"""Loopback teaching adapter. Not a production HTTP server."""
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from pipeline import decode, encode, predict


def server(bundle, version, port=0):
    class Handler(BaseHTTPRequestHandler):
        def log_message(self, *_):
            pass

        def reply(self, status, value):
            data = encode(value)
            self.send_response(status)
            self.send_header('Content-Type', 'application/json')
            self.send_header('Content-Length', str(len(data)))
            self.end_headers()
            self.wfile.write(data)

        def do_POST(self):
            if self.path != '/predict':
                self.reply(404, {'error': 'unknown route'})
                return
            try:
                size = int(self.headers.get('Content-Length', '0'))
                if not 0 < size <= 4096:
                    self.reply(413, {'error': 'body must be 1..4096 bytes'})
                    return
                if self.headers.get_content_type() != 'application/json':
                    self.reply(415, {'error': 'application/json required'})
                    return
                data = self.rfile.read(size)
                self.reply(200, predict(bundle, decode(data), version))
            except (ValueError, TypeError, OverflowError):
                self.reply(422, {'error': 'invalid prediction request'})
    service = ThreadingHTTPServer(('127.0.0.1', port), Handler)
    service.timeout = 2
    return service