/*==================================================================
 *
 *               University College Dublin
 *          COMP20020 - Unix Programming
 *
 * File Name    :   assign1-18442024.c
 *
 * Description  :   program to carry out user controlled head and tail operations on a file read from stdin
 *                  checklist:
 *                      getopt working coorectly
 *                      default 10 lines working correctly
 *                      -n K lines function working correctly
 *                      -h program description working correctly
 *                      -V print version version info working correctly
 *                      -e/-o options working correctly
 *                      read from stdin if no recognisable file is supplied
 *                      all functions work form both supplied files and std input files
 *
 *
 * Author       :   Matthew Murnaghan
 *
 * Date         :   16-02-20
 *
 *==================================================================*/

#include <stdlib.h>
#include <stdio.h>
#include <getopt.h>     // include relevant libraries
#include <string.h>
#include <stdbool.h>

#define READONLY "r"    // defined for use in file opening
#define HEADERSIZE 10
#define TAILSIZE 10
#define MAXLINE_LENGTH 180  // defines max line length, can be changed to suit file, use for printing a seperating line between stdin input and stdin output file
#define DEBUG 0   // defined to enable optional debug mode for analysis                                                                           // see line 130
#define MAX_ARGUEMENTS 5

int main(int argc, char **argv)
{
    int K, lines = 0, ctr = 1, evenOdd = 2, option, i;       // declares int values for later use
    char *line;                                                                                  // declares pointer to line foe use in getline fucntion
    char head[] = "head", tail[] = "tail", V[] = "V", h[] = "h";                                 // declares char arrays for later use
    char usage[] = "Error - Input format must be: { head | tail } [OPTION ] . . . [ FILE ]\n\n"; // declares generic usage error message
    char optlist[] = "List of options for this program -->-n (int) K--returns int value K lines of read file\n-V-- returns version info\n-h-- returns help message\n-o-- returns odd lines of file\n-e-- returns even lines of file";
    bool headMode = false, tailMode = false, fsupplied = true, optsupplied = false;              // declares booleans for condition checking
    size_t len = 0;                                                                              // delcares size_t for use in get line for correct memory allocation
    FILE *fpin, *tmpFile;                                                                        //declares needed file pointers
    if (DEBUG)
        printf("argc = %d\n\n", argc);
    if (DEBUG)
        for (i = 0; i < argc; i++)
        {
            printf("argv %d = %s \n", i, argv[i]);  // prints all arguments to the function
        }
    if (argc > MAX_ARGUEMENTS)
    {
        printf("Error - arguments for this program must not exceed 5\n");   // Prints specific error message if user exceeds max number of arguements
        exit(2);
    }
    for (i = 1; i < argc; i++)  // checks all arguments to see of -h or -V is present
    {
        if (strcmp(argv[i], "-h") ==0 || strcmp(argv[i], "-H") == 0)
        {
            if (DEBUG)
            {
                printf("%d\n", strcmp(argv[i], "-h"));
                printf("-h present - optsupplied = true\n");
            }
            optsupplied = true; // sets optsupplied to true for comparison check. if optsupplied == true
        }
            if (strcmp(argv[i], "-V") == 0 || strcmp(argv[i], "-v") == 0)
        {
            if (DEBUG)
                printf("-V present - optsupplied = true\n");
            optsupplied = true;
        }
    }
    if (argc<2)
    {
        printf("%sMust provide at least 2 arguements\n", usage);
        exit(2);
    }
    if (DEBUG)
    {
        printf("optsupplied false\n");
    }
    if (optsupplied == false)
    {
        if ((strncmp(head, argv[1], 4)) == 0)
        {
            if (DEBUG)
                printf("headmode\n");
            headMode = true;
        }
        else if ((strncmp(tail, argv[1], 4)) == 0)
        {
            if (DEBUG)
                printf("tailemode\n");
            tailMode = true; // printf("head/tail check\n");
        }
    }
    if (optsupplied == false) // checks to make sure h option hasnt been triggered before attempting to open a file.
    {
        if ((fpin = fopen(argv[argc - 1], READONLY)) == NULL)
        {
            fsupplied = false;
            printf("No File provided or file not recognised\n\nOpening temp file from stdin:\nTo end file input: user input --> \"Ctrl + D\"\n");
            fpin = stdin;
            tmpFile = tmpfile();
            if (tmpFile == NULL)
            {
                printf("Temp file failed to open \n");
                exit(EXIT_FAILURE);
            }
            while ((getline(&line, &len, fpin)) != EOF)
            {
                fputs(line, tmpFile);
                lines++;
            }
            if (DEBUG)
                printf("lines %d\n", lines);
            fpin = tmpFile;
        }
        if (DEBUG)
        {
            printf("%d\n", fsupplied);
            printf("file opened\n");
        }
        if (DEBUG)
            printf("lines %d\n", lines);
        if (fsupplied == false)
        {
            for (i = 0; i < MAXLINE_LENGTH; i++)
                fputs("-", stdout);

