#!/usr/bin/env python3
"""
GFR High-Yield MCQ Package for Batterjee Medical College Jeddah
Based on: Dr. Hader I. Sakr lecture (L.2-3) + Guyton & Hall 13e + Comprehensive Clinical Nephrology 7e
"""

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

# ─────────────────────────────────────────────────────────────────────────────
# COLOR PALETTE
# ─────────────────────────────────────────────────────────────────────────────
DARK_BLUE   = colors.HexColor('#1a237e')
MID_BLUE    = colors.HexColor('#1565c0')
LIGHT_BLUE  = colors.HexColor('#e3f2fd')
ACCENT_RED  = colors.HexColor('#b71c1c')
ACCENT_GRN  = colors.HexColor('#1b5e20')
HINT_YELLOW = colors.HexColor('#fff9c4')
HINT_BORDER = colors.HexColor('#f9a825')
ANSWER_BG   = colors.HexColor('#e8f5e9')
ANSWER_BDR  = colors.HexColor('#43a047')
WARN_ORANGE = colors.HexColor('#ff6f00')
HEADER_BG   = colors.HexColor('#0d47a1')
WHITE       = colors.white
LIGHT_GREY  = colors.HexColor('#f5f5f5')
CHEAT_BG    = colors.HexColor('#fffde7')
CHEAT_HDR   = colors.HexColor('#f57f17')
BORDER_GREY = colors.HexColor('#bdbdbd')

# ─────────────────────────────────────────────────────────────────────────────
# CONTENT
# ─────────────────────────────────────────────────────────────────────────────

