<!--
// Copyright 2015 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.
-->
<import src="/sky/framework/elements/sky-element.sky" />
<import src="/sky/framework/elements/sky-scrollable.sky" />
<sky-element>
<template>
  <style>
    #control {
      height: -webkit-fill-available;
      background-color: black;
      color: rgb(255, 191, 0);
      font-family: 'Courier', 'monospace';
    }
    .line {
      white-space: pre;
    }
  </style>
  <sky-scrollable id="control" contenteditable />
</template>
<script>
import 'dart:async';
import 'dart:core';
import 'dart:sky';
import 'package:examples/echo_terminal/terminal_client.mojom.dart' as terminal;
import '/sky/framework/embedder.dart';
import 'terminal_display.dart';
import 'terminal_file_impl.dart';

// Implements the <terminal> element, which implements a "terminal display". Has
// an |url| attribute, whose value should be a Mojo app that provides the
// |terminal.TerminalClient| service.
@Tagname('terminal')
class TerminalDisplayImpl extends SkyElement implements TerminalDisplay {
  Element _control;

  // Queue of unconsumed input (keystrokes), with the head at index 0.
  // Keystrokes end up here if there's no reader (i.e., |getChar()|) pending,
  // i.e., if |_readerQueue| is empty. Invariant: At most one of |_inputQueue|
  // and |_readerQueue| may be nonempty at any given time.
  List<int> _inputQueue;

  // Queue of things waiting for input, with the head at index 0. If a keystroke
  // is received and this is nonempty, the head is given that keystroke (and
  // dequeued).
  List<Completer<int>> _readerQueue;

  TerminalDisplayImpl()
      : _inputQueue = new List<int>(),
        _readerQueue = new List<Completer<int>>() {
  }

  void shadowRootReady() {
    _control = shadowRoot.getElementById('control');
    _control.addEventListener('keydown', _handleKeyDown);
    _control.addEventListener('keypress', _handleKeyPress);

    // Initialize with the first line.
    _newLine();

    _connect(getAttribute('url'));
  }

  void _handleKeyDown(KeyboardEvent event) {
    // TODO(vtl): In general, our key handling is a total hack (due in part to
    // sky's keyboard support being incomplete) -- e.g., we shouldn't have to
    // make our div contenteditable. We have to intercept backspace (^H) here,
    // since we won't actually get a keypress event for it. (Possibly, we should
    // only handle keydown instead of keypress, but then we'd have to handle
    // shift, etc. ourselves.)
    if (event.key == 8) {
      _enqueueChar(8);
      event.preventDefault();
    }
  }

  void _handleKeyPress(KeyboardEvent event) {
    _enqueueChar(event.charCode);
    event.preventDefault();
  }

  void _enqueueChar(int charCode) {
    // TODO(vtl): Add "echo" mode; do |putChar(event.charCode);| if echo is on.

    if (_readerQueue.isEmpty) {
      _inputQueue.add(charCode);
    } else {
      _readerQueue.removeAt(0).complete(charCode);
    }
  }

  void _backspace() {
    var oldText = _control.lastChild.textContent;
    if (oldText.length > 0) {
      _control.lastChild.textContent = oldText.substring(0, oldText.length - 1);
    }
  }

  void _newLine() {
    var line = document.createElement('div');
    line.setAttribute('class', 'line');
    _control.appendChild(line);
  }

  void _clear() {
    while (_control.firstChild != null) {
      _control.firstChild.remove();
    }
    _newLine();
  }

  // TODO(vtl): Should we always auto-connect? Should there be facilities for
  // programmatically connecting? (What if the |url| attribute isn't set?)
  void _connect(String url) {
    var terminalClient = new terminal.TerminalClientProxy.unbound();
    embedder.connectToService(url, terminalClient);
    terminalClient.ptr.connectToTerminal(new TerminalFileImpl(this).stub);
    terminalClient.close();
  }

  // |TerminalDisplay| implementation:

  @override
  void putChar(int byte) {
    // Fast-path for printable chars.
    if (byte >= 32) {
      _control.lastChild.textContent += new String.fromCharCode(byte);
      return;
    }

    switch (byte) {
      case 8:  // BS (^H).
        _backspace();
        break;
      case 10:  // LF ('\n').
        _newLine();  // TODO(vtl): LF and CR should be separated.
        break;
      case 12:  // FF (^L).
        _clear();
        break;
      case 13:  // CR ('\r').
        _newLine();  // TODO(vtl): LF and CR should be separated.
        break;
      default:
        // Should beep or something.
        break;
    }
  }

  @override
  Future<int> getChar() async {
    if (_inputQueue.isNotEmpty) {
      return new Future.value(_inputQueue.removeAt(0));
    }

    var completer = new Completer<int>();
    _readerQueue.add(completer);
    return completer.future;
  }
}

_init(script) => register(script, TerminalDisplayImpl);
</script>
</sky-element>