mitmproxy/libmproxy/console/flowview.py

from __future__ import absolute_import
import os, sys, copy
import urwid
from . import common, grideditor, contentview, signals
from .. import utils, flow, controller
from ..protocol.http import HTTPRequest, HTTPResponse, CONTENT_MISSING, decoded


class SearchError(Exception): pass


def _mkhelp():
    text = []
    keys = [
        ("A", "accept all intercepted flows"),
        ("a", "accept this intercepted flow"),
        ("b", "save request/response body"),
        ("d", "delete flow"),
        ("D", "duplicate flow"),
        ("e", "edit request/response"),
        ("f", "load full body data"),
        ("g", "copy response(content/headers) to clipboard"),
        ("m", "change body display mode for this entity"),
            (None,
                common.highlight_key("automatic", "a") +
                [("text", ": automatic detection")]
            ),
            (None,
                common.highlight_key("hex", "e") +
                [("text", ": Hex")]
            ),
            (None,
                common.highlight_key("html", "h") +
                [("text", ": HTML")]
            ),
            (None,
                common.highlight_key("image", "i") +
                [("text", ": Image")]
            ),
            (None,
                common.highlight_key("javascript", "j") +
                [("text", ": JavaScript")]
            ),
            (None,
                common.highlight_key("json", "s") +
                [("text", ": JSON")]
            ),
            (None,
                common.highlight_key("urlencoded", "u") +
                [("text", ": URL-encoded data")]
            ),
            (None,
                common.highlight_key("raw", "r") +
                [("text", ": raw data")]
            ),
            (None,
                common.highlight_key("xml", "x") +
                [("text", ": XML")]
            ),
        ("M", "change default body display mode"),
        ("p", "previous flow"),
        ("r", "replay request"),
        ("V", "revert changes to request"),
        ("v", "view body in external viewer"),
        ("w", "save all flows matching current limit"),
        ("W", "save this flow"),
        ("x", "delete body"),
        ("X", "view flow details"),
        ("z", "encode/decode a request/response"),
        ("tab", "toggle request/response view"),
        ("space", "next flow"),
        ("|", "run script on this flow"),
        ("/", "search in response body (case sensitive)"),
        ("n", "repeat search forward"),
        ("N", "repeat search backwards"),
    ]
    text.extend(common.format_keyvals(keys, key="key", val="text", indent=4))
    return text
help_context = _mkhelp()

footer = [
    ('heading_key', "?"), ":help ",
    ('heading_key', "q"), ":back ",
]


class FlowViewHeader(urwid.WidgetWrap):
    def __init__(self, master, f):
        self.master, self.flow = master, f
        self._w = common.format_flow(
            f,
            False,
            extended=True,
            padding=0,
            hostheader=self.master.showhost
        )
        signals.flow_change.connect(self.sig_flow_change)

    def sig_flow_change(self, sender, flow):
        if flow == self.flow:
            self._w = common.format_flow(
                flow,
                False,
                extended=True,
                padding=0,
                hostheader=self.master.showhost
            )


cache = utils.LRUCache(200)


class FlowView(urwid.WidgetWrap):
    highlight_color = "focusfield"

    def __init__(self, master, state, flow):
        self.master, self.state, self.flow = master, state, flow
        self.last_displayed_body = None
        if self.state.view_flow_mode == common.VIEW_FLOW_RESPONSE:
            self.view_response()
        else:
            self.view_request()
        signals.flow_change.connect(self.sig_flow_change)

    def sig_flow_change(self, sender, flow):
        if flow == self.flow:
            if self.state.view_flow_mode == common.VIEW_FLOW_RESPONSE and self.flow.response:
                self.view_response()
            else:
                self.view_request()

    def _cached_content_view(self, viewmode, hdrItems, content, limit, is_request):
        return contentview.get_content_view(
            viewmode,
            hdrItems,
            content,
            limit,
            self.master.add_event,
            is_request
        )

    def content_view(self, viewmode, conn):
        full = self.state.get_flow_setting(
            self.flow,
            (self.state.view_flow_mode, "fullcontents"),
            False
        )
        if full:
            limit = sys.maxint
        else:
            limit = contentview.VIEW_CUTOFF
        description, text_objects = cache.get(
                    self._cached_content_view,
                    viewmode,
                    tuple(tuple(i) for i in conn.headers.lst),
                    conn.content,
                    limit,
                    isinstance(conn, HTTPRequest)
                )
        return (description, text_objects)

