//
// Cforall Version 1.0.0 Copyright (C) 2021 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// locks.hfa -- PUBLIC
// Runtime locks that used with the runtime thread system.
//
// Author           : Colby Alexander Parsons
// Created On       : Thu Jan 21 19:46:50 2021
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#pragma once

#include <stdbool.h>
#include <stdio.h>

#include "bits/weakso_locks.hfa"
#include "containers/queueLockFree.hfa"
#include "containers/list.hfa"

#include "limits.hfa"
#include "thread.hfa"

#include "time_t.hfa"
#include "time.hfa"

//-----------------------------------------------------------------------------
// Semaphore
struct semaphore {
	__spinlock_t lock;
	int count;
	__queue_t(thread$) waiting;
};

void  ?{}(semaphore & this, int count = 1);
void ^?{}(semaphore & this);
bool   P (semaphore & this);
bool   V (semaphore & this);
bool   V (semaphore & this, unsigned count);
thread$ * V (semaphore & this, bool );

//----------
struct single_acquisition_lock {
	inline blocking_lock;
};

static inline void  ?{}( single_acquisition_lock & this ) {((blocking_lock &)this){ false, false };}
static inline void ^?{}( single_acquisition_lock & this ) {}
static inline void   lock     ( single_acquisition_lock & this ) { lock    ( (blocking_lock &)this ); }
static inline bool   try_lock ( single_acquisition_lock & this ) { return try_lock( (blocking_lock &)this ); }
static inline void   unlock   ( single_acquisition_lock & this ) { unlock  ( (blocking_lock &)this ); }
static inline size_t on_wait  ( single_acquisition_lock & this ) { return on_wait ( (blocking_lock &)this ); }
static inline void   on_wakeup( single_acquisition_lock & this, size_t v ) { on_wakeup ( (blocking_lock &)this, v ); }
static inline void   on_notify( single_acquisition_lock & this, struct thread$ * t ) { on_notify( (blocking_lock &)this, t ); }

//----------
struct owner_lock {
	inline blocking_lock;
};

static inline void  ?{}( owner_lock & this ) {((blocking_lock &)this){ true, true };}
static inline void ^?{}( owner_lock & this ) {}
static inline void   lock     ( owner_lock & this ) { lock    ( (blocking_lock &)this ); }
static inline bool   try_lock ( owner_lock & this ) { return try_lock( (blocking_lock &)this ); }
static inline void   unlock   ( owner_lock & this ) { unlock  ( (blocking_lock &)this ); }
static inline size_t on_wait  ( owner_lock & this ) { return on_wait ( (blocking_lock &)this ); }
static inline void   on_wakeup( owner_lock & this, size_t v ) { on_wakeup ( (blocking_lock &)this, v ); }
static inline void   on_notify( owner_lock & this, struct thread$ * t ) { on_notify( (blocking_lock &)this, t ); }

//-----------------------------------------------------------------------------
// MCS Lock
struct mcs_node {
	mcs_node * volatile next;
	single_sem sem;
};

static inline void ?{}(mcs_node & this) { this.next = 0p; }

static inline mcs_node * volatile & ?`next ( mcs_node * node ) {
	return node->next;
}

struct mcs_lock {
	mcs_queue(mcs_node) queue;
};

static inline void lock(mcs_lock & l, mcs_node & n) {
	if(push(l.queue, &n))
		wait(n.sem);
}

static inline void unlock(mcs_lock & l, mcs_node & n) {
	mcs_node * next = advance(l.queue, &n);
	if(next) post(next->sem);
}

//-----------------------------------------------------------------------------
// Linear backoff Spinlock
struct linear_backoff_then_block_lock {
	// Spin lock used for mutual exclusion
	__spinlock_t spinlock;

	// Current thread owning the lock
	struct thread$ * owner;

	// List of blocked threads
	dlist( thread$ ) blocked_threads;

	// Used for comparing and exchanging
	volatile size_t lock_value;

	// used for linear backoff spinning
	int spin_start;
	int spin_end;
	int spin_count;