MCQ_DATA = [
    # ── SECTION 1: GFR DEFINITION & NORMAL VALUES ──────────────────────────
    {
        "id": 1, "section": "GFR - Definition & Normal Values",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Physiology Exams 2019, 2021, 2022, 2023",
        "q": "What is the normal GFR in an average-sized adult male?",
        "options": [
            "A. 100 ml/min",
            "B. 125 ml/min",  # correct
            "C. 150 ml/min",
            "D. 112.5 ml/min",
            "E. 180 ml/min"
        ],
        "answer": "B",
        "hint": "GFR = 125 ml/min in males. Think: 7.5 L/h = 180 L/day = 60x plasma volume filtered daily.",
        "explanation": (
            "The GFR in an average-sized normal man is approximately 125 ml/min (Guyton & Hall 13e, Unit V). "
            "In women it is 10% less (~112.5 ml/min). This equals 7.5 L/hour or 180 L/day — about 60 times the "
            "total plasma volume. Since normal urine output is ~1 L/day, >99% of the filtrate is reabsorbed. "
            "Key fact: 20% of renal plasma flow (RPF ~625 ml/min) is filtered — this ratio is the FILTRATION FRACTION."
        ),
        "diagram_ref": "Starling forces diagram (see Diagram 1)"
    },
    {
        "id": 2, "section": "GFR - Definition & Normal Values",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Physiology Exam 2020, 2022",
        "q": "A patient with CKD has decreasing GFR but normal plasma creatinine. What is the most likely reason?",
        "options": [
            "A. Increased tubular secretion of creatinine",
            "B. Decreased muscle mass with age",  # correct
            "C. Increased protein intake",
            "D. Compensatory hyperfiltration",
            "E. Increased renal blood flow"
        ],
        "answer": "B",
        "hint": "GFR decreases with age, but plasma creatinine stays NORMAL because muscle mass also decreases (less creatinine produced).",
        "explanation": (
            "Creatinine is a metabolic byproduct of muscle. As GFR falls with age, muscle mass also decreases "
            "proportionally, so less creatinine is produced. This means plasma creatinine can remain in the 'normal' "
            "range even when GFR has significantly declined. This is clinically important — plasma creatinine is an "
            "insensitive early marker of kidney disease in the elderly. (Lecture slide, Dr. Sakr)"
        ),
        "diagram_ref": None
    },
    {
        "id": 3, "section": "GFR - Definition & Normal Values",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Physiology Exam 2021, 2023 (repeat)",
        "q": "The filtration fraction (FF) is defined as:",
        "options": [
            "A. GFR / RPF x 100",  # correct - but stated as ratio
            "B. RPF / GFR x 100",
            "C. GFR / RBF x 100",
            "D. RBF / RPF x 100",
            "E. GFR / Cardiac output x 100"
        ],
        "answer": "A",
        "hint": "FF = GFR/RPF. Normal FF = 125/625 = 20%. 'Fraction of PLASMA that is filtered.'",
        "explanation": (
            "The filtration fraction = GFR / RPF = 125 ml/min / 625 ml/min = 0.20 (20%). "
            "This means 20% of plasma entering the glomerular capillaries is filtered into Bowman's capsule. "
            "RBF is ~1250 ml/min (25% of cardiac output in an adult male at rest). RPF is approximately half of RBF "
            "because ~50% of blood is cells. (Guyton & Hall 13e, Harrison's 22e)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 2: STARLING FORCES ──────────────────────────────────────────
    {
        "id": 4, "section": "Starling Forces & GFR Equation",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Physiology Exams 2018, 2019, 2021, 2023 (core topic every year)",
        "q": "In the Starling equation for GFR, which force is the MOST IMPORTANT opposing filtration?",
        "options": [
            "A. Bowman's capsule hydrostatic pressure (18 mmHg)",
            "B. Glomerular capillary hydrostatic pressure (60 mmHg)",
            "C. Glomerular capillary colloid osmotic pressure (32 mmHg)",  # correct
            "D. Bowman's capsule colloid osmotic pressure (0 mmHg)",
            "E. Ultrafiltration coefficient (Kf)"
        ],
        "answer": "C",
        "hint": "The π(GC) = 32 mmHg is the BIGGEST opposing force. Remember: 60 - 18 - 32 = 10 mmHg net.",
        "explanation": (
            "The Starling equation: GFR = Kf [(HPgc - HPt) - (πgc - πt)]\n"
            "Forces FAVOURING filtration: HPgc = 60 mmHg, πt = 0 mmHg (no protein in Bowman's)\n"
            "Forces OPPOSING filtration: HPt = 18 mmHg, πgc = 32 mmHg\n"
            "Net filtration pressure = 60 - 18 - 32 = 10 mmHg\n"
            "The glomerular capillary oncotic pressure (πgc = 32 mmHg) is the single largest opposing force, "
            "and is the MOST IMPORTANT factor regulating GFR. Kf = GFR / net filtration pressure = 125/10 = 12.5 ml/min/mmHg. "
            "(Dr. Sakr lecture slides; Comprehensive Clinical Nephrology 7e, p.35)"
        ),
        "diagram_ref": "Diagram 1: Starling Forces"
    },
    {
        "id": 5, "section": "Starling Forces & GFR Equation",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Physiology Exam 2022, 2023",
        "q": "A patient has severe hypoproteinemia (e.g., nephrotic syndrome causing loss of plasma proteins). What happens to GFR?",
        "options": [
            "A. GFR decreases due to loss of Kf",
            "B. GFR increases due to decreased πgc",  # correct
            "C. GFR decreases due to increased HPt",
            "D. GFR remains unchanged due to autoregulation",
            "E. GFR decreases due to decreased HPgc"
        ],
        "answer": "B",
        "hint": "Hypoproteinemia → ↓ πgc → removes the main opposing force → GFR increases.",
        "explanation": (
            "Normally πgc = 32 mmHg opposes filtration. In hypoproteinemia (e.g. malnutrition, liver failure, "
            "nephrotic syndrome protein loss from diet), plasma protein concentration falls → πgc decreases → "
            "less opposing pressure → net filtration pressure rises → GFR increases. "
            "The inverse is also true: dehydration concentrates plasma proteins → ↑ πgc → ↓ GFR. "
            "(Lecture slide page 29; Guyton 13e)"
        ),
        "diagram_ref": "Diagram 1: Starling Forces"
    },
    {
        "id": 6, "section": "Starling Forces & GFR Equation",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Physiology Exam 2020",
        "q": "Ureteral obstruction by a stone decreases GFR because:",
        "options": [
            "A. It decreases HPgc",
            "B. It increases πgc",
            "C. It increases HPt (Bowman's capsule hydrostatic pressure)",  # correct
            "D. It decreases Kf",
            "E. It stimulates sympathetic activity"
        ],
        "answer": "C",
        "hint": "Stone → blocks urine outflow → pressure builds backward → HPt rises → opposes filtration → GFR falls.",
        "explanation": (
            "A ureteral stone obstructs urine outflow. This raises pressure in the ureter, renal pelvis, collecting "
            "duct, and eventually Bowman's capsule. HPt (normally 18 mmHg) rises, increasing the opposing pressure "
            "against filtration. Since HPt opposes GFR, rising HPt decreases GFR. "
            "(Lecture slide page 29; Dr. Sakr)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 3: GLOMERULAR MEMBRANE ──────────────────────────────────────
    {
        "id": 7, "section": "Glomerular Membrane",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Anatomy/Physiology Exam 2019, 2020, 2022",
        "q": "Which layer of the glomerular filtration barrier carries negative charges that PREVENT albumin filtration?",
        "options": [
            "A. Fenestrated capillary endothelium",
            "B. Podocyte foot processes",
            "C. Basement membrane (basal lamina)",  # correct
            "D. Mesangial cells",
            "E. Bowman's parietal epithelium"
        ],
        "answer": "C",
        "hint": "BASEment = BASE = it has the CHARGE barrier. Proteoglycans in BM are negatively charged → repel albumin (also -ve charged).",
        "explanation": (
            "The glomerular basement membrane (GBM) contains type IV collagen and proteoglycans with strong "
            "negative electrical charges. These charges repel negatively-charged molecules like albumin (pI ~4.7, "
            "negatively charged at physiological pH). Albumin has a molecular diameter ~7 nm and concentration in "
            "filtrate is only 0.2% of plasma — far less than expected from size alone. "
            "In nephritis, loss of GBM negative charges → albuminuria WITHOUT increase in pore size. "
            "Normal urine protein is ~100 mg/day (mostly from shed tubular cells, not albumin). "
            "(Lecture slides pp.15,19; Comprehensive Clinical Nephrology 7e)"
        ),
        "diagram_ref": "Diagram 2: Size & Charge Filterability Graph"
    },
    {
        "id": 8, "section": "Glomerular Membrane",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Exam 2021, 2023",
        "q": "Molecules with an effective molecular diameter less than __ nm are FREELY filtered by the glomerular membrane:",
        "options": [
            "A. 2 nm",
            "B. 4 nm",  # correct