    def cont_view_handle_missing(self, conn, viewmode):
            if conn.content == CONTENT_MISSING:
                msg, body = "", [urwid.Text([("error", "[content missing]")])]
            else:
                msg, body = self.content_view(viewmode, conn)

            return (msg, body)

    def viewmode_get(self, override):
        return self.state.default_body_view if override is None else override

    def override_get(self):
        return self.state.get_flow_setting(self.flow,
                (self.state.view_flow_mode, "prettyview"))

    def conn_text_raw(self, conn):
        """
            Based on a request/response, conn, returns the elements for
            display.
        """
        headers = common.format_keyvals(
                [(h+":", v) for (h, v) in conn.headers.lst],
                key = "header",
                val = "text"
            )
        override = self.override_get()
        viewmode = self.viewmode_get(override)
        msg, body = self.cont_view_handle_missing(conn, viewmode)
        return headers, msg, body

    def conn_text_merge(self, headers, msg, body):
        """
            Grabs what is returned by conn_text_raw and merges them all
            toghether, mainly used by conn_text and search
        """
        override = self.override_get()
        viewmode = self.viewmode_get(override)

        cols = [urwid.Text(
                [
                    ("heading", msg),
                ]
            )
        ]

        if override is not None:
            cols.append(urwid.Text([
                        " ",
                        ('heading', "["),
                        ('heading_key', "m"),
                        ('heading', (":%s]"%viewmode.name)),
                    ],
                    align="right"
                )
            )

        title = urwid.AttrWrap(urwid.Columns(cols), "heading")
        headers.append(title)
        headers.extend(body)

        return headers

    def conn_text(self, conn):
        """
        Same as conn_text_raw, but returns result wrapped in a listbox ready for
        usage.
        """
        headers, msg, body = self.conn_text_raw(conn)
        merged = self.conn_text_merge(headers, msg, body)
        return urwid.ListBox(merged)

    def _tab(self, content, attr):
        p = urwid.Text(content)
        p = urwid.Padding(p, align="left", width=("relative", 100))
        p = urwid.AttrWrap(p, attr)
        return p

    def wrap_body(self, active, body):
        parts = []

        if self.flow.intercepted and not self.flow.reply.acked and not self.flow.response:
            qt = "Request intercepted"
        else:
            qt = "Request"
        if active == common.VIEW_FLOW_REQUEST:
            parts.append(self._tab(qt, "heading"))
        else:
            parts.append(self._tab(qt, "heading_inactive"))

        if self.flow.intercepted and not self.flow.reply.acked and self.flow.response:
            st = "Response intercepted"
        else:
            st = "Response"
        if active == common.VIEW_FLOW_RESPONSE:
            parts.append(self._tab(st, "heading"))
        else:
            parts.append(self._tab(st, "heading_inactive"))

        h = urwid.Columns(parts)
        f = urwid.Frame(
                    body,
                    header=h
                )
        return f

    def search_wrapped_around(self, last_find_line, last_search_index, backwards):
        """
            returns true if search wrapped around the bottom.
        """

        current_find_line = self.state.get_flow_setting(self.flow,
                "last_find_line")
        current_search_index = self.state.get_flow_setting(self.flow,
                "last_search_index")

        if not backwards:
            message = "search hit BOTTOM, continuing at TOP"
            if current_find_line <= last_find_line:
                return True, message
            elif current_find_line == last_find_line:
                if current_search_index <= last_search_index:
                    return True, message
        else:
            message = "search hit TOP, continuing at BOTTOM"
            if current_find_line >= last_find_line:
                return True, message
            elif current_find_line == last_find_line:
                if current_search_index >= last_search_index:
                    return True, message

        return False, ""

    def search_again(self, backwards=False):
        """
            runs the previous search again, forwards or backwards.
        """
        last_search_string = self.state.get_flow_setting(
            self.flow, "last_search_string"
        )
        if last_search_string:
            message = self.search(last_search_string, backwards)
            if message:
                signals.status_message.send(message=message)
        else:
            message = "no previous searches have been made"
            signals.status_message.send(message=message)

