#pragma once

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

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

// hybrid data structure. Copies until buffer is full and then allocates for intrusive list
struct copy_queue {
    dlist( request ) list;
    request * buffer;
    size_t count, buffer_size, index;
};
static inline void ?{}( copy_queue & this ) {}
static inline void ?{}( copy_queue & this, size_t buf_size ) with(this) { 
    list{};
    buffer_size = buf_size;
    buffer = aalloc( buffer_size );
    count = 0;
    index = 0;
}
static inline void ^?{}( copy_queue & this ) with(this) { adelete(buffer); }

static inline void insert( copy_queue & this, request & elem ) with(this) {
    if ( count < buffer_size ) { // fast path ( no alloc )
        buffer[count]{ elem };
        count++;
        return;
    }
    request * new_elem = alloc();
    (*new_elem){ elem };
    insert_last( list, *new_elem );
}

// once you start removing you need to remove all elements
// it is not supported to call insert() before the list is fully empty
// should_delete is an output param
static inline request & remove( copy_queue & this, bool & should_delete ) with(this) {
    if ( count > 0 ) {
        count--;
        should_delete = false;
        size_t old_idx = index;
        index = count == 0 ? 0 : index + 1;
        return buffer[old_idx];
    }
    should_delete = true;
    return try_pop_front( list );
}

static inline bool isEmpty( copy_queue & this ) with(this) { return count == 0 && list`isEmpty; }

static size_t __buffer_size = 10; // C_TODO: rework this to be passed from executor through ctors (no need for global)
struct work_queue {
    futex_mutex mutex_lock; 
    copy_queue * c_queue; // C_TODO: try putting this on the stack with ptr juggling
}; // work_queue
static inline void ?{}( work_queue & this ) with(this) { 
    c_queue = alloc();
    (*c_queue){ __buffer_size }; // C_TODO: support passing copy buff size as arg to executor
}
static inline void ^?{}( work_queue & this ) with(this) { delete( c_queue ); }

static inline void insert( work_queue & this, request & elem ) with(this) {
    lock( mutex_lock );
    insert( *c_queue, elem );
    unlock( mutex_lock );
} // insert

static inline void transfer( work_queue & this, copy_queue ** transfer_to ) with(this) {
    lock( mutex_lock );
    // swap copy queue ptrs
    copy_queue * temp = *transfer_to;
    *transfer_to = c_queue;
    c_queue = temp;
    unlock( mutex_lock );
} // transfer

thread worker {
    work_queue * request_queues;
    copy_queue * 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 = alloc();
    (*this.current_queue){ __buffer_size };
    this.start = start;
    this.range = range;
}
static inline void ^?{}( worker & mutex this ) with(this) { delete( current_queue ); }

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, size_t buf_size ) with(this) {
    if ( nrqueues < nworkers ) abort( "nrqueues needs to be >= nworkers\n" );
    __buffer_size = buf_size;
    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, bool seperate_clus ) { this{ nprocessors, nworkers, nrqueues, seperate_clus, __buffer_size }; }
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

    adelete( workers );
    adelete( request_queues );
    adelete( 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
};

static inline 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 );
}
static inline 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
};

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

static inline 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) {
    bool should_delete;
    Exit:
    for ( unsigned int i = 0;; i = (i + 1) % range ) { // cycle through set of request buffers
        // C_TODO: potentially check queue count instead of immediately trying to transfer
        transfer( request_queues[i + start], &current_queue );
        while ( ! isEmpty( *current_queue ) ) {
            &req = &remove( *current_queue, should_delete );
            if ( !&req ) continue; // possibly add some work stealing/idle sleep here
            if ( req.stop ) break Exit;
            deliver_request( req );

            if ( should_delete ) 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 == 1 ? 1 : 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;
}