"use strict";

var PouchDB = require("./constructor");
var utils = require('./utils');
var Promise = utils.Promise;
var EventEmitter = require('events').EventEmitter;
PouchDB.adapters = {};
PouchDB.preferredAdapters = require('./adapters/preferredAdapters.js');

PouchDB.prefix = '_pouch_';

var eventEmitter = new EventEmitter();

var eventEmitterMethods = [
  'on',
  'addListener',
  'emit',
  'listeners',
  'once',
  'removeAllListeners',
  'removeListener',
  'setMaxListeners'
];

eventEmitterMethods.forEach(function (method) {
  PouchDB[method] = eventEmitter[method].bind(eventEmitter);
});
PouchDB.setMaxListeners(0);
PouchDB.parseAdapter = function (name, opts) {
  var match = name.match(/([a-z\-]*):\/\/(.*)/);
  var adapter, adapterName;
  if (match) {
    // the http adapter expects the fully qualified name
    name = /http(s?)/.test(match[1]) ? match[1] + '://' + match[2] : match[2];
    adapter = match[1];
    if (!PouchDB.adapters[adapter].valid()) {
      throw 'Invalid adapter';
    }
    return {name: name, adapter: match[1]};
  }

  // check for browsers that have been upgraded from websql-only to websql+idb
  var skipIdb = 'idb' in PouchDB.adapters && 'websql' in PouchDB.adapters &&
    utils.hasLocalStorage() &&
    global.localStorage['_pouch__websqldb_' + PouchDB.prefix + name];

  if (typeof opts !== 'undefined' && opts.db) {
    adapterName = 'leveldb';
  } else {
    for (var i = 0; i < PouchDB.preferredAdapters.length; ++i) {
      adapterName = PouchDB.preferredAdapters[i];
      if (adapterName in PouchDB.adapters) {
        if (skipIdb && adapterName === 'idb') {
          continue; // keep using websql to avoid user data loss
        }
        break;
      }
    }
  }

  adapter = PouchDB.adapters[adapterName];
  if (adapterName && adapter) {
    var use_prefix = 'use_prefix' in adapter ? adapter.use_prefix : true;

    return {
      name: use_prefix ? PouchDB.prefix + name : name,
      adapter: adapterName
    };
  }

  throw 'No valid adapter found';
};

PouchDB.destroy = utils.toPromise(function (name, opts, callback) {
  if (typeof opts === 'function' || typeof opts === 'undefined') {
    callback = opts;
    opts = {};
  }

  if (name && typeof name === 'object') {
    opts = name;
    name = undefined;
  }

  var backend = PouchDB.parseAdapter(opts.name || name, opts);
  var dbName = backend.name;
  var fullName = (opts.prefix || '') + dbName;
  
  var adapter = PouchDB.adapters[backend.adapter];

  function destroyDb() {
    // call destroy method of the particular adaptor
    adapter.destroy(fullName, opts, function (err, resp) {
      if (err) {
        callback(err);
      } else {
        PouchDB.emit('destroyed', name);
        //so we don't have to sift through all dbnames
        PouchDB.emit(name, 'destroyed');
        callback(null, resp || { 'ok': true });
      }
    });
  }

  var usePrefix = 'use_prefix' in adapter ? adapter.use_prefix : true;

  var trueDbName = usePrefix ?
    dbName.replace(new RegExp('^' + PouchDB.prefix), '') : dbName;
  var createOpts = utils.extend(true, opts, {adapter : backend.adapter});
  new PouchDB(trueDbName, createOpts, function (err, db) {
    if (err) {
      return callback(err);
    }
    db.get('_local/_pouch_dependentDbs', function (err, localDoc) {
      if (err) {
        if (err.name !== 'not_found') {
          return callback(err);
        } else { // no dependencies
          return destroyDb();
        }
      }
      var dependentDbs = localDoc.dependentDbs;
      var deletedMap = Object.keys(dependentDbs).map(function (name) {
        var trueName = usePrefix ?
          name.replace(new RegExp('^' + PouchDB.prefix), '') : name;
        var subOpts = utils.extend(true, opts, {adapter: backend.adapter});
        return PouchDB.destroy(trueName, subOpts);
      });
      Promise.all(deletedMap).then(destroyDb, function (error) {
        callback(error);
      });
    });
  });
});

PouchDB.allDbs = utils.toPromise(function (callback) {
  var err = new Error('allDbs method removed');
  err.stats = '400';
  callback(err);
});
PouchDB.adapter = function (id, obj) {
  if (obj.valid()) {
    PouchDB.adapters[id] = obj;
  }
};

PouchDB.plugin = function (obj) {
  Object.keys(obj).forEach(function (id) {
    PouchDB.prototype[id] = obj[id];
  });
};

PouchDB.defaults = function (defaultOpts) {
  defaultOpts = utils.clone(defaultOpts);

  function PouchAlt(name, opts, callback) {
    if (typeof opts === 'function' || typeof opts === 'undefined') {
      callback = opts;
      opts = {};
    }
    if (name && typeof name === 'object') {
      opts = name;
      name = undefined;
    }

    opts = utils.extend(true, defaultOpts, opts);
    PouchDB.call(this, name, opts, callback);
  }

  utils.inherits(PouchAlt, PouchDB);

  PouchAlt.destroy = utils.toPromise(function (name, opts, callback) {
    if (typeof opts === 'function' || typeof opts === 'undefined') {
      callback = opts;
      opts = {};
    }

    if (name && typeof name === 'object') {
      opts = name;
      name = undefined;
    }

    opts = utils.extend(true, defaultOpts, opts);
    return PouchDB.destroy(name, opts, callback);
  });

  eventEmitterMethods.forEach(function (method) {
    PouchAlt[method] = eventEmitter[method].bind(eventEmitter);
  });
  PouchAlt.setMaxListeners(0);

  PouchAlt.preferredAdapters = PouchDB.preferredAdapters.slice();
  Object.keys(PouchDB).forEach(function (key) {
    if (!(key in PouchAlt)) {
      PouchAlt[key] = PouchDB[key];
    }
  });

  return PouchAlt;
};

module.exports = PouchDB;