require "open3"

module Buildr
  module Derby
    REQUIRES = group("derby", "derbytools", :under=>"org.apache.derby", :version=>"10.1.2.1")

    class << self

      # Returns a task that will create a new Derby database. The task name is the path to
      # the derby database. The prerequisites are all the SQL files for inclusion in the database.
      #
      # For example:
      #   Derby.create "mydb"=>derby.sql
      def create(args)
        db, prereqs = Rake.application.resolve_args(args)
        # Copy the SQL files into the database directory.
        file(File.expand_path(db)=>prereqs) do |task|
          cmd = [ Java.path_to_bin('java'), "-cp", requires, "org.apache.derby.tools.ij" ]
          Open3.popen3(*cmd) do |stdin, stdout, stderr|
            # Shutdown so if a database already exists, we can remove it.
            stdin.puts "connect 'jdbc:derby:;shutdown=true';"
            rm_rf task.name if File.exist?(task.name)
            # Create a new database, and load all the prerequisites.
            stdin.puts "connect 'jdbc:derby:#{task.to_s};create=true;user=sa'"
            stdin.puts "set schema sa"
            stdin.puts "autocommit on;"
            task.prerequisites.each { |prereq| stdin.write File.read(prereq.to_s) }
            # Exiting will shutdown the database so we can copy the files around.
            stdin.puts "exit"
            stdin.close
            # Helps when dignosing SQL errors.
            stdout.read.tap { |output| puts output if Rake.application.options.trace }
          end
          filter(prereqs).into(task.name).run
          touch task.name, :verbose=>false
        end
      end

    protected

      # This will download all the required artifacts before returning a classpath, and we want to do this only once.
      def requires()
        @requires ||= artifacts(REQUIRES).each(&:invoke).map(&:to_s).join(File::PATH_SEPARATOR)
      end
    end
  end
end