        return message

    def search(self, search_string, backwards=False):
        """
            similar to view_response or view_request, but instead of just
            displaying the conn, it highlights a word that the user is
            searching for and handles all the logic surrounding that.
        """

        if not search_string:
            search_string = self.state.get_flow_setting(self.flow,
                    "last_search_string")
            if not search_string:
                return

        if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            text = self.flow.request
            const = common.VIEW_FLOW_REQUEST
        else:
            text = self.flow.response
            const = common.VIEW_FLOW_RESPONSE
            if not self.flow.response:
                return "no response to search in"

        last_find_line = self.state.get_flow_setting(self.flow,
                "last_find_line")
        last_search_index = self.state.get_flow_setting(self.flow,
                "last_search_index")

        # generate the body, highlight the words and get focus
        headers, msg, body = self.conn_text_raw(text)
        try:
            body, focus_position = self.search_highlight_text(
                body,
                search_string,
                backwards=backwards
            )
        except SearchError:
            return "Search not supported in this view."

        if focus_position == None:
            # no results found.
            return "no matches for '%s'" % search_string

        # UI stuff.
        merged = self.conn_text_merge(headers, msg, body)
        list_box = urwid.ListBox(merged)
        list_box.set_focus(focus_position + 2)
        self._w = self.wrap_body(const, list_box)
        signals.update_settings.send(self)

        self.last_displayed_body = list_box

        wrapped, wrapped_message = self.search_wrapped_around(
            last_find_line,
            last_search_index,
            backwards
        )

        if wrapped:
            return wrapped_message

    def search_get_start(self, search_string):
        start_line = 0
        start_index = 0
        last_search_string = self.state.get_flow_setting(
            self.flow,
            "last_search_string"
        )
        if search_string == last_search_string:
            start_line = self.state.get_flow_setting(
                self.flow,
                "last_find_line"
            )
            start_index = self.state.get_flow_setting(self.flow,
                    "last_search_index")

            if start_index == None:
                start_index = 0
            else:
                start_index += len(search_string)

            if start_line == None:
                start_line = 0

        else:
            self.state.add_flow_setting(self.flow, "last_search_string",
                    search_string)

        return (start_line, start_index)

    def search_get_range(self, len_text_objects, start_line, backwards):
        if not backwards:
            loop_range = xrange(start_line, len_text_objects)
        else:
            loop_range = xrange(start_line, -1, -1)

        return loop_range

    def search_find(self, text, search_string, start_index, backwards):
            if backwards == False:
                find_index = text.find(search_string, start_index)
            else:
                if start_index != 0:
                    start_index -= len(search_string)
                else:
                    start_index = None

                find_index = text.rfind(search_string, 0, start_index)

            return find_index

    def search_highlight_text(self, text_objects, search_string, looping = False, backwards = False):
        start_line, start_index = self.search_get_start(search_string)
        i = start_line

        found = False
        text_objects = copy.deepcopy(text_objects)
        loop_range = self.search_get_range(
            len(text_objects),
            start_line, backwards
        )
        for i in loop_range:
            text_object = text_objects[i]

            try:
                text, style = text_object.get_text()
            except AttributeError:
                raise SearchError()

            if i != start_line:
                start_index = 0

            find_index = self.search_find(
                text,
                search_string,
                start_index,
                backwards
            )

            if find_index != -1:
                new_text = self.search_highlight_object(
                    text,
                    find_index,
                    search_string
                )
                text_objects[i] = new_text

                found = True
                self.state.add_flow_setting(self.flow, "last_search_index",
                        find_index)
                self.state.add_flow_setting(self.flow, "last_find_line", i)

                break

        # handle search WRAP
        if found:
            focus_pos = i
        else :
            if looping:
                focus_pos = None
            else:
                if not backwards:
                    self.state.add_flow_setting(
                        self.flow, "last_search_index", 0
                    )
                    self.state.add_flow_setting(
                        self.flow, "last_find_line", 0
                    )
                else:
                    self.state.add_flow_setting(
                        self.flow, "last_search_index", None
                    )
                    self.state.add_flow_setting(
                        self.flow, "last_find_line", len(text_objects) - 1
                    )

