from mitmproxy import log
from mitmproxy import exceptions
from mitmproxy.net import tls
from mitmproxy.proxy import protocol
from mitmproxy.proxy import modes
from mitmproxy.proxy.protocol import http


class RootContext:

    """
    The outermost context provided to the root layer.
    As a consequence, every layer has access to methods and attributes defined here.

    Attributes:
        client_conn:
            The :py:class:`client connection <mitmproxy.connections.ClientConnection>`.
        channel:
            A :py:class:`~mitmproxy.controller.Channel` to communicate with the FlowMaster.
            Provides :py:meth:`.ask() <mitmproxy.controller.Channel.ask>` and
            :py:meth:`.tell() <mitmproxy.controller.Channel.tell>` methods.
        config:
            The :py:class:`proxy server's configuration <mitmproxy.proxy.ProxyConfig>`
    """

    def __init__(self, client_conn, config, channel):
        self.client_conn = client_conn
        self.channel = channel
        self.config = config

    def next_layer(self, top_layer):
        """
        This function determines the next layer in the protocol stack.

        Arguments:
            top_layer: the current innermost layer.

        Returns:
            The next layer
        """
        layer = self._next_layer(top_layer)
        return self.channel.ask("next_layer", layer)

    def _next_layer(self, top_layer):
        try:
            d = top_layer.client_conn.rfile.peek(3)
        except exceptions.TcpException as e:
            raise exceptions.ProtocolException(str(e))
        client_tls = tls.is_tls_record_magic(d)

        # 1. check for filter
        if self.config.check_filter:
            is_filtered = self.config.check_filter(top_layer.server_conn.address)
            if not is_filtered and client_tls:
                try:
                    client_hello = tls.ClientHello.from_file(self.client_conn.rfile)
                except exceptions.TlsProtocolException as e:
                    self.log("Cannot parse Client Hello: %s" % repr(e), "error")
                else:
                    sni_str = client_hello.sni and client_hello.sni.decode("idna")
                    is_filtered = self.config.check_filter((sni_str, 443))
            if is_filtered:
                return protocol.RawTCPLayer(top_layer, ignore=True)

        # 2. Always insert a TLS layer, even if there's neither client nor server tls.
        # An inline script may upgrade from http to https,
        # in which case we need some form of TLS layer.
        if isinstance(top_layer, modes.ReverseProxy):
            return protocol.TlsLayer(
                top_layer,
                client_tls,
                top_layer.server_tls,
                top_layer.server_conn.address[0]
            )
        if isinstance(top_layer, protocol.ServerConnectionMixin):
            return protocol.TlsLayer(top_layer, client_tls, client_tls)
        if isinstance(top_layer, protocol.UpstreamConnectLayer):
            # if the user manually sets a scheme for connect requests, we use this to decide if we
            # want TLS or not.
            if top_layer.connect_request.scheme:
                server_tls = top_layer.connect_request.scheme == "https"
            else:
                server_tls = client_tls
            return protocol.TlsLayer(top_layer, client_tls, server_tls)

        # 3. In Http Proxy mode and Upstream Proxy mode, the next layer is fixed.
        if isinstance(top_layer, protocol.TlsLayer):
            if isinstance(top_layer.ctx, modes.HttpProxy):
                return protocol.Http1Layer(top_layer, http.HTTPMode.regular)
            if isinstance(top_layer.ctx, modes.HttpUpstreamProxy):
                return protocol.Http1Layer(top_layer, http.HTTPMode.upstream)

        # 4. Check for other TLS cases (e.g. after CONNECT).
        if client_tls:
            return protocol.TlsLayer(top_layer, True, True)

        # 4. Check for --tcp
        if self.config.check_tcp(top_layer.server_conn.address):
            return protocol.RawTCPLayer(top_layer)

        # 5. Check for TLS ALPN (HTTP1/HTTP2)
        if isinstance(top_layer, protocol.TlsLayer):
            alpn = top_layer.client_conn.get_alpn_proto_negotiated()
            if alpn == b'h2':
                return protocol.Http2Layer(top_layer, http.HTTPMode.transparent)
            if alpn == b'http/1.1':
                return protocol.Http1Layer(top_layer, http.HTTPMode.transparent)

        # 6. Check for raw tcp mode
        is_ascii = (
            len(d) == 3 and
            # expect A-Za-z
            all(65 <= x <= 90 or 97 <= x <= 122 for x in d)
        )
        if self.config.options.rawtcp and not is_ascii:
            return protocol.RawTCPLayer(top_layer)

        # 7. Assume HTTP1 by default
        return protocol.Http1Layer(top_layer, http.HTTPMode.transparent)

    def log(self, msg, level, subs=()):
        """
        Send a log message to the master.
        """
        full_msg = [
            "{}:{}: {}".format(self.client_conn.address[0], self.client_conn.address[1], msg)
        ]
        for i in subs:
            full_msg.append("  -> " + i)
        full_msg = "\n".join(full_msg)
        self.channel.tell("log", log.LogEntry(full_msg, level))