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

# ── Colour palette ────────────────────────────────────────────────────────────
NAVY       = HexColor("#1a3a5c")
TEAL       = HexColor("#0d7377")
LIGHT_TEAL = HexColor("#e8f7f8")
GOLD       = HexColor("#e8a020")
LIGHT_GOLD = HexColor("#fdf4e3")
LIGHT_GREY = HexColor("#f4f6f9")
MID_GREY   = HexColor("#d0d7e2")
RED_SOFT   = HexColor("#c0392b")
GREEN_SOFT = HexColor("#1e8449")
WHITE      = colors.white

PAGE_W, PAGE_H = A4

# ── Document ──────────────────────────────────────────────────────────────────
OUTPUT = "/home/daytona/workspace/opd-cases/OPD_Patient_Cases_Educational.pdf"

doc = SimpleDocTemplate(
    OUTPUT,
    pagesize=A4,
    leftMargin=2*cm, rightMargin=2*cm,
    topMargin=2.5*cm, bottomMargin=2.5*cm,
    title="OPD Patient Cases – Educational Prescriptions",
    author="Medical Education Unit",
    subject="Clinical Practice & Pharmacology"
)

# ── Styles ────────────────────────────────────────────────────────────────────
base = getSampleStyleSheet()

def S(name, **kw):
    return ParagraphStyle(name, parent=base["Normal"], **kw)

sTitle      = S("sTitle",      fontSize=26, textColor=WHITE,      alignment=TA_CENTER,
                fontName="Helvetica-Bold", leading=32)
sSubTitle   = S("sSubTitle",   fontSize=12, textColor=LIGHT_TEAL, alignment=TA_CENTER,
                fontName="Helvetica", leading=16)
sDate       = S("sDate",       fontSize=9,  textColor=LIGHT_GOLD, alignment=TA_CENTER,
                fontName="Helvetica-Oblique")

sCaseNum    = S("sCaseNum",    fontSize=14, textColor=WHITE,      fontName="Helvetica-Bold",
                alignment=TA_LEFT, leading=18)
sCaseTitle  = S("sCaseTitle",  fontSize=11, textColor=LIGHT_TEAL, fontName="Helvetica",
                alignment=TA_LEFT, leading=14)

sSection    = S("sSection",    fontSize=10, textColor=NAVY,       fontName="Helvetica-Bold",
                spaceAfter=3, leading=14)
sBody       = S("sBody",       fontSize=9.5, textColor=HexColor("#2c3e50"),
                fontName="Helvetica", leading=14, spaceAfter=2)
sBullet     = S("sBullet",     fontSize=9.5, textColor=HexColor("#2c3e50"),
                fontName="Helvetica", leading=14, leftIndent=14, spaceAfter=1,
                bulletIndent=4)
sReason     = S("sReason",     fontSize=9.5, textColor=HexColor("#1a5276"),
                fontName="Helvetica-Oblique", leading=14, leftIndent=14, spaceAfter=1)
sWarning    = S("sWarning",    fontSize=8.5, textColor=RED_SOFT,
                fontName="Helvetica-Bold", leading=12, leftIndent=14)
sGreen      = S("sGreen",      fontSize=8.5, textColor=GREEN_SOFT,
                fontName="Helvetica-Bold", leading=12, leftIndent=14)
sFooterNote = S("sFooterNote", fontSize=7.5, textColor=HexColor("#7f8c8d"),
                fontName="Helvetica-Oblique", alignment=TA_CENTER)
sTocEntry   = S("sTocEntry",   fontSize=10, textColor=NAVY, fontName="Helvetica", leading=16)

# ── Helper: coloured banner ───────────────────────────────────────────────────
class ColourBanner(Flowable):
    def __init__(self, bg, height=1.4*cm, radius=8):
        super().__init__()
        self.bg = bg
        self.height = height
        self.radius = radius

    def wrap(self, aw, ah):
        self.width = aw
        return aw, self.height

    def draw(self):
        c = self.canv
        c.setFillColor(self.bg)
        c.roundRect(0, 0, self.width, self.height,
                    radius=self.radius, stroke=0, fill=1)

def case_header(num, title, subtitle=""):
    banner = ColourBanner(NAVY, height=1.55*cm)
    items = [banner]
    # overlay text using a table over the banner via absolute positioning trick:
    # instead, place text directly after banner via a negative spacer trick –
    # simplest: use a 1-row table
    header_data = [[
        Paragraph(f"CASE {num}", sCaseNum),
        Paragraph(title, sCaseTitle)
    ]]
    t = Table(header_data, colWidths=[2.8*cm, None])
    t.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), NAVY),
        ("VALIGN",     (0,0), (-1,-1), "MIDDLE"),
        ("LEFTPADDING",(0,0), (0,0),  12),
        ("LEFTPADDING",(1,0), (1,0),   6),
        ("TOPPADDING", (0,0), (-1,-1), 10),
        ("BOTTOMPADDING",(0,0),(-1,-1),10),
        ("ROUNDEDCORNERS", [8]),
    ]))
    return [t]

def section_label(text, icon=""):
    return Paragraph(f"{icon} {text}" if icon else text, sSection)

def body(text):
    return Paragraph(text, sBody)

def bullet(text):
    return Paragraph(f"• {text}", sBullet)

def reason(text):
    return Paragraph(f"↳ {text}", sReason)

def warn(text):
    return Paragraph(f"⚠ {text}", sWarning)

def ok(text):
    return Paragraph(f"✔ {text}", sGreen)

def gap(h=0.25):
    return Spacer(1, h*cm)

def hr(color=MID_GREY, thickness=0.5):
    return HRFlowable(width="100%", thickness=thickness, color=color, spaceAfter=4, spaceBefore=4)

def prescription_table(rows):
    """rows = list of (Drug, Dose/Route, Frequency, Duration)"""
    header = ["Drug", "Dose / Route", "Frequency", "Duration"]
    data   = [header] + rows
    col_w  = [5.8*cm, 3.8*cm, 3.2*cm, 2.4*cm]
    t = Table(data, colWidths=col_w, repeatRows=1)
    t.setStyle(TableStyle([
        # header
        ("BACKGROUND",   (0,0), (-1,0),  TEAL),
        ("TEXTCOLOR",    (0,0), (-1,0),  WHITE),
        ("FONTNAME",     (0,0), (-1,0),  "Helvetica-Bold"),
        ("FONTSIZE",     (0,0), (-1,0),  9),
        ("ALIGN",        (0,0), (-1,0),  "CENTER"),
        # body
        ("FONTNAME",     (0,1), (-1,-1), "Helvetica"),
        ("FONTSIZE",     (0,1), (-1,-1), 9),
        ("ROWBACKGROUNDS",(0,1),(-1,-1), [WHITE, LIGHT_TEAL]),
        ("ALIGN",        (1,1), (-1,-1), "CENTER"),
        ("VALIGN",       (0,0), (-1,-1), "MIDDLE"),
        ("TOPPADDING",   (0,0), (-1,-1), 6),
        ("BOTTOMPADDING",(0,0), (-1,-1), 6),
        ("LEFTPADDING",  (0,0), (0,-1),  8),
        ("GRID",         (0,0), (-1,-1), 0.4, MID_GREY),
        ("ROUNDEDCORNERS",[4]),
    ]))
    return t

