bluetooth: Add control for reading/writing of characteristics to internals page.

chrome/browser/resources/bluetooth_internals/value_control.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * Javascript for ValueControl, served from chrome://bluetooth-internals/.
+ */
+
+cr.define('value_control', function() {
+  /** @const */ var Snackbar = snackbar.Snackbar;
+  /** @const */ var SnackbarType = snackbar.SnackbarType;
+
+  /** @const {!Array<string>} */
+  var VALUE_DATA_TYPES = ['Hexadecimal', 'UTF-8', 'Decimal'];
+
+  /**
+   * A set of inputs that allow a user to request reads and writes of values.
+   * This control allows the value to be displayed in multiple forms
+   * as defined by the |VALUE_DATA_TYPES| array. Values must be written
+   * in these formats. Read and write capability is controlled by a
+   * 'permissions' bitfield provided by the characteristic.
+   * @constructor
+   */
+  var ValueControl = cr.ui.define('div');
+
+  ValueControl.prototype = {
+    __proto__: HTMLDivElement.prototype,
+
+    /**
+     * Decorates the element as a ValueControl. Creates the layout for the value
+     * control by creating a text input, select element, and two buttons for
+     * read/write requests. Event handlers are attached and references to these
+     * elements are stored for later use.
+     * @override
+     */
+    decorate: function() {
+      this.classList.add('value-control');
+
+      /** @private {!Array<number>} */
+      this.value_ = [];
+      /** @private {?string} */
+      this.deviceAddress_ = null;
+      /** @private {?string} */
+      this.serviceId_ = null;
+      /** @private {!interfaces.BluetoothDevice.CharacteristicInfo} */
+      this.characteristicInfo_ = null;
+
+      this.unavailableMessage_ = document.createElement('h3');
+      this.unavailableMessage_.textContent = 'Value cannot be read or written.';
+
+      this.valueInput_ = document.createElement('input');
+      this.valueInput_.addEventListener('change', function() {
+        this.value_ = this.convertValueToArray_();
+      }.bind(this));
+
+      this.typeSelect_ = document.createElement('select');
+
+      VALUE_DATA_TYPES.forEach(function(type) {
+        var option = document.createElement('option');
+        option.value = type;
+        option.text = type;
+        this.typeSelect_.add(option);
+      }, this);
+
+      this.typeSelect_.addEventListener('change', this.redraw.bind(this));
+
+      var inputDiv = document.createElement('div');
+      inputDiv.appendChild(this.valueInput_);
+      inputDiv.appendChild(this.typeSelect_);
+
+      this.readBtn_ = document.createElement('button');
+      this.readBtn_.textContent = 'Read';
+      this.readBtn_.addEventListener('click', this.readValue_.bind(this));
+
+      this.writeBtn_ = document.createElement('button');
+      this.writeBtn_.textContent = 'Write';
+      this.writeBtn_.addEventListener('click', this.writeValue_.bind(this));
+
+      var buttonsDiv = document.createElement('div');
+      buttonsDiv.appendChild(this.readBtn_);
+      buttonsDiv.appendChild(this.writeBtn_);
+
+      this.appendChild(this.unavailableMessage_);
+      this.appendChild(inputDiv);
+      this.appendChild(buttonsDiv);
+    },
+
+    /**
+     * Sets the settings used by the value control and redraws the control to
+     * match the read/write settings provided in
+     * |characteristicInfo.permissions|.
+     * @param {string} deviceAddress
+     * @param {string} serviceId
+     * @param {!interfaces.BluetoothDevice.CharacteristicInfo}
+     *     characteristicInfo
+     */
+    load: function(deviceAddress, serviceId, characteristicInfo) {
+      this.deviceAddress_ = deviceAddress;
+      this.serviceId_ = serviceId;
+      this.characteristicInfo_ = characteristicInfo;
+
+      this.redraw();
+    },
+
+    /**
+     * Redraws the value control with updated layout depending on the
+     * availability of reads and writes and the current cached value.
+     */
+    redraw: function() {
+      this.readBtn_.hidden = (this.characteristicInfo_.properties &
+          interfaces.BluetoothDevice.Property.READ) === 0;
+      this.writeBtn_.hidden = (this.characteristicInfo_.properties &
+          interfaces.BluetoothDevice.Property.WRITE) === 0;
+
+      var isAvailable = !this.readBtn_.hidden || !this.writeBtn_.hidden;
+      this.unavailableMessage_.hidden = isAvailable;
+      this.valueInput_.hidden = !isAvailable;
+      this.typeSelect_.hidden = !isAvailable;
+
+      if (!isAvailable) return;
+
+      var type = this.typeSelect_.selectedOptions[0].value;
+
+      switch (type) {
+        case 'Hexadecimal':
+          this.valueInput_.value = this.value_.reduce(
+              function(result, value, index) {
+                var answer = result + ('0' + value.toString(16)).substr(-2);
+                if (index === 0)
+                  return '0x' + answer;
+
+                return answer;
+              }, '');

[ortuno, 2017/01/22 22:38:01]

Why not make this '0x'? instead of having checking for the first element?

[mbrunson, 2017/01/24 00:25:31]

What if |value_| is empty? I didn't want '0x' printing by itself, so I just put
an if statement in the reduce function.

Alternatively, I could put the if statement on the outside and put the reduce in
an else statement.

