//                              -*- Mode: CFA -*-
//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// monitor_desc.c --
//
// Author           : Thierry Delisle
// Created On       : Thd Feb 23 12:27:26 2017
// Last Modified By : Thierry Delisle
// Last Modified On : --
// Update Count     : 0
//

#include "monitor"

#include <stdlib>

#include "kernel_private.h"
#include "libhdr.h"

//-----------------------------------------------------------------------------
// Forward declarations
static inline void set_owner( monitor_desc * this, thread_desc * owner );
static inline thread_desc * next_thread( monitor_desc * this );

static inline void lock_all( spinlock ** locks, unsigned short count );
static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count );
static inline void unlock_all( spinlock ** locks, unsigned short count );
static inline void unlock_all( monitor_desc ** locks, unsigned short count );

static inline void save_recursion   ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count );
static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count );

static inline thread_desc * check_condition( __condition_criterion_t * );
static inline void brand_condition( condition * );
static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val );

//-----------------------------------------------------------------------------
// Enter/Leave routines


extern "C" {
	void __enter_monitor_desc(monitor_desc * this) {
		lock( &this->lock );
		thread_desc * thrd = this_thread();

		LIB_DEBUG_PRINT_SAFE("%p Entering %p (o: %p, r: %i)\n", thrd, this, this->owner, this->recursion);

		if( !this->owner ) {
			//No one has the monitor, just take it
			set_owner( this, thrd );
		}
		else if( this->owner == thrd) {
			//We already have the monitor, just not how many times we took it
			assert( this->recursion > 0 );
			this->recursion += 1;
		}
		else {
			//Some one else has the monitor, wait in line for it
			append( &this->entry_queue, thrd );
			LIB_DEBUG_PRINT_SAFE("%p Blocking on entry\n", thrd);
			ScheduleInternal( &this->lock );

			//ScheduleInternal will unlock spinlock, no need to unlock ourselves
			return; 
		}

		unlock( &this->lock );
		return;
	}

	// leave pseudo code :
	//	TODO
	void __leave_monitor_desc(monitor_desc * this) {
		lock( &this->lock );

		thread_desc * thrd = this_thread();

		LIB_DEBUG_PRINT_SAFE("%p Leaving %p (o: %p, r: %i)\n", thrd, this, this->owner, this->recursion);
		assertf( thrd == this->owner, "Expected owner to be %p, got %p (r: %i)", thrd, this->owner, this->recursion );

		//Leaving a recursion level, decrement the counter
		this->recursion -= 1;

		//If we haven't left the last level of recursion
		//it means we don't need to do anything
		if( this->recursion != 0) {
			unlock( &this->lock );
			return;
		}

		thread_desc * new_owner = next_thread( this );

		//We can now let other threads in safely
		unlock( &this->lock );

		LIB_DEBUG_PRINT_SAFE("Next owner is %p\n", new_owner);

		//We need to wake-up the thread
		ScheduleThread( new_owner );
	}
}

static inline void enter(monitor_desc ** monitors, int count) {
	for(int i = 0; i < count; i++) {
		__enter_monitor_desc( monitors[i] );
	}
}

static inline void leave(monitor_desc ** monitors, int count) {
	for(int i = count - 1; i >= 0; i--) {
		__leave_monitor_desc( monitors[i] );
	}
}

void ?{}( monitor_guard_t * this, monitor_desc ** m, int count ) {
	this->m = m;
	this->count = count;
	qsort(this->m, count);
	enter( this->m, this->count );

	this->prev_mntrs = this_thread()->current_monitors;
	this->prev_count = this_thread()->current_monitor_count;

	this_thread()->current_monitors      = m;
	this_thread()->current_monitor_count = count;
}

void ^?{}( monitor_guard_t * this ) {
	leave( this->m, this->count );

	this_thread()->current_monitors      = this->prev_mntrs;
	this_thread()->current_monitor_count = this->prev_count;
}

void ?{}(__condition_node_t * this, thread_desc * waiting_thread, unsigned short count, uintptr_t user_info ) {
	this->waiting_thread = waiting_thread;
	this->count = count;
	this->next = NULL;
	this->user_info = user_info;
}

void ?{}(__condition_criterion_t * this ) {
	this->ready  = false;
	this->target = NULL;
	this->owner  = NULL;
	this->next   = NULL;
}

void ?{}(__condition_criterion_t * this, monitor_desc * target, __condition_node_t * owner ) {
	this->ready  = false;
	this->target = target;
	this->owner  = owner;
	this->next   = NULL;
}

//-----------------------------------------------------------------------------
// Internal scheduling
void wait( condition * this, uintptr_t user_info = 0 ) {
	LIB_DEBUG_PRINT_SAFE("Waiting\n");

	brand_condition( this );

	//Check that everything is as expected
	assertf( this->monitors != NULL, "Waiting with no monitors (%p)", this->monitors );
	assertf( this->monitor_count != 0, "Waiting with 0 monitors (%i)", this->monitor_count );
	assertf( this->monitor_count < 32u, "Excessive monitor count (%i)", this->monitor_count );

	unsigned short count = this->monitor_count;
	unsigned int recursions[ count ];		//Save the current recursion levels to restore them later
	spinlock *   locks     [ count ];		//We need to pass-in an array of locks to ScheduleInternal

