// scanner/scanCartella.js
const path = require('path');
const fsp = require('fs/promises');
const processFile = require('./processFile');
const { sha256 } = require('./utils');
const { SUPPORTED_EXTS } = require('../config');

async function* scanCartella(userName, cartella, absCartella, previousIndexTree) {

  async function* walk(currentAbs, relPath = '') {
    let entries = [];
    try {
      entries = await fsp.readdir(currentAbs, { withFileTypes: true });
    } catch {
      return;
    }

    for (const e of entries) {
      const absPath = path.join(currentAbs, e.name);

      if (e.isDirectory()) {
        yield* walk(absPath, path.join(relPath, e.name));
        continue;
      }

      const ext = path.extname(e.name).toLowerCase();
      if (!SUPPORTED_EXTS.has(ext)) continue;

      const fileRelPath = relPath ? `${relPath}/${e.name}` : e.name;
      const id = sha256(`${userName}/${cartella}/${fileRelPath}`);

      let st;
      try { st = await fsp.stat(absPath); } catch { continue; }

      const hash = sha256(`${st.size}-${st.mtimeMs}`);
      const prev = previousIndexTree?.[userName]?.[cartella]?.[id];

      // FILE INVARIATO
      if (prev && prev.hash === hash) {
        yield {
          id,
          user: userName,
          cartella,
          path: `/photos/${userName}/original/${cartella}/${fileRelPath}`,
          _indexHash: hash,
          unchanged: true
        };
        continue;
      }

      // FILE NUOVO/MODIFICATO
      const meta = await processFile(
        userName,
        cartella,
        fileRelPath,
        absPath,
        ext,
        st
      );

      meta.id = id;
      meta.path = `/photos/${userName}/original/${cartella}/${fileRelPath}`;
      meta._indexHash = hash;

      yield meta;
    }
  }

  yield* walk(absCartella);
}

module.exports = scanCartella;