#!/usr/bin/env python3
"""
Detailed ECG Interpretation Guide - PDF Generator
Uses ReportLab to produce a professional, well-formatted reference guide.
"""

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.units import mm, cm
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_LEFT, TA_CENTER, TA_JUSTIFY
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, PageBreak, KeepTogether
)
from reportlab.pdfgen import canvas
from reportlab.platypus.flowables import Flowable
import math

OUTPUT_PATH = "/home/daytona/workspace/ecg-guide/ECG_Interpretation_Guide.pdf"

# ─── Color Palette ────────────────────────────────────────────────────────────
C_RED       = colors.HexColor("#C0392B")
C_DARK_RED  = colors.HexColor("#922B21")
C_BLUE      = colors.HexColor("#1A5276")
C_TEAL      = colors.HexColor("#117A65")
C_ORANGE    = colors.HexColor("#D35400")
C_PURPLE    = colors.HexColor("#6C3483")
C_GREEN     = colors.HexColor("#1E8449")
C_LIGHT_BG  = colors.HexColor("#F4F6F7")
C_HEADER_BG = colors.HexColor("#1A5276")
C_WARN_BG   = colors.HexColor("#FDEBD0")
C_WARN_BORDER = colors.HexColor("#D35400")
C_CRIT_BG   = colors.HexColor("#FADBD8")
C_CRIT_BORDER = colors.HexColor("#C0392B")
C_NOTE_BG   = colors.HexColor("#EBF5FB")
C_NOTE_BORDER = colors.HexColor("#1A5276")
C_GREEN_BG  = colors.HexColor("#EAFAF1")
C_GREEN_BORDER = colors.HexColor("#1E8449")
C_GRID      = colors.HexColor("#E8E8E8")
C_BLACK     = colors.black
C_WHITE     = colors.white
C_GRAY      = colors.HexColor("#7F8C8D")
C_DARK      = colors.HexColor("#2C3E50")

# ─── ECG Waveform Drawable ─────────────────────────────────────────────────────
class ECGWaveform(Flowable):
    """Draws a simplified ECG PQRST waveform diagram."""
    def __init__(self, width=160*mm, height=40*mm):
        Flowable.__init__(self)
        self.width = width
        self.height = height

    def draw(self):
        c = self.canv
        w, h = self.width, self.height
        baseline = h * 0.45
        x0 = w * 0.03

        # Grid lines
        c.setStrokeColor(colors.HexColor("#FFCCCC"))
        c.setLineWidth(0.3)
        for i in range(0, int(w), int(5*mm)):
            c.line(x0 + i, 0, x0 + i, h)
        for i in range(0, int(h), int(5*mm)):
            c.line(x0, i, w, i)

        # Major grid
        c.setStrokeColor(colors.HexColor("#FF9999"))
        c.setLineWidth(0.5)
        for i in range(0, int(w), int(25*mm)):
            c.line(x0 + i, 0, x0 + i, h)
        for i in range(0, int(h), int(10*mm)):
            c.line(x0, i, w, i)

        # ECG trace
        c.setStrokeColor(C_DARK)
        c.setLineWidth(1.5)
        p = c.beginPath()

        scale = h * 0.38
        unit = w * 0.055  # one small square width

        # Isoelectric lead-in
        pts = [(0, 0)]
        # P wave (small bump)
        for i, t in enumerate([i/20 for i in range(21)]):
            x = unit*2 + t * unit*2
            y = 0.25 * scale * math.sin(math.pi * t)
            pts.append((x, y))
        # PR segment
        pts.append((unit*4.5, 0))
        pts.append((unit*5.5, 0))
        # Q wave (small dip)
        pts.append((unit*5.8, -0.15*scale))
        # R wave (tall peak)
        pts.append((unit*6.2, 1.0*scale))
        # S wave (small dip)
        pts.append((unit*6.6, -0.2*scale))
        # J point
        pts.append((unit*7.0, 0.05*scale))
        # ST segment
        pts.append((unit*8.5, 0.05*scale))
        # T wave (rounded bump)
        for i, t in enumerate([i/20 for i in range(21)]):
            x = unit*8.5 + t * unit*3
            y = 0.45 * scale * math.sin(math.pi * t)
            pts.append((x, y))
        # Return to baseline
        pts.append((unit*12.5, 0))
        pts.append((unit*14.0, 0))
        # Second beat (compressed)
        pts.append((unit*14.5, 0.12*scale))
        pts.append((unit*15.5, 0.12*scale))
        pts.append((unit*15.7, -0.15*scale))
        pts.append((unit*16.0, 1.0*scale))
        pts.append((unit*16.3, -0.2*scale))
        pts.append((unit*16.6, 0.05*scale))
        pts.append((unit*17.5, 0.05*scale))
        for i, t in enumerate([i/20 for i in range(21)]):
            x = unit*17.5 + t * unit*2.5
            y = 0.42 * scale * math.sin(math.pi * t)
            pts.append((x, y))
        pts.append((unit*20.5, 0))

        p.moveTo(x0, baseline + pts[0][1])
        for x, y in pts[1:]:
            p.lineTo(x0 + x, baseline + y)
        c.drawPath(p, stroke=1, fill=0)

        # Labels
        c.setFillColor(C_RED)
        c.setFont("Helvetica-Bold", 7)
        # P label
        c.drawCentredString(x0 + unit*3.5, baseline + 0.35*scale, "P")
        # Q label
        c.drawCentredString(x0 + unit*5.8, baseline - 0.32*scale, "Q")
        # R label
        c.drawCentredString(x0 + unit*6.2, baseline + 1.15*scale, "R")
        # S label
        c.drawCentredString(x0 + unit*6.7, baseline - 0.38*scale, "S")
        # T label
        c.drawCentredString(x0 + unit*10.0, baseline + 0.6*scale, "T")

        # Interval arrows & labels
        c.setStrokeColor(C_BLUE)
        c.setFillColor(C_BLUE)
        c.setLineWidth(0.8)
        arrow_y = baseline - 0.55*scale

        def draw_arrow(x1, x2, y, label, color=C_BLUE):
            c.setStrokeColor(color)
            c.setFillColor(color)
            c.setFont("Helvetica", 6.5)
            c.line(x1, y, x2, y)
            c.line(x1, y-2, x1, y+2)
            c.line(x2, y-2, x2, y+2)
            c.drawCentredString((x1+x2)/2, y - 7, label)

        # PR interval
        draw_arrow(x0 + unit*2.0, x0 + unit*5.8, arrow_y - 3, "PR interval", C_BLUE)
        # QRS duration
        draw_arrow(x0 + unit*5.8, x0 + unit*7.0, arrow_y - 12, "QRS", C_RED)
        # QT interval
        draw_arrow(x0 + unit*5.8, x0 + unit*11.5, arrow_y - 21, "QT interval", C_TEAL)
        # RR interval
        draw_arrow(x0 + unit*6.2, x0 + unit*16.0, arrow_y - 30, "RR interval", C_PURPLE)


# ─── Page Template ─────────────────────────────────────────────────────────────
def make_header_footer(canvas_obj, doc):
    canvas_obj.saveState()
    W, H = A4
    # Header bar
    canvas_obj.setFillColor(C_HEADER_BG)
    canvas_obj.rect(0, H - 18*mm, W, 18*mm, fill=1, stroke=0)
    canvas_obj.setFillColor(C_WHITE)
    canvas_obj.setFont("Helvetica-Bold", 11)
    canvas_obj.drawString(15*mm, H - 12*mm, "ECG Interpretation Reference Guide")
    canvas_obj.setFont("Helvetica", 9)
    canvas_obj.drawRightString(W - 15*mm, H - 12*mm, "Clinical Reference | 2026")

    # Footer
    canvas_obj.setFillColor(C_HEADER_BG)
    canvas_obj.rect(0, 0, W, 12*mm, fill=1, stroke=0)
    canvas_obj.setFillColor(C_WHITE)
    canvas_obj.setFont("Helvetica", 8)
    canvas_obj.drawString(15*mm, 4*mm,
        "For educational/clinical reference use. Always correlate with patient history & clinical findings.")
    canvas_obj.drawRightString(W - 15*mm, 4*mm, f"Page {doc.page}")
    canvas_obj.restoreState()


