#pragma once

/*
  Common abbreviations:
  buf = buffer
  tex = texture
  desc = description
  idx = index
*/

// Standard library includes
#include <assert.h>
#include <math.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Third party dependency includes
#include <glfw3.h>

#define inlined inline  // remove inlined functions so we can generate bindings

typedef uint8_t u8;
typedef uint16_t u16;
typedef uint32_t u32;
typedef uint64_t u64;

typedef int8_t i8;
typedef int16_t i16;
typedef int32_t i32;
typedef int64_t i64;

typedef float f32;
typedef double f64;

_Static_assert(sizeof(bool) == 1, "type bool should be 1 byte");

_Static_assert(sizeof(u8) == 1, "type u8 should be 1 byte");
_Static_assert(sizeof(u16) == 2, "type u16 should be 2 byte");
_Static_assert(sizeof(u32) == 4, "type u32 should be 4 byte");
_Static_assert(sizeof(u64) == 8, "type u64 should be 8 byte");

_Static_assert(sizeof(i8) == 1, "type i8 should be 1 byte");
_Static_assert(sizeof(i16) == 2, "type i16 should be 2 byte");
_Static_assert(sizeof(i32) == 4, "type i32 should be 4 byte");
_Static_assert(sizeof(i64) == 8, "type i64 should be 8 byte");

_Static_assert(sizeof(f32) == 4, "type f32 should be 4 bytes");
_Static_assert(sizeof(f64) == 8, "type f64 should be 8 bytes");

_Static_assert(sizeof(ptrdiff_t) == 8, "type ptrdiff_t should be 8 bytes");

#define alignof(x) _Alignof(x)

#define threadlocal _Thread_local

// Wrap a u32 to make a type-safe "handle" or ID
#define DEFINE_HANDLE(name) \
  typedef struct name name; \
  struct name {             \
    u32 raw;                \
  }

#define KB(x) ((size_t)x * 1000)
#define MB(x) ((size_t)x * 1000 * 1000)
#define GB(x) ((size_t)x * 1000 * 1000 * 1000)

// Platform informs renderer backend (unless user overrides)
#if defined(CEL_PLATFORM_LINUX) || defined(CEL_PLATFORM_WINDOWS)
#define GPU_VULKAN 1
#else
#define GPU_METAL 1
#endif

// --- Forward declare vital structures
typedef struct core core;
typedef struct renderer renderer;
typedef struct input_state input_state;
struct GLFWwindow;

// Global getters
core* get_g_core();
renderer* get_g_renderer();
struct GLFWwindow* get_window();

struct core {
  const char* app_name;
  struct GLFWwindow* window;
  bool should_exit;
  renderer* renderer;
  input_state* input;
};
extern core g_core; /** @brief global `Core` that other files can use */

void core_bringup(const char* window_name, struct GLFWwindow* optional_window);
void core_shutdown();
void core_resize_viewport(int width, int height);
bool app_should_exit();

// --- Error handling

// global error handling
#define CEL_OK 0
extern int g_last_error;

/** @brief get last global status value */
int cel_check_status();
void _cel_push_error(int error_code);

// --- Memory facilities: Allocators, helpers

// TODO: Arenas

// Pool
typedef struct void_pool_header void_pool_header;  // TODO: change name of this
struct void_pool_header {
  void_pool_header* next;
};

typedef struct void_pool {
  u64 capacity;
  u64 entry_size;
  u64 count;
  void* backing_buffer;
  void_pool_header* free_list_head;
  const char* debug_label;
} void_pool;

void_pool void_pool_create(void* storage, const char* debug_label, u64 capacity, u64 entry_size);
void void_pool_free_all(void_pool* pool);
bool void_pool_is_empty(void_pool* pool);
bool void_pool_is_full(void_pool* pool);
void* void_pool_get(void_pool* pool, u32 raw_handle);
void* void_pool_alloc(void_pool* pool, u32* out_raw_handle);
void void_pool_dealloc(void_pool* pool, u32 raw_handle);
u32 void_pool_insert(void_pool* pool, void* item);

