/**
 * # Terminal Riot Tag
 *
 * Provides a pretend commandline interface, capable of displaying output from a
 * "shell" javascript class. Multiple terminal tags can be used on a page, using
 * the same shell class or different ones - each terminal will work
 * independently.
 *
 * ## Defaults
 *
 * The default prompt is `'$'`. There is no default the welcome message. The
 * default shell performs no actions: pressing enter will simply move the cursor
 * to the next prompt line.
 *
 * ## Usage
 *
 *     <terminal shell='jsclass' welcome='text' prompt='text'></terminal>
 *
 *     <script src='riot+compiler.min.js'></script>
 *     <script src='he.js'></script>
 *     <script src='shell.js'></script>
 *     <script src='terminal.tag' type='riot/tag'></script>
 *     <script>riot.mount('terminal')</script>
 *
 * ## Dependencies
 *
 * - riot.js (http://riotjs.com/)
 * - he.js (https://github.com/mathiasbynens/he) for HTML Entity conversion.
 *
 * ## Making A Shell Class
 *
 * The shell class must be defined before the tag is mounted. Shells can keep
 * prompt and welcome message settings, and must define a `process()` function.
 * Here is the structure of a minimal shell that does nothing:
 *
 *     // Contents of myshell.js
 *     function() myshell() {
 *        this.prompt = ''
 *        this.welcome = ''
 *        this.process = function(input) {
 *          return ''
 *        }
 *     }
 *
 *     // shell class used by Terminal Riot Tag in index.html
 *     <terminal shell='myshell'></terminal>
 *
 * ## Special Shell Return Values
 *
 * The terminal tag recognises some predefined shell return values and upon
 * receiving them, can perform actions other than printing output:
 *
 * - `'clear'`. Terminal will clear its output history.
 *
 */
<terminal>
  <history welcome={ welcome } />
  <commandline prompt={ prompt } />

  // Take defaults from shell, otherwise take from terminal tag options.
  var shell = { 'process': function() { return ''; } }
  this.shell = window[opts.shell] ? new window[opts.shell] : shell
  this.welcome = this.shell.welcome ? this.shell.welcome : opts.welcome
  this.prompt = this.shell.prompt ? this.shell.prompt : opts.prompt

  /**
   * How to process a command:
   * - Make the input safe by transforming html entities.
   * - Keep the last command in history as we go to the next line.
   * - Based on shell response, perform special actions or append the output.
   * - Update the prompt as required.
   */
  process(prompt, input) {
    input = he.encode(input)
    var output = prompt + input + '\n'
    var response = this.shell.process(input)
    switch(response) {
      case 'clear':
        this.clear()
        break
      default:
        this.tags.history.add(output + response)
    }
    this.tags.commandline.setPrompt(this.shell.prompt)
    this.tags.commandline.command.value = ''
  }

  clear() {
    this.tags.history.hist = []
    this.update()
  }
</terminal>

<commandline>
  <form autocomplete='off' onsubmit={ process }>
    <raw name='lhs' content={ prompt } /><input type='text' name='command' />
  </form>

  <style>
    input[name='command'] {
      background: transparent;
      border: none; outline: none;
      padding: 0; margin: 0;
      width: 90%;
    }
  </style>

  this.on('mount', function() {
    document.getElementsByName('command')[0].focus()
  })

  /**
   * Set the prompt to any truthy value.
   *
   * Note about `lhs.write()` check:
   * Terminal tag setup fires `setPrompt()` before `lhs.write()` exists.
   * At that point, `lhs` is initialised with just its `content` attribute.
   * After that, `lhs.write()` is called to make all subsequent prompt changes.
   */
  setPrompt(value) {
    if (value) {
      if (typeof this.tags.lhs.write != 'undefined') {
        this.tags.lhs.write(value)
      }
      this.update({ 'prompt': value })
    }
  }

  process(e) {
    this.parent.process(this.prompt, this.command.value)
  }

  this.prompt = '$ '
  this.setPrompt(opts.prompt)
</commandline>

<history>
  <div each={ hist }>
    <raw content={ content } />
  </div>

  add(output) {
    if (output) {
      output = this.preserveWhiteSpace(output)
      this.hist.push({ 'content': output })
      this.update()
    }
  }

  /**
   * Make sure whitespace displays correctly.
   *
   * Keep the following:
   *
   * - Newlines.
   * - Whitespace for display. This means all spaces that are not within tags.
   */
  preserveWhiteSpace(text) {
    text = text.replace(/(?:\r\n|\r|\n)/g, '<br />')
    // Search for tags or whitespace. Replace whitespace, leave the tags.
    text = text.replace(/<[^<]+>|( )/g, function(match, group1) {
      if (group1 == " ") { return '&nbsp;' }
      return match
    })
    return text
  }

  this.hist = []
  this.add(opts.welcome)
</history>

<raw>
  <span></span>

  // Initialise contents from tag options, but expose `write()` for updating.
  write(value) {
    this.root.innerHTML = value
  }
  this.write(opts.content)
</raw>