# ─── Styles ────────────────────────────────────────────────────────────────────
def get_styles():
    base = getSampleStyleSheet()
    s = {}

    s['cover_title'] = ParagraphStyle('cover_title',
        fontSize=34, fontName='Helvetica-Bold',
        textColor=C_WHITE, alignment=TA_CENTER,
        spaceAfter=6*mm, leading=40)

    s['cover_sub'] = ParagraphStyle('cover_sub',
        fontSize=15, fontName='Helvetica',
        textColor=colors.HexColor("#AED6F1"), alignment=TA_CENTER,
        spaceAfter=4*mm, leading=20)

    s['cover_tag'] = ParagraphStyle('cover_tag',
        fontSize=11, fontName='Helvetica-Oblique',
        textColor=colors.HexColor("#D5DBDB"), alignment=TA_CENTER,
        spaceAfter=2*mm)

    s['chapter'] = ParagraphStyle('chapter',
        fontSize=16, fontName='Helvetica-Bold',
        textColor=C_WHITE, alignment=TA_LEFT,
        spaceBefore=0, spaceAfter=0, leading=20,
        leftIndent=0, borderPad=0)

    s['section'] = ParagraphStyle('section',
        fontSize=12, fontName='Helvetica-Bold',
        textColor=C_HEADER_BG, spaceBefore=5*mm,
        spaceAfter=2*mm, leading=16)

    s['subsection'] = ParagraphStyle('subsection',
        fontSize=10.5, fontName='Helvetica-Bold',
        textColor=C_DARK, spaceBefore=3*mm,
        spaceAfter=1.5*mm, leading=14)

    s['body'] = ParagraphStyle('body',
        fontSize=9.5, fontName='Helvetica',
        textColor=C_DARK, spaceBefore=1*mm,
        spaceAfter=1*mm, leading=14, alignment=TA_JUSTIFY)

    s['bullet'] = ParagraphStyle('bullet',
        fontSize=9.5, fontName='Helvetica',
        textColor=C_DARK, spaceBefore=0.5*mm,
        spaceAfter=0.5*mm, leading=13,
        leftIndent=12, bulletIndent=2)

    s['sub_bullet'] = ParagraphStyle('sub_bullet',
        fontSize=9, fontName='Helvetica',
        textColor=C_DARK, spaceBefore=0.2*mm,
        spaceAfter=0.2*mm, leading=12,
        leftIndent=22, bulletIndent=14)

    s['note'] = ParagraphStyle('note',
        fontSize=9, fontName='Helvetica-Oblique',
        textColor=C_BLUE, spaceBefore=1*mm,
        spaceAfter=1*mm, leading=13)

    s['table_header'] = ParagraphStyle('table_header',
        fontSize=8.5, fontName='Helvetica-Bold',
        textColor=C_WHITE, alignment=TA_CENTER, leading=12)

    s['table_cell'] = ParagraphStyle('table_cell',
        fontSize=8.5, fontName='Helvetica',
        textColor=C_DARK, alignment=TA_LEFT, leading=12)

    s['table_cell_center'] = ParagraphStyle('table_cell_center',
        fontSize=8.5, fontName='Helvetica',
        textColor=C_DARK, alignment=TA_CENTER, leading=12)

    s['warn_text'] = ParagraphStyle('warn_text',
        fontSize=9, fontName='Helvetica',
        textColor=colors.HexColor("#784212"),
        leading=13, spaceBefore=1*mm, spaceAfter=1*mm)

    s['crit_text'] = ParagraphStyle('crit_text',
        fontSize=9, fontName='Helvetica',
        textColor=C_DARK_RED,
        leading=13, spaceBefore=1*mm, spaceAfter=1*mm)

    s['note_text'] = ParagraphStyle('note_text',
        fontSize=9, fontName='Helvetica',
        textColor=C_BLUE,
        leading=13, spaceBefore=1*mm, spaceAfter=1*mm)

    s['green_text'] = ParagraphStyle('green_text',
        fontSize=9, fontName='Helvetica',
        textColor=C_GREEN,
        leading=13, spaceBefore=1*mm, spaceAfter=1*mm)

    return s


# ─── Box Helpers ───────────────────────────────────────────────────────────────
def warning_box(text, styles, label="WARNING"):
    data = [[Paragraph(f'<b>{label}:</b> {text}', styles['warn_text'])]]
    t = Table(data, colWidths=[170*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), C_WARN_BG),
        ('BOX', (0,0), (-1,-1), 1.5, C_WARN_BORDER),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('RIGHTPADDING', (0,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 5),
        ('BOTTOMPADDING', (0,0), (-1,-1), 5),
        ('ROUNDEDCORNERS', [4, 4, 4, 4]),
    ]))
    return t

def critical_box(text, styles, label="CRITICAL"):
    data = [[Paragraph(f'<b>{label}:</b> {text}', styles['crit_text'])]]
    t = Table(data, colWidths=[170*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), C_CRIT_BG),
        ('BOX', (0,0), (-1,-1), 1.5, C_CRIT_BORDER),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('RIGHTPADDING', (0,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 5),
        ('BOTTOMPADDING', (0,0), (-1,-1), 5),
    ]))
    return t

def note_box(text, styles, label="NOTE"):
    data = [[Paragraph(f'<b>{label}:</b> {text}', styles['note_text'])]]
    t = Table(data, colWidths=[170*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), C_NOTE_BG),
        ('BOX', (0,0), (-1,-1), 1.5, C_NOTE_BORDER),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('RIGHTPADDING', (0,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 5),
        ('BOTTOMPADDING', (0,0), (-1,-1), 5),
    ]))
    return t

def green_box(text, styles, label="NORMAL"):
    data = [[Paragraph(f'<b>{label}:</b> {text}', styles['green_text'])]]
    t = Table(data, colWidths=[170*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), C_GREEN_BG),
        ('BOX', (0,0), (-1,-1), 1.5, C_GREEN_BORDER),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('RIGHTPADDING', (0,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 5),
        ('BOTTOMPADDING', (0,0), (-1,-1), 5),
    ]))
    return t

def chapter_header(title, subtitle, styles, color=C_HEADER_BG):
    data = [[
        Paragraph(title, styles['chapter']),
        Paragraph(subtitle, ParagraphStyle('ch_sub', fontSize=9,
            fontName='Helvetica-Oblique', textColor=colors.HexColor("#AED6F1"),
            alignment=TA_LEFT, leading=12))
    ]]
    t = Table(data, colWidths=[120*mm, 50*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), color),
        ('LEFTPADDING', (0,0), (0,-1), 8),
        ('RIGHTPADDING', (-1,0), (-1,-1), 8),
        ('TOPPADDING', (0,0), (-1,-1), 7),
        ('BOTTOMPADDING', (0,0), (-1,-1), 7),
        ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
    ]))
    return t

def make_table(headers, rows, styles, col_widths=None):
    header_row = [Paragraph(h, styles['table_header']) for h in headers]
    body_rows = []
    for row in rows:
        body_rows.append([Paragraph(str(cell), styles['table_cell']) for cell in row])
    data = [header_row] + body_rows
    if col_widths is None:
        col_widths = [170*mm / len(headers)] * len(headers)
    t = Table(data, colWidths=col_widths, repeatRows=1)
    ts = [
        ('BACKGROUND', (0,0), (-1,0), C_HEADER_BG),
        ('TEXTCOLOR', (0,0), (-1,0), C_WHITE),
        ('FONTNAME', (0,0), (-1,0), 'Helvetica-Bold'),
        ('FONTSIZE', (0,0), (-1,0), 8.5),
        ('ALIGN', (0,0), (-1,0), 'CENTER'),
        ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ('ROWBACKGROUNDS', (0,1), (-1,-1), [C_WHITE, C_LIGHT_BG]),
        ('GRID', (0,0), (-1,-1), 0.5, C_GRID),
        ('LEFTPADDING', (0,0), (-1,-1), 5),
        ('RIGHTPADDING', (0,0), (-1,-1), 5),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
    ]
    t.setStyle(TableStyle(ts))
    return t


# ─── Cover Page ────────────────────────────────────────────────────────────────
def build_cover(styles):
    elements = []
    W, H = A4

    # Blue gradient cover background via table
    cover_data = [['']]
    cover_table = Table(cover_data, colWidths=[W - 30*mm], rowHeights=[H - 30*mm])
    cover_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), C_HEADER_BG),
        ('BOX', (0,0), (-1,-1), 2, C_BLUE),
    ]))

    inner = []
    inner.append(Spacer(1, 35*mm))

    # ECG line decoration
    ecg_line = "_" * 60
    inner.append(Paragraph(
        '<font color="#AED6F1" size="8">— — — — — — — — — — — — — — — — — — — — — — — — — — — — — —</font>',
        ParagraphStyle('ecg_line', alignment=TA_CENTER, spaceBefore=0, spaceAfter=5*mm)))

    inner.append(Paragraph("ECG Interpretation", styles['cover_title']))
    inner.append(Paragraph("Reference Guide", ParagraphStyle('ct2',
        fontSize=28, fontName='Helvetica',
        textColor=colors.HexColor("#AED6F1"), alignment=TA_CENTER,
        spaceAfter=8*mm, leading=34)))

    inner.append(Paragraph(
        '<font color="#AED6F1" size="8">— — — — — — — — — — — — — — — — — — — — — — — — — — — — — —</font>',
        ParagraphStyle('ecg_line2', alignment=TA_CENTER, spaceBefore=0, spaceAfter=8*mm)))

    inner.append(Spacer(1, 5*mm))
    inner.append(Paragraph(
        "A Complete Systematic Approach to 12-Lead ECG Analysis",
        styles['cover_sub']))
    inner.append(Spacer(1, 5*mm))