            fputs("\n", stdout);
            fseek(fpin, 0, SEEK_SET);
        }
    }
    if (DEBUG)
        printf("start of while loop\n");

    while ((option = getopt(argc, argv, "hvn:eo")) != -1 || argc < 4)
    {
        switch (option)
        {
        case 'o':
            if (argc > 4)
            {
                printf("Error - even odd option requires no integer input\n");
                exit(2);
            }
            while ((getline(&line, &len, fpin)) != EOF)
            {
                if (evenOdd % 2 == 0) /* code */
                {
                    fputs(line, stdout);
                }
                evenOdd++;
            }
            exit(EXIT_SUCCESS);
            {
                fputs(usage, stdout);
                exit(2);
            {
                fputs(usage, stdout);
                exit(2);
            }
            }

        case 'e':
            if (argc > 4)
            {
                printf("Error - even odd option requires no integer input\n");
                exit(2);
            }
            evenOdd = 1;
            while ((getline(&line, &len, fpin)) != EOF)
            {
                if (evenOdd % 2 == 0)
                {
                    fputs(line, stdout);
                }
                evenOdd++;
            }
            exit(EXIT_SUCCESS);

        case 'V':
            if (optsupplied == true && argc>2)
            {
                printf("Error -V option requires only 2 inputs\n");
                exit(2);
            }
            printf("Version info:\n\tProgram Author: Matthew Murnaghan\n\tStudent email: \tmatthew.murnaghan@ucdconnect.ie\n\tstudent number: 18442024\n");
            exit(EXIT_SUCCESS);

        case 'n':
            lines = 0;
            K = atoi(optarg);
            if (DEBUG)
                printf("%d\n", K);
            if (headMode == true)
            {
                for (ctr = 0; ctr < K; ctr++)
                {
                    (getline(&line, &len, fpin));
                    fputs(line, stdout);
                }
            }
            else if (tailMode == true)
            {
                if (DEBUG)
                    printf("tailmode - before while\n");
                while ((getline(&line, &len, fpin)) != EOF)
                {
                    lines++;
                }
                if (DEBUG)
                    printf("after while\nlines = %d\n", lines);
                fseek(fpin, 0, SEEK_SET);
                while ((getline(&line, &len, fpin)) != EOF)
                {
                    if (ctr > lines - K)
                        fputs(line, stdout);

                    ctr++;
                }
                fputs("\n", stdout);
            }
            exit(EXIT_SUCCESS);

        case 'h':
            if (optsupplied == true && argc>2)
            {
                printf("Error -h option requires only 2 inputs\n");

                exit(2);
            }
            fputs("\nThis is a program to print a user specified amount of lines from the head or tail of a file\n", stdout);
            fputs("Input format must be: { head | tail } [OPTION ] . . . [ FILE ]\n\n", stdout);
            printf("%s\n", optlist);
            exit(EXIT_SUCCESS);

        default:
            if (DEBUG)
                printf("default\n");
            if (headMode == true)
            {
                if (DEBUG)
                    printf("forloop\n");
                if (lines < HEADERSIZE && fsupplied == false) //this part is used for when no file is supplied and the default case should trigger
                {
                    if (DEBUG)
                        printf("ctr = %d\n", ctr);
                    for (ctr = 0; ctr < lines; ctr++)
                    {
                        (getline(&line, &len, fpin));
                        fputs(line, stdout);
                    }
                }
                else
                {
                    lines = 0;
                    for (ctr = 0; ctr < HEADERSIZE; ctr++) // this part is for when a file is supplied
                    {
                        (getline(&line, &len, fpin));
                        fputs(line, stdout);
                    }
                    if (DEBUG)
                        printf("past forloop\n");
                }
            }
            else if (tailMode == true)
            {
                if (DEBUG)
                    printf("tail mode - before while\n");
                while ((getline(&line, &len, fpin)) != EOF)
                {
                    lines++;
                }
                if (DEBUG)
                    printf("after while\nlines =%d\n", lines);
                fseek(fpin, 0, SEEK_SET);
                while ((getline(&line, &len, fpin)) != EOF)
                {
                    if (ctr > lines - TAILSIZE)
                        fputs(line, stdout);

                    ctr++;
                }
                fputs("\n", stdout);
            }
            else
            {
                printf("%s", usage);
                exit(2);
            }
            exit(EXIT_SUCCESS);
        }
    }
    if (headMode)
    {
        fclose(fpin);
        free(line);
        free(tmpFile);
    }
    exit(EXIT_SUCCESS);
}