require 'active_record/connection_adapters/abstract_adapter'

module ActiveRecord
  class Base
    # Establishes a connection to the database that's used by all Active Record objects.
    def self.mysql_connection(config) # :nodoc:
      # Only include the MySQL driver if one hasn't already been loaded
      unless defined? Mysql
        begin
          require_library_or_gem 'mysql'
        rescue LoadError => cannot_require_mysql
          # Only use the supplied backup Ruby/MySQL driver if no driver is already in place
          begin
            require 'active_record/vendor/mysql'
          rescue LoadError
            raise cannot_require_mysql
          end
        end
      end


      config = config.symbolize_keys
      host     = config[:host]
      port     = config[:port]
      socket   = config[:socket]
      username = config[:username] ? config[:username].to_s : 'root'
      password = config[:password].to_s

      if config.has_key?(:database)
        database = config[:database]
      else
        raise ArgumentError, "No database specified. Missing argument: database."
      end

      mysql = Mysql.init
      mysql.ssl_set(config[:sslkey], config[:sslcert], config[:sslca], config[:sslcapath], config[:sslcipher]) if config[:sslkey]
      ConnectionAdapters::MysqlAdapter.new(mysql, logger, [host, username, password, database, port, socket], config)
    end
  end

  module ConnectionAdapters
    class MysqlColumn < Column #:nodoc:
      private
        def simplified_type(field_type)
          return :boolean if MysqlAdapter.emulate_booleans && field_type.downcase == "tinyint(1)"
          super
        end
    end

    # The MySQL adapter will work with both Ruby/MySQL, which is a Ruby-based MySQL adapter that comes bundled with Active Record, and with
    # the faster C-based MySQL/Ruby adapter (available both as a gem and from http://www.tmtm.org/en/mysql/ruby/).
    #
    # Options:
    #
    # * <tt>:host</tt> -- Defaults to localhost
    # * <tt>:port</tt> -- Defaults to 3306
    # * <tt>:socket</tt> -- Defaults to /tmp/mysql.sock
    # * <tt>:username</tt> -- Defaults to root
    # * <tt>:password</tt> -- Defaults to nothing
    # * <tt>:database</tt> -- The name of the database. No default, must be provided.
    # * <tt>:sslkey</tt> -- Necessary to use MySQL with an SSL connection
    # * <tt>:sslcert</tt> -- Necessary to use MySQL with an SSL connection
    # * <tt>:sslcapath</tt> -- Necessary to use MySQL with an SSL connection
    # * <tt>:sslcipher</tt> -- Necessary to use MySQL with an SSL connection
    #
    # By default, the MysqlAdapter will consider all columns of type tinyint(1)
    # as boolean. If you wish to disable this emulation (which was the default
    # behavior in versions 0.13.1 and earlier) you can add the following line
    # to your environment.rb file:
    #
    #   ActiveRecord::ConnectionAdapters::MysqlAdapter.emulate_booleans = false
    class MysqlAdapter < AbstractAdapter
      @@emulate_booleans = true
      cattr_accessor :emulate_booleans

      LOST_CONNECTION_ERROR_MESSAGES = [
        "Server shutdown in progress",
        "Broken pipe",
        "Lost connection to MySQL server during query",
        "MySQL server has gone away"
      ]

      def initialize(connection, logger, connection_options, config)
        super(connection, logger)
        @connection_options, @config = connection_options, config
        @null_values_in_each_hash = Mysql.const_defined?(:VERSION)
        connect
      end

      def adapter_name #:nodoc:
        'MySQL'
      end

      def supports_migrations? #:nodoc:
        true
      end

      def native_database_types #:nodoc
        {
          :primary_key => "int(11) DEFAULT NULL auto_increment PRIMARY KEY",
          :string      => { :name => "varchar", :limit => 255 },
          :text        => { :name => "text" },
          :integer     => { :name => "int", :limit => 11 },
          :float       => { :name => "float" },
          :datetime    => { :name => "datetime" },
          :timestamp   => { :name => "datetime" },
          :time        => { :name => "time" },
          :date        => { :name => "date" },
          :binary      => { :name => "blob" },
          :boolean     => { :name => "tinyint", :limit => 1 }
        }
      end


      # QUOTING ==================================================

      def quote(value, column = nil)
        if value.kind_of?(String) && column && column.type == :binary
          s = column.class.string_to_binary(value).unpack("H*")[0]
          "x'#{s}'"
        else
          super
        end
      end

      def quote_column_name(name) #:nodoc:
        "`#{name}`"
      end

      def quote_string(string) #:nodoc:
        @connection.quote(string)
      end

      def quoted_true
        "1"
      end
      
      def quoted_false
        "0"
      end


      # CONNECTION MANAGEMENT ====================================

      def active?
        if @connection.respond_to?(:stat)
          @connection.stat
        else
          @connection.query 'select 1'
        end