#define TYPED_POOL(T, Name)                                                          \
  typedef struct Name##_pool {                                                       \
    void_pool inner;                                                                 \
  } Name##_pool;                                                                     \
                                                                                     \
  static Name##_pool Name##_pool_create(void* storage, u64 cap, u64 entry_size) {    \
    void_pool p = void_pool_create(storage, "\"" #Name "\"", cap, entry_size);       \
    return (Name##_pool){ .inner = p };                                              \
  }                                                                                  \
  static inline T* Name##_pool_get(Name##_pool* pool, Name##_handle handle) {        \
    return (T*)void_pool_get(&pool->inner, handle.raw);                              \
  }                                                                                  \
  static inline T* Name##_pool_alloc(Name##_pool* pool, Name##_handle* out_handle) { \
    return (T*)void_pool_alloc(&pool->inner, &out_handle->raw);                      \
  }                                                                                  \
  static inline void Name##_pool_dealloc(Name##_pool* pool, Name##_handle handle) {  \
    void_pool_dealloc(&pool->inner, handle.raw);                                     \
  }                                                                                  \
  static Name##_handle Name##_pool_insert(Name##_pool* pool, T* item) {              \
    u32 raw_handle = void_pool_insert(pool, item);                                   \
    return (Name##_handle){ .raw = raw_handle };                                     \
  }

// --- Strings

// --- Logging

// Log levels
typedef enum loglevel {
  LOG_LEVEL_FATAL = 0,
  LOG_LEVEL_ERROR = 1,
  LOG_LEVEL_WARN = 2,
  LOG_LEVEL_INFO = 3,
  LOG_LEVEL_DEBUG = 4,
  LOG_LEVEL_TRACE = 5,
} loglevel;

void log_output(char* module, loglevel level, const char* msg, ...);

#define NAMESPACED_LOGGER(module)                    \
  static inline void FATAL(const char* msg, ...) {   \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_FATAL, msg, args); \
    va_end(args);                                    \
  }                                                  \
  static inline void ERROR(const char* msg, ...) {   \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_ERROR, msg, args); \
    va_end(args);                                    \
  }                                                  \
  static inline void WARN(const char* msg, ...) {    \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_WARN, msg, args);  \
    va_end(args);                                    \
  }                                                  \
  static inline void INFO(const char* msg, ...) {    \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_INFO, msg, args);  \
    va_end(args);                                    \
  }                                                  \
  static inline void DEBUG(const char* msg, ...) {   \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_DEBUG, msg, args); \
    va_end(args);                                    \
  }                                                  \
  static inline void TRACE(const char* msg, ...) {   \
    va_list args;                                    \
    va_start(args, msg);                             \
    log_output(#module, LOG_LEVEL_TRACE, msg, args); \
    va_end(args);                                    \
  }

// --- Maths

// Constants
#define PI 3.14159265358979323846
#define HALF_PI 1.57079632679489661923
#define TAU (2.0 * PI)

/** @brief 2D Vector */
typedef struct vec2 {
  f32 x, y;
} vec2;

/** @brief 3D Vector */
typedef struct vec3 {
  f32 x, y, z;
} vec3;

/** @brief 4D Vector */
typedef struct vec4 {
  f32 x, y, z, w;
} vec4;

/** @brief Quaternion */
typedef vec4 quat;

/** @brief 4x4 Matrix */
typedef struct mat4 {
  // TODO: use this format for more readable code: vec4 x_axis, y_axis, z_axis, w_axis;
  f32 data[16];
} mat4;

/** @brief 3D affine transformation */
typedef struct transform {
  vec3 position;
  quat rotation;
  vec3 scale;
  bool is_dirty;
} transform;

