// Copyright 2023 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use std::collections::{HashMap, VecDeque};
use std::sync::Arc;
use std::task::Poll;

use bt_common::packet_encoding::Decodable;
use bt_gatt::client::CharacteristicNotification;
use bt_gatt::types::{Error as BtGattError, Handle};
use futures::stream::{BoxStream, FusedStream, SelectAll};
use futures::{Stream, StreamExt};
use parking_lot::Mutex;

use crate::client::error::Error;
use crate::client::error::ServiceError;
use crate::client::BroadcastSourceIdTracker;
use crate::types::*;

#[derive(Clone, Debug, PartialEq)]
pub enum BroadcastAudioScanServiceEvent {
    // Broadcast Audio Scan Service (BASS) server requested for SyncInfo through PAST procedure.
    SyncInfoRequested(BroadcastId),
    // BASS server failed to synchornize to PA or did not synchronize to PA.
    NotSyncedToPa(BroadcastId),
    // BASS server successfully synced to PA.
    SyncedToPa(BroadcastId),
    // BASS server failed to sync to PA since SyncInfo wasn't received.
    SyncedFailedNoPast(BroadcastId),
    // BASS server requires code to since the BIS is encrypted.
    BroadcastCodeRequired(BroadcastId),
    // BASS server failed to decrypt BIS using the previously provided code.
    InvalidBroadcastCode(BroadcastId, [u8; 16]),
    // Received a packet from the BASS server not recognized by this library.
    UnknownPacket,
}

impl BroadcastAudioScanServiceEvent {
    pub(crate) fn from_broadcast_receive_state(
        state: &ReceiveState,
    ) -> Vec<BroadcastAudioScanServiceEvent> {
        let mut events = Vec::new();
        let pa_sync_state = state.pa_sync_state();
        let broadcast_id = state.broadcast_id();
        match pa_sync_state {
            PaSyncState::SyncInfoRequest => {
                events.push(BroadcastAudioScanServiceEvent::SyncInfoRequested(broadcast_id))
            }
            PaSyncState::Synced => {
                events.push(BroadcastAudioScanServiceEvent::SyncedToPa(broadcast_id))
            }
            PaSyncState::FailedToSync | PaSyncState::NotSynced => {
                events.push(BroadcastAudioScanServiceEvent::NotSyncedToPa(broadcast_id))
            }
            PaSyncState::NoPast => {
                events.push(BroadcastAudioScanServiceEvent::SyncedFailedNoPast(broadcast_id))
            }
        }
        match state.big_encryption() {
            EncryptionStatus::BroadcastCodeRequired => {
                events.push(BroadcastAudioScanServiceEvent::BroadcastCodeRequired(broadcast_id))
            }
            EncryptionStatus::BadCode(code) => events.push(
                BroadcastAudioScanServiceEvent::InvalidBroadcastCode(broadcast_id, code.clone()),
            ),
            _ => {}
        };
        events
    }
}

pub struct BroadcastAudioScanServiceEventStream {
    // Polled to receive BASS notifications.
    notification_streams:
        SelectAll<BoxStream<'static, Result<CharacteristicNotification, BtGattError>>>,

    event_queue: VecDeque<Result<BroadcastAudioScanServiceEvent, Error>>,
    terminated: bool,

    // States to be updated.
    id_tracker: Arc<Mutex<BroadcastSourceIdTracker>>,
    receive_states: Arc<Mutex<HashMap<Handle, Option<BroadcastReceiveState>>>>,
}

impl BroadcastAudioScanServiceEventStream {
    pub(crate) fn new(
        notification_streams: SelectAll<
            BoxStream<'static, Result<CharacteristicNotification, BtGattError>>,
        >,
        id_tracker: Arc<Mutex<BroadcastSourceIdTracker>>,
        receive_states: Arc<Mutex<HashMap<Handle, Option<BroadcastReceiveState>>>>,
    ) -> Self {
        Self {
            notification_streams,
            event_queue: VecDeque::new(),
            terminated: false,
            id_tracker,
            receive_states,
        }
    }
}