def info_table(pairs):
    """pairs = [(label, value), ...]  – patient info block"""
    data = pairs
    col_w = [3.8*cm, 11.6*cm]
    t = Table(data, colWidths=col_w)
    t.setStyle(TableStyle([
        ("BACKGROUND",   (0,0), (0,-1),  LIGHT_GREY),
        ("FONTNAME",     (0,0), (0,-1),  "Helvetica-Bold"),
        ("FONTNAME",     (1,0), (1,-1),  "Helvetica"),
        ("FONTSIZE",     (0,0), (-1,-1), 9),
        ("TEXTCOLOR",    (0,0), (0,-1),  NAVY),
        ("TEXTCOLOR",    (1,0), (1,-1),  HexColor("#2c3e50")),
        ("TOPPADDING",   (0,0), (-1,-1), 5),
        ("BOTTOMPADDING",(0,0), (-1,-1), 5),
        ("LEFTPADDING",  (0,0), (-1,-1), 8),
        ("GRID",         (0,0), (-1,-1), 0.3, MID_GREY),
        ("ROWBACKGROUNDS",(0,0),(-1,-1), [WHITE, LIGHT_GREY]),
    ]))
    return t

# ══════════════════════════════════════════════════════════════════════════════
# CASES DATA
# ══════════════════════════════════════════════════════════════════════════════

CASES = [
    # ── CASE 1 ──────────────────────────────────────────────────────────────
    {
        "num": 1,
        "title": "Acute Upper Respiratory Tract Infection (Viral URTI)",
        "patient": [
            ("Name", "Mr. Ravi Sharma"),
            ("Age / Sex", "34 years / Male"),
            ("Occupation", "School Teacher"),
            ("Vitals", "BP 118/76 mmHg | HR 82/min | Temp 38.1°C | SpO₂ 98% (RA)"),
        ],
        "presenting_complaint": "Sore throat, runny nose, mild headache and low-grade fever for 3 days.",
        "history": [
            "No past medical history of asthma, diabetes, or hypertension.",
            "No known drug allergies.",
            "Several colleagues with similar symptoms in the past week.",
            "Non-smoker, occasional alcohol."
        ],
        "examination": [
            "Throat: mildly erythematous, no exudate, no tonsillar enlargement.",
            "Cervical lymph nodes: non-tender, not significantly enlarged.",
            "Chest: clear on auscultation.",
            "Rapid antigen test (Group A Strep): NEGATIVE."
        ],
        "diagnosis": "Viral URTI (Common Cold / Viral Pharyngitis)",
        "prescription": [
            ("Paracetamol 500 mg", "500 mg – Oral", "TDS (if febrile/pain)", "5 days"),
            ("Cetirizine 10 mg", "10 mg – Oral", "OD at bedtime", "5 days"),
            ("Normal Saline Nasal Drops", "2 drops each nostril", "QID", "5 days"),
            ("ORS Sachets", "1 sachet in 200 mL water", "Sip frequently", "PRN"),
        ],
        "reasoning": [
            ("Paracetamol",
             "Antipyretic and analgesic. Reduces fever and relieves sore throat pain. "
             "First-line choice in viral illness; safe hepatic metabolism; no renal prostaglandin inhibition concern."),
            ("Cetirizine",
             "Second-generation H1-antihistamine. Reduces rhinorrhoea, nasal congestion, and sneezing "
             "without significant sedation. Preferred over first-generation (e.g. chlorphenamine) due to fewer anticholinergic side effects."),
            ("Saline Nasal Drops",
             "Isotonic saline rinses help clear nasal secretions, reduce mucosal oedema, and improve ciliary function. "
             "Safe for all ages; no systemic side effects."),
            ("ORS",
             "Fever increases insensible fluid losses. ORS replaces water and electrolytes, preventing dehydration. "
             "Glucose-sodium co-transport mechanism ensures efficient intestinal absorption."),
        ],
        "antibiotics_note": "NO antibiotics prescribed – Strep test negative; viral aetiology confirmed. "
                            "Antibiotic stewardship is essential to prevent resistance.",
        "follow_up": "Return if fever >39°C persists beyond 5 days, dyspnoea, severe odynophagia, or rash develops.",
    },

    # ── CASE 2 ──────────────────────────────────────────────────────────────
    {
        "num": 2,
        "title": "Type 2 Diabetes Mellitus – New Diagnosis",
        "patient": [
            ("Name", "Mrs. Sunita Verma"),
            ("Age / Sex", "52 years / Female"),
            ("Occupation", "Housewife"),
            ("Vitals", "BP 132/84 mmHg | HR 78/min | BMI 29.4 kg/m² | RBS 268 mg/dL"),
        ],
        "presenting_complaint": "Polyuria, polydipsia, and fatigue for 2 months. Incidental high blood sugar on screening.",
        "history": [
            "Family history of T2DM (mother).",
            "No previous diagnosis of diabetes.",
            "HbA1c today: 8.9% | FPG: 214 mg/dL.",
            "Mild dyslipidaemia on previous lipid panel (LDL 148 mg/dL).",
            "No known drug allergies."
        ],
        "examination": [
            "Abdomen: soft, non-tender; no hepatomegaly.",
            "Peripheral sensation: intact bilaterally.",
            "Fundoscopy: no diabetic retinopathy.",
            "Foot exam: normal pulses, no ulcers."
        ],
        "diagnosis": "Type 2 Diabetes Mellitus (newly diagnosed) + Overweight",
        "prescription": [
            ("Metformin 500 mg", "500 mg – Oral", "BD (with meals)", "1 month then review"),
            ("Aspirin 75 mg", "75 mg – Oral", "OD (with breakfast)", "Long-term"),
            ("Atorvastatin 10 mg", "10 mg – Oral", "OD at bedtime", "Long-term"),
            ("Multivitamin + Chromium", "1 tab – Oral", "OD", "3 months"),
        ],
        "reasoning": [
            ("Metformin",
             "First-line oral hypoglycaemic agent for T2DM. Works by reducing hepatic glucose output (via AMPK activation) "
             "and improving peripheral insulin sensitivity. Weight-neutral, low hypoglycaemia risk, cardiovascular-safe, "
             "affordable. Start at 500 mg to minimise GI side effects; titrate to 1000 mg BD after 4 weeks if tolerated."),
            ("Aspirin 75 mg",
             "Low-dose aspirin for primary cardiovascular prevention in a diabetic patient with multiple CV risk factors "
             "(age, female sex, dyslipidaemia, overweight). Inhibits COX-1-mediated thromboxane A2 production, "
             "reducing platelet aggregation."),
            ("Atorvastatin",
             "All diabetic patients have elevated CV risk and benefit from statin therapy regardless of baseline LDL. "
             "Atorvastatin inhibits HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptors. "
             "Bedtime dosing aligns with peak hepatic cholesterol synthesis (overnight)."),
            ("Multivitamin + Chromium",
             "Chromium potentiates insulin receptor signalling. Diabetes increases micronutrient turnover. "
             "Supportive role; not a substitute for pharmacological therapy."),
        ],
        "antibiotics_note": None,
        "follow_up": "Review in 4 weeks: FPG, symptoms; up-titrate Metformin. HbA1c at 3 months. "
                     "Annual fundoscopy, urine microalbumin, and foot exam.",
    },

