use crate::utility::list::List;
use crate::kernel::thread::Thread;
use crate::simulator::interrupt::InterruptStatus::InterruptOff;
use crate::simulator::machine::Machine;
use std::cell::RefCell;
use std::rc::Rc;

use super::system::System;
use super::thread_manager::ThreadManager;

///     Structure of a Semaphore used for synchronisation
pub struct Semaphore {

    /// Counter of simultanous Semaphore
    counter:i32,
    /// QUeue of Semaphore waiting to be exucated
    waiting_queue:List<Rc<RefCell<Thread>>>,

}

impl Semaphore {

    ///     Initializes a semaphore, so that it can be used for synchronization.
    ///
    ///  ### Parameters
    /// - *counter* initial value of counter
    /// - *thread_manager* Thread manager which managing threads
    pub fn new(counter: i32) -> Semaphore{
        Semaphore { counter, waiting_queue: List::new()}
    }

    ///     Decrement the value, and wait if it becomes < 0. Checking the
    ///	value and decrementing must be done atomically, so we
    ///	need to disable interrupts before checking the value.
    ///
    ///	Note that thread_manager::thread_sleep assumes that interrupts are disabled
    ///	when it is called.
    ///
    /// ### Parameters TODO Refaire
    /// - *current_thread* the current thread
    /// - *machine* the machine where the threads are executed
    pub fn p(&mut self, machine: &mut Machine, thread_manager: &mut ThreadManager) {
        let old_status = machine.interrupt.set_status(InterruptOff);
        self.counter -= 1;
        if self.counter < 0 {
            match thread_manager.get_g_current_thread() {
                Some(thread) => {
                    let rc1_thread = Rc::clone(thread);
                    let rc2_thread = Rc::clone(thread);
                    self.waiting_queue.push(rc1_thread);
                    thread_manager.thread_sleep(machine, rc2_thread);
                },
                None => unreachable!("Current thread should not be None")
            }
        }
        machine.interrupt.set_status(old_status);
    }

    /// Increment semaphore value, waking up a waiting thread if any.
    /// As with P(), this operation must be atomic, so we need to disable
    /// interrupts.
    ///
    /// scheduler::ready_to_run() assumes that interrupts
    /// are disabled when it is called.
    ///
    /// ### Parameters
    /// - **machine** the machine where the threads are executed
    /// - **scheduler** the scheduler which determine which thread to execute
    pub fn v(&mut self, system: &mut System){
        let old_status = system.get_machine().interrupt.set_status(InterruptOff);
        self.counter += 1;
        if self.waiting_queue.peek() != None {
            system.get_thread_manager().ready_to_run(self.waiting_queue.pop().unwrap());
        }
        system.get_machine().interrupt.set_status(old_status);
    }
}

/// Lock used for synchronisation, can be interpreted has a Semaphore with a
/// counter of 1
/// It's used for critical parts
pub struct Lock{

    /// Thread owning the lock
    owner: Option<Rc<RefCell<Thread>>>,
    /// The queue of threads waiting for execution
    waiting_queue:List<Rc<RefCell<Thread>>>,
    /// A boolean definig if the lock is free or not
    free: bool

}

impl Lock {

    ///    Initialize a Lock, so that it can be used for synchronization.
    /// The lock is initialy free
    ///
    /// ### Parameters
    /// - **thread_manager** Thread manager which managing threads
    pub fn new() -> Lock {
        Lock { owner: None, waiting_queue: List::new(), free: true }
    }

    ///    Wait until the lock become free.  Checking the
    ///	state of the lock (free or busy) and modify it must be done
    ///	atomically, so we need to disable interrupts before checking
    ///	the value of free.
    ///
    ///	Note that thread_manager::thread_seep assumes that interrupts are disabled
    ///	when it is called.
    ///
    /// ### Parameters
    /// - **current_thread** the current thread
    /// - **machine** the machine where the threads are executed
    pub fn acquire(&mut self, machine: &mut Machine, thread_manager: &mut ThreadManager) {
        let old_status = machine.interrupt.set_status(InterruptOff);
        if self.free {
            self.free = false;
            self.owner = Option::Some(match thread_manager.get_g_current_thread() {
                Some(th) => {
                    Rc::clone(&th)
                },
                None => unreachable!()
            });
        } else {
            match thread_manager.get_g_current_thread() {
                Some(x) => {
                    let x = Rc::clone(&x);
                    self.waiting_queue.push(Rc::clone(&x));
                    thread_manager.thread_sleep(machine, Rc::clone(&x));
                },
                None => unreachable!("Current thread should not be None")
            }
        }