+          break;
+
+        case 'UTF-8':
+          this.valueInput_.value = this.value_.reduce(function(result, value) {
+            return result + String.fromCharCode(value);
+          }, '');
+          break;
+
+        case 'Decimal':
+          this.valueInput_.value = this.value_.reduce(
+              function(result, value, index) {
+                if (index === this.value_.length - 1)
+                  return result + value.toString();
+                else
+                  return result + value.toString() + '-';
+              }.bind(this), '');
+          break;
+      }
+    },
+
+    /**
+     * Sets the value of the control.
+     * @param {!Array<number>} value
+     */
+    setValue: function(value) {
+      this.value_ = value;
+      this.redraw();
+    },
+
+    /**
+     * Converts the current value of the text input into an array of numbers
+     * using the currently selected format in the type select element. The
+     * numbers are created such that they will not exceed 8-bits in length to be
+     * compatible with the expected data type of values set in a characteristic.
+     * @return {!Array<number>}
+     * @private
+     */
+    convertValueToArray_: function() {
+      var value = this.valueInput_.value;
+      if (!value) return;
+
+      var type = this.typeSelect_.selectedOptions[0].value;
+      switch (type) {
+        case 'Hexadecimal':
+          value = value.replace('0x', '');

[ortuno, 2017/01/22 22:38:01]

We should show an error if the string in value is not of the right format. OK to
do in follow up.

[mbrunson, 2017/01/24 00:25:31]

Done.

+          return Array.from(value).reduce(function(result, value, index) {

[ortuno, 2017/01/22 22:38:01]

I appreciate the use of reduce but I think that just makes the code harder to
follow. I would just do:

var result = [];
for (var i = 2; i < value.length; i += 2) {
  result.push(parseInt(value.substr(i, 2), 16));
}
return result;

[mbrunson, 2017/01/24 00:25:31]

Done.

+            if (index % 2 == 0)
+              result.push(parseInt(value, 16) << 4);
+            else
+              result[Math.floor(index/2)] += parseInt(value, 16);
+            return result;

[ortuno, 2017/01/22 22:38:01]

What's our current policy on tests? Should we have tests to make sure the
correct values are being read/written?

[mbrunson, 2017/01/24 00:25:31]

Added tests. Caught some issues. :-)

Done.

+          }, []);
+
+        case 'UTF-8':
+          return Array.from(value).map(function(char) {
+            return char.charCodeAt(0);
+          });
+
+        case 'Decimal':
+          return value.split('-').map(parseInt);
+      }
+    },
+
+    /**
+     * Called when the read button is pressed. Connects to the device and
+     * retrieves the current value of the characteristic in the |service_id|
+     * with id |characteristic_id|
+     * @private
+     */
+    readValue_: function() {
+      this.readBtn_.disabled = true;
+
+      device_broker.connectToDevice(this.deviceAddress_).then(function(device) {

[ortuno, 2017/01/22 22:38:01]

Why do we need to connect? Can't we just check if there is a connected devices
already and use that?

[mbrunson, 2017/01/24 00:25:31]

The connectToDevice function does that internally. If a connection exists, the
existing DevicePtr is returned. If no connection exists, it creates one and
returns the new DevicePtr.

+        return device.readValueForCharacteristic(
+            this.serviceId_, this.characteristicInfo_.id);
+      }.bind(this)).then(function(response) {
+        this.readBtn_.disabled = false;
+        var GattResult = interfaces.BluetoothDevice.GattResult;
+
+        if (response.result === GattResult.SUCCESS) {
+          this.setValue(response.value);
+          Snackbar.show(
+              this.deviceAddress_ + ': Read succeeded', SnackbarType.SUCCESS);
+          return;
+        }
+
+        // TODO(crbug.com/663394): Replace with more descriptive error
+        // messages.
+        var errorString = Object.keys(GattResult).find(function(key) {
+          return GattResult[key] === response.result;
+        });
+
+        Snackbar.show(
+          this.deviceAddress_ + ': ' + errorString, SnackbarType.ERROR,
+          'Retry', this.readValue_.bind(this));
+      }.bind(this));
+    },
+
+    /**
+     * Called when the write button is pressed. Connects to the device and
+     * retrieves the current value of the characteristic in the |service_id|
+     * with id |characteristic_id|
+     * @private
+     */
+    writeValue_: function() {
+      this.writeBtn_.disabled = true;
+
+      device_broker.connectToDevice(this.deviceAddress_).then(function(device) {
+        return device.writeValueForCharacteristic(
+            this.serviceId_, this.characteristicInfo_.id, this.value_);
+      }.bind(this)).then(function(response) {
+        this.writeBtn_.disabled = false;
+        var GattResult = interfaces.BluetoothDevice.GattResult;
+
+        if (response.result === GattResult.SUCCESS) {
+          Snackbar.show(
+              this.deviceAddress_ + ': Write succeeded', SnackbarType.SUCCESS);
+          return;
+        }
+
+        // TODO(crbug.com/663394): Replace with more descriptive error
+        // messages.
+        var errorString = Object.keys(GattResult).find(function(key) {
+          return GattResult[key] === response.result;
+        });
+
+        Snackbar.show(
+            this.deviceAddress_ + ': ' + errorString, SnackbarType.ERROR,
+            'Retry', this.writeValue_.bind(this));
+      }.bind(this));
+    },
+  }
+
+  return {
+    ValueControl: ValueControl,
+  };
+});