    # ── CASE 3 ──────────────────────────────────────────────────────────────
    {
        "num": 3,
        "title": "Hypertension – Stage 1 (Newly Diagnosed)",
        "patient": [
            ("Name", "Mr. Anil Kapoor"),
            ("Age / Sex", "48 years / Male"),
            ("Occupation", "Software Engineer"),
            ("Vitals", "BP 154/96 mmHg (confirmed on 3 separate visits) | HR 76/min | BMI 27.1 kg/m²"),
        ],
        "presenting_complaint": "Occasional headaches and dizziness. BP elevated on routine check.",
        "history": [
            "No DM, no dyslipidaemia.",
            "Smokes 5-6 cigarettes/day; sedentary lifestyle.",
            "No organ damage on ECG and renal function.",
            "No known drug allergies."
        ],
        "examination": [
            "Cardiovascular: normal heart sounds, no murmurs.",
            "Fundoscopy: grade 1 hypertensive retinopathy (arteriolar narrowing).",
            "Kidney function, electrolytes: normal.",
            "ECG: normal sinus rhythm, no LVH."
        ],
        "diagnosis": "Essential Hypertension – Stage 1 (no compelling indication)",
        "prescription": [
            ("Amlodipine 5 mg", "5 mg – Oral", "OD (morning)", "1 month then review"),
            ("Aspirin 75 mg", "75 mg – Oral", "OD (with food)", "Long-term"),
            ("Lifestyle counselling", "—", "Ongoing", "Lifelong"),
        ],
        "reasoning": [
            ("Amlodipine",
             "Dihydropyridine calcium channel blocker (CCB). First-line for hypertension especially in non-diabetic patients "
             "without compelling indications. Relaxes vascular smooth muscle by blocking L-type Ca²⁺ channels, reducing "
             "peripheral vascular resistance. Long half-life (30-50 h) allows OD dosing and avoids BP fluctuations. "
             "Preferred over beta-blockers as first-line in absence of heart failure, post-MI, or tachyarrhythmia."),
            ("Aspirin 75 mg",
             "CV risk reduction in hypertensive male smoker aged 48. Only given after BP partially controlled "
             "(to avoid haemorrhagic stroke risk at high BP). Irreversibly inhibits COX-1 platelets for their lifespan."),
            ("Lifestyle counselling",
             "DASH diet (restrict Na⁺ <2.3 g/day, increase K⁺, Mg²⁺), aerobic exercise 30 min/day × 5 days/week, "
             "smoking cessation, weight reduction. Lifestyle changes can reduce SBP by 5-15 mmHg and may avoid or delay "
             "need for additional medications."),
        ],
        "antibiotics_note": None,
        "follow_up": "Recheck BP in 4 weeks. If BP not at goal (<130/80 mmHg), add ACE inhibitor (Enalapril 5 mg OD). "
                     "Annual labs: serum creatinine, electrolytes, lipids.",
    },

    # ── CASE 4 ──────────────────────────────────────────────────────────────
    {
        "num": 4,
        "title": "Acute Gastroenteritis (Probable Viral)",
        "patient": [
            ("Name", "Master Arjun Singh"),
            ("Age / Sex", "8 years / Male"),
            ("Weight", "24 kg"),
            ("Vitals", "BP 96/62 mmHg | HR 106/min | Temp 37.8°C | No dehydration signs"),
        ],
        "presenting_complaint": "Watery diarrhoea (5-6 episodes/day) and vomiting (3 episodes) for 1 day. Mild abdominal cramps.",
        "history": [
            "Ate street food the previous day. Sibling at home with similar symptoms.",
            "Fully vaccinated (Rotavirus given at 6 and 10 weeks).",
            "No blood in stool, no high fever.",
            "No known drug allergies."
        ],
        "examination": [
            "Abdomen: soft, mildly tender periumbilically, no guarding.",
            "Hydration: moist mucosae, good capillary refill (<2 sec), skin turgor normal.",
            "Stool exam: no RBCs or pus cells; Rotavirus antigen: positive."
        ],
        "diagnosis": "Acute Viral Gastroenteritis (Rotavirus) – No dehydration",
        "prescription": [
            ("ORS (WHO-recommended)", "75 mL/kg over 4 h, then 10 mL/kg per loose stool", "After each loose stool", "Until diarrhoea stops"),
            ("Zinc 20 mg", "20 mg – Oral", "OD", "14 days"),
            ("Ondansetron 2 mg", "2 mg – Oral (dissolve on tongue)", "Q8H (if vomiting)", "3 days"),
            ("Probiotics (Lactobacillus rhamnosus GG)", "1 sachet – Oral", "BD", "5 days"),
        ],
        "reasoning": [
            ("ORS",
             "Cornerstone of gastroenteritis management. WHO low-osmolarity ORS (Na 75 mEq/L, Glucose 75 mmol/L) "
             "exploits glucose-sodium co-transport in the gut to replenish fluid and electrolytes. Reduces stool output "
             "by 25% vs. standard ORS. Prevents dehydration and avoids IV fluids."),
            ("Zinc 20 mg",
             "WHO & UNICEF recommendation for all children with diarrhoea. Zinc reduces duration of diarrhoea by ~25% "
             "and severity by ~30%. Mechanism: maintains intestinal epithelial integrity, enhances immune function, "
             "supports mucosal repair. Continue for 14 days to replenish body stores."),
            ("Ondansetron",
             "5-HT3 receptor antagonist. Reduces vomiting, improving oral fluid retention. "
             "Evidence supports single/short-course use in paediatric gastroenteritis; avoids IV rehydration admission. "
             "Weight-based dose: 0.1-0.15 mg/kg per dose; max 4 mg in children."),
            ("Probiotics (LGG)",
             "Best-evidenced probiotic strain for acute viral gastroenteritis. Competes with pathogens for colonisation, "
             "modulates immune response, reduces diarrhoea duration by approximately 1 day. Safe and well-tolerated."),
        ],
        "antibiotics_note": "NO antibiotics – Viral aetiology confirmed. Antibiotics do not treat viral diarrhoea "
                            "and increase risk of antibiotic-associated diarrhoea and resistance.",
        "follow_up": "Return immediately if signs of dehydration (sunken eyes, dry tongue, decreased urine output) "
                     "or blood in stool appear. Otherwise review in 48 hours.",
    },

