//
// Copyright (C) 2021 The Android Open Source Project
//
// 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.
//

//! ProfCollect tracing scheduler.

use std::sync::mpsc::{sync_channel, SyncSender};
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;

use crate::config::{Config, PROFILE_OUTPUT_DIR, TRACE_OUTPUT_DIR};
use crate::trace_provider::{self, TraceProvider};
use anyhow::{anyhow, ensure, Context, Result};

pub struct Scheduler {
    /// Signal to terminate the periodic collection worker thread, None if periodic collection is
    /// not scheduled.
    termination_ch: Option<SyncSender<()>>,
    /// The preferred trace provider for the system.
    trace_provider: Arc<Mutex<dyn TraceProvider + Send>>,
}

impl Scheduler {
    pub fn new() -> Result<Self> {
        let p = trace_provider::get_trace_provider()?;
        Ok(Scheduler { termination_ch: None, trace_provider: p })
    }

    fn is_scheduled(&self) -> bool {
        self.termination_ch.is_some()
    }

    pub fn schedule_periodic(&mut self, config: &Config) -> Result<()> {
        ensure!(!self.is_scheduled(), "Already scheduled.");

        let (sender, receiver) = sync_channel(1);
        self.termination_ch = Some(sender);

        // Clone config and trace_provider ARC for the worker thread.
        let config = config.clone();
        let trace_provider = self.trace_provider.clone();

        thread::spawn(move || {
            loop {
                match receiver.recv_timeout(config.collection_interval) {
                    Ok(_) => break,
                    Err(_) => {
                        // Did not receive a termination signal, initiate trace event.
                        trace_provider.lock().unwrap().trace(
                            &TRACE_OUTPUT_DIR,
                            "periodic",
                            &config.sampling_period,
                        );
                    }
                }
            }
        });
        Ok(())
    }

    pub fn terminate_periodic(&mut self) -> Result<()> {
        self.termination_ch
            .as_ref()
            .ok_or_else(|| anyhow!("Not scheduled"))?
            .send(())
            .context("Scheduler worker disappeared.")?;
        self.termination_ch = None;
        Ok(())
    }

    pub fn one_shot(&self, config: &Config, tag: &str) -> Result<()> {
        let trace_provider = self.trace_provider.clone();
        trace_provider.lock().unwrap().trace(&TRACE_OUTPUT_DIR, tag, &config.sampling_period);
        Ok(())
    }

    pub fn process(&self, blocking: bool) -> Result<()> {
        let trace_provider = self.trace_provider.clone();
        let handle = thread::spawn(move || {
            trace_provider
                .lock()
                .unwrap()
                .process(&TRACE_OUTPUT_DIR, &PROFILE_OUTPUT_DIR)
                .expect("Failed to process profiles.");
        });
        if blocking {
            handle.join().map_err(|_| anyhow!("Profile process thread panicked."))?;
        }
        Ok(())
    }

    pub fn get_trace_provider_name(&self) -> &'static str {
        self.trace_provider.lock().unwrap().get_name()
    }
}