import struct
import sys
import threading
from queue import Queue


import tkinter as Tkinter
from tkinter import messagebox as tkMessageBox

if sys.platform == "win32":
    import os, msvcrt

    msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)


def send_message(message):
    sys.stdout.write(str(len(message)))
    sys.stdout.write(message)
    sys.stdout.flush()


def read_thread_func(queue):
    message_number = 0
    while 1:
        text_length_bytes = sys.stdin.read(4)
        if len(text_length_bytes) == 0:
            if queue:
                queue.put(None)
            sys.exit(0)

        text_length = struct.unpack("i", text_length_bytes)[0]
        text = sys.stdin.read(text_length).decode("utf-8")

        if queue:
            queue.put(text)
        else:
            send_message('{"echo": %s}' % text)


if Tkinter:

    class NativeMessagingWindow(Tkinter.Frame):
        def __init__(self, queue):
            self.queue = queue

            Tkinter.Frame.__init__(self)
            self.pack()

            self.text = Tkinter.Text(self)
            self.text.grid(row=0, column=0, padx=10, pady=10, columnspan=2)
            self.text.config(state=Tkinter.DISABLED, height=10, width=40)

            self.messageContent = Tkinter.StringVar()
            self.sendEntry = Tkinter.Entry(self, textvariable=self.messageContent)
            self.sendEntry.grid(row=1, column=0, padx=10, pady=10)

            self.sendButton = Tkinter.Button(self, text="Send", command=self.onSend)
            self.sendButton.grid(row=1, column=1, padx=10, pady=10)

            self.after(100, self.processMessages)

        def processMessages(self):
            while not self.queue.empty():
                message = self.queue.get_nowait()
                if message == None:
                    self.quit()
                    return
                self.log("Received %s" % message)

            self.after(100, self.processMessages)

        def onSend(self):
            text = '{"text": "' + self.messageContent.get() + '"}'
            self.log("Sending %s" % text)
            try:
                send_message(text)
            except IOError:
                tkMessageBox.showinfo(
                    "Native Messaging Example", "Failed to send message."
                )
                sys.exit(1)

        def log(self, message):
            self.text.config(state=Tkinter.NORMAL)
            self.text.insert(Tkinter.END, message + "\n")
            self.text.config(state=Tkinter.DISABLED)


def Main():
    if not Tkinter:
        send_message(
            "\"Tkinter python module wasn't found. Running in headless "
            + 'mode. Please consider installing Tkinter."'
        )
        read_thread_func(None)
        sys.exit(0)

    queue = Queue()

    main_window = NativeMessagingWindow(queue)
    main_window.master.title("Native Messaging Example")

    thread = threading.Thread(target=read_thread_func, args=(queue,))
    thread.daemon = True
    thread.start()
    main_window.mainloop()
    sys.exit(0)


if __name__ == "__main__":
    Main()