#include <locks.hfa>
#include <limits.hfa>
#include <list.hfa>

#ifdef __CFA_DEBUG__
#define CFA_DEBUG( stmt ) stmt
#else
#define CFA_DEBUG( stmt )
#endif // CFA_DEBUG

// Define the default number of processors created in the executor. Must be greater than 0.
#define __DEFAULT_EXECUTOR_PROCESSORS__ 2

// Define the default number of threads created in the executor. Must be greater than 0.
#define __DEFAULT_EXECUTOR_WORKERS__ 2

// Define the default number of executor request-queues (mailboxes) written to by actors and serviced by the
// actor-executor threads. Must be greater than 0.
#define __DEFAULT_EXECUTOR_RQUEUES__ 2

// Define if executor is created in a separate cluster
#define __DEFAULT_EXECUTOR_SEPCLUS__ false

// forward decls
struct actor;
struct message;

enum Allocation { Nodelete, Delete, Destroy, Finished }; // allocation status

typedef Allocation (*__receive_fn)(actor &, message &);
struct request {
    actor * receiver;
    message * msg;
    __receive_fn fn;
    bool stop;
    inline dlink(request);
};
P9_EMBEDDED( request, dlink(request) )

void ?{}( request & this ) { this.stop = true; } // default ctor makes a sentinel
void ?{}( request & this, actor * receiver, message * msg, __receive_fn fn ) {
    this.receiver = receiver;
    this.msg = msg;
    this.fn = fn;
    this.stop = false;
}

struct work_queue {
    futex_mutex mutex_lock; 
    dlist( request ) input;						// unbounded list of work requests
}; // work_queue
void ?{}( work_queue & this ) with(this) { input{}; mutex_lock{}; }

void insert( work_queue & this, request & elem ) with(this) {
    lock( mutex_lock );
    insert_last( input, elem );
    unlock( mutex_lock );
} // insert

void transfer( work_queue & this, dlist(request) & transferTo ) with(this) {
    lock( mutex_lock );

    //C_TODO CHANGE
    // transferTo->transfer( input );              // transfer input to output

    // this is awfully inefficient but Ill use it until transfer is implemented
    request * r;
    while ( ! input`isEmpty ) {
        r = &try_pop_front( input );
        if ( r ) insert_last( transferTo, *r );
    }

    // transfer( input, transferTo );

    unlock( mutex_lock );
} // transfer

thread worker {
    work_queue * request_queues;
    dlist( request ) current_queue;
	request & req;
    unsigned int start, range;
};

static inline void ?{}( worker & this, cluster & clu, work_queue * request_queues, unsigned int start, unsigned int range ) {
    ((thread &)this){ clu };
    this.request_queues = request_queues;
    this.current_queue{};
    this.start = start;
    this.range = range;
}

struct executor {
    cluster * cluster;							    // if workers execute on separate cluster
	processor ** processors;					    // array of virtual processors adding parallelism for workers
	work_queue * request_queues;				    // master list of work request queues
	worker ** workers;								// array of workers executing work requests
	unsigned int nprocessors, nworkers, nrqueues;	// number of processors/threads/request queues
	bool seperate_clus;								// use same or separate cluster for executor
}; // executor

static inline void ?{}( executor & this, unsigned int nprocessors, unsigned int nworkers, unsigned int nrqueues, bool seperate_clus ) with(this) {
    if ( nrqueues < nworkers ) abort( "nrqueues needs to be >= nworkers\n" );
    this.nprocessors = nprocessors;
    this.nworkers = nworkers;
    this.nrqueues = nrqueues;
    this.seperate_clus = seperate_clus;

    if ( seperate_clus ) {
        cluster = alloc();
        (*cluster){};
    } else cluster = active_cluster();

    request_queues = aalloc( nrqueues );
    for ( i; nrqueues )
        request_queues[i]{};
    
    processors = aalloc( nprocessors );
    for ( i; nprocessors ) 
        (*(processors[i] = alloc())){ *cluster };

    workers = alloc( nworkers );
    unsigned int reqPerWorker = nrqueues / nworkers, extras = nrqueues % nworkers;
    for ( unsigned int i = 0, start = 0, range; i < nworkers; i += 1, start += range ) {
        range = reqPerWorker + ( i < extras ? 1 : 0 );
        (*(workers[i] = alloc())){ *cluster, request_queues, start, range };
    } // for
}

static inline void ?{}( executor & this, unsigned int nprocessors, unsigned int nworkers, unsigned int nrqueues ) { this{ nprocessors, nworkers, nrqueues, __DEFAULT_EXECUTOR_SEPCLUS__ }; }
static inline void ?{}( executor & this, unsigned int nprocessors, unsigned int nworkers ) { this{ nprocessors, nworkers, __DEFAULT_EXECUTOR_RQUEUES__ }; }
static inline void ?{}( executor & this, unsigned int nprocessors ) { this{ nprocessors, __DEFAULT_EXECUTOR_WORKERS__ }; }
static inline void ?{}( executor & this ) { this{ __DEFAULT_EXECUTOR_PROCESSORS__ }; }