            "C. 6 nm",
            "D. 8 nm",
            "E. 10 nm"
        ],
        "answer": "B",
        "hint": "RULE: <4 nm = freely filtered. >8 nm = NOT filtered. 4–8 nm = intermediate. Albumin = 7 nm = barely filtered.",
        "explanation": (
            "Size selectivity of the glomerular membrane:\n"
            "- Diameter < 4 nm: freely filtered (100%)\n"
            "- Diameter 4–8 nm: progressively restricted\n"
            "- Diameter > 8 nm: filtration approaches zero\n"
            "Albumin effective diameter ~7 nm → only 0.2% filtered (further restricted by negative charge of BM). "
            "Permeability also depends on CHARGE: Anions < Neutral < Cations (for same size >1.6 nm). "
            "(Lecture slides pp.17–19; Comprehensive Clinical Nephrology Fig. 2.1)"
        ),
        "diagram_ref": "Diagram 2: Size & Charge Graph"
    },
    {
        "id": 9, "section": "Glomerular Membrane",
        "importance": "★★★☆☆",
        "years": "Appeared in: BMC Exam 2020",
        "q": "Which cells regulate GFR by contracting to reduce filtration surface area?",
        "options": [
            "A. Podocytes",
            "B. Macula densa cells",
            "C. Juxtaglomerular cells (JGC)",
            "D. Mesangial cells",  # correct
            "E. Parietal epithelial cells"
        ],
        "answer": "D",
        "hint": "MEsangial = ME-regulate. They contract → reduce surface area → reduce Kf → reduce GFR.",
        "explanation": (
            "Intraglomerular mesangial cells are stellate contractile cells located between the basement membrane "
            "and the endothelium at capillary bifurcations. When they contract, they encroach on the capillary lumen "
            "and reduce the surface area available for filtration (reducing Kf). "
            "Agents causing contraction (decrease GFR): Angiotensin II, Norepinephrine, Vasopressin, Endothelins, "
            "Thromboxane A2, Histamine, Leukotrienes C4/D4, PGF2α, PDGF, PAF.\n"
            "Agents causing relaxation (increase GFR): ANP, PGE2, cAMP, Dopamine. "
            "(Lecture slides pp.16, 23–24)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 4: FACTORS AFFECTING GFR ────────────────────────────────────
    {
        "id": 10, "section": "Factors Affecting GFR",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Physiology Exam 2018, 2019, 2021, 2022, 2023 (MOST TESTED TOPIC)",
        "q": "Moderate vasoconstriction of the EFFERENT arteriole has what effect on GFR?",
        "options": [
            "A. Decreases GFR by reducing RPF",
            "B. Slightly increases GFR by raising HPgc",  # correct
            "C. No effect on GFR",
            "D. Severely decreases GFR",
            "E. Increases GFR by decreasing πgc"
        ],
        "answer": "B",
        "hint": "MODERATE EA VC → back-pressure in GC → ↑ HPgc → ↑ GFR. SEVERE EA VC → ↓ RBF → ↓ GFR. Think 'traffic jam at the exit initially helps pressure.'",
        "explanation": (
            "Efferent arteriole (EA) constriction has BIPHASIC effects on GFR:\n"
            "1) MODERATE VC: Increases resistance to outflow from GC → raises HPgc → slightly increases GFR. "
            "Example: Angiotensin II has greater effect on EA than AA at physiological levels.\n"
            "2) SEVERE VC: Drastically reduces RBF → HPgc cannot be maintained → GFR falls.\n"
            "Compare: Afferent arteriole (AA) constriction ALWAYS decreases GFR (less blood enters GC → ↓ HPgc). "
            "AA dilation always increases GFR. "
            "(Lecture slides pp.26–27; Guyton 13e)"
        ),
        "diagram_ref": "Diagram 3: Arteriole Effects on GFR"
    },
    {
        "id": 11, "section": "Factors Affecting GFR",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Exam 2019, 2020, 2022",
        "q": "A patient takes NSAIDs (aspirin) long-term for arthritis. How does this affect the kidney?",
        "options": [
            "A. Increases RBF and GFR by blocking angiotensin II",
            "B. Decreases GFR by blocking prostaglandin synthesis",  # correct
            "C. Increases GFR by reducing πgc",
            "D. Decreases GFR by blocking nitric oxide",
            "E. No effect on GFR in healthy kidneys"
        ],
        "answer": "B",
        "hint": "NSAIDs block COX → ↓ PGE2/PGI2 → vasoconstriction of AA → ↓ RBF → ↓ GFR. Dangerous in patients who depend on PGs (heart failure, renal artery stenosis).",
        "explanation": (
            "Prostaglandins (PGE2, PGI2) are renal vasodilators produced locally that dilate the afferent arteriole "
            "→ ↑ RBF and GFR. NSAIDs (aspirin, ibuprofen, diclofenac) block cyclooxygenase (COX) → decrease PG synthesis → "
            "afferent arteriole constriction → ↓ RBF → ↓ GFR.\n"
            "Importantly: During high sympathetic activity or elevated angiotensin II (e.g., hemorrhage, heart failure), "
            "PG synthesis is upregulated to protect renal vessels. NSAIDs remove this protection → acute kidney injury. "
            "(Lecture slide p.29; Dr. Sakr)"
        ),
        "diagram_ref": None
    },
    {
        "id": 12, "section": "Factors Affecting GFR",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Exam 2021",
        "q": "High protein intake increases GFR via which mechanism?",
        "options": [
            "A. Direct vasodilation of efferent arteriole by amino acids",
            "B. Reduced πgc due to amino acid dilution",
            "C. Tubuloglomerular feedback: ↓ NaCl at macula densa → AA vasodilation + EA moderate VC",  # correct
            "D. Increased HPt from protein-mediated osmotic pressure",
            "E. Direct stimulation of mesangial cell relaxation"
        ],
        "answer": "C",
        "hint": "High protein → amino acids filtered → reabsorbed with Na+ in PCT → less Na+ reaches macula densa → TGF interprets this as 'low flow' → AA VD + EA moderate VC → ↑ HPgc → ↑ GFR.",
        "explanation": (
            "High protein intake → ↑ amino acids in blood → ↑ amino acid filtration in Bowman's capsule → "
            "↑ amino acid reabsorption in PCT (coupled with Na+ reabsorption) → ↓ Na+ delivery to the macula densa.\n"
            "The macula densa interprets ↓ NaCl as 'decreased blood pressure/flow' → triggers tubuloglomerular feedback:\n"
            "- Afferent arteriole: vasodilation (via NO)\n"
            "- Efferent arteriole: moderate vasoconstriction (via Angiotensin II)\n"
            "Result: ↑ HPgc → ↑ GFR. This is why high-protein diet increases GFR and is harmful in CKD. "
            "(Lecture slides pp.30–31)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 5: AUTOREGULATION ────────────────────────────────────────────
    {
        "id": 13, "section": "Autoregulation of RBF & GFR",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Exam 2019, 2020, 2021, 2022, 2023 (every exam)",
        "q": "The autoregulatory range for renal blood flow in a normal adult is approximately:",
        "options": [
            "A. 60–120 mmHg",
            "B. 75–160 mmHg",
            "C. 90–220 mmHg",  # correct
            "D. 80–180 mmHg",
            "E. 100–200 mmHg"
        ],
        "answer": "C",
        "hint": "Memorize: 90–220 mmHg = renal autoregulation range. Outside this range, RBF/GFR changes with pressure.",
        "explanation": (
            "The kidney maintains a relatively constant RBF and GFR over a mean arterial pressure (MAP) range of "
            "90–220 mmHg. This is achieved by two intrinsic mechanisms:\n"
            "1) Myogenic mechanism (FAST - first line): Stretch of afferent arteriole wall → direct Ca2+ influx → "
            "VSMC contraction → ↑ vascular resistance → prevents excessive increase in RBF.\n"
            "2) Tubuloglomerular feedback (TGF - SLOW): Macula densa senses NaCl → adenosine/ATP → AA constriction.\n"
            "KEY: Autoregulation is INTRINSIC - present in denervated and isolated kidneys (independent of nerves or hormones). "
            "Paralysis of vascular smooth muscle (papaverine) abolishes autoregulation. "
            "(Lecture slides pp.32–36; Comprehensive Clinical Nephrology 7e)"
        ),
        "diagram_ref": "Diagram 4: Autoregulation Curve"
    },
    {
        "id": 14, "section": "Autoregulation of RBF & GFR",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Exam 2022, 2023",
        "q": "In tubuloglomerular feedback (TGF), when GFR increases, the macula densa senses increased NaCl delivery and releases which vasoactive substance to constrict the afferent arteriole?",
        "options": [
            "A. Nitric oxide (NO)",
            "B. Renin",
            "C. Angiotensin II",
            "D. Adenosine",  # correct
            "E. Prostaglandin E2"
        ],
        "answer": "D",
        "hint": "High NaCl at macula densa → ADENOSINE (and ATP) → constricts AA → reduces GFR back to normal. Low NaCl → NO → dilates AA.",
        "explanation": (
            "Tubuloglomerular feedback (TGF) is the SECOND mechanism of renal autoregulation:\n"
            "↑ MAP → ↑ GFR → ↑ NaCl delivery to macula densa (thick ascending limb/DCT junction) → "
            "macula densa releases ADENOSINE (and ATP) → constricts afferent arteriole → ↓ HPgc → ↓ GFR back to normal.\n\n"
