# SPDX-License-Identifier: GPL-3.0-or-later

# Haketilo addon for Mitmproxy.
#
# This file is part of Hydrilla&Haketilo.
#
# Copyright (C) 2022 Wojtek Kosior
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
#
#
# I, Wojtek Kosior, thereby promise not to sue for violation of this
# file's license. Although I request that you do not make use of this
# code in a proprietary program, I am not going to enforce this in
# court.

"""
This module contains the definition of a mitmproxy addon that gets instantiated
from addon script.
"""

import sys
import re
import threading
import secrets
import typing as t
import dataclasses as dc
import traceback as tb

from pathlib import Path
from contextlib import contextmanager
from urllib.parse import urlparse

from mitmproxy import tls, http, addonmanager, ctx
from mitmproxy.script import concurrent

from ..exceptions import HaketiloException
from ..translations import smart_gettext as _
from .. import url_patterns
from .state_impl import ConcreteHaketiloState
from . import state
from . import policies
from . import http_messages


class LoggerToMitmproxy(state.Logger):
    def warn(self, msg: str) -> None:
        ctx.log.warn(f'Haketilo: {msg}')


def safe_parse_url(url: str) -> url_patterns.ParsedUrl:
    try:
        return url_patterns.parse_url(url)
    except url_patterns.HaketiloURLException:
        return url_patterns.dummy_url


@dc.dataclass
class FlowHandling:
    flow:              http.HTTPFlow
    policy:            policies.Policy
    _bl_request_info:  http_messages.BodylessRequestInfo
    _request_info:     t.Optional[http_messages.RequestInfo]          = None
    _bl_response_info: t.Optional[http_messages.BodylessResponseInfo] = None

    @property
    def bl_request_info(self) -> http_messages.BodylessRequestInfo:
        return self._bl_request_info

    @property
    def request_info(self) -> http_messages.RequestInfo:
        if self._request_info is None:
            body = self.flow.request.get_content(strict=False) or b''
            self._request_info = self._bl_request_info.with_body(body)

        return self._request_info

    @property
    def bl_response_info(self) -> http_messages.BodylessResponseInfo:
        if self._bl_response_info is None:
            assert self.flow.response is not None

            self._bl_response_info = http_messages.BodylessResponseInfo.make(
                url         = safe_parse_url(self.flow.request.url),
                status_code = self.flow.response.status_code,
                headers     = self.flow.response.headers
            )

        return self._bl_response_info

    @property
    def response_info(self) -> http_messages.ResponseInfo:
        assert self.flow.response is not None

        body = self.flow.response.get_content(strict=False) or b''
        return self.bl_response_info.with_body(body)

    @property
    def full_http_info(self) -> http_messages.FullHTTPInfo:
        return http_messages.FullHTTPInfo(self.request_info, self.response_info)

    @staticmethod
    def make(
            flow:   http.HTTPFlow,
            policy: policies.Policy,
            url:    url_patterns.ParsedUrl
    ) -> 'FlowHandling':
        bl_request_info = http_messages.BodylessRequestInfo.make(
            url     = url,
            method  = flow.request.method,
            headers = flow.request.headers
        )

        return FlowHandling(flow, policy, bl_request_info)


@dc.dataclass
class PassedOptions:
    haketilo_dir:            t.Optional[str]  = None
    haketilo_listen_host:    t.Optional[str]  = None
    haketilo_listen_port:    t.Optional[int]  = None
    haketilo_launch_browser: t.Optional[bool] = None

    @property
    def fully_configured(self) -> bool:
        return (self.haketilo_dir            is not None and
                self.haketilo_listen_host    is not None and
                self.haketilo_listen_port    is not None and
                self.haketilo_launch_browser is not None)


Lock = threading.Lock

@dc.dataclass
class HaketiloAddon:
    initial_options: PassedOptions = PassedOptions()
    configured:      bool          = False
    configured_lock: Lock          = dc.field(default_factory=Lock)

    handling_dict:      dict[int, FlowHandling] = dc.field(default_factory=dict)
    handling_dict_lock: Lock                    = dc.field(default_factory=Lock)

    logger: LoggerToMitmproxy = dc.field(default_factory=LoggerToMitmproxy)

    state: t.Optional[ConcreteHaketiloState] = None

    def load(self, loader: addonmanager.Loader) -> None:
        """...."""
        loader.add_option(
            name     = 'haketilo_dir',
            typespec = str,
            default  = '~/.haketilo/',
            help     = "Point to a Haketilo data directory to use"
        )
        loader.add_option(
            name     = 'haketilo_listen_host',
            typespec = str,
            default  = '127.0.0.1',
            help     = "Specify the address proxy listens on"
        )
        loader.add_option(
            name     = 'haketilo_listen_port',
            typespec = int,
            default  = 8080,
            help     = "Specify the port listens on"
        )
        loader.add_option(
            name     = 'haketilo_launch_browser',
            typespec = bool,
            default  = True,
            help     = "Specify whether to attempt to open a browser window with Haketilo page displayed inside"
        )

    def configure(self, updated: set[str]) -> None:
        with self.configured_lock:
            val_names = ('dir', 'listen_host', 'listen_port', 'launch_browser')
            for val_name in val_names:
                key = f'haketilo_{val_name}'

                if key not in updated:
                    continue

                if getattr(self.initial_options, key) is not None:
                    fmt = _('warn.proxy.setting_already_configured_{}')
                    self.logger.warn(fmt.format(key))
                    continue

