/*
 * Mr. 4th Dimention - Allen Webster
 *
 * 10.11.2017
 *
 * OpenGL render implementation
 *
 */

// TOP

//#define GL_FUNC(N,R,P) typedef R (N##_Function) P; N##_Function *P = 0;
//#include "4ed_opengl_funcs.h"
#include "4ed_opengl_defines.h"

#if 0
internal GLuint
gl__texture_initialize(GLint tex_width, GLint tex_height, u32 *pixels){
    GLuint tex;
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, tex_width, tex_height, 0, GL_RED, GL_UNSIGNED_INT, pixels);
    return(tex);
}
#endif

internal u32
gl__get_gpu_texture(Vec3_i32 dim, Texture_Kind texture_kind){
    u32 tex;
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAX_LEVEL, 0);
    glTexStorage3D(GL_TEXTURE_2D_ARRAY, 0, GL_R8, dim.x, dim.y, 0, GL_RED, GL_UNSIGNED_INT, 0);
    return(tex);
}

internal void
gl__draw_bind_texture(Render_Target *t, i32 texid){
    if (t->bound_texture != texid){
        glBindTexture(GL_TEXTURE_2D, texid);
        t->bound_texture = texid;
    }
}

internal void CALL_CONVENTION
gl__error_callback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, char *message, void *userParam){
    InvalidPath;
}

char *gl__header = R"foo(#version 150
)foo";

char *gl__vertex = R"foo(
uniform vec2 view_t;
uniform mat2x2 view_m;
 uniform vec4 color;
in vec2 vertex_p;
in vec2 vertex_t;
smooth out vec4 fragment_color;
smooth out vec2 uv;
void main(void)
{
gl_Position = vec4(view_m*(vertex_p - view_t), 0.f, 1.f);
fragment_color = color;
uv = vertex_t;
}
)foo";

char *gl__fragment = R"foo(
smooth in vec4 fragment_color;
smooth in vec2 uv;
uniform sampler2D sampler;
uniform float texture_override;
out vec4 out_color;
void main(void)
{
out_color = fragment_color*(texture(sampler, uv).r + texture_override);
}
)foo";

#define AttributeList(X) \
X(vertex_p) \
X(vertex_t)

#define UniformList(X) \
X(view_t) \
X(view_m) \
X(color) \
X(sampler) \
X(texture_override)

struct GL_Program{
    u32 program;
#define GetAttributeLocation(N) i32 N;
    AttributeList(GetAttributeLocation)
#undef GetAttributeLocation
#define GetUniformLocation(N) i32 N;
        UniformList(GetUniformLocation)
#undef GetUniformLocation
};

internal GL_Program
gl__make_program(char *header, char *vertex, char *fragment){
    if (header == 0){
        header = "";
    }
    
    GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    GLchar *vertex_source_array[] = { header, vertex };
    glShaderSource(vertex_shader, ArrayCount(vertex_source_array), vertex_source_array, 0);
    glCompileShader(vertex_shader);
    
    GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    GLchar *fragment_source_array[] = { header, fragment };
    glShaderSource(fragment_shader, ArrayCount(fragment_source_array), fragment_source_array, 0);
    glCompileShader(fragment_shader);
    
    GLuint program = glCreateProgram();
    glAttachShader(program, vertex_shader);
    glAttachShader(program, fragment_shader);
    glLinkProgram(program);
    glValidateProgram(program);
    
    GLint success = false;
    glGetProgramiv(program, GL_LINK_STATUS, &success);
    if (!success){
        GLsizei ignore = 0;
        char vertex_errors[KB(4)];
        char fragment_errors[KB(4)];
        char program_errors[KB(4)];
        glGetShaderInfoLog(vertex_shader, sizeof(vertex_errors), &ignore, vertex_errors);
        glGetShaderInfoLog(fragment_shader, sizeof(fragment_errors), &ignore, fragment_errors);
        glGetProgramInfoLog(program, sizeof(program_errors), &ignore, program_errors);
#if SHIP_MODE
        os_popup_window(string_u8_litexpr("Error"), string_u8_litexpr("Shader compilation failed."));
#endif
        InvalidPath;
    }
    
    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);
    
    GL_Program result = {};
    result.program = program;
#define GetAttributeLocation(N) result.N = glGetAttribLocation(program, #N);
    AttributeList(GetAttributeLocation)
#undef GetAttributeLocation
#define GetUniformLocation(N) result.N = glGetUniformLocation(program, #N);
        UniformList(GetUniformLocation)
#undef GetUniformLocation
        return(result);
}

#define GLOffset(p,m) ((void*)(OffsetOfMemberStruct(p,m)))

internal void
gl_render(Render_Target *t, Arena *scratch){
    local_persist b32 first_opengl_call = true;
    local_persist u32 attribute_buffer = 0;
    local_persist GL_Program gpu_program = {};
    
    if (first_opengl_call){
        first_opengl_call = false;
        
