/* Freetype GL - A C OpenGL Freetype engine
 *
 * Distributed under the OSI-approved BSD 2-Clause License.  See accompanying
 * file `LICENSE` for more details.
 */
#include <stdio.h>
#include <string.h>
#include "freetype-gl.h"
#include "vertex-buffer.h"
#include "shader.h"
#include "mat4.h"
#include "screenshot-util.h"

#include <GLFW/glfw3.h>


// ------------------------------------------------------- typedef & struct ---
typedef struct {
    float x, y, z;    // position
    float s, t;       // texture
    float r, g, b, a; // color
} vertex_t;


// ------------------------------------------------------- global variables ---
texture_atlas_t * atlas;
texture_font_t * font;
vertex_buffer_t * buffer;
char *text =
    "A Quick Brown Fox Jumps Over The Lazy Dog 0123456789 "
    "A Quick Brown Fox Jumps Over The Lazy Dog 0123456789 ";
int line_count = 42;
GLuint shader;
mat4   model, view, projection;


// --------------------------------------------------------------- add_text ---
void add_text( vertex_buffer_t * buffer, texture_font_t * font,
               char *text, vec4 * color, vec2 * pen )
{
    size_t i;
    float r = color->red, g = color->green, b = color->blue, a = color->alpha;
    for( i = 0; i < strlen(text); ++i )
    {
        texture_glyph_t *glyph = texture_font_get_glyph( font, text + i );
        if( glyph != NULL )
        {
            float kerning = 0.0f;
            if( i > 0)
            {
                kerning = texture_glyph_get_kerning( glyph, text + i - 1 );
            }
            pen->x += kerning;
            int x0  = (int)( pen->x + glyph->offset_x );
            int y0  = (int)( pen->y + glyph->offset_y );
            int x1  = (int)( x0 + glyph->width );
            int y1  = (int)( y0 - glyph->height );
            float s0 = glyph->s0;
            float t0 = glyph->t0;
            float s1 = glyph->s1;
            float t1 = glyph->t1;
            GLuint index = buffer->vertices->size;
            GLuint indices[] = {index, index+1, index+2,
                                index, index+2, index+3};
            vertex_t vertices[] = { { x0,y0,0,  s0,t0,  r,g,b,a },
                                    { x0,y1,0,  s0,t1,  r,g,b,a },
                                    { x1,y1,0,  s1,t1,  r,g,b,a },
                                    { x1,y0,0,  s1,t0,  r,g,b,a } };
            vertex_buffer_push_back_indices( buffer, indices, 6 );
            vertex_buffer_push_back_vertices( buffer, vertices, 4 );
            pen->x += glyph->advance_x;
        }
    }
}


// ------------------------------------------------------------------- init ---
void init( void )
{
    size_t i;
    vec2 pen = {{0,0}};
    vec4 color = {{0,0,0,1}};

    atlas  = texture_atlas_new( 512, 512, 1 );
    font = texture_font_new_from_file( atlas, 12, "fonts/VeraMono.ttf" );
    buffer = vertex_buffer_new( "vertex:3f,tex_coord:2f,color:4f" );

    pen.y = -font->descender;
    for( i=0; i<line_count; ++i )
    {
        pen.x = 10.0;
        add_text( buffer, font, text, &color, &pen );
        pen.y += font->height - font->linegap;
    }

    glClearColor( 1.0, 1.0, 1.0, 1.0 );
    glDisable( GL_DEPTH_TEST );
    glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
    glEnable( GL_TEXTURE_2D );
    glEnable( GL_BLEND );

    glGenTextures( 1, &atlas->id );
    glBindTexture( GL_TEXTURE_2D, atlas->id );
    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_MAG_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RED, atlas->width, atlas->height,
                  0, GL_RED, GL_UNSIGNED_BYTE, atlas->data );

    shader = shader_load("shaders/v3f-t2f-c4f.vert",
                         "shaders/v3f-t2f-c4f.frag");
    mat4_set_identity( &projection );
    mat4_set_identity( &model );
    mat4_set_identity( &view );
}


