// "Where else does this word appear?": every verse that uses a Strong's number, grouped by book. Built once, in
// memory, from the interlinear files the Reader already ships (public/interlinear, or dist/interlinear in a build),
// the first time anyone asks. Greek (G…) and Hebrew (H…) numbers both work.
import { existsSync } from 'fs';
import { readdir, readFile } from 'fs/promises';
import { fileURLToPath } from 'url';
import { dirname, join } from 'path';
import { bookNameFor } from './bibleApi.js';

const __dirname = dirname(fileURLToPath(import.meta.url));

// Strong's numbers come as "G4102", "g4102", "H7225" or sometimes with a letter suffix ("H1234a").
export function normalizeStrongs(input) {
  const m = String(input ?? '').trim().match(/^([GH])0*(\d{1,5})[a-z]?$/i);
  return m ? `${m[1].toUpperCase()}${Number(m[2])}` : null;
}

// One book's interlinear file -> adds each verse it uses a number in to the index (once per verse).
export function indexBook(index, book, data) {
  for (const [chapter, verses] of Object.entries(data ?? {})) {
    for (const [verse, words] of Object.entries(verses ?? {})) {
      const seen = new Set();
      for (const w of Array.isArray(words) ? words : []) {
        const s = normalizeStrongs(w?.s);
        if (!s || seen.has(s)) continue;
        seen.add(s);
        let entry = index.get(s);
        if (!entry) { entry = { count: 0, books: new Map() }; index.set(s, entry); }
        let refs = entry.books.get(book);
        if (!refs) { refs = []; entry.books.set(book, refs); }
        refs.push([Number(chapter), Number(verse)]);
        entry.count += 1;
      }
    }
  }
}

// The answer for one number: { strongs, total, books: [{ book, name, count, refs: [[chapter, verse], ...] }] },
// books in the order the index was built (Bible order when files are indexed in canon order).
export function occurrences(index, strongs) {
  const key = normalizeStrongs(strongs);
  const entry = key && index.get(key);
  if (!entry) return { strongs: key, total: 0, books: [] };
  const books = [...entry.books].map(([book, refs]) => ({
    book, name: bookNameFor(book) ?? book, count: refs.length,
    refs: refs.slice().sort((a, b) => a[0] - b[0] || a[1] - b[1]),
  }));
  return { strongs: key, total: entry.count, books };
}

// Canon order so the books come back Genesis → Revelation, whatever order the directory lists them.
const CANON = ['GEN','EXO','LEV','NUM','DEU','JOS','JDG','RUT','1SA','2SA','1KI','2KI','1CH','2CH','EZR','NEH','EST','JOB','PSA','PRO','ECC','SNG','ISA','JER','LAM','EZK','DAN','HOS','JOL','AMO','OBA','JON','MIC','NAM','HAB','ZEP','HAG','ZEC','MAL','MAT','MRK','LUK','JHN','ACT','ROM','1CO','2CO','GAL','EPH','PHP','COL','1TH','2TH','1TI','2TI','TIT','PHM','HEB','JAS','1PE','2PE','1JN','2JN','3JN','JUD','REV'];

export async function buildIndex(dir) {
  const index = new Map();
  const files = new Set(await readdir(dir));
  for (const book of CANON) {
    if (!files.has(`${book}.json`)) continue;
    try { indexBook(index, book, JSON.parse(await readFile(join(dir, `${book}.json`), 'utf8'))); } catch { /* a damaged file just leaves that book out */ }
  }
  return index;
}

function interlinearDir() {
  return [join(__dirname, '..', 'dist', 'interlinear'), join(__dirname, '..', 'public', 'interlinear')].find(existsSync) ?? null;
}

let pending = null;
const getIndex = () => {
  if (!pending) {
    const dir = interlinearDir();
    pending = (dir ? buildIndex(dir) : Promise.resolve(new Map())).catch((err) => { pending = null; throw err; });
  }
  return pending;
};

export function registerStrongsRoutes(app, requireAuth) {
  // GET /api/strongs/:number/occurrences
  app.get('/api/strongs/:number/occurrences', requireAuth, async (req, res) => {
    const key = normalizeStrongs(req.params.number);
    if (!key) return res.status(400).json({ error: 'Use a Strong’s number like G4102 or H7225.' });
    try {
      res.json(occurrences(await getIndex(), key));
    } catch (err) {
      console.error('GET /api/strongs occurrences error:', err);
      res.status(500).json({ error: 'Could not look up that word.' });
    }
  });
}