// Copyright 2025 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use matrix_sdk::{Client, Room, latest_events::LocalLatestEventValue};
use matrix_sdk_base::latest_event::LatestEventValue as BaseLatestEventValue;
use ruma::{
    MilliSecondsSinceUnixEpoch, OwnedUserId,
    events::{
        AnyMessageLikeEventContent, relation::Replacement, room::message::RoomMessageEventContent,
    },
};
use tracing::trace;

use crate::timeline::{
    Profile, TimelineDetails, TimelineItemContent,
    event_handler::{HandleAggregationKind, TimelineAction},
    traits::RoomDataProvider,
};

/// A simplified version of [`matrix_sdk_base::latest_event::LatestEventValue`]
/// tailored for this `timeline` module.
#[derive(Debug)]
pub enum LatestEventValue {
    /// No value has been computed yet, or no candidate value was found.
    None,

    /// The latest event represents a remote event.
    Remote {
        /// The timestamp of the remote event.
        timestamp: MilliSecondsSinceUnixEpoch,

        /// The sender of the remote event.
        sender: OwnedUserId,

        /// Has this event been sent by the current logged user?
        is_own: bool,

        /// The sender's profile.
        profile: TimelineDetails<Profile>,

        /// The content of the remote event.
        content: TimelineItemContent,
    },

    /// The latest event represents a local event that is sending, or that
    /// cannot be sent, either because a previous local event, or this local
    /// event cannot be sent.
    Local {
        /// The timestamp of the local event.
        timestamp: MilliSecondsSinceUnixEpoch,

        /// The sender of the remote event.
        sender: OwnedUserId,

        /// The sender's profile.
        profile: TimelineDetails<Profile>,

        /// The content of the local event.
        content: TimelineItemContent,

        /// Whether the local event is sending if it is set to `true`, otherwise
        /// it cannot be sent.
        is_sending: bool,
    },
}

impl LatestEventValue {
    pub(crate) async fn from_base_latest_event_value(
        value: BaseLatestEventValue,
        room: &Room,
        client: &Client,
    ) -> Self {
        match value {
            BaseLatestEventValue::None => Self::None,
            BaseLatestEventValue::Remote(timeline_event) => {
                let raw_any_sync_timeline_event = timeline_event.into_raw();
                let Ok(any_sync_timeline_event) = raw_any_sync_timeline_event.deserialize() else {
                    return Self::None;
                };

                let timestamp = any_sync_timeline_event.origin_server_ts();
                let sender = any_sync_timeline_event.sender().to_owned();
                let is_own = client.user_id().map(|user_id| user_id == sender).unwrap_or(false);
                let profile = room
                    .profile_from_user_id(&sender)
                    .await
                    .map(TimelineDetails::Ready)
                    .unwrap_or(TimelineDetails::Unavailable);

                match TimelineAction::from_event(
                    any_sync_timeline_event,
                    &raw_any_sync_timeline_event,
                    room,
                    None,
                    None,
                    None,
                    None,
                )
                .await
                {
                    // Easy path: no aggregation, direct event.
                    Some(TimelineAction::AddItem { content }) => {
                        Self::Remote { timestamp, sender, is_own, profile, content }
                    }

                    // Aggregated event.
                    //
                    // Only edits are supported for the moment.
                    Some(TimelineAction::HandleAggregation {
                        kind:
                            HandleAggregationKind::Edit { replacement: Replacement { new_content, .. } },
                        ..
                    }) => {
                        // Let's map the edit into a regular message.
                        match TimelineAction::from_content(
                            AnyMessageLikeEventContent::RoomMessage(RoomMessageEventContent::new(
                                new_content.msgtype,
                            )),
                            // We don't care about the `InReplyToDetails` in the context of a
                            // `LatestEventValue`.
                            None,
                            // We don't care about the thread information in the context of a
                            // `LatestEventValue`.
                            None,
                            None,
                        ) {
                            // The expected case.
                            TimelineAction::AddItem { content } => {
                                Self::Remote { timestamp, sender, is_own, profile, content }
                            }

                            // Supposedly unreachable, but let's pretend there is no
                            // `LatestEventValue` if it happens.
                            _ => {
                                trace!("latest event was an edit that failed to be un-aggregated");

                                Self::None
                            }
                        }
                    }

                    _ => Self::None,
                }
            }
            BaseLatestEventValue::LocalIsSending(LocalLatestEventValue {
                timestamp,
                content: ref serialized_content,
            })
            | BaseLatestEventValue::LocalCannotBeSent(LocalLatestEventValue {
                timestamp,
                content: ref serialized_content,
            }) => {
                let Ok(message_like_event_content) = serialized_content.deserialize() else {
                    return Self::None;
                };

                let sender =
                    client.user_id().expect("The `Client` is supposed to be logged").to_owned();
                let profile = room
                    .profile_from_user_id(&sender)
                    .await
                    .map(TimelineDetails::Ready)
                    .unwrap_or(TimelineDetails::Unavailable);
                let is_sending = matches!(value, BaseLatestEventValue::LocalIsSending(_));

                match TimelineAction::from_content(message_like_event_content, None, None, None) {
                    TimelineAction::AddItem { content } => {
                        Self::Local { timestamp, sender, profile, content, is_sending }
                    }