	// after unsuccessful linear backoff yield this many times
	int yield_count;
};

static inline void  ?{}( linear_backoff_then_block_lock & this, int spin_start, int spin_end, int spin_count, int yield_count ) {
	this.spinlock{};
	this.blocked_threads{};
	this.lock_value = 0;
	this.spin_start = spin_start;
	this.spin_end = spin_end;
	this.spin_count = spin_count;
	this.yield_count = yield_count;
}
static inline void  ?{}( linear_backoff_then_block_lock & this ) { this{4, 1024, 16, 0}; }
static inline void ^?{}( linear_backoff_then_block_lock & this ) {}
static inline void ?{}( linear_backoff_then_block_lock & this, linear_backoff_then_block_lock this2 ) = void;
static inline void ?=?( linear_backoff_then_block_lock & this, linear_backoff_then_block_lock this2 ) = void;

static inline bool internal_try_lock(linear_backoff_then_block_lock & this, size_t & compare_val) with(this) {
	if (__atomic_compare_exchange_n(&lock_value, &compare_val, 1, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
		owner = active_thread();
		return true;
	}
	return false;
}

static inline bool try_lock(linear_backoff_then_block_lock & this) { size_t compare_val = 0; return internal_try_lock(this, compare_val); }

static inline bool try_lock_contention(linear_backoff_then_block_lock & this) with(this) {
	if (__atomic_exchange_n(&lock_value, 2, __ATOMIC_ACQUIRE) == 0) {
		owner = active_thread();
		return true;
	}
	return false;
}

static inline bool block(linear_backoff_then_block_lock & this) with(this) {
	lock( spinlock __cfaabi_dbg_ctx2 );
	if (lock_value != 2) {
		unlock( spinlock );
		return true;
	}
	insert_last( blocked_threads, *active_thread() );
	unlock( spinlock );
	park( );
	return true;
}

static inline void lock(linear_backoff_then_block_lock & this) with(this) {
	// if owner just return
	if (active_thread() == owner) return;
	size_t compare_val = 0;
	int spin = spin_start;
	// linear backoff
	for( ;; ) {
		compare_val = 0;
		if (internal_try_lock(this, compare_val)) return;
		if (2 == compare_val) break;
		for (int i = 0; i < spin; i++) Pause();
		if (spin >= spin_end) break;
		spin += spin;
	}

	if(2 != compare_val && try_lock_contention(this)) return;
	// block until signalled
	while (block(this)) if(try_lock_contention(this)) return;
}

static inline void unlock(linear_backoff_then_block_lock & this) with(this) {
	verify(lock_value > 0);
    owner = 0p;
    if (__atomic_exchange_n(&lock_value, 0, __ATOMIC_RELEASE) == 1) return;
	lock( spinlock __cfaabi_dbg_ctx2 );
	thread$ * t = &try_pop_front( blocked_threads );
	unlock( spinlock );
	unpark( t );
}

static inline void on_notify(linear_backoff_then_block_lock & this, struct thread$ * t ) { unpark(t); }
static inline size_t on_wait(linear_backoff_then_block_lock & this) { unlock(this); return 0; }
static inline void on_wakeup(linear_backoff_then_block_lock & this, size_t recursion ) { lock(this); }

//-----------------------------------------------------------------------------
// Fast Block Lock

// High efficiency minimal blocking lock
// - No reacquire for cond var
// - No recursive acquisition
// - No ownership
struct fast_block_lock {
	// Spin lock used for mutual exclusion
	__spinlock_t lock;

	// List of blocked threads
	dlist( thread$ ) blocked_threads;

	bool held:1;
};

static inline void  ?{}( fast_block_lock & this ) with(this) {
	lock{};
	blocked_threads{};
	held = false;
}
static inline void ^?{}( fast_block_lock & this ) {}
static inline void ?{}( fast_block_lock & this, fast_block_lock this2 ) = void;
static inline void ?=?( fast_block_lock & this, fast_block_lock this2 ) = void;

