import type { Product } from "@/lib/data/products";

export type StorageNote = {
  icon: "thermometer-outline" | "sunny-outline" | "happy-outline" | "water-outline";
  title: string;
  body: string;
};

export type DrugFacts = {
  /** Short therapeutic label shown above the product name. */
  useCase: string;
  /** Dose form: Tablet, Syrup, Cream, Device… */
  form: string;
  genericName: string;
  brandNames: string;
  drugClass: string;
  /** Selectable strengths on the detail page. Empty for non-dosed products. */
  dosages: string[];
  sideEffects: { mild: string[]; severe: string[] };
  storage: StorageNote[];
  directions: { title: string; body: string }[];
  stockCount: number;
  /** Pharmacist guidance shown in the safety callout. */
  advice: string;
};

const CATEGORY_USE_CASE: Record<string, string> = {
  medicines: "General Medicine",
  vitamins: "Supplements",
  "personal-care": "Personal Care",
  diabetic: "Diabetes Care",
  devices: "Medical Device",
  baby: "Baby Care",
  "first-aid": "First Aid",
  wellness: "Sexual Wellness",
};

const CATEGORY_FORM: Record<string, string> = {
  medicines: "Tablet",
  vitamins: "Tablet",
  "personal-care": "Topical",
  diabetic: "Tablet",
  devices: "Device",
  baby: "Topical",
  "first-aid": "Supply",
  wellness: "Tablet",
};