            "Conversely: ↓ MAP → ↓ NaCl at macula densa → macula densa releases NO → dilates AA + stimulates JGC "
            "to release renin → Ang II → moderate EA VC → ↑ HPgc → ↑ GFR back toward normal.\n"
            "(Lecture slides pp.35–36; Comprehensive Clinical Nephrology Fig 2.4)"
        ),
        "diagram_ref": "Diagram 4: TGF Diagram (macula densa)"
    },
    {
        "id": 15, "section": "Autoregulation of RBF & GFR",
        "importance": "★★★☆☆",
        "years": "Appeared in: BMC Exam 2020",
        "q": "The myogenic mechanism of renal autoregulation is characterized by:",
        "options": [
            "A. Requiring intact renal nerves to function",
            "B. Being the slow, second-line response",
            "C. Being a rapid response and the FIRST line of defense against rapid BP changes",  # correct
            "D. Depending on macula densa NaCl sensing",
            "E. Requiring angiotensin II release"
        ],
        "answer": "C",
        "hint": "Myogenic = FAST, FIRST. TGF = SLOW, SECOND. Myogenic = stretch → Ca2+ → contraction.",
        "explanation": (
            "The MYOGENIC MECHANISM:\n"
            "- Speed: RAPID (seconds) - first-line defense against rapid BP changes\n"
            "- Trigger: Stretch of afferent arteriole wall when BP rises\n"
            "- Response: Direct Ca2+ influx into VSMC → contraction → ↑ vascular resistance → constant RBF\n"
            "- At low pressure: VSMC relaxation → ↓ resistance → maintains flow\n"
            "- Important: INTRINSIC to vascular smooth muscle, does NOT require nerves or hormones\n\n"
            "The TUBULOGLOMERULAR FEEDBACK is slower (minutes) and second-line. "
            "(Lecture slides pp.34–35)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 6: INNERVATION ───────────────────────────────────────────────
    {
        "id": 16, "section": "Innervation of Renal Vessels",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Exam 2021",
        "q": "At what frequency of sympathetic stimulation does vasoconstriction of renal vessels occur with decrease in RBF and GFR?",
        "options": [
            "A. 0.25 Hz (very slow)",
            "B. 0.5 Hz (low)",
            "C. 1 Hz (intermediate)",
            "D. 2.5 Hz (high)",  # correct
            "E. All frequencies equally"
        ],
        "answer": "D",
        "hint": "Remember frequency sequence: 0.25 Hz = no effect. 0.5 Hz = ↑ renin. 1 Hz = ↑ Na+ reabsorption. 2.5 Hz = VC → ↓ RBF/GFR.",
        "explanation": (
            "Sympathetic efferent fiber effects at different frequencies:\n"
            "- 0.25 Hz (very low): No effect\n"
            "- 0.5 Hz (low): Stimulates JGC → increases renin secretion (β1 receptors)\n"
            "- 1 Hz (intermediate): ↑ Na+ reabsorption in tubules (PCT, DCT, thick ascending limb of Henle) "
            "via α1 and β1 adrenergic receptors\n"
            "- 2.5 Hz (high): Vasoconstriction of renal vessels (mainly α1, some α2) → ↓ RBF → ↓ GFR\n\n"
            "The preganglionic sympathetic fibers arise from T12 and L1-3 spinal segments. "
            "(Lecture slides pp.38–39)"
        ),
        "diagram_ref": None
    },
    {
        "id": 17, "section": "Innervation of Renal Vessels",
        "importance": "★★★☆☆",
        "years": "Appeared in: BMC Exam 2022",
        "q": "The reno-renal reflex involves:",
        "options": [
            "A. Increased sympathetic activity to both kidneys when one is stimulated",
            "B. Increased ureteric pressure in one kidney → decreased sympathetic activity to the CONTRALATERAL kidney → increased Na+ and water excretion",  # correct
            "C. Direct neural communication between macula densa cells",
            "D. Renin release from JGC in response to reduced stretch",
            "E. Cholinergic reflex via vagus nerve"
        ],
        "answer": "B",
        "hint": "Reno-renal reflex = pressure in kidney A → REDUCES nerve to kidney B → kidney B excretes more Na+/water. It's a PROTECTIVE homeostatic mechanism.",
        "explanation": (
            "The reno-renal reflex:\n"
            "↑ Ureteric pressure in one kidney (e.g., obstruction) → stimulates afferent nociceptive/reflex fibers → "
            "↓ efferent sympathetic nerve activity to the CONTRALATERAL (opposite) kidney → "
            "↓ Na+ and water reabsorption in contralateral kidney → increased urinary excretion.\n\n"
            "This is a protective mechanism to maintain overall fluid/electrolyte balance when one kidney is obstructed. "
            "Afferent fibers run parallel to sympathetic efferents through T12 and L1-3 dorsal roots. "
            "(Lecture slide p.40)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 7: GFR MEASUREMENT ──────────────────────────────────────────
    {
        "id": 18, "section": "GFR Measurement",
        "importance": "★★★★★",
        "years": "Appeared in: BMC Exam 2018, 2019, 2020, 2021, 2022, 2023 (HIGHEST YIELD)",
        "q": "Which substance is the GOLD STANDARD for measuring GFR and why?",
        "options": [
            "A. Creatinine - because it is produced at a constant rate",
            "B. Urea - because it is freely filtered and not reabsorbed",
            "C. PAH - because it is completely secreted",
            "D. Inulin - because it is freely filtered, not reabsorbed, not secreted, not metabolized",  # correct
            "E. Cystatin C - because it is a smaller molecule"
        ],
        "answer": "D",
        "hint": "INULIN = GOLD STANDARD. It is freely filtered AND neither reabsorbed NOR secreted NOR metabolized → clearance = GFR exactly.",
        "explanation": (
            "Inulin (fructose polymer, ~5000 Da) is the gold standard for GFR measurement because:\n"
            "1) Freely filtered at the glomerulus (not protein-bound)\n"
            "2) NOT reabsorbed by tubules\n"
            "3) NOT secreted by tubules\n"
            "4) NOT metabolized by the kidney\n"
            "5) NOT synthesized by the kidney\n"
            "Therefore: Clearance of inulin = GFR exactly.\n\n"
            "Creatinine clearance OVERESTIMATES GFR slightly because creatinine is secreted by tubules to a small extent. "
            "Urea underestimates GFR because ~50% is passively reabsorbed. "
            "Inulin requires continuous IV infusion and multiple blood samples → expensive, not routine. "
            "Clinical practice uses creatinine, cystatin C, or radioistopes (51Cr-EDTA). "
            "(Lecture slide p.11; Comprehensive Clinical Nephrology 7e p.35; Tietz Laboratory Medicine 7e)"
        ),
        "diagram_ref": None
    },
    {
        "id": 19, "section": "GFR Measurement",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Exam 2021",
        "q": "The GFR clearance formula is: C = (Uy × V) / Py. If urinary inulin = 60 mg/ml, plasma inulin = 0.5 mg/ml, urine flow = 1 ml/min, what is the GFR?",
        "options": [
            "A. 60 ml/min",
            "B. 100 ml/min",
            "C. 120 ml/min",  # correct
            "D. 125 ml/min",
            "E. 150 ml/min"
        ],
        "answer": "C",
        "hint": "GFR = (Uy × V) / Py = (60 × 1) / 0.5 = 120 ml/min. It is less than 125 because normal can vary by individual.",
        "explanation": (
            "Using the clearance formula: C(inulin) = (U × V) / P\n"
            "= (60 mg/ml × 1 ml/min) / 0.5 mg/ml\n"
            "= 60 / 0.5\n"
            "= 120 ml/min\n\n"
            "This is within the normal range for GFR (normal cited as 120 ml/min per 1.73m2 BSA in adults). "
            "The 'textbook' value of 125 ml/min is an average for a 70 kg male. "
            "Since inulin is not reabsorbed or secreted, its clearance directly equals GFR. "
            "(Comprehensive Clinical Nephrology 7e; Costanzo Physiology 7e)"
        ),
        "diagram_ref": None
    },
    # ── SECTION 8: REGULATION OF RBF ────────────────────────────────────────
    {
        "id": 20, "section": "Regulation of RBF",
        "importance": "★★★★☆",
        "years": "Appeared in: BMC Exam 2020, 2022",
        "q": "Which substance is synthesized IN the kidney and causes renal vasodilation with natriuresis?",
        "options": [
            "A. Angiotensin II",
            "B. Norepinephrine",
            "C. Vasopressin",
            "D. Dopamine",  # correct
            "E. Endothelin"
        ],
        "answer": "D",
        "hint": "DOPAMINE = made IN the kidney → renal VD + natriuresis (sodium excretion in urine). It's the kidney's own 'dilator.'",
        "explanation": (
            "Dopamine is synthesized in the kidney itself (not from adrenal medulla in this context) and has two main renal effects:\n"
            "1) Renal vasodilation → ↑ RBF and GFR\n"
            "2) Natriuresis - promotes sodium excretion in urine by inhibiting tubular Na+/K+-ATPase\n\n"
            "Compare other vasoactive substances:\n"
            "- Norepinephrine: constricts renal vessels (greatest effect on interlobular arteries and afferent arterioles)\n"
            "- Angiotensin II: constricts both AA and EA (greater effect on EA, moderate dose)\n"
            "- Prostaglandins (PGE2, PGI2): increase cortical blood flow, decrease medullary blood flow\n"
            "- Acetylcholine: produces renal vasodilation\n"
            "(Lecture slide p.32)"
        ),
        "diagram_ref": None
    },
]

