#include <thread>

#include "blockingconcurrentqueue.h"

#include "ultra64.h"
#include "ultramodern.hpp"
#include "recomp.h"

struct QueuedMessage {
    PTR(OSMesgQueue) mq;
    OSMesg mesg;
    bool jam;
};

static moodycamel::BlockingConcurrentQueue<QueuedMessage> external_messages {};

void enqueue_external_message(PTR(OSMesgQueue) mq, OSMesg msg, bool jam) {
    external_messages.enqueue({mq, msg, jam});
}

bool do_send(RDRAM_ARG PTR(OSMesgQueue) mq_, OSMesg msg, bool jam, bool block);

void dequeue_external_messages(RDRAM_ARG1) {
    QueuedMessage to_send;
    while (external_messages.try_dequeue(to_send)) {
        do_send(PASS_RDRAM to_send.mq, to_send.mesg, to_send.jam, false);
    }
}

void ultramodern::wait_for_external_message(RDRAM_ARG1) {
    QueuedMessage to_send;
    external_messages.wait_dequeue(to_send);
    do_send(PASS_RDRAM to_send.mq, to_send.mesg, to_send.jam, false);
}

extern "C" void osCreateMesgQueue(RDRAM_ARG PTR(OSMesgQueue) mq_, PTR(OSMesg) msg, s32 count) {
    OSMesgQueue *mq = TO_PTR(OSMesgQueue, mq_);
    mq->blocked_on_recv = NULLPTR;
    mq->blocked_on_send = NULLPTR;
    mq->msgCount = count;
    mq->msg = msg;
    mq->validCount = 0;
    mq->first = 0;
}

s32 MQ_GET_COUNT(OSMesgQueue *mq) {
    return mq->validCount;
}

s32 MQ_IS_EMPTY(OSMesgQueue *mq) {
    return mq->validCount == 0;
}

s32 MQ_IS_FULL(OSMesgQueue* mq) {
    return MQ_GET_COUNT(mq) >= mq->msgCount;
}

bool do_send(RDRAM_ARG PTR(OSMesgQueue) mq_, OSMesg msg, bool jam, bool block) {
    OSMesgQueue* mq = TO_PTR(OSMesgQueue, mq_);
    if (!block) {
        // If non-blocking, fail if the queue is full.
        if (MQ_IS_FULL(mq)) {
            return false;
        }
    }
    else {
        // Otherwise, yield this thread until the queue has room.
        while (MQ_IS_FULL(mq)) {
            debug_printf("[Message Queue] Thread %d is blocked on send\n", TO_PTR(OSThread, ultramodern::this_thread())->id);
            ultramodern::thread_queue_insert(PASS_RDRAM GET_MEMBER(OSMesgQueue, mq_, blocked_on_send), ultramodern::this_thread());
            ultramodern::run_next_thread_and_wait(PASS_RDRAM1);
        }
    }
    
    if (jam) {
        // Jams insert at the head of the message queue's buffer.
        mq->first = (mq->first + mq->msgCount - 1) % mq->msgCount;
        TO_PTR(OSMesg, mq->msg)[mq->first] = msg;
        mq->validCount++;
    }
    else {
        // Sends insert at the tail of the message queue's buffer.
        s32 last = (mq->first + mq->validCount) % mq->msgCount;
        TO_PTR(OSMesg, mq->msg)[last] = msg;
        mq->validCount++;
    }

    // If any threads were blocked on receiving from this message queue, pop the first one and schedule it.
    PTR(PTR(OSThread)) blocked_queue = GET_MEMBER(OSMesgQueue, mq_, blocked_on_recv);
    if (!ultramodern::thread_queue_empty(PASS_RDRAM blocked_queue)) {
        ultramodern::schedule_running_thread(PASS_RDRAM ultramodern::thread_queue_pop(PASS_RDRAM blocked_queue));
    }
    
