//
// Created by lukas on 05.02.22.
//
#define GL_GLEXT_PROTOTYPES
#include <cstdio>
#include <GL/gl.h>
#include <GL/glext.h>
#include "bmploader.h"

unsigned bmploader::loadBMP(const char *imagepath) {
    // Data read from the header of the BMP file
    unsigned char header[54]; // Each BMP file begins by a 54-bytes header
    unsigned int dataPos;     // Position in the file where the actual data begins
    int width, height;
    unsigned int imageSize;   // = width*height*3
    // Actual RGB data
    unsigned char * data;


    // Open the file
    FILE * file = fopen(imagepath,"rb");
    if (!file){printf("Image could not be opened\n"); return 0;}

    if ( fread(header, 1, 54, file)!=54 ){ // If not 54 bytes read : problem
        printf("Not a correct BMP file\n");
        return false;
    }

    if ( header[0]!='B' || header[1]!='M' ){
        printf("Not a correct BMP file\n");
        return 0;
    }

    // Read ints from the byte array
    dataPos    = *(int*)&(header[0x0A]);
    imageSize  = *(int*)&(header[0x22]);
    width      = *(int*)&(header[0x12]);
    height     = *(int*)&(header[0x16]);

    // Some BMP files are misformatted, guess missing information
    if (imageSize==0)    imageSize=width*height*3; // 3 : one byte for each Red, Green and Blue component
    if (dataPos==0)      dataPos=54; // The BMP header is done that way

    // Create a buffer
    data = new unsigned char [imageSize];

    // Read the actual data from the file into the buffer
    fread(data,1,imageSize,file);

    //Everything is in memory now, the file can be closed
    fclose(file);

    glEnable(GL_TEXTURE_2D);

    // Create one OpenGL texture
    unsigned textureID;
    glGenTextures(1, &textureID);
    glActiveTexture(GL_TEXTURE0);
    // "Bind" the newly created texture : all future texture functions will modify this texture
    glBindTexture(GL_TEXTURE_2D, textureID);


    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    // Give the image to OpenGL
    glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
    // Generate mipmaps, by the way.
    glGenerateMipmap(GL_TEXTURE_2D);



    return textureID;
}