    # Chapter badges
    badge_items = [
        "Rate & Rhythm", "Axis Determination", "P Wave Analysis",
        "PR / QRS / QT Intervals", "ST Segments & Ischemia",
        "Bundle Branch Blocks", "Arrhythmias", "Hypertrophy Criteria",
        "STEMI Localization", "Differential Diagnosis"
    ]
    badge_text = "  |  ".join(badge_items)
    inner.append(Paragraph(
        f'<font color="#85C1E9" size="8">{badge_text}</font>',
        ParagraphStyle('badges', alignment=TA_CENTER, spaceAfter=10*mm, leading=14)))

    inner.append(Spacer(1, 10*mm))
    inner.append(Paragraph(
        "Based on Braunwald's Heart Disease, Fuster & Hurst's The Heart,<br/>"
        "Roberts & Hedges' Clinical Procedures in Emergency Medicine",
        ParagraphStyle('sources', fontSize=9, fontName='Helvetica-Oblique',
            textColor=colors.HexColor("#85C1E9"), alignment=TA_CENTER,
            leading=14, spaceAfter=3*mm)))

    inner.append(Spacer(1, 5*mm))
    inner.append(Paragraph(
        "Clinical Reference Edition · 2026",
        ParagraphStyle('edition', fontSize=10, fontName='Helvetica-Bold',
            textColor=colors.HexColor("#D5DBDB"), alignment=TA_CENTER,
            spaceAfter=2*mm)))

    for item in inner:
        elements.append(item)

    elements.append(PageBreak())
    return elements


# ─── Table of Contents ─────────────────────────────────────────────────────────
def build_toc(styles):
    elements = []
    elements.append(Spacer(1, 5*mm))
    elements.append(Paragraph("Table of Contents", ParagraphStyle('toc_title',
        fontSize=18, fontName='Helvetica-Bold', textColor=C_HEADER_BG,
        spaceAfter=5*mm, leading=22)))
    elements.append(HRFlowable(width="100%", thickness=2, color=C_HEADER_BG))
    elements.append(Spacer(1, 3*mm))

    toc_items = [
        ("1", "ECG Basics - Paper, Speed, and Calibration", "3"),
        ("2", "The Normal PQRST Waveform & Intervals", "4"),
        ("3", "Step-by-Step Systematic Approach (10 Steps)", "5"),
        ("4", "Heart Rate Calculation Methods", "6"),
        ("5", "Cardiac Axis Determination", "7"),
        ("6", "P Wave Analysis - Normal & Abnormal", "8"),
        ("7", "PR Interval & AV Block Classification", "9"),
        ("8", "QRS Complex - Width, Morphology & Voltage", "10"),
        ("9", "Bundle Branch Blocks (RBBB & LBBB)", "11"),
        ("10", "ST Segment Analysis & Ischemia", "12"),
        ("11", "T Wave Abnormalities", "13"),
        ("12", "QT Interval & Long QT Syndrome", "14"),
        ("13", "STEMI Recognition & Territory Localization", "15"),
        ("14", "Arrhythmia Recognition", "16"),
        ("15", "Ventricular Hypertrophy Criteria", "17"),
        ("16", "Quick Reference Cards & Differentials", "18"),
    ]

    for num, title, page in toc_items:
        row_data = [[
            Paragraph(f'<b>{num}.</b>', ParagraphStyle('tc_num', fontSize=10,
                fontName='Helvetica-Bold', textColor=C_HEADER_BG, alignment=TA_CENTER)),
            Paragraph(title, ParagraphStyle('tc_title', fontSize=10,
                fontName='Helvetica', textColor=C_DARK, leading=14)),
            Paragraph(page, ParagraphStyle('tc_page', fontSize=10,
                fontName='Helvetica-Bold', textColor=C_GRAY, alignment=TA_CENTER)),
        ]]
        t = Table(row_data, colWidths=[12*mm, 148*mm, 10*mm])
        t.setStyle(TableStyle([
            ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
            ('TOPPADDING', (0,0), (-1,-1), 3),
            ('BOTTOMPADDING', (0,0), (-1,-1), 3),
            ('LINEBELOW', (0,0), (-1,0), 0.3, C_GRID),
        ]))
        elements.append(t)

    elements.append(PageBreak())
    return elements


# ─── Chapter 1: ECG Basics ─────────────────────────────────────────────────────
def chapter1(styles):
    el = []
    el.append(chapter_header("Chapter 1", "ECG Basics - Paper, Speed & Calibration", styles))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("What is an ECG?", styles['section']))
    el.append(Paragraph(
        "An electrocardiogram (ECG/EKG) is a graphical recording of the electrical activity of the heart over time. "
        "Electrodes placed on the skin detect voltage differences between body surface points, producing a "
        "waveform that reflects depolarization and repolarization of the myocardium. The standard 12-lead ECG "
        "is the most important non-invasive cardiac diagnostic tool available.", styles['body']))

    el.append(Paragraph("Standard ECG Paper Settings", styles['section']))
    el.append(Paragraph(
        "All ECG measurements depend on correct calibration. Always verify settings before interpretation.", styles['body']))

    data = [
        ["Parameter", "Standard Value", "Clinical Meaning"],
        ["Paper speed", "25 mm/second", "1 small box = 0.04 s; 1 large box = 0.20 s"],
        ["Voltage calibration", "10 mm/mV", "1 small box = 0.1 mV; 1 large box = 0.5 mV"],
        ["Small box (1 mm)", "0.04 s (40 ms) wide", "Duration of tiny intervals"],
        ["Large box (5 mm)", "0.20 s (200 ms) wide", "Duration of intervals (e.g. PR ~1 large box)"],
        ["1 mm height", "0.1 mV", "Amplitude reference for voltage criteria"],
        ["Calibration pulse", "10 mm tall square wave", "Confirms 10 mm/mV calibration"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 50*mm, 75*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(note_box(
        "If paper speed is 50 mm/s (common in some countries), all time measurements are halved. "
        "A large box = 0.10 s at 50 mm/s. Always confirm the speed printed on the ECG.",
        styles, label="NOTE"))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("The 12 Leads Explained", styles['section']))
    el.append(Paragraph(
        "The 12-lead ECG captures cardiac electrical activity from 12 different angles, "
        "grouped into two planes:", styles['body']))

    el.append(Paragraph("Limb Leads (Frontal Plane):", styles['subsection']))
    data2 = [
        ["Lead", "View", "Normal QRS Deflection", "Territory"],
        ["I", "Lateral (0°)", "Positive", "Lateral wall"],
        ["II", "Inferior (+60°)", "Positive (tallest)", "Inferior wall / rhythm strip"],
        ["III", "Inferior (+120°)", "Variable", "Inferior wall"],
        ["aVR", "Right arm (-150°)", "Negative (inverted)", "Cavity / right sided"],
        ["aVL", "Left arm (-30°)", "Variable/biphasic", "High lateral wall"],
        ["aVF", "Foot (+90°)", "Positive", "Inferior wall"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[15*mm, 45*mm, 55*mm, 55*mm]))
    el.append(Spacer(1, 2*mm))

    el.append(Paragraph("Precordial Leads (Horizontal Plane):", styles['subsection']))
    data3 = [
        ["Lead", "Position", "Normal Morphology", "Territory"],
        ["V1", "4th ICS, right sternal border", "rS pattern (small r, deep S)", "RV, septal"],
        ["V2", "4th ICS, left sternal border", "rS pattern", "Septal"],
        ["V3", "Between V2 and V4", "Transitional", "Anterior septal"],
        ["V4", "5th ICS, midclavicular line", "RS (r=s, transition zone)", "Anterior"],
        ["V5", "5th ICS, anterior axillary", "qR pattern (dominant R)", "Lateral"],
        ["V6", "5th ICS, midaxillary line", "qR pattern", "Lateral"],
    ]
    el.append(make_table(data3[0], data3[1:], styles, col_widths=[15*mm, 55*mm, 50*mm, 50*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(note_box(
        "R wave progression: The R wave should gradually increase in amplitude from V1 to V5/V6 "
        "(R wave 'grows'). Poor R-wave progression (PRWP) in V1-V4 may indicate anterior infarction or LBBB.",
        styles))

    el.append(PageBreak())
    return el


# ─── Chapter 2: PQRST Waveform ─────────────────────────────────────────────────
def chapter2(styles):
    el = []
    el.append(chapter_header("Chapter 2", "The Normal PQRST Waveform & Intervals", styles))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("PQRST Waveform Diagram", styles['section']))
    el.append(ECGWaveform(width=170*mm, height=45*mm))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Waveform Components - Normal Values", styles['section']))
    data = [
        ["Component", "What It Represents", "Normal Duration", "Normal Amplitude"],
        ["P wave", "Atrial depolarization (SA node to AV node)", "< 120 ms (3 small boxes)", "< 2.5 mm in II; < 1.5 mm in V1"],
        ["PR interval", "Time from atrial to ventricular activation (AV node delay)", "120-200 ms (3-5 large boxes)", "Not measured"],
        ["PR segment", "AV node conduction time", "Isoelectric", "At baseline"],
        ["QRS complex", "Ventricular depolarization", "< 120 ms (< 3 small boxes)", "Varies by lead"],
        ["Q wave", "Initial septal depolarization", "< 40 ms; < 25% of R height", "< 25% of R wave"],
        ["R wave", "Ventricular depolarization (main upstroke)", "N/A", "See LVH criteria"],
        ["S wave", "Terminal ventricular depolarization", "N/A", "N/A"],
        ["ST segment", "Ventricular plateau (between depol. & repol.)", "Isoelectric", "< 1 mm deviation (< 2 mm V1-V4)"],
        ["T wave", "Ventricular repolarization", "100-250 ms", "< 5 mm limb; < 10 mm precordial"],
        ["QT interval", "Total ventricular electromechanical activity", "See QTc formula", "Rate-corrected"],
        ["U wave", "Purkinje/M-cell repolarization (or hypokalemia)", "< T wave amplitude", "Small, same direction as T"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[25*mm, 60*mm, 45*mm, 40*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Key Interval Formulas", styles['section']))
    formulas = [
        ("QTc (Bazett formula)", "QTc = QT / √RR", "Most widely used. Normal: ≤ 440 ms (men), ≤ 460 ms (women)."),
        ("QTc (Fridericia formula)", "QTc = QT / (RR)^(1/3)", "More accurate at fast/slow rates. Same normal cutoffs."),
        ("Heart Rate from RR", "HR = 1500 / (RR in small boxes)", "At 25 mm/s: count small boxes between R peaks."),
        ("Heart Rate (large boxes)", "HR = 300 / (# large boxes between R-R)", "Quick estimation method."),
    ]
    for name, formula, note in formulas:
        row = [[
            Paragraph(f'<b>{name}</b>', styles['subsection']),
            Paragraph(f'<b><font color="#C0392B">{formula}</font></b>',
                ParagraphStyle('formula', fontSize=11, fontName='Helvetica-Bold',
                    textColor=C_RED, leading=14, alignment=TA_CENTER)),
            Paragraph(note, styles['body'])
        ]]
        t = Table(row, colWidths=[52*mm, 50*mm, 68*mm])
        t.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (-1,-1), C_LIGHT_BG),
            ('GRID', (0,0), (-1,-1), 0.5, C_GRID),
            ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
            ('TOPPADDING', (0,0), (-1,-1), 5),
            ('BOTTOMPADDING', (0,0), (-1,-1), 5),
            ('LEFTPADDING', (0,0), (-1,-1), 5),
        ]))
        el.append(t)
        el.append(Spacer(1, 1*mm))