                text_objects, focus_pos = self.search_highlight_text(
                    text_objects,
                    search_string,
                    looping=True,
                    backwards=backwards
                )

        return text_objects, focus_pos

    def search_highlight_object(self, text_object, find_index, search_string):
        """
            just a little abstraction
        """
        before = text_object[:find_index]
        after = text_object[find_index+len(search_string):]

        new_text = urwid.Text(
            [
                before,
                (self.highlight_color, search_string),
                after,
            ]
        )

        return new_text

    def view_request(self):
        self.state.view_flow_mode = common.VIEW_FLOW_REQUEST
        body = self.conn_text(self.flow.request)
        self._w = self.wrap_body(common.VIEW_FLOW_REQUEST, body)

    def view_response(self):
        self.state.view_flow_mode = common.VIEW_FLOW_RESPONSE
        if self.flow.response:
            body = self.conn_text(self.flow.response)
        else:
            body = urwid.ListBox(
                        [
                            urwid.Text(""),
                            urwid.Text(
                                [
                                    ("highlight", "No response. Press "),
                                    ("key", "e"),
                                    ("highlight", " and edit any aspect to add one."),
                                ]
                            )
                        ]
                   )
        self._w = self.wrap_body(common.VIEW_FLOW_RESPONSE, body)

    def set_method_raw(self, m):
        if m:
            self.flow.request.method = m
            signals.flow_change.send(self, flow = self.flow)

    def edit_method(self, m):
        if m == "e":
            signals.status_prompt.send(
                prompt = "Method",
                text = self.flow.request.method,
                callback = self.set_method_raw
            )
        else:
            for i in common.METHOD_OPTIONS:
                if i[1] == m:
                    self.flow.request.method = i[0].upper()
            signals.flow_change.send(self, flow = self.flow)

    def set_url(self, url):
        request = self.flow.request
        try:
            request.url = str(url)
        except ValueError:
            return "Invalid URL."
        signals.flow_change.send(self, flow = self.flow)

    def set_resp_code(self, code):
        response = self.flow.response
        try:
            response.code = int(code)
        except ValueError:
            return None
        import BaseHTTPServer
        if BaseHTTPServer.BaseHTTPRequestHandler.responses.has_key(int(code)):
            response.msg = BaseHTTPServer.BaseHTTPRequestHandler.responses[int(code)][0]
        signals.flow_change.send(self, flow = self.flow)

    def set_resp_msg(self, msg):
        response = self.flow.response
        response.msg = msg
        signals.flow_change.send(self, flow = self.flow)

    def set_headers(self, lst, conn):
        conn.headers = flow.ODictCaseless(lst)
        signals.flow_change.send(self, flow = self.flow)

    def set_query(self, lst, conn):
        conn.set_query(flow.ODict(lst))
        signals.flow_change.send(self, flow = self.flow)

    def set_path_components(self, lst, conn):
        conn.set_path_components([i[0] for i in lst])
        signals.flow_change.send(self, flow = self.flow)

    def set_form(self, lst, conn):
        conn.set_form_urlencoded(flow.ODict(lst))
        signals.flow_change.send(self, flow = self.flow)

    def edit_form(self, conn):
        self.master.view_grideditor(
            grideditor.URLEncodedFormEditor(
                self.master,
                conn.get_form_urlencoded().lst,
                self.set_form,
                conn
            )
        )

    def edit_form_confirm(self, key, conn):
        if key == "y":
            self.edit_form(conn)

    def edit(self, part):
        if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            message = self.flow.request
        else:
            if not self.flow.response:
                self.flow.response = HTTPResponse(
                    self.flow.request.httpversion,
                    200, "OK", flow.ODictCaseless(), ""
                )
                self.flow.response.reply = controller.DummyReply()
            message = self.flow.response

