Issue relations first commit (not thoroughly tested). 4 kinds of relation are available:

* relates to: do nothing special. Just to know that the 2 issues are related...
* duplicates: will close the related issue with the same status when closing the issue (not implemented yet)
* blocks: will require to close the blocking issue before closing the blocked issue (not implemented yet)
* precedes (end to start relation): start date of the related issue depends on the due date of the preceding issue (implemented). A delay can be set so that the related issue can only start n days after the end of the preceding issue. When setting dates for an issue, dates of all downstream issues are set according to these relations.

To set a relation, the 2 issues have to belong to the same project (may change in the future). So if an issue is moved to another project, all its relations are removed.
Circular dependencies are checked when creating a relation.

git-svn-id: http://redmine.rubyforge.org/svn/trunk@506 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue.rb

@@ -1,5 +1,5 @@
 # redMine - project management software
-# Copyright (C) 2006  Jean-Philippe Lang
+# Copyright (C) 2006-2007  Jean-Philippe Lang
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -16,7 +16,6 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 class Issue < ActiveRecord::Base
-
   belongs_to :project
   belongs_to :tracker
   belongs_to :status, :class_name => 'IssueStatus', :foreign_key => 'status_id'
@@ -33,6 +32,9 @@ class Issue < ActiveRecord::Base
   has_many :custom_fields, :through => :custom_values
   has_and_belongs_to_many :changesets, :order => "revision ASC"
   
+  has_many :relations_from, :class_name => 'IssueRelation', :foreign_key => 'issue_from_id', :dependent => :delete_all
+  has_many :relations_to, :class_name => 'IssueRelation', :foreign_key => 'issue_to_id', :dependent => :delete_all
+  
   acts_as_watchable
   
   validates_presence_of :subject, :description, :priority, :tracker, :author, :status
@@ -52,13 +54,13 @@ class Issue < ActiveRecord::Base
     if self.due_date and self.start_date and self.due_date < self.start_date
       errors.add :due_date, :activerecord_error_greater_than_start_date
     end
+    
+    if start_date && soonest_start && start_date < soonest_start
+      errors.add :start_date, :activerecord_error_invalid
+    end
   end
-
-  #def before_create
-  #  build_history
-  #end
   
-  def before_save
+  def before_save  
     if @current_journal
       # attributes changes
       (Issue.column_names - %w(id description)).each {|c|
@@ -78,6 +80,10 @@ class Issue < ActiveRecord::Base
     end
   end
   
+  def after_save
+    relations_from.each(&:set_issue_to_dates)
+  end  
+  
   def long_id
     "%05d" % self.id
   end
@@ -98,12 +104,25 @@ class Issue < ActiveRecord::Base
   def spent_hours
     @spent_hours ||= time_entries.sum(:hours) || 0
   end
-
-private
-  # Creates an history for the issue
-  #def build_history
-  #  @history = self.histories.build
-  #  @history.status = self.status
-  #  @history.author = self.author
-  #end
+  
+  def relations
+    (relations_from + relations_to).sort
+  end
+  
+  def all_dependent_issues
+    dependencies = []
+    relations_from.each do |relation|
+      dependencies << relation.issue_to
+      dependencies += relation.issue_to.all_dependent_issues
+    end
+    dependencies
+  end
+  
+  def duration
+    (start_date && due_date) ? due_date - start_date : 0
+  end
+  
+  def soonest_start
+    @soonest_start ||= relations_to.collect{|relation| relation.successor_soonest_start}.compact.min
+  end
 end