// Copyright 2024 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 std::cmp::Ordering;

use super::{RoomListItem, Sorter};

fn cmp<'a, 'b, F>(names: F, left: &'a RoomListItem, right: &'b RoomListItem) -> Ordering
where
    F: Fn(&'a RoomListItem, &'b RoomListItem) -> (Option<&'a str>, Option<&'b str>),
{
    let (left_name, right_name) = names(left, right);

    left_name.cmp(&right_name)
}

/// Create a new sorter that will sort two [`RoomListItem`] by name, i.e. by
/// comparing their display names. A lexicographically ordering is applied, i.e.
/// "a" < "b".
pub fn new_sorter() -> impl Sorter {
    fn names<'a, 'b>(
        left: &'a RoomListItem,
        right: &'b RoomListItem,
    ) -> (Option<&'a str>, Option<&'b str>) {
        (left.cached_display_name.as_deref(), right.cached_display_name.as_deref())
    }

    move |left, right| -> Ordering { cmp(names, left, right) }
}

#[cfg(test)]
mod tests {
    use matrix_sdk::test_utils::mocks::MatrixMockServer;
    use matrix_sdk_test::async_test;
    use ruma::room_id;

    use super::{super::super::filters::new_rooms, *};

    #[async_test]
    async fn test_with_two_names() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let [room_a, room_b] =
            new_rooms([room_id!("!a:b.c"), room_id!("!d:e.f")], &client, &server).await;

        // `room_a` has a “greater name” than `room_b`.
        {
            assert_eq!(
                cmp(|_left, _right| (Some("Foo"), Some("Baz")), &room_a, &room_b),
                Ordering::Greater
            );
        }

        // `room_a` has a “lesser name” than `room_b`.
        {
            assert_eq!(
                cmp(|_left, _right| (Some("Bar"), Some("Baz")), &room_a, &room_b),
                Ordering::Less
            );
        }

        // `room_a` has the same name than `room_b`.
        {
            assert_eq!(
                cmp(|_left, _right| (Some("Baz"), Some("Baz")), &room_a, &room_b),
                Ordering::Equal
            );
        }
    }

    #[async_test]
    async fn test_with_one_name() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let [room_a, room_b] =
            new_rooms([room_id!("!a:b.c"), room_id!("!d:e.f")], &client, &server).await;

        // `room_a` has a name, `room_b` has no name.
        {
            assert_eq!(
                cmp(|_left, _right| (Some("Foo"), None), &room_a, &room_b),
                Ordering::Greater
            );
        }

        // `room_a` has no name, `room_b` has a name.
        {
            assert_eq!(cmp(|_left, _right| (None, Some("Bar")), &room_a, &room_b), Ordering::Less);
        }
    }

    #[async_test]
    async fn test_with_zero_name() {
        let server = MatrixMockServer::new().await;
        let client = server.client_builder().build().await;
        let [room_a, room_b] =
            new_rooms([room_id!("!a:b.c"), room_id!("!d:e.f")], &client, &server).await;

        // `room_a` and `room_b` has no name.
        {
            assert_eq!(cmp(|_left, _right| (None, None), &room_a, &room_b), Ordering::Equal);
        }
    }
}