_Static_assert(alignof(vec3) == 4, "vec3 is 4 byte aligned");
_Static_assert(sizeof(vec3) == 12, "vec3 is 12 bytes so has no padding");
_Static_assert(alignof(vec4) == 4, "vec4 is 4 byte aligned");

inlined vec3 vec3_create(f32 x, f32 y, f32 z);
inlined vec3 vec3_add(vec3 u, vec3 v);
inlined vec3 vec3_sub(vec3 u, vec3 v);
inlined vec3 vec3_mult(vec3 u, f32 s);
inlined vec3 vec3_div(vec3 u, f32 s);
inlined vec3 vec3_len_squared(vec3 a);
inlined f32 vec3_len(vec3 a);
inlined vec3 vec3_negate(vec3 a);
inlined vec3 vec3_normalise(vec3 a);
inlined f32 vec3_dot(vec3 a, vec3 b);
inlined vec3 vec3_cross(vec3 a, vec3 b);

inlined vec4 vec4_create(f32 x, f32 y, f32 z, f32 w);

// quaternion functions
inlined quat quat_ident();
quat quat_from_axis_angle(vec3 axis, f32 angle, bool normalise);
quat quat_slerp(quat a, quat b, f32 percentage);

// matrix functions
inlined mat4 mat4_ident();
mat4 mat4_translation(vec3 position);
mat4 mat4_scale(vec3 scale);
mat4 mat4_rotation(quat rotation);
mat4 mat4_mult(mat4 lhs, mat4 rhs);
mat4 mat4_transposed(mat4 m);
mat4 mat4_perspective(f32 fov_radians, f32 aspect_ratio, f32 near_clip, f32 far_clip);
mat4 mat4_orthographic(f32 left, f32 right, f32 bottom, f32 top, f32 near_clip, f32 far_clip);
mat4 mat4_look_at(vec3 position, vec3 target, vec3 up);

// transform functions
inlined transform transform_create(vec3 pos, quat rot, vec3 scale);
mat4 transform_to_mat(transform* tf);

// helpers

#define vec3(x, y, z) ((vec3){ x, y, z })
#define vec4(x, y, z, w) ((vec4){ x, y, z, w })
inlined vec4 v3tov4(vec3 v3) { return vec4_create(v3.x, v3.y, v3.z, 1.0); }

static const vec3 VEC3_X = vec3(1.0, 0.0, 0.0);
static const vec3 VEC3_NEG_X = vec3(-1.0, 0.0, 0.0);
static const vec3 VEC3_Y = vec3(0.0, 1.0, 0.0);
static const vec3 VEC3_NEG_Y = vec3(0.0, -1.0, 0.0);
static const vec3 VEC3_Z = vec3(0.0, 0.0, 1.0);
static const vec3 VEC3_NEG_Z = vec3(0.0, 0.0, -1.0);
static const vec3 VEC3_ZERO = vec3(0.0, 0.0, 0.0);
static const vec3 VEC3_ONES = vec3(1.0, 1.0, 1.0);

// --- RAL

DEFINE_HANDLE(buf_handle);
DEFINE_HANDLE(tex_handle);
DEFINE_HANDLE(pipeline_handle);
DEFINE_HANDLE(compute_pipeline_handle);

#define MAX_VERTEX_ATTRIBUTES 16
#define MAX_SHADER_BINDINGS 16

// Backend-specific structs
typedef struct gpu_swapchain gpu_swapchain;
typedef struct gpu_encoder gpu_encoder;  // Render command encoder
typedef struct gpu_compute_encoder gpu_compute_encoder;
typedef struct gpu_buffer gpu_buffer;
typedef struct gpu_texture gpu_texture;

// NOTE: Can we just use Storage buffer for everything?
// typedef enum gpu_buf_type {} gpu_buf_type;

typedef enum gpu_tex_type {
  TEXTURE_TYPE_2D,
  TEXTURE_TYPE_3D,
  TEXTURE_TYPE_2D_ARRAY,
  TEXTURE_TYPE_CUBE_MAP,
  TEXTURE_TYPE_COUNT
} gpu_tex_type;

/** @brief Texture Description - used by texture creation functions */
typedef struct texture_desc {
  gpu_tex_type tex_type;
  // GPU_TextureFormat format;
  int width, height, num_channels;
} texture_desc;

