// Copyright 2019 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 {
    anyhow::Error,
    async_trait::async_trait,
    fidl_fuchsia_test_hub as fhub,
    futures::{channel::*, lock::Mutex, sink::SinkExt, StreamExt},
    std::{collections::HashMap, sync::Arc},
    test_utils_lib::injectors::ProtocolInjector,
};

#[derive(Debug)]
pub enum HubReportEvent {
    DirectoryListing { listing: Vec<String>, responder: fhub::HubReportListDirectoryResponder },
    FileContent { content: String, responder: fhub::HubReportReportFileContentResponder },
}

/// A futures channel between the task where the integration test is running
/// and the task where the HubReport protocol is being serviced.
pub struct HubReportChannel {
    pub receiver: Option<mpsc::Receiver<HubReportEvent>>,
    pub sender: Option<mpsc::Sender<HubReportEvent>>,
}

fn get_or_insert_channel(
    map: &mut HashMap<String, HubReportChannel>,
    path: String,
) -> &mut HubReportChannel {
    map.entry(path.clone()).or_insert({
        let (sender, receiver) = mpsc::channel(0);
        HubReportChannel { receiver: Some(receiver), sender: Some(sender) }
    })
}

/// Framework capability that serves the HubReport FIDL protocol
pub struct HubReportCapability {
    // Path <-> Channel mapping
    observers: Arc<Mutex<HashMap<String, HubReportChannel>>>,

    // This sender is cloned and moved into to the server
    channel_close_tx: mpsc::Sender<()>,
}

impl HubReportCapability {
    pub fn new() -> (Arc<Self>, mpsc::Receiver<()>) {
        let (tx, rx) = mpsc::channel(0);
        (
            Arc::new(Self {
                observers: Arc::new(Mutex::new(HashMap::new())),
                channel_close_tx: tx,
            }),
            rx,
        )
    }

    /// Given a path, blocks until the component responds with a directory listing
    /// or file content.
    pub async fn observe(&self, path: &str) -> HubReportEvent {
        let mut receiver = {
            let mut observers = self.observers.lock().await;
            // Avoid holding onto to the observers lock while waiting for a
            // message to avoid deadlock.
            let channel = get_or_insert_channel(&mut observers, path.to_string());
            channel.receiver.take().unwrap()
        };
        let event = receiver.next().await.expect("Missing HubReportEvent");
        // Transfer ownership back to the observers HashMap after the listing has
        // been received.
        let mut observers = self.observers.lock().await;
        let channel = get_or_insert_channel(&mut observers, path.to_string());
        channel.receiver = Some(receiver);

        return event;
    }
}

#[async_trait]
impl ProtocolInjector for HubReportCapability {
    type Marker = fhub::HubReportMarker;

    async fn serve(
        self: Arc<Self>,
        mut request_stream: fhub::HubReportRequestStream,
    ) -> Result<(), Error> {
        while let Some(Ok(request)) = request_stream.next().await {
            let (path, event) = match request {
                fhub::HubReportRequest::ListDirectory { path, entries, responder } => {
                    (path, HubReportEvent::DirectoryListing { listing: entries, responder })
                }
                fhub::HubReportRequest::ReportFileContent { path, content, responder } => {
                    (path, HubReportEvent::FileContent { content, responder })
                }
            };
            let mut sender = {
                // Avoid holding onto to the observers lock while sending a
                // message to avoid deadlock.
                let mut observers = self.observers.lock().await;
                let channel = get_or_insert_channel(&mut observers, path.clone());
                channel.sender.take().unwrap()
            };
            sender.send(event).await?;
            // Transfer ownership back to the observers HashMap after the listing has
            // been sent.
            let mut observers = self.observers.lock().await;
            let channel = get_or_insert_channel(&mut observers, path.clone());
            channel.sender = Some(sender);
        }

        // Notify HubTestHook that the channel has been closed
        self.channel_close_tx.clone().send(()).await?;

        Ok(())
    }
}