Sequel.require %w'shared/mysql utils/stored_procedures', 'adapters'

module Sequel
  module MySQL
    # This module is used by the mysql and mysql2 adapters to support
    # prepared statements and stored procedures.
    module PreparedStatements
      module DatabaseMethods
        # Support stored procedures on MySQL
        def call_sproc(name, opts={}, &block)
          args = opts[:args] || [] 
          execute("CALL #{name}#{args.empty? ? '()' : literal(args)}", opts.merge(:sproc=>false), &block)
        end
        
        # Executes the given SQL using an available connection, yielding the
        # connection if the block is given.
        def execute(sql, opts={}, &block)
          if opts[:sproc]
            call_sproc(sql, opts, &block)
          elsif sql.is_a?(Symbol)
            execute_prepared_statement(sql, opts, &block)
          else
            synchronize(opts[:server]){|conn| _execute(conn, sql, opts, &block)}
          end
        end
        
        private

        def add_prepared_statements_cache(conn)
          class << conn
            attr_accessor :prepared_statements
          end
          conn.prepared_statements = {}
        end

        # Executes a prepared statement on an available connection.  If the
        # prepared statement already exists for the connection and has the same
        # SQL, reuse it, otherwise, prepare the new statement.  Because of the
        # usual MySQL stupidity, we are forced to name arguments via separate
        # SET queries.  Use @sequel_arg_N (for N starting at 1) for these
        # arguments.
        def execute_prepared_statement(ps_name, opts, &block)
          args = opts[:arguments]
          ps = prepared_statements[ps_name]
          sql = ps.prepared_sql
          synchronize(opts[:server]) do |conn|
            unless conn.prepared_statements[ps_name] == sql
              conn.prepared_statements[ps_name] = sql
              _execute(conn, "PREPARE #{ps_name} FROM #{literal(sql)}", opts)
            end
            i = 0
            _execute(conn, "SET " + args.map {|arg| "@sequel_arg_#{i+=1} = #{literal(arg)}"}.join(", "), opts) unless args.empty?
            _execute(conn, "EXECUTE #{ps_name}#{" USING #{(1..i).map{|j| "@sequel_arg_#{j}"}.join(', ')}" unless i == 0}", opts, &block)
          end
        end
        
      end
      module DatasetMethods
        include Sequel::Dataset::StoredProcedures
       
        # Methods to add to MySQL prepared statement calls without using a
        # real database prepared statement and bound variables.
        module CallableStatementMethods
          # Extend given dataset with this module so subselects inside subselects in
          # prepared statements work.
          def subselect_sql_append(sql, ds)
            ps = ds.to_prepared_statement(:select).clone(:append_sql => sql)
            ps.extend(CallableStatementMethods)
            ps = ps.bind(@opts[:bind_vars]) if @opts[:bind_vars]
            ps.prepared_args = prepared_args
            ps.prepared_sql
          end
        end
        
        # Methods for MySQL prepared statements using the native driver.
        module PreparedStatementMethods
          include Sequel::Dataset::UnnumberedArgumentMapper
          
          # Raise a more obvious error if you attempt to call a unnamed prepared statement.
          def call(*)
            raise Error, "Cannot call prepared statement without a name" if prepared_statement_name.nil?
            super
          end
          
          private
          
          # Execute the prepared statement with the bind arguments instead of
          # the given SQL.
          def execute(sql, opts={}, &block)
            super(prepared_statement_name, {:arguments=>bind_arguments}.merge(opts), &block)
          end
          
          # Same as execute, explicit due to intricacies of alias and super.
          def execute_dui(sql, opts={}, &block)
            super(prepared_statement_name, {:arguments=>bind_arguments}.merge(opts), &block)
          end
        end
        
        # Methods for MySQL stored procedures using the native driver.
        module StoredProcedureMethods
          include Sequel::Dataset::StoredProcedureMethods
          
          private
          
          # Execute the database stored procedure with the stored arguments.
          def execute(sql, opts={}, &block)
            super(@sproc_name, {:args=>@sproc_args, :sproc=>true}.merge(opts), &block)
          end
          
          # Same as execute, explicit due to intricacies of alias and super.
          def execute_dui(sql, opts={}, &block)
            super(@sproc_name, {:args=>@sproc_args, :sproc=>true}.merge(opts), &block)
          end
        end
        
        # MySQL is different in that it supports prepared statements but not bound
        # variables outside of prepared statements.  The default implementation
        # breaks the use of subselects in prepared statements, so extend the
        # temporary prepared statement that this creates with a module that
        # fixes it.
        def call(type, bind_arguments={}, *values, &block)
          ps = to_prepared_statement(type, values)
          ps.extend(CallableStatementMethods)
          ps.call(bind_arguments, &block)
        end
        
        # Store the given type of prepared statement in the associated database
        # with the given name.
        def prepare(type, name=nil, *values)
          ps = to_prepared_statement(type, values)
          ps.extend(PreparedStatementMethods)
          if name
            ps.prepared_statement_name = name
            db.prepared_statements[name] = ps
          end
          ps
        end
        
        private

        # Extend the dataset with the MySQL stored procedure methods.
        def prepare_extend_sproc(ds)
          ds.extend(StoredProcedureMethods)
        end
        
      end
    end
  end
end