from engel.application import Application, View

from engel.widgets.structure import List
from engel.widgets.forms import Button, TextBox
from engel.widgets.text import Title, Span

from engel.libraries import bootstrap4

import os


class FileService(object):
  """Services are the main way of interacting with the outside world with Engel.
  This service encapsulates all interactions with our file, and will be made
  available to our application.
  """
  def __init__(self):
    if not os.path.isfile('myfile.txt'):
      open('myfile.txt', 'a').close()

  def get_all(self):
    with open("myfile.txt", "rU") as infile:
      return list(filter(bool, infile.readlines()))

  def add(self, txt):
    with open("myfile.txt", "a") as outfile:
      outfile.write(txt + "\n")


class MainFileView(View):
  """With Engel, views represent the structure of the page currently displayed
  as well as the different actions handled by the program.
  """
  title = "MyFile.txt"

  current_id = 0

  libraries = [bootstrap4]

  def build(self):
    """The build() method is called when the application is rendering the page to
    HTML. It is responsible for building the DOM and enqueuing the event handlers required by the view.
    """

    # We create a bootstrap Container() object and anchor it to the root of the page.
    main_panel = bootstrap4.Container(id="containerMain", parent=self.root)
    Title(id="pageTitle", text="Contents of myfile.txt", parent=main_panel)

    # Here, we define a List() object. Contrary to Container(), List() is more than
    # a simple wrapper around <ul>. The List object provides an interface very similar to python's list,
    # and at the same time provides the auto-updating capabilities of Engel widgets.
    self.lines_list = List(id="lstLines", parent=main_panel)

    # We get the list of active services from the view's context & call the
    # method allowing us to retrieve all lines in the file.
    for ln in self.context.services["FileService"].get_all():
      self.append_line(ln)

    self.txtNew = TextBox(id="txtNew", name="txtNew", parent=main_panel)
    btn = Button(id="btnSubmit", text="Add Line", parent=main_panel)

    # Note: The framework handles seamlessly the forwarding of events from the
    # client to the server, so we can set a server-side method as callback
    # for a client event.
    self.on(event="click", callback=self.create_line, selector="#" + btn.id)

  def append_line(self, ln):
    self.lines_list.append(Span(id="line_" + str(self.current_id), text=ln))
    self.current_id += 1

  def create_line(self, event, interface):
    new_line = self.txtNew.text
    self.context.services["FileService"].add(new_line)
    self.append_line(new_line)

    # Note: The framework also handles the updating of client widgets from the server. This means
    # that the HTML view is guaranteed to always be in sync with your python objects.
    self.txtNew.text = ""


class FileApp(Application):
  """The Application object is the central object tying your Engel app together.
  It holds all the information common to all views, as well as view and service
  definitions.
  """

  # The base title of the app.
  # The actual title of the page is set by App.base_title.format(view.title)
  base_title = "{0} | TextFileManager"

  def __init__(self, debug=False):
    super(FileApp, self).__init__(debug)

    self.views["default"] = MainFileView

    # Services are instanciated on app startup and are kept running for the
    # entire lifetime of the app.
    self.services["FileService"] = FileService


if __name__ == "__main__":
  app = FileApp(debug=True)
  app.start()