/**
 * @file mvgal_cmd_dag.c
 * @brief Command Buffer DAG Implementation - Phase 3
 */

#include "mvgal/mvgal_cmd_dag.h"
#include "mvgal/mvgal_log.h"
#include "mvgal/mvgal.h"

#include <stdlib.h>
#include <string.h>

/* ============================================================================
 * Device-to-DAG mapping for active command buffers
 * ============================================================================ */

typedef struct {
    VkCommandBuffer cmd_buf;
    mvgal_cmd_dag_t* dag;
} cmd_dag_entry_t;

#define CMD_DAG_BUCKETS 256
static cmd_dag_entry_t g_cmd_dag_map[CMD_DAG_BUCKETS];

static uint32_t hash_cmd_buf(VkCommandBuffer cmd)
{
    return (uint32_t)((uintptr_t)cmd ^ ((uintptr_t)cmd >> 32)) & (CMD_DAG_BUCKETS - 1);
}

/* ============================================================================
 * DAG Node Management
 * ============================================================================ */

static mvgal_cmd_node_t* mvgal_cmd_node_create(mvgal_cmd_type_t type)
{
    mvgal_cmd_node_t* node = calloc(1, sizeof(*node));
    if (!node) return NULL;
    
    node->type = type;
    node->dep_capacity = 16;
    node->deps = calloc(node->dep_capacity, sizeof(mvgal_cmd_node_t*));
    if (!node->deps) {
        free(node);
        return NULL;
    }
    
    return node;
}

static void mvgal_cmd_node_destroy(mvgal_cmd_node_t* node)
{
    if (!node) return;
    free(node->deps);
    free(node);
}

/* ============================================================================
 * DAG Management
 * ============================================================================ */

mvgal_cmd_dag_t* mvgal_dag_create(void)
{
    mvgal_cmd_dag_t* dag = calloc(1, sizeof(*dag));
    return dag;
}

void mvgal_dag_destroy(mvgal_cmd_dag_t* dag)
{
    if (!dag) return;
    
    mvgal_cmd_node_t* node = dag->head;
    while (node) {
        mvgal_cmd_node_t* next = node->next;
        mvgal_cmd_node_destroy(node);
        node = next;
    }
    
    free(dag);
}

mvgal_cmd_node_t* mvgal_dag_add_node(mvgal_cmd_dag_t* dag, mvgal_cmd_type_t type)
{
    if (!dag) return NULL;
    
    mvgal_cmd_node_t* node = mvgal_cmd_node_create(type);
    if (!node) return NULL;
    
    node->next = dag->head;
    dag->head = node;
    dag->node_count++;
    
    return node;
}

void mvgal_dag_add_dependency(mvgal_cmd_node_t* from, mvgal_cmd_node_t* to)
{
    if (!from || !to || from == to) return;
    
    /* Check if dependency already exists */
    for (size_t i = 0; i < to->dep_count; i++) {
        if (to->deps[i] == from) return;
    }
    
    /* Expand capacity if needed */
    if (to->dep_count >= to->dep_capacity) {
        size_t new_cap = to->dep_capacity * 2;
        mvgal_cmd_node_t** new_deps = realloc(to->deps, new_cap * sizeof(mvgal_cmd_node_t*));
        if (!new_deps) return;
        to->deps = new_deps;
        to->dep_capacity = new_cap;
    }
    
    to->deps[to->dep_count++] = from;
}

/* ============================================================================
 * Command Buffer Recording Interception
 * ============================================================================ */

mvgal_cmd_dag_t* mvgal_cmd_dag_begin(VkCommandBuffer cmd_buf)
{
    mvgal_cmd_dag_t* dag = mvgal_dag_create();
    if (!dag) return NULL;
    
    uint32_t bucket = hash_cmd_buf(cmd_buf);
    g_cmd_dag_map[bucket].cmd_buf = cmd_buf;
    g_cmd_dag_map[bucket].dag = dag;
    
    return dag;
}

void mvgal_cmd_dag_end(VkCommandBuffer cmd_buf)
{
    uint32_t bucket = hash_cmd_buf(cmd_buf);
    if (g_cmd_dag_map[bucket].cmd_buf == cmd_buf) {
        mvgal_dag_destroy(g_cmd_dag_map[bucket].dag);
        g_cmd_dag_map[bucket].cmd_buf = VK_NULL_HANDLE;
        g_cmd_dag_map[bucket].dag = NULL;
    }
}

/* ============================================================================
 * Command Recording Interceptions
 * ============================================================================ */

void mvgal_record_cmd_draw(mvgal_cmd_dag_t* dag, uint32_t vertex_count, uint32_t instance_count)
{
    mvgal_cmd_node_t* node = mvgal_dag_add_node(dag, MVGAL_CMD_DRAW);
    if (node) {
        node->args.draw.vertex_count = vertex_count;
        node->args.draw.instance_count = instance_count;
    }
}

void mvgal_record_cmd_dispatch(mvgal_cmd_dag_t* dag, uint32_t group_x, uint32_t group_y, uint32_t group_z)
{
    mvgal_cmd_node_t* node = mvgal_dag_add_node(dag, MVGAL_CMD_DISPATCH);
    if (node) {
        node->args.dispatch.group_x = group_x;
        node->args.dispatch.group_y = group_y;
        node->args.dispatch.group_z = group_z;
    }
}

void mvgal_record_cmd_barrier(mvgal_cmd_dag_t* dag, uint32_t dependency_count, const VkDependencyInfo* info)
{
    mvgal_cmd_node_t* node = mvgal_dag_add_node(dag, MVGAL_CMD_BARRIER);
    if (node) {
        node->args.barrier.dependency_count = dependency_count;
        node->args.barrier.info = info;
    }
}

/* ============================================================================
 * DAG Capture (Incomplete - requires VkCommandBuffer inheritance)
 * ============================================================================ */

VkResult mvgal_capture_command_buffer(VkCommandBuffer cmd, mvgal_cmd_dag_t** dag)
{
    (void)cmd;
    if (!dag) return VK_ERROR_INCOMPATIBLE_DRIVER;
    
    *dag = NULL;
    return VK_ERROR_INITIALIZATION_FAILED;
}

/* ============================================================================
 * DAG Translation and Emission (Stub Implementation)
 * ============================================================================ */

mvgal_cmd_dag_t* mvgal_translate_dag(mvgal_cmd_dag_t* dag, mvgal_vendor_t vendor)
{
    (void)vendor;
    return dag; /* In production: return translated copy */
}

VkResult mvgal_emit_dag(mvgal_cmd_dag_t* dag, VkCommandBuffer cmd)
{
    (void)dag;
    (void)cmd;
    return VK_ERROR_LAYER_NOT_PRESENT;
}