(function () {
  'use strict';

  var DB_NAME = 'soondesign_local';
  var DB_VERSION = 1;
  var MAX_BLOBS = 20;
  var THUMB_MAX_BYTES = 102400;
  var dbPromise = null;
  var idbAvailable = typeof indexedDB !== 'undefined';

  function soonExtractThumbFromJson(json) {
    if (!json || !json.frontDisplayPic || typeof json.frontDisplayPic !== 'string') return '';
    var candidate = json.frontDisplayPic.trim();
    if (candidate.indexOf('data:image/') !== 0) return '';
    if (candidate.length > THUMB_MAX_BYTES) return '';
    return candidate;
  }

  function txDone(tx) {
    return new Promise(function (resolve, reject) {
      tx.oncomplete = function () { resolve(); };
      tx.onerror = function () { reject(tx.error || new Error('idb_tx_error')); };
      tx.onabort = function () { reject(tx.error || new Error('idb_tx_abort')); };
    });
  }

  function reqPromise(req) {
    return new Promise(function (resolve, reject) {
      req.onsuccess = function () { resolve(req.result); };
      req.onerror = function () { reject(req.error || new Error('idb_req_error')); };
    });
  }

  function soonLocalOpen() {
    if (!idbAvailable) return Promise.resolve(null);
    if (dbPromise) return dbPromise;
    dbPromise = new Promise(function (resolve, reject) {
      var req = indexedDB.open(DB_NAME, DB_VERSION);
      req.onupgradeneeded = function (e) {
        var db = e.target.result;
        if (!db.objectStoreNames.contains('blobs')) {
          db.createObjectStore('blobs', { keyPath: 'cacheKey' });
        }
        if (!db.objectStoreNames.contains('thumbs')) {
          db.createObjectStore('thumbs', { keyPath: 'cacheKey' });
        }
      };
      req.onsuccess = function () { resolve(req.result); };
      req.onerror = function () {
        idbAvailable = false;
        dbPromise = null;
        reject(req.error || new Error('idb_open_failed'));
      };
    }).catch(function () {
      idbAvailable = false;
      dbPromise = null;
      return null;
    });
    return dbPromise;
  }

  function soonLocalGet(cacheKey) {
    if (!cacheKey || !idbAvailable) return Promise.resolve(null);
    return soonLocalOpen().then(function (db) {
      if (!db) return null;
      var tx = db.transaction('blobs', 'readonly');
      return reqPromise(tx.objectStore('blobs').get(cacheKey)).then(function (row) {
        if (!row || row.json == null) return null;
        return {
          json: row.json,
          meta: {
            name: row.name,
            type: row.type,
            source: row.source,
            updatedAt: row.updatedAt,
            savedAt: row.savedAt,
            bytes: row.bytes
          }
        };
      });
    }).catch(function () { return null; });
  }

  function soonLocalEvictLRU(max) {
    max = max || MAX_BLOBS;
    return soonLocalOpen().then(function (db) {
      if (!db) return;
      var tx = db.transaction(['blobs', 'thumbs'], 'readwrite');
      var blobStore = tx.objectStore('blobs');
      return reqPromise(blobStore.getAll()).then(function (rows) {
        if (!rows || rows.length <= max) return txDone(tx);
        rows.sort(function (a, b) { return (a.savedAt || 0) - (b.savedAt || 0); });
        var toRemove = rows.length - max;
        for (var i = 0; i < toRemove; i++) {
          var k = rows[i].cacheKey;
          blobStore.delete(k);
          tx.objectStore('thumbs').delete(k);
        }
        return txDone(tx);
      });
    }).catch(function () { /* ignore */ });
  }

  function soonLocalPut(cacheKey, json, meta) {
    if (!cacheKey || json == null || !idbAvailable) return Promise.resolve(false);
    meta = meta || {};
    var jsonObj = typeof json === 'string' ? (function () {
      try { return JSON.parse(json); } catch (e) { return null; }
    })() : json;
    if (!jsonObj) return Promise.resolve(false);
    var bytes = 0;
    try { bytes = JSON.stringify(jsonObj).length; } catch (e) { bytes = 0; }
    var row = {
      cacheKey: cacheKey,
      json: jsonObj,
      name: meta.name || '',
      type: meta.type != null ? meta.type : (jsonObj.soonType || 1),
      source: meta.source || '',
      updatedAt: meta.updatedAt || '',
      savedAt: Date.now(),
      bytes: bytes
    };
    return soonLocalOpen().then(function (db) {
      if (!db) return false;
      var tx = db.transaction('blobs', 'readwrite');
      tx.objectStore('blobs').put(row);
      return txDone(tx).then(function () {
        return soonLocalEvictLRU(MAX_BLOBS).then(function () { return true; });
      });
    }).catch(function () { return false; });
  }

