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

typedef uint8_t  BYTE;

int check_header_is_jpeg();

int main(int argc, char *argv[])
{
    // check proper usage
    if (argc != 2)
    {
        fprintf(stderr, "usage: ./recover filename\n");
        return 1;
    }

    // keep filenames
    char *infile = argv[1];
    char *outfile = "000.jpg";
    FILE *inptr = fopen(infile, "r");
    FILE *outptr = fopen(outfile, "w");

    // check if files open properly
    if (inptr == NULL)
    {
        fprintf(stderr, "Could not open %s\n", infile);
        return 2;
    }
    if (outptr == NULL)
    {
        fprintf(stderr, "Could not write in %s\n", infile);
        return 3;
    }
    while (!check_header_is_jpeg(inptr))
    {
        fseek(inptr, 512, SEEK_CUR);
    }

    // only keep reading if block is proper size (512)
    while (fread(outptr, 1, 512, inptr) == 512)
    {
        check_header_is_jpeg(inptr);
        fwrite(&outptr, 512, 1, inptr);
    }

    printf("end\n");

    // close files
    fclose(inptr);
    fclose(outptr);
    return 0;
}


int check_header_is_jpeg(FILE *memcard)
{
    BYTE *BLOCKHEADER = malloc(4 * sizeof(BYTE));
    // read first 4 bytes of current memory block
    for (int i = 0; i < 4; i++)
    {
        fread(&BLOCKHEADER[i], 1, 1, memcard);
    }

    // rewind seek back to beginning of block
    fseek(memcard, -4, SEEK_CUR);

    // check if header is the same as JPEG header, return true if it is
    if (BLOCKHEADER[0] == 0xff &&
        BLOCKHEADER[1] == 0xd8 &&
        BLOCKHEADER[2] == 0xff &&
        (BLOCKHEADER[3] & 0xf0) == 0xe0)
    {
        printf("JPEG Header found!\n");
        free(BLOCKHEADER);
        return 1;
    }
    else
    {
        free(BLOCKHEADER);
        return 0;
    }
}