var EventEmitter = require('events').EventEmitter;

var defaults = require('./defaults');
var genericPool = require('generic-pool');


module.exports = function(Client) {
  var pools = {
    Client: Client,
    //dictionary of all key:pool pairs
    all: {},
    //reference to the client constructor - can override in tests or for require('pg').native
    getOrCreate: function(clientConfig) {
      clientConfig = clientConfig || {};
      var name = JSON.stringify(clientConfig);
      var pool = pools.all[name];
      if(pool) {
        return pool;
      }
      pool = genericPool.Pool({
        name: name,
        max: clientConfig.poolSize || defaults.poolSize,
        idleTimeoutMillis: clientConfig.poolIdleTimeout || defaults.poolIdleTimeout,
        reapIntervalMillis: clientConfig.reapIntervalMillis || defaults.reapIntervalMillis,
        returnToHead: clientConfig.returnToHead || defaults.returnToHead,
        log: clientConfig.poolLog || defaults.poolLog,
        create: function(cb) {
          var client = new pools.Client(clientConfig);
          // Ignore errors on pooled clients until they are connected.
          client.on('error', Function.prototype);
          client.connect(function(err) {
            if(err) return cb(err, null);

            // Remove the noop error handler after a connection has been established.
            client.removeListener('error', Function.prototype);

            //handle connected client background errors by emitting event
            //via the pg object and then removing errored client from the pool
            client.on('error', function(e) {
              pool.emit('error', e, client);

              // If the client is already being destroyed, the error
              // occurred during stream ending. Do not attempt to destroy
              // the client again.
              if (!client._destroying) {
                pool.destroy(client);
              }
            });

            // Remove connection from pool on disconnect
            client.on('end', function(e) {
              // Do not enter infinite loop between pool.destroy
              // and client 'end' event...
              if ( ! client._destroying ) {
                pool.destroy(client);
              }
            });
            client.poolCount = 0;
            return cb(null, client);
          });
        },
        destroy: function(client) {
          client._destroying = true;
          client.poolCount = undefined;
          client.end();
        }
      });
      pools.all[name] = pool;
      //mixin EventEmitter to pool
      EventEmitter.call(pool);
      for(var key in EventEmitter.prototype) {
        if(EventEmitter.prototype.hasOwnProperty(key)) {
          pool[key] = EventEmitter.prototype[key];
        }
      }
      //monkey-patch with connect method
      pool.connect = function(cb) {
        var domain = process.domain;
        pool.acquire(function(err, client) {
          if(domain) {
            cb = domain.bind(cb);
          }
          if(err)  return cb(err, null, function() {/*NOOP*/});
          client.poolCount++;
          cb(null, client, function(err) {
            if(err) {
              pool.destroy(client);
            } else {
              pool.release(client);
            }
          });
        });
      };
      return pool;
    }
  };

  return pools;
};