From 43e94b83b49f88de921ded962df82f959a8ad51e Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Tue, 10 May 2016 17:04:16 -0400
Subject: [PATCH] Timer driver

---
 js/src/main.js         |   1 +
 js/src/timer-driver.js | 114 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 js/src/timer-driver.js

diff --git a/js/src/main.js b/js/src/main.js
index 0925f29..96a580a 100644
--- a/js/src/main.js
+++ b/js/src/main.js
@@ -29,6 +29,7 @@ module.exports.Ack = require('./ack.js').Ack;
 module.exports.RandomID = require('./randomid.js');
 module.exports.DOM = require("./dom-driver.js");
 module.exports.JQuery = require("./jquery-driver.js");
+module.exports.Timer = require("./timer-driver.js");
 module.exports.Reflect = require("./reflect.js");
 module.exports.WakeDetector = require("./wake-detector-driver.js");
 module.exports.Codec = require("./codec.js");
diff --git a/js/src/timer-driver.js b/js/src/timer-driver.js
new file mode 100644
index 0000000..0ee8162
--- /dev/null
+++ b/js/src/timer-driver.js
@@ -0,0 +1,114 @@
+// Timer event driver
+var Patch = require("./patch.js");
+var DemandMatcher = require('./demand-matcher.js').DemandMatcher;
+var Struct = require('./struct.js');
+
+var Dataspace_ = require("./dataspace.js");
+var Dataspace = Dataspace_.Dataspace;
+var __ = Dataspace_.__;
+var _$ = Dataspace_._$;
+
+var periodicTick = Struct.makeConstructor('periodicTick', ['intervalMS']); // message
+var timeLaterThan = Struct.makeConstructor('timeLaterThan', ['deadlineMS']); // assertion
+
+function spawnTimerDriver() {
+  Dataspace.spawn(
+    new DemandMatcher([Patch.observe(periodicTick(_$('intervalMS')))],
+		      [Patch.advertise(periodicTick(_$('intervalMS')))],
+		      {
+			onDemandIncrease: function (c) {
+			  Dataspace.spawn(new Tick(c.intervalMS));
+			}
+		      }));
+  Dataspace.spawn(
+    new DemandMatcher([Patch.observe(timeLaterThan(_$('deadlineMS')))],
+		      [Patch.advertise(timeLaterThan(_$('deadlineMS')))],
+		      {
+			onDemandIncrease: function (c) {
+			  Dataspace.spawn(new Alarm(c.deadlineMS));
+			}
+		      }));
+}
+
+function Tick(intervalMS) {
+  this.intervalMS = intervalMS;
+  this.handle = null;
+}
+
+Tick.prototype.boot = function () {
+  var self = this;
+  this.handle = setInterval(Dataspace.wrap(function () {
+    Dataspace.send(periodicTick(self.intervalMS));
+  }), this.intervalMS);
+
+  return Patch.sub(Patch.observe(periodicTick(this.intervalMS))) // monitor interest
+    .andThen(Patch.pub(periodicTick(this.intervalMS))) // signal we exist to DemandMatcher
+  ;
+};
+
+Tick.prototype.trapexit = function () {
+  this.cancelTimer();
+};
+
+Tick.prototype.cancelTimer = function () {
+  if (this.handle !== null) {
+    clearInterval(this.handle);
+    this.handle = null;
+  }
+};
+
+Tick.prototype.handleEvent = function (e) {
+  if (e.type === 'stateChange' && e.patch.hasRemoved()) {
+    Dataspace.exit();
+  }
+};
+
+function Alarm(deadlineMS) {
+  this.deadlineMS = deadlineMS;
+  this.handle = null;
+}
+
+Alarm.prototype.boot = function () {
+  this.checkTimeout();
+
+  return Patch.sub(Patch.observe(timeLaterThan(this.deadlineMS))) // monitor interest
+    .andThen(Patch.pub(timeLaterThan(this.deadlineMS))) // signal we exist to DemandMatcher
+  ;
+};
+
+Alarm.prototype.checkTimeout = function () {
+  var now = +(new Date());
+  var delta = this.deadlineMS - now;
+  if (delta <= 0) {
+    Dataspace.stateChange(Patch.assert(timeLaterThan(this.deadlineMS)));
+    this.cancelTimer();
+  } else if (this.handle === null) {
+    var self = this;
+    this.handle = setTimeout(Dataspace.wrap(function () { self.checkTimeout(); }), delta);
+  }
+};
+
+Alarm.prototype.cancelTimer = function () {
+  if (this.handle !== null) {
+    clearTimeout(this.handle);
+    this.handle = null;
+  }
+};
+
+Alarm.prototype.trapexit = function () {
+  this.cancelTimer();
+};
+
+Alarm.prototype.handleEvent = function (e) {
+  if (e.type === 'stateChange' && e.patch.hasRemoved()) {
+    Dataspace.exit();
+  }
+};
+
+///////////////////////////////////////////////////////////////////////////
+
+module.exports.spawnTimerDriver = spawnTimerDriver;
+module.exports.periodicTick = periodicTick;
+module.exports.timeLaterThan = timeLaterThan;
+module.exports.Tick = Tick;
+module.exports.Alarm = Alarm;