var Q = require('q');
var _ = require('underscore');

// Setup is called with the context of the current client.
exports.setup = function(Client, name, options) {
  if (!options.connection) {
    throw new Error('The database connection properties must be specified.');
  }
  this.name = name;
  this.debug = options.debug;
  this.connectionSettings = options.connection;
  this.grammar = Client.grammar;
  this.schemaGrammar = Client.schemaGrammar;

  // Extend the genericPool with the options
  // passed into the init under the "pool" option.
  var instance = this;
  this.pool = require('generic-pool').Pool(_.extend({
    name: 'pool-' + name,
    min: 2,
    max: 10,
    log: false,
    idleTimeoutMillis: 30000,
    create: function(callback) {
      var conn = instance.getRawConnection();
      conn.__cid = _.uniqueId('__cid');
      callback(null, conn);
    },
    destroy: function(client) { client.end(); }
  }, this.poolDefaults, options.pool));
};

exports.protoProps = {

  // Execute a query on the specified Builder or QueryBuilder
  // interface. If a `connection` is specified, use it, otherwise
  // acquire a connection, and then dispose of it when we're done.
  query: function(builder) {
    var emptyConnection = !builder._connection;
    var debug = this.debug || builder.debug;
    var instance = this;
    return Q((builder._connection || this.getConnection()))
      .then(function(conn) {
        var promise;

        // Prep the SQL associated with the builder.
        builder.sql = builder.toSql();
        builder.bindings = builder._cleanBindings();
        builder = instance.prepData(builder);
        
        // If we have a debug flag set, console.log the query.
        if (debug) console.log(_.extend(builder, {__cid: conn.__cid}));

        // If it's an array (in the case of schema builders), resolve with
        // all of the queries, called with the same connection, otherwise
        conn.query = _.bind(conn.query, conn);
        if (_.isArray(builder.sql)) {
          promise = Q.all(_.map(builder.sql, function(sql) {
            return Q.nfcall(conn.query, sql, (builder.bindings || [])); 
          }));
        } else {
          promise = Q.nfcall(conn.query, builder.sql, (builder.bindings || []));
        }

        // Empty the connection after we run the query, unless one was specifically
        // set (in the case of transactions, etc).
        return promise.fin(function() {
          if (emptyConnection) instance.pool.release(conn);
        });
      });
  },

  prepData: function(data) {
    return data;
  },

  prepResp: function(resp) {
    return resp;
  },

  // Retrieves a connection from the connection pool,
  // returning a promise.
  getConnection: function() {
    return Q.ninvoke(this.pool, 'acquire');
  },

  // Releases a connection from the connection pool,
  // returning a promise.
  releaseConnection: function(conn) {
    return Q.ninvoke(this.pool, 'release', conn);
  },

  // Begins a transaction statement on the instance,
  // resolving with the connection of the current transaction.
  startTransaction: function() {
    return this.getConnection().then(function(connection) {
      return Q.ninvoke(connection, 'query', 'begin;', []).then(function() {
        return connection;
      });
    });
  },

  finishTransaction: function(type, trans, dfd) {
    Q.ninvoke(trans.connection, 'query', type + ';', []).then(function() {
      if (type === 'commit') dfd.resolve(resp);
      if (type === 'rollback') dfd.reject(resp);
    }).fin(function() {
      trans.connection.end();
      trans.connection = null;
    });
  }

};

exports.grammar = {

};

exports.schemaGrammar = {
  
  // Compile a create table command.
  compileCreateTable: function(blueprint, command) {
    var columns = this.getColumns(blueprint).join(', ');
    return 'create table ' + this.wrapTable(blueprint) + ' (' + columns + ')';
  },

  // Compile a drop table command.
  compileDropTable: function(blueprint, command) {
    return 'drop table ' + this.wrapTable(blueprint);
  },

  // Compile a drop table (if exists) command.
  compileDropTableIfExists: function(blueprint, command) {
    return 'drop table if exists ' + this.wrapTable(blueprint);
  }

};