                    TimelineAction::HandleAggregation { kind, .. } => {
                        // Add some debug logging here to help diagnose issues with the latest
                        // event.
                        trace!("latest event is an aggregation: {}", kind.debug_string());
                        Self::None
                    }
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use std::ops::Not;

    use assert_matches::assert_matches;
    use matrix_sdk::{
        latest_events::{LocalLatestEventValue, RemoteLatestEventValue},
        store::SerializableEventContent,
        test_utils::mocks::MatrixMockServer,
    };
    use matrix_sdk_test::{JoinedRoomBuilder, async_test, event_factory::EventFactory};
    use ruma::{
        MilliSecondsSinceUnixEpoch, event_id,
        events::{AnyMessageLikeEventContent, room::message::RoomMessageEventContent},
        room_id, uint, user_id,
    };

    use super::{
        super::{MsgLikeContent, MsgLikeKind, TimelineItemContent},
        BaseLatestEventValue, LatestEventValue, TimelineDetails,
    };

    #[async_test]
    async fn test_none() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let room = server.sync_room(&client, JoinedRoomBuilder::new(room_id!("!r0"))).await;

        let base_value = BaseLatestEventValue::None;
        let value =
            LatestEventValue::from_base_latest_event_value(base_value, &room, &client).await;

        assert_matches!(value, LatestEventValue::None);
    }

    #[async_test]
    async fn test_remote() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let room = server.sync_room(&client, JoinedRoomBuilder::new(room_id!("!r0"))).await;
        let sender = user_id!("@mnt_io:matrix.org");
        let event_factory = EventFactory::new();

        let base_value = BaseLatestEventValue::Remote(RemoteLatestEventValue::from_plaintext(
            event_factory
                .server_ts(42)
                .sender(sender)
                .text_msg("raclette")
                .event_id(event_id!("$ev0"))
                .into_raw_sync(),
        ));
        let value =
            LatestEventValue::from_base_latest_event_value(base_value, &room, &client).await;

        assert_matches!(value, LatestEventValue::Remote { timestamp, sender: received_sender, is_own, profile, content } => {
            assert_eq!(u64::from(timestamp.get()), 42u64);
            assert_eq!(received_sender, sender);
            assert!(is_own.not());
            assert_matches!(profile, TimelineDetails::Unavailable);
            assert_matches!(
                content,
                TimelineItemContent::MsgLike(MsgLikeContent { kind: MsgLikeKind::Message(message), .. }) => {
                    assert_eq!(message.body(), "raclette");
                }
            );
        })
    }

    #[async_test]
    async fn test_local_is_sending() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let room = server.sync_room(&client, JoinedRoomBuilder::new(room_id!("!r0"))).await;

        let base_value = BaseLatestEventValue::LocalIsSending(LocalLatestEventValue {
            timestamp: MilliSecondsSinceUnixEpoch(uint!(42)),
            content: SerializableEventContent::new(&AnyMessageLikeEventContent::RoomMessage(
                RoomMessageEventContent::text_plain("raclette"),
            ))
            .unwrap(),
        });
        let value =
            LatestEventValue::from_base_latest_event_value(base_value, &room, &client).await;

        assert_matches!(value, LatestEventValue::Local { timestamp, sender, profile, content, is_sending } => {
            assert_eq!(u64::from(timestamp.get()), 42u64);
            assert_eq!(sender, "@example:localhost");
            assert_matches!(profile, TimelineDetails::Unavailable);
            assert_matches!(
                content,
                TimelineItemContent::MsgLike(MsgLikeContent { kind: MsgLikeKind::Message(_), .. })
            );
            assert!(is_sending);
        })
    }

    #[async_test]
    async fn test_local_cannot_be_sent() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let room = server.sync_room(&client, JoinedRoomBuilder::new(room_id!("!r0"))).await;

        let base_value = BaseLatestEventValue::LocalCannotBeSent(LocalLatestEventValue {
            timestamp: MilliSecondsSinceUnixEpoch(uint!(42)),
            content: SerializableEventContent::new(&AnyMessageLikeEventContent::RoomMessage(
                RoomMessageEventContent::text_plain("raclette"),
            ))
            .unwrap(),
        });
        let value =
            LatestEventValue::from_base_latest_event_value(base_value, &room, &client).await;

        assert_matches!(value, LatestEventValue::Local { timestamp, sender, profile, content, is_sending } => {
            assert_eq!(u64::from(timestamp.get()), 42u64);
            assert_eq!(sender, "@example:localhost");
            assert_matches!(profile, TimelineDetails::Unavailable);
            assert_matches!(
                content,
                TimelineItemContent::MsgLike(MsgLikeContent { kind: MsgLikeKind::Message(_), .. })
            );
            assert!(is_sending.not());
        })
    }

    #[async_test]
    async fn test_remote_edit() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let room = server.sync_room(&client, JoinedRoomBuilder::new(room_id!("!r0"))).await;
        let sender = user_id!("@mnt_io:matrix.org");
        let event_factory = EventFactory::new();

        let base_value = BaseLatestEventValue::Remote(RemoteLatestEventValue::from_plaintext(
            event_factory
                .server_ts(42)
                .sender(sender)
                .text_msg("bonjour")
                .event_id(event_id!("$ev1"))
                .edit(event_id!("$ev0"), RoomMessageEventContent::text_plain("fondue").into())
                .into_raw_sync(),
        ));
        let value =
            LatestEventValue::from_base_latest_event_value(base_value, &room, &client).await;

        assert_matches!(value, LatestEventValue::Remote { timestamp, sender: received_sender, is_own, profile, content } => {
            assert_eq!(u64::from(timestamp.get()), 42u64);
            assert_eq!(received_sender, sender);
            assert!(is_own.not());
            assert_matches!(profile, TimelineDetails::Unavailable);
            assert_matches!(
                content,
                TimelineItemContent::MsgLike(MsgLikeContent { kind: MsgLikeKind::Message(message), .. }) => {
                    assert_eq!(message.body(), "fondue");
                }
            );
        })
    }
}