/// @strip_prefix(ATTR_)
typedef enum vertex_attrib_type {
  ATTR_F32,
  ATTR_F32x2,
  ATTR_F32x3,
  ATTR_F32x4,
  ATTR_U32,
  ATTR_U32x2,
  ATTR_U32x3,
  ATTR_U32x4,
  ATTR_I32,
  ATTR_I32x2,
  ATTR_I32x3,
  ATTR_I32x4,
} vertex_attrib_type;

typedef struct vertex_desc {
  const char* label;
  vertex_attrib_type attributes[MAX_VERTEX_ATTRIBUTES];
  u32 attribute_count;
  u32 padding;
} vertex_desc;

// Some default formats
vertex_desc static_3d_vertex_format();

typedef enum shader_binding_type {
  BINDING_BYTES,
  BINDING_BUFFER,
  BINDING_BUFFER_ARRAY,
  BINDING_TEXTURE,
  BINDING_TEXTURE_ARRAY,
  BINDING_SAMPLER,
  BINDING_COUNT
} shader_binding_type;

typedef enum shader_stage {
  STAGE_VERTEX = 1 << 0,
  STAGE_FRAGMENT = 1 << 1,
  STAGE_COMPUTE = 1 << 2,
} shader_stage;

typedef struct shader_binding {
  const char* label;
  shader_binding_type binding_type;
  shader_stage visibility;
  union {
    struct {
      u32 size;
      void* data;
    } bytes;
    struct {
      buf_handle handle;
    } buffer;
    struct {
      tex_handle handle;
    } texture;
  } data;
} shader_binding;

typedef struct shader_data_layout {
  shader_binding bindings[MAX_SHADER_BINDINGS];
  size_t binding_count;
} shader_data_layout;

typedef struct shader_function {
  const char* source;
  bool is_spirv;
  const char* entry_point;
  shader_stage stage;
} shader_function;

typedef enum cull_mode { Cull_BackFace, Cull_FrontFace } cull_mode;

typedef struct gfx_pipeline_desc {
  const char* label;
  vertex_desc vertex_desc;
  shader_function vertex;
  shader_function fragment;
  // ShaderDataLayout data_layouts[MAX_SHADER_DATA_LAYOUTS];
  // u32 data_layouts_count;
} gfx_pipeline_desc;

typedef struct compute_pipeline_desc { /* TODO */
} compute_pipeline_desc;

typedef struct render_pass_desc {
} render_pass_desc;

// --- RAL Functions

// Resources
buf_handle ral_buffer_create(u64 size, const void* data);
void ral_buffer_destroy(buf_handle handle);

tex_handle ral_texture_create(texture_desc desc, bool create_view, const void* data);
tex_handle ral_texture_load_from_file(const char* filepath);
void ral_texture_destroy(tex_handle handle);

// Encoders / cmd buffers
/** @brief grabs a new command encoder from the pool of available ones and begins recording */
gpu_encoder* ral_render_encoder(render_pass_desc rpass_desc);

gpu_compute_encoder ral_compute_encoder();

void ral_encoder_finish(gpu_encoder* enc);
void ral_encoder_submit(gpu_encoder* enc);
void ral_encoder_finish_and_submit(gpu_encoder* enc);

pipeline_handle ral_gfx_pipeline_create(gfx_pipeline_desc desc);
void ral_gfx_pipeline_destroy(pipeline_handle handle);

compute_pipeline_handle ral_compute_pipeline_create(compute_pipeline_desc);
void ral_compute_pipeline_destroy(compute_pipeline_handle handle);

// Encoding
void ral_encode_bind_pipeline(gpu_encoder* enc, pipeline_handle pipeline);
void ral_encode_set_vertex_buf(gpu_encoder* enc, buf_handle vbuf);
void ral_encode_set_index_buf(gpu_encoder* enc, buf_handle ibuf);
void ral_encode_set_texture(gpu_encoder* enc, tex_handle texture, u32 slot);
void ral_encode_draw_tris(gpu_encoder* enc, size_t start, size_t count);

