function toArray(arr) {
  return Array.prototype.slice.call(arr);
}

function promisifyRequest(request) {
  return new Promise(function(resolve, reject) {
    request.onsuccess = function() {
      resolve(request.result);
    };

    request.onerror = function() {
      reject(request.error);
    };
  });
}

function promisifyRequestCall(obj, method, args) {
  var request;
  var p = new Promise(function(resolve, reject) {
    request = obj[method].apply(obj, args);
    promisifyRequest(request).then(resolve, reject);
  });

  p.request = request;
  return p;
}

function promisifyCursorRequestCall(obj, method, args) {
  var p = promisifyRequestCall(obj, method, args);
  return p.then(function(value) {
    if (!value) return;
    return new Cursor(value, p.request);
  });
}

function proxyProperties(ProxyClass, targetProp, properties) {
  properties.forEach(function(prop) {
    Object.defineProperty(ProxyClass.prototype, prop, {
      get: function() {
        return this[targetProp][prop];
      },
      set: function(val) {
        this[targetProp][prop] = val;
      }
    });
  });
}

function proxyRequestMethods(ProxyClass, targetProp, Constructor, properties) {
  properties.forEach(function(prop) {
    if (!(prop in Constructor.prototype)) return;
    ProxyClass.prototype[prop] = function() {
      return promisifyRequestCall(this[targetProp], prop, arguments);
    };
  });
}

function proxyMethods(ProxyClass, targetProp, Constructor, properties) {
  properties.forEach(function(prop) {
    if (!(prop in Constructor.prototype)) return;
    ProxyClass.prototype[prop] = function() {
      return this[targetProp][prop].apply(this[targetProp], arguments);
    };
  });
}

function proxyCursorRequestMethods(ProxyClass, targetProp, Constructor, properties) {
  properties.forEach(function(prop) {
    if (!(prop in Constructor.prototype)) return;
    ProxyClass.prototype[prop] = function() {
      return promisifyCursorRequestCall(this[targetProp], prop, arguments);
    };
  });
}

function Index(index) {
  this._index = index;
}

proxyProperties(Index, '_index', [
  'name',
  'keyPath',
  'multiEntry',
  'unique'
]);

proxyRequestMethods(Index, '_index', IDBIndex, [
  'get',
  'getKey',
  'getAll',
  'getAllKeys',
  'count'
]);

proxyCursorRequestMethods(Index, '_index', IDBIndex, [
  'openCursor',
  'openKeyCursor'
]);

function Cursor(cursor, request) {
  this._cursor = cursor;
  this._request = request;
}

proxyProperties(Cursor, '_cursor', [
  'direction',
  'key',
  'primaryKey',
  'value'
]);

proxyRequestMethods(Cursor, '_cursor', IDBCursor, [
  'update',
  'delete'
]);

// proxy 'next' methods
['advance', 'continue', 'continuePrimaryKey'].forEach(function(methodName) {
  if (!(methodName in IDBCursor.prototype)) return;
  Cursor.prototype[methodName] = function() {
    var cursor = this;
    var args = arguments;
    return Promise.resolve().then(function() {
      cursor._cursor[methodName].apply(cursor._cursor, args);
      return promisifyRequest(cursor._request).then(function(value) {
        if (!value) return;
        return new Cursor(value, cursor._request);
      });
    });
  };
});

function ObjectStore(store) {
  this._store = store;
}

ObjectStore.prototype.createIndex = function() {
  return new Index(this._store.createIndex.apply(this._store, arguments));
};

ObjectStore.prototype.index = function() {
  return new Index(this._store.index.apply(this._store, arguments));
};

proxyProperties(ObjectStore, '_store', [
  'name',
  'keyPath',
  'indexNames',
  'autoIncrement'
]);

proxyRequestMethods(ObjectStore, '_store', IDBObjectStore, [
  'put',
  'add',
  'delete',
  'clear',
  'get',
  'getAll',
  'getKey',
  'getAllKeys',
  'count'
]);

proxyCursorRequestMethods(ObjectStore, '_store', IDBObjectStore, [
  'openCursor',
  'openKeyCursor'
]);

proxyMethods(ObjectStore, '_store', IDBObjectStore, [
  'deleteIndex'
]);

function Transaction(idbTransaction) {
  this._tx = idbTransaction;
  this.complete = new Promise(function(resolve, reject) {
    idbTransaction.oncomplete = function() {
      resolve();
    };
    idbTransaction.onerror = function() {
      reject(idbTransaction.error);
    };
    idbTransaction.onabort = function() {
      reject(idbTransaction.error);
    };
  });
}

Transaction.prototype.objectStore = function() {
  return new ObjectStore(this._tx.objectStore.apply(this._tx, arguments));
};

proxyProperties(Transaction, '_tx', [
  'objectStoreNames',
  'mode'
]);

proxyMethods(Transaction, '_tx', IDBTransaction, [
  'abort'
]);

function UpgradeDB(db, oldVersion, transaction) {
  this._db = db;
  this.oldVersion = oldVersion;
  this.transaction = new Transaction(transaction);
}

UpgradeDB.prototype.createObjectStore = function() {
  return new ObjectStore(this._db.createObjectStore.apply(this._db, arguments));
};

proxyProperties(UpgradeDB, '_db', [
  'name',
  'version',
  'objectStoreNames'
]);

proxyMethods(UpgradeDB, '_db', IDBDatabase, [
  'deleteObjectStore',
  'close'
]);

function DB(db) {
  this._db = db;
}

DB.prototype.transaction = function() {
  return new Transaction(this._db.transaction.apply(this._db, arguments));
};

proxyProperties(DB, '_db', [
  'name',
  'version',
  'objectStoreNames'
]);

proxyMethods(DB, '_db', IDBDatabase, [
  'close'
]);

// Add cursor iterators
// TODO: remove this once browsers do the right thing with promises
['openCursor', 'openKeyCursor'].forEach(function(funcName) {
  [ObjectStore, Index].forEach(function(Constructor) {
    // Don't create iterateKeyCursor if openKeyCursor doesn't exist.
    if (!(funcName in Constructor.prototype)) return;

    Constructor.prototype[funcName.replace('open', 'iterate')] = function() {
      var args = toArray(arguments);
      var callback = args[args.length - 1];
      var nativeObject = this._store || this._index;
      var request = nativeObject[funcName].apply(nativeObject, args.slice(0, -1));
      request.onsuccess = function() {
        callback(request.result);
      };
    };
  });
});

// polyfill getAll
[Index, ObjectStore].forEach(function(Constructor) {
  if (Constructor.prototype.getAll) return;
  Constructor.prototype.getAll = function(query, count) {
    var instance = this;
    var items = [];

    return new Promise(function(resolve) {
      instance.iterateCursor(query, function(cursor) {
        if (!cursor) {
          resolve(items);
          return;
        }
        items.push(cursor.value);

        if (count !== undefined && items.length == count) {
          resolve(items);
          return;
        }
        cursor.continue();
      });
    });
  };
});

export function openDb(name, version, upgradeCallback) {
  var p = promisifyRequestCall(indexedDB, 'open', [name, version]);
  var request = p.request;

  if (request) {
    request.onupgradeneeded = function(event) {
      if (upgradeCallback) {
        upgradeCallback(new UpgradeDB(request.result, event.oldVersion, request.transaction));
      }
    };
  }

  return p.then(function(db) {
    return new DB(db);
  });
}

export function deleteDb(name) {
  return promisifyRequestCall(indexedDB, 'deleteDatabase', [name]);
}