    el.append(PageBreak())
    return el


# ─── Chapter 3: 10-Step Systematic Approach ───────────────────────────────────
def chapter3(styles):
    el = []
    el.append(chapter_header("Chapter 3", "10-Step Systematic Approach to ECG Interpretation", styles))
    el.append(Spacer(1, 4*mm))
    el.append(Paragraph(
        "Always follow this systematic sequence. Skipping steps causes missed diagnoses. "
        "Interpret the ECG BEFORE looking at the computer reading.", styles['body']))
    el.append(Spacer(1, 3*mm))

    steps = [
        ("1", "CONFIRM TECHNICAL DETAILS", C_BLUE,
         "Patient name, age, date/time. Paper speed (25 or 50 mm/s). Calibration (10 mm/mV). "
         "Lead placement correct (V1 right sternal border, not reversed). Check for lead artifact."),
        ("2", "HEART RATE", C_TEAL,
         "Method 1 (regular): 300 / # large boxes between R waves. "
         "Method 2: Count R waves in 6-second strip x 10. "
         "Normal: 60-100 bpm. Bradycardia: <60 bpm. Tachycardia: >100 bpm."),
        ("3", "RHYTHM", C_GREEN,
         "Is it regular or irregular? Are all RR intervals equal? "
         "Is there a P wave before every QRS? Is the QRS narrow or wide? "
         "Does the PR interval vary?"),
        ("4", "P WAVES", C_PURPLE,
         "Present? Upright in I and II (confirms sinus rhythm)? "
         "One P before each QRS? Normal shape (not peaked or bifid)? "
         "PR constant? P axis 0-75 degrees?"),
        ("5", "PR INTERVAL", C_ORANGE,
         "Normal: 120-200 ms. Short (<120ms): pre-excitation (WPW), junctional rhythm. "
         "Long (>200ms): 1st degree AV block. Variable: 2nd or 3rd degree block."),
        ("6", "QRS COMPLEX", C_RED,
         "Duration (normal <120ms). Morphology. Axis. "
         "Q waves (pathologic if >40ms or >25% R height). "
         "R wave progression V1→V6. Low voltage (<5mm limb, <10mm precordial)."),
        ("7", "ST SEGMENT", C_DARK_RED,
         "Measured at J point, 60-80ms after J point. "
         "Elevation (>1mm limb leads, >2mm V1-V4): STEMI until proven otherwise. "
         "Depression (>1mm): ischemia, NSTEMI, digoxin effect, LVH strain."),
        ("8", "T WAVES", C_BLUE,
         "Should be upright in I, II, V3-V6 and inverted in aVR. "
         "Peaked (hyperkalemia, hyperacute MI). Inverted (ischemia, strain, PE, CNS event). "
         "Biphasic (Wellens pattern - critical LAD stenosis)."),
        ("9", "QT INTERVAL", C_TEAL,
         "Measure in V5 or II. Calculate QTc using Bazett: QTc = QT / √RR. "
         "Prolonged QTc: >440ms men, >460ms women - risk of Torsades de Pointes. "
         "Short QTc: <350ms - hypercalcemia, short QT syndrome."),
        ("10", "OVERALL INTERPRETATION", C_GREEN,
         "Synthesize all findings. Provide: Rhythm, Rate, Axis, Intervals, "
         "ST-T changes, and any specific diagnoses. Correlate with clinical context."),
    ]

    for num, title, color, desc in steps:
        row = [[
            Paragraph(num, ParagraphStyle('step_num', fontSize=18,
                fontName='Helvetica-Bold', textColor=C_WHITE,
                alignment=TA_CENTER, leading=22)),
            [
                Paragraph(title, ParagraphStyle('step_title', fontSize=10,
                    fontName='Helvetica-Bold', textColor=color, leading=14,
                    spaceAfter=2)),
                Paragraph(desc, styles['body'])
            ]
        ]]
        t = Table(row, colWidths=[14*mm, 156*mm])
        t.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (0,0), color),
            ('BACKGROUND', (1,0), (1,0), C_WHITE),
            ('BOX', (0,0), (-1,-1), 1, color),
            ('VALIGN', (0,0), (-1,-1), 'TOP'),
            ('TOPPADDING', (0,0), (-1,-1), 5),
            ('BOTTOMPADDING', (0,0), (-1,-1), 5),
            ('LEFTPADDING', (1,0), (1,0), 8),
        ]))
        el.append(t)
        el.append(Spacer(1, 1.5*mm))

    el.append(PageBreak())
    return el


# ─── Chapter 4: Rate Calculation ──────────────────────────────────────────────
def chapter4(styles):
    el = []
    el.append(chapter_header("Chapter 4", "Heart Rate Calculation Methods", styles))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Method 1: The 300 Rule (Regular Rhythms)", styles['section']))
    el.append(Paragraph(
        "Count the number of large boxes (5 mm each) between two consecutive R waves. "
        "Divide 300 by this number:", styles['body']))

    data = [
        ["# Large Boxes", "Heart Rate (bpm)", "Classification"],
        ["1", "300", "Critical tachycardia (likely VF/VT)"],
        ["2", "150", "Tachycardia (consider atrial flutter 2:1)"],
        ["3", "100", "Upper limit of normal"],
        ["4", "75", "Normal"],
        ["5", "60", "Lower limit of normal"],
        ["6", "50", "Bradycardia"],
        ["7", "43", "Bradycardia"],
        ["8-10", "30-38", "Severe bradycardia"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[40*mm, 55*mm, 75*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Method 2: 6-Second Strip Count (Irregular Rhythms)", styles['section']))
    el.append(Paragraph(
        "Count the number of QRS complexes in a 6-second strip (= 30 large boxes at 25mm/s). "
        "Multiply by 10 to get rate per minute. Use this for atrial fibrillation or other irregular rhythms.", styles['body']))

    el.append(Spacer(1, 2*mm))
    el.append(Paragraph("Method 3: 1500 Rule (Precise - Regular Rhythms)", styles['section']))
    el.append(Paragraph(
        "Count the number of small boxes (1 mm each) between two consecutive R waves. "
        "Divide 1500 by this number. Most precise at 25 mm/s.", styles['body']))

    el.append(Spacer(1, 3*mm))
    el.append(Paragraph("Rate Classification Table", styles['section']))
    data2 = [
        ["Rate Category", "Beats Per Minute", "Common Causes"],
        ["Severe bradycardia", "< 40 bpm", "Complete heart block, hypothermia, hypothyroidism"],
        ["Bradycardia", "40-60 bpm", "High vagal tone, athletic heart, inferior MI, beta-blockers"],
        ["Normal", "60-100 bpm", "Sinus rhythm at rest"],
        ["Tachycardia", "100-150 bpm", "Sinus tach, atrial tach, SVT, AFL with block"],
        ["Rapid tachycardia", "150-250 bpm", "SVT, AFL 2:1, AF with rapid ventricular response"],
        ["Extreme tachycardia", "> 250 bpm", "VF, pre-excited AF (WPW), polymorphic VT"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[50*mm, 40*mm, 80*mm]))

    el.append(Spacer(1, 3*mm))
    el.append(warning_box(
        "A ventricular rate of exactly 150 bpm should always raise suspicion for atrial flutter "
        "with 2:1 AV conduction - look carefully for flutter waves (F waves) in V1 and lead II.",
        styles))

    el.append(PageBreak())
    return el


# ─── Chapter 5: Axis ──────────────────────────────────────────────────────────
def chapter5(styles):
    el = []
    el.append(chapter_header("Chapter 5", "Cardiac Axis Determination", styles))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph(
        "The cardiac axis represents the mean direction of ventricular depolarization in the frontal plane. "
        "Quick axis determination uses leads I and aVF:", styles['body']))

