#! /usr/bin/env python
import argparse
import logging
import sys
from pprint import pformat
from typing import Awaitable, Callable, Collection, Optional, Tuple, cast
from unittest.mock import MagicMock, patch

import dictdiffer
import pydot
import yaml

from twisted.internet import task

from synapse.config._base import RootConfig
from synapse.config.cache import CacheConfig
from synapse.config.database import DatabaseConfig
from synapse.config.workers import WorkerConfig
from synapse.events import EventBase
from synapse.server import HomeServer
from synapse.state import StateResolutionStore
from synapse.storage.databases.main.event_federation import EventFederationWorkerStore
from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.databases.main.room import RoomWorkerStore
from synapse.storage.databases.main.state import StateGroupWorkerStore
from synapse.storage.state import StateFilter
from synapse.types import ISynapseReactor

"""This monstrosity is useful for visualising and debugging state resolution problems.


"""

logger = logging.getLogger(sys.argv[0])


# Bits of the HomeServer Machinery we need to talk to the DB.
class Config(RootConfig):
    config_classes = [DatabaseConfig, WorkerConfig, CacheConfig]


def load_config(source: str) -> Config:
    data = yaml.safe_load(source)
    data["worker_name"] = "stateres-debug"

    config = Config()
    config.parse_config_dict(data, "DUMMYPATH", "DUMMYPATH")
    config.key = MagicMock()  # Don't bother creating signing keys
    return config


class DataStore(
    StateGroupWorkerStore,
    EventFederationWorkerStore,
    EventsWorkerStore,
    RoomWorkerStore,
):
    pass


class MockHomeserver(HomeServer):
    DATASTORE_CLASS = DataStore  # type: ignore [assignment]

    def __init__(self, config: Config):
        super(MockHomeserver, self).__init__(
            hostname="stateres-debug",
            config=config,  # type: ignore[arg-type]
        )


# Functions for drawing graphviz diagrams via `pydot`.
def node(
    event: EventBase, suffix: Optional[str] = None, **kwargs: object
) -> pydot.Node:
    label = f"{event.event_id}\n{event.type}"
    if suffix:
        label += f"\n{suffix}"
    kwargs.setdefault("label", label)
    type_to_shape = {"m.room.member": "oval"}
    if event.type in type_to_shape:
        kwargs.setdefault("shape", type_to_shape[event.type])

    q = pydot.quote_if_necessary
    return pydot.Node(q(event.event_id), **kwargs)


def edge(source: EventBase, target: EventBase, **kwargs: object) -> pydot.Edge:
    return pydot.Edge(
        pydot.quote_if_necessary(source.event_id),
        pydot.quote_if_necessary(target.event_id),
        **kwargs,
    )


async def dump_mainlines(
    hs: MockHomeserver,
    starting_event: EventBase,
    watch_func: Optional[Callable[[EventBase], Awaitable[str]]] = None,
    extras: Collection[EventBase] = (),
) -> None:
    """Visualise the auth DAG above a given `starting_event`.

    Starting with the given event's parents and any `extras` of interest, we search in
    their auth events for power levels, join rules and sender membership events.
    We recursively repeat this process for any events found during the search
    until we have no more auth-ancestors of interest to find.

    In this way we build up a subset of the auth chain of the `starting_event`.
    (In particular we omit edges to m.room.create: they are everywhere and convey no
    information.)

    An optional `watch_func` allows us to annotate the events we see with a string of
    our choice. This can be useful if we want to track a single piece of state through
    the auth DAG.
    """
    graph = pydot.Dot(rankdir="BT")
    graph.set_node_defaults(shape="box", style="filled")

    async def new_node(event: EventBase, **kwargs: object) -> pydot.Node:
        suffix = await watch_func(event) if watch_func else None
        return node(event, suffix, **kwargs)

    graph.add_node(await new_node(starting_event, fillcolor="#6699cc"))
    seen = {starting_event.event_id}

    todo = []
    for extra in extras:
        graph.add_node(await new_node(extra, fillcolor="#cc9966"))
        seen.add(extra.event_id)
        todo.append(extra)

    for pid in starting_event.prev_event_ids():
        parent = await hs.get_datastores().main.get_event(pid)
        graph.add_node(await new_node(parent, fillcolor="#6699cc"))
        seen.add(pid)
        graph.add_edge(edge(starting_event, parent, style="dashed"))
        todo.append(parent)

    while todo:
        event = todo.pop()
        auth_events = {
            (e.type, e.state_key): e
            for e in (
                await hs.get_datastores().main.get_events(event.auth_event_ids())
            ).values()
        }

        for key, style in [
            (("m.room.power_levels", ""), "dashed"),
            (("m.room.join_rules", ""), "dashed"),
            (("m.room.member", event.sender), "dotted"),
        ]:
            auth_event = auth_events.get(key)
            if auth_event:
                if auth_event.event_id not in seen:
                    if key[0] == "m.room.power_levels":
                        graph.add_node(await new_node(auth_event, fillcolor="#ffcccc"))
                    else:
                        graph.add_node(await new_node(auth_event))
                    seen.add(auth_event.event_id)
                    todo.append(auth_event)
                graph.add_edge(edge(event, auth_event, style=style))

