// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! A process-wide libuv event loop for library use.

use iotask = uv_iotask;
use uv_iotask::{IoTask, spawn_iotask};

use core::clone::Clone;
use core::comm::{Port, Chan, SharedChan, select2i};
use core::option::{Some, None};
use core::task::{task, SingleThreaded, spawn};
use core::task;
use core::unstable::global::{global_data_clone_create, global_data_clone};
use core::unstable::weak_task::weaken_task;

/**
 * Race-free helper to get access to a global task where a libuv
 * loop is running.
 *
 * Use `uv::hl::interact` to do operations against the global
 * loop that this function returns.
 *
 * # Return
 *
 * * A `hl::high_level_loop` that encapsulates communication with the global
 * loop.
 */
pub fn get() -> IoTask {
    return get_monitor_task_gl();
}

#[doc(hidden)]
fn get_monitor_task_gl() -> IoTask {

    type MonChan = Chan<IoTask>;

    struct GlobalIoTask(IoTask);

    impl Clone for GlobalIoTask {
        fn clone(&self) -> GlobalIoTask {
            GlobalIoTask((**self).clone())
        }
    }

    fn key(_: GlobalIoTask) { }

    match unsafe { global_data_clone(key) } {
        Some(GlobalIoTask(iotask)) => iotask,
        None => {
            let iotask: IoTask = spawn_loop();
            let mut installed = false;
            let final_iotask = unsafe {
                do global_data_clone_create(key) {
                    installed = true;
                    ~GlobalIoTask(iotask.clone())
                }
            };
            if installed {
                do task().unlinked().spawn() {
                    unsafe {
                        debug!("global monitor task starting");
                        // As a weak task the runtime will notify us
                        // when to exit
                        do weaken_task |weak_exit_po| {
                            debug!("global monitor task is weak");
                            weak_exit_po.recv();
                            iotask::exit(&iotask);
                            debug!("global monitor task is unweak");
                        };
                        debug!("global monitor task exiting");
                    }
                }
            } else {
                iotask::exit(&iotask);
            }

            match final_iotask {
                GlobalIoTask(iotask) => iotask
            }
        }
    }
}

fn spawn_loop() -> IoTask {
    let builder = do task().add_wrapper |task_body| {
        let result: ~fn() = || {
            // The I/O loop task also needs to be weak so it doesn't keep
            // the runtime alive
            unsafe {
                do weaken_task |_| {
                    debug!("global libuv task is now weak");
                    task_body();

                    // We don't wait for the exit message on weak_exit_po
                    // because the monitor task will tell the uv loop when to
                    // exit

                    debug!("global libuv task is leaving weakened state");
                }
            }
        };
        result
    };
    let builder = builder.unlinked();
    spawn_iotask(builder)
}

#[cfg(test)]
mod test {
    use core::prelude::*;

    use get_gl = uv_global_loop::get;
    use uv::iotask;
    use uv::ll;
    use uv_iotask::IoTask;

    use core::iter;
    use core::libc;
    use core::ptr;
    use core::task;
    use core::cast::transmute;
    use core::libc::c_void;
    use core::comm::{stream, SharedChan, Chan};

    extern fn simple_timer_close_cb(timer_ptr: *ll::uv_timer_t) {
        unsafe {
            let exit_ch_ptr = ll::get_data_for_uv_handle(
                timer_ptr as *libc::c_void);
            let exit_ch = transmute::<*c_void, ~Chan<bool>>(exit_ch_ptr);
            exit_ch.send(true);
            debug!("EXIT_CH_PTR simple_timer_close_cb exit_ch_ptr: %?",
                     exit_ch_ptr);
        }
    }
    extern fn simple_timer_cb(timer_ptr: *ll::uv_timer_t,
                             _status: libc::c_int) {
        unsafe {
            debug!(~"in simple timer cb");
            ll::timer_stop(timer_ptr);
            let hl_loop = &get_gl();
            do iotask::interact(hl_loop) |_loop_ptr| {
                debug!(~"closing timer");
                unsafe {
                    ll::close(timer_ptr, simple_timer_close_cb);
                }
                debug!(~"about to deref exit_ch_ptr");
                debug!(~"after msg sent on deref'd exit_ch");
            };
            debug!(~"exiting simple timer cb");
        }
    }

    fn impl_uv_hl_simple_timer(iotask: &IoTask) {
        unsafe {
            let (exit_po, exit_ch) = stream::<bool>();
            let exit_ch_ptr: *libc::c_void = transmute(~exit_ch);
            debug!("EXIT_CH_PTR newly created exit_ch_ptr: %?",
                            exit_ch_ptr);
            let timer_handle = ll::timer_t();
            let timer_ptr = ptr::addr_of(&timer_handle);
            do iotask::interact(iotask) |loop_ptr| {
                unsafe {
                    debug!(~"user code inside interact loop!!!");
                    let init_status = ll::timer_init(loop_ptr, timer_ptr);
                    if(init_status == 0i32) {
                        ll::set_data_for_uv_handle(
                            timer_ptr as *libc::c_void,
                            exit_ch_ptr);
                        let start_status = ll::timer_start(timer_ptr,
                                                           simple_timer_cb,
                                                           1u, 0u);
                        if(start_status != 0i32) {
                            fail!(~"failure on ll::timer_start()");
                        }
                    }
                    else {
                        fail!(~"failure on ll::timer_init()");
                    }
                }
            };
            exit_po.recv();
            debug!(
                ~"global_loop timer test: msg recv on exit_po, done..");
        }
    }

    #[test]
    fn test_gl_uv_global_loop_high_level_global_timer() {
        let hl_loop = &get_gl();
        let (exit_po, exit_ch) = stream::<()>();
        task::spawn_sched(task::ManualThreads(1u), || {
            let hl_loop = &get_gl();
            impl_uv_hl_simple_timer(hl_loop);
            exit_ch.send(());
        });
        impl_uv_hl_simple_timer(hl_loop);
        exit_po.recv();
    }

    // keeping this test ignored until some kind of stress-test-harness
    // is set up for the build bots
    #[test]
    #[ignore]
    fn test_stress_gl_uv_global_loop_high_level_global_timer() {
        let (exit_po, exit_ch) = stream::<()>();
        let exit_ch = SharedChan(exit_ch);
        let cycles = 5000u;
        for iter::repeat(cycles) {
            let exit_ch_clone = exit_ch.clone();
            task::spawn_sched(task::ManualThreads(1u), || {
                let hl_loop = &get_gl();
                impl_uv_hl_simple_timer(hl_loop);
                exit_ch_clone.send(());
            });
        };
        for iter::repeat(cycles) {
            exit_po.recv();
        };
        debug!(~"test_stress_gl_uv_global_loop_high_level_global_timer"+
            ~" exiting sucessfully!");
    }
}