import {
  INGREDIENT_LABEL_SYNONYMS_EN,
  INGREDIENT_LABELS_EN,
  UNIT_LABELS_EN,
} from "@batch-cooking/shared";
import { prisma } from "../../db/prisma.js";
import { normalizeText } from "./tech-step-matcher.js";

/**
 * Resolves the free-text `name`/`unit`/`quantity` a `RecipeSourceAdapter`
 * lifts from an English-language source (`ParsedRecipeIngredient`) against
 * our own `Ingredient`/`Unit` reference catalogs — the ingredient-side
 * counterpart to `tech-step-matcher.ts`'s technique detection, built for
 * the same reason: an English source's raw text has no idea our catalogs
 * even exist.
 *
 * Unlike tech steps (regex mappings hand-authored per technique),
 * ingredient/unit labels are plain hand-written English text
 * (`INGREDIENT_LABELS_EN`/`UNIT_LABELS_EN`, `packages/shared`) — matching
 * them against arbitrary free text (extra adjectives, plurals, "large diced
 * yellow onion" for a catalog entry that's just "Onion") needs its own,
 * lighter algorithm: word-tokenize both sides, naively stem for plurals,
 * then look for the catalog phrase's tokens as a contiguous run inside the
 * ingredient text's tokens. The longest (most specific) matching catalog
 * phrase wins, same "specificity resolves overlaps" idea as
 * `matchTechSteps`, just without weights (there's no need to rank two
 * *unrelated* ingredients — only a phrase against its own substrings, e.g.
 * "chicken breast" beating bare "chicken").
 *
 * `matchIngredientName`/`matchUnit`/`extractQuantity` are pure, so they're
 * unit-testable without a database (see `test/ingredient-matcher.test.ts`);
 * `loadIngredientCatalog`/`loadUnitCatalog` are the only DB-touching pieces,
 * meant to be fetched once per request and reused across every ingredient
 * line, the same "don't requery per item" convention
 * `tech-step-matcher.ts`'s `TechStepClassifierService` follows for its own
 * one-time training pass.
 */

/** One `Ingredient` row trimmed to what {@link matchIngredientName} needs, alongside its English matching label. */
export interface IngredientMatchEntry {
  ingredientId: number;
  /** English label from `INGREDIENT_LABELS_EN`, e.g. `"Chicken breast"` — matched against free text, never displayed. */
  label: string;
}

/** One `Unit` row trimmed to what {@link matchUnit} needs, alongside its accepted English spellings. */
export interface UnitMatchEntry {
  unitId: number;
  /** Accepted spellings from `UNIT_LABELS_EN`, e.g. `["tbsp", "tbs", "tablespoon", "tablespoons"]`. */
  synonyms: string[];
}

/**
 * Naive English stemmer — strips a plural suffix so "tomato"/"tomatoes",
 * "onion"/"onions", "cherry"/"cherries" compare equal after stemming.
 * Deliberately not a real linguistic stemmer: it only has to be
 * *consistent* (the same word always stems the same way) since both sides
 * of every comparison go through it, not linguistically correct on its
 * own — see the module doc comment.
 */
function stemWord(word: string): string {
  if (word.endsWith("ies") && word.length > 4) return `${word.slice(0, -3)}y`;
  if (word.endsWith("es") && word.length > 3) return word.slice(0, -2);
  if (word.endsWith("s") && !word.endsWith("ss") && word.length > 3) return word.slice(0, -1);
  return word;
}

/** Lowercases, strips diacritics (via `normalizeText`) and splits `text` into stemmed word tokens — empty/non-letter runs are dropped, not kept as empty tokens. */
function tokenize(text: string): string[] {
  return normalizeText(text)
    .split(/[^a-z]+/)
    .filter((word) => word.length > 0)
    .map(stemWord);
}

/** Whether `needle` appears as a contiguous run inside `haystack`, at any starting position. */
function containsSubsequence(haystack: string[], needle: string[]): boolean {
  if (needle.length === 0 || needle.length > haystack.length) return false;
  for (let start = 0; start <= haystack.length - needle.length; start++) {
    if (needle.every((word, i) => haystack[start + i] === word)) return true;
  }
  return false;
}

/**
 * Resolves free-text `name` (a `ParsedRecipeIngredient.name`, e.g. `"large
 * diced yellow onions"`) to the best-matching `Ingredient` in `catalog`, or
 * `null` if nothing matches. Among every catalog entry whose label's words
 * all appear as a contiguous run in `name`, the one with the most words
 * wins (most specific — "chicken breast" over bare "chicken"); ties break
 * on the lowest `ingredientId`, for a deterministic result independent of
 * catalog order.
 */
export function matchIngredientName(name: string, catalog: IngredientMatchEntry[]): number | null {
  const nameTokens = tokenize(name);
  if (nameTokens.length === 0) return null;

  let best: { ingredientId: number; tokenCount: number } | null = null;
  for (const entry of catalog) {
    const labelTokens = tokenize(entry.label);
    if (!containsSubsequence(nameTokens, labelTokens)) continue;
    if (
      best === null ||
      labelTokens.length > best.tokenCount ||
      (labelTokens.length === best.tokenCount && entry.ingredientId < best.ingredientId)
    ) {
      best = {
        ingredientId: entry.ingredientId,
        tokenCount: labelTokens.length,
      };
    }
  }
  return best?.ingredientId ?? null;
}

