module Neo4j

  module Migrations

    # This is the context in which the Migrations DSL are evaluated in.
    # This class is also responsible for running the migrations.
    class Migration
      attr_reader :up_block, :down_block, :up_migrator, :down_migrator, :version, :name

      def initialize(version, name)
        @auto_transaction = true
        @version = version
        @name = name
      end

      # Specifies a code block which is run when the migration is upgraded.
      #
      def up(&block)
        @up_block = block
      end

      # Specifies a code block which is run when the migration is upgraded.
      #
      def down(&block)
        @down_block = block
      end

      # Specifies if transaction should automatically be created (default)
      def auto_transaction(run_with_auto_tx)
        @auto_transaction = run_with_auto_tx
      end


      # Specifies which fields should be indexed
      def add_index(*fields)
        @add_indexed_field = fields
      end

      # Specifies which fields indexed should be removed
      def rm_index(*fields)
        @rm_indexed_field = fields
      end

      # Runs the up migration. If successful it will set the property
      # ':_db_version' on the given context.
      #
      # === Parameters
      # context:: the context on which the block is evaluated in
      # meta_node:: the node on which to set the 'db_version' property
      #
      def execute_up(context, meta_node)

        if @auto_transaction
          Neo4j::Transaction.run do
            context.instance_eval &@up_block if @up_block
            add_index_on(context, @add_indexed_field) if @add_indexed_field
            rm_index_on(context, @rm_indexed_field) if @rm_indexed_field
            meta_node._java_node[:_db_version] = version # use the raw java node since Neo4j::Rails::Mode wraps it
          end
        else
          context.instance_eval &@up_block if @up_block
          add_index_on(context, @add_indexed_field) if @add_indexed_field
          Neo4j::Transaction.run do
            rm_index_on(context, @rm_indexed_field) if @rm_indexed_field
            meta_node._java_node[:_db_version] = version # use the raw java node since Neo4j::Rails::Mode wraps it
          end
        end
      end

      # Same as #execute_up but executes the down_block instead
      def execute_down(context, meta_node)
        if @auto_transaction
          Neo4j::Transaction.run do
            context.instance_eval &@down_block if @down_block
            add_index_on(context, @rm_indexed_field) if @rm_indexed_field
            rm_index_on(context, @add_indexed_field) if @add_indexed_field
            meta_node._java_node[:_db_version] = version - 1
          end
        else
          context.instance_eval &@down_block if @down_block
          add_index_on(context, @rm_indexed_field) if @rm_indexed_field
          Neo4j::Transaction.run do
            rm_index_on(context, @add_indexed_field) if @add_indexed_field
            meta_node._java_node[:_db_version] = version - 1
          end
        end
      end

      def add_index_on(context, fields) #:nodoc:
        context.all.each do |node|
          fields.each do |field|
            node.add_index(field)
          end
        end
      end

      def rm_index_on(context, fields) #:nodoc:
        context.all.each do |node|
          fields.each do |field|
            node.rm_index(field)
          end
        end
      end


      def to_s
        "Migration version: #{version}, name: #{name}"
      end
    end

  end
end