#if !SHIP_MODE
        glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
        glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION, 0, 0, true);
        glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_LOW, 0, 0, true);
        glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_MEDIUM, 0, 0, true);
        glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_HIGH, 0, 0, true);
        glDebugMessageCallback(gl__error_callback, 0);
#endif
        
        ////////////////////////////////
        
        GLuint dummy_vao = 0;
        glGenVertexArrays(1, &dummy_vao);
        glBindVertexArray(dummy_vao);
        
        ////////////////////////////////
        
        glGenBuffers(1, &attribute_buffer);
        glBindBuffer(GL_ARRAY_BUFFER, attribute_buffer);
        
        ////////////////////////////////
        
        glEnable(GL_SCISSOR_TEST);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        
        ////////////////////////////////
        
        gpu_program = gl__make_program(gl__header, gl__vertex, gl__fragment);
        glUseProgram(gpu_program.program);
    }
    
    i32 width = t->width;
    i32 height = t->height;
    
    glViewport(0, 0, width, height);
    glScissor(0, 0, width, height);
    glClearColor(1.f, 0.f, 1.f, 1.f);
    glClear(GL_COLOR_BUFFER_BIT);
    
    glBindTexture(GL_TEXTURE_2D, 0);
    t->bound_texture = 0;
    
    for (Render_Free_Texture *free_texture = t->free_texture_first;
         free_texture != 0;
         free_texture = free_texture->next){
        glDeleteTextures(1, &free_texture->tex_id);
    }
    t->free_texture_first = 0;
    t->free_texture_last = 0;
    
    u8 *start = (u8*)t->buffer.base;
    u8 *end = (u8*)t->buffer.base + t->buffer.pos;
    Render_Command_Header *header = 0;
    for (u8 *p = start; p < end; p += header->size){
        header = (Render_Command_Header*)p;
        
        i32 type = header->type;
        switch (type){
            case RenCom_Rectangle:
            {
                Render_Command_Rectangle *rectangle = (Render_Command_Rectangle*)header;
                gl__draw_bind_texture(t, 0);
                
                Vec4 c = unpack_color4(rectangle->color);
                
                i32 vertex_count = ArrayCount(rectangle->vertices);
                glBufferData(GL_ARRAY_BUFFER, sizeof(rectangle->vertices), rectangle->vertices, GL_STREAM_DRAW);
                glEnableVertexAttribArray(gpu_program.vertex_p);
                glVertexAttribPointer(gpu_program.vertex_p, 2, GL_FLOAT, true, sizeof(rectangle->vertices[0]), 0);
                
                glUniform2f(gpu_program.view_t, width/2.f, height/2.f);
                f32 m[4] = {
                    2.f/width, 0.f,
                    0.f, -2.f/height,
                };
                glUniformMatrix2fv(gpu_program.view_m, 1, GL_FALSE, m);
                glUniform4f(gpu_program.color, c.r, c.g, c.b, c.a);
                glUniform1f(gpu_program.texture_override, 1.f);
                
                glDrawArrays(GL_TRIANGLE_STRIP, 0, vertex_count);
                glDisableVertexAttribArray(gpu_program.vertex_p);
            }break;
            
            case RenCom_Glyph:
            {
                Render_Command_Glyph *glyph = (Render_Command_Glyph*)header;
#if 0
                Font_Pointers font = system_font_get_pointers_by_id(glyph->font_id);
                if (!font.valid){
                    break;
                }
#endif
                Face *face = 0;
                if (face == 0){
                    break;
                }
                
                u32 codepoint = glyph->codepoint;
                
#if 0                
                u32 page_number = codepoint/GLYPHS_PER_PAGE;
                Glyph_Page *page = font_cached_get_page(font.pages, page_number);
                if (page == 0){
                    break;
                }
                
                if (!page->has_gpu_setup){
                    Temp_Memory temp = begin_temp(scratch);
                    i32 tex_width = 0;
                    i32 tex_height = 0;
                    u32 *pixels = font_load_page_pixels(scratch, font.settings, page, page_number, &tex_width, &tex_height);
                    page->has_gpu_setup = true;
                    page->gpu_tex = gl__texture_initialize(tex_width, tex_height, pixels);
                    end_temp(temp);
                }
                if (page->gpu_tex == 0){
                    break;
                }
                
                u32 glyph_index = codepoint%GLYPHS_PER_PAGE;
                Glyph_Bounds bounds = page->glyphs[glyph_index];
                GLuint tex = page->gpu_tex;
                i32 tex_width = page->tex_width;
                i32 tex_height = page->tex_height;
                