        machine.interrupt.set_status(old_status);
    }

    ///     Wake up a waiter if necessary, or release it if no thread is waiting.
    /// We check that the lock is held by the g_current_thread.
    ///	As with Acquire, this operation must be atomic, so we need to disable
    ///	interrupts.  scheduler::ready_to_run() assumes that threads
    ///	are disabled when it is called.
    ///
    /// ### Parameters
    /// - **machine** the machine where the code is executed
    /// - **scheduler** the scheduler which determine which thread to execute
    pub fn release(&mut self, system: &mut System) {
        let old_status = system.get_machine().interrupt.set_status(InterruptOff);
        
        match system.get_thread_manager().get_g_current_thread() {
            Some(thread) => {
                if self.held_by_current_thread(system) {
                    if self.waiting_queue.peek() != None {
                        self.owner = Some(self.waiting_queue.pop().unwrap());
                        match &self.owner {
                            Some(x) => system.get_thread_manager().ready_to_run(Rc::clone(&x)),
                            None => ()
                        }
                    } else {
                        self.free = true;
                        self.owner = None;
                    }
                }
            }
            None => ()
        }

        system.get_machine().interrupt.set_status(old_status);
    }

    pub fn held_by_current_thread(&mut self, system: &mut System) -> bool {
        match &self.owner {
            Some(x) => 
                match system.get_thread_manager().get_g_current_thread() {
                    Some(thread) => Rc::ptr_eq(&x, &thread),
                    None => false
                }
            None => false
        }
    }
}

/// Structure of a condition used for synchronisation
pub struct Condition{

    /// The queue of threads waiting for execution
    waiting_queue:List<Rc<RefCell<Thread>>>,
    
}

impl Condition {

    /// Initializes a Condition, so that it can be used for synchronization.
    ///
    /// ### Parameters
    /// - *thread_manager* Thread manager which managing threads
    pub fn new() -> Condition {
        Condition{ waiting_queue: List::new()}
    }

    ///  Block the calling thread (put it in the wait queue).
    ///  This operation must be atomic, so we need to disable interrupts.
    ///
    /// ### Parameters
    /// - **current_thread** the current thread
    /// - **machine** the machine where threads are executed
    pub fn wait(&mut self, machine: &mut Machine, thread_manager: &mut ThreadManager) {
        let old_status = machine.interrupt.set_status(InterruptOff);
        match thread_manager.get_g_current_thread() {
            Some(thread) => {
                let rc1 = Rc::clone(thread);
                let rc2 = Rc::clone(thread);
                self.waiting_queue.push(rc1);
                thread_manager.thread_sleep(machine, rc2);
            },
            None => unreachable!()
        }

        machine.interrupt.set_status(old_status);
    }

    /// Wake up the first thread of the wait queue (if any).
    /// This operation must be atomic, so we need to disable interrupts.
    ///
    /// ### Parameters
    /// - **machine** the machine where the code is executed
    /// - **scheduler** the scheduler which determine which thread to execute
    pub fn signal(&mut self, system: &mut System) {
        let old_status = system.get_machine().interrupt.set_status(InterruptOff);

        if self.waiting_queue.peek() != None {
            system.get_thread_manager().ready_to_run(self.waiting_queue.pop().unwrap());
        }

        system.get_machine().interrupt.set_status(old_status);

    }

    /// Wake up all threads waiting in the waitqueue of the condition
    /// This operation must be atomic, so we need to disable interrupts.
    ///
    /// ### Parameters
    /// - **machine** the machine where the code is executed
    /// - **scheduler** the scheduler which determine which thread to execute
    pub fn broadcast(&mut self, system: &mut System) {
        let old_status = system.get_machine().interrupt.set_status(InterruptOff);

        while self.waiting_queue.peek() != None {
            system.get_thread_manager().ready_to_run(self.waiting_queue.pop().unwrap());
        }
        system.get_machine().interrupt.set_status(old_status);

    }

}

// #[cfg(test)]
// mod test {
//     use std::{rc::Rc, cell::RefCell};

//     use crate::{kernel::{thread::Thread, synch::{Semaphore, Lock}}, init_system, simulator::machine::Machine};

//     #[test]
//     fn test_semaphore_single() {
//         // Init
//         let system = init_system!();
//         let mut semaphore = Semaphore::new(1);
//         let thread = Rc::new(RefCell::new(Thread::new("test_semaphore")));
//         // P
//         semaphore.p(system, thread);
//         assert_eq!(semaphore.counter, 0);
//         assert!(semaphore.waiting_queue.is_empty());
//         // V
//         semaphore.v(Rc::clone(&system));
//         assert_eq!(semaphore.counter, 1);
//         assert!(semaphore.waiting_queue.is_empty());
//     }

