Added support for conflicts_with?

Closes ice-cube-ruby#41

lib/ice_cube/schedule.rb

@@ -125,9 +125,7 @@ def occurrences(closing_time)
 
     # All of the occurrences
     def all_occurrences
-      unless end_time || recurrence_rules.all?(&:terminating?)
-        raise ArgumentError.new('Rule must specify either an until date or a count to use #all_occurrences')
-      end
+      raise ArgumentError.new('Rule must specify either an until date or a count to use #all_occurrences') unless terminating?
       find_occurrences(start_time)
     end
 
@@ -180,6 +178,43 @@ def occurring_at?(time)
       end
     end
 
+    # Determine if this schedule conflicts with another schedule
+    # @param [IceCube::Schedule] other_schedule - The schedule to compare to
+    # @param [Time] closing_time - the last time to consider
+    # @return [Boolean] whether or not the schedules conflict at all
+    def conflicts_with?(other_schedule, closing_time = nil)
+      unless terminating? || other_schedule.terminating? || closing_time
+        raise ArgumentError.new 'At least one schedule must be terminating to use #conflicts_with?'
+      end
+      # Pick the terminating schedule, and other schedule
+      # No need to reverse if terminating? or there is a closing time
+      terminating_schedule = self
+      unless terminating? || closing_time
+        terminating_schedule, other_schedule = other_schedule, terminating_schedule
+      end
+      # Go through each occurrence of the terminating schedule and determine
+      # if the other occurs at that time
+      last_time = nil
+      terminating_schedule.each_occurrence do |time|
+        if closing_time && time > closing_time
+          last_time = closing_time
+          break
+        end
+        last_time = time
+        return true if other_schedule.occurring_at?(time)
+      end
+      # Due to durations, we need to walk up to the end time, and verify in the
+      # other direction
+      if last_time
+        other_schedule.each_occurrence do |time|
+          break if time > last_time
+          return true if terminating_schedule.occurring_at?(time)
+        end
+      end
+      # No conflict, return false
+      false
+    end
+
     # Determine if the schedule occurs at a specific time
     def occurs_at?(time)
       occurs_between?(time, time)
@@ -261,6 +296,12 @@ def self.from_hash(data, options = {})
       schedule
     end
 
+    # Determine if the schedule will end
+    # @return [Boolean] true if ending, false if repeating forever
+    def terminating?
+      end_time || recurrence_rules.all?(&:terminating?)
+    end
+
     private
 
     # Reset all rules for another run

spec/examples/schedule_spec.rb

@@ -4,6 +4,103 @@
 
   include IceCube
 
+  describe :conflicts_with? do
+
+    it 'should raise an error if both are not terminating' do
+      schedules = 2.times.map do
+        schedule = IceCube::Schedule.new(Time.now)
+        schedule.rrule IceCube::Rule.daily
+        schedule
+      end
+      lambda do
+        schedules.first.conflicts_with?(schedules.last)
+      end.should raise_error ArgumentError
+    end
+
+    it 'should not raise error if both are non-terminating closing time present' do
+      schedule1 = IceCube::Schedule.new Time.now
+      schedule1.rrule IceCube::Rule.weekly
+      schedule2 = IceCube::Schedule.new Time.now
+      schedule2.rrule IceCube::Rule.weekly
+      lambda do
+        schedule1.conflicts_with?(schedule2, Time.now + IceCube::ONE_DAY)
+      end.should_not raise_error
+    end
+
+    it 'should not raise an error if one is non-terminating' do
+      schedule1 = IceCube::Schedule.new Time.now
+      schedule1.rrule IceCube::Rule.weekly
+      schedule2 = IceCube::Schedule.new Time.now
+      schedule2.rrule IceCube::Rule.weekly.until(Time.now)
+      lambda do
+        schedule1.conflicts_with?(schedule2)
+      end.should_not raise_error
+    end
+
+    it 'should not raise an error if the other is non-terminating' do
+      schedule1 = IceCube::Schedule.new Time.now
+      schedule1.rrule IceCube::Rule.weekly.until(Time.now)
+      schedule2 = IceCube::Schedule.new Time.now
+      schedule2.rrule IceCube::Rule.weekly
+      lambda do
+        schedule1.conflicts_with?(schedule2)
+      end.should_not raise_error
+    end
+
+    it 'should return true if conflict is present' do
+      start_time = Time.now
+      schedule1 = IceCube::Schedule.new(start_time)
+      schedule1.rrule IceCube::Rule.daily
+      schedule2 = IceCube::Schedule.new(start_time)
+      schedule2.rrule IceCube::Rule.daily
+      conflict = schedule1.conflicts_with?(schedule2, start_time + IceCube::ONE_DAY)
+      conflict.should be_true
+    end
+
+    it 'should return false if conflict is not present' do
+      start_time = Time.now
+      schedule1 = IceCube::Schedule.new(start_time)
+      schedule1.rrule IceCube::Rule.weekly.day(:tuesday)
+      schedule2 = IceCube::Schedule.new(start_time)
+      schedule2.rrule IceCube::Rule.weekly.day(:monday)
+      conflict = schedule1.conflicts_with?(schedule2, start_time + IceCube::ONE_DAY)
+      conflict.should be_false
+    end
+
+    it 'should return true if conflict is present based on duration' do
+      start_time = Time.now
+      schedule1 = IceCube::Schedule.new(start_time, :duration => IceCube::ONE_DAY + 1)
+      schedule1.rrule IceCube::Rule.weekly.day(:monday)
+      schedule2 = IceCube::Schedule.new(start_time)
+      schedule2.rrule IceCube::Rule.weekly.day(:tuesday)
+      conflict = schedule1.conflicts_with?(schedule2, start_time + IceCube::ONE_WEEK)
+      conflict.should be_true
+    end
+
+    it 'should return true if conflict is present based on duration - other way' do
+      start_time = Time.now
+      schedule1 = IceCube::Schedule.new(start_time)
+      schedule1.rrule IceCube::Rule.weekly.day(:tuesday)
+      schedule2 = IceCube::Schedule.new(start_time, :duration => IceCube::ONE_DAY + 1)
+      schedule2.rrule IceCube::Rule.weekly.day(:monday)
+      conflict = schedule1.conflicts_with?(schedule2, start_time + IceCube::ONE_WEEK)
+      conflict.should be_true
+    end
+
+    it 'should return false if conflict is past closing_time' do
+      start_time = Time.local(2011, 1, 1, 12) # Sunday
+      schedule1 = IceCube::Schedule.new(start_time)
+      schedule1.rrule IceCube::Rule.weekly.day(:friday)
+      schedule2 = IceCube::Schedule.new(start_time)
+      schedule2.rrule IceCube::Rule.weekly.day(:friday)
+      schedule2.conflicts_with?(schedule1, start_time + IceCube::ONE_WEEK).
+        should be_true
+      schedule2.conflicts_with?(schedule1, start_time + IceCube::ONE_DAY).
+        should be_false
+    end
+
+  end
+
   describe :each do
 
     it 'should be able to yield occurrences for a schedule' do