    # ── CASE 5 ──────────────────────────────────────────────────────────────
    {
        "num": 5,
        "title": "Bronchial Asthma – Mild Persistent (Step 2)",
        "patient": [
            ("Name", "Ms. Priya Nair"),
            ("Age / Sex", "22 years / Female"),
            ("Occupation", "College Student"),
            ("Vitals", "BP 110/70 mmHg | HR 88/min | RR 18/min | SpO₂ 97% | Peak Flow: 72% predicted"),
        ],
        "presenting_complaint": "Recurrent episodes of wheeze, chest tightness, and shortness of breath – especially at night and during exercise.",
        "history": [
            "Symptoms >2 days/week but not daily; nighttime symptoms 2-3 times/month.",
            "Family history of atopy (mother: allergic rhinitis).",
            "No hospital admissions; no oral steroids required previously.",
            "No known drug allergies. Non-smoker."
        ],
        "examination": [
            "Chest: bilateral expiratory wheeze on auscultation.",
            "No use of accessory muscles, no cyanosis.",
            "Spirometry: FEV1/FVC 71% (obstructive pattern); FEV1 reversibility +15% post-salbutamol.",
        ],
        "diagnosis": "Bronchial Asthma – Mild Persistent (GINA Step 2)",
        "prescription": [
            ("Salbutamol MDI 100 mcg", "2 puffs (200 mcg) – Inhaled", "PRN (rescue)", "Ongoing"),
            ("Budesonide MDI 200 mcg", "1 puff (200 mcg) – Inhaled", "BD (controller)", "3 months min"),
            ("Montelukast 10 mg", "10 mg – Oral", "OD at bedtime", "3 months"),
            ("Spacer device", "Use with all MDIs", "Every dose", "Ongoing"),
        ],
        "reasoning": [
            ("Salbutamol (SABA)",
             "Short-Acting Beta-2 Agonist. Relieves acute bronchospasm by activating beta-2 receptors on bronchial "
             "smooth muscle, causing cAMP-mediated relaxation within minutes. Used PRN as rescue; not for regular scheduled use alone "
             "(increases risk of poor control if used >2 days/week without controller therapy)."),
            ("Budesonide (ICS)",
             "Inhaled Corticosteroid – preferred controller for Step 2 asthma (GINA guidelines). "
             "Reduces airway inflammation, decreases mucus production, and lowers bronchial hyper-responsiveness. "
             "Low systemic bioavailability minimises side effects. Must be taken daily even when asymptomatic."),
            ("Montelukast (LTRA)",
             "Leukotriene Receptor Antagonist. Add-on therapy for exercise-induced or allergic asthma. "
             "Blocks CysLT1 receptors, preventing leukotriene D4-mediated bronchoconstriction and mucus secretion. "
             "Also reduces concomitant allergic rhinitis symptoms. Bedtime dosing targets nocturnal symptoms."),
            ("Spacer device",
             "Reduces oropharyngeal deposition of inhaled drug, improves lung delivery, and reduces ICS-related "
             "oral candidiasis risk. Essential for correct MDI technique – increases drug delivery to lungs by 30-50%."),
        ],
        "antibiotics_note": None,
        "follow_up": "Assess symptom control and inhaler technique at 4 weeks. "
                     "Step up to GINA Step 3 (ICS/LABA combination) if control inadequate after 3 months.",
    },

    # ── CASE 6 ──────────────────────────────────────────────────────────────
    {
        "num": 6,
        "title": "Urinary Tract Infection (Uncomplicated Cystitis in Female)",
        "patient": [
            ("Name", "Mrs. Kavitha Reddy"),
            ("Age / Sex", "29 years / Female"),
            ("Occupation", "Nurse"),
            ("Vitals", "BP 116/74 mmHg | HR 80/min | Temp 37.4°C | No CVA tenderness"),
        ],
        "presenting_complaint": "Burning micturition, increased urinary frequency, and lower abdominal discomfort for 2 days. No fever. No flank pain.",
        "history": [
            "Second episode this year; previous UTI treated with Nitrofurantoin (resolved fully).",
            "Not pregnant (urine hCG negative).",
            "No DM, no immunosuppression.",
            "No known drug allergies."
        ],
        "examination": [
            "Suprapubic tenderness: mild.",
            "No costovertebral angle tenderness.",
            "Urine dipstick: Leucocytes ++, Nitrites + , Blood trace.",
            "Urine C&S sent (empirical treatment started)."
        ],
        "diagnosis": "Uncomplicated Urinary Tract Infection (Cystitis)",
        "prescription": [
            ("Nitrofurantoin 100 mg MR", "100 mg – Oral", "BD (with food)", "5 days"),
            ("Phenazopyridine 100 mg", "100 mg – Oral", "TDS (after meals)", "2 days only"),
            ("Cranberry extract 400 mg", "400 mg – Oral", "OD", "1 month (prophylaxis)"),
            ("Adequate fluid intake (>2 L/day)", "—", "Throughout day", "Ongoing"),
        ],
        "reasoning": [
            ("Nitrofurantoin MR",
             "First-line antibiotic for uncomplicated UTI in non-pregnant women. Active against most E. coli and Staphylococcus saprophyticus – the commonest uropathogens. "
             "Mechanism: reduced to reactive intermediates by bacterial reductases, damaging DNA, ribosomes, and cell-wall synthesis. "
             "Achieves high urinary concentrations; minimal GI flora disruption. MR formulation improves tolerability. "
             "Preferred over fluoroquinolones to preserve broad-spectrum agents."),
            ("Phenazopyridine",
             "Urinary analgesic/anaesthetic dye. Provides rapid relief of dysuria, urgency, and frequency by exerting local "
             "anaesthetic effect on urothelium. NOTE: Not an antibiotic – use for ≤2 days only. "
             "Warn patient: urine turns orange-red (harmless but may stain clothing)."),
            ("Cranberry extract",
             "Proanthocyanidins in cranberry inhibit P-fimbriae of E. coli from adhering to uroepithelial cells. "
             "Evidence supports modest reduction in recurrent UTI frequency. Appropriate for a patient with recurrent infections."),
            ("Fluid intake",
             "Flushing effect helps physically remove bacteria from urethra and bladder. Dilutes urine, reducing irritation. "
             "Reduces bacterial load in bladder."),
        ],
        "antibiotics_note": "ANTIBIOTIC NOTE: Review C&S result in 48-72 h – adjust if necessary. "
                            "Fluoroquinolones (e.g. ciprofloxacin) are AVOIDED as first-line due to growing resistance and collateral damage.",
        "follow_up": "Review C&S in 48-72 h. Repeat urine dipstick at 1 week post-treatment. "
                     "If ≥3 UTIs/year, discuss long-term low-dose prophylaxis.",
    },

