use std::{
    collections::{HashMap, HashSet},
    iter,
    sync::Arc,
};

use ruma::{
    api::client::error::ErrorKind,
    events::{
        room::{create::PreviousRoom, member::MembershipState},
        AnyStrippedStateEvent, StateEventType, TimelineEventType,
    },
    room::RoomType,
    serde::Raw,
    state_res::{self, StateMap},
    EventId, OwnedEventId, OwnedRoomId, RoomId, RoomVersionId, UserId,
};
use serde::{de::DeserializeOwned, Deserialize};
use tracing::warn;

use super::{short::ShortStateHash, state_compressor::CompressedStateEvent};
use crate::{
    service::globals::marker,
    services,
    utils::{
        calculate_hash, debug_slice_truncated, on_demand_hashmap::KeyToken,
    },
    Error, PduEvent, Result,
};

mod data;

pub(crate) use data::Data;

pub(crate) trait ExtractCreateContent: DeserializeOwned {
    type Extract;

    fn extract(self) -> Self::Extract;
}

/// Extract the `room_version` from an `m.room.create` event
#[derive(Deserialize)]
pub(crate) struct ExtractVersion {
    room_version: RoomVersionId,
}

impl ExtractCreateContent for ExtractVersion {
    type Extract = RoomVersionId;

    fn extract(self) -> Self::Extract {
        self.room_version
    }
}

/// Extract the `type` from an `m.room.create` event
#[derive(Deserialize)]
pub(crate) struct ExtractType {
    #[serde(rename = "type")]
    kind: Option<RoomType>,
}

impl ExtractCreateContent for ExtractType {
    type Extract = Option<RoomType>;

    fn extract(self) -> Self::Extract {
        self.kind
    }
}

#[derive(Deserialize)]
pub(crate) struct ExtractPredecessor {
    predecessor: Option<PreviousRoom>,
}

impl ExtractCreateContent for ExtractPredecessor {
    type Extract = Option<PreviousRoom>;

    fn extract(self) -> Self::Extract {
        self.predecessor
    }
}

pub(crate) struct Service {
    pub(crate) db: &'static dyn Data,
}

impl Service {
    /// Set the room to the given statehash and update caches.
    #[tracing::instrument(skip(self, statediffnew, _statediffremoved))]
    pub(crate) async fn force_state(
        &self,
        room_id: &KeyToken<OwnedRoomId, marker::State>,
        shortstatehash: ShortStateHash,
        statediffnew: Arc<HashSet<CompressedStateEvent>>,
        _statediffremoved: Arc<HashSet<CompressedStateEvent>>,
    ) -> Result<()> {
        for event_id in statediffnew.iter().filter_map(|new| {
            services()
                .rooms
                .state_compressor
                .parse_compressed_state_event(new)
                .ok()
                .map(|(_, id)| id)
        }) {
            let Some(pdu) =
                services().rooms.timeline.get_pdu_json(&event_id)?
            else {
                continue;
            };

            let pdu: PduEvent = match serde_json::from_str(
                &serde_json::to_string(&pdu)
                    .expect("CanonicalJsonObj can be serialized to JSON"),
            ) {
                Ok(pdu) => pdu,
                Err(_) => continue,
            };

            match pdu.kind {
                TimelineEventType::RoomMember => {
                    #[derive(Deserialize)]
                    struct ExtractMembership {
                        membership: MembershipState,
                    }

                    let membership =
                        match serde_json::from_str::<ExtractMembership>(
                            pdu.content.get(),
                        ) {
                            Ok(e) => e.membership,
                            Err(_) => continue,
                        };

                    let Some(state_key) = pdu.state_key else {
                        continue;
                    };

                    let Ok(user_id) = UserId::parse(state_key) else {
                        continue;
                    };

                    services().rooms.state_cache.update_membership(
                        room_id,
                        &user_id,
                        membership,
                        &pdu.sender,
                        None,
                        false,
                    )?;
                }
                TimelineEventType::SpaceChild => {
                    services()
                        .rooms
                        .spaces
                        .invalidate_cache(&pdu.room_id)
                        .await;
                }
                _ => continue,
            }
        }

        services().rooms.state_cache.update_joined_count(room_id)?;

        self.db.set_room_state(room_id, shortstatehash)?;

