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const fs = require('fs');

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// ─── TITLE PAGE ───────────────────────────────────────────────────
const titleSection = [
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  new Paragraph({
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    children: [new TextRun({ text: "PUPILLARY LIGHT REFLEX", bold: true, color: BLUE, size: 56 })]
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];

// ─── SECTION 1: DEFINITION & OVERVIEW ─────────────────────────────
const sec1 = [
  heading1("1.  Definition & Overview"),
  divider(),
  body("The pupillary light reflex (PLR) is the constriction of the pupil in response to light stimulation of the retina. It is a brain stem reflex that does not involve the cerebral cortex."),
  ...spacer(1),
  body("Key characteristics:"),
  bullet("Consensual: light in ONE eye causes constriction of BOTH pupils"),
  bullet("Mediated by CN II (afferent) and CN III (efferent)"),
  bullet("Reflex centre: Pretectal nucleus (olivary pretectal nucleus), dorsal midbrain"),
  bullet("Bypasses the lateral geniculate body and visual cortex"),
  bullet("Most resistant of all nervous system responses to metabolic insult"),
  ...spacer(1),
  highlightBox([
    "★  KEY EXAM POINT",
    "The afferent fibres leave the optic tract BEFORE the lateral geniculate body.",
    "This is why cortical blindness (damage to visual cortex / optic radiations) PRESERVES the pupillary light reflex.",
    "The reflex arc is: Retina → CN II → Pretectal nucleus → Edinger-Westphal nucleus → CN III → Ciliary ganglion → Short ciliary nerves → Sphincter pupillae"
  ], KEY_FILL, "FFC000"),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 2: COMPLETE PATHWAY ──────────────────────────────────
const sec2 = [
  heading1("2.  Complete Pathway – Step by Step"),
  divider(),

  heading2("2.1  Afferent Limb (Sensory – CN II)"),

  heading3("Step 1 – Retinal Photoreceptors"),
  bullet("Light stimulates rods and cones in the outer retina"),
  bullet("Intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) containing melanopsin also directly detect ambient light intensity"),
  bullet("ipRGCs are irradiance detectors – NOT image-forming cells"),
  bulletMixed([
    new TextRun({ text: "Clinical significance: ", bold: true, size: 22 }),
    new TextRun({ text: "Pupillary light reflexes are preserved even in patients with rod and cone degeneration (functionally blind), because ipRGCs are intact", size: 22 })
  ]),

  heading3("Step 2 – Bipolar Cells (Inner Nuclear Layer of Retina)"),
  bullet("Signals pass from photoreceptors through bipolar cells"),

  heading3("Step 3 – Retinal Ganglion Cells → Optic Nerve → Optic Chiasm → Optic Tract"),
  bullet("Retinal ganglion cell axons converge to form the optic nerve (CN II)"),
  bullet("At the optic chiasm: nasal fibres decussate (cross), temporal fibres remain ipsilateral (~53% crossed, 47% uncrossed)"),
  bullet("Fibres continue in the optic tract toward the midbrain"),

  ...spacer(1),
  highlightBox([
    "★  CRITICAL DIVERGENCE POINT",
    "Pupillary light reflex fibres LEAVE the optic tract just ROSTRAL (anterior) to the lateral geniculate body (LGB).",
    "They do NOT synapse in the LGB.",
    "They pass via the brachium of the superior colliculus to reach the pretectal nucleus.",
    "Result: Lesions of the visual cortex or optic radiations → cortical blindness but INTACT pupillary light reflex."
  ], KEY_FILL, "FFC000"),
  ...spacer(1),

  heading3("Step 4 – Pretectal Nucleus (Olivary Pretectal Nucleus), Dorsal Midbrain"),
  bullet("Pupillary fibres synapse in the olivary pretectal nucleus at the level of the superior colliculus"),
  bullet("This nucleus receives bilateral input (due to partial chiasmal decussation)"),

  heading2("2.2  Internuncial Neurons – Bilateral Distribution"),
  bullet("Axons from each pretectal nucleus pass to BOTH Edinger-Westphal (EW) nuclei:"),
  bullet("(a)  Directly to the ipsilateral EW nucleus", 1),
  bullet("(b)  Crossing via the posterior commissure to the contralateral EW nucleus", 1),
  ...spacer(1),
  highlightBox([
    "This bilateral distribution is the anatomical basis for the CONSENSUAL reflex.",
    "Lesion of the posterior commissure (e.g., pinealoma) → BILATERAL fixed, slightly large pupils (5–6 mm)."
  ], WARN_FILL, "FF0000"),
  ...spacer(1),

  heading2("2.3  Efferent Limb (Motor – CN III) – Two-Neuron Parasympathetic Pathway"),

