import json
import os
import random
import string

import requests
import vim

from . import diff

BASE_URL = 'https://via.ce9e.org/hmsg/pad/'

session = requests.Session()
pads = {}


def get_selection(window):
	row, col = window.cursor
	pos = sum([len(line) + 1 for line in window.buffer[:(row - 1)]]) + col
	return [pos, pos]


def set_selection(window, selection):
	row, col = 0, selection[0]
	for line in window.buffer:
		if col > len(line):
			col -= len(line) + 1
			row += 1
		else:
			window.cursor = row + 1, col
			break


class Pad:
	def __init__(self, buffer):
		self.id = ''.join(random.sample(string.hexdigits, 6))
		self.buffer = buffer
		self.local_changes = []
		self.staged_changes = []
		self.old = self.get_text()
		self.last_event_id = 0

		self.name = os.path.basename(buffer.name).removesuffix('.pad')
		self.url = BASE_URL + self.name

	def get_text(self):
		return '\n'.join(self.buffer[:])

	def start_listen(self):
		vim.command(
			f'let g:pad_curl_{self.buffer.number} = job_start('
				f'["curl", "-N", "{self.url}"], '
				f'{{"out_cb": function("pad#on_channel", [{self.buffer.number}])}}'
			')'
		)

	def stop_listen(self):
		vim.command(f'call job_stop(g:pad_curl_{self.buffer.number})')

	def on_input(self):
		text = self.get_text()
		change = diff.diff(self.old, text, 3)
		diff.push_change(self.local_changes, change)
		self.old = text

	def send_changes(self):
		if self.staged_changes:
			# TODO: retry again later
			print('abort because of staged changes')
		else:
			self.staged_changes = self.local_changes
			self.local_changes = []
			data = [self.id, 'changes', self.staged_changes]
			try:
				r = session.post(self.url, json=data)
				r.raise_for_status()
			except Exception as e:
				print(e)
				self.local_changes = [*self.staged_changes, *self.local_changes]
				self.staged_changes = []

	def apply_changes(self, changes):
		if vim.current.window.buffer == self.buffer:
			selection = get_selection(vim.current.window)
		else:
			selection = None
		text = self.get_text()
		prior = text
		my_changes = [*self.staged_changes, *self.local_changes]

		for change in reversed(my_changes):
			text = diff.unapply(text, change, selection)

		for change in changes:
			text = diff.apply(text, change, selection)

		for change in my_changes:
			text = diff.apply(text, change, selection)

		if text != prior:
			self.buffer[:] = text.split('\n')
			if vim.current.window.buffer == self.buffer:
				set_selection(vim.current.window, selection)
			self.old = text

	def reset_modified(self):
		mod = bool(self.local_changes or self.staged_changes)
		self.buffer.options['modified'] = mod

	def optimize(self):
		text = self.get_text()
		my_changes = [*self.staged_changes, *self.local_changes]

		for change in reversed(my_changes):
			text = diff.unapply(text, change)

		change = diff.diff('', text, 3)
		data = [self.id, 'changes', [change]]
		session.put(self.url, json=data, headers={
			'Last-Event-ID': self.last_event_id
		})


def get_buffer():
	return int(vim.eval('expand("<abuf>")'), 10)


def on_open():
	i = get_buffer()
	pad = Pad(vim.buffers[i])
	pads[i] = pad
	pad.start_listen()
	print(f'Connected to {pad.url}')


def on_input():
	pad = pads[get_buffer()]
	pad.on_input()


def on_write():
	pad = pads[get_buffer()]
	pad.send_changes()


def on_close():
	pad = pads.pop(get_buffer())
	pad.stop_listen()


def on_channel(i, msg):
	pad = pads[i]

	if msg.startswith('data: '):
		data = json.loads(msg.split(': ', 1)[1])
		if data[1] == 'changes':
			if data[0] == pad.id:
				pad.staged_changes = []
			else:
				pad.apply_changes(data[2])
			pad.reset_modified()

			if (random.random() < 0.05):
				pad.optimize()
	elif msg.startswith('id: '):
		pad.last_event_id = msg.split(': ', 1)[1]