    # ── CASE 7 ──────────────────────────────────────────────────────────────
    {
        "num": 7,
        "title": "Iron Deficiency Anaemia",
        "patient": [
            ("Name", "Mrs. Fatima Sheikh"),
            ("Age / Sex", "31 years / Female"),
            ("Occupation", "Garment Worker"),
            ("Vitals", "BP 108/68 mmHg | HR 96/min | Pallor: moderate | Koilonychia present"),
        ],
        "presenting_complaint": "Fatigue, palpitations, shortness of breath on exertion, and brittle nails for 3 months.",
        "history": [
            "Heavy menstrual bleeding (menorrhagia) for 6+ months.",
            "Poor dietary iron intake (vegetarian, low pulse consumption).",
            "Hb: 7.8 g/dL | MCV: 64 fL | MCH: 19 pg | Serum ferritin: 6 ng/mL | TIBC: elevated.",
            "No GI bleeding symptoms. No prior anaemia treatment."
        ],
        "examination": [
            "Pallor: conjunctival, palmar.",
            "Koilonychia (spoon-shaped nails) present.",
            "Mild tachycardia; no cardiac murmurs.",
            "No hepatosplenomegaly."
        ],
        "diagnosis": "Iron Deficiency Anaemia (secondary to menorrhagia + dietary deficiency)",
        "prescription": [
            ("Ferrous sulphate 200 mg", "200 mg elemental Fe 60 mg – Oral", "TDS (before meals)", "3-6 months"),
            ("Vitamin C (Ascorbic acid) 500 mg", "500 mg – Oral", "TDS (with iron dose)", "3-6 months"),
            ("Folic acid 5 mg", "5 mg – Oral", "OD", "3 months"),
            ("Tranexamic acid 500 mg", "500 mg – Oral", "TDS during menstruation", "Each cycle"),
        ],
        "reasoning": [
            ("Ferrous sulphate",
             "Replaces depleted iron stores. Iron is essential for haemoglobin synthesis and mitochondrial electron transport. "
             "Ferrous (Fe²⁺) form has superior GI absorption (~10-20%) vs ferric (Fe³⁺). "
             "Pre-meal dosing maximises absorption (less interference from phytates/calcium) but TDS on empty stomach "
             "may cause GI upset – adjust timing if needed. Target: Hb rise of 1 g/dL per week."),
            ("Vitamin C",
             "Ascorbic acid reduces Fe³⁺ → Fe²⁺ in the gut, maintaining iron in the absorbable form. Also chelates iron "
             "in a soluble complex that resists precipitation at alkaline duodenal pH. Co-administration can increase "
             "iron absorption by 2-3 fold."),
            ("Folic acid",
             "Co-existing nutritional deficiency common in menorrhagic women with poor diet. Folic acid required for "
             "DNA synthesis and RBC maturation (megaloblastic component may co-exist with IDA). Prevents neural tube "
             "defects if patient becomes pregnant."),
            ("Tranexamic acid",
             "Antifibrinolytic agent. Inhibits plasminogen activators, preventing clot dissolution. Reduces menstrual blood "
             "loss by 30-58% in menorrhagia. Addresses the root cause of iron loss. Taken only during menstruation, "
             "limiting systemic thromboembolic risk."),
        ],
        "antibiotics_note": None,
        "follow_up": "Recheck Hb and ferritin at 4 weeks. Continue iron for 3 months after Hb normalises (to replenish stores). "
                     "Refer to gynaecology if menorrhagia persists.",
    },

    # ── CASE 8 ──────────────────────────────────────────────────────────────
    {
        "num": 8,
        "title": "Peptic Ulcer Disease / Gastritis (H. pylori Positive)",
        "patient": [
            ("Name", "Mr. Deepak Mehta"),
            ("Age / Sex", "44 years / Male"),
            ("Occupation", "Journalist"),
            ("Vitals", "BP 122/78 mmHg | HR 74/min | Temp 36.8°C | No haematemesis"),
        ],
        "presenting_complaint": "Epigastric pain (burning, worse on empty stomach, relieved by food), nausea, and bloating for 6 weeks.",
        "history": [
            "Regular NSAID use (Ibuprofen 400 mg TDS for chronic back pain).",
            "Smokes 10 cigarettes/day; drinks 2-3 cups of coffee daily.",
            "H. pylori rapid urease test (RUT) on endoscopy: POSITIVE.",
            "OGD findings: duodenal ulcer 0.8 cm with no active bleeding."
        ],
        "examination": [
            "Abdomen: epigastric tenderness on deep palpation.",
            "No peritoneal signs, no guarding.",
            "No pallor, no melaena on rectal exam."
        ],
        "diagnosis": "H. pylori-positive Peptic Ulcer Disease (Duodenal Ulcer)",
        "prescription": [
            ("Omeprazole 20 mg", "20 mg – Oral", "BD (before meals)", "14 days then OD × 4 wks"),
            ("Clarithromycin 500 mg", "500 mg – Oral", "BD", "14 days"),
            ("Amoxicillin 1000 mg", "1000 mg – Oral", "BD", "14 days"),
            ("Sucralfate 1 g", "1 g – Oral", "QID (1 h before meals + HS)", "4 weeks"),
        ],
        "reasoning": [
            ("Omeprazole (PPI)",
             "Proton Pump Inhibitor – irreversibly inhibits H⁺/K⁺-ATPase on parietal cells, reducing gastric acid by >90%. "
             "Creates alkaline environment essential for antibiotic efficacy against H. pylori (antibiotics are pH-sensitive). "
             "Also promotes ulcer healing by reducing acid-mediated mucosal injury. BD dosing during eradication therapy; "
             "reduce to OD for 4 weeks post-eradication for ulcer healing."),
            ("Clarithromycin + Amoxicillin (Triple Therapy)",
             "Standard first-line H. pylori eradication regimen (OAC: Omeprazole + Amoxicillin + Clarithromycin). "
             "Clarithromycin (macrolide): inhibits 50S ribosomal subunit, blocking protein synthesis. "
             "Amoxicillin (beta-lactam): inhibits transpeptidase, disrupting cell wall synthesis. "
             "Together they achieve eradication rates of 70-85%. Dual antibiotic coverage prevents resistance."),
            ("Sucralfate",
             "Cytoprotective agent. At low pH, polymerises to form a viscous paste that adheres selectively to ulcer base, "
             "acting as a physical barrier against acid and pepsin. Also stimulates prostaglandin and mucus production. "
             "Use for 4 weeks adjunct to PPI for ulcer base healing."),
        ],
        "antibiotics_note": "NSAID CESSATION: Ibuprofen MUST be stopped. NSAIDs inhibit COX-1, reducing cytoprotective "
                            "prostaglandins in gastric mucosa. Switch back pain management to Paracetamol or discuss with orthopaedics.",
        "follow_up": "H. pylori eradication confirmation (urea breath test or stool antigen) 4 weeks after antibiotics completion. "
                     "Smoking cessation strongly advised. Repeat OGD in 8 weeks if large ulcer or alarm symptoms.",
    },

