From 320ac0901d200ee618c20dcc08f3dd2c8bddee30 Mon Sep 17 00:00:00 2001
From: "Joshua A. Horton" <joshua_horton@sil.org>
Date: Mon, 4 Mar 2019 09:01:34 +0700
Subject: [PATCH] Implements a shutdown() function on LMLayer, killing the
 worker.

---
 common/predictive-text/index.ts                       |  8 ++++++++
 .../unit_tests/in_browser/cases/top-level-lmlayer.js  |  2 ++
 .../in_browser/cases/worker-dummy-integration.js      |  1 +
 .../in_browser/cases/worker-wordlist-integration.js   |  1 +
 .../unit_tests/in_browser/cases/worker.js             |  1 +
 common/predictive-text/worker/index.ts                | 11 +++++++++++
 6 files changed, 24 insertions(+)

diff --git a/common/predictive-text/index.ts b/common/predictive-text/index.ts
index 0c43d6bd4b..88ea5c1de1 100644
--- a/common/predictive-text/index.ts
+++ b/common/predictive-text/index.ts
@@ -113,6 +113,14 @@ namespace com.keyman.text.prediction {
       }
     }
 
+    /**
+     * Clears out any computational resources in use by the LMLayer, including shutting
+     * down any internal WebWorkers.
+     */
+    public shutdown() {
+      this._worker.terminate();
+    }
+
     /**
      * Given a function, this utility returns the source code within it, as a string.
      * This is intended to unwrap the "wrapped" source code created in the LMLayerWorker
diff --git a/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.js b/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.js
index 2083e2e29c..a97e84b20d 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.js
+++ b/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.js
@@ -6,6 +6,7 @@ describe('LMLayer', function () {
     it('should construct with zero arguments', function () {
       let lmLayer = new LMLayer();
       assert.instanceOf(lmLayer, LMLayer);
+      lmLayer.shutdown();
     });
   });
 
@@ -25,6 +26,7 @@ describe('LMLayer', function () {
       let worker = new Worker(uri);
       worker.onmessage = function thisShouldBeCalled(event) {
         assert.propertyVal(event, 'data', 'fhqwhgads');
+        worker.terminate();
         done();
       };
     })
diff --git a/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.js b/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.js
index 5137e042ad..360699bf84 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.js
+++ b/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.js
@@ -35,6 +35,7 @@ describe('LMLayer using dummy model', function () {
         return lmLayer.predict(zeroTransform(), emptyContext());
       }).then(function (suggestions) {
         assert.deepEqual(suggestions, iGotDistractedByHazel()[3]);
+        lmLayer.shutdown();
         return Promise.resolve();
       });
     });
diff --git a/common/predictive-text/unit_tests/in_browser/cases/worker-wordlist-integration.js b/common/predictive-text/unit_tests/in_browser/cases/worker-wordlist-integration.js
index a5e14af879..281c652e9f 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/worker-wordlist-integration.js
+++ b/common/predictive-text/unit_tests/in_browser/cases/worker-wordlist-integration.js
@@ -35,6 +35,7 @@ describe('LMLayer using the word list model', function () {
         return lmLayer.predict(type('q'), atEndOfBuffer('the '));
       }).then(function (suggestions) {
         assert.isAtLeast(suggestions.length, EXPECTED_SUGGESTIONS);
+        lmLayer.shutdown();
         return Promise.resolve();
       });
     });
diff --git a/common/predictive-text/unit_tests/in_browser/cases/worker.js b/common/predictive-text/unit_tests/in_browser/cases/worker.js
index be81f4c5ef..693967323b 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/worker.js
+++ b/common/predictive-text/unit_tests/in_browser/cases/worker.js
@@ -17,6 +17,7 @@ describe('LMLayerWorker', function () {
       let worker = new Worker(uri);
       worker.onmessage = function thisShouldBeCalled(message) {
         done();
+        worker.terminate();
       };
       worker.postMessage({
         message: 'initialize',
diff --git a/common/predictive-text/worker/index.ts b/common/predictive-text/worker/index.ts
index 7aa85f1a60..6621cc818c 100644
--- a/common/predictive-text/worker/index.ts
+++ b/common/predictive-text/worker/index.ts
@@ -72,6 +72,9 @@ class LMLayerWorker {
   /**
    * By default, it's self.importScripts(), but can be overridden
    * so that this can be tested **outside of a Worker**.
+   * 
+   * To function properly, self.importScripts() must be bound to self
+   * before being stored here, else it will fail.
    */
   private _importScripts: ImportScripts;
 
@@ -161,6 +164,13 @@ class LMLayerWorker {
     this._importScripts(url);
   }
 
+  public unloadModel() {
+    // Right now, this seems sufficient to clear out the old model.
+    // The only existing reference to a loaded model is held by 
+    // transitionToReadyState's `handleMessage` closure. (The `model` var)
+    this.setupInitialState();
+  }
+
   /**
    * Sets the initial state, i.e., `uninitialized`.
    * This state only handles `initialized` messages, and will
@@ -229,6 +239,7 @@ class LMLayerWorker {
     scope.onmessage = worker.onMessage.bind(worker);
 
     // Ensures that the worker instance is accessible for loaded model scripts.
+    // Assists unit-testing.
     scope['LMLayerWorker'] = worker;
     scope['models'] = models;