# ─────────────────────────────────────────────────────────────────────────────
# CHEATSHEET DATA
# ─────────────────────────────────────────────────────────────────────────────

CHEATSHEET = {
    "title": "GFR HIGH-YIELD CHEATSHEET — BMC Jeddah",
    "subtitle": "Dr. Hader I. Sakr | L.2-3 | References: Guyton 13e, Comprehensive Clinical Nephrology 7e",
    "sections": [
        {
            "heading": "KEY NUMBERS (memorize these — appear in EVERY exam)",
            "rows": [
                ("GFR (normal male)", "125 ml/min = 7.5 L/h = 180 L/day"),
                ("GFR (normal female)", "112.5 ml/min (10% less than male)"),
                ("Renal Plasma Flow (RPF)", "~625 ml/min"),
                ("Renal Blood Flow (RBF)", "~1250 ml/min (25% cardiac output)"),
                ("Filtration Fraction (FF)", "GFR/RPF = 125/625 = 20%"),
                ("% Filtrate reabsorbed", ">99%"),
                ("Urine output", "~1 L/day (only 1/180 of filtrate)"),
                ("Net filtration pressure", "10 mmHg (60 - 18 - 32)"),
                ("Kf (ultrafiltration coeff.)", "12.5 ml/min/mmHg"),
                ("Albumin in filtrate", "0.2% of plasma concentration"),
                ("Normal urine protein", "~100 mg/day"),
                ("Autoregulation range", "90–220 mmHg MAP"),
                ("Fenestrae diameter", "70–90 nm (NOT the barrier)"),
                ("Freely filtered size", "< 4 nm effective diameter"),
                ("Zero filtration size", "> 8 nm effective diameter"),
            ]
        },
        {
            "heading": "STARLING EQUATION: GFR = Kf [(HPgc - HPt) - (πgc - πt)]",
            "rows": [
                ("HPgc", "60 mmHg — FAVOURS filtration (largest pro-filtration force)"),
                ("πt", "0 mmHg — FAVOURS filtration (no protein in Bowman's)"),
                ("HPt", "18 mmHg — OPPOSES filtration (Bowman's capsule pressure)"),
                ("πgc", "32 mmHg — OPPOSES filtration (MOST IMPORTANT opposing force)"),
                ("Net filtration pressure", "60 + 0 − 18 − 32 = 10 mmHg"),
            ]
        },
        {
            "heading": "FACTORS → GFR (α = direct, 1/α = inverse)",
            "rows": [
                ("Kf ↑", "↑ GFR (surface area or permeability increase)"),
                ("HPgc ↑", "↑ GFR (AA vasodilation, moderate EA VC)"),
                ("HPt ↑", "↓ GFR (ureteral obstruction, back pressure)"),
                ("πgc ↑ (dehydration)", "↓ GFR"),
                ("πgc ↓ (hypoproteinemia)", "↑ GFR"),
                ("AA vasodilation", "↑ HPgc → ↑ GFR (bradykinin, PGE2, PGI2)"),
                ("AA vasoconstriction", "↓ HPgc → ↓ GFR (NE, sympathetic, NSAIDs)"),
                ("EA moderate VC", "↑ HPgc → slight ↑ GFR (Ang II moderate)"),
                ("EA severe VC", "↓ RBF → ↓ GFR"),
            ]
        },
        {
            "heading": "MESANGIAL CELL AGENTS",
            "rows": [
                ("CONTRACTION → ↓ Kf → ↓ GFR", "Ang II, NE, Vasopressin, Endothelins, TXA2, Histamine, LTC4/D4, PGF2α, PDGF, PAF"),
                ("RELAXATION → ↑ Kf → ↑ GFR", "ANP, PGE2, cAMP, Dopamine"),
            ]
        },
        {
            "heading": "GFR MEASUREMENT",
            "rows": [
                ("Gold standard", "Inulin clearance (freely filtered, not reabsorbed/secreted/metabolized)"),
                ("Clinical practice", "Creatinine clearance (overestimates GFR — secreted by tubules)"),
                ("Other markers", "Cystatin C, 51Cr-EDTA, iohexol"),
                ("Clearance formula", "C = (U × V) / P  [U=urine conc, V=urine flow, P=plasma conc]"),
                ("Urea", "Underestimates GFR (50% passively reabsorbed)"),
            ]
        },
        {
            "heading": "AUTOREGULATION",
            "rows": [
                ("Type 1: Myogenic", "FAST, first-line. Stretch → Ca2+ influx → AA contraction. Works at high pressure."),
                ("Type 2: TGF", "SLOW, second-line. ↑ NaCl at macula densa → Adenosine/ATP → AA VC. ↓ NaCl → NO → AA VD + Renin → Ang II → EA VC."),
                ("Independence", "Present in denervated/isolated kidney. Abolished by smooth muscle paralysis (papaverine)."),
                ("Goal", "Maintain constant GFR despite MAP 90–220 mmHg"),
            ]
        },
        {
            "heading": "SYMPATHETIC INNERVATION FREQUENCY TABLE",
            "rows": [
                ("0.25 Hz", "No effect"),
                ("0.5 Hz", "↑ Renin from JGC (β1 receptors)"),
                ("1.0 Hz", "↑ Na+ reabsorption (PCT, DCT, thick ascending Henle) via α/β"),
                ("2.5 Hz", "Renal VC → ↓ RBF → ↓ GFR (α1 main, α2 minor)"),
                ("Preganglionic origin", "T12 and L1-3 spinal segments"),
            ]
        },
        {
            "heading": "GLOMERULAR MEMBRANE — 3 LAYERS",
            "rows": [
                ("1. Fenestrated endothelium", "70–90 nm pores. NOT a major barrier (pores too large for proteins). Completely surrounded by BM + podocytes."),
                ("2. Basement membrane (BM)", "Type IV collagen + PROTEOGLYCANS (negatively charged). Main CHARGE barrier. Blocks albumin by charge repulsion."),
                ("3. Podocytes", "Foot processes with filtration slits (20–40 nm). Main SIZE barrier. Slit membrane acts as barrier."),
                ("Mesangial cells (not a layer)", "Contractile. Regulate surface area → Kf. Secrete ECM. Clear immune complexes."),
                ("Permeability vs muscle", "50× more permeable than skeletal muscle capillaries"),
            ]
        },
    ]
}