    # ── CASE 9 ──────────────────────────────────────────────────────────────
    {
        "num": 9,
        "title": "Hypothyroidism (Newly Diagnosed Overt)",
        "patient": [
            ("Name", "Mrs. Rohini Das"),
            ("Age / Sex", "38 years / Female"),
            ("Occupation", "Accountant"),
            ("Vitals", "BP 124/82 mmHg | HR 58/min | BMI 31.2 kg/m² | Temp 36.1°C"),
        ],
        "presenting_complaint": "Weight gain (8 kg over 6 months), fatigue, constipation, dry skin, cold intolerance, and hair loss.",
        "history": [
            "TSH: 48.2 mIU/L (↑) | Free T4: 0.52 ng/dL (↓) | Anti-TPO antibodies: 420 IU/mL (↑).",
            "Family history: mother has Hashimoto's thyroiditis.",
            "No cardiac disease.",
            "No known drug allergies. Not pregnant."
        ],
        "examination": [
            "Thyroid: diffuse, firm, non-tender goitre (Grade 1).",
            "Skin: dry, coarse; non-pitting oedema in pretibial region.",
            "Reflexes: delayed relaxation phase (hung-up reflexes).",
            "ECG: sinus bradycardia, low-voltage QRS."
        ],
        "diagnosis": "Overt Primary Hypothyroidism – Hashimoto's Thyroiditis",
        "prescription": [
            ("Levothyroxine (T4) 50 mcg", "50 mcg – Oral", "OD (fasting, 30 min before breakfast)", "Lifelong"),
            ("Calcium / Vitamin D supplement", "500 mg Ca + 400 IU Vit D – Oral", "OD (4 h after Levothyroxine)", "Ongoing"),
        ],
        "reasoning": [
            ("Levothyroxine",
             "Synthetic T4 (thyroxine) – replaces deficient thyroid hormone. Converted peripherally to active T3 by "
             "deiodinases. Starting dose 50 mcg is cautious in a 38-year-old (avoids precipitating angina or arrhythmia). "
             "Titrate by 12.5-25 mcg every 6-8 weeks targeting TSH 0.5-2.5 mIU/L. "
             "Fasting morning administration critical: food (especially calcium, iron, fibre) significantly reduces "
             "LT4 absorption by up to 40%. Treatment is lifelong in Hashimoto's."),
            ("Calcium + Vitamin D",
             "Autoimmune thyroid disease is associated with other autoimmune conditions including hypocalcaemia risk. "
             "Calcium must be taken ≥4 hours after LT4 to avoid chelation and absorption interference. "
             "Vitamin D deficiency is prevalent in hypothyroid patients and can worsen autoimmune activity."),
        ],
        "antibiotics_note": "IMPORTANT INTERACTIONS: Avoid concurrent iron supplements, antacids, calcium within 4 h of LT4. "
                            "Amiodarone, rifampicin, and oestrogen alter T4 metabolism – review if added.",
        "follow_up": "Recheck TSH and free T4 at 6-8 weeks. Titrate dose. Annual TFTs once stable. "
                     "Screen for associated autoimmune conditions (coeliac disease, T1DM, vitiligo).",
    },

    # ── CASE 10 ─────────────────────────────────────────────────────────────
    {
        "num": 10,
        "title": "Acute Bacterial Tonsillitis (Group A Streptococcal)",
        "patient": [
            ("Name", "Miss Sana Qureshi"),
            ("Age / Sex", "16 years / Female"),
            ("Occupation", "School Student"),
            ("Vitals", "BP 108/70 mmHg | HR 98/min | Temp 38.9°C | Centor Score: 4/4"),
        ],
        "presenting_complaint": "Severe sore throat, high fever, and difficulty swallowing for 3 days. No cough.",
        "history": [
            "Centor criteria: exudate on tonsils, anterior cervical lymphadenopathy, fever >38°C, no cough (score 4).",
            "Rapid antigen test (RADT) for Group A Streptococcus: POSITIVE.",
            "No penicillin allergy. First episode.",
            "No rheumatic fever history."
        ],
        "examination": [
            "Throat: bilateral tonsillar enlargement with white exudate.",
            "Cervical lymph nodes: tender, enlarged bilaterally (anterior chain).",
            "No peritonsillar swelling/abscess.",
            "No rash (ruling out scarlet fever)."
        ],
        "diagnosis": "Acute Group A Streptococcal Tonsillitis",
        "prescription": [
            ("Phenoxymethylpenicillin (Pen V) 500 mg", "500 mg – Oral", "QID (every 6 h)", "10 days"),
            ("Paracetamol 500 mg", "500-1000 mg – Oral", "QID PRN", "5-7 days"),
            ("Ibuprofen 400 mg", "400 mg – Oral", "TDS (with food)", "3-5 days"),
            ("Chlorhexidine / Benzydamine gargle", "10 mL – Gargle", "TDS", "5 days"),
        ],
        "reasoning": [
            ("Phenoxymethylpenicillin (Penicillin V)",
             "Drug of choice for Group A Streptococcal pharyngitis/tonsillitis. "
             "Beta-lactam: inhibits transpeptidase, blocking peptidoglycan cross-linking in bacterial cell wall – bactericidal. "
             "GAS remains uniformly sensitive to penicillin (no resistance documented). "
             "10-day course essential to eradicate pharyngeal carriage and prevent: (1) rheumatic fever, (2) post-streptococcal "
             "glomerulonephritis, (3) peritonsillar abscess. Shorter courses are associated with higher relapse rates."),
            ("Paracetamol",
             "Antipyretic and analgesic via central prostaglandin inhibition and activation of descending serotonergic pathways. "
             "Reduces fever and throat pain. Safe, hepatic metabolism. Maximum 4 g/day in adults; avoid in liver disease."),
            ("Ibuprofen",
             "NSAID – inhibits COX-1 and COX-2, reducing prostaglandin synthesis. Provides superior anti-inflammatory and "
             "analgesic effect compared to paracetamol alone for exudative tonsillitis. Combination with paracetamol (alternating) "
             "provides superior analgesia. Taken with food to prevent gastric irritation."),
            ("Chlorhexidine / Benzydamine gargle",
             "Topical antiseptic (chlorhexidine) reduces bacterial load in oropharynx. Benzydamine is a topical NSAID/local "
             "anaesthetic that reduces mucosal inflammation and pain on swallowing. Adjunct to systemic therapy."),
        ],
        "antibiotics_note": "PENICILLIN ALLERGY ALTERNATIVE: If allergic to penicillin, use Azithromycin 500 mg OD × 5 days "
                            "or Clarithromycin 250 mg BD × 10 days. Avoid cephalosporins in anaphylaxis history.",
        "follow_up": "Review at 48-72 h if no improvement. Complete full 10-day course even if feeling better. "
                     "Refer to ENT if ≥7 episodes/year (tonsillectomy criteria).",
    },
]

