// GpuNV12SlotPool.cpp — Process-wide singleton, compiled into ANSCV.dll.
//
// ANSCV.dll owns the canonical GpuNV12SlotPool instance.  Other DLLs
// (ANSODEngine, etc.) find it via GetProcAddress at runtime.

#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <windows.h>
#include "GpuNV12SlotPool.h"

#include <cuda_runtime.h>

// ANSCV.dll owns the process-wide singleton.
GpuNV12SlotPool* GpuNV12SlotPool::resolveProcessWide() {
    static GpuNV12SlotPool pool;
    return &pool;
}

// Exported so other DLLs (ANSODEngine, etc.) can find this instance at runtime.
extern "C" __declspec(dllexport)
GpuNV12SlotPool* GpuNV12SlotPool_GetInstance() {
    return &GpuNV12SlotPool::instance();
}

// Transition all COOLING slots past the cooldown threshold to FREE.
// Collects pending AVFrames for the caller to av_frame_free.
void GpuNV12SlotPool::drainCooledSlots_locked() {
    auto now = std::chrono::steady_clock::now();
    auto threshold = std::chrono::milliseconds(SLOT_COOLDOWN_MS);
    for (auto& s : m_slots) {
        if (s->state.load(std::memory_order_acquire) == GpuNV12Slot::STATE_COOLING) {
            if (now - s->cooldownStart >= threshold) {
                s->state.store(GpuNV12Slot::STATE_FREE, std::memory_order_release);
            }
        }
    }
}

// Acquire a free slot matching (gpuIdx, w, h), or allocate a new one.
GpuNV12Slot* GpuNV12SlotPool::acquire(int gpuIdx, int w, int h) {
    std::lock_guard<std::mutex> lock(m_mutex);

    // 1. Drain cooled-down slots to make them available
    drainCooledSlots_locked();

    // 2. Try to find an existing FREE slot that matches the resolution
    for (auto& s : m_slots) {
        if (s->state.load(std::memory_order_acquire) == GpuNV12Slot::STATE_FREE &&
            s->gpuIdx == gpuIdx && s->width == w && s->height == h) {
            s->state.store(GpuNV12Slot::STATE_ACTIVE, std::memory_order_release);
            NV12POOL_DBG("acquire: reuse slot Y=%p UV=%p %dx%d gpu=%d (total=%zu)",
                         s->bufY, s->bufUV, w, h, gpuIdx, m_slots.size());
            return s.get();
        }
    }

    // 3. No matching free slot — allocate a new one if under the limit
    if (static_cast<int>(m_slots.size()) >= GPU_NV12_POOL_MAX_SLOTS) {
        // Always log POOL FULL to DebugView — this is a critical diagnostic.
        {
            char _buf[128];
            snprintf(_buf, sizeof(_buf), "[NV12Pool] POOL FULL (%zu slots) — fallback to CPU\n", m_slots.size());
#ifdef _WIN32
            OutputDebugStringA(_buf);
#endif
            fprintf(stderr, "%s", _buf);
        }
        return nullptr;
    }

    // Allocate CUDA buffers + stream + event on the target GPU
    int prevDev = -1;
    cudaGetDevice(&prevDev);
    if (gpuIdx >= 0) cudaSetDevice(gpuIdx);

    auto slot = std::make_unique<GpuNV12Slot>();
    cudaError_t e1 = cudaMallocPitch(&slot->bufY,  &slot->pitchY,  w, h);
    cudaError_t e2 = cudaMallocPitch(&slot->bufUV, &slot->pitchUV, w, h / 2);

    // Non-blocking stream: avoids NULL-stream implicit sync with inference.
    cudaStream_t stream = nullptr;
    cudaError_t e3 = cudaStreamCreateWithFlags(&stream, cudaStreamNonBlocking);

    if (prevDev >= 0) cudaSetDevice(prevDev);

    if (e1 != cudaSuccess || e2 != cudaSuccess) {
        NV12POOL_DBG("acquire: cudaMallocPitch FAILED %dx%d gpu=%d e1=%d e2=%d",
                     w, h, gpuIdx, (int)e1, (int)e2);
        int prev2 = -1; cudaGetDevice(&prev2);
        if (gpuIdx >= 0) cudaSetDevice(gpuIdx);
        if (e1 == cudaSuccess && slot->bufY) cudaFree(slot->bufY);
        if (e2 == cudaSuccess && slot->bufUV) cudaFree(slot->bufUV);
        if (e3 == cudaSuccess && stream) cudaStreamDestroy(stream);
        if (prev2 >= 0) cudaSetDevice(prev2);
        return nullptr;
    }

    slot->width  = w;
    slot->height = h;
    slot->gpuIdx = gpuIdx;
    slot->copyStream = (e3 == cudaSuccess) ? stream : nullptr;
    slot->state.store(GpuNV12Slot::STATE_ACTIVE, std::memory_order_release);

    GpuNV12Slot* raw = slot.get();
    m_slots.push_back(std::move(slot));

    // Always log new slot allocation to DebugView (rare event).
    {
        char _buf[256];
        snprintf(_buf, sizeof(_buf),
            "[NV12Pool] NEW slot #%zu: %dx%d gpu=%d Y=%p UV=%p pitchY=%zu stream=%p\n",
            m_slots.size(), w, h, gpuIdx, raw->bufY, raw->bufUV, raw->pitchY,
            raw->copyStream);
#ifdef _WIN32
        OutputDebugStringA(_buf);
#endif
        fprintf(stderr, "%s", _buf);
    }

    return raw;
}