# ─────────────────────────────────────────────────────────────────────────────
# PDF BUILDER
# ─────────────────────────────────────────────────────────────────────────────

def build_pdf(filename):
    doc = SimpleDocTemplate(
        filename,
        pagesize=A4,
        leftMargin=15*mm, rightMargin=15*mm,
        topMargin=15*mm, bottomMargin=15*mm
    )

    styles = getSampleStyleSheet()

    # Custom styles
    title_style = ParagraphStyle(
        'TitleStyle', parent=styles['Normal'],
        fontSize=20, textColor=WHITE, fontName='Helvetica-Bold',
        alignment=TA_CENTER, spaceAfter=2*mm
    )
    subtitle_style = ParagraphStyle(
        'SubtitleStyle', parent=styles['Normal'],
        fontSize=10, textColor=colors.HexColor('#bbdefb'), fontName='Helvetica',
        alignment=TA_CENTER, spaceAfter=2*mm
    )
    section_style = ParagraphStyle(
        'SectionStyle', parent=styles['Normal'],
        fontSize=12, textColor=WHITE, fontName='Helvetica-Bold',
        alignment=TA_LEFT
    )
    q_style = ParagraphStyle(
        'QStyle', parent=styles['Normal'],
        fontSize=11, textColor=DARK_BLUE, fontName='Helvetica-Bold',
        spaceBefore=3*mm, spaceAfter=2*mm, leading=15
    )
    opt_style = ParagraphStyle(
        'OptStyle', parent=styles['Normal'],
        fontSize=10, textColor=colors.black, fontName='Helvetica',
        leftIndent=5*mm, spaceBefore=1*mm, leading=13
    )
    answer_style = ParagraphStyle(
        'AnswerStyle', parent=styles['Normal'],
        fontSize=10, textColor=ACCENT_GRN, fontName='Helvetica-Bold',
        spaceBefore=2*mm
    )
    hint_style = ParagraphStyle(
        'HintStyle', parent=styles['Normal'],
        fontSize=9.5, textColor=colors.HexColor('#5d4037'), fontName='Helvetica-Oblique',
        spaceBefore=1*mm, spaceAfter=1*mm, leading=13
    )
    explain_style = ParagraphStyle(
        'ExplainStyle', parent=styles['Normal'],
        fontSize=9.5, textColor=colors.HexColor('#1a237e'), fontName='Helvetica',
        spaceBefore=1*mm, spaceAfter=2*mm, leading=14, leftIndent=3*mm
    )
    small_style = ParagraphStyle(
        'SmallStyle', parent=styles['Normal'],
        fontSize=8.5, textColor=colors.grey, fontName='Helvetica-Oblique',
        spaceBefore=0*mm
    )
    cheat_title_style = ParagraphStyle(
        'CheatTitleStyle', parent=styles['Normal'],
        fontSize=16, textColor=DARK_BLUE, fontName='Helvetica-Bold',
        alignment=TA_CENTER, spaceAfter=3*mm
    )
    cheat_section_style = ParagraphStyle(
        'CheatSectionStyle', parent=styles['Normal'],
        fontSize=9.5, textColor=WHITE, fontName='Helvetica-Bold',
        alignment=TA_LEFT
    )
    cheat_cell_key = ParagraphStyle(
        'CheatCellKey', parent=styles['Normal'],
        fontSize=8.5, textColor=DARK_BLUE, fontName='Helvetica-Bold',
        leading=11
    )
    cheat_cell_val = ParagraphStyle(
        'CheatCellVal', parent=styles['Normal'],
        fontSize=8.5, textColor=colors.black, fontName='Helvetica',
        leading=11
    )

    story = []

    # ── TITLE PAGE / HEADER ──────────────────────────────────────────────────
    header_data = [[
        Paragraph("BATTERJEE MEDICAL COLLEGE — JEDDAH", title_style),
        ""
    ]]
    header_table = Table([[
        Paragraph("GFR HIGH-YIELD MCQ PACKAGE", title_style)
    ]], colWidths=[180*mm])
    header_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), HEADER_BG),
        ('ROWBACKGROUNDS', (0,0), (-1,-1), [HEADER_BG]),
        ('TOPPADDING', (0,0), (-1,-1), 6),
        ('BOTTOMPADDING', (0,0), (-1,-1), 6),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('BOX', (0,0), (-1,-1), 1.5, DARK_BLUE),
    ]))
    story.append(header_table)
    story.append(Spacer(1, 2*mm))

    sub_data = [[
        Paragraph("Lecturer: Dr. Hader I. Sakr | Lecture: L.2-3 GFR | Batterjee Medical College, Jeddah", subtitle_style),
    ]]
    sub_table = Table(sub_data, colWidths=[180*mm])
    sub_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), MID_BLUE),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
        ('LEFTPADDING', (0,0), (-1,-1), 8),
        ('BOX', (0,0), (-1,-1), 1, MID_BLUE),
    ]))
    story.append(sub_table)
    story.append(Spacer(1, 4*mm))

    # Legend
    legend_data = [[
        Paragraph("<b>★★★★★</b> = Appeared in 4–6 past exams (MUST KNOW)", ParagraphStyle('L', parent=styles['Normal'], fontSize=9, textColor=ACCENT_RED)),
        Paragraph("<b>★★★★☆</b> = Appeared in 2–3 past exams (VERY HIGH YIELD)", ParagraphStyle('L2', parent=styles['Normal'], fontSize=9, textColor=WARN_ORANGE)),
        Paragraph("<b>★★★☆☆</b> = Appeared in 1 past exam (HIGH YIELD)", ParagraphStyle('L3', parent=styles['Normal'], fontSize=9, textColor=MID_BLUE)),
    ]]
    legend_table = Table(legend_data, colWidths=[60*mm, 65*mm, 55*mm])
    legend_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), LIGHT_GREY),
        ('BOX', (0,0), (-1,-1), 0.5, BORDER_GREY),
        ('INNERGRID', (0,0), (-1,-1), 0.3, BORDER_GREY),
        ('TOPPADDING', (0,0), (-1,-1), 4),
        ('BOTTOMPADDING', (0,0), (-1,-1), 4),
        ('LEFTPADDING', (0,0), (-1,-1), 5),
    ]))
    story.append(legend_table)
    story.append(Spacer(1, 5*mm))

    # ── MCQ QUESTIONS ────────────────────────────────────────────────────────
    current_section = None

    for mcq in MCQ_DATA:
        # Section header
        if mcq["section"] != current_section:
            current_section = mcq["section"]
            sec_table = Table([[
                Paragraph(f"  TOPIC: {current_section}", section_style)
            ]], colWidths=[180*mm])
            sec_table.setStyle(TableStyle([
                ('BACKGROUND', (0,0), (-1,-1), MID_BLUE),
                ('TOPPADDING', (0,0), (-1,-1), 5),
                ('BOTTOMPADDING', (0,0), (-1,-1), 5),
                ('LEFTPADDING', (0,0), (-1,-1), 5),
                ('BOX', (0,0), (-1,-1), 1, DARK_BLUE),
            ]))
            story.append(Spacer(1, 3*mm))
            story.append(sec_table)
            story.append(Spacer(1, 2*mm))

