// OpenGL textures
// https://nehe.gamedev.net/tutorial/texture_mapping/12038/
// https://github.com/gamedev-net/nehe-opengl/blob/master/linux/lesson6/Data/lesson6/NeHe.bmp

#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <string.h>
#include "GL/glut.h"
#include "GL/gl.h"
#include "GL/glu.h"
#include <stdio.h>
#include <math.h>

GLuint texture[2];

struct Image {
    unsigned long sizeX;
    unsigned long sizeY;
    char* data;
};

typedef struct Image Image;

#define checkImageWidth 64
#define checkImageHeight 64

GLubyte checkImage[checkImageWidth][checkImageHeight][3];
void makeCheckImage(void) {
    int i, j, c;
    for (i = 0; i < checkImageWidth; i++) {
        for (j = 0; j < checkImageHeight; j++) {
            c = ((((i & 0x8) == 0) ^ ((j & 0x8) == 0))) * 255;
            checkImage[i][j][0] = (GLubyte)c;
            checkImage[i][j][1] = (GLubyte)c;
            checkImage[i][j][2] = (GLubyte)c;
        }
    }
}

int ImageLoad(char* filename, Image* image) {
    FILE* file;
    unsigned long size; // size of the image in bytes.
    unsigned long i; // standard counter.
    unsigned short int planes; // number of planes in image (must be 1)
    unsigned short int bpp; // number of bits per pixel (must be 24)
    char temp; // temporary color storage for bgr-rgb conversion.
    // make sure the file is there.
    if ((file = fopen(filename, "rb")) == NULL) {
        printf("File Not Found : %s\n", filename);
        return 0;
    }
    // seek through the bmp header, up to the width/height:
    fseek(file, 18, SEEK_CUR);
    // read the width
    if ((i = fread(&image->sizeX, 4, 1, file)) != 1) {
        printf("Error reading width from %s.\n", filename);
        return 0;
    }
    //printf("Width of %s: %lu\n", filename, image->sizeX);
    // read the height
    if ((i = fread(&image->sizeY, 4, 1, file)) != 1) {
        printf("Error reading height from %s.\n", filename);
        return 0;
    }
    //printf("Height of %s: %lu\n", filename, image->sizeY);
    // calculate the size (assuming 24 bits or 3 bytes per pixel).
    size = image->sizeX * image->sizeY * 3;
    // read the planes
    if ((fread(&planes, 2, 1, file)) != 1) {
        printf("Error reading planes from %s.\n", filename);
        return 0;
    }
    if (planes != 1) {
        printf("Planes from %s is not 1: %u\n", filename, planes);
        return 0;
    }
    // read the bitsperpixel
    if ((i = fread(&bpp, 2, 1, file)) != 1) {
        printf("Error reading bpp from %s.\n", filename);
        return 0;
    }
    if (bpp != 24) {
        printf("Bpp from %s is not 24: %u\n", filename, bpp);
        return 0;
    }
    // seek past the rest of the bitmap header.
    fseek(file, 24, SEEK_CUR);
    // read the data.
    image->data = (char*)malloc(size);
    if (image->data == NULL) {
        printf("Error allocating memory for color-corrected image data");
        return 0;
    }
    if ((i = fread(image->data, size, 1, file)) != 1) {
        printf("Error reading image data from %s.\n", filename);
        return 0;
    }
    for (i = 0; i < size; i += 3) { // reverse all of the colors. (bgr -> rgb)
        temp = image->data[i];
        image->data[i] = image->data[i + 2];
        image->data[i + 2] = temp;
    }
    // we're done.
    return 1;
}

Image* loadTexture() {
    Image* image1;
    // allocate space for texture
    image1 = (Image*)malloc(sizeof(Image));
    if (image1 == NULL) {
        printf("Error allocating space for image");
        exit(0);
    }
    if (!ImageLoad((char*)"Data/NeHe.bmp", image1)) {
        exit(1);
    }
    return image1;
}

void myinit(void)
{
    glClearColor(0.5, 0.5, 0.5, 0.0);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    Image* image1 = loadTexture();
    if (image1 == NULL) {
        printf("Image was not returned from loadTexture\n");
        exit(0);
    }
    makeCheckImage();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    // Create Texture
    glGenTextures(2, texture);
    glBindTexture(GL_TEXTURE_2D, texture[0]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //scale linearly when image bigger than texture
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); //scale linearly when image smalled than texture
    glTexImage2D(GL_TEXTURE_2D, 0, 3, image1->sizeX, image1->sizeY, 0,
        GL_RGB, GL_UNSIGNED_BYTE, image1->data);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glBindTexture(GL_TEXTURE_2D, texture[1]);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glTexImage2D(GL_TEXTURE_2D, 0, 3, checkImageWidth,
        checkImageHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, &checkImage[0][0][0]);
    glEnable(GL_TEXTURE_2D);
    glShadeModel(GL_FLAT);
}

void display(void) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glBindTexture(GL_TEXTURE_2D, texture[1]);
    glutSolidTeapot(1.0);
    glBindTexture(GL_TEXTURE_2D, texture[0]);
    glBegin(GL_QUADS);
    glTexCoord2f(0.0, 0.0);
    glVertex3f(1.0, -1.0, 0.0);
    glTexCoord2f(1.0, 0.0);
    glVertex3f(1.0, 1.0, 0.0);
    glTexCoord2f(1.0, 1.0);
    glVertex3f(2.41421, 1.0, -1.41421);
    glTexCoord2f(0.0, 1.0);
    glVertex3f(2.41421, -1.0, -1.41421);
    glEnd();
    glutSwapBuffers();
}

void myReshape(int w, int h) {
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0, 1.0 * (GLfloat)w / (GLfloat)h, 1.0, 30.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -3.6);
}

void keyboard(unsigned char key, int x, int y) {
    switch (key) {
    case 27: // “esc” on keyboard
        exit(0);
        break;
    default: // “a” on keyboard
        break;
    }
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutCreateWindow("Texture Mapping - Programming Techniques");
    myinit();
    glutReshapeFunc(myReshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboard);
    glutMainLoop();
    return 0;
}