# ══════════════════════════════════════════════════════════════════════════════
# BUILD STORY (PDF flowable elements)
# ══════════════════════════════════════════════════════════════════════════════

story = []

# ── Cover page ────────────────────────────────────────────────────────────────
def cover_page():
    elems = []
    # full-width coloured block
    banner = ColourBanner(NAVY, height=6*cm, radius=0)
    elems.append(banner)
    elems.append(Spacer(1, -5.5*cm))  # overlap

    # white hospital icon placeholder text
    cover_tbl = Table(
        [[Paragraph("OPD PATIENT CASES", sTitle)],
         [Paragraph("Educational Prescriptions & Clinical Reasoning", sSubTitle)],
         [Spacer(1, 0.4*cm)],
         [Paragraph("For Medical Students, Interns & Residents", sSubTitle)],
         [Spacer(1, 0.3*cm)],
         [Paragraph(f"Compiled: {datetime.date.today().strftime('%B %Y')}", sDate)],
        ],
        colWidths=[15.7*cm]
    )
    cover_tbl.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), NAVY),
        ("TOPPADDING",    (0,0), (-1,-1), 8),
        ("BOTTOMPADDING", (0,0), (-1,-1), 8),
        ("LEFTPADDING",   (0,0), (-1,-1), 20),
        ("RIGHTPADDING",  (0,0), (-1,-1), 20),
    ]))
    elems.append(cover_tbl)
    elems.append(Spacer(1, 1*cm))

    # summary box
    sum_data = [
        [Paragraph("<b>10</b>", ParagraphStyle("big", fontSize=28, textColor=TEAL, fontName="Helvetica-Bold", alignment=TA_CENTER)),
         Paragraph("<b>Specialties</b><br/>covered", ParagraphStyle("sm", fontSize=10, textColor=NAVY, fontName="Helvetica", alignment=TA_CENTER, leading=14))],
        [Paragraph("<b>40+</b>", ParagraphStyle("big2", fontSize=28, textColor=GOLD, fontName="Helvetica-Bold", alignment=TA_CENTER)),
         Paragraph("<b>Drug explanations</b><br/>with mechanisms", ParagraphStyle("sm2", fontSize=10, textColor=NAVY, fontName="Helvetica", alignment=TA_CENTER, leading=14))],
    ]
    sum_tbl = Table(sum_data, colWidths=[4*cm, 7*cm])
    sum_tbl.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), LIGHT_TEAL),
        ("ALIGN", (0,0), (-1,-1), "CENTER"),
        ("VALIGN", (0,0), (-1,-1), "MIDDLE"),
        ("TOPPADDING", (0,0), (-1,-1), 14),
        ("BOTTOMPADDING", (0,0), (-1,-1), 14),
        ("ROUNDEDCORNERS", [10]),
        ("GRID", (0,0), (-1,-1), 0.3, MID_GREY),
    ]))
    elems.append(sum_tbl)
    elems.append(Spacer(1, 0.8*cm))

    # Disclaimer
    disc_style = ParagraphStyle("disc", fontSize=8, textColor=HexColor("#7f8c8d"),
                                fontName="Helvetica-Oblique", alignment=TA_CENTER, leading=12)
    elems.append(Paragraph(
        "DISCLAIMER: This document is created solely for educational purposes. "
        "Prescriptions are illustrative and should not be used as direct clinical instructions. "
        "Always refer to current local guidelines and consult a qualified clinician.",
        disc_style
    ))
    elems.append(PageBreak())
    return elems

story += cover_page()

# ── TOC ───────────────────────────────────────────────────────────────────────
story.append(Paragraph("Table of Contents", ParagraphStyle(
    "toc_h", fontSize=16, textColor=NAVY, fontName="Helvetica-Bold", spaceAfter=12
)))
story.append(hr(TEAL, 1.5))
story.append(gap(0.3))

toc_items = [(f"Case {c['num']}", c['title'], c['diagnosis']) for c in CASES]
for num, title, diag in toc_items:
    row = Table(
        [[Paragraph(f"<b>{num}</b>", sTocEntry),
          Paragraph(title, sTocEntry),
          Paragraph(f"<i>{diag}</i>", ParagraphStyle("tocDiag", fontSize=9, textColor=HexColor("#7f8c8d"),
                                                      fontName="Helvetica-Oblique"))]],
        colWidths=[2*cm, 9*cm, 5*cm]
    )
    row.setStyle(TableStyle([
        ("VALIGN", (0,0), (-1,-1), "TOP"),
        ("TOPPADDING", (0,0), (-1,-1), 5),
        ("BOTTOMPADDING", (0,0), (-1,-1), 5),
        ("LINEBELOW", (0,0), (-1,-1), 0.3, MID_GREY),
    ]))
    story.append(row)

story.append(PageBreak())

# ── Cases ─────────────────────────────────────────────────────────────────────
for case in CASES:
    # Header
    story += case_header(case["num"], case["title"])
    story.append(gap(0.35))

    # Diagnosis badge
    diag_tbl = Table(
        [[Paragraph("DIAGNOSIS:", ParagraphStyle("db", fontSize=9, fontName="Helvetica-Bold",
                                                  textColor=WHITE)),
          Paragraph(case["diagnosis"], ParagraphStyle("dv", fontSize=9, fontName="Helvetica",
                                                       textColor=WHITE))]],
        colWidths=[2.8*cm, 12.9*cm]
    )
    diag_tbl.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), TEAL),
        ("TOPPADDING", (0,0), (-1,-1), 5),
        ("BOTTOMPADDING", (0,0), (-1,-1), 5),
        ("LEFTPADDING", (0,0), (-1,-1), 8),
        ("ROUNDEDCORNERS", [6]),
    ]))
    story.append(diag_tbl)
    story.append(gap(0.3))