/** Per-product clinical overrides. Everything else falls back to category defaults. */
const OVERRIDES: Record<string, Partial<DrugFacts>> = {
  "panadol-advance": {
    useCase: "Pain & Fever",
    genericName: "Paracetamol (Acetaminophen)",
    brandNames: "Panadol, Tylenol, Calpol",
    drugClass: "Analgesic / Antipyretic",
    dosages: ["500mg", "650mg"],
    sideEffects: {
      mild: ["Nausea", "Sleepiness", "Stomach upset"],
      severe: ["Liver damage", "Rash", "Breathing issues"],
    },
    advice: "Do not exceed 4g of paracetamol in 24 hours across all products.",
  },
  paracetamol: {
    useCase: "Pain & Fever",
    genericName: "Paracetamol",
    brandNames: "Panadol, Tylenol",
    drugClass: "Analgesic / Antipyretic",
    dosages: ["500mg"],
    advice: "Avoid alcohol while taking this medicine.",
  },
  "paracetamol-tylenol": {
    useCase: "Pain & Fever",
    genericName: "Acetaminophen",
    brandNames: "Tylenol, Panadol",
    drugClass: "Analgesic",
    dosages: ["500mg", "650mg"],
  },
  "paracetamol-caffeine": {
    useCase: "Headache Relief",
    genericName: "Paracetamol + Caffeine",
    brandNames: "Panadol Extra",
    drugClass: "Analgesic combination",
    dosages: ["500mg / 65mg"],
    advice: "Contains caffeine — limit other caffeinated drinks.",
  },
  snip: {
    useCase: "Cold & Flu",
    genericName: "Paracetamol + Pseudoephedrine + Chlorphenamine",
    brandNames: "SNIP",
    drugClass: "Decongestant combination",
    sideEffects: {
      mild: ["Drowsiness", "Dry mouth", "Dizziness"],
      severe: ["Rapid heartbeat", "High blood pressure"],
    },
    advice: "May cause drowsiness. Do not drive until you know how it affects you.",
  },
  metformin: {
    useCase: "Diabetes Care",
    genericName: "Metformin hydrochloride",
    brandNames: "Glucophage, Glumet",
    drugClass: "Biguanide antidiabetic",
    dosages: ["500mg", "850mg", "1000mg"],
    sideEffects: {
      mild: ["Nausea", "Diarrhoea", "Metallic taste"],
      severe: ["Lactic acidosis", "Vitamin B12 deficiency"],
    },
    advice: "Take with meals to reduce stomach upset. Requires a valid prescription.",
  },
  ciprofloxacin: {
    useCase: "Antibiotic",
    genericName: "Ciprofloxacin",
    brandNames: "Cipro, Ciprobay",
    drugClass: "Fluoroquinolone antibiotic",
    dosages: ["250mg", "500mg"],
    sideEffects: {
      mild: ["Nausea", "Headache", "Dizziness"],
      severe: ["Tendon rupture", "Nerve damage"],
    },
    advice: "Finish the full course even if you feel better.",
  },
  azitro: {
    useCase: "Antibiotic",
    genericName: "Azithromycin",
    brandNames: "Zithromax, Azitro",
    drugClass: "Macrolide antibiotic",
    dosages: ["250mg", "500mg"],
    advice: "Usually taken once daily for 3 days. Complete the course as prescribed.",
  },
  diclofenac: {
    useCase: "Pain & Inflammation",
    genericName: "Diclofenac sodium",
    brandNames: "Voltaren, Cataflam",
    drugClass: "NSAID",
    dosages: ["25mg", "50mg", "75mg"],
    sideEffects: {
      mild: ["Indigestion", "Headache", "Dizziness"],
      severe: ["Stomach bleeding", "Kidney issues"],
    },
    advice: "Take after food. Avoid if you have a history of stomach ulcers.",
  },
  pantoprazole: {
    useCase: "Acid Reflux",
    genericName: "Pantoprazole sodium",
    brandNames: "Protonix, Pantocid",
    drugClass: "Proton pump inhibitor",
    dosages: ["20mg", "40mg"],
    advice: "Take 30–60 minutes before your first meal of the day.",
  },
  desloratidine: {
    useCase: "Allergy Relief",
    genericName: "Desloratadine",
    brandNames: "Clarinex, Aerius",
    drugClass: "Antihistamine",
    dosages: ["5mg"],
    advice: "Non-drowsy for most people, but avoid driving until you're sure.",
  },
  "nat-c-vitamin-c": {
    useCase: "Immune Support",
    genericName: "Ascorbic acid",
    brandNames: "Nat C, Redoxon",
    drugClass: "Vitamin supplement",
    dosages: ["500mg", "1000mg"],
    sideEffects: { mild: ["Stomach upset", "Heartburn"], severe: ["Kidney stones (high doses)"] },
  },
  gofen: {
    useCase: "Pain & Inflammation",
    genericName: "Ibuprofen",
    brandNames: "Brufen, Advil, Gofen",
    drugClass: "NSAID",
    dosages: ["200mg", "400mg"],
    advice: "Take with food or milk to protect your stomach.",
  },
  quemox: {
    useCase: "Antibiotic",
    genericName: "Amoxicillin",
    brandNames: "Amoxil, Quemox",
    drugClass: "Penicillin antibiotic",
    dosages: ["250mg", "500mg"],
    advice: "Tell your pharmacist about any penicillin allergy before use.",
  },
  sildenafil: {
    useCase: "Sexual Wellness",
    genericName: "Sildenafil citrate",
    brandNames: "Viagra, Cialis (tadalafil alt.)",
    drugClass: "PDE5 inhibitor",
    dosages: ["25mg", "50mg", "100mg"],
    advice: "Never combine with nitrate heart medicines. Prescription required.",
  },
  "ors-sachets": {
    useCase: "Rehydration",
    genericName: "Oral rehydration salts",
    brandNames: "ORS, Hydralyte",
    drugClass: "Electrolyte replacement",
    advice: "Dissolve one sachet in 200ml of clean water. Use within 24 hours.",
  },
  "cough-syrup": {
    useCase: "Cough Relief",
    form: "Syrup",
    genericName: "Dextromethorphan / Guaifenesin",
    brandNames: "Robitussin, Benylin",
    drugClass: "Antitussive / Expectorant",
    dosages: ["100ml", "200ml"],
  },
  "lubricating-eye-drops": {
    useCase: "Eye Care",
    form: "Drops",
  },
  "eye-drops-lubricating": {
    useCase: "Eye Care",
    form: "Drops",
    genericName: "Carboxymethylcellulose",
    brandNames: "Refresh Tears, Optive",
    drugClass: "Ocular lubricant",
  },
  "blood-pressure-monitor": {
    useCase: "Monitoring",
    form: "Device",
    genericName: "Upper-arm oscillometric monitor",
    brandNames: "HealthTech",
    drugClass: "Class II medical device",
  },
  "glucose-meter-kit": {
    useCase: "Diabetes Care",
    form: "Device",
    genericName: "Blood glucose monitoring system",
    brandNames: "DiaCare",
    drugClass: "Class II medical device",
  },
};