  function soonLocalPutThumb(cacheKey, dataUrl) {
    if (!cacheKey || !dataUrl || !idbAvailable) return Promise.resolve(false);
    if (String(dataUrl).length > THUMB_MAX_BYTES) return Promise.resolve(false);
    return soonLocalOpen().then(function (db) {
      if (!db) return false;
      var tx = db.transaction('thumbs', 'readwrite');
      tx.objectStore('thumbs').put({ cacheKey: cacheKey, dataUrl: dataUrl, savedAt: Date.now() });
      return txDone(tx).then(function () { return true; });
    }).catch(function () { return false; });
  }

  function soonLocalGetThumb(cacheKey) {
    if (!cacheKey || !idbAvailable) return Promise.resolve('');
    return soonLocalOpen().then(function (db) {
      if (!db) return '';
      var tx = db.transaction('thumbs', 'readonly');
      return reqPromise(tx.objectStore('thumbs').get(cacheKey)).then(function (row) {
        return (row && row.dataUrl) ? row.dataUrl : '';
      });
    }).catch(function () { return ''; });
  }

  function soonLocalRemove(cacheKey) {
    if (!cacheKey || !idbAvailable) return Promise.resolve();
    return soonLocalOpen().then(function (db) {
      if (!db) return;
      var tx = db.transaction(['blobs', 'thumbs'], 'readwrite');
      tx.objectStore('blobs').delete(cacheKey);
      tx.objectStore('thumbs').delete(cacheKey);
      return txDone(tx);
    }).catch(function () { /* ignore */ });
  }

  function soonLocalRenameKey(oldKey, newKey, meta) {
    if (!oldKey || !newKey || oldKey === newKey) return Promise.resolve(false);
    return soonLocalGet(oldKey).then(function (hit) {
      if (!hit) return false;
      return soonLocalPut(newKey, hit.json, Object.assign({}, hit.meta, meta || {})).then(function (ok) {
        if (!ok) return false;
        return soonLocalGetThumb(oldKey).then(function (thumb) {
          var chain = Promise.resolve();
          if (thumb) chain = soonLocalPutThumb(newKey, thumb);
          return chain.then(function () { return soonLocalRemove(oldKey); }).then(function () { return true; });
        });
      });
    }).catch(function () { return false; });
  }

  function soonLocalCacheAndThumb(cacheKey, json, meta) {
    var thumb = soonExtractThumbFromJson(json);
    return soonLocalPut(cacheKey, json, meta).then(function (ok) {
      if (!ok) return false;
      if (thumb) return soonLocalPutThumb(cacheKey, thumb).then(function () { return true; });
      return true;
    });
  }

  function soonLocalIsTemplateStale(cacheKey, blobMeta) {
    if (!cacheKey || cacheKey.indexOf('soondesign_template:') !== 0) return false;
    var tplMeta = window._soonTemplateMeta;
    if (!tplMeta || !tplMeta.updated_at) return false;
    if (!blobMeta || !blobMeta.updatedAt) return false;
    return String(tplMeta.updated_at) !== String(blobMeta.updatedAt);
  }

  window.soonLocalOpen = soonLocalOpen;
  window.soonLocalGet = soonLocalGet;
  window.soonLocalPut = soonLocalPut;
  window.soonLocalPutThumb = soonLocalPutThumb;
  window.soonLocalGetThumb = soonLocalGetThumb;
  window.soonLocalRemove = soonLocalRemove;
  window.soonLocalRenameKey = soonLocalRenameKey;
  window.soonLocalEvictLRU = soonLocalEvictLRU;
  window.soonLocalCacheAndThumb = soonLocalCacheAndThumb;
  window.soonLocalIsTemplateStale = soonLocalIsTemplateStale;
  window.soonExtractThumbFromJson = soonExtractThumbFromJson;

  var LS_DROP = ['soondesign_recent', 'soondesign_history', 'soondesign_recent_migrated'];
  var SS_DROP = ['soondesign_open_file', 'soondesign_open_type', 'soondesign_open_meta', 'soondesign_pending_import'];

  function dropStorageKeys(storage, prefix) {
    if (!storage) return;
    try {
      var rm = [];
      for (var i = 0; i < storage.length; i++) {
        var k = storage.key(i);
        if (k && k.indexOf(prefix) === 0) rm.push(k);
      }
      rm.forEach(function (k) { storage.removeItem(k); });
    } catch (e) { /* ignore */ }
  }

  function soonClearLocalDesignCache() {
    try {
      LS_DROP.forEach(function (k) { localStorage.removeItem(k); });
      dropStorageKeys(localStorage, 'soondesign_session:');
      SS_DROP.forEach(function (k) { sessionStorage.removeItem(k); });
      dropStorageKeys(sessionStorage, 'soondesign_session:');
    } catch (e) { /* ignore */ }
    dbPromise = null;
    if (typeof indexedDB === 'undefined') return Promise.resolve();
    return new Promise(function (resolve) {
      var done = function () { resolve(); };
      try {
        var req = indexedDB.deleteDatabase(DB_NAME);
        req.onsuccess = req.onerror = req.onblocked = done;
      } catch (e2) { done(); }
    });
  }

  window.soonClearLocalDesignCache = soonClearLocalDesignCache;
})();