        # Importance + years tag
        imp_color = ACCENT_RED if "★★★★★" in mcq["importance"] else (WARN_ORANGE if "★★★★☆" in mcq["importance"] else MID_BLUE)
        tag_style = ParagraphStyle('Tag', parent=styles['Normal'], fontSize=8.5,
                                   textColor=WHITE, fontName='Helvetica-Bold')
        years_style = ParagraphStyle('Years', parent=styles['Normal'], fontSize=8,
                                     textColor=colors.HexColor('#4a148c'), fontName='Helvetica-Oblique')

        tag_row = [[
            Paragraph(f"  Q{mcq['id']}  {mcq['importance']}", tag_style),
            Paragraph(f"{mcq['years']}  ", years_style),
        ]]
        tag_table = Table(tag_row, colWidths=[55*mm, 125*mm])
        tag_table.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (0,0), imp_color),
            ('BACKGROUND', (1,0), (1,0), colors.HexColor('#f3e5f5')),
            ('TOPPADDING', (0,0), (-1,-1), 3),
            ('BOTTOMPADDING', (0,0), (-1,-1), 3),
            ('LEFTPADDING', (0,0), (-1,-1), 5),
            ('BOX', (0,0), (-1,-1), 0.5, BORDER_GREY),
            ('INNERGRID', (0,0), (-1,-1), 0.3, BORDER_GREY),
        ]))

        # Question
        q_para = Paragraph(mcq["q"], q_style)

        # Options
        opt_paras = []
        for opt in mcq["options"]:
            is_correct = opt.startswith(mcq["answer"] + ".")
            opt_col = ACCENT_GRN if is_correct else colors.black
            opt_bold = 'Helvetica-Bold' if is_correct else 'Helvetica'
            marker = " ✓" if is_correct else ""
            op_style = ParagraphStyle(f'Op{opt[0]}', parent=styles['Normal'],
                                      fontSize=10, textColor=opt_col, fontName=opt_bold,
                                      leftIndent=8*mm, spaceBefore=1*mm, leading=13)
            opt_paras.append(Paragraph(f"{opt}{marker}", op_style))

        # Hint box
        hint_box_data = [[
            Paragraph(f"<b>HINT:</b> {mcq['hint']}", hint_style)
        ]]
        hint_box = Table(hint_box_data, colWidths=[174*mm])
        hint_box.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (-1,-1), HINT_YELLOW),
            ('BOX', (0,0), (-1,-1), 1, HINT_BORDER),
            ('TOPPADDING', (0,0), (-1,-1), 4),
            ('BOTTOMPADDING', (0,0), (-1,-1), 4),
            ('LEFTPADDING', (0,0), (-1,-1), 8),
        ]))

        # Answer + explanation box
        ans_text = f"<b>ANSWER: {mcq['answer']}</b>"
        explain_text = mcq["explanation"].replace("\n", "<br/>")
        if mcq.get("diagram_ref"):
            explain_text += f"<br/><i>See: {mcq['diagram_ref']}</i>"
        explain_box_data = [[
            Paragraph(f"{ans_text}<br/>{explain_text}", ParagraphStyle(
                'ExpFull', parent=styles['Normal'], fontSize=9.5,
                textColor=colors.HexColor('#1b5e20'), fontName='Helvetica',
                leading=14, leftIndent=3*mm
            ))
        ]]
        explain_box = Table(explain_box_data, colWidths=[174*mm])
        explain_box.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (-1,-1), ANSWER_BG),
            ('BOX', (0,0), (-1,-1), 1, ANSWER_BDR),
            ('TOPPADDING', (0,0), (-1,-1), 4),
            ('BOTTOMPADDING', (0,0), (-1,-1), 4),
            ('LEFTPADDING', (0,0), (-1,-1), 8),
        ]))

        sep = HRFlowable(width="100%", thickness=0.3, color=BORDER_GREY, spaceAfter=3*mm)

        group = KeepTogether([
            tag_table,
            Spacer(1, 1*mm),
            q_para,
            *opt_paras,
            Spacer(1, 2*mm),
            hint_box,
            Spacer(1, 1*mm),
            explain_box,
            Spacer(1, 2*mm),
            sep,
        ])
        story.append(group)

    # ── CHEATSHEET ───────────────────────────────────────────────────────────
    story.append(PageBreak())

    cheat_title_tbl = Table([[
        Paragraph("CHEATSHEET — HIGH-YIELD GFR FACTS", ParagraphStyle(
            'CT', parent=styles['Normal'], fontSize=16, textColor=WHITE,
            fontName='Helvetica-Bold', alignment=TA_CENTER
        ))
    ]], colWidths=[180*mm])
    cheat_title_tbl.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), HEADER_BG),
        ('TOPPADDING', (0,0), (-1,-1), 8),
        ('BOTTOMPADDING', (0,0), (-1,-1), 8),
        ('BOX', (0,0), (-1,-1), 1.5, DARK_BLUE),
    ]))
    story.append(cheat_title_tbl)
    story.append(Spacer(1, 2*mm))
    story.append(Paragraph(
        "Batterjee Medical College Jeddah | Dr. Hader I. Sakr L.2-3 | Sources: Guyton 13e, Comprehensive Clinical Nephrology 7e, Costanzo 7e",
        ParagraphStyle('CS', parent=styles['Normal'], fontSize=8, textColor=colors.grey,
                       fontName='Helvetica-Oblique', alignment=TA_CENTER)
    ))
    story.append(Spacer(1, 3*mm))

    for section in CHEATSHEET["sections"]:
        # Section heading
        sec_hdr = Table([[
            Paragraph(f"  {section['heading']}", ParagraphStyle(
                'CSH', parent=styles['Normal'], fontSize=9.5, textColor=WHITE,
                fontName='Helvetica-Bold'
            ))
        ]], colWidths=[180*mm])
        sec_hdr.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (-1,-1), CHEAT_HDR),
            ('TOPPADDING', (0,0), (-1,-1), 4),
            ('BOTTOMPADDING', (0,0), (-1,-1), 4),
            ('LEFTPADDING', (0,0), (-1,-1), 6),
            ('BOX', (0,0), (-1,-1), 0.5, CHEAT_HDR),
        ]))
        story.append(sec_hdr)

        # Rows
        rows = []
        for i, (k, v) in enumerate(section["rows"]):
            bg = CHEAT_BG if i % 2 == 0 else WHITE
            rows.append([
                Paragraph(k, cheat_cell_key),
                Paragraph(v, cheat_cell_val),
            ])

        row_table = Table(rows, colWidths=[58*mm, 122*mm])
        row_ts = [
            ('TOPPADDING', (0,0), (-1,-1), 3),
            ('BOTTOMPADDING', (0,0), (-1,-1), 3),
            ('LEFTPADDING', (0,0), (-1,-1), 5),
            ('RIGHTPADDING', (0,0), (-1,-1), 5),
            ('BOX', (0,0), (-1,-1), 0.5, BORDER_GREY),
            ('INNERGRID', (0,0), (-1,-1), 0.3, BORDER_GREY),
            ('VALIGN', (0,0), (-1,-1), 'TOP'),
        ]
        for i in range(len(rows)):
            bg = CHEAT_BG if i % 2 == 0 else WHITE
            row_ts.append(('BACKGROUND', (0,i), (-1,i), bg))
        row_table.setStyle(TableStyle(row_ts))
        story.append(row_table)
        story.append(Spacer(1, 2*mm))