    return true;
}

bool do_recv(RDRAM_ARG PTR(OSMesgQueue) mq_, PTR(OSMesg) msg_, bool block) {
    OSMesgQueue* mq = TO_PTR(OSMesgQueue, mq_);
    if (!block) {
        // If non-blocking, fail if the queue is empty
        if (MQ_IS_EMPTY(mq)) {
            return false;
        }
    } else {
        // Otherwise, yield this thread in a loop until the queue is no longer full
        while (MQ_IS_EMPTY(mq)) {
            debug_printf("[Message Queue] Thread %d is blocked on receive\n", TO_PTR(OSThread, ultramodern::this_thread())->id);
            ultramodern::thread_queue_insert(PASS_RDRAM GET_MEMBER(OSMesgQueue, mq_, blocked_on_recv), ultramodern::this_thread());
            ultramodern::run_next_thread_and_wait(PASS_RDRAM1);
        }
    }

    if (msg_ != NULLPTR) {
        *TO_PTR(OSMesg, msg_) = TO_PTR(OSMesg, mq->msg)[mq->first];
    }
    
    mq->first = (mq->first + 1) % mq->msgCount;
    mq->validCount--;

    // If any threads were blocked on sending to this message queue, pop the first one and schedule it.
    PTR(PTR(OSThread)) blocked_queue = GET_MEMBER(OSMesgQueue, mq_, blocked_on_send);
    if (!ultramodern::thread_queue_empty(PASS_RDRAM blocked_queue)) {
        ultramodern::schedule_running_thread(PASS_RDRAM ultramodern::thread_queue_pop(PASS_RDRAM blocked_queue));
    }

    return true;
}

extern "C" s32 osSendMesg(RDRAM_ARG PTR(OSMesgQueue) mq_, OSMesg msg, s32 flags) {
    OSMesgQueue *mq = TO_PTR(OSMesgQueue, mq_);
    bool jam = false;
    
    // Don't directly send to the message queue if this isn't a game thread to avoid contention.
    if (!ultramodern::is_game_thread()) {
        enqueue_external_message(mq_, msg, jam);
        return 0;
    }
    
    // Handle any messages that have been received from an external thread.
    dequeue_external_messages(PASS_RDRAM1);

    // Try to send the message.
    bool sent = do_send(PASS_RDRAM mq_, msg, jam, flags == OS_MESG_BLOCK);
    
    // Check the queue to see if this thread should swap execution to another.
    ultramodern::check_running_queue(PASS_RDRAM1);

    return sent ? 0 : -1;
}

extern "C" s32 osJamMesg(RDRAM_ARG PTR(OSMesgQueue) mq_, OSMesg msg, s32 flags) {
    OSMesgQueue *mq = TO_PTR(OSMesgQueue, mq_);
    bool jam = true;
    
    // Don't directly send to the message queue if this isn't a game thread to avoid contention.
    if (!ultramodern::is_game_thread()) {
        enqueue_external_message(mq_, msg, jam);
        return 0;
    }
    
    // Handle any messages that have been received from an external thread.
    dequeue_external_messages(PASS_RDRAM1);

    // Try to send the message.
    bool sent = do_send(PASS_RDRAM mq_, msg, jam, flags == OS_MESG_BLOCK);
    
    // Check the queue to see if this thread should swap execution to another.
    ultramodern::check_running_queue(PASS_RDRAM1);

    return sent ? 0 : -1;
}

extern "C" s32 osRecvMesg(RDRAM_ARG PTR(OSMesgQueue) mq_, PTR(OSMesg) msg_, s32 flags) {
    OSMesgQueue *mq = TO_PTR(OSMesgQueue, mq_);
    
    assert(ultramodern::is_game_thread() && "RecvMesg not allowed outside of game threads.");
    
    // Handle any messages that have been received from an external thread.
    dequeue_external_messages(PASS_RDRAM1);

    // Try to receive a message.
    bool received = do_recv(PASS_RDRAM mq_, msg_, flags == OS_MESG_BLOCK);
    
    // Check the queue to see if this thread should swap execution to another.
    ultramodern::check_running_queue(PASS_RDRAM1);

    return received ? 0 : -1;
}