impl FusedStream for BroadcastAudioScanServiceEventStream {
    fn is_terminated(&self) -> bool {
        self.terminated
    }
}

impl Stream for BroadcastAudioScanServiceEventStream {
    type Item = Result<BroadcastAudioScanServiceEvent, Error>;

    fn poll_next(
        mut self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> Poll<Option<Self::Item>> {
        if self.terminated {
            return Poll::Ready(None);
        }

        loop {
            match self.notification_streams.poll_next_unpin(cx) {
                Poll::Pending => {}
                Poll::Ready(None) => {
                    self.event_queue.push_back(Err(Error::Service(
                        super::error::ServiceError::NotificationChannelClosed(format!(
                            "GATT notification stream for BRS characteristics closed"
                        )),
                    )));
                }
                Poll::Ready(Some(received)) => {
                    match received {
                        Err(error) => match error {
                            BtGattError::PeerNotRecognized(_)
                            | BtGattError::ScanFailed(_)
                            | BtGattError::Other(_) => {
                                self.event_queue.push_back(Err(Error::Service(
                                    ServiceError::NotificationChannelClosed(format!(
                                        "unexpected error encountered from GATT notification"
                                    )),
                                )));
                            }
                            BtGattError::PeerDisconnected(id) => {
                                self.event_queue.push_back(Err(Error::Service(
                                    ServiceError::NotificationChannelClosed(format!(
                                        "peer ({id}) disconnected"
                                    )),
                                )));
                            }
                            _ => {} // TODO(b/308483171): decide what to do for non-critical errors.
                        },
                        Ok(notification) => {
                            let Ok((brs, _)) =
                                BroadcastReceiveState::decode(notification.value.as_slice())
                            else {
                                self.event_queue
                                    .push_back(Ok(BroadcastAudioScanServiceEvent::UnknownPacket));
                                break;
                            };
                            match &brs {
                                BroadcastReceiveState::Empty => {}
                                BroadcastReceiveState::NonEmpty(state) => {
                                    let events = BroadcastAudioScanServiceEvent::from_broadcast_receive_state(state);
                                    events
                                        .into_iter()
                                        .for_each(|e| self.event_queue.push_back(Ok(e)));

                                    // Update broadcast ID to source ID mapping.
                                    let _ = self
                                        .id_tracker
                                        .lock()
                                        .update(state.source_id(), state.broadcast_id());
                                }
                            };
                            {
                                // Update the Broadcast Receive States.
                                let mut lock = self.receive_states.lock();
                                let char = lock.get_mut(&notification.handle).unwrap();
                                char.replace(brs);
                            }
                        }
                    }
                }
            };
            break;
        }

        let popped = self.event_queue.pop_front();
        match popped {
            None => Poll::Pending,
            Some(item) => match item {
                Ok(event) => Poll::Ready(Some(Ok(event))),
                Err(e) => {
                    // If an error was received, we terminate the event stream, but send an error to
                    // indicate why it was terminated.
                    self.terminated = true;
                    Poll::Ready(Some(Err(e)))
                }
            },
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use futures::channel::mpsc::unbounded;

    #[test]
    fn poll_broadcast_audio_scan_service_event_stream() {
        let mut streams = SelectAll::new();
        let (sender1, receiver1) = unbounded();
        let (sender2, receiver2) = unbounded();
        streams.push(receiver1.boxed());
        streams.push(receiver2.boxed());

        let id_tracker = Arc::new(Mutex::new(BroadcastSourceIdTracker::new()));
        let receive_states =
            Arc::new(Mutex::new(HashMap::from([(Handle(0x1), None), (Handle(0x2), None)])));
        let mut event_streams =
            BroadcastAudioScanServiceEventStream::new(streams, id_tracker, receive_states);