    data = [
        ["Lead I", "Lead aVF", "Axis Range", "Interpretation"],
        ["Positive (upright)", "Positive (upright)", "0° to +90°", "NORMAL AXIS"],
        ["Positive (upright)", "Negative (down)", "-90° to 0°", "LEFT AXIS DEVIATION (LAD)"],
        ["Negative (down)", "Positive (upright)", "+90° to +180°", "RIGHT AXIS DEVIATION (RAD)"],
        ["Negative (down)", "Negative (down)", "-90° to ±180°", "EXTREME AXIS (NW axis - 'no man's land')"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[40*mm, 40*mm, 45*mm, 45*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Normal Axis Ranges by Age", styles['subsection']))
    data2 = [
        ["Age Group", "Normal Axis Range"],
        ["Newborn / Infant", "+30° to +180° (right-dominant at birth)"],
        ["Child (1-8 years)", "+10° to +100°"],
        ["Adult", "0° to +90° (-30° to +90° acceptable)"],
        ["Left axis deviation (adult)", "More negative than -30°"],
        ["Right axis deviation (adult)", "Greater than +90°"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[60*mm, 110*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Causes of Axis Deviation", styles['section']))
    causes_data = [
        ["LEFT Axis Deviation", "RIGHT Axis Deviation"],
        ["Left anterior fascicular block (most common cause)",
         "Right ventricular hypertrophy"],
        ["Left ventricular hypertrophy",
         "Left posterior fascicular block"],
        ["Inferior MI (loss of inferior forces)",
         "Lateral wall MI (loss of lateral forces)"],
        ["Left bundle branch block",
         "Right bundle branch block (mild RAD)"],
        ["Wolff-Parkinson-White (right-sided pathway)",
         "Wolff-Parkinson-White (left-sided pathway)"],
        ["Hyperkalemia (marked)",
         "Pulmonary embolism / cor pulmonale"],
        ["Pacemaker (RV-paced)",
         "Normal in children, tall/thin adults, COPD"],
    ]
    t = Table(causes_data, colWidths=[85*mm, 85*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (0,0), C_TEAL),
        ('BACKGROUND', (1,0), (1,0), C_RED),
        ('TEXTCOLOR', (0,0), (-1,0), C_WHITE),
        ('FONTNAME', (0,0), (-1,0), 'Helvetica-Bold'),
        ('FONTSIZE', (0,0), (-1,-1), 9),
        ('ROWBACKGROUNDS', (0,1), (-1,-1), [C_WHITE, C_LIGHT_BG]),
        ('GRID', (0,0), (-1,-1), 0.5, C_GRID),
        ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ('LEFTPADDING', (0,0), (-1,-1), 6),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
    ]))
    el.append(t)

    el.append(PageBreak())
    return el


# ─── Chapter 6: P Wave ────────────────────────────────────────────────────────
def chapter6(styles):
    el = []
    el.append(chapter_header("Chapter 6", "P Wave Analysis", styles, C_TEAL))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Normal P Wave Criteria", styles['section']))
    el.append(green_box(
        "Upright in leads I, II, aVF, V4-V6. Inverted in aVR. Duration < 120ms (3 small boxes). "
        "Amplitude < 2.5mm in lead II. Biphasic in V1 (small positive then small negative component).",
        styles, label="NORMAL"))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("P Wave Abnormalities", styles['section']))
    data = [
        ["Abnormality", "ECG Features", "Causes"],
        ["P pulmonale\n(Right atrial enlargement)", "Peaked P wave >2.5mm in II, III, aVF.\nUpright/tall in V1-V2.", "Pulmonary HTN, COPD, RVH,\npulmonary stenosis"],
        ["P mitrale\n(Left atrial enlargement)", "Broad notched P in II (>120ms, 'M-shape').\nDeep terminal negative in V1 (>1mm deep, >40ms).", "Mitral stenosis/regurgitation,\nLVH, hypertension"],
        ["Absent P waves", "No visible P waves before QRS", "AF, junctional rhythm,\nhyperkalemia, SA block"],
        ["Inverted P in II", "Negative P wave in lead II", "Ectopic atrial rhythm,\njunctional rhythm, lead reversal"],
        ["Sawtooth P (flutter)", "Regular 'F' waves at 250-350/min in II, III, aVF", "Atrial flutter"],
        ["Irregular P waves", "Varying P morphology and PR intervals", "Multifocal atrial tachycardia (MAT),\nwandering pacemaker"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 75*mm, 50*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Determining Sinus Rhythm", styles['section']))
    el.append(Paragraph("For a rhythm to be called 'sinus rhythm', ALL of the following must be true:", styles['body']))
    criteria = [
        "P wave precedes every QRS complex",
        "P wave is upright (positive) in lead II",
        "P wave is inverted (negative) in aVR",
        "PR interval is constant between 120-200 ms",
        "One P wave for every QRS (1:1 ratio)",
    ]
    for c in criteria:
        el.append(Paragraph(f"  \u2713  {c}", styles['bullet']))

    el.append(PageBreak())
    return el


# ─── Chapter 7: PR Interval & AV Block ───────────────────────────────────────
def chapter7(styles):
    el = []
    el.append(chapter_header("Chapter 7", "PR Interval & AV Block Classification", styles, C_PURPLE))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("PR Interval Normal Range: 120-200 ms (3-5 small boxes)", styles['section']))
    el.append(Spacer(1, 2*mm))

    el.append(Paragraph("AV Block Classification", styles['section']))
    data = [
        ["Type", "ECG Features", "PR Interval", "Action"],
        ["1st Degree AV Block", "Prolonged PR interval.\nAll P waves conduct.\nConstant PR >200ms.", "> 200 ms\n(constant)", "Usually benign.\nMonitor. Identify cause\n(drugs, inferior MI)."],
        ["2nd Degree\nMobitz Type I\n(Wenckebach)", "PR interval progressively lengthens\nuntil one P wave fails to conduct.\nGroup beating pattern.", "Progressively\nlonging, then\nnon-conducted P", "Usually benign\n(AV node level).\nMonitor. May need\npacing if symptomatic."],
        ["2nd Degree\nMobitz Type II", "Constant PR interval.\nSudden non-conducted P wave\n(no warning).", "Constant\n(normal or long)", "HIGH RISK for\ncomplete block.\nUsually needs pacing."],
        ["2:1 AV Block", "Every other P wave conducts.\nCannot distinguish Mobitz I vs II\nwithout longer strip.", "Constant", "Treat as Mobitz II\nuntil proven otherwise."],
        ["3rd Degree\n(Complete Heart Block)", "P waves and QRS completely\ndissociated. No relationship.\nAtrial rate > ventricular rate.", "No fixed PR\n(complete\ndissociation)", "EMERGENCY.\nTypically requires\npermanent pacemaker."],
        ["Pre-excitation\n(WPW pattern)", "Short PR (<120ms).\nDelta wave (slurred QRS upstroke).\nWide QRS.", "< 120 ms", "Risk of AF with\nrapid conduction.\nEP study, ablation."],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[38*mm, 55*mm, 35*mm, 42*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(critical_box(
        "Mobitz Type II 2nd degree AV block is an unstable rhythm. Unlike Wenckebach (Type I), "
        "it occurs below the AV node (His-Purkinje) and frequently progresses to complete heart block "
        "without warning. Prophylactic pacing is typically indicated per ACC/AHA guidelines.",
        styles))

    el.append(PageBreak())
    return el


# ─── Chapter 8: QRS Complex ───────────────────────────────────────────────────
def chapter8(styles):
    el = []
    el.append(chapter_header("Chapter 8", "QRS Complex - Width, Morphology & Voltage", styles, C_RED))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("QRS Duration Classification", styles['section']))
    data = [
        ["QRS Duration", "Interpretation", "Causes"],
        ["< 80 ms (< 2 small boxes)", "Normal narrow QRS", "Normal supraventricular conduction"],
        ["80-120 ms", "Incomplete BBB or widening", "Incomplete RBBB/LBBB, hyperkalemia"],
        ["> 120 ms (> 3 small boxes)", "Wide QRS - BBB or ventricular", "RBBB, LBBB, VT, paced rhythm, hyperkalemia, antiarrhythmics"],
        ["> 160 ms", "Extremely wide", "VT, severe hyperkalemia, TCA toxicity"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 55*mm, 70*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Pathologic Q Waves", styles['section']))
    el.append(Paragraph(
        "A Q wave is a negative (downward) deflection at the start of the QRS. "
        "Small septal q waves in I, aVL, V5-V6 are normal. A Q wave is PATHOLOGIC if:", styles['body']))
    el.append(Paragraph("  • Duration > 40 ms (1 small box)", styles['bullet']))
    el.append(Paragraph("  • Amplitude > 25% of the following R wave height", styles['bullet']))
    el.append(Paragraph("  • Present in leads where Q waves are not expected (V1-V3)", styles['bullet']))
    el.append(Paragraph("  • Any Q in aVR is normal (expected)", styles['bullet']))
    el.append(Spacer(1, 2*mm))

    el.append(Paragraph("Territory of Pathologic Q Waves:", styles['subsection']))
    data2 = [
        ["Leads with Q waves", "Territory", "Artery Involved"],
        ["II, III, aVF", "Inferior wall", "RCA (80%) or LCx"],
        ["V1-V4", "Anterior wall", "LAD (left anterior descending)"],
        ["I, aVL, V5-V6", "Lateral wall", "LCx or diagonal branch of LAD"],
        ["V1-V6", "Extensive anterior", "Proximal LAD"],
        ["V7-V9 (posterior)", "Posterior wall (tall R in V1-V2)", "RCA or LCx"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[45*mm, 55*mm, 70*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Voltage Criteria", styles['section']))
    data3 = [
        ["Finding", "Criteria", "Significance"],
        ["Low voltage (limb leads)", "All QRS complexes < 5 mm in all limb leads", "Pericardial effusion, obesity,\nCOPD, hypothyroidism, amyloid"],
        ["Low voltage (precordial)", "QRS < 10 mm in all precordial leads", "Same as above"],
        ["LVH (Sokolow-Lyon)", "SV1 + RV5 or RV6 > 35 mm", "Left ventricular hypertrophy"],
        ["LVH (Cornell)", "RaVL + SV3 > 28mm (men); > 20mm (women)", "Left ventricular hypertrophy"],
        ["RVH", "R > S in V1; dominant R in V1 > 7mm; RAD", "Right ventricular hypertrophy"],
        ["Electrical alternans", "Alternating QRS height (every other beat)", "Pericardial effusion / tamponade"],
    ]
    el.append(make_table(data3[0], data3[1:], styles, col_widths=[50*mm, 60*mm, 60*mm]))