/**
 * Resolves free-text `unitText` (e.g. `"tbsp"`, `"Cups"`) to the matching
 * `Unit` in `catalog`, or `null` if nothing matches. A unit is a single
 * word by convention (see `UNIT_LABELS_EN`), so this is a whole-token
 * equality check (after stemming/normalizing), not the substring search
 * `matchIngredientName` does — `"cup"` shouldn't match inside an unrelated
 * longer word.
 */
export function matchUnit(unitText: string, catalog: UnitMatchEntry[]): number | null {
  const tokens = tokenize(unitText);
  if (tokens.length === 0) return null;
  const firstToken = tokens[0];

  for (const entry of catalog) {
    if (entry.synonyms.some((synonym) => stemWord(normalizeText(synonym)) === firstToken)) {
      return entry.unitId;
    }
  }
  return null;
}

/** What {@link extractQuantity} pulls out of a leading numeric expression, alongside what's left of the string after it. */
export interface ExtractedQuantity {
  quantity: number | null;
  /** `rawText` with the leading quantity (and any separating whitespace) removed — `rawText` unchanged if none was found. */
  remainder: string;
}

// Leading "1 1/2", "1/2", "1.5", "1,5" or "2" (optionally followed by a
// hyphenated range like "2-3", in which case only the first number counts —
// good enough for a best-effort quantity, not meant to model ranges.
const LEADING_QUANTITY_PATTERN = /^(\d+)\s+(\d+)\/(\d+)|^(\d+)\/(\d+)|^(\d+(?:[.,]\d+)?)/;

/**
 * Pulls a leading quantity off `rawText` (e.g. `"1 1/2 cups flour"` ->
 * `{ quantity: 1.5, remainder: "cups flour" }`), supporting a plain
 * integer/decimal, a simple fraction (`"1/2"`), or a mixed number
 * (`"1 1/2"`). `quantity: null` (remainder === rawText, trimmed) when
 * `rawText` doesn't start with a recognizable number — e.g. `"salt to
 * taste"`, which has none.
 */
export function extractQuantity(rawText: string): ExtractedQuantity {
  const trimmed = rawText.trim();
  const match = LEADING_QUANTITY_PATTERN.exec(trimmed);
  if (!match) return { quantity: null, remainder: trimmed };

  let quantity: number;
  if (match[1] !== undefined) {
    // Mixed number: "1 1/2".
    quantity = Number(match[1]) + Number(match[2]) / Number(match[3]);
  } else if (match[4] !== undefined) {
    // Simple fraction: "1/2".
    quantity = Number(match[4]) / Number(match[5]);
  } else {
    // Plain integer/decimal: "2" or "1.5"/"1,5" — group 6 is guaranteed
    // defined here (the only remaining alternative in the pattern), `?? ""`
    // is just satisfying the indexed-access type, not a real fallback.
    quantity = Number((match[6] ?? "").replace(",", "."));
  }

  return { quantity, remainder: trimmed.slice(match[0].length).trim() };
}

/** Loads the full `Ingredient` catalog as {@link IngredientMatchEntry}s — one entry per key with an authored English label (see `INGREDIENT_LABELS_EN`), plus one extra entry per alternate wording (`INGREDIENT_LABEL_SYNONYMS_EN`, e.g. "Vanilla pod" alongside "Vanilla bean" — see issue #54) sharing the same `ingredientId`; `matchIngredientName` doesn't need to know synonyms exist, it just sees more candidate labels for the same ingredient. An ingredient with no English label yet is silently skipped, never a matching target. Meant to be fetched once per request and reused across every ingredient line, not re-queried per line. */
export async function loadIngredientCatalog(): Promise<IngredientMatchEntry[]> {
  try {
    const ingredients = await prisma.ingredient.findMany({
      select: { id: true, key: true },
    });
    const catalog: IngredientMatchEntry[] = [];
    for (const ingredient of ingredients) {
      const label = INGREDIENT_LABELS_EN[ingredient.key];
      if (label === undefined) continue;
      catalog.push({ ingredientId: ingredient.id, label });
      for (const synonym of INGREDIENT_LABEL_SYNONYMS_EN[ingredient.key] ?? []) {
        catalog.push({ ingredientId: ingredient.id, label: synonym });
      }
    }
    return catalog;
  } catch (err) {
    // Rethrown as-is — the caller (`sources.service.ts`/`recipe-translation.ts`)
    // already handles/logs failures centrally; this function just isn't
    // allowed a bare `await` per the repo's async/try-catch convention.
    throw err;
  }
}

/** Loads the full `Unit` catalog as {@link UnitMatchEntry}s — one entry per key with authored English synonyms (see `UNIT_LABELS_EN`); a unit with none yet is silently skipped. Meant to be fetched once per request, same reasoning as {@link loadIngredientCatalog}. */
export async function loadUnitCatalog(): Promise<UnitMatchEntry[]> {
  try {
    const units = await prisma.unit.findMany({
      select: { id: true, key: true },
    });
    const catalog: UnitMatchEntry[] = [];
    for (const unit of units) {
      const synonyms = UNIT_LABELS_EN[unit.key];
      if (synonyms !== undefined) catalog.push({ unitId: unit.id, synonyms });
    }
    return catalog;
  } catch (err) {
    throw err; // see loadIngredientCatalog()'s catch comment above
  }
}