const DEFAULT_SIDE_EFFECTS: DrugFacts["sideEffects"] = {
  mild: ["Nausea", "Headache", "Mild dizziness"],
  severe: ["Allergic reaction", "Difficulty breathing"],
};

const DEFAULT_STORAGE: StorageNote[] = [
  {
    icon: "thermometer-outline",
    title: "Temperature",
    body: "Store at room temperature, between 20°C and 25°C.",
  },
  {
    icon: "sunny-outline",
    title: "Light & moisture",
    body: "Keep in a dry place, away from direct sunlight.",
  },
  {
    icon: "happy-outline",
    title: "Children",
    body: "Keep out of reach of children to prevent accidental ingestion.",
  },
];

const DEFAULT_DIRECTIONS: DrugFacts["directions"] = [
  {
    title: "Check with your pharmacist",
    body: "Confirm the dose is right for your age, weight and other medicines.",
  },
  {
    title: "Take as directed",
    body: "Follow the schedule on the label. Do not double up on a missed dose.",
  },
  {
    title: "Take with water",
    body: "Swallow whole with a full glass of water unless told otherwise.",
  },
  {
    title: "Track your response",
    body: "Stop and contact us if symptoms persist beyond 3 days.",
  },
];

const DEVICE_DIRECTIONS: DrugFacts["directions"] = [
  { title: "Unbox and inspect", body: "Check all parts are present and undamaged." },
  { title: "Prepare", body: "Sit still for 5 minutes and rest your arm at heart level." },
  { title: "Measure", body: "Follow the on-screen prompts and stay quiet during the reading." },
  { title: "Log the result", body: "Record readings so your pharmacist can review trends." },
];

/** Deterministic pseudo-stock so the number is stable between renders. */
function stockFor(product: Product): number {
  if (!product.inStock) return 0;
  const seed = product.id
    .split("")
    .reduce((total, char) => total + char.charCodeAt(0), 0);
  return 8 + (seed % 44);
}

export function getDrugFacts(product: Product): DrugFacts {
  const override = OVERRIDES[product.slug] ?? {};
  const isDevice = product.category === "devices" || product.category === "first-aid";

  return {
    useCase: override.useCase ?? CATEGORY_USE_CASE[product.category] ?? "Healthcare",
    form: override.form ?? CATEGORY_FORM[product.category] ?? "Unit",
    genericName: override.genericName ?? product.name,
    brandNames: override.brandNames ?? product.brand,
    drugClass: override.drugClass ?? CATEGORY_USE_CASE[product.category] ?? "Healthcare product",
    dosages: override.dosages ?? [],
    sideEffects:
      override.sideEffects ??
      (isDevice ? { mild: ["Skin irritation"], severe: [] } : DEFAULT_SIDE_EFFECTS),
    storage: override.storage ?? DEFAULT_STORAGE,
    directions: override.directions ?? (isDevice ? DEVICE_DIRECTIONS : DEFAULT_DIRECTIONS),
    stockCount: override.stockCount ?? stockFor(product),
    advice:
      override.advice ??
      (product.requiresPrescription
        ? "A valid prescription is required. Our pharmacist will verify it before dispatch."
        : "Speak to our pharmacist if you are pregnant, breastfeeding or taking other medicines."),
  };
}

/** Star distribution for the review summary, weighted by the product rating. */
export function getReviewBreakdown(product: Product) {
  const weights = [0.62, 0.22, 0.09, 0.04, 0.03];
  const shift = Math.max(0, Math.round((4.8 - product.rating) * 10)) / 100;
  return [5, 4, 3, 2, 1].map((stars, index) => {
    const weight = Math.max(0.01, weights[index] - (index === 0 ? shift : -shift / 4));
    return { stars, count: Math.max(1, Math.round(product.reviews * weight)) };
  });
}