// Copyright (C) 2022 RozK
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#ifndef _RK_ENGINE_RENDER_H
#define _RK_ENGINE_RENDER_H

#include "types.hpp"
#include "math.hpp"

extern rk_vec3 rk_view_origin;
extern rk_vec3 rk_view_lookat;
extern rk_mat4 rk_view;
extern rk_mat4 rk_view_km; //TODO: remove from engine

extern float rk_projection_hfov;
extern float rk_projection_ratio;
extern float rk_projection_near;
extern float rk_projection_far;
extern rk_mat4 rk_projection;

typedef rk_handle_t rk_window_t;
typedef rk_handle_t rk_shader_t;
typedef rk_handle_t rk_input_t;
typedef rk_handle_t rk_texture_t;
typedef rk_handle_t rk_triangles_t;
typedef rk_handle_t rk_vertices_t;
typedef rk_handle_t rk_batch_t;

#define RK_FLAG(bit) (1 << (bit))

enum rk_input_mode : rk_uint {
    RK_INPUT_IDENTITY = 0,
    RK_INPUT_VIEW_POSITION = 1,
    RK_INPUT_VIEW_ORIENTATION = 2
};

enum rk_texture_format : rk_uint {
    RK_TEXTURE_FORMAT_SRGB8_A8 = 0,
    RK_TEXTURE_FORMAT_RGBA8 = 1,
    RK_TEXTURE_FORMAT_RGB10_A2 = 2,
    RK_TEXTURE_FORMAT_32F = 3
};

enum rk_texture_flags : rk_uint {
    RK_TEXTURE_FLAG_3D = RK_FLAG(0),
    RK_TEXTURE_FLAG_MIPMAPS = RK_FLAG(1),
    RK_TEXTURE_FLAG_MIN_NEAREST = 0,
    RK_TEXTURE_FLAG_MIN_LINEAR = RK_FLAG(2),
    RK_TEXTURE_FLAG_MAG_NEAREST = 0,
    RK_TEXTURE_FLAG_MAG_LINEAR = RK_FLAG(3),
};

enum rk_vertex_format : rk_ubyte {
    RK_VERTEX_FORMAT_END = 0,
    RK_VERTEX_FORMAT_VEC2_FLOAT = 1,
    RK_VERTEX_FORMAT_VEC2_USHORT = 2,
    RK_VERTEX_FORMAT_VEC3_FLOAT = 3,
    RK_VERTEX_FORMAT_VEC3_INT10 = 4,
};

enum rk_instance_flags : rk_ubyte {
    RK_INSTANCE_FLAG_SPAWNED = RK_FLAG(0),
    RK_INSTANCE_FLAG_VISIBLE = RK_FLAG(1)
};

enum : rk_ubyte { RK_INSTANCE_FLAGS_SPAWNED_VISIBLE = RK_INSTANCE_FLAG_SPAWNED | RK_INSTANCE_FLAG_VISIBLE };

enum : rk_uint { RK_BATCH_MAX_SIZE = 65536 };

enum rk_batch_translation_format : rk_uint {
    RK_BATCH_TRANSLATION_FORMAT_FLOAT = 0,
    RK_BATCH_TRANSLATION_FORMAT_SHORT = 1
};

enum rk_batch_orientation_format : rk_uint {
    RK_BATCH_ORIENTATION_FORMAT_NONE = 0,
    RK_BATCH_ORIENTATION_FORMAT_FLOAT = 1,
    RK_BATCH_ORIENTATION_FORMAT_INT10 = 2
};

union rk_mesh {
    rk_uint packed;
    struct {
        rk_ushort offset;
        rk_ushort count;
    };
};

RK_EXPORT rk_window_t rk_initialize(
    char const * name,
    rk_uint width,
    rk_uint height);

RK_EXPORT rk_shader_t rk_load_shader(
    char const * name);

RK_EXPORT void rk_select_shader(
    rk_shader_t _shader);

RK_EXPORT rk_input_t rk_resolve_input(
    char const * name);

RK_EXPORT void rk_set_input_float(
    rk_input_t input,
    float value);

RK_EXPORT void rk_set_input_vec3(
    rk_input_t input,
    rk_vec3 const & value,
    rk_input_mode mode);

RK_EXPORT rk_texture_t rk_create_texture(
    rk_uint slot,
    char const * input,
    rk_texture_format format,
    rk_uint width,
    rk_uint height,
    rk_uint nlevels,
    rk_texture_flags flags,
    void const * pixels);

RK_EXPORT rk_triangles_t rk_create_triangles(
    rk_uint nvertices,
    rk_vec3 const * vertices);

RK_EXPORT rk_vertices_t rk_create_vertices(
    rk_vertex_format const * format,
    rk_uint nvertices,
    void const * vertices,
    rk_uint nindices,
    rk_ushort const * indices);

RK_EXPORT rk_batch_t rk_create_batch(
    rk_uint max_size,
    rk_batch_translation_format translation_format,
    rk_batch_orientation_format orientation_format);

//TODO: export math function and take a projection matrix instead of its parameters
RK_EXPORT void rk_set_projection(
    float hfov,
    float ratio,
    float near,
    float far);

//TODO: export math function and take a view matrix instead of its parameters
RK_EXPORT void rk_set_view(
    rk_vec3 const & position,
    rk_vec3 const & lookat);

RK_EXPORT void rk_begin_frame();

RK_EXPORT void rk_select_texture(
    rk_texture_t texture);

RK_EXPORT void rk_draw_triangles(
    rk_triangles_t triangles);

RK_EXPORT void rk_select_vertices(
    rk_vertices_t vertices);

RK_EXPORT void rk_draw_batch(
    rk_batch_t batch,
    rk_uint size,
    rk_instance_flags const * flags,
    rk_ushort const * texlevels,
    rk_mesh const * meshes,
    rk_vec3 const * translations,
    rk_vec3 const * orientations);

RK_EXPORT void rk_unselect_vertices(
    rk_vertices_t vertices);

RK_EXPORT void rk_unselect_texture(
    rk_texture_t texture);

RK_EXPORT void rk_unselect_shader(
    rk_shader_t shader);

RK_EXPORT void rk_end_frame();

RK_EXPORT void rk_destroy_batch(
    rk_batch_t batch);

RK_EXPORT void rk_destroy_triangles(
    rk_triangles_t triangles);

RK_EXPORT void rk_destroy_vertices(
    rk_vertices_t vertices);

RK_EXPORT void rk_destroy_texture(
    rk_texture_t texture);

RK_EXPORT void rk_destroy_shader(
    rk_shader_t shader);

RK_EXPORT void rk_terminate();

#endif // _RK_ENGINE_RENDER_H