Different colors for new tracks, types and levels

Every time a new track, event type or difficulty level is created, the color picker has a different color by default.

Closes https://github.com/openSUSE/osem/issues/1077

app/controllers/admin/difficulty_levels_controller.rb

@@ -11,7 +11,7 @@ module Admin
     def edit; end
 
     def new
-      @difficulty_level = @conference.program.difficulty_levels.new
+      @difficulty_level = @conference.program.difficulty_levels.new(color: @conference.next_color_for_collection(:levels))
     end
 
     def create

app/controllers/admin/event_types_controller.rb

@@ -9,7 +9,7 @@ module Admin
     def edit; end
 
     def new
-      @event_type = @conference.program.event_types.new
+      @event_type = @conference.program.event_types.new(color: @conference.next_color_for_collection(:types))
     end
 
     def create

app/controllers/admin/tracks_controller.rb

@@ -14,7 +14,7 @@ module Admin
     end
 
     def new
-      @track = @program.tracks.new
+      @track = @program.tracks.new(color: @conference.next_color_for_collection(:tracks))
     end
 
     def create

app/models/conference.rb

@@ -595,6 +595,20 @@ class Conference < ActiveRecord::Base
     registration_limit > 0 && registrations.count >= registration_limit
   end
 
+  # Returns an hexadecimal color given a collection. The returned color changed
+  # when the number of element in the collection changes and for consecutive
+  # number of elements it returns highly different colors.
+  def next_color_for_collection(collection)
+    # we have different start indices for every collection to generate a
+    # different color for every of them.
+    start_index = {
+      tracks: (program.tracks.count + 1),
+      levels: (program.difficulty_levels.count + 51),
+      types: (program.event_types.count + 101)
+    }
+    next_color(start_index[collection])
+  end
+
   private
 
   # Returns a different html colour for every i and consecutive colors are

app/models/difficulty_level.rb

@@ -3,4 +3,5 @@ class DifficultyLevel < ActiveRecord::Base
   has_many :events, dependent: :nullify
 
   validates :title, presence: true
+  validates :color, format: /\A#[0-9a-fA-F]{6}\z/
 end

app/models/event_type.rb

@@ -7,6 +7,7 @@ class EventType < ActiveRecord::Base
   validates :minimum_abstract_length, presence: true
   validates :maximum_abstract_length, presence: true
   validate :length_step
+  validates :color, format: /\A#[0-9a-fA-F]{6}\z/
 
   alias_attribute :name, :title
 

app/models/track.rb

@@ -4,6 +4,7 @@ class Track < ActiveRecord::Base
 
   before_create :generate_guid
   validates :name, presence: true
+  validates :color, format: /\A#[0-9a-fA-F]{6}\z/
 
   private
 

spec/factories/event_types.rb

@@ -6,6 +6,7 @@ FactoryGirl.define do
     length 30
     minimum_abstract_length 0
     maximum_abstract_length 500
+    color '#ffffff'
     program
   end