static inline void ^?{}( executor & this ) with(this) {
    request sentinels[nworkers];
    unsigned int reqPerWorker = nrqueues / nworkers;
    for ( unsigned int i = 0, step = 0; i < nworkers; i += 1, step += reqPerWorker ) {
        insert( request_queues[step], sentinels[i] );		// force eventually termination
    } // for

    for ( i; nworkers )
        delete( workers[i] );

    for ( i; nprocessors ) {
        delete( processors[i] );
    } // for

    delete( workers );
    delete( request_queues );
    delete( processors );
    if ( seperate_clus ) delete( cluster );
}

// this is a static field of executor but have to forward decl for get_next_ticket
static unsigned int __next_ticket = 0; 

static inline unsigned int get_next_ticket( executor & this ) with(this) {
    return __atomic_fetch_add( &__next_ticket, 1, __ATOMIC_SEQ_CST) % nrqueues;
} // tickets

// C_TODO: update globals in this file to be static fields once the project is done
static executor * __actor_executor_ = 0p;
static bool __actor_executor_passed = false;        // was an executor passed to start_actor_system
static unsigned long int __num_actors_;				// number of actor objects in system
static struct thread$ * __actor_executor_thd = 0p;		// used to wake executor after actors finish
struct actor {
    unsigned long int ticket;	        // executor-queue handle to provide FIFO message execution
    Allocation allocation_;			// allocation action
};

void ?{}( actor & this ) {
    // Once an actor is allocated it must be sent a message or the actor system cannot stop. Hence, its receive
    // member must be called to end it
    verifyf( __actor_executor_, "Creating actor before calling start_actor_system()." ); 
    this.allocation_ = Nodelete;
    this.ticket = get_next_ticket( *__actor_executor_ );
    __atomic_fetch_add( &__num_actors_, 1, __ATOMIC_SEQ_CST );
}
void ^?{}( actor & this ) {}

static inline void check_actor( actor & this ) {
    if ( this.allocation_ != Nodelete ) {
        switch( this.allocation_ ) {
            case Delete: delete( &this ); break;
            case Destroy:
                CFA_DEBUG( this.ticket = MAX; );	// mark as terminated
                ^?{}(this);
                break;
            case Finished:
                CFA_DEBUG( this.ticket = MAX; );	// mark as terminated
                break;
            default: ;								// stop warning
        }

        if ( unlikely( __atomic_add_fetch( &__num_actors_, -1, __ATOMIC_SEQ_CST ) == 0 ) ) { // all actors have terminated
            unpark( __actor_executor_thd );
        }
    }
}

struct message {
    Allocation allocation_;			// allocation action
};

void ?{}( message & this ) { this.allocation_ = Nodelete; }
void ?{}( message & this, Allocation allocation ) { this.allocation_ = allocation; }
void ^?{}( message & this ) {}

static inline void check_message( message & this ) {
    switch ( this.allocation_ ) {						// analyze message status
        case Nodelete: break;
        case Delete: delete( &this ); break;
        case Destroy: ^?{}(this); break;
        case Finished: break;
    } // switch
}

void deliver_request( request & this ) {
    Allocation actor_allocation = this.fn( *this.receiver, *this.msg );
    this.receiver->allocation_ = actor_allocation;
    check_actor( *this.receiver );
    check_message( *this.msg );
}

void main( worker & this ) with(this) {
    Exit:
    for ( unsigned int i = 0;; i = (i + 1) % range ) { // cycle through set of request buffers
        transfer( request_queues[i + start], current_queue );
        while ( ! current_queue`isEmpty ) {
            &req = &try_pop_front( current_queue );
            if ( !&req ) continue; // possibly add some work stealing/idle sleep here
            if ( req.stop ) break Exit;
            deliver_request( req );

            delete( &req );
        } // while
    } // for
}

static inline void send( executor & this, request & req, unsigned long int ticket ) with(this) {
    insert( request_queues[ticket], req);
}

static inline void send( actor & this, request & req ) {
    send( *__actor_executor_, req, this.ticket );
}

static inline void start_actor_system( size_t num_thds ) {
    __actor_executor_thd = active_thread();
    __actor_executor_ = alloc();
    (*__actor_executor_){ 0, num_thds, num_thds * 16 };
}

static inline void start_actor_system() { start_actor_system( active_cluster()->procs.total ); }

static inline void start_actor_system( executor & this ) {
    __actor_executor_thd = active_thread();
    __actor_executor_ = &this;
    __actor_executor_passed = true;
}

static inline void stop_actor_system() {
    park( ); // will receive signal when actor system is finished

    if ( !__actor_executor_passed ) delete( __actor_executor_ );
    __actor_executor_ = 0p;
    __actor_executor_thd = 0p;
    __next_ticket = 0;
    __actor_executor_passed = false;
}