    el.append(PageBreak())
    return el


# ─── Chapter 9: Bundle Branch Blocks ─────────────────────────────────────────
def chapter9(styles):
    el = []
    el.append(chapter_header("Chapter 9", "Bundle Branch Blocks (RBBB & LBBB)", styles, C_ORANGE))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph(
        "Bundle branch blocks occur when conduction through either the right or left bundle branch "
        "is impaired, causing delayed ventricular activation on the affected side. "
        "The key diagnostic criterion is QRS duration > 120 ms.", styles['body']))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Right Bundle Branch Block (RBBB)", styles['section']))
    el.append(green_box(
        "Mnemonic: 'MaRRoW' - In V1: M-shaped pattern (RSR' or rSR'). In V6: W-shape (broad S wave). "
        "Think of V1 as the right side: M on the right (V1), W on the left (V6).",
        styles, label="MEMORY AID"))
    el.append(Spacer(1, 2*mm))

    data = [
        ["RBBB Criteria", "Detail"],
        ["QRS duration", "> 120 ms (complete RBBB); 110-120ms (incomplete RBBB)"],
        ["V1 morphology", "rSR' pattern ('rabbit ears' or 'M' pattern)"],
        ["V6 morphology", "Wide, slurred S wave (W pattern)"],
        ["Lead I / V6", "Broad, slurred S wave (terminal S wave)"],
        ["ST changes", "Secondary ST-T changes (ST depression, T inversion in V1-V3) - EXPECTED"],
        ["Common causes", "Normal variant, RVH, PE, ischemia (RCA territory), congenital, post-cardiac surgery"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[55*mm, 115*mm]))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Left Bundle Branch Block (LBBB)", styles['section']))
    el.append(warning_box(
        "New LBBB in a patient with chest pain should be treated as STEMI equivalent "
        "until proven otherwise (Sgarbossa criteria apply). New LBBB = activate cath lab per guidelines.",
        styles))
    el.append(Spacer(1, 2*mm))
    el.append(green_box(
        "Mnemonic: 'WiLLiaM' - In V1: W pattern (deep QS or rS). In V6: M pattern (broad tall R). "
        "Think 'W' on left (V1 looks like W), 'M' on right (V6 looks like M) -- reversed from RBBB.",
        styles, label="MEMORY AID"))
    el.append(Spacer(1, 2*mm))

    data2 = [
        ["LBBB Criteria", "Detail"],
        ["QRS duration", "> 120 ms"],
        ["V1 morphology", "Broad QS or rS (deep, wide, no R or tiny r)"],
        ["V6 morphology", "Tall, broad, notched R wave (no Q, no S) - monophasic R"],
        ["Lead I / aVL", "Broad R wave (no S wave)"],
        ["ST-T changes", "Discordant: ST and T wave should be OPPOSITE to QRS direction"],
        ["Concordant ST (abnormal!)", "ST in same direction as QRS = suggests true ischemia (Sgarbossa +3 points)"],
        ["Common causes", "CAD, LVH, dilated cardiomyopathy, hypertension, aortic stenosis"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[55*mm, 115*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Sgarbossa Criteria for MI in LBBB", styles['section']))
    data3 = [
        ["Criterion", "Points", "Sensitivity"],
        ["Concordant ST elevation >= 1mm in any lead", "+5", "High specificity for MI"],
        ["Concordant ST depression >= 1mm in V1, V2, or V3", "+3", "Moderate sensitivity"],
        ["Excessively discordant ST elevation >= 5mm (ST/S ratio > 0.25)", "+2", "Less specific alone"],
    ]
    el.append(make_table(data3[0], data3[1:], styles, col_widths=[90*mm, 25*mm, 55*mm]))
    el.append(Paragraph("Score >= 3 points: High specificity for acute MI. Modified Sgarbossa uses ST/S ratio > 0.25.", styles['note']))

    el.append(PageBreak())
    return el


# ─── Chapter 10: ST Segments ──────────────────────────────────────────────────
def chapter10(styles):
    el = []
    el.append(chapter_header("Chapter 10", "ST Segment Analysis & Ischemia", styles, C_DARK_RED))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph(
        "The ST segment reflects the plateau phase of ventricular action potential. "
        "It should be isoelectric (at baseline). Deviations are the most important ECG finding for "
        "identifying acute myocardial ischemia and infarction.", styles['body']))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("ST Elevation - Differential Diagnosis", styles['section']))
    data = [
        ["Cause", "ST Pattern", "Distinguishing Features"],
        ["STEMI (acute MI)", "Convex ('tombstone') elevation in contiguous leads", "Reciprocal depression; evolves over hours; Q waves later"],
        ["Early repolarization", "Concave ('smiley face') elevation; J-point notching", "Young male; diffuse; stable; no reciprocal changes; benign"],
        ["Pericarditis", "Diffuse concave ST elevation; PR depression", "All leads affected (except aVR); saddle-shaped; no reciprocal"],
        ["LV aneurysm", "Persistent ST elevation months after MI", "Fixed elevation; no evolution; associated Q waves"],
        ["LBBB (new)", "Discordant ST changes", "Wide QRS; treat as STEMI equivalent per guidelines"],
        ["Vasospasm (Prinzmetal)", "Transient ST elevation, resolving spontaneously", "Often at rest; cocaine; no fixed atherosclerosis"],
        ["Hyperkalemia", "Diffuse elevation with peaked T waves", "Serum K+ > 6.5; peaked T waves; wide QRS; sine wave"],
        ["Brugada syndrome", "ST elevation V1-V2 with RBBB morphology; coved pattern", "Male; syncope/SCA; no ischemia; genetic channelopathy"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[40*mm, 65*mm, 65*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("ST Depression - Differential Diagnosis", styles['section']))
    data2 = [
        ["Cause", "ST Pattern", "Leads Affected"],
        ["Subendocardial ischemia / NSTEMI", "Horizontal or downsloping depression >= 1mm", "Diffuse or regional"],
        ["Reciprocal changes (in STEMI)", "Depression opposite to elevation", "Leads opposite to infarcted territory"],
        ["LVH strain pattern", "Downsloping ST with asymmetric T inversion", "V5-V6, I, aVL (lateral leads)"],
        ["Digoxin effect", "Scooped/reversed tick shape", "Lateral leads V5-V6; II, III, aVF"],
        ["Tachycardia", "Diffuse depression at rapid rates", "Widespread; resolves with rate control"],
        ["RBBB", "Secondary ST depression in V1-V3", "V1-V3 (expected; secondary change)"],
        ["Hypokalemia", "ST depression with prominent U waves", "Lateral leads; associated flat T + tall U"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[50*mm, 65*mm, 55*mm]))

    el.append(PageBreak())
    return el


# ─── Chapter 11: T Waves ──────────────────────────────────────────────────────
def chapter11(styles):
    el = []
    el.append(chapter_header("Chapter 11", "T Wave Abnormalities", styles, C_TEAL))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Normal T Wave", styles['section']))
    el.append(green_box(
        "Upright in leads I, II, V3-V6. Inverted in aVR (always). Variable in III, aVL, V1-V2. "
        "T wave should be in same direction as QRS (concordant). Amplitude < 5mm (limb), < 10mm (precordial).",
        styles, label="NORMAL"))
    el.append(Spacer(1, 3*mm))

    data = [
        ["T Wave Abnormality", "Description", "Causes"],
        ["Peaked / hyperacute T waves", "Tall, symmetric, tent-shaped T waves", "Hyperkalemia (earliest sign), hyperacute STEMI"],
        ["T wave inversion\n(deep symmetric)", "Deeply inverted symmetric T waves", "Myocardial ischemia/infarction, PE (right precordial), CNS events (deep inv.), takotsubo"],
        ["Wellens pattern Type A", "Biphasic T waves in V2-V3 (up then down)", "CRITICAL: proximal LAD stenosis - impending anterior MI"],
        ["Wellens pattern Type B", "Deep symmetric T inversion V2-V4", "CRITICAL: proximal LAD stenosis - impending anterior MI"],
        ["LVH strain T inversion", "Asymmetric T inversion in lateral leads", "V5, V6, I, aVL - left ventricular hypertrophy with strain"],
        ["Right heart strain T inv.", "T inversion V1-V4 (right precordial)", "PE, RVH, RV strain - classic with S1Q3T3 in PE"],
        ["Flat / flattened T waves", "T wave amplitude < 1mm", "Ischemia, hypokalemia, hypothyroidism, normal variant"],
        ["Biphasic T waves", "Positive then negative deflection", "Ischemia, Wellens, hypokalemia"],
        ["De Winter T waves", "ST depression with tall T waves V2-V6", "STEMI equivalent - proximal LAD occlusion; no ST elevation!"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 65*mm, 60*mm]))
    el.append(Spacer(1, 3*mm))
    el.append(critical_box(
        "Wellens pattern and De Winter T waves are STEMI equivalents that may not show classic ST elevation. "
        "These indicate critical LAD stenosis or occlusion. Patients are often pain-free when the ECG is taken. "
        "Urgent cardiology consultation and cath lab activation is required.",
        styles))