// ---------------------------------------------------------------- display ---
void display( GLFWwindow* window )
{
    static int frame=0;
    static int count = 0;
    static double time;

    if( count == 0 && frame == 0 )
    {
        printf(
            "Computing FPS with text generation and rendering at each frame...\n" );
        printf(
            "Number of glyphs: %d\n", (int)strlen(text)*line_count );
    }

    frame++;
    time = glfwGetTime( );

    if( time > 2.5 )
    {
        printf( "FPS : %.2f (%d frames in %.2f second, %.1f glyph/second)\n",
                frame/time, frame, time,
                frame/time * strlen(text)*line_count );
        glfwSetTime( 0.0 );
        frame = 0;
        ++count;
        if( count == 5 )
        {
            printf( "\nComputing FPS with text rendering at each frame...\n" );
            printf( "Number of glyphs: %d\n", (int)strlen(text)*line_count );
        }
        if( count > 9 )
        {
            glfwSetWindowShouldClose( window, GL_TRUE );
        }
    }
    if( count < 5 )
    {
        size_t i;
        vec4 color = {{0,0,0,1}};
        vec2 pen = {{0,0}};
        vertex_buffer_clear( buffer );

        pen.y = -font->descender;
        for( i=0; i<line_count; ++i )
        {
            pen.x = 10.0;
            add_text( buffer, font, text, &color, &pen );
            pen.y += font->height - font->linegap;
        }
    }
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    glBindTexture( GL_TEXTURE_2D, atlas->id );

    glUseProgram( shader );
    {
        glUniform1i( glGetUniformLocation( shader, "texture" ),
                     0 );
        glUniformMatrix4fv( glGetUniformLocation( shader, "model" ),
                            1, 0, model.data);
        glUniformMatrix4fv( glGetUniformLocation( shader, "view" ),
                            1, 0, view.data);
        glUniformMatrix4fv( glGetUniformLocation( shader, "projection" ),
                            1, 0, projection.data);
        vertex_buffer_render( buffer, GL_TRIANGLES );
    }

    glfwSwapBuffers( window );
}


// ---------------------------------------------------------------- reshape ---
void reshape( GLFWwindow* window, int width, int height )
{
    glViewport(0, 0, width, height);
    mat4_set_orthographic( &projection, 0, width, 0, height, -1, 1);
}


// --------------------------------------------------------------- keyboard ---
void keyboard( GLFWwindow* window, int key, int scancode, int action, int mods )
{
    if ( key == GLFW_KEY_ESCAPE && action == GLFW_PRESS )
    {
        glfwSetWindowShouldClose( window, GL_TRUE );
    }
}


// --------------------------------------------------------- error-callback ---
void error_callback( int error, const char* description )
{
    fputs( description, stderr );
}


// ------------------------------------------------------------------- main ---
int main( int argc, char **argv )
{
    GLFWwindow* window;
    char* screenshot_path = NULL;

    if (argc > 1)
    {
        if (argc == 3 && 0 == strcmp( "--screenshot", argv[1] ))
            screenshot_path = argv[2];
        else
        {
            fprintf( stderr, "Unknown or incomplete parameters given\n" );
            exit( EXIT_FAILURE );
        }
    }

    glfwSetErrorCallback( error_callback );

    if (!glfwInit( ))
    {
        exit( EXIT_FAILURE );
    }

    glfwWindowHint( GLFW_VISIBLE, GL_FALSE );
    glfwWindowHint( GLFW_RESIZABLE, GL_FALSE );

    window = glfwCreateWindow( 800, 600, argv[0], NULL, NULL );

    if (!window)
    {
        glfwTerminate( );
        exit( EXIT_FAILURE );
    }

    glfwMakeContextCurrent( window );
    glfwSwapInterval( 0 ); // disable V-SYNC

    glfwSetFramebufferSizeCallback( window, reshape );
    glfwSetWindowRefreshCallback( window, display );
    glfwSetKeyCallback( window, keyboard );

#ifndef __APPLE__
    glewExperimental = GL_TRUE;
    GLenum err = glewInit();
    if (GLEW_OK != err)
    {
        /* Problem: glewInit failed, something is seriously wrong. */
        fprintf( stderr, "Error: %s\n", glewGetErrorString(err) );
        exit( EXIT_FAILURE );
    }
    fprintf( stderr, "Using GLEW %s\n", glewGetString(GLEW_VERSION) );
#endif

    init();

    glfwShowWindow( window );
    reshape( window, 800, 600 );

    glfwSetTime(0.0);

    while (!glfwWindowShouldClose( window ))
    {
        display( window );
        glfwPollEvents( );

        if (screenshot_path)
        {
            screenshot( window, screenshot_path );
            glfwSetWindowShouldClose( window, 1 );
        }
    }

    glDeleteTextures( 1, &atlas->id );
    atlas->id = 0;
    texture_atlas_delete( atlas );

    glfwDestroyWindow( window );
    glfwTerminate( );

    return EXIT_SUCCESS;
}