//     #[test]
//     #[ignore]
//     fn test_semaphore_multiple() {
//         // Init
//         let system = init_system!();
//         let tm = system.borrow_mut().get_thread_manager();
//         let mut semaphore = Semaphore::new(2, Rc::clone(&tm));
//         let thread1 = Rc::new(RefCell::new(Thread::new("test_semaphore_1")));
//         let thread2 = Rc::new(RefCell::new(Thread::new("test_semaphore_2")));
//         let thread3 = Rc::new(RefCell::new(Thread::new("test_semaphore_3")));

//         let mut borrow_tm = tm.borrow_mut();
//         let scheduler = &mut borrow_tm.g_scheduler;
//         scheduler.ready_to_run(Rc::clone(&thread1));
//         scheduler.ready_to_run(Rc::clone(&thread2));
//         scheduler.ready_to_run(Rc::clone(&thread3));
//         // P
//         borrow_tm.set_g_current_thread(Some(Rc::clone(&thread1)));
//         semaphore.p(thread1, Rc::clone(&system));
//         assert_eq!(semaphore.counter, 1);
//         assert!(semaphore.waiting_queue.is_empty());
        
//         borrow_tm.set_g_current_thread(Some(Rc::clone(&thread2)));
//         semaphore.p(thread2, Rc::clone(&system));
//         assert_eq!(semaphore.counter, 0);
//         assert!(semaphore.waiting_queue.is_empty());

//         borrow_tm.set_g_current_thread(Some(Rc::clone(&thread3)));
//         semaphore.p(thread3, Rc::clone(&system));
//         assert_eq!(semaphore.counter, -1);
//         assert!(semaphore.waiting_queue.iter().count() == 1);

//         // V
//         semaphore.v(Rc::clone(&system));
//         assert_eq!(semaphore.counter, 0);
//         assert!(semaphore.waiting_queue.is_empty());

//         semaphore.v(Rc::clone(&system));
//         assert_eq!(semaphore.counter, 1);
//         assert!(semaphore.waiting_queue.is_empty());

//         semaphore.v(Rc::clone(&system));
//         assert_eq!(semaphore.counter, 2);
//         assert!(semaphore.waiting_queue.is_empty());
//     }



//     #[test]
//     #[ignore]
//     fn test_lock_simple() {
//         let system = init_system!();
//         let sys = system.borrow_mut();
//         let tm = sys.get_thread_manager();
//         let thread = Rc::new(RefCell::new(Thread::new("test_lock")));
//         tm.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread)));
//         let mut lock = Lock::new(Rc::clone(&tm));

//         assert!(lock.free);
//         lock.acquire(Some(Rc::clone(&thread)), Rc::clone(&system));
//         assert!(lock.held_by_current_thread(Rc::clone(&thread)));

//         assert!(!lock.free);
//         lock.release(Rc::clone(&system), Rc::clone(&thread));
//         assert!(!lock.held_by_current_thread(thread));
//         assert!(lock.free);
//     }

//     #[test]
//     #[ignore]
//     fn test_lock_multiple() {
//         let system = init_system!();
//         let thread1 = Rc::new(RefCell::new(Thread::new("test_lock1")));
//         let thread2 = Rc::new(RefCell::new(Thread::new("test_lock2")));
//         let thread3 = Rc::new(RefCell::new(Thread::new("test_lock3")));

//         let tm = system.borrow_mut().get_thread_manager();
//         tm.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread1)));
//         let mut lock = Lock::new(Rc::clone(&tm));

//         assert!(lock.free);
//         lock.acquire(Some(Rc::clone(&thread1)), Rc::clone(&system));
//         assert!(lock.held_by_current_thread(Rc::clone(&thread1)));
//         assert!(!lock.free);

//         tm.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread2)));
//         lock.acquire(Some(Rc::clone(&thread2)), Rc::clone(&system));
//         tm.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread1)));

        
//         assert!(lock.held_by_current_thread(Rc::clone(&thread1)));
//         assert!(lock.waiting_queue.iter().count() == 1);
//         assert!(!lock.free);

//         lock.release(Rc::clone(&system), Rc::clone(&thread1));
//         assert!(!lock.held_by_current_thread(thread1));
//         assert!(lock.held_by_current_thread(Rc::clone(&thread2)));
//         assert!(!lock.free);

//         tm.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread2)));


//         lock.release(Rc::clone(&system), Rc::clone(&thread2));
//         assert!(!lock.held_by_current_thread(thread2));
//         assert!(lock.free);
//     }
// }