/*******************************************************
* Section : 15
* Machine No. : N
* Roll No. : 19CS100XY
* Name : Aritra Hazra
* Assignment No : 9
* Description : File Handling and Comman-line Arguments
*******************************************************/

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>    // for srand(), rand()
#include <sys/types.h> // for getpid()
#include <unistd.h>    // for getpid()

#define defaultOutputFile "output.txt"
#define defaultInterFile "inter.txt"

void printUsage()
{
	fprintf(stderr,"USAGE:: ./a.out -input <Input_File_Name> [-output <Output_File_Name>] [-flag <Flag_Option>]\n\t([ ] indicates optional arguments)\n");
}

int main(int argc, char **argv)
{
    char *inputFile, *outputFile = defaultOutputFile, *flagOption = NULL;
    FILE *inputFP, *outputFP, *interFP;
    int i, shift, reportAlpha = 0, reportNum = 0, reportSymb = 0;
    char c;
    
    srand( getpid() );

    // Opening the Read-Write Files From Command-Line Input
    if(argc > 7) {
        fprintf(stderr,"Error: Too Many Arguments!!\n");
        printUsage();
        exit(0);
    }
    if(argc < 3) {
        fprintf(stderr,"Error: Too Few Arguments!!\n");
        printUsage();
        exit(0);
    }
    for(i = 1; i < argc; i = i + 2) {
        if(!strcmp(argv[i],"-input")) {
            if(i + 1 == argc || !strcmp(argv[i + 1],"-output") || !strcmp(argv[i + 1],"-flag")) {
                fprintf(stderr,"Error: Input_File_Name Not Specified!!\n");
                printUsage();
                exit(0);
            }
            else {
                inputFile = argv[i + 1];
            }
        }
        else {
            if(!strcmp(argv[i],"-output")) {
                if(i + 1 == argc || !strcmp(argv[i + 1],"-input") || !strcmp(argv[i + 1],"-flag")) {
                    fprintf(stderr,"Error: Output_File_Name Not Specified!!\n");
                    printUsage();
                    exit(0);
                }
                else {
                    outputFile = argv[i + 1];
                }
            }
            else {
                if(!strcmp(argv[i],"-flag"))
                    if(i + 1 == argc || !strcmp(argv[i + 1],"-input") || !strcmp(argv[i + 1],"-output")) {
                        fprintf(stderr,"Error: Flag_Options Not Specified!!\n");
                        printUsage();
                        exit(0);
                    }
                    else {
                        flagOption = argv[i + 1];
                    }
                else {
                    fprintf(stderr,"Error: Wrong Arguments!!\n");
                    printUsage();
                    exit(0);
                }
            }
        }
    }
    
    // Check whether input file specified
    if(inputFile == NULL) {
        fprintf(stderr,"Error: Input_File_Name Not Specified!!\n");
        printUsage();
        exit(0);
    }
    else {
        inputFP = fopen(inputFile, "r");
        if(inputFP == NULL) { // Checking input file error
            fprintf(stderr,"Error: Cannot Open Input File!!\n");
            exit(0);
        }
        interFP = fopen(defaultInterFile, "w");
        if(interFP == NULL) { // Checking intermediate file error
            fprintf(stderr,"Error: Cannot Open Intermediate File!!\n");
            exit(0);
        }
        
        //making the intermediate file with caeser cipher text (alphabets shifted within [1-10])
        shift = (char)(rand() % 10 + 1) ; // Generating shift within 1-10 range
        printf("shift = %d\n", shift);
        while((c = fgetc(inputFP)) != EOF) {
            if(isalpha(c)) {
                if(isupper(c))
                    fputc((c-'A'+shift)%26+'A', interFP);
                else
                    fputc((c-'a'+shift)%26+'a', interFP);
            }
            else
                fputc(c, interFP);
        }
        fclose(interFP);
        
        interFP = fopen(defaultInterFile, "r");
        if(interFP == NULL) { // checking intermediate file error
            fprintf(stderr,"Error: Cannot Open Intermediate File!!\n");
            exit(0);
        }
        outputFP = fopen(outputFile, "w");
        if(outputFP == NULL) { // Checking output file error
            fprintf(stderr,"Error: Cannot Open Output File!!\n");
            exit(0);
        }
        if(flagOption == NULL) { // Checking flag option error
            fprintf(stderr,"Error: Cannot Find Flag Option!!\n");
            exit(0);
        }
        for(i=0; flagOption[i] != '\0'; i++) {
            if(flagOption[i] == 'a') reportAlpha = 1; // need to report all alphabatic characters
            if(flagOption[i] == 'n') reportNum = 1; // need to report all numeric characters
            if(flagOption[i] == 's') reportSymb = 1; // need to report all symbols
        }
        
        // Reporting all alphabatic characters
        fputs("Alphabetic Characters:\n", outputFP);
        while((c = fgetc(interFP)) != EOF) {
            if(reportAlpha) {
                if(isalpha(c)) {
                    fputc(c, outputFP);
                    fputc(' ', outputFP);
                }
            }
        }
        fputc('\n', outputFP);
        // Reporting all numeric characters
        fseek(interFP, 0, SEEK_SET);
        fputs("Numeric Characters:\n", outputFP);
        while((c = fgetc(interFP)) != EOF) {
            if(reportNum) {
                if(isdigit(c)) {
                    fputc(c, outputFP);
                    fputc(' ', outputFP);
                }
            }
        }
        fputc('\n', outputFP);
        // Reporting all symbols (ignoring space)
        fseek(interFP, 0, SEEK_SET);
        fputs("Symbolic Characters:\n", outputFP);
        while((c = fgetc(interFP)) != EOF) {
            if(reportSymb) {
                if(!isalnum(c) && c != ' ') {
                    if(c == '\n') fputs("\\n ", outputFP);
                    else if(c == '\t') fputs("\\t ", outputFP);
                    else {
                        fputc(c, outputFP);
                        fputc(' ', outputFP);
                    }
                }
            }
        }
        fputs("\n\n", outputFP);
        
        fclose(interFP);
        fclose(inputFP);
        fclose(outputFP);
    }

    return 0;
}