// Backend lifecycle
void ral_backend_init(const char* window_name, struct GLFWwindow* window);
void ral_backend_shutdown();
void ral_backend_resize_framebuffer(int width, int height);

// Frame lifecycle

typedef void (*scoped_draw_commands)();  // callback that we run our draw commands within.
// allows us to wrap some api-specific behaviour

void ral_frame_start();
void ral_frame_draw(scoped_draw_commands draw_fn);
void ral_frame_end();

// --- Containers (Forward declared as internals are unnecessary for external header)
typedef struct u32_darray u32_darray;

// --- Base Renderer types

DEFINE_HANDLE(mesh_handle);
DEFINE_HANDLE(material_handle);
DEFINE_HANDLE(model_handle);

typedef struct geometry {
  vertex_desc vertex_format;
  void* vertex_data;
  bool has_indices;  // When this is false indexed drawing is not used
  u32_darray* indices;
} geometry;

typedef u32 joint_idx;
typedef struct armature {
} armature;

/** @brief Mesh data that has been uploaded to GPU and is ready to be rendered each frame
           Gets stored in a pool */
typedef struct mesh {
  buf_handle vertex_buffer;
  buf_handle index_buffer;
  // todo: material?
  geometry geo;  // the originating mesh data
  const armature* skinning_data;
} mesh;

typedef struct draw_mesh_cmd {
  mesh_handle mesh;
  mat4 transform;
  vec3 bounding_sphere_center;
  f32 bounding_sphere_radius;
  const armature* skinning_data;  // NULL = static mesh
  bool cast_shadows;
} draw_mesh_cmd;

// --- Geometry/Mesh primitives

geometry geo_plane(f32 x_scale, f32 z_scale, u32 tiling_u, u32 tiling_v);
geometry geo_cuboid(f32 x_scale, f32 y_scale, f32 z_scale);
geometry geo_cylinder(f32 radius, f32 height, u32 resolution);
geometry geo_cone(f32 radius, f32 height, u32 resolution);
geometry geo_uv_sphere(f32 radius, u32 north_south_lines, u32 east_west_lines);
geometry geo_ico_sphere(f32 radius, f32 n_subdivisions);
void geo_scale_uniform(geometry* geo, f32 scale);
void geo_scale_xyz(geometry* geo, vec3 scale_xyz);

// --- Renderer

// void renderer_init(renderer* rend);
// void renderer_shutdown(renderer* rend);

typedef struct camera {
  vec3 position;
  // TODO: move to using a quaternion for the camera's orientation - need to update
  //       how the view transformation matrix is calculated
  vec3 forwards;
  vec3 up;
  f32 fov;
} camera;

/** @brief calculates the view and projection matrices for a camera  */
mat4 camera_view_proj(camera camera, f32 lens_height, f32 lens_width, mat4* out_view, mat4* out_proj);

// TODO: Filament PBR model

// --- Scene / Transform Hierarchy

// --- Gameplay

// --- Game and model data

typedef struct model {
} model;

model_handle model_load_from_gltf(const char* path);

// --- Animation

typedef enum keyframe_kind { Keyframe_Rotation, Keyframe_Translation, Keyframe_Scale, Keyframe_Weights } keyframe_kind;

extern const char* keyframe_kind_strings[4];

typedef union keyframe {
  quat rotation;
  vec3 translation;
  vec3 scale;
  f32 weights[4];
} keyframe;

typedef struct keyframes {
  keyframe_kind kind;
  keyframe* values;
  size_t n_frames;
} keyframes;

typedef enum interpolation { Interpolation_Step, Interpolation_Linear, Interpolation_Cubic } interpolation;

extern const char* interpolation_strings[3];

typedef struct animation_spline {
  f32* timestamps;
  size_t n_timestamps;
  keyframes frames;
} animation_spline;

// Compute shader approach so we only need one kind of vertex format

// --- Input

// --- Collisions

// --- Physics

// --- Platform

// --- Audio