        self.flow.backup()
        if part == "r":
            with decoded(message):
                # Fix an issue caused by some editors when editing a
                # request/response body. Many editors make it hard to save a
                # file without a terminating newline on the last line. When
                # editing message bodies, this can cause problems. For now, I
                # just strip the newlines off the end of the body when we return
                # from an editor.
                c = self.master.spawn_editor(message.content or "")
                message.content = c.rstrip("\n")
        elif part == "f":
            if not message.get_form_urlencoded() and message.content:
                signals.status_prompt_onekey.send(
                    prompt = "Existing body is not a URL-encoded form. Clear and edit?",
                    keys = [
                        ("yes", "y"),
                        ("no", "n"),
                    ],
                    callback = self.edit_form_confirm,
                    args = (message,)
                )
            else:
                self.edit_form(message)
        elif part == "h":
            self.master.view_grideditor(
                grideditor.HeaderEditor(
                    self.master,
                    message.headers.lst,
                    self.set_headers,
                    message
                )
            )
        elif part == "p":
            p = message.get_path_components()
            p = [[i] for i in p]
            self.master.view_grideditor(
                grideditor.PathEditor(
                    self.master,
                    p,
                    self.set_path_components,
                    message
                )
            )
        elif part == "q":
            self.master.view_grideditor(
                grideditor.QueryEditor(
                    self.master,
                    message.get_query().lst,
                    self.set_query, message
                )
            )
        elif part == "u" and self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            signals.status_prompt.send(
                prompt = "URL",
                text = message.url,
                callback = self.set_url
            )
        elif part == "m" and self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            signals.status_prompt_onekey.send(
                prompt = "Method",
                keys = common.METHOD_OPTIONS,
                callback = self.edit_method
            )
        elif part == "c" and self.state.view_flow_mode == common.VIEW_FLOW_RESPONSE:
            signals.status_prompt.send(
                prompt = "Code",
                text = str(message.code),
                callback = self.set_resp_code
            )
        elif part == "m" and self.state.view_flow_mode == common.VIEW_FLOW_RESPONSE:
            signals.status_prompt.send(
                prompt = "Message",
                text = message.msg,
                callback = self.set_resp_msg
            )
        signals.flow_change.send(self, flow = self.flow)

    def _view_nextprev_flow(self, np, flow):
        try:
            idx = self.state.view.index(flow)
        except IndexError:
            return
        if np == "next":
            new_flow, new_idx = self.state.get_next(idx)
        else:
            new_flow, new_idx = self.state.get_prev(idx)
        if new_flow is None:
            signals.status_message.send(message="No more flows!")
        else:
            signals.pop_view_state.send(self)
            self.master.view_flow(new_flow)

    def view_next_flow(self, flow):
        return self._view_nextprev_flow("next", flow)

    def view_prev_flow(self, flow):
        return self._view_nextprev_flow("prev", flow)

    def change_this_display_mode(self, t):
        self.state.add_flow_setting(
            self.flow,
            (self.state.view_flow_mode, "prettyview"),
            contentview.get_by_shortcut(t)
        )
        signals.flow_change.send(self, flow = self.flow)

    def delete_body(self, t):
        if t == "m":
            val = CONTENT_MISSING
        else:
            val = None
        if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            self.flow.request.content = val
        else:
            self.flow.response.content = val
        signals.flow_change.send(self, flow = self.flow)

    def keypress(self, size, key):
        if key == " ":
            self.view_next_flow(self.flow)
            return

        key = common.shortcuts(key)
        if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
            conn = self.flow.request
        else:
            conn = self.flow.response