        Ok(())
    }

    /// Generates a new StateHash and associates it with the incoming event.
    ///
    /// This adds all current state events (not including the incoming event)
    /// to `stateid_pduid` and adds the incoming event to `eventid_statehash`.
    #[tracing::instrument(skip(self, state_ids_compressed))]
    pub(crate) fn set_event_state(
        &self,
        event_id: &EventId,
        room_id: &RoomId,
        state_ids_compressed: Arc<HashSet<CompressedStateEvent>>,
    ) -> Result<ShortStateHash> {
        let shorteventid =
            services().rooms.short.get_or_create_shorteventid(event_id)?;

        let previous_shortstatehash =
            self.db.get_room_shortstatehash(room_id)?;

        let state_hash = calculate_hash(
            state_ids_compressed.iter().map(CompressedStateEvent::as_bytes),
        );

        let (shortstatehash, already_existed) =
            services().rooms.short.get_or_create_shortstatehash(&state_hash)?;

        if !already_existed {
            let states_parents = previous_shortstatehash.map_or_else(
                || Ok(Vec::new()),
                |p| {
                    services()
                        .rooms
                        .state_compressor
                        .load_shortstatehash_info(p)
                },
            )?;

            let (statediffnew, statediffremoved) =
                if let Some(parent_stateinfo) = states_parents.last() {
                    let statediffnew: HashSet<_> = state_ids_compressed
                        .difference(&parent_stateinfo.full_state)
                        .copied()
                        .collect();

                    let statediffremoved: HashSet<_> = parent_stateinfo
                        .full_state
                        .difference(&state_ids_compressed)
                        .copied()
                        .collect();

                    (Arc::new(statediffnew), Arc::new(statediffremoved))
                } else {
                    (state_ids_compressed, Arc::new(HashSet::new()))
                };
            services().rooms.state_compressor.save_state_from_diff(
                shortstatehash,
                statediffnew,
                statediffremoved,
                // high number because no state will be based on this one
                1_000_000,
                states_parents,
            )?;
        }

        self.db.set_event_state(shorteventid, shortstatehash)?;

        Ok(shortstatehash)
    }

    /// Generates a new StateHash and associates it with the incoming event.
    ///
    /// This adds all current state events (not including the incoming event)
    /// to `stateid_pduid` and adds the incoming event to `eventid_statehash`.
    #[tracing::instrument(skip(self, new_pdu))]
    pub(crate) fn append_to_state(
        &self,
        new_pdu: &PduEvent,
    ) -> Result<ShortStateHash> {
        let shorteventid = services()
            .rooms
            .short
            .get_or_create_shorteventid(&new_pdu.event_id)?;

        let previous_shortstatehash =
            self.get_room_shortstatehash(&new_pdu.room_id)?;

        if let Some(p) = previous_shortstatehash {
            self.db.set_event_state(shorteventid, p)?;
        }

        if let Some(state_key) = &new_pdu.state_key {
            let states_parents = previous_shortstatehash.map_or_else(
                || Ok(Vec::new()),
                |p| {
                    services()
                        .rooms
                        .state_compressor
                        .load_shortstatehash_info(p)
                },
            )?;

            let shortstatekey =
                services().rooms.short.get_or_create_shortstatekey(
                    &new_pdu.kind.to_string().into(),
                    state_key,
                )?;

            let new = services()
                .rooms
                .state_compressor
                .compress_state_event(shortstatekey, &new_pdu.event_id)?;

            let replaces = states_parents
                .last()
                .map(|info| {
                    info.full_state
                        .iter()
                        .find(|compressed| compressed.state == shortstatekey)
                })
                .unwrap_or_default();

            if Some(&new) == replaces {
                return Ok(previous_shortstatehash.expect("must exist"));
            }

            // TODO: statehash with deterministic inputs
            let shortstatehash =
                ShortStateHash::new(services().globals.next_count()?);

            let mut statediffnew = HashSet::new();
            statediffnew.insert(new);

            let mut statediffremoved = HashSet::new();
            if let Some(replaces) = replaces {
                statediffremoved.insert(*replaces);
            }

            services().rooms.state_compressor.save_state_from_diff(
                shortstatehash,
                Arc::new(statediffnew),
                Arc::new(statediffremoved),
                2,
                states_parents,
            )?;

            Ok(shortstatehash)
        } else {
            Ok(previous_shortstatehash
                .expect("first event in room must be a state event"))
        }
    }

