#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#pragma pack(push, 1)

typedef struct bmpHeader{
    uint16_t bfType;
    uint32_t bfSize, bfReserved, bfOffBits;
}bmpHeader;

typedef struct bmpInfoHeader{
    uint32_t biSize,biWidth,biHeight;
    uint16_t biPlanes,biBitCount;
    uint32_t biCompression, biSizeImage, biPelsPerMeter[2], biClrUsed, biClrImportant;
}bmpInfoHeader;

typedef  struct pixel{
    unsigned char B;
    unsigned char G;
    unsigned char R;
}pixel;

#pragma pack(pop)

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("%s <input.bmp> <offset> \n", argv[0]);
        exit(1);
    }
    FILE *input ;
    input = fopen(argv[1], "rb");
    FILE *output;
    if (input == NULL) {
        exit(1);
    }
    if (argv[3] != NULL ) {
        output = fopen(argv[3], "wb");
    } else {
        output = fopen("NewBMP.bmp", "wb");
    }
    int offset = atoi(argv[2]);
    bmpHeader header;
    bmpInfoHeader infoHeader;
    fread(&header, sizeof(header), 1, input);
    fread(&infoHeader, sizeof(infoHeader), 1, input);

    pixel *pixBuff = malloc(header.bfSize - header.bfOffBits);
    pixel *offsetBuff = malloc(sizeof(pixel) * (abs(offset)));

    fread(pixBuff, sizeof(pixel), (infoHeader.biWidth*infoHeader.biHeight), input);

    if (offset>=0) {

        for (int x = 0; x < infoHeader.biHeight; x++) {
            for (int y = infoHeader.biWidth; y > (infoHeader.biWidth-offset)  ; y--) {
                offsetBuff[infoHeader.biWidth - y] = pixBuff[x * infoHeader.biWidth + y -1];
            }
            for (int y = infoHeader.biWidth; y >offset  ; y--) {
                pixBuff[x * infoHeader.biWidth + y -1].R = pixBuff[x * infoHeader.biWidth + y - offset -1].R ;
            }
            for (int y = 0; y < offset  ; y++) {
                pixBuff[x * infoHeader.biWidth + y  ].R = offsetBuff[offset-y].R ;
            }
        }
    } else{
        offset = abs(offset);
        for (int x = 0; x < infoHeader.biHeight; x++) {
            for (int y = 0; y < offset  ; y++) {
                offsetBuff[y] = pixBuff[x * infoHeader.biWidth + y ];
            }
            for (int y = 0; y <infoHeader.biWidth -offset  ; y++) {
                pixBuff[x * infoHeader.biWidth + y ].R = pixBuff[x * infoHeader.biWidth + y + offset].R ;
            }
            for (int y = infoHeader.biWidth-offset; y < infoHeader.biWidth  ; y++) {
                pixBuff[x * infoHeader.biWidth + y  ].R = offsetBuff[y - infoHeader.biWidth + offset].R ;
            }
        }
    }

    fwrite(&header, sizeof(header),1,output);
    fwrite(&infoHeader, sizeof(infoHeader),1,output);
    fwrite(pixBuff, sizeof(pixel), (infoHeader.biWidth*infoHeader.biHeight),output);

    fclose(output);
    fclose(input);

    return 0;
}