#include "cuda_cpu_runtime.h"

// Thread-local storage for CUDA-like thread coordinates
__thread uint3 threadIdx = {0, 0, 0};
__thread uint3 blockIdx = {0, 0, 0};
__thread dim3 blockDim = {1, 1, 1};
__thread dim3 gridDim = {1, 1, 1};
int counts=0;
// Memory tracking table
#define MAX_ALLOCATIONS 1024
memory_tracker_t memory_table[MAX_ALLOCATIONS];
int memory_count = 0;

// CPU Runtime initialization
void cpu_runtime_init(void) {
    memory_count = 0;
    for (int i = 0; i < 1024; i++) {
        memory_table[i].cpu_ptr = NULL;
        memory_table[i].device_ptr = NULL;
        memory_table[i].size = 0;
        memory_table[i].is_allocated = 0;
    }
}

void cpu_runtime_cleanup(void) {
    for (int i = 0; i < memory_count; i++) {
        if (memory_table[i].is_allocated && memory_table[i].cpu_ptr) {
            free(memory_table[i].cpu_ptr);
            memory_table[i].is_allocated = 0;
        }
    }
    memory_count = 0;
}

// CUDA Memory Management API Emulation
cudaError_t cudaMalloc(void **devPtr, size_t size) {
    if(memory_count > MAX_ALLOCATIONS) {
        fprintf(stderr, "Error: Exceeded maximum memory allocations (%d)\n", MAX_ALLOCATIONS);
        return cudaErrorMemoryAllocation;
    }
    void *ptr = malloc(size);
    if (!ptr) {
        return cudaErrorMemoryAllocation;
    }
    
    *devPtr = ptr;
    memory_table[memory_count].cpu_ptr = ptr;
    memory_table[memory_count].device_ptr = ptr;  // Same on CPU
    memory_table[memory_count].size = size;
    memory_table[memory_count].is_allocated = 1;
    memory_count++;
    
    return cudaSuccess;
}

cudaError_t cudaFree(void *devPtr) {
    for (int i = 0; i < memory_count; i++) {
        if (memory_table[i].device_ptr == devPtr && memory_table[i].is_allocated) {
            free(memory_table[i].cpu_ptr);
            memory_table[i].is_allocated = 0;
            return cudaSuccess;
        }
    }
    return cudaErrorInvalidValue;
}

cudaError_t cudaMemcpy(void *dst, const void *src, size_t count, int kind) {
    // For CPU implementation, all memory is accessible
    memcpy(dst, src, count);
    return cudaSuccess;
}

cudaError_t cudaDeviceSynchronize(void) {
    // No-op for CPU implementation
    return cudaSuccess;
}

// Forward declaration for the kernel wrapper
void compute_kernel_wrapper(void **args, void *func);

// kernel execution emulation
cudaError_t cudaLaunchKernel(void *func, dim3 grid_dim, dim3 block_dim, 
                            void **args, size_t sharedMem, void *stream) {
    
    // Calculate total configuration
    long long total_blocks = grid_dim.x * grid_dim.y * grid_dim.z;
    long long threads_per_block = block_dim.x * block_dim.y * block_dim.z;
    long long total_threads = total_blocks * threads_per_block;
    
    long long max_omp_threads = omp_get_max_threads();
    long long threads_to_use = (total_blocks < max_omp_threads) ? total_blocks : max_omp_threads;
    
    // Process blocks in parallel, threads within blocks sequentially
    #pragma omp parallel num_threads(threads_to_use)
    {
        long long omp_thread_id = omp_get_thread_num();
        long long num_omp_threads = omp_get_num_threads();
        // Each OpenMP thread processes one or more blocks
        for (long long block_id = omp_thread_id; block_id < total_blocks; block_id += num_omp_threads) {
            // Set block coordinates (constant for all threads in this block)
            long long bx = block_id % grid_dim.x;
            long long by = (block_id / grid_dim.x) % grid_dim.y;
            long long bz = block_id / (grid_dim.x * grid_dim.y);
            
            // Set all threadIDs in this block
            for (long long thread_in_block = 0; thread_in_block < threads_per_block; thread_in_block++) {
                // Set thread-local CUDA coordinates
                blockIdx.x = bx;
                blockIdx.y = by;
                blockIdx.z = bz;
                
                threadIdx.x = thread_in_block % block_dim.x;
                threadIdx.y = (thread_in_block / block_dim.x) % block_dim.y;
                threadIdx.z = thread_in_block / (block_dim.x * block_dim.y);
                
                blockDim = block_dim;
                gridDim = grid_dim;
                
                // Execute kernel for this thread
                compute_kernel_wrapper(args, func);
            }
        }
    }
    
    return cudaSuccess;
}

// Error handling
const char* cudaGetErrorString(cudaError_t error) {
    switch (error) {
        case cudaSuccess:
            return "cudaSuccess";
        case cudaErrorMemoryAllocation:
            return "cudaErrorMemoryAllocation";
        case cudaErrorInvalidValue:
            return "cudaErrorInvalidValue";
        default:
            return "Unknown CUDA error";
    }
}