Fixes ButtonStatus not firing events.

ButtonStatus was overwriting the "old state" of the button board
every time it got a chunk of serial data, whether an update packet
was complete or not. Oops. Turns out you never detect any events
that way.

Also adds a couple specs and does a little refactoring.

lib/bitfield.js

@@ -18,7 +18,9 @@ class Bitfield {
       this.buffer = new Buffer(buffer.length);
       buffer.copy(this.buffer);
     } else if (isNumeric(buffer)) {
-      this.buffer = new Buffer(byteIndex(Math.floor(Number(buffer) - 1)) + 1);
+      let bitCount = Math.floor(Number(buffer));
+      let lastBitIdx = bitCount - 1;
+      this.buffer = new Buffer(byteIndex(lastBitIdx) + 1);
     } else {
       throw new Error('Bitfield constructor accepts a Buffer or an integer bitfield width');
     }

lib/buttonStatus.js

@@ -3,11 +3,11 @@ const EventEmitter = require('events').EventEmitter;
 const Bitfield = require('./bitfield');
 
 class ButtonStatus extends EventEmitter {
-  constructor(mapping) {
+  constructor(mapping, packetByteLength = 8) {
     super();
     this.mapping = mapping;
-    this.state = new Bitfield(new Buffer(8));
-    this.oldState = new Bitfield(new Buffer(8));
+    this.state = new Bitfield(new Buffer(packetByteLength));
+    this.oldState = new Bitfield(new Buffer(packetByteLength));
     this.dataQueue = new Buffer(0);
   }
 
@@ -23,11 +23,10 @@ class ButtonStatus extends EventEmitter {
     let seqCount = dataQueue.filter(byte => byte & 1).length;
     if (seqCount === 0) return;
 
-    // Move current state to old state.
-    state.copyTo(oldState);
-
     // Process each buffered sequence.
     for (let seqNum = 0; seqNum < seqCount; seqNum++) {
+      // Move current state to old state.
+      state.copyTo(oldState);
       state.copyFrom(dataQueue);
       dataQueue = dataQueue.slice(state.length);
       this._triggerEvents()

test/bitfield_spec.js

@@ -86,6 +86,22 @@ describe('Bitfield', () => {
       bfSrc = bfSrc.setAt(0, 0);
       assert.notDeepEqual(bfDest.buffer, bfSrc.buffer);
     });
+
+    it('should copy from a shorter bitfield', () => {
+      let bfSrc = Bitfield.fromBits([1,0,1]);
+      let bfDest = new Bitfield(Buffer.from([0x00, 0x00]));
+
+      bfDest.copyFrom(bfSrc);
+      assert.deepEqual(bfDest.toString(), "10100000000000");
+    })
+
+    it('should copy from a longer bitfield', () => {
+      let bfSrc = new Bitfield(Buffer.from([0x0E, 0xFE]));
+      let bfDest = new Bitfield(7);
+
+      bfDest.copyFrom(bfSrc);
+      assert.deepEqual(bfDest.toString(), "1110000");
+    });
   });
 
   describe('copyTo()', () => {
@@ -160,10 +176,12 @@ describe('Bitfield', () => {
       let bf1 = Bitfield.fromBits([1,0,1]);
       let bf2 = Bitfield.fromBits([1,1,0]);
       let changeIdx = 1;
-      for (let {index, value} of bf1.xor(bf2)) {
-        assert.equal(index, changeIdx++)
-        assert.equal(value, bf1.at(index));
-      }
+      let changes = [...bf1.xor(bf2)];
+      assert.equal(changes.length, 2);
+      assert.equal(changes[0].index, 1);
+      assert.equal(changes[0].value, 0);
+      assert.equal(changes[1].index, 2);
+      assert.equal(changes[1].value, 1);
     });
   });
 });

test/buttonStatus_spec.js

@@ -7,7 +7,7 @@ describe('buttonStatus', () => {
   let buttonStatus = null;
 
   beforeEach(() => {
-    buttonStatus = new ButtonStatus([0,1,2]);
+    buttonStatus = new ButtonStatus([0,1,2,3,4,5,6,7]);
   });
 
   describe('update()', () => {
@@ -30,6 +30,23 @@ describe('buttonStatus', () => {
       buttonStatus.update(Buffer.from([0x07]));
     });
 
+    it('should fire buttonDown event when updating with partial packets', done => {
+      let buttonsDown = [];
+      let packetBytes = [0x02, 0x00, 0x01];
+
+      buttonStatus.on('buttonDown', button => {
+        assert.equal(button, 0);
+        done();
+      });
+
+      function update(bytes) {
+        buttonStatus.update(Buffer.from([bytes.shift()]));
+        if (bytes.length > 0) setImmediate(() => update(bytes), 100);
+      }
+
+      update(packetBytes);
+    });
+
     it('should fire buttonUp event', done => {
       let buttonsUp = [];
 
@@ -51,8 +68,8 @@ describe('buttonStatus', () => {
       let json = buttonStatus.toJSON();
       assert.ok('length' in json);
       assert.ok('buttons' in json);
-      assert.equal(json.length, 3);
-      assert.deepEqual(json.buttons, {0:0, 1:0, 2:0});
+      assert.equal(json.length, 8);
+      assert.deepEqual(json.buttons, {0:0, 1:0, 2:0, 3:0, 4:0, 5:0, 6:0, 7:0});
     });
   });
 })