Impl. Migrations, look at the RSpecs for detail. [#108 state:open]

lib/neo4j.rb

@@ -22,6 +22,7 @@
 require 'neo4j/mixins/java_list_mixin'
 require 'neo4j/mixins/relationship_mixin'
 require 'neo4j/mixins/node_mixin'
+require 'neo4j/mixins/migration_mixin'
 
 # relationships
 require 'neo4j/relationships/decl_relationship_dsl'

lib/neo4j/mixins/migration_mixin.rb

@@ -0,0 +1,89 @@
+module Neo4j
+
+  # By including this mixing on a node class one can add migrations to it.
+  # Adds a db_version attribute on the class including this mixin.
+  # 
+  module MigrationMixin
+
+    def db_version
+      Neo4j::Transaction.run {self[:db_version] || 0}
+    end
+
+
+    def init_with_node(java_node) # :nodoc:
+      super # call Neo4j::NodeMixin#init_with_node
+      migrate! self.class.migrate_to # for lazy migrations
+    end
+
+
+    def migrate!(to_version=nil)
+      return if self.class.migrations.nil? || self.class.migrations.empty?
+      puts "Curr version #{db_version}"
+      to_version ||= self.class.migrations.keys.sort.reverse[0]
+      puts "To version #{to_version}"
+
+      Neo4j::Transaction.new
+      # going up or down ?
+      if (db_version == to_version)
+        puts "Already at version #{to_version}"
+      elsif (db_version < to_version)
+        Migrator.upgrade( (db_version+1).upto(to_version).collect { |ver| self.class.migrations[ver] }, self )
+      else
+        Migrator.downgrade( db_version.downto(to_version+1).collect { |ver| self.class.migrations[ver] }, self )
+      end
+      self[:db_version] = to_version
+      Neo4j::Transaction.finish
+    end
+
+    def self.included(c) # :nodoc:
+      c.extend Neo4j::MigrationMixin::ClassMethods
+    end
+
+    module ClassMethods
+      attr_accessor :migrations, :migrate_to
+
+      def migration(number, name, &block)
+        @migrations ||= {}
+        @migrations[number] = {:name => name, :block => block}
+      end
+
+      def migrate!(to_version=nil)
+        @migrate_to = to_version
+      end
+    end
+
+    # This is used as both the context for the Migration DSL and running the actual migrations.
+    class Migrator # :nodoc:
+      attr_reader :up_blocks, :down_blocks
+
+      def up(&block)
+        @up_blocks ||= []
+        @up_blocks << block
+      end
+
+      def down(&block)
+        @down_blocks ||= []
+        @down_blocks << block
+      end
+
+      class << self
+        def upgrade(migrations, node_context)
+          get_blocks(migrations).up_blocks.each {|block| node_context.instance_eval &block}
+        end
+
+        def downgrade(migrations, node_context)
+          get_blocks(migrations).down_blocks.each { |block| node_context.instance_eval &block}
+        end
+
+        def get_blocks(migrations)
+          context = Migrator.new
+          migrations.each {|m| puts "Running Migration #{m[:name]}"; context.instance_eval &m[:block]}
+          context
+        end
+      end
+    end
+
+
+  end
+end
+