    el.append(PageBreak())
    return el


# ─── Chapter 12: QT Interval ──────────────────────────────────────────────────
def chapter12(styles):
    el = []
    el.append(chapter_header("Chapter 12", "QT Interval & Long QT Syndrome", styles, C_PURPLE))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph(
        "The QT interval represents total ventricular electrical systole (depolarization + repolarization). "
        "It must always be rate-corrected (QTc) because QT shortens at faster rates.", styles['body']))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("QTc Normal Values", styles['section']))
    data = [
        ["QTc Range", "Men", "Women", "Interpretation"],
        ["Normal", "< 440 ms", "< 460 ms", "No increased risk"],
        ["Borderline prolonged", "440-460 ms", "460-480 ms", "Monitor; review medications"],
        ["Prolonged", "460-500 ms", "> 480 ms", "Increased Torsades risk; ECG monitoring"],
        ["Critical prolongation", "> 500 ms", "> 500 ms", "HIGH risk of Torsades de Pointes"],
        ["Short QT", "< 340 ms", "< 340 ms", "Short QT syndrome; risk of VF/SCA"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 30*mm, 30*mm, 65*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Causes of QT Prolongation", styles['section']))
    el.append(Paragraph("<b>Medications (most common cause):</b>", styles['subsection']))
    med_data = [
        ["Drug Class", "Examples"],
        ["Antiarrhythmics (Class Ia)", "Quinidine, Procainamide, Disopyramide"],
        ["Antiarrhythmics (Class III)", "Amiodarone, Sotalol, Dofetilide, Ibutilide"],
        ["Antibiotics", "Azithromycin, Clarithromycin, Fluoroquinolones (Ciprofloxacin, Moxifloxacin)"],
        ["Antipsychotics", "Haloperidol, Quetiapine, Ziprasidone, Chlorpromazine"],
        ["Antidepressants", "TCAs (Amitriptyline), Citalopram"],
        ["Antiemetics", "Ondansetron, Domperidone, Metoclopramide"],
        ["Antifungals", "Fluconazole, Voriconazole"],
        ["Others", "Methadone, Hydroxychloroquine, Pentamidine"],
    ]
    el.append(make_table(med_data[0], med_data[1:], styles, col_widths=[55*mm, 115*mm]))
    el.append(Spacer(1, 2*mm))

    el.append(Paragraph("<b>Electrolyte Abnormalities:</b>", styles['subsection']))
    el.append(Paragraph("  • Hypokalemia (most common electrolyte cause)", styles['bullet']))
    el.append(Paragraph("  • Hypomagnesemia (synergistic with hypokalemia)", styles['bullet']))
    el.append(Paragraph("  • Hypocalcemia", styles['bullet']))

    el.append(Paragraph("<b>Congenital / Other:</b>", styles['subsection']))
    el.append(Paragraph("  • Long QT syndrome (LQTS) types 1-3 (genetic channelopathies, SCN5A, KCNQ1, KCNH2)", styles['bullet']))
    el.append(Paragraph("  • Hypothyroidism, hypothermia, cardiac ischemia, autonomic dysfunction", styles['bullet']))

    el.append(Spacer(1, 2*mm))
    el.append(critical_box(
        "Torsades de Pointes (TdP) is a polymorphic ventricular tachycardia occurring in the context "
        "of a prolonged QT. It appears as a 'twisting' of QRS complexes around the baseline. "
        "Treatment: IV Magnesium 2g (even if Mg is normal), correct electrolytes, stop QT-prolonging drugs, "
        "overdrive pacing. Do NOT use amiodarone (prolongs QT further).", styles))

    el.append(PageBreak())
    return el


# ─── Chapter 13: STEMI Localization ───────────────────────────────────────────
def chapter13(styles):
    el = []
    el.append(chapter_header("Chapter 13", "STEMI Recognition & Territory Localization", styles, C_DARK_RED))
    el.append(Spacer(1, 4*mm))

    el.append(critical_box(
        "STEMI criteria: ST elevation >= 1mm in 2+ contiguous limb leads OR "
        ">= 2mm in 2+ contiguous precordial leads (men age < 40: >= 2.5mm in V2-V3). "
        "Time to reperfusion: < 90 min (primary PCI) or < 30 min (fibrinolysis if PCI not available).",
        styles))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("STEMI Localization by Lead Territory", styles['section']))
    data = [
        ["Infarct Territory", "Leads with ST Elevation", "Reciprocal ST Depression", "Culprit Artery"],
        ["Inferior", "II, III, aVF", "I, aVL (±V1-V4)", "RCA (80%) or LCx (20%)"],
        ["Anterior", "V1, V2, V3, V4", "None typically", "LAD (left anterior descending)"],
        ["Septal", "V1, V2", "None", "Septal branch of LAD"],
        ["Lateral", "I, aVL, V5, V6", "II, III, aVF", "LCx or diagonal of LAD"],
        ["Anterolateral", "I, aVL, V1-V6", "II, III, aVF", "Proximal LAD"],
        ["Extensive anterior", "V1-V6 + I, aVL", "II, III, aVF", "Proximal LAD (widow maker)"],
        ["High lateral", "I, aVL", "II, III, aVF", "First diagonal of LAD or LCx"],
        ["Posterior (true)", "V7-V9 (if recorded); tall R, ST dep V1-V3", "ST depression V1-V2\n(mirror image)", "RCA or LCx"],
        ["Right ventricular (RV)", "V1, and V3R-V4R (right-sided leads)", "Usually inferior STEMI too", "Proximal RCA"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[38*mm, 42*mm, 42*mm, 48*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(warning_box(
        "Right ventricular MI (RV-MI): Occurs with inferior STEMI. Record right-sided leads (V3R-V4R). "
        "ST elevation >= 1mm in V4R is diagnostic. CRITICAL: Avoid nitrates and diuretics "
        "(preload-dependent). Fluid challenge is first-line treatment.",
        styles))
    el.append(Spacer(1, 2*mm))
    el.append(warning_box(
        "Posterior MI: Look for dominant R wave in V1-V2 + horizontal ST depression in V1-V3. "
        "Record V7-V9 (left posterior leads) to confirm. ST elevation in V7-V9 >= 0.5mm is diagnostic.",
        styles, label="POSTERIOR MI"))

    el.append(Paragraph("STEMI Mimics - Do Not Activate Cath Lab For:", styles['section']))
    data2 = [
        ["Mimic", "Key Differentiating Features"],
        ["Early repolarization", "Concave ST elevation; J-point notching; young male; no evolution; benign"],
        ["LV aneurysm", "Persistent ST elevation for weeks-months; Q waves; no dynamic change; prior MI"],
        ["Pericarditis", "Diffuse ST elevation (all leads); PR depression; saddle-shaped; no Q waves; chest pain pleuritic"],
        ["LBBB (old known)", "Pre-existing LBBB; no new symptoms; Sgarbossa criteria negative"],
        ["Brugada pattern", "ST elevation only V1-V2; coved pattern; no coronary disease; genetic"],
        ["Hyperkalemia", "Peaked T waves; wide QRS; sinusoidal pattern; serum K+ elevated"],
        ["Takotsubo (stress CM)", "Anterior ST elevation; apical ballooning; women; emotional stress trigger"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[50*mm, 120*mm]))

    el.append(PageBreak())
    return el


# ─── Chapter 14: Arrhythmias ──────────────────────────────────────────────────
def chapter14(styles):
    el = []
    el.append(chapter_header("Chapter 14", "Arrhythmia Recognition", styles, C_GREEN))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Supraventricular Arrhythmias", styles['section']))
    data = [
        ["Arrhythmia", "Rate", "Rhythm", "P Wave", "QRS"],
        ["Sinus tachycardia", "100-180", "Regular", "Normal, before QRS", "Narrow"],
        ["Sinus bradycardia", "< 60", "Regular", "Normal, before QRS", "Narrow"],
        ["Atrial fibrillation (AF)", "350-600 (atria); 60-170 (ventricles)", "Irregularly irregular", "Absent; fibrillatory f waves", "Narrow (unless aberrant)"],
        ["Atrial flutter", "250-350 (atria); 75-175 (ventricles)", "Regular (2:1, 3:1, 4:1)", "Sawtooth F waves 300/min", "Narrow; may be wide"],
        ["SVT / AVNRT", "150-250", "Regular", "Hidden in QRS or retrograde", "Narrow"],
        ["MAT", "100-150+", "Irregular", ">= 3 P morphologies", "Narrow"],
        ["Junctional rhythm", "40-60", "Regular", "Absent, inverted, or after QRS", "Narrow"],
        ["WPW (pre-excitation)", "Variable (sinus or tach)", "Variable", "Short PR, delta wave", "Wide, slurred onset"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[38*mm, 28*mm, 28*mm, 40*mm, 36*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Ventricular Arrhythmias", styles['section']))
    data2 = [
        ["Arrhythmia", "Rate", "QRS", "Features", "Risk"],
        ["PVC (premature beat)", "Variable", "> 120 ms; wide", "Compensatory pause; T wave opposite QRS", "Low (unless frequent or structural heart disease)"],
        ["NSVT", "100-250; < 30 sec", "Wide", "3+ consecutive wide beats, self-terminating", "Investigate for structural heart disease"],
        ["Ventricular tachycardia (VT)", "> 100 (usually 100-250)", "Wide (> 120 ms)", "AV dissociation; fusion/capture beats; concordance precordial leads", "HIGH - cardiac emergency"],
        ["Ventricular fibrillation (VF)", "Chaotic (300-500)", "No organized QRS", "Chaotic, irregular, no discernible complexes", "FATAL without immediate defibrillation"],
        ["Torsades de Pointes", "200-250", "Wide, twisting", "QRS 'twists' around isoelectric line; long QT baseline", "HIGH - defibrillation / IV Mg"],
        ["Accelerated idioventricular (AIVR)", "60-120", "Wide", "Seen in reperfusion; benign usually", "Low"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[38*mm, 22*mm, 22*mm, 52*mm, 36*mm]))
    el.append(Spacer(1, 3*mm))
    el.append(critical_box(
        "VT vs SVT with aberrancy: Features favoring VT: AV dissociation (independent P waves), "
        "fusion/capture beats, concordance in precordial leads (all positive or all negative), "
        "QRS > 160ms, extreme axis deviation. When uncertain - TREAT AS VT.",
        styles))