        # mysql-ruby doesn't raise an exception when stat fails.
        if @connection.respond_to?(:errno)
          @connection.errno.zero?
        else
          true
        end
      rescue Mysql::Error
        false
      end

      def reconnect!
        @connection.close rescue nil
        connect
      end


      # DATABASE STATEMENTS ======================================

      def select_all(sql, name = nil) #:nodoc:
        select(sql, name)
      end

      def select_one(sql, name = nil) #:nodoc:
        result = select(sql, name)
        result.nil? ? nil : result.first
      end

      def execute(sql, name = nil, retries = 2) #:nodoc:
        log(sql, name) { @connection.query(sql) }
      rescue ActiveRecord::StatementInvalid => exception
        if exception.message.split(":").first =~ /Packets out of order/
          raise ActiveRecord::StatementInvalid, "'Packets out of order' error was received from the database. Please update your mysql bindings (gem install mysql) and read http://dev.mysql.com/doc/mysql/en/password-hashing.html for more information.  If you're on Windows, use the Instant Rails installer to get the updated mysql bindings."
        else
          raise
        end
      end

      def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) #:nodoc:
        execute(sql, name = nil)
        id_value || @connection.insert_id
      end

      def update(sql, name = nil) #:nodoc:
        execute(sql, name)
        @connection.affected_rows
      end

      alias_method :delete, :update #:nodoc:


      def begin_db_transaction #:nodoc:
        execute "BEGIN"
      rescue Exception
        # Transactions aren't supported
      end

      def commit_db_transaction #:nodoc:
        execute "COMMIT"
      rescue Exception
        # Transactions aren't supported
      end

      def rollback_db_transaction #:nodoc:
        execute "ROLLBACK"
      rescue Exception
        # Transactions aren't supported
      end


      def add_limit_offset!(sql, options) #:nodoc
        if limit = options[:limit]
          unless offset = options[:offset]
            sql << " LIMIT #{limit}"
          else
            sql << " LIMIT #{offset}, #{limit}"
          end
        end
      end


      # SCHEMA STATEMENTS ========================================

      def structure_dump #:nodoc:
        select_all("SHOW TABLES").inject("") do |structure, table|
          structure += select_one("SHOW CREATE TABLE #{table.to_a.first.last}")["Create Table"] + ";\n\n"
        end
      end

      def recreate_database(name) #:nodoc:
        drop_database(name)
        create_database(name)
      end

      def create_database(name) #:nodoc:
        execute "CREATE DATABASE #{name}"
      end
      
      def drop_database(name) #:nodoc:
        execute "DROP DATABASE IF EXISTS #{name}"
      end


      def tables(name = nil) #:nodoc:
        tables = []
        execute("SHOW TABLES", name).each { |field| tables << field[0] }
        tables
      end

      def indexes(table_name, name = nil)#:nodoc:
        indexes = []
        current_index = nil
        execute("SHOW KEYS FROM #{table_name}", name).each do |row|
          if current_index != row[2]
            next if row[2] == "PRIMARY" # skip the primary key
            current_index = row[2]
            indexes << IndexDefinition.new(row[0], row[2], row[1] == "0", [])
          end

          indexes.last.columns << row[4]
        end
        indexes
      end

      def columns(table_name, name = nil)#:nodoc:
        sql = "SHOW FIELDS FROM #{table_name}"
        columns = []
        execute(sql, name).each { |field| columns << MysqlColumn.new(field[0], field[4], field[1], field[2] == "YES") }
        columns
      end

      def create_table(name, options = {}) #:nodoc:
        super(name, {:options => "ENGINE=InnoDB"}.merge(options))
      end
      
      def rename_table(name, new_name)
        execute "RENAME TABLE #{name} TO #{new_name}"
      end  

      def change_column_default(table_name, column_name, default) #:nodoc:
        current_type = select_one("SHOW COLUMNS FROM #{table_name} LIKE '#{column_name}'")["Type"]

        change_column(table_name, column_name, current_type, { :default => default })
      end

      def change_column(table_name, column_name, type, options = {}) #:nodoc:
        options[:default] ||= select_one("SHOW COLUMNS FROM #{table_name} LIKE '#{column_name}'")["Default"]
        
        change_column_sql = "ALTER TABLE #{table_name} CHANGE #{column_name} #{column_name} #{type_to_sql(type, options[:limit])}"
        add_column_options!(change_column_sql, options)
        execute(change_column_sql)
      end

      def rename_column(table_name, column_name, new_column_name) #:nodoc:
        current_type = select_one("SHOW COLUMNS FROM #{table_name} LIKE '#{column_name}'")["Type"]
        execute "ALTER TABLE #{table_name} CHANGE #{column_name} #{new_column_name} #{current_type}"
      end


      private
        def connect
          encoding = @config[:encoding]
          if encoding
            @connection.options(Mysql::SET_CHARSET_NAME, encoding) rescue nil
          end
          @connection.real_connect(*@connection_options)
          execute("SET NAMES '#{encoding}'") if encoding
        end

        def select(sql, name = nil)
          @connection.query_with_result = true
          result = execute(sql, name)
          rows = []
          if @null_values_in_each_hash
            result.each_hash { |row| rows << row }
          else
            all_fields = result.fetch_fields.inject({}) { |fields, f| fields[f.name] = nil; fields }
            result.each_hash { |row| rows << all_fields.dup.update(row) }
          end
          result.free
          rows
        end
    end
  end
end
