#!/usr/bin/env python3

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import base64
import html
import http.server
import os
import sys
import urllib.parse

files = {}

def gen_id():
	return base64.urlsafe_b64encode(os.urandom(48 * 6 // 8)).decode()

def process_file(file_id):
	r = []
	for line in files[file_id]:
		r.append('<code>%s</code>' % html.escape(line))

	return '\n'.join(r)

def run_command(keyvalues):
	file_id = keyvalues['id'][-1]
	cmd = keyvalues['cmd'][-1]
	linenum = int(keyvalues['linenum'][-1])

	assert cmd in ['append', 'delete']

	if cmd == 'append':
		line = keyvalues['line'][-1]
		before = files[file_id][:linenum]
		after = files[file_id][linenum:]
		files[file_id] = before + [line] + after

	elif cmd == 'delete':
		assert 0 < linenum <= len(files[file_id])
		del files[file_id][linenum - 1]

class WebEd(http.server.BaseHTTPRequestHandler):
	def redirect(self, path):
		self.send_response(303)
		self.send_header('Content-Type', 'text/plain; charset=utf-8')
		self.send_header('Content-Length', 0)
		self.send_header('Location', path)
		self.end_headers()

	def send_html(self, html, status_code = 200):
		encoded = html.encode('utf-8')
		length = len(encoded)

		self.send_response(status_code)
		self.send_header('Content-Type', 'text/html; charset=utf-8')
		self.send_header('Content-Length', length)
		self.end_headers()

		self.wfile.write(encoded)

	def do_GET(self):
		url, _, keyvalues = self.path.partition('?')
		keyvalues = urllib.parse.parse_qs(keyvalues)

		if url == '/' and 'id' not in keyvalues:
			# Generate new ID
			file_id = gen_id()
			self.redirect('%s?id=%s' % (url, file_id))

		elif 'id' not in keyvalues:
			self.send_html("""
				<!DOCTYPE html>
				<html>
					<head>
						<title>404 Not Found</title>
					</head>
					<body>
						<p>404 Not Found</p>
					</body>
				</html>
			""", 404)

		else:
			file_id = keyvalues['id'][-1]

			if file_id not in files:
				files[file_id] = []

			if 'cmd' in keyvalues:
				try:
					run_command(keyvalues)

				except Exception as err:
					self.send_html("""
						<!DOCTYPE html>
						<html>
							<head>
								<title>400 Bad Request</title>
							</head>
							<body>
								<p>400 Bad Request</p>
							</body>
						</html>
					""", 400)
					return

				self.redirect('%s?id=%s' % (url, file_id))

			self.send_html("""<!DOCTYPE html>
				<html>
					<head>
						<title>WebEd</title>
						<style type="text/css">
							pre { white-space: pre-wrap; counter-reset: linenum; }
							code::before { counter-increment: linenum; content: counter(linenum) " "; }
						</style>
					</head>
					<body>
						<p>
							<pre>%s</pre>
						</p>
						<p>
							<form action="" method="get">
								<input type="hidden" name="id" value="%s"/>
								<ul>
									<li>
										<label for="append">append</label>
										<input type="radio" checked="true" name="cmd" id="append" value="append"/>
									</li>
									<li>
										<label for="delete">delete</label>
										<input type="radio" name="cmd" id="delete" value="delete"/>
									</li>
								</ul>
								<label>Line</label>
								<input type="number" name="linenum" min="0" max="%i" value="%i"/>
								<input type="input" name="line"/>
								<input type="submit" value="run"/>
							</form>
						</p>
					</body>
				</html>""" % (process_file(file_id), file_id, len(files[file_id]), len(files[file_id])))

def main():
	http.server.HTTPServer(('', int(sys.argv[1])), WebEd).serve_forever()

if __name__ == '__main__':
	main()