#pragma once

#include <assets/kasset_types.h>
#include <defines.h>
#include <identifiers/identifier.h>
#include <math/math_types.h>
#include <strings/kname.h>

#define TERRAIN_MAX_MATERIAL_COUNT 4

/*
Need to modify the geometry structure/functions to allow for multiple materials.
Write shader to handle 8 material weights/blending
Multi-materials (combine maps using uv offsets)?
Load terrain configuration from file
Load heightmaps
calculate normals/tangents (copy-pasta of existing, but using terrain_vertex
structure) New material type? (terrain/multi material)
*/

typedef struct terrain_vertex {
	/** @brief The position of the vertex */
	vec3 position;
	/** @brief The normal of the vertex. */
	vec3 normal;
	/** @brief The texture coordinate of the vertex. */
	vec2 texcoord;
	/** @brief The colour of the vertex. */
	vec4 colour;
	/** @brief The tangent of the vertex. */
	vec4 tangent;

	/** @brief A collection of material weights for this vertex. */
	f32 material_weights[TERRAIN_MAX_MATERIAL_COUNT];
} terrain_vertex;

typedef struct terrain_vertex_data {
	f32 height;
} terrain_vertex_data;

typedef struct terrain_chunk_lod {
	/** @brief The index count for the chunk surface. */
	u32 surface_index_count;

	/** @brief The total index count, including those for side skirts. */
	u32 total_index_count;
	/** @brief The index data. */
	u32 *indices;
	/** @brief The offset from the beginning of the index buffer. */
	u64 index_buffer_offset;
} terrain_chunk_lod;

typedef struct terrain_chunk {
	/** @brief The chunk generation. Incremented every time the geometry changes. */
	u16 generation;
	u32 surface_vertex_count;
	u32 total_vertex_count;
	terrain_vertex *vertices;
	u64 vertex_buffer_offset;

	terrain_chunk_lod *lods;

	/** @brief The center of the geometry in local coordinates. */
	vec3 center;
	/** @brief The extents of the geometry in local coordinates. */
	extents_3d extents;

	/** @brief The material instance associated with this geometry. */
	kmaterial_instance material;

	u8 current_lod;
} terrain_chunk;

typedef enum terrain_state {
	TERRAIN_STATE_UNDEFINED,
	TERRAIN_STATE_CREATED,
	TERRAIN_STATE_INITIALIZED,
	TERRAIN_STATE_LOADING,
	TERRAIN_STATE_LOADED
} terrain_state;

typedef struct terrain {
	identifier id;
	u32 generation;
	terrain_state state;
	kname name;
	kasset_heightmap_terrain *asset;
	kname material_name;
	u32 tile_count_x;
	u32 tile_count_z;
	// How large each tile is on the x axis.
	f32 tile_scale_x;
	// How large each tile is on the z axis.
	f32 tile_scale_z;
	// The max height of the generated terrain.
	f32 scale_y;

	u32 chunk_size;

	u32 vertex_data_length;
	terrain_vertex_data *vertex_datas;

	extents_3d extents;
	vec3 origin;

	u32 chunk_count;
	// row by row, then column
	// 0, 1, 2, 3
	// 4, 5, 6, 7
	// 8, 9, ...
	terrain_chunk *chunks;

	u8 lod_count;

	u32 material_count;
	kname *material_names;
} terrain;

KAPI b8 terrain_create (kasset_heightmap_terrain *asset, terrain *out_terrain);
KAPI void terrain_destroy (terrain *t);

KAPI b8 terrain_initialize (terrain *t);
KAPI b8 terrain_load (terrain *t);
KAPI b8 terrain_chunk_load (terrain *t, terrain_chunk *chunk);
KAPI b8 terrain_unload (terrain *t);
KAPI b8 terrain_chunk_unload (terrain *t, terrain_chunk *chunk);

KAPI b8 terrain_update (terrain *t);

KAPI void terrain_geometry_generate_normals (u32 vertex_count, struct terrain_vertex *vertices, u32 index_count, u32 *indices);

KAPI void terrain_geometry_generate_tangents (u32 vertex_count, struct terrain_vertex *vertices, u32 index_count, u32 *indices);