/*
 * Gumshoe_NLA.cpp
 *
 * Guidelines:
 * To open the file for reading: FILE *fp = fopen(filename, "r"); the mystery.raw file is only going to be read,
 *      so it only needs the "r" flag.
 * Extracted files should follow Name_ImageX.jpg, where X starts at 0 and increments and Name is your last name.
 *
 *
 *  Created on: Nov 5, 2010
 *      Author: NLA
 */

#include "Gumshoe_NLA.h"

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

#define BUFFSIZE 512
#define SIGLENGTH 4

void printUsage() { // Print out a message for the user to indicate proper program usage.
    printf("\nValid usage: Gumshoe_NLA.exe [File] , where");
    printf("\n\t[File] is the name of the file (in the same directory as Gumshoe_NLA) that will be searched for JPEGs.");
    printf("\n\nPlease re-run the program and try again.");
}

// Checks to see if an improper number of arguments was passed.
void processCommandLine(int argc, char *argv[]) {
    if (argc != 2) {
        printf("\n");
        fprintf(stderr, "Improper number of parameters passed. ");
        printf("Printing program syntax information.\n");
        printUsage();
        exit(1);
    }
}

int compareFirstFourBytes (char first[], char second[]) {
    int i = 0;
    for (i = 0; i < SIGLENGTH; i++) {
        if (first[i] != second [i])
            return 0;
    }

    return 1;

}

int main(int argc, char *argv[]) {

    int numRead; // Int number of bytes read from the rawFile.
    int numExtracted = 0; // Number of extracted JPEGs from file.
    char rawFileBuffer[BUFFSIZE]; // Buffer that holds incremental 512 bytes from the rawFile.
    char rawFileFirstFourBytes[SIGLENGTH]; // The first four bytes of the incremental 512 bytes buffer.

    // Signatures of JPEG files: 0xFF 0xD8 0XFF 0xE0 or 0xFF 0xD8 0xFF 0XE1

    // Char arrays that hold the signatures of essentially all JPEG files.
    char jpegSigOne[SIGLENGTH];
    (jpegSigOne[0] = 0xff); (jpegSigOne[1] = 0xd8); (jpegSigOne[2] = 0xff); (jpegSigOne[3] = 0xe0);
    char jpegSigTwo[SIGLENGTH];
    (jpegSigTwo[0] = 0xff); (jpegSigTwo[1] = 0xd8); (jpegSigTwo[2] = 0xff); (jpegSigTwo[3] = 0xe1);

    FILE *extractedFile;

    // Processes the command line input and checks for obvious errors; makes sure the program should run.
    processCommandLine(argc, argv);

    FILE *rawFile; // Begin opening the file, rawFile.
    if ((rawFile = fopen(argv[1], "rb")) == 0) { // Handles the case that the file could not be opened for a variety of reasons.
        printf("\n");
        fprintf(stderr, "File %s was not able to be opened! ", argv[1]);
        printf("Please re-run the program and try again.\n");
        exit(1); // Terminates with non-0 int.
    }

    // File is now opened for read-only binary reading from the current directory.

    printf("Searching %s for JPEGs ...", argv[1]);

    // Routine for looking through blocks of 512 for JPEG signatures here
    while ((numRead = fread(&rawFileBuffer, sizeof(char), BUFFSIZE, rawFile)) > 0) {

        char fileName[20];
        sprintf(fileName, "NLA_Image%d.jpg", numExtracted);

        fread(&rawFileFirstFourBytes, sizeof(char), SIGLENGTH, rawFile);

        if (compareFirstFourBytes(rawFileFirstFourBytes, jpegSigOne) || compareFirstFourBytes(rawFileFirstFourBytes, jpegSigTwo)) {
            fclose(extractedFile);
            extractedFile = fopen(fileName, "a");
            numExtracted++;
        }

            // Write the 512 bytes from rawFile buffer into extractedFile; TO BE WRITTEN.

    }

    // If no JPEGs are found:
    if (numExtracted == 0) {
        printf("\n");
        fprintf(stderr, "No JPEGs found in file! ");
        printf("Program exiting!");
        exit(1);
    }

    if (fclose(rawFile) < 0) {
        printf("\n");
        fprintf(stderr, "Unable to close %s! ", argv[1]);
        printf("Program exiting!");
        exit(1);
    }

    // Tells how many JPEGs were successfully extracted from the passed rawFile, and exits.
    printf("%d JPEGs successfully extracted. Program now successfully terminating.", numExtracted);

    return EXIT_SUCCESS;
}