// scanner/scanPhoto.js
const path = require('path');
const fsp = require('fs/promises');
const { loadPreviousIndex, saveIndex } = require('./indexStore');
const scanUserRoot = require('./scanUser');
const postWithAuth = require('./postWithAuth');
const {
  WEB_ROOT,
  SEND_PHOTOS,
  BASE_URL,
  WRITE_INDEX,
} = require('../config');

const COMMON = 'Common'; // Nome canonico e case-sensitive per la shared folder

/**
 * Restituisce la prima directory esistente tra le candidate
 * @param {string[]} candidates
 * @returns {Promise<string|null>}
 */
async function firstExistingDir(candidates) {
  for (const dir of candidates) {
    try {
      const st = await fsp.stat(dir);
      if (st.isDirectory()) return dir;
    } catch { /* ignore */ }
  }
  return null;
}

/**
 * Scansione foto con indice separato:
 *  - Carica indice precedente (mappa { id: meta })
 *  - Produce SOLO i cambiamenti (nuovi/modificati)
 *  - Merge e salvataggio atomico dell'indice
 *  - POST verso /photos solo del delta (se abilitato)
 *  - Admin: include la cartella "Common"
 *
 * Nota path: usiamo un path ASSOLUTO per <root>/public/photos
 * partendo da .../api_v1/scanner -> '..', '..' per salire alla root del progetto.
 */
async function scanPhoto(dir, userName) {
  try {
    const previousIndexMap = await loadPreviousIndex();
    const nextIndexMap = { ...previousIndexMap };

    // Path assoluto alla radice photos (es: <root>/public/photos)
    const photosRoot = path.resolve(__dirname, '..', '..', WEB_ROOT, 'photos');

    let changes = [];

    if (userName === 'Admin') {
      // 1) Scansiona TUTTI gli utenti tranne la/e cartella/e common
      let entries = [];
      try {
        entries = await fsp.readdir(photosRoot, { withFileTypes: true });
      } catch (e) {
        console.error(`[SCAN] photosRoot non accessibile: ${photosRoot}`, e.message);
        entries = [];
      }

      for (const e of entries) {
        if (!e.isDirectory()) continue;
        // salta qualunque "common" (qualunque casing) per non doppiare
        if (e.name.toLowerCase() === COMMON.toLowerCase()) continue;

        const userDir = path.join(photosRoot, e.name, 'original');
        try {
          const st = await fsp.stat(userDir);
          if (!st.isDirectory()) continue;
        } catch {
          continue;
        }

        const userChanges = await scanUserRoot(e.name, userDir, previousIndexMap);
        for (const m of userChanges) nextIndexMap[m.id] = m;
        changes.push(...userChanges);
      }

      // 2) Scansiona la cartella COMMON (case strict), con fallback legacy (solo lettura) a 'common'
      const commonPreferred = path.join(photosRoot, COMMON, 'original');  // .../photos/Common/original
      const commonLegacy    = path.join(photosRoot, 'common', 'original'); // .../photos/common/original (legacy)

      const commonDir = await firstExistingDir([commonPreferred, commonLegacy]);
      if (commonDir) {
        // Forziamo SEMPRE userName = 'Common' per ID/thumbnails coerenti in 'Common'
        const commonChanges = await scanUserRoot(COMMON, commonDir, previousIndexMap);
        for (const m of commonChanges) nextIndexMap[m.id] = m;
        changes.push(...commonChanges);
        console.log(`[SCAN] Common indicizzati da ${commonDir}: +${commonChanges.length}`);
      } else {
        console.log(`[SCAN] Nessuna cartella "${COMMON}" trovata sotto ${photosRoot} (atteso: ${commonPreferred})`);
      }

    } else {
      // Non-Admin (per completezza; in server.js /scan è Admin-only)
      const userDir = path.join(photosRoot, userName, 'original');
      try {
        const st = await fsp.stat(userDir);
        if (st.isDirectory()) {
          const userChanges = await scanUserRoot(userName, userDir, previousIndexMap);
          for (const m of userChanges) nextIndexMap[m.id] = m;
          changes.push(...userChanges);
        }
      } catch {
        // utente senza dir 'original' -> nessuna modifica
      }
    }

    // Salva indice (mappa) in modo atomico
    if (WRITE_INDEX) {
      await saveIndex(nextIndexMap);
    }

    // POST solo dei cambiamenti (delta)
    if (SEND_PHOTOS && BASE_URL && changes.length) {
      for (const p of changes) {
        try {
          await postWithAuth(`${BASE_URL}/photos`, p);
        } catch (err) {
          console.error('Errore invio:', err.message);
        }
      }
    }

    console.log(`SCAN COMPLETATA per utente ${userName}: ${changes.length} file aggiornati`);
    return changes;
  } catch (e) {
    console.error('Errore generale scanPhoto:', e);
    throw e;
  }
}

module.exports = scanPhoto;