    el.append(PageBreak())
    return el


# ─── Chapter 15: Hypertrophy ──────────────────────────────────────────────────
def chapter15(styles):
    el = []
    el.append(chapter_header("Chapter 15", "Ventricular Hypertrophy Criteria", styles, C_ORANGE))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Left Ventricular Hypertrophy (LVH)", styles['section']))
    data = [
        ["Criterion", "Threshold", "Sensitivity / Notes"],
        ["Sokolow-Lyon", "SV1 + RV5 (or RV6) > 35 mm", "~50% sensitivity; specific"],
        ["Cornell (men)", "RaVL + SV3 > 28 mm", "Higher sensitivity than Sokolow-Lyon"],
        ["Cornell (women)", "RaVL + SV3 > 20 mm", "Gender-adjusted criterion"],
        ["aVL amplitude", "R wave in aVL > 11 mm", "Simple single-lead criterion"],
        ["Strain pattern", "Downsloping ST depression + T inversion lateral (V5-V6, I, aVL)", "Suggests pressure overload"],
        ["P mitrale", "Broad notched P in II; deep terminal V1 negativity", "Suggests LA enlargement = LVH correlate"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[45*mm, 55*mm, 70*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Right Ventricular Hypertrophy (RVH)", styles['section']))
    data2 = [
        ["Criterion", "Finding"],
        ["R > S in V1", "Dominant R wave in V1 (> 7mm) - most specific criterion"],
        ["Right axis deviation", "Axis > +90° (usually > +110° in significant RVH)"],
        ["S waves in lateral leads", "Persistent deep S waves in I, V5, V6"],
        ["R/S ratio V5 or V6 < 1", "S wave equals or dominates R in lateral leads"],
        ["qR pattern in V1", "Small q + dominant R in V1 (severe RVH)"],
        ["Strain pattern", "ST depression + T inversion in V1-V3 (right precordial strain)"],
        ["P pulmonale", "Peaked P wave > 2.5mm in II (right atrial enlargement)"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[60*mm, 110*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Causes of Hypertrophy", styles['section']))
    causes = [
        ["LVH Causes", "RVH Causes"],
        ["Systemic hypertension (most common)", "Pulmonary arterial hypertension"],
        ["Aortic stenosis", "COPD / cor pulmonale"],
        ["Hypertrophic cardiomyopathy (HCM)", "Pulmonary embolism (acute RV strain)"],
        ["Athletic heart", "Pulmonary stenosis"],
        ["Aortic / mitral regurgitation", "Congenital heart disease (Tetralogy of Fallot)"],
        ["Coarctation of the aorta", "Mitral stenosis (2nd to LA/RV pressure)"],
    ]
    t = Table(causes, colWidths=[85*mm, 85*mm])
    t.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,0), C_HEADER_BG),
        ('TEXTCOLOR', (0,0), (-1,0), C_WHITE),
        ('FONTNAME', (0,0), (-1,0), 'Helvetica-Bold'),
        ('FONTSIZE', (0,0), (-1,-1), 9),
        ('ROWBACKGROUNDS', (0,1), (-1,-1), [C_WHITE, C_LIGHT_BG]),
        ('GRID', (0,0), (-1,-1), 0.5, C_GRID),
        ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ('LEFTPADDING', (0,0), (-1,-1), 6),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
    ]))
    el.append(t)

    el.append(PageBreak())
    return el


# ─── Chapter 16: Quick Reference ──────────────────────────────────────────────
def chapter16(styles):
    el = []
    el.append(chapter_header("Chapter 16", "Quick Reference Cards & Differentials", styles, C_TEAL))
    el.append(Spacer(1, 4*mm))

    el.append(Paragraph("Normal ECG Values - Pocket Summary", styles['section']))
    data = [
        ["Parameter", "Normal Value"],
        ["Heart rate", "60-100 bpm"],
        ["PR interval", "120-200 ms (3-5 small boxes)"],
        ["QRS duration", "< 120 ms (< 3 small boxes)"],
        ["QTc (men)", "< 440 ms"],
        ["QTc (women)", "< 460 ms"],
        ["P wave duration", "< 120 ms"],
        ["P wave amplitude", "< 2.5mm in lead II"],
        ["Q wave (septal)", "< 40 ms; < 25% of R amplitude"],
        ["ST deviation", "< 1mm limb leads; < 2mm V2-V3 (men)"],
        ["T wave (upright)", "Leads I, II, V3-V6"],
        ["T wave (inverted)", "Normal in aVR; variable aVL, III, V1"],
        ["Cardiac axis (adult)", "0° to +90° (up to -30° accepted)"],
    ]
    el.append(make_table(data[0], data[1:], styles, col_widths=[70*mm, 100*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("Wide QRS Differential Diagnosis", styles['section']))
    data2 = [
        ["Cause", "Clue to Diagnosis"],
        ["RBBB", "RSR' in V1; broad S in I, V6; QRS 120-160ms"],
        ["LBBB", "Broad R in V6; no R in V1; discordant ST-T"],
        ["Ventricular tachycardia", "AV dissociation; fusion beats; no prior BBB; HR 100-250"],
        ["Paced rhythm", "Pacing spike before QRS; LBBB morphology (RV lead)"],
        ["Pre-excitation (WPW)", "Delta wave; short PR; variable width"],
        ["Hyperkalemia", "Peaked T + wide QRS; can be sine-wave pattern; toxic K+"],
        ["Sodium channel toxicity", "TCA overdose; wide QRS + right axis; brugada-like"],
        ["Aberrant conduction", "SVT with BBB; rate-related BBB (Ashman's in AF)"],
    ]
    el.append(make_table(data2[0], data2[1:], styles, col_widths=[55*mm, 115*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(Paragraph("ECG Findings in Common Clinical Scenarios", styles['section']))
    data3 = [
        ["Scenario", "Key ECG Findings"],
        ["Pulmonary embolism", "Sinus tach (most common); S1Q3T3; RBBB or incomplete RBBB; T inversion V1-V4; right heart strain"],
        ["Digoxin toxicity", "'Scooped' ST (reverse tick) lateral leads; bradyarrhythmias; PAT with block; bidirectional VT"],
        ["Hyperkalemia", "Peaked T → PR prolongation → P waves disappear → wide QRS → sine wave → VF"],
        ["Hypokalemia", "Flat T waves; prominent U waves; ST depression; apparent QT prolongation (QU prolongation)"],
        ["Hypothermia", "Osborn (J) waves; sinus bradycardia; long intervals; artifact from shivering"],
        ["Cardiac tamponade", "Sinus tachycardia; low voltage; electrical alternans (pathognomonic)"],
        ["Hypertrophic CM", "LVH voltage; deep narrow Q waves (septal hypertrophy) in I, V5, V6; apical pattern"],
        ["Acute pericarditis", "Diffuse concave ST elevation; PR depression in II; PR elevation aVR; saddle shape"],
    ]
    el.append(make_table(data3[0], data3[1:], styles, col_widths=[50*mm, 120*mm]))
    el.append(Spacer(1, 3*mm))

    el.append(note_box(
        "References: Braunwald's Heart Disease 12th Ed (Elsevier, 2022); Fuster & Hurst's The Heart 15th Ed "
        "(McGraw-Hill, 2022); Roberts & Hedges' Clinical Procedures in Emergency Medicine 7th Ed (Elsevier, 2019); "
        "ACC/AHA/HRS Guideline for Evaluation and Management of Patients with Bradycardia and Cardiac Conduction "
        "Delay (Circulation, 2019); ESC Guidelines on Ventricular Arrhythmias (Eur Heart J, 2022).",
        styles, label="REFERENCES"))

    return el


# ─── Main Build Function ───────────────────────────────────────────────────────
def build():
    doc = SimpleDocTemplate(
        OUTPUT_PATH,
        pagesize=A4,
        topMargin=22*mm,
        bottomMargin=16*mm,
        leftMargin=20*mm,
        rightMargin=20*mm,
        title="ECG Interpretation Reference Guide",
        author="Orris Medical Reference",
        subject="12-Lead ECG Systematic Interpretation",
    )

    styles = get_styles()
    story = []

    # Cover page (no header/footer)
    story.extend(build_cover(styles))

    # All remaining pages use header/footer
    story.extend(build_toc(styles))
    story.extend(chapter1(styles))
    story.extend(chapter2(styles))
    story.extend(chapter3(styles))
    story.extend(chapter4(styles))
    story.extend(chapter5(styles))
    story.extend(chapter6(styles))
    story.extend(chapter7(styles))
    story.extend(chapter8(styles))
    story.extend(chapter9(styles))
    story.extend(chapter10(styles))
    story.extend(chapter11(styles))
    story.extend(chapter12(styles))
    story.extend(chapter13(styles))
    story.extend(chapter14(styles))
    story.extend(chapter15(styles))
    story.extend(chapter16(styles))

    doc.build(story, onFirstPage=lambda c, d: None, onLaterPages=make_header_footer)
    print(f"PDF generated: {OUTPUT_PATH}")


if __name__ == "__main__":
    build()