// if this is called recursively IT WILL DEADLOCK!!!!!
static inline void lock(fast_block_lock & this) with(this) {
	lock( lock __cfaabi_dbg_ctx2 );
	if (held) {
		insert_last( blocked_threads, *active_thread() );
		unlock( lock );
		park( );
		return;
	}
	held = true;
	unlock( lock );
}

static inline void unlock(fast_block_lock & this) with(this) {
	lock( lock __cfaabi_dbg_ctx2 );
	/* paranoid */ verifyf( held != false, "Attempt to release lock %p that isn't held", &this );
	thread$ * t = &try_pop_front( blocked_threads );
	held = ( t ? true : false );
	unpark( t );
	unlock( lock );
}

static inline void on_notify(fast_block_lock & this, struct thread$ * t ) { unpark(t); }
static inline size_t on_wait(fast_block_lock & this) { unlock(this); return 0; }
static inline void on_wakeup(fast_block_lock & this, size_t recursion ) { }

//-----------------------------------------------------------------------------
// is_blocking_lock
trait is_blocking_lock(L & | sized(L)) {
	// For synchronization locks to use when acquiring
	void on_notify( L &, struct thread$ * );

	// For synchronization locks to use when releasing
	size_t on_wait( L & );

	// to set recursion count after getting signalled;
	void on_wakeup( L &, size_t recursion );
};

//-----------------------------------------------------------------------------
// // info_thread
// // the info thread is a wrapper around a thread used
// // to store extra data for use in the condition variable
forall(L & | is_blocking_lock(L)) {
	struct info_thread;

	// // for use by sequence
	// info_thread(L) *& Back( info_thread(L) * this );
	// info_thread(L) *& Next( info_thread(L) * this );
}

//-----------------------------------------------------------------------------
// Synchronization Locks
forall(L & | is_blocking_lock(L)) {

	//-----------------------------------------------------------------------------
	// condition_variable

	// The multi-tool condition variable
	// - can pass timeouts to wait for either a signal or timeout
	// - can wait without passing a lock
	// - can have waiters reacquire different locks while waiting on the same cond var
	// - has shadow queue
	// - can be signalled outside of critical sections with no locks held
	struct condition_variable {
		// Spin lock used for mutual exclusion
		__spinlock_t lock;

		// List of blocked threads
		dlist( info_thread(L) ) blocked_threads;

		// Count of current blocked threads
		int count;
	};


	void  ?{}( condition_variable(L) & this );
	void ^?{}( condition_variable(L) & this );

	bool notify_one( condition_variable(L) & this );
	bool notify_all( condition_variable(L) & this );

	uintptr_t front( condition_variable(L) & this );

	bool empty  ( condition_variable(L) & this );
	int  counter( condition_variable(L) & this );

	void wait( condition_variable(L) & this );
	void wait( condition_variable(L) & this, uintptr_t info );
	bool wait( condition_variable(L) & this, Duration duration );
	bool wait( condition_variable(L) & this, uintptr_t info, Duration duration );

	void wait( condition_variable(L) & this, L & l );
	void wait( condition_variable(L) & this, L & l, uintptr_t info );
	bool wait( condition_variable(L) & this, L & l, Duration duration );
	bool wait( condition_variable(L) & this, L & l, uintptr_t info, Duration duration );

	//-----------------------------------------------------------------------------
	// fast_cond_var

	// The trimmed and slim condition variable
	// - no internal lock so you must hold a lock while using this cond var
	// - signalling without holding branded lock is UNSAFE!
	// - only allows usage of one lock, cond var is branded after usage
	struct fast_cond_var {
		// List of blocked threads
		dlist( info_thread(L) ) blocked_threads;

		#ifdef __CFA_DEBUG__
		L * lock_used;
		#endif
	};


	void  ?{}( fast_cond_var(L) & this );
	void ^?{}( fast_cond_var(L) & this );

	bool notify_one( fast_cond_var(L) & this );
	bool notify_all( fast_cond_var(L) & this );

	uintptr_t front( fast_cond_var(L) & this );

	bool empty  ( fast_cond_var(L) & this );

	void wait( fast_cond_var(L) & this, L & l );
	void wait( fast_cond_var(L) & this, L & l, uintptr_t info );
}