	LIB_DEBUG_PRINT_SAFE("count %i\n", count);

	__condition_node_t waiter = { this_thread(), count, user_info };

	__condition_criterion_t criteria[count];
	for(int i = 0; i < count; i++) {
		(&criteria[i]){ this->monitors[i], &waiter };
		LIB_DEBUG_PRINT_SAFE( "Criterion %p\n", &criteria[i] );
	}

	waiter.criteria = criteria;
	append( &this->blocked, &waiter );

	lock_all( this->monitors, locks, count );
	save_recursion( this->monitors, recursions, count );
	//DON'T unlock, ask the kernel to do it

	//Find the next thread(s) to run
	unsigned short thread_count = 0;
	thread_desc * threads[ count ];
	for(int i = 0; i < count; i++) {
		threads[i] = 0;
	}

	for( int i = 0; i < count; i++) {
		thread_desc * new_owner = next_thread( this->monitors[i] );
		thread_count = insert_unique( threads, thread_count, new_owner );
	}

	LIB_DEBUG_PRINT_SAFE("Will unblock: ");
	for(int i = 0; i < thread_count; i++) {
		LIB_DEBUG_PRINT_SAFE("%p ", threads[i]);
	}
	LIB_DEBUG_PRINT_SAFE("\n");

	// Everything is ready to go to sleep
	ScheduleInternal( locks, count, threads, thread_count );


	//WE WOKE UP


	//We are back, restore the owners and recursions
	lock_all( locks, count );
	restore_recursion( this->monitors, recursions, count );
	unlock_all( locks, count );
}

bool signal( condition * this ) {
	if( is_empty( this ) ) {
		LIB_DEBUG_PRINT_SAFE("Nothing to signal\n");
		return false;
	}

	//Check that everything is as expected
	assert( this->monitors );
	assert( this->monitor_count != 0 );

	unsigned short count = this->monitor_count;
	
	//Some more checking in debug
	LIB_DEBUG_DO(
		thread_desc * this_thrd = this_thread();
		if ( this->monitor_count != this_thrd->current_monitor_count ) {
			abortf( "Signal on condition %p made with different number of monitor(s), expected %i got %i", this, this->monitor_count, this_thrd->current_monitor_count );
		} // if

		for(int i = 0; i < this->monitor_count; i++) {
			if ( this->monitors[i] != this_thrd->current_monitors[i] ) {
				abortf( "Signal on condition %p made with different monitor, expected %p got %i", this, this->monitors[i], this_thrd->current_monitors[i] );
			} // if
		}
	);

	//Lock all the monitors
	lock_all( this->monitors, NULL, count );
	LIB_DEBUG_PRINT_SAFE("Signalling");

	//Pop the head of the waiting queue
	__condition_node_t * node = pop_head( &this->blocked );

	//Add the thread to the proper AS stack
	for(int i = 0; i < count; i++) {
		__condition_criterion_t * crit = &node->criteria[i];
		LIB_DEBUG_PRINT_SAFE(" %p", crit->target);
		assert( !crit->ready );
		push( &crit->target->signal_stack, crit );
	}

	LIB_DEBUG_PRINT_SAFE("\n");

	//Release
	unlock_all( this->monitors, count );

	return true;
}

bool signal_block( condition * this ) {
	if( !this->blocked.head ) {
		LIB_DEBUG_PRINT_SAFE("Nothing to signal\n");
		return false;
	}

	//Check that everything is as expected
	assertf( this->monitors != NULL, "Waiting with no monitors (%p)", this->monitors );
	assertf( this->monitor_count != 0, "Waiting with 0 monitors (%i)", this->monitor_count );

	unsigned short count = this->monitor_count;
	unsigned int recursions[ count ];		//Save the current recursion levels to restore them later
	spinlock *   locks     [ count ];		//We need to pass-in an array of locks to ScheduleInternal

	lock_all( this->monitors, locks, count );

	//create creteria
	__condition_node_t waiter = { this_thread(), count, 0 };

	__condition_criterion_t criteria[count];
	for(int i = 0; i < count; i++) {
		(&criteria[i]){ this->monitors[i], &waiter };
		LIB_DEBUG_PRINT_SAFE( "Criterion %p\n", &criteria[i] );
		push( &criteria[i].target->signal_stack, &criteria[i] );
	}

	waiter.criteria = criteria;

	//save contexts
	save_recursion( this->monitors, recursions, count );

	//Find the thread to run
	thread_desc * signallee = pop_head( &this->blocked )->waiting_thread;
	for(int i = 0; i < count; i++) {
		set_owner( this->monitors[i], signallee );
	}

	LIB_DEBUG_PRINT_SAFE( "Waiting on signal block\n" );

	//Everything is ready to go to sleep
	ScheduleInternal( locks, count, &signallee, 1 );




	LIB_DEBUG_PRINT_SAFE( "Back from signal block\n" );