        // Send notifications to underlying streams.
        let bad_code_status =
            EncryptionStatus::BadCode([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);
        #[rustfmt::skip]
        sender1
            .unbounded_send(Ok(CharacteristicNotification {
                handle: Handle(0x1),
                value: vec![
                    0x01, AddressType::Public as u8,         // source id and address type
                    0x02, 0x03, 0x04, 0x05, 0x06, 0x07,      // address
                    0x01, 0x01, 0x02, 0x03,                  // ad set id and broadcast id
                    PaSyncState::FailedToSync as u8,
                    bad_code_status.raw_value(),
                    1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,  // bad code
                    0x00,                                    // no subgroups
                ],
                maybe_truncated: false,
            }))
            .expect("should send");

        #[rustfmt::skip]
        sender2
            .unbounded_send(Ok(CharacteristicNotification {
                handle: Handle(0x2),
                value: vec![
                    0x02, AddressType::Public as u8,             // source id and address type
                    0x03, 0x04, 0x05, 0x06, 0x07, 0x08,          // address
                    0x01, 0x02, 0x03, 0x04,                      // ad set id and broadcast id
                    PaSyncState::NoPast as u8,
                    EncryptionStatus::NotEncrypted.raw_value(),
                    0x00,                                        // no subgroups
                ],
                maybe_truncated: false,
            }))
            .expect("should send");

        // Events should have been generated from notifications.
        let mut noop_cx = futures::task::Context::from_waker(futures::task::noop_waker_ref());
        match event_streams.poll_next_unpin(&mut noop_cx) {
            Poll::Ready(Some(Ok(event))) => assert_eq!(
                event,
                BroadcastAudioScanServiceEvent::NotSyncedToPa(BroadcastId::new(0x030201))
            ),
            _ => panic!("should have received event"),
        }
        match event_streams.poll_next_unpin(&mut noop_cx) {
            Poll::Ready(Some(Ok(event))) => assert_eq!(
                event,
                BroadcastAudioScanServiceEvent::InvalidBroadcastCode(
                    BroadcastId::new(0x030201),
                    [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
                )
            ),
            _ => panic!("should have received event"),
        }
        match event_streams.poll_next_unpin(&mut noop_cx) {
            Poll::Ready(Some(Ok(event))) => assert_eq!(
                event,
                BroadcastAudioScanServiceEvent::SyncedFailedNoPast(BroadcastId::new(0x040302))
            ),
            _ => panic!("should have received event"),
        }

        // Should be pending because no more events generated from notifications.
        assert!(event_streams.poll_next_unpin(&mut noop_cx).is_pending());

        // Send notifications to underlying streams.
        #[rustfmt::skip]
        sender2
            .unbounded_send(Ok(CharacteristicNotification {
                handle: Handle(0x2),
                value: vec![
                    0x02, AddressType::Public as u8,             // source id and address type
                    0x03, 0x04, 0x05, 0x06, 0x07, 0x08,          // address
                    0x01, 0x02, 0x03, 0x04,                      // ad set id and broadcast id
                    PaSyncState::Synced as u8,
                    EncryptionStatus::NotEncrypted.raw_value(),
                    0x00,                                        // no subgroups
                ],
                maybe_truncated: false,
            }))
            .expect("should send");

        // Event should have been generated from notification.
        let mut noop_cx = futures::task::Context::from_waker(futures::task::noop_waker_ref());
        match event_streams.poll_next_unpin(&mut noop_cx) {
            Poll::Ready(Some(Ok(event))) => assert_eq!(
                event,
                BroadcastAudioScanServiceEvent::SyncedToPa(BroadcastId::new(0x040302))
            ),
            _ => panic!("should have received event"),
        }

        // Should be pending because no more events generated from notifications.
        assert!(event_streams.poll_next_unpin(&mut noop_cx).is_pending());
    }
}