    # TODO: make this location configurable
    graph.write_svg("mainlines.svg")


# The main logic and the arguments we need to invoke it.
parser = argparse.ArgumentParser(
    description="Debug the stateres calculation of a specific event."
)
parser.add_argument(
    "config_file", help="Synapse config file", type=argparse.FileType("r")
)
parser.add_argument("--verbose", "-v", help="Log verbosely", action="store_true")
parser.add_argument(
    "--debug", "-d", help="Enter debugger after state is resolved", action="store_true"
)
parser.add_argument("event_id", help="The event ID to be resolved")
parser.add_argument(
    "--watch",
    help="Track a piece of state in the auth DAG",
    default=None,
    nargs=2,
    metavar=("TYPE", "STATE_KEY"),
)


async def debug_specific_stateres(
    reactor: ISynapseReactor, hs: MockHomeserver, args: argparse.Namespace
) -> None:
    """Recompute the state at the given event.

    This produces
    - a file called `mainline.svg` representing the auth chain of the given event,
    - logging from state resolution calculations, written to stdout,
    - the recomputed and stored state, written to stdout, and
    - their difference, written to stdout.
    """
    # Fetch the event in question.
    event = await hs.get_datastores().main.get_event(args.event_id)
    assert event is not None
    logger.info(
        "event %s has %d parents, %s",
        event.event_id,
        len(event.prev_event_ids()),
        event.prev_event_ids(),
    )

    state_after_parents = [
        await hs.get_storage_controllers().state.get_state_ids_for_event(prev_event_id)
        for prev_event_id in event.prev_event_ids()
    ]

    if args.watch is not None:
        key_pair = cast(Tuple[str, str], tuple(args.watch))
        filter = StateFilter.from_types([key_pair])

        watch_func: Optional[Callable[[EventBase], Awaitable[str]]]

        async def watch_func(event: EventBase) -> str:
            result = await hs.get_storage_controllers().state.get_state_ids_for_event(
                event.event_id, filter
            )
            return f"{key_pair}: {result.get(key_pair, '<Missing>')}"

    else:
        watch_func = None

    await dump_mainlines(hs, event, watch_func)

    result = await hs.get_state_resolution_handler().resolve_events_with_store(
        event.room_id,
        event.room_version.identifier,
        state_after_parents,
        event_map=None,
        state_res_store=StateResolutionStore(hs.get_datastores().main),
    )

    logger.info("State resolved at %s:", event.event_id)
    logger.info(pformat(result))

    logger.info("Stored state at %s:", event.event_id)
    stored_state = await hs.get_storage_controllers().state.get_state_ids_for_event(
        event.event_id
    )
    logger.info(pformat(stored_state))

    # TODO make this a like-for-like comparison.
    logger.info("Diff from stored (after event) to resolved (before event):")
    for change in dictdiffer.diff(stored_state, result):
        logger.info(pformat(change))

    if args.debug:
        print(
            f"see `state_after_parents[i]` for 0 <= i < {len(state_after_parents)}"
            " and `result`",
            file=sys.stderr,
        )
        breakpoint()


# Entrypoint.
if __name__ == "__main__":
    args = parser.parse_args()
    logging.basicConfig(
        format="%(asctime)s %(name)s:%(lineno)d %(levelname)s %(message)s",
        level=logging.DEBUG if args.verbose else logging.INFO,
        stream=sys.stdout,
    )
    # Suppress logs weren't not interested in.
    logging.getLogger("synapse.util").setLevel(logging.ERROR)
    logging.getLogger("synapse.storage").setLevel(logging.ERROR)

    config = load_config(args.config_file)
    hs = MockHomeserver(config)
    # Patch out enough stuff so we can work with a readonly DB connection.
    with patch("synapse.storage.databases.prepare_database"), patch(
        "synapse.storage.database.BackgroundUpdater"
    ), patch("synapse.storage.databases.main.events_worker.MultiWriterIdGenerator"):
        hs.setup()

    task.react(debug_specific_stateres, [hs, parser.parse_args()])