	//We are back, restore the owners and recursions
	lock_all( locks, count );
	restore_recursion( this->monitors, recursions, count );
	unlock_all( locks, count );

	return true;
}

uintptr_t front( condition * this ) {
	LIB_DEBUG_DO(
		if( is_empty(this) ) {
			abortf( "Attempt to access user data on an empty condition.\n"
                    "Possible cause is not checking if the condition is empty before reading stored data." );
		}
	);
	return this->blocked.head->user_info;
}

//-----------------------------------------------------------------------------
// Internal scheduling
void __accept_internal( unsigned short count, __acceptable_t * acceptables, void (*func)(void) ) {
	// thread_desc * this = this_thread();

	// unsigned short count = this->current_monitor_count;
	// unsigned int recursions[ count ];		//Save the current recursion levels to restore them later
	// spinlock *   locks     [ count ];		//We need to pass-in an array of locks to ScheduleInternal

	// lock_all( this->current_monitors, locks, count );





	// // // Everything is ready to go to sleep
	// // ScheduleInternal( locks, count, threads, thread_count );


	// //WE WOKE UP


	// //We are back, restore the owners and recursions
	// lock_all( locks, count );
	// restore_recursion( this->monitors, recursions, count );
	// unlock_all( locks, count );
}

//-----------------------------------------------------------------------------
// Utilities

static inline void set_owner( monitor_desc * this, thread_desc * owner ) {
	//Pass the monitor appropriately
	this->owner = owner;

	//We are passing the monitor to someone else, which means recursion level is not 0
	this->recursion = owner ? 1 : 0;
}

static inline thread_desc * next_thread( monitor_desc * this ) {
	//Check the signaller stack
	__condition_criterion_t * urgent = pop( &this->signal_stack );
	if( urgent ) {
		//The signaller stack is not empty,
		//regardless of if we are ready to baton pass,
		//we need to set the monitor as in use
		set_owner( this,  urgent->owner->waiting_thread );

		return check_condition( urgent );
	}

	// No signaller thread
	// Get the next thread in the entry_queue
	thread_desc * new_owner = pop_head( &this->entry_queue );
	set_owner( this, new_owner );

	return new_owner;
}

static inline void lock_all( spinlock ** locks, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		lock( locks[i] );
	}
}

static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		spinlock * l = &source[i]->lock;
		lock( l );
		if(locks) locks[i] = l;
	}
}

static inline void unlock_all( spinlock ** locks, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		unlock( locks[i] );
	}
}

static inline void unlock_all( monitor_desc ** locks, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		unlock( &locks[i]->lock );
	}
}


static inline void save_recursion   ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		recursions[i] = ctx[i]->recursion;
	}
}

static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count ) {
	for( int i = 0; i < count; i++ ) {
		ctx[i]->recursion = recursions[i];
	}
}

// Function has 2 different behavior
// 1 - Marks a monitors as being ready to run
// 2 - Checks if all the monitors are ready to run
//     if so return the thread to run
static inline thread_desc * check_condition( __condition_criterion_t * target ) {
	__condition_node_t * node = target->owner;
	unsigned short count = node->count;
	__condition_criterion_t * criteria = node->criteria;

	bool ready2run = true;

	for(	int i = 0; i < count; i++ ) {

		LIB_DEBUG_PRINT_SAFE( "Checking %p for %p\n", &criteria[i], target );
		if( &criteria[i] == target ) {
			criteria[i].ready = true;
			LIB_DEBUG_PRINT_SAFE( "True\n" );
		}

		ready2run = criteria[i].ready && ready2run;
	}

	LIB_DEBUG_PRINT_SAFE( "Runing %i\n", ready2run );
	return ready2run ? node->waiting_thread : NULL;
}

static inline void brand_condition( condition * this ) {
	thread_desc * thrd = this_thread();
	if( !this->monitors ) {
		LIB_DEBUG_PRINT_SAFE("Branding\n");
		assertf( thrd->current_monitors != NULL, "No current monitor to brand condition", thrd->current_monitors );
		this->monitor_count = thrd->current_monitor_count;

		this->monitors = malloc( this->monitor_count * sizeof( *this->monitors ) );
		for( int i = 0; i < this->monitor_count; i++ ) {
			this->monitors[i] = thrd->current_monitors[i];
		}
	}
}

static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val ) {
	if( !val ) return end;

	for(int i = 0; i <= end; i++) {
		if( thrds[i] == val ) return end;
	}

	thrds[end] = val;
	return end + 1;
}

void ?{}( __condition_blocked_queue_t * this ) {
	this->head = NULL;
	this->tail = &this->head;
}

void append( __condition_blocked_queue_t * this, __condition_node_t * c ) {
	assert(this->tail != NULL);
	*this->tail = c;
	this->tail = &c->next;
}

__condition_node_t * pop_head( __condition_blocked_queue_t * this ) {
	__condition_node_t * head = this->head;
	if( head ) {
		this->head = head->next;
		if( !head->next ) {
			this->tail = &this->head;
		}
		head->next = NULL;
	}
	return head;
}