// 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_OPENGLES_H
#define _RK_ENGINE_RENDER_OPENGLES_H

#include "../types.hpp"
#include "../math.hpp"
#include <GLES3/gl32.h>
#include <GLES3/gl3ext.h>
#include <GLES3/gl3platform.h>

struct rk_shader {
    GLuint vertex;
    GLuint fragment;
    GLuint program;
};

struct rk_texture {
    unsigned nlevels;
    GLuint texture;
};

struct rk_triangles {
    unsigned size;
    GLuint array;
    GLuint vertices;
};

struct rk_vertices {
    unsigned nvertices;
    unsigned nindices;
    unsigned nmeshes;
    rk_vertex_format * format;
    rk_ubyte * vertices;
    rk_vertex_index * indices;
    rk_mesh * meshes;
    GLuint vertices_buffer;
    GLuint indices_buffer;
};

struct rk_command {
    GLuint nvertices;
    GLuint ninstances;
    GLuint base_index;
    GLint base_vertex;
    GLuint base_instance;
};

// param output types must be size compatible with an array of rk_param_output
typedef rk_uint rk_param_output;

#define RK_CHECK_PARAM_OUTPUT_TYPE(_t) static_assert(!(sizeof(_t) % sizeof(rk_param_output)))

struct rk_vec3_float {
    float x;
    float y;
    float z;
};

static_assert(sizeof(rk_vec3_float) == sizeof(rk_vec3));

struct rk_vec3_short {
    rk_short x;
    rk_short y;
    rk_short z;
    rk_short pad;
};

typedef rk_int rk_vec3_int10;
typedef rk_uint rk_vec3_uint10;

struct rk_mat3_float {
    rk_vec3_float x;
    rk_vec3_float y;
    rk_vec3_float z;
};

static_assert(sizeof(rk_mat3_float) == sizeof(rk_mat3));

struct rk_mat3_int10 {
    rk_vec3_int10 x;
    rk_vec3_int10 y;
    rk_vec3_int10 z;
};

RK_CHECK_PARAM_INPUT_TYPE(rk_vec3_float);
RK_CHECK_PARAM_INPUT_TYPE(rk_mat3_float);

RK_CHECK_PARAM_OUTPUT_TYPE(rk_vec3_float);
RK_CHECK_PARAM_OUTPUT_TYPE(rk_vec3_short);
RK_CHECK_PARAM_OUTPUT_TYPE(rk_vec3_int10);
RK_CHECK_PARAM_OUTPUT_TYPE(rk_vec3_uint10);
RK_CHECK_PARAM_OUTPUT_TYPE(rk_mat3_float);
RK_CHECK_PARAM_OUTPUT_TYPE(rk_mat3_int10);

typedef void (*rk_packer)(
    unsigned const, // count
    rk_instance_index const * const, // indices
    rk_param_output *, // dst
    rk_param_input const * const); // src

struct rk_parameter {
    mutable bool dirty;
    unsigned binding;
    unsigned offset;
    unsigned src_size;
    unsigned dst_size;
    unsigned src_len;
    unsigned dst_len;
    rk_param_input * source;
    rk_packer packer;
};

struct rk_bucket {
    unsigned size;
    unsigned count;
    rk_instance_index * indices;
};

enum rk_batch_state {
    RK_BATCH_STATE_EMPTY = 0,
    RK_BATCH_STATE_FILLED = 1,
    RK_BATCH_STATE_SORTED = 2,
    RK_BATCH_STATE_PACKED = 3
};

struct rk_batch {
    mutable rk_batch_state state;
    mutable unsigned count;
    mutable unsigned ninstances;
    mutable unsigned ncommands;
    unsigned max_size;
    unsigned nparams;
    rk_vertices const * vertices;
    rk_instance_flags * flags;
    rk_mesh_index * meshes;
    rk_instance_index * indices;
    rk_command * commands;
    rk_parameter * params;
    GLuint vertex_array;
    GLuint commands_buffer;
    GLuint params_buffer;
};

#endif // _RK_ENGINE_RENDER_OPENGLES_H