    # Patient info
    story.append(section_label("PATIENT INFORMATION"))
    story.append(info_table(case["patient"]))
    story.append(gap(0.3))

    # Presenting complaint
    story.append(section_label("PRESENTING COMPLAINT"))
    story.append(body(case["presenting_complaint"]))
    story.append(gap(0.15))

    # History
    story.append(section_label("HISTORY"))
    for h in case["history"]:
        story.append(bullet(h))
    story.append(gap(0.15))

    # Examination
    story.append(section_label("EXAMINATION FINDINGS"))
    for e in case["examination"]:
        story.append(bullet(e))
    story.append(gap(0.25))

    # Prescription
    story.append(section_label("PRESCRIPTION"))
    story.append(prescription_table(case["prescription"]))
    story.append(gap(0.3))

    # Reasoning
    story.append(section_label("CLINICAL REASONING – WHY THIS PRESCRIPTION?"))
    for drug, rationale in case["reasoning"]:
        story.append(body(f"<b>{drug}</b>"))
        story.append(reason(rationale))
        story.append(gap(0.1))

    # Antibiotic note
    if case.get("antibiotics_note"):
        story.append(gap(0.1))
        if "NO antibiotic" in case["antibiotics_note"] or "NO antibiotics" in case["antibiotics_note"]:
            story.append(ok(case["antibiotics_note"]))
        else:
            story.append(warn(case["antibiotics_note"]))

    # Follow-up
    story.append(gap(0.2))
    f_bg = Table(
        [[Paragraph("FOLLOW-UP:", ParagraphStyle("fup_l", fontSize=9, fontName="Helvetica-Bold",
                                                  textColor=NAVY)),
          Paragraph(case["follow_up"], ParagraphStyle("fup_v", fontSize=9, fontName="Helvetica",
                                                       textColor=HexColor("#2c3e50")))]],
        colWidths=[2.8*cm, 12.9*cm]
    )
    f_bg.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), LIGHT_GOLD),
        ("TOPPADDING", (0,0), (-1,-1), 6),
        ("BOTTOMPADDING", (0,0), (-1,-1), 6),
        ("LEFTPADDING", (0,0), (-1,-1), 8),
        ("VALIGN", (0,0), (-1,-1), "TOP"),
        ("ROUNDEDCORNERS", [6]),
    ]))
    story.append(f_bg)
    story.append(gap(0.4))
    story.append(hr(MID_GREY))
    story.append(PageBreak())

# ── Back matter: quick reference ─────────────────────────────────────────────
story.append(Paragraph("Quick Reference – Drug Class Summary",
    ParagraphStyle("qr_h", fontSize=15, textColor=NAVY, fontName="Helvetica-Bold", spaceAfter=8)))
story.append(hr(TEAL, 1.5))
story.append(gap(0.3))

qr_data = [
    ["Drug Class", "Key Mechanism", "Representative Drug", "Common Use"],
    ["Analgesic/Antipyretic", "Central PG inhibition", "Paracetamol", "Pain, fever"],
    ["2nd-gen Antihistamine", "H1 receptor block", "Cetirizine", "Allergic rhinitis, urticaria"],
    ["Biguanide", "AMPK activation, ↓ hepatic glucose output", "Metformin", "T2DM first-line"],
    ["CCB (Dihydropyridine)", "L-type Ca²⁺ channel block", "Amlodipine", "Hypertension, angina"],
    ["ORS / Zinc", "Na-glucose co-transport / epithelial repair", "WHO-ORS + Zinc", "Diarrhoea / dehydration"],
    ["SABA", "Beta-2 receptor agonist (cAMP)", "Salbutamol", "Acute bronchospasm"],
    ["ICS", "Anti-inflammatory (GR-mediated)", "Budesonide", "Asthma controller"],
    ["Antibiotic – Nitrofurantoin", "DNA/ribosome damage via reductase", "Nitrofurantoin MR", "Uncomplicated UTI"],
    ["Iron supplement", "Replaces Fe stores → Hb synthesis", "Ferrous sulphate", "IDA"],
    ["PPI", "H⁺/K⁺-ATPase inhibition", "Omeprazole", "PUD, GORD, H. pylori"],
    ["Thyroid hormone", "T4 → T3 peripheral conversion", "Levothyroxine", "Hypothyroidism"],
    ["Penicillin (narrow spectrum)", "Transpeptidase inhibition", "Phenoxymethylpenicillin", "GAS tonsillitis"],
    ["5-HT3 antagonist", "Blocks serotonin-mediated nausea arc", "Ondansetron", "N/V in gastroenteritis"],
    ["Antifibrinolytic", "Inhibits plasminogen activators", "Tranexamic acid", "Menorrhagia"],
    ["LTRA", "CysLT1 receptor block", "Montelukast", "Asthma, allergic rhinitis"],
]
qr_tbl = Table(qr_data, colWidths=[4*cm, 5.5*cm, 3.5*cm, 2.6*cm], repeatRows=1)
qr_tbl.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), NAVY),
    ("TEXTCOLOR", (0,0), (-1,0), WHITE),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 8.5),
    ("ALIGN", (0,0), (-1,0), "CENTER"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [WHITE, LIGHT_GREY]),
    ("GRID", (0,0), (-1,-1), 0.3, MID_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 5),
    ("BOTTOMPADDING", (0,0), (-1,-1), 5),
    ("LEFTPADDING", (0,0), (-1,-1), 6),
    ("VALIGN", (0,0), (-1,-1), "MIDDLE"),
]))
story.append(qr_tbl)
story.append(gap(0.5))
story.append(Paragraph(
    "This document is for educational use only. Drug doses and regimens may vary by local guidelines, "
    "patient weight, renal function, and comorbidities. Always verify with current references before clinical application.",
    sFooterNote
))

# ── Build ─────────────────────────────────────────────────────────────────────

def add_page_number(canvas, doc):
    canvas.saveState()
    canvas.setFont("Helvetica", 8)
    canvas.setFillColor(HexColor("#7f8c8d"))
    page_num = canvas.getPageNumber()
    canvas.drawCentredString(PAGE_W / 2, 1.2*cm, f"Page {page_num}")
    canvas.setStrokeColor(MID_GREY)
    canvas.setLineWidth(0.5)
    canvas.line(2*cm, 1.5*cm, PAGE_W - 2*cm, 1.5*cm)
    canvas.restoreState()

doc.build(story, onFirstPage=add_page_number, onLaterPages=add_page_number)
print(f"PDF created: {OUTPUT}")