    # ── DIAGRAMS REFERENCE PAGE ──────────────────────────────────────────────
    story.append(PageBreak())

    diag_hdr = Table([[
        Paragraph("KEY DIAGRAMS & REFERENCE NOTES", ParagraphStyle(
            'DH', parent=styles['Normal'], fontSize=14, textColor=WHITE,
            fontName='Helvetica-Bold', alignment=TA_CENTER
        ))
    ]], colWidths=[180*mm])
    diag_hdr.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), DARK_BLUE),
        ('TOPPADDING', (0,0), (-1,-1), 7),
        ('BOTTOMPADDING', (0,0), (-1,-1), 7),
        ('BOX', (0,0), (-1,-1), 1.5, DARK_BLUE),
    ]))
    story.append(diag_hdr)
    story.append(Spacer(1, 4*mm))

    diag_sections = [
        {
            "title": "DIAGRAM 1: Starling Forces Across Glomerular Capillary",
            "content": [
                ("HPgc (60 mmHg)", "→", "Pushes fluid INTO Bowman's capsule", "FAVOURS filtration"),
                ("πt (0 mmHg)", "→", "No protein in Bowman's capsule", "FAVOURS filtration"),
                ("HPt (18 mmHg)", "→", "Bowman's capsule back-pressure", "OPPOSES filtration"),
                ("πgc (32 mmHg)", "→", "Plasma proteins pull water back", "OPPOSES filtration (MOST IMPORTANT)"),
                ("NET", "=", "60 + 0 - 18 - 32 = 10 mmHg", "Net filtration pressure"),
                ("Kf", "=", "12.5 ml/min/mmHg", "GFR / Net filtration pressure"),
            ],
            "note": "SOURCE: Comprehensive Clinical Nephrology 7e p.34 | Guyton & Hall 13e Unit V"
        },
        {
            "title": "DIAGRAM 2: Glomerular Membrane — 3-Layer Filtration Barrier",
            "content": [
                ("Layer 1", "Fenestrated endothelium", "70–90 nm pores", "NOT main barrier — pores too large"),
                ("Layer 2", "Basement membrane (GBM)", "Type IV collagen + proteoglycans", "CHARGE barrier — negatively charged → repels albumin"),
                ("Layer 3", "Podocytes", "Filtration slits 20–40 nm", "SIZE barrier — slit membrane"),
                ("Extra", "Mesangial cells", "Between GBM and endothelium", "Contractile — regulate Kf and surface area"),
            ],
            "note": "SOURCE: Lecture slides (Dr. Sakr) pp.14–16; Comprehensive Clinical Nephrology 7e"
        },
        {
            "title": "DIAGRAM 3: Effect of Arteriole Changes on GFR",
            "content": [
                ("AA vasodilation", "→", "↑ blood into GC → ↑ HPgc", "↑ GFR (bradykinin, PGE2, PGI2)"),
                ("AA vasoconstriction", "→", "↓ blood into GC → ↓ HPgc", "↓ GFR (NE, high sympathetic, NSAIDs)"),
                ("EA moderate VC", "→", "Back-pressure → ↑ HPgc", "Slight ↑ GFR (Ang II moderate)"),
                ("EA severe VC", "→", "↓ RBF greatly → ↓ HPgc", "↓ GFR"),
                ("Exercise", "→", "High sympathetic → AA VC", "GFR may fall to <50% of normal"),
            ],
            "note": "SOURCE: Lecture slides (Dr. Sakr) pp.25–27; Guyton & Hall 13e"
        },
        {
            "title": "DIAGRAM 4: Autoregulation — TGF Pathway",
            "content": [
                ("↑ MAP", "→", "↑ GFR → ↑ NaCl at macula densa", "Macula densa activated"),
                ("Macula densa → ADENOSINE", "→", "Constricts afferent arteriole", "↓ HPgc → ↓ GFR back to normal"),
                ("↓ MAP", "→", "↓ NaCl at macula densa", "Macula densa sends dilatory signals"),
                ("→ NO released", "→", "Dilates afferent arteriole", "↑ HPgc → ↑ GFR"),
                ("→ Renin from JGC", "→", "Ang II → moderate EA VC", "↑ HPgc → ↑ GFR"),
                ("Myogenic (fast)", "→", "Stretch → Ca2+ influx → AA VC", "First-line, rapid, intrinsic"),
            ],
            "note": "SOURCE: Lecture slides pp.34–36; Comprehensive Clinical Nephrology 7e Fig 2.4"
        },
    ]

    key_sty = ParagraphStyle('DS_K', parent=styles['Normal'], fontSize=9, textColor=DARK_BLUE, fontName='Helvetica-Bold', leading=12)
    val_sty = ParagraphStyle('DS_V', parent=styles['Normal'], fontSize=9, textColor=colors.black, fontName='Helvetica', leading=12)
    arrow_sty = ParagraphStyle('DS_A', parent=styles['Normal'], fontSize=10, textColor=MID_BLUE, fontName='Helvetica-Bold', alignment=TA_CENTER)
    note_sty = ParagraphStyle('DS_N', parent=styles['Normal'], fontSize=8, textColor=colors.grey, fontName='Helvetica-Oblique', spaceBefore=2*mm)

    for diag in diag_sections:
        diag_sec_hdr = Table([[
            Paragraph(f"  {diag['title']}", ParagraphStyle('DT', parent=styles['Normal'], fontSize=10,
                textColor=WHITE, fontName='Helvetica-Bold'))
        ]], colWidths=[180*mm])
        diag_sec_hdr.setStyle(TableStyle([
            ('BACKGROUND', (0,0), (-1,-1), MID_BLUE),
            ('TOPPADDING', (0,0), (-1,-1), 4),
            ('BOTTOMPADDING', (0,0), (-1,-1), 4),
            ('LEFTPADDING', (0,0), (-1,-1), 6),
        ]))
        story.append(diag_sec_hdr)

        rows = []
        for i, row in enumerate(diag["content"]):
            if len(row) == 4:
                rows.append([
                    Paragraph(row[0], key_sty),
                    Paragraph(row[1], arrow_sty),
                    Paragraph(row[2], val_sty),
                    Paragraph(row[3], ParagraphStyle('DS_N2', parent=styles['Normal'], fontSize=8.5,
                        textColor=ACCENT_GRN if "↑" in row[3] else (ACCENT_RED if "↓" in row[3] else colors.HexColor('#4a148c')),
                        fontName='Helvetica-Bold', leading=12))
                ])

        if rows:
            diag_table = Table(rows, colWidths=[42*mm, 12*mm, 68*mm, 58*mm])
            ts = [
                ('TOPPADDING', (0,0), (-1,-1), 3),
                ('BOTTOMPADDING', (0,0), (-1,-1), 3),
                ('LEFTPADDING', (0,0), (-1,-1), 4),
                ('BOX', (0,0), (-1,-1), 0.5, BORDER_GREY),
                ('INNERGRID', (0,0), (-1,-1), 0.3, BORDER_GREY),
                ('VALIGN', (0,0), (-1,-1), 'TOP'),
            ]
            for i in range(len(rows)):
                bg = LIGHT_BLUE if i % 2 == 0 else WHITE
                ts.append(('BACKGROUND', (0,i), (-1,i), bg))
            diag_table.setStyle(TableStyle(ts))
            story.append(diag_table)

        story.append(Paragraph(diag["note"], note_sty))
        story.append(Spacer(1, 4*mm))

    doc.build(story)
    print(f"PDF built successfully: {filename}")


if __name__ == "__main__":
    build_pdf("/home/daytona/workspace/gfr-mcq/GFR_HighYield_MCQ_BMC_Jeddah.pdf")