/**
 * @file transform_hierarchy.h
 */
#pragma once

#include "maths_types.h"
#include "ral.h"
#include "render_types.h"

#define MAX_TF_NODE_CHILDREN \
  32 /** TEMP: Make it simpler to manage children in `transform_node`s　*/

typedef struct TransformHierarchy TransformHierarchy;

struct Transform_Node {
  ModelHandle model; /** A handle back to what model this node represents */
  Transform tf;
  Mat4 local_matrix_tf; /** cached local affine transform */
  Mat4 world_matrix_tf; /** cached world-space affine transform */

  struct transform_node* parent;
  struct transform_node* children[MAX_TF_NODE_CHILDREN];
  u32 n_children;
  struct transform_hierarchy* tfh;
};
typedef struct Transform_Node Transform_Node;
typedef struct Transform_Node TF_Node;

// --- Lifecycle

/** @brief Allocates and returns an empty transform hierarchy with a root node */
TransformHierarchy* TransformHierarchy_Create();

// /**
//  * @brief recursively frees all the children and then finally itself
//  * @note in the future we can use an object pool for the nodes
//  */
// void transform_hierarchy_free(transform_hierarchy* tfh);

// // --- Main usecase

// /** @brief Updates matrices of any invalidated nodes based on the `is_dirty` flag inside
// `transform`
//  */
// void transform_hierarchy_propagate_transforms(transform_hierarchy* tfh);

// // --- Queries

// /** @brief Get a pointer to the root node */
// Transform_Node* TransformHierarchy_RootNode(TransformHierarchy* tfh);

// // --- Mutations
// Transform_Node* TransformHierarchy_AddNode(transform_node* parent, ModelHandle model,
//                                              Transform tf);
// void transform_hierarchy_delete_node(transform_node* node);

// // --- Traversal

// /**
//  * @brief Perform a depth-first search traversal starting from `start_node`.
//  * @param start_node The starting node of the traversal.
//  * @param visit_node The function to call for each node visited. The callback should return false
//  to stop the traversal early.
//  * @param is_pre_order Indicates whether to do pre-order or post-order traversal i.e. when to
//  call the `visit_node` function.
//  * @param ctx_data An optional pointer to data that is be passed on each call to `visit_node`.
//  Can be used to carry additional information or context.
//  *
//  * @note The main use-cases are:
//             1. traversing the whole tree to update cached 4x4 affine transform matrices
//             (post-order)
//             2. freeing child nodes after deleting a node in the tree (post-order)
//             3. debug pretty printing the whole tree (post-order)
//  */
// void transform_hierarchy_dfs(transform_node* start_node,
//                              bool (*visit_node)(transform_node* node, void* ctx_data),
//                              bool is_pre_order, void* ctx_data);

// struct Core;
// void transform_hierarchy_debug_print(transform_node* start_node, struct Core* core);