        if key == "q":
            signals.pop_view_state.send(self)
            return None
        elif key == "tab":
            if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
                self.view_response()
            else:
                self.view_request()
        elif key in ("up", "down", "page up", "page down"):
            # Why doesn't this just work??
            self._w.keypress(size, key)
        elif key == "a":
            self.flow.accept_intercept(self.master)
            self.master.view_flow(self.flow)
        elif key == "A":
            self.master.accept_all()
            self.master.view_flow(self.flow)
        elif key == "b":
            if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
                common.ask_save_body("q", self.master, self.state, self.flow)
            else:
                common.ask_save_body("s", self.master, self.state, self.flow)
        elif key == "d":
            if self.state.flow_count() == 1:
                self.master.view_flowlist()
            elif self.state.view.index(self.flow) == len(self.state.view)-1:
                self.view_prev_flow(self.flow)
            else:
                self.view_next_flow(self.flow)
            f = self.flow
            f.kill(self.master)
            self.state.delete_flow(f)
        elif key == "D":
            f = self.master.duplicate_flow(self.flow)
            self.master.view_flow(f)
            signals.status_message.send(message="Duplicated.")
        elif key == "e":
            if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
                signals.status_prompt_onekey.send(
                    prompt = "Edit request",
                    keys = (
                        ("query", "q"),
                        ("path", "p"),
                        ("url", "u"),
                        ("header", "h"),
                        ("form", "f"),
                        ("raw body", "r"),
                        ("method", "m"),
                    ),
                    callback = self.edit
                )
            else:
                signals.status_prompt_onekey.send(
                    prompt = "Edit response",
                    keys = (
                        ("code", "c"),
                        ("message", "m"),
                        ("header", "h"),
                        ("raw body", "r"),
                    ),
                    callback = self.edit
                )
            key = None
        elif key == "f":
            signals.status_message.send(message="Loading all body data...")
            self.state.add_flow_setting(
                self.flow,
                (self.state.view_flow_mode, "fullcontents"),
                True
            )
            signals.flow_change.send(self, flow = self.flow)
            signals.status_message.send(message="")
        elif key == "g":
            if self.state.view_flow_mode == common.VIEW_FLOW_REQUEST:
                scope = "q"
            else:
                scope = "s"
            common.ask_copy_part(scope, self.flow, self.master, self.state)
        elif key == "m":
            p = list(contentview.view_prompts)
            p.insert(0, ("Clear", "C"))
            signals.status_prompt_onekey.send(
                self,
                prompt = "Display mode",
                keys = p,
                callback = self.change_this_display_mode
            )
            key = None
        elif key == "p":
            self.view_prev_flow(self.flow)
        elif key == "r":
            r = self.master.replay_request(self.flow)
            if r:
                signals.status_message.send(message=r)
            signals.flow_change.send(self, flow = self.flow)
        elif key == "V":
            if not self.flow.modified():
                signals.status_message.send(message="Flow not modified.")
                return
            self.state.revert(self.flow)
            signals.flow_change.send(self, flow = self.flow)
            signals.status_message.send(message="Reverted.")
        elif key == "W":
            signals.status_prompt_path.send(
                prompt = "Save this flow",
                callback = self.master.save_one_flow,
                args = (self.flow,)
            )
        elif key == "v":
            if conn and conn.content:
                t = conn.headers["content-type"] or [None]
                t = t[0]
                if os.environ.has_key("EDITOR") or os.environ.has_key("PAGER"):
                    self.master.spawn_external_viewer(conn.content, t)
                else:
                    signals.status_message.send(
                        message = "Error! Set $EDITOR or $PAGER."
                    )
        elif key == "|":
            signals.status_prompt_path.send(
                prompt = "Send flow to script",
                callback = self.master.run_script_once,
                args = (self.flow,)
            )
        elif key == "x":
            signals.status_prompt_onekey.send(
                prompt = "Delete body",
                keys = (
                    ("completely", "c"),
                    ("mark as missing", "m"),
                ),
                callback = self.delete_body
            )
            key = None
        elif key == "X":
            self.master.view_flowdetails(self.flow)
        elif key == "z":
            if conn:
                self.flow.backup()
                e = conn.headers.get_first("content-encoding", "identity")
                if e != "identity":
                    if not conn.decode():
                        signals.status_message.send(
                            message = "Could not decode - invalid data?"
                        )
                else:
                    signals.status_prompt_onekey.send(
                        prompt = "Select encoding: ",
                        keys = (
                            ("gzip", "z"),
                            ("deflate", "d"),
                        ),
                        callback = self.encode_callback,
                        args = (conn,)
                    )
                signals.flow_change.send(self, flow = self.flow)
        elif key == "/":
            last_search_string = self.state.get_flow_setting(
                self.flow,
                "last_search_string"
            )
            search_prompt = "Search body ["+last_search_string+"]" if last_search_string else "Search body"
            signals.status_prompt.send(
                prompt = search_prompt,
                text = "",
                callback = self.search
            )
        elif key == "n":
            self.search_again(backwards=False)
        elif key == "N":
            self.search_again(backwards=True)
        else:
            return key

    def encode_callback(self, key, conn):
        encoding_map = {
            "z": "gzip",
            "d": "deflate",
        }
        conn.encode(encoding_map[key])
        signals.flow_change.send(self, flow = self.flow)