                new_val = getattr(ctx.options, key)
                setattr(self.initial_options, key, new_val)

            if self.configured or not self.initial_options.fully_configured:
                return

            try:
                haketilo_dir = self.initial_options.haketilo_dir
                listen_host  = self.initial_options.haketilo_listen_host
                listen_port  = self.initial_options.haketilo_listen_port

                self.state = ConcreteHaketiloState.make(
                    store_dir   = Path(t.cast(str, haketilo_dir)) / 'store',
                    listen_host = t.cast(str, listen_host),
                    listen_port = t.cast(int, listen_port),
                    logger      = self.logger
                )
            except Exception as e:
                tb.print_exception(None, e, e.__traceback__)
                sys.exit(1)

            self.configured = True

    def running(self) -> None:
        with self.configured_lock:
            assert self.configured

        assert self.state is not None

        if self.initial_options.haketilo_launch_browser:
            if not self.state.launch_browser():
                self.logger.warn(_('warn.proxy.couldnt_launch_browser'))

    def get_flow_handling(self, flow: http.HTTPFlow) -> FlowHandling:
        policy: policies.Policy

        assert self.state is not None

        with self.handling_dict_lock:
            handling = self.handling_dict.get(id(flow))

        if handling is None:
            try:
                parsed_url = url_patterns.parse_url(flow.request.url)
            except url_patterns.HaketiloURLException as e:
                haketilo_settings = self.state.get_settings()
                policy = policies.ErrorBlockPolicy(haketilo_settings, error=e)
                parsed_url = url_patterns.dummy_url
            else:
                policy = self.state.select_policy(parsed_url)

            handling = FlowHandling.make(flow, policy, parsed_url)

            with self.handling_dict_lock:
                self.handling_dict[id(flow)] = handling

        return handling

    def forget_flow_handling(self, flow: http.HTTPFlow) -> None:
        with self.handling_dict_lock:
            self.handling_dict.pop(id(flow), None)

    @contextmanager
    def http_safe_event_handling(self, flow: http.HTTPFlow) -> t.Iterator:
        """...."""
        with self.configured_lock:
            assert self.configured

        try:
            yield
        except Exception as e:
            tb_string = ''.join(tb.format_exception(None, e, e.__traceback__))
            error_text = _('err.proxy.unknown_error_{}_try_again')\
                .format(tb_string)\
                .encode()
            flow.response = http.Response.make(
                status_code = 500,
                content     = error_text,
                headers     = [(b'Content-Type', b'text/plain; charset=utf-8')]
            )

            self.forget_flow_handling(flow)

    @concurrent
    def requestheaders(self, flow: http.HTTPFlow) -> None:
        with self.http_safe_event_handling(flow):
            referrer = flow.request.headers.get('referer')
            if referrer is not None:
                if urlparse(referrer).netloc == 'hkt.mitm.it' and \
                   urlparse(flow.request.url).netloc != 'hkt.mitm.it':
                    # Do not reveal to the site that Haketilo meta-site was
                    # visited before.
                    flow.request.headers.pop('referer', None)

            handling = self.get_flow_handling(flow)
            policy = handling.policy

            if not policy.should_process_request(handling.bl_request_info):
                flow.request.stream = True
            if policy.anticache:
                flow.request.anticache()

    @concurrent
    def request(self, flow: http.HTTPFlow) -> None:
        if flow.request.stream:
            return

        with self.http_safe_event_handling(flow):
            handling = self.get_flow_handling(flow)

            result = handling.policy.consume_request(handling.request_info)

            if result is not None:
                mitmproxy_headers = http.Headers(result.headers.items_bin())

                if isinstance(result, http_messages.RequestInfo):
                    flow.request.url     = result.url.orig_url
                    flow.request.method  = result.method
                    flow.request.headers = mitmproxy_headers
                    flow.request.set_content(result.body or None)
                else:
                    # isinstance(result, http_messages.ResponseInfo)
                    flow.response = http.Response.make(
                        status_code = result.status_code,
                        headers     = mitmproxy_headers,
                        content     = result.body
                    )

    def responseheaders(self, flow: http.HTTPFlow) -> None:
        assert flow.response is not None

        with self.http_safe_event_handling(flow):
            handling = self.get_flow_handling(flow)

            if not handling.policy.should_process_response(
                    request_info  = handling.request_info,
                    response_info = handling.bl_response_info
            ):
                flow.response.stream = True

    @concurrent
    def response(self, flow: http.HTTPFlow) -> None:
        assert flow.response is not None

        if flow.response.stream:
            return

        with self.http_safe_event_handling(flow):
            handling = self.get_flow_handling(flow)

            new_nonce = secrets.token_urlsafe(8)
            setattr(policies.response_work_data, 'nonce', new_nonce)

            try:
                http_info = handling.full_http_info
                result = handling.policy.consume_response(http_info)
            finally:
                delattr(policies.response_work_data, 'nonce')

            if result is not None:
                headers_bin = result.headers.items_bin()

                flow.response.status_code = result.status_code
                flow.response.headers     = http.Headers(headers_bin)
                flow.response.set_content(result.body)

            self.forget_flow_handling(flow)

    def tls_clienthello(self, data: tls.ClientHelloData):
        if data.context.server.address is None:
            return

        host, port = data.context.server.address
        if (host == 'hkt.mitm.it' or host.endswith('.hkt.mitm.it')) and \
           port == 443:
            return

        data.establish_server_tls_first = True

    def error(self, flow: http.HTTPFlow) -> None:
        self.forget_flow_handling(flow)