#include "ge_physics.h"
#include "ge_collision_box.h"

typedef struct {
    ge_vector2i_t position;
    ge_vector2i_t size;
    ge_int_t tile_size;
    ge_phy_layers_t* layers; // 二维layer数组
} ge_phy_tilemap_t;

static inline int check_tilemap_collision(ge_phy_tilemap_t* tilemap, ge_phy_box_t* entity_collision) {
    Assert(tilemap->tile_size > 0);
    const int tile_size_int = tilemap->tile_size;

    // 计算瓦片地图的网格尺寸（列数和行数）
    const int grid_cols = tilemap->size.x / tile_size_int;
    const int grid_rows = tilemap->size.y / tile_size_int;

    // 计算实体碰撞盒在瓦片地图局部坐标系中的位置
    const ge_vector2i_t local_entity_pos = GE_VEC2I_SUB(
        entity_collision->position,
        tilemap->position
    );

    // 计算实体边界（使用闭区间）
    const int entity_left = local_entity_pos.x;
    const int entity_top = local_entity_pos.y;
    const int entity_right = entity_left + entity_collision->size.x - 1; // 闭区间右边界
    const int entity_bottom = entity_top + entity_collision->size.y - 1; // 闭区间下边界

    // 计算覆盖的瓦片范围
    const int start_tile_x = GE_MAX(0, entity_left / tile_size_int);
    const int start_tile_y = GE_MAX(0, entity_top / tile_size_int);
    const int end_tile_x = GE_MIN(grid_cols - 1, entity_right / tile_size_int);
    const int end_tile_y = GE_MIN(grid_rows - 1, entity_bottom / tile_size_int);

    // 遍历实体覆盖的瓦片区域
    for (int y = start_tile_y; y <= end_tile_y; y++) {
        for (int x = start_tile_x; x <= end_tile_x; x++) {
            // 计算当前瓦片的边界（开区间）
            const int tile_left = x * tile_size_int;
            const int tile_top = y * tile_size_int;
            const int tile_right = tile_left + tile_size_int; // 开区间右边界
            const int tile_bottom = tile_top + tile_size_int; // 开区间下边界

            // 检查实体是否实际接触到瓦片内部
            const int overlap_x = entity_left < tile_right && entity_right > tile_left;
            const int overlap_y = entity_top < tile_bottom && entity_bottom > tile_top;
            
            if (overlap_x && overlap_y && tilemap->layers[y * grid_cols + x] != 0) {
                return 1; // 检测到碰撞
            }
        }
    }

    return 0; // 无碰撞
}