  heading3("Neuron 1 (Preganglionic): Edinger-Westphal Nucleus → CN III"),
  bullet("Edinger-Westphal (EW) nucleus = accessory parasympathetic nucleus of CN III"),
  bullet("Located just DORSAL to the main oculomotor nucleus, close to the midline, in the midbrain tegmentum"),
  bullet("Preganglionic parasympathetic fibres travel in CN III on its SUPERFICIAL / DORSOMEDIAL surface"),
  bullet("Enter the inferior division of CN III → travel via the nerve to the inferior oblique → reach the ciliary ganglion"),
  ...spacer(1),
  highlightBox([
    "★  WHY COMPRESSION AFFECTS PUPIL FIRST:",
    "Pupilloconstrictor fibres run SUPERFICIALLY in CN III.",
    "Compression (e.g., posterior communicating artery aneurysm, uncal herniation) affects the outer fibres first → dilated unreactive pupil BEFORE somatic motor loss.",
    "Ischaemic CN III palsy (e.g., diabetes) affects the central fibres → somatic motor paresis with PUPIL-SPARING."
  ], WARN_FILL, "FF4500"),
  ...spacer(1),

  heading3("Synapse 2 – Ciliary Ganglion (Orbit)"),
  bullet("Located within the muscle cone, just BEHIND the globe, in the posterior orbit"),
  bullet("Preganglionic fibres synapse here on postganglionic parasympathetic neurons"),
  bullet("Other fibres (sympathetic, sensory) pass through WITHOUT synapsing – only parasympathetic fibres synapse here"),

  heading3("Neuron 2 (Postganglionic): Short Ciliary Nerves → Sphincter Pupillae"),
  bullet("Postganglionic fibres leave the ciliary ganglion as short ciliary nerves (6–10 in number)"),
  bullet("Innervate the sphincter pupillae (circular smooth muscle of the iris)"),
  bullet("Sphincter pupillae contraction → MIOSIS (pupil constriction)"),

  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 3: SUMMARY TABLE ─────────────────────────────────────
const sec3 = [
  heading1("3.  Pathway Summary Table"),
  divider(),
  makeTable(
    ["Step", "Structure", "Notes"],
    [
      ["1", "Retina (rods/cones + ipRGCs)", "melanopsin in ipRGCs; preserved in rod/cone degeneration"],
      ["2", "Bipolar cells", "Inner nuclear layer of retina"],
      ["3", "Retinal ganglion cells → Optic nerve", "Axons form CN II"],
      ["4", "Optic chiasm", "Nasal fibres cross; 53:47 ratio"],
      ["5", "Optic tract", "Bilateral representation"],
      ["6", "Fibres leave optic tract (before LGB)", "Critical divergence point; via brachium of SC"],
      ["7", "Pretectal nucleus (olivary)", "Dorsal midbrain; first synapse"],
      ["8", "Internuncial neurons via posterior commissure", "Bilateral EW nucleus distribution"],
      ["9", "Edinger-Westphal nucleus (bilateral)", "Midbrain; preganglionic parasympathetic origin"],
      ["10", "CN III (inferior division)", "Superficial fibres; pupilloconstrictor"],
      ["11", "Ciliary ganglion (orbit)", "Second synapse; only parasympathetic fibres synapse"],
      ["12", "Short ciliary nerves", "Postganglionic parasympathetic"],
      ["13", "Sphincter pupillae", "MIOSIS (constriction)"],
    ]
  ),
  ...spacer(2),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 4: DIRECT vs CONSENSUAL ─────────────────────────────
const sec4 = [
  heading1("4.  Direct vs Consensual Reflex"),
  divider(),
  makeTable(
    ["Feature", "Direct Reflex", "Consensual Reflex"],
    [
      ["Definition", "Constriction of illuminated eye's pupil", "Constriction of opposite eye's pupil"],
      ["Afferent", "Ipsilateral optic nerve", "Ipsilateral optic nerve"],
      ["Efferent", "Ipsilateral CN III", "Contralateral CN III"],
      ["Mechanism", "Ipsilateral EW nucleus activation", "Crossing via posterior commissure"],
      ["Clinical use", "Tests afferent + efferent (same side)", "Tests afferent (one side) + efferent (other side)"],
    ]
  ),
  ...spacer(2),