                // TODO(allen): do(think about baking unit_u/unit_v into font data)
                f32 unit_u = 1.f/tex_width;
                f32 unit_v = 1.f/tex_height;
#else
                
                u16 glyph_index = 0;
                if (!table_read(&face->codepoint_to_index_table, codepoint, &glyph_index)){
                    glyph_index = 0;
                }
                Glyph_Bounds bounds = face->bounds[glyph_index];
                GLuint tex = face->gpu_texture;
                Vec3_f32 gpu_texture_dim = face->gpu_texture_dim;
#endif
                
                f32 x = glyph->pos.x;
                f32 y = glyph->pos.y;
                
                f32_Rect uv = Rf32(bounds.uv.x0, bounds.uv.y0,
                                   bounds.uv.x1, bounds.uv.y1);
                f32_Rect xy = Rf32(x + bounds.xy_off.x0, y + bounds.xy_off.y0,
                                   x + bounds.xy_off.x1, y + bounds.xy_off.y1);
                
                struct Textutred_Vertex{
                    Vec2 xy;
                    Vec2 uv;
                };
                
                Textutred_Vertex vertices[4];
                if (!HasFlag(glyph->flags, GlyphFlag_Rotate90)){
                    vertices[0].xy = V2(xy.x0, xy.y1); vertices[0].uv = V2(uv.x0, uv.y1);
                    vertices[1].xy = V2(xy.x1, xy.y1); vertices[1].uv = V2(uv.x1, uv.y1);
                    vertices[2].xy = V2(xy.x0, xy.y0); vertices[2].uv = V2(uv.x0, uv.y0);
                    vertices[3].xy = V2(xy.x1, xy.y0); vertices[3].uv = V2(uv.x1, uv.y0);
                }
                else{
                    vertices[0].xy = V2(xy.x0, xy.y1); vertices[0].uv = V2(uv.x1, uv.y1);
                    vertices[1].xy = V2(xy.x1, xy.y1); vertices[1].uv = V2(uv.x1, uv.y0);
                    vertices[2].xy = V2(xy.x0, xy.y0); vertices[2].uv = V2(uv.x0, uv.y1);
                    vertices[3].xy = V2(xy.x1, xy.y0); vertices[3].uv = V2(uv.x0, uv.y0);
                }
                
                gl__draw_bind_texture(t, tex);
                
                Vec4 c = unpack_color4(glyph->color);
                
                i32 vertex_count = ArrayCount(vertices);
                glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STREAM_DRAW);
                glEnableVertexAttribArray(gpu_program.vertex_p);
                glEnableVertexAttribArray(gpu_program.vertex_t);
                glVertexAttribPointer(gpu_program.vertex_p, 2, GL_FLOAT, true, sizeof(vertices[0]), GLOffset(&vertices[0], xy));
                glVertexAttribPointer(gpu_program.vertex_t, 2, GL_FLOAT, true, sizeof(vertices[0]), GLOffset(&vertices[0], uv));
                
                glUniform2f(gpu_program.view_t, width/2.f, height/2.f);
                f32 m[4] = {
                    2.f/width, 0.f,
                    0.f, -2.f/height,
                };
                glUniformMatrix2fv(gpu_program.view_m, 1, GL_FALSE, m);
                glUniform4f(gpu_program.color, c.r, c.g, c.b, c.a);
                
                glUniform1i(gpu_program.sampler, 0);
                glUniform1f(gpu_program.texture_override, 0.f);
                
                glDrawArrays(GL_TRIANGLE_STRIP, 0, vertex_count);
                glDisableVertexAttribArray(gpu_program.vertex_p);
                glDisableVertexAttribArray(gpu_program.vertex_t);
                
#if 0
                if (codepoint != ' ' && font.settings->parameters.underline){
                    // TODO(allen): recover this feature
                    glDisable(GL_TEXTURE_2D);
                    
                    f32 x0 = x;
                    f32 x1 = x + page->advance[glyph_index];
                    f32 yoff1 = y + font.metrics->underline_yoff1;
                    f32 yoff2 = y + font.metrics->underline_yoff2;
                    
                    glBegin(GL_QUADS);
                    {
                        glVertex2f(x0, yoff1);
                        glVertex2f(x1, yoff1);
                        glVertex2f(x1, yoff2);
                        glVertex2f(x0, yoff2);
                    }
                    glEnd();
                    
                    glEnable(GL_TEXTURE_2D);
                }
#endif
            }break;
            
            case RenCom_ChangeClip:
            {
                Render_Command_Change_Clip *clip = (Render_Command_Change_Clip*)header;
                i32_Rect box = clip->box;
                glScissor(box.x0, height - box.y1, box.x1 - box.x0, box.y1 - box.y0);
            }break;
        }
    }
    
    if (target.out_of_memory){
        glScissor(0, 0, width, height);
        glClearColor(0.f, 1.f, 0.f, 1.f);
        glClear(GL_COLOR_BUFFER_BIT);
        target.out_of_memory = false;
    }
    
    glFlush();
}

// BOTTOM