#ifndef TWN_RENDERING_C_H
#define TWN_RENDERING_C_H

#include "twn_textures_c.h"
#include "twn_util.h"
#include "twn_option.h"

#include <SDL2/SDL.h>
#include <stb_truetype.h>

#ifdef EMSCRIPTEN
#include <GLES2/gl2.h>
#else
#include <glad/glad.h>
#endif

#include <stdbool.h>

extern t_matrix4 camera_projection_matrix;
extern t_matrix4 camera_look_at_matrix;

#define QUAD_ELEMENT_BUFFER_LENGTH (65536 / 6)


typedef GLuint vertex_buffer;

typedef struct vertex_buffer_builder {
    size_t bytes_left;
    void *mapping;
} vertex_buffer_builder;


struct sprite_primitive {
    t_frect rect;
    t_color color;
    float rotation;
    t_texture_key texture_key;
    bool flip_x;
    bool flip_y;
    bool repeat;

    m_option_list(
        t_fvec2, texture_origin )
};

struct rect_primitive {
    t_frect rect;
    t_color color;
};

struct circle_primitive {
    float radius;
    t_color color;
    t_fvec2 position;
};

struct text_primitive {
    t_color color;
    t_fvec2 position;
    char *text;
    const char *font;
    int height_px;
};

enum primitive_2d_type {
    PRIMITIVE_2D_SPRITE,
    PRIMITIVE_2D_RECT,
    PRIMITIVE_2D_CIRCLE,
    PRIMITIVE_2D_TEXT,
};

struct primitive_2d {
    enum primitive_2d_type type;

    union {
        struct sprite_primitive sprite;
        struct rect_primitive rect;
        struct circle_primitive circle;
        struct text_primitive text;
    };
};

/* union for in-place recalculation of texture coordinates */
union uncolored_space_triangle {
    /* pending for sending, uvs are not final as texture atlases could update */
    struct uncolored_space_triangle_primitive {
        t_fvec3 v0;
        t_fvec2 uv0; /* in pixels */
        t_fvec3 v1;
        t_fvec2 uv1; /* in pixels */
        t_fvec3 v2;
        t_fvec2 uv2; /* in pixels */
    } primitive;

    /* TODO: have it packed? */
    /* structure that is passed in opengl vertex array */
    struct uncolored_space_triangle_payload {
        t_fvec3 v0;
        t_fvec2 uv0;
        t_fvec3 v1;
        t_fvec2 uv1;
        t_fvec3 v2;
        t_fvec2 uv2;
    } payload;
};

/* batch of primitives with overlapping properties */
struct mesh_batch {
    uint8_t *primitives;
};

struct mesh_batch_item {
    t_texture_key key;
    struct mesh_batch value;
};

struct text_cache {
    struct font_data **data;
};


/* renders the background, then the primitives in all render queues */
void render(void);

/* clears all render queues */
void render_queue_clear(void);

void create_circle_geometry(t_fvec2 position,
                            t_color color,
                            float radius,
                            size_t num_vertices,
                            SDL_Vertex **vertices_out,
                            int **indices_out);

struct sprite_batch {
    size_t size;             /* how many primitives are in current batch */
    enum texture_mode mode;
    bool constant_colored;   /* whether colored batch is uniformly colored */
    bool repeat;             /* whether repeat is needed */
} collect_sprite_batch(const struct primitive_2d primitives[], size_t len);

void render_sprites(const struct primitive_2d primitives[],
                    const struct sprite_batch batch);

void draw_uncolored_space_traingle_batch(struct mesh_batch *batch,
                                         t_texture_key texture_key);

/* text */

void render_text(const struct text_primitive *text);

void text_cache_init(struct text_cache *cache);

void text_cache_deinit(struct text_cache *cache);

/* vertex buffer */

vertex_buffer create_vertex_buffer(void);

void delete_vertex_buffer(vertex_buffer buffer);

void specify_vertex_buffer(vertex_buffer buffer, void *data, size_t bytes);

/* uses present in 1.5 buffer mapping feature */
vertex_buffer_builder build_vertex_buffer(vertex_buffer buffer, size_t bytes);

/* collects bytes for sending to the gpu until all is pushed, which is when false is returned */
bool push_to_vertex_buffer_builder(vertex_buffer_builder *builder,
                                   void *bytes,
                                   size_t size);

/* state */

void setup_viewport(int x, int y, int width, int height);

void clear_draw_buffer(void);

void swap_buffers(void);

void set_depth_range(double low, double high);

void bind_quad_element_buffer(void);

void render_circle(const struct circle_primitive *circle);

void render_rectangle(const struct rect_primitive *rectangle);

void use_space_pipeline(void);

void use_2d_pipeline(void);

void use_texture_mode(enum texture_mode mode);

void finally_render_sprites(struct primitive_2d const primitives[],
                            struct sprite_batch batch,
                            vertex_buffer buffer);

size_t get_sprite_payload_size(struct sprite_batch batch);

bool push_sprite_payload_to_vertex_buffer_builder(struct sprite_batch batch,
                                                  vertex_buffer_builder *builder,
                                                  t_fvec2 v0, t_fvec2 v1, t_fvec2 v2, t_fvec2 v3,
                                                  t_fvec2 uv0, t_fvec2 uv1, t_fvec2 uv2, t_fvec2 uv3,
                                                  t_color color);

void finally_draw_uncolored_space_traingle_batch(struct mesh_batch const *batch,
                                                 t_texture_key texture_key,
                                                 vertex_buffer buffer);

size_t get_text_payload_size(void);

bool push_text_payload_to_vertex_buffer_builder(struct font_data const *font_data,
                                                vertex_buffer_builder *builder,
                                                stbtt_aligned_quad quad);

void finally_draw_text(struct font_data const *font_data,
                       size_t len,
                       t_color color,
                       vertex_buffer buffer);

#endif