  heading2("Practical Testing – Swinging Flashlight Test"),
  body("Alternately swing a bright light from one eye to the other at ~1-second intervals."),
  bullet("Normal: both pupils constrict equally when either eye is illuminated"),
  bullet("RAPD present: when light swings to the affected eye, both pupils dilate (paradoxically) due to weak afferent signal"),
  ...spacer(1),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 5: ANATOMICAL KEY POINTS ────────────────────────────
const sec5 = [
  heading1("5.  Key Anatomical Points"),
  divider(),
  makeTable(
    ["Point", "Detail"],
    [
      ["Afferent nerve", "CN II (Optic nerve)"],
      ["Efferent nerve", "CN III (Oculomotor nerve)"],
      ["Reflex centre", "Pretectal nucleus (olivary pretectal nucleus), dorsal midbrain"],
      ["Parasympathetic nucleus", "Edinger-Westphal nucleus (part of CN III nuclear complex)"],
      ["Why consensual?", "Internuncial neurons cross via posterior commissure to both EW nuclei"],
      ["Critical divergence", "Fibres leave optic tract BEFORE LGB → bypass visual cortex"],
      ["Ganglion in orbit", "Ciliary ganglion (only parasympathetic synapse here)"],
      ["Final effector", "Sphincter pupillae muscle (circular smooth muscle)"],
      ["Pupilloconstrictor position in CN III", "Superficial / dorsomedial – vulnerable to compression"],
      ["ipRGCs", "Intrinsically photosensitive retinal ganglion cells; contain melanopsin; drive PLR"],
    ]
  ),
  ...spacer(2),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 6: CLINICAL CORRELATIONS ────────────────────────────
const sec6 = [
  heading1("6.  Clinical Correlations"),
  divider(),

  heading2("6.1  Relative Afferent Pupillary Defect (RAPD) – Marcus Gunn Pupil"),
  highlightBox([
    "Cause: Optic nerve lesion (unilateral or asymmetric)",
    "Test: Swinging Flashlight Test",
    "Finding: Light swings to affected eye → both pupils PARADOXICALLY DILATE",
    "Explanation: Weak afferent signal from diseased eye → EW nucleus less stimulated → pupils dilate",
    "Lesion sites: retina, optic nerve, optic chiasm, optic tract, pretectal nucleus",
    "Note: RAPD is NEVER caused by a dense cataract (media opacity does NOT produce RAPD)"
  ], GREEN_FILL, "00B050"),
  ...spacer(1),

  heading2("6.2  Absolute Afferent Pupillary Defect (Amaurotic Pupil)"),
  bullet("Cause: Complete optic nerve lesion"),
  bullet("Affected eye: completely blind (no light perception)"),
  bullet("Light in affected eye → NEITHER pupil reacts"),
  bullet("Light in normal eye → BOTH pupils react normally"),
  bullet("Near reflex: normal in both eyes"),
  ...spacer(1),

  heading2("6.3  CN III Palsy – Efferent Defect"),
  bullet("Pupil is DILATED and UNREACTIVE (mydriasis) – loss of parasympathetic constriction"),
  bullet("Both direct AND consensual reflex lost in the affected eye"),
  bullet("Consensual reflex still intact in the other eye (afferent is intact)"),
  bullet("Associated with: ptosis, 'down and out' gaze (exotropia + hypotropia)"),
  bullet("Compressive CN III (aneurysm, herniation): pupil involved FIRST"),
  bullet("Ischaemic CN III (diabetes, hypertension): pupil SPARED"),
  ...spacer(1),

  heading2("6.4  Horner's Syndrome – Sympathetic Pathway Disruption"),
  highlightBox([
    "NOT a PLR pathway defect (sympathetic pathway is separate).",
    "Features: Miosis (small pupil), Ptosis (partial), Anhidrosis (if pre-ganglionic), Enophthalmos (apparent)",
    "Pupil still CONSTRICTS to light, but DILATES poorly in the dark.",
    "Causes: Pancoast tumour, carotid artery dissection, lateral medullary syndrome, cervical cord lesions"
  ], TABLE_ALT, LIGHT_BLUE),
  ...spacer(1),

  heading2("6.5  Light-Near Dissociation (Argyll Robertson Pupil)"),
  bullet("Pupil constricts to NEAR (accommodation-convergence) but NOT to LIGHT"),
  bullet("Classic causes: Neurosyphilis, Parinaud's syndrome, aberrant CN III regeneration, diabetes"),
  bullet("Lesion: Dorsal internuncial neurons in pretectal area (connecting pretectal nucleus to EW nucleus)"),
  bullet("Near reflex centre is more VENTRAL in midbrain – spared by dorsal lesions"),
  bullet("Pupils typically small, irregular, bilateral in Argyll Robertson"),
  ...spacer(1),

  heading2("6.6  Parinaud's Syndrome / Pinealoma"),
  bullet("Compresses posterior commissure and pretectal area"),
  bullet("Results: bilateral fixed pupils (internuncial neurons disrupted)"),
  bullet("Also: upgaze palsy, convergence-retraction nystagmus, pseudo-Argyll Robertson pupils"),
  ...spacer(1),

