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with HAL;      use HAL;
with HAL.Time;

package MicroBit.Time is

   subtype Time_Ms is UInt64;

   function Clock return Time_Ms;

   procedure Delay_Ms (Milliseconds : UInt64);

   procedure Sleep (Milliseconds : UInt64) renames Delay_Ms;

   function Tick_Period return Time_Ms;

   type Tick_Callback is access procedure;

   function Tick_Subscriber (Callback : not null Tick_Callback) return Boolean;
   --  Return True if callback is already a tick event subscriber

   function Tick_Subscribe (Callback : not null Tick_Callback) return Boolean
     with Pre  => not Tick_Subscriber (Callback),
          Post => (if Tick_Subscribe'Result then Tick_Subscriber (Callback));
   --  Subscribe a callback to the tick event. The function return True on
   --  success, False if there's no more room for subscribers.

   function Tick_Unsubscribe (Callback : not null Tick_Callback) return Boolean
     with Pre  => Tick_Subscriber (Callback),
          Post => (if Tick_Unsubscribe'Result then not Tick_Subscriber (Callback));
   --  Unsubscribe a callback to the tick event. The function return True on
   --  success, False if the callback was not a subscriber.

   function HAL_Delay return not null HAL.Time.Any_Delays;
private

   type MB_Delays is new HAL.Time.Delays with null record;

   overriding
   procedure Delay_Microseconds (This : in out MB_Delays;
                                 Us   : Integer);

   overriding
   procedure Delay_Milliseconds (This : in out MB_Delays;
                                 Ms   : Integer);

   overriding
   procedure Delay_Seconds      (This : in out MB_Delays;
                                 S    : Integer);

end MicroBit.Time;