    /// Gather events to help the invited user identify the room
    ///
    /// Also includes the invite event itself.
    #[tracing::instrument(skip(self, invite_event))]
    pub(crate) fn get_helpful_invite_events(
        &self,
        invite_event: &PduEvent,
    ) -> Result<Vec<Raw<AnyStrippedStateEvent>>> {
        let helpful_events = [
            (StateEventType::RoomCreate, ""),
            (StateEventType::RoomJoinRules, ""),
            (StateEventType::RoomCanonicalAlias, ""),
            (StateEventType::RoomAvatar, ""),
            (StateEventType::RoomName, ""),
            (StateEventType::RoomMember, invite_event.sender.as_str()),
        ];

        let helpful_events =
            helpful_events.into_iter().filter_map(|(state_type, state_key)| {
                let state = services().rooms.state_accessor.room_state_get(
                    &invite_event.room_id,
                    &state_type,
                    state_key,
                );

                match state {
                    Ok(Some(x)) => Some(Ok(x.to_stripped_state_event())),
                    Err(x) => Some(Err(x)),
                    Ok(None) => None,
                }
            });

        let actual_event =
            iter::once(Ok(invite_event.to_stripped_state_event()));

        helpful_events.chain(actual_event).collect()
    }

    /// Set the state hash to a new version, but does not update state_cache.
    #[tracing::instrument(skip(self))]
    pub(crate) fn set_room_state(
        &self,
        room_id: &KeyToken<OwnedRoomId, marker::State>,
        shortstatehash: ShortStateHash,
    ) -> Result<()> {
        self.db.set_room_state(room_id, shortstatehash)
    }

    /// Returns the value of a field of an `m.room.create` event's `content`.
    #[tracing::instrument(skip(self))]
    pub(crate) fn get_create_content<T: ExtractCreateContent>(
        &self,
        room_id: &RoomId,
    ) -> Result<T::Extract> {
        let create_event = services().rooms.state_accessor.room_state_get(
            room_id,
            &StateEventType::RoomCreate,
            "",
        )?;

        let content_field = create_event
            .as_ref()
            .map(|create_event| {
                serde_json::from_str::<T>(create_event.content.get()).map_err(
                    |error| {
                        warn!(%error, "Invalid create event");
                        Error::BadDatabase("Invalid create event in db.")
                    },
                )
            })
            .transpose()?
            .ok_or_else(|| {
                Error::BadRequest(
                    ErrorKind::InvalidParam,
                    "No create event found",
                )
            })?;

        Ok(content_field.extract())
    }

    #[tracing::instrument(skip(self))]
    pub(crate) fn get_room_shortstatehash(
        &self,
        room_id: &RoomId,
    ) -> Result<Option<ShortStateHash>> {
        self.db.get_room_shortstatehash(room_id)
    }

    #[tracing::instrument(skip(self))]
    pub(crate) fn get_forward_extremities(
        &self,
        room_id: &RoomId,
    ) -> Result<HashSet<Arc<EventId>>> {
        self.db.get_forward_extremities(room_id)
    }

    #[tracing::instrument(
        skip(self, event_ids),
        fields(event_ids = debug_slice_truncated(&event_ids, 5)),
    )]
    pub(crate) fn set_forward_extremities(
        &self,
        room_id: &KeyToken<OwnedRoomId, marker::State>,
        event_ids: Vec<OwnedEventId>,
    ) -> Result<()> {
        self.db.set_forward_extremities(room_id, event_ids)
    }

    /// This fetches auth events from the current state.
    #[tracing::instrument(skip(self))]
    pub(crate) fn get_auth_events(
        &self,
        room_id: &RoomId,
        kind: &TimelineEventType,
        sender: &UserId,
        state_key: Option<&str>,
        content: &serde_json::value::RawValue,
    ) -> Result<StateMap<Arc<PduEvent>>> {
        let Some(shortstatehash) = self.get_room_shortstatehash(room_id)?
        else {
            return Ok(HashMap::new());
        };

        let auth_events =
            state_res::auth_types_for_event(kind, sender, state_key, content)
                .expect("content is a valid JSON object");

        let mut sauthevents = auth_events
            .into_iter()
            .filter_map(|(event_type, state_key)| {
                services()
                    .rooms
                    .short
                    .get_shortstatekey(
                        &event_type.to_string().into(),
                        &state_key,
                    )
                    .ok()
                    .flatten()
                    .map(|s| (s, (event_type, state_key)))
            })
            .collect::<HashMap<_, _>>();

        let full_state = services()
            .rooms
            .state_compressor
            .load_shortstatehash_info(shortstatehash)?
            .pop()
            .expect("there is always one layer")
            .full_state;

        Ok(full_state
            .iter()
            .filter_map(|compressed| {
                services()
                    .rooms
                    .state_compressor
                    .parse_compressed_state_event(compressed)
                    .ok()
            })
            .filter_map(|(shortstatekey, event_id)| {
                sauthevents.remove(&shortstatekey).map(|k| (k, event_id))
            })
            .filter_map(|(k, event_id)| {
                services()
                    .rooms
                    .timeline
                    .get_pdu(&event_id)
                    .ok()
                    .flatten()
                    .map(|pdu| (k, pdu))
            })
            .collect())
    }
}