  heading2("6.7  Pupillary Findings in Coma (Localisation Value)"),
  makeTable(
    ["Lesion Level", "Pupil Size", "Reactivity", "Clinical Significance"],
    [
      ["Metabolic coma", "Small (bilateral)", "Reactive", "Last sign to go in metabolic causes"],
      ["Diencephalon", "Small (bilateral)", "Reactive", "Also seen in metabolic coma – limited localising value"],
      ["Midbrain", "Mid-position 5–6 mm", "Fixed", "Bilateral EW nucleus damage; posterior commissure lesion"],
      ["Pons", "Pinpoint (bilateral)", "Reactive", "Pontine haemorrhage; loss of sympathetic, parasympathetic intact"],
      ["Uncal herniation (CN III)", "Unilateral dilated", "Fixed", "Compressive CN III; ominous sign"],
      ["Horner's (sympathetic)", "Unilateral small", "Reactive", "Ipsilateral ptosis + anhidrosis"],
    ]
  ),
  ...spacer(1),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 7: NEAR REFLEX ───────────────────────────────────────
const sec7 = [
  heading1("7.  Near Reflex (Accommodation-Convergence Reflex)"),
  divider(),
  body("The near reflex is a SYNKINESIS (not a true reflex) activated when gaze shifts from distant to near target."),
  ...spacer(1),
  body("It comprises THREE components:"),
  bullet("Accommodation – lens thickening (ciliary muscle contraction)"),
  bullet("Convergence – medial rectus contraction"),
  bullet("Miosis – sphincter pupillae contraction"),
  ...spacer(1),
  body("The final pathways are IDENTICAL to the light reflex (CN III → ciliary ganglion → short ciliary nerves)."),
  body("The near reflex centre is more VENTRAL in the midbrain than the pretectal nucleus for the light reflex."),
  ...spacer(1),
  highlightBox([
    "IMPORTANT: There is no condition in which the light reflex is PRESENT but the near response is ABSENT.",
    "However, the converse IS possible (Light-Near Dissociation = near present, light absent) –",
    "seen in Argyll Robertson pupil (neurosyphilis), Parinaud's syndrome."
  ], KEY_FILL, "FFC000"),
  ...spacer(1),
  new Paragraph({ children: [new PageBreak()] })
];

// ─── SECTION 8: QUICK REVISION BOX ───────────────────────────────
const sec8 = [
  heading1("8.  Quick Revision – High-Yield Summary"),
  divider(),
  highlightBox([
    "AFFERENT: Retina → Bipolar cells → Retinal ganglion cells → Optic nerve (CN II) → Optic chiasm → Optic tract",
    "↓ (fibres leave BEFORE LGB via brachium of superior colliculus)",
    "→ Pretectal nucleus (olivary, dorsal midbrain)  ← FIRST SYNAPSE",
    "→ Internuncial neurons → BOTH EW nuclei (via posterior commissure for contralateral)",
    "",
    "EFFERENT: EW nucleus → CN III (superficial fibres) → Ciliary ganglion (orbit)  ← SECOND SYNAPSE",
    "→ Short ciliary nerves → Sphincter pupillae → MIOSIS",
    "",
    "CONSENSUAL reflex = bilateral EW distribution via posterior commissure",
    "PUPIL SPARING CN III palsy = ischaemic (central fibres affected first)",
    "RAPD = afferent limb lesion; detected by swinging flashlight test",
    "Argyll Robertson = light-near dissociation; neurosyphilis",
    "Cortical blindness = INTACT pupillary light reflex (reflex bypasses cortex)"
  ], GREEN_FILL, "00B050"),
  ...spacer(2),

  heading2("Nerve – Nucleus Quick Reference"),
  makeTable(
    ["Component", "Nerve / Structure", "Location"],
    [
      ["Afferent", "CN II – Optic nerve", "Retina to pretectal nucleus"],
      ["1st synapse", "Olivary pretectal nucleus", "Dorsal midbrain (pretectum)"],
      ["Internuncial", "Via posterior commissure", "Dorsal midbrain"],
      ["Pre-ganglionic parasympathetic", "Edinger-Westphal nucleus → CN III", "Midbrain tegmentum"],
      ["2nd synapse", "Ciliary ganglion", "Posterior orbit (muscle cone)"],
      ["Post-ganglionic", "Short ciliary nerves", "Orbit to iris"],
      ["Effector", "Sphincter pupillae", "Iris (circular smooth muscle)"],
    ]
  ),
  ...spacer(2),

  heading2("Sources"),
  body("• Adams and Victor's Principles of Neurology, 12th Edition", { italics: true }),
  body("• Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition", { italics: true }),
  body("• Localization in Clinical Neurology, 8th Edition", { italics: true }),
  body("• Plum and Posner's Diagnosis and Treatment of Stupor and Coma", { italics: true }),
  body("• Neuroscience: Exploring the Brain, 5th Edition", { italics: true }),
];

// ─── ASSEMBLE DOCUMENT ────────────────────────────────────────────
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