#!/usr/bin/env python3

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import http.server
import sys
import urllib.request

timeout = 5

pathprefix = None
base_url = None

class Proxy(http.server.BaseHTTPRequestHandler):
	server_version = 'Oftgophproxy/0.1'

	def error(self, code, text):
		contents = text.encode('utf-8')

		self.send_response(code)
		self.send_header('Content-Type', 'text/plain; charset=utf-8')
		self.send_header('Content-Length', len(contents))
		self.end_headers()
		self.wfile.write(contents)

	def do_GET(self):
		if self.path[:len(pathprefix)] == pathprefix:
			path = self.path[len(pathprefix):]
		else:
			path = self.path

		if len(path) > 0 and path[0] != '/':
			path = '/' + path

		request_url = base_url + path

		try:
			r = urllib.request.urlopen(request_url, timeout = timeout)
		except urllib.error.HTTPError as err:
			if err.code == 400:
				self.error(400, 'Remote returned 400 Bad Request\n\nMake sure you remembered to use the itemtype')
			else:
				self.error(502, 'Remote returned %i %s' % (err.code, err.reason))
			return

		except urllib.error.URLError as err:
			self.error(502, 'Could not connect to remote')
			return

		mimetype = None
		for key, value in r.info().items():
			if key.lower() == 'content-type':
				mimetype = value

		if mimetype is None:
			self.error(502, 'Remote did not include content-type')
			return

		contents = r.read()

		self.send_response(200)
		self.send_header('Content-Type', mimetype)
		self.send_header('Content-Length', len(contents))
		self.end_headers()
		self.wfile.write(contents)

def main():
	global pathprefix
	global base_url

	if len(sys.argv) != 4:
		print('Usage: %s port pathprefix remote' % sys.argv[0], file=sys.stderr)
		sys.exit(1)

	try:
		port = int(sys.argv[1])
	except ValueError:
		print('%s: Error: "%s" not a valid port number' % sys.argv[0], file=sys.stderr)
		sys.exit(1)

	if port <= 0 or port >= (2**16):
		print('%s: Error: Port number %i out of valid range' % (sys.argv[0], port))
		sys.exit(1)

	pathprefix = sys.argv[2]

	base_url = sys.argv[3]

	http.server.HTTPServer(('', port), Proxy).serve_forever()

if __name__ == '__main__':
	main()