/*
 * Copyright (c) 2020 Roger Seguin <rgrsgn@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

static char     rcsid[] =
    "$Id: expandtabs.C,v 1.1 2020/08/29 10:36:45 RogerSeguin Exp $";

/*
Description:
	Replace tabs with spaces
	Usage:
		expandtabs <inputfile >outputfile
		expandtabs inputfile outputfile
		expandtabs infile
*/

#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h> 
#include <sys/stat.h>
#include <iostream>
#include <exception>
#include <string>

namespace {
    int m_tabSz = 8;	// How many spaces per tab
}

using namespace std;

int usage(const char *prg)
{
    cout << rcsid + 5 << endl;
    cout << prg << " - Replace tabs with spaces" << endl;
    cout << "Usage:" << endl;
    cout << '\t' << prg << " [-t n] [<inputfile >outputfile]" << endl;
    cout << '\t' << prg << " [-t n] infile [outputfile]" << endl;
    cout << '\t' << prg << " -h" << endl;
    cout << "Options:" << endl;
    cout << "\t-t n\tset tab size to n spaces [2..8] (default=" << m_tabSz << ")"
         << endl;
    cout << "\t-h\tdisplay this message and exit" << endl;
    cout << "Description:" << endl;
    cout << "\tIf no parameters are given, input is stdin and output is stdout"
         << endl;
    cout << "\tIf only one file name is indicated, the repacement is in-place"
         << endl;
    cout  << "\t\t(original file backed up with suffix .BAK)" << endl;
    cout << "\tIf 2 parameters are given, read input file and write output file"
         << endl;
    return (0);
}	// usage()

class ReadWriteError: public exception {
        virtual const char* what() const throw()
        {
            return "ReadWriteError";
        }
};	// class ReadWriteError

int readchar(int fd)
{
    char c;
    int n = read(fd, &c, sizeof (char));
    if (n == 1)
        return (c);
    if (n == 0)	// Nothing to read
        return (EOF);
    /* Should never reach here */
    if (n == -1)
        perror("read()");
    throw (ReadWriteError());
    return (-1);
}	// readchar()

int processFileNumbers (int fdin, int fdout)
{
    /* Read fdin, replace tabs with spaces, output to fdout */
    const char SPACE = ' ',
               NEWLINE = '\n',
               TAB = '\t';
    try {
        bool loop = true;
        while (loop) {
            int c;
            int pos = 0;
            while ((c = readchar(fdin)) && (c != EOF) && (c != NEWLINE)) {
                if (c == TAB) {
                    do {
                        int n = write (fdout, &SPACE, sizeof (char));
                        if (n != 1) {
                            perror("write()");
                            throw (ReadWriteError());
                        }
                    } while ((++pos) % m_tabSz);
                }
                else {
                    int n = write (fdout, &c, sizeof (char));
                    if (n != 1) {
                        perror("write()");
                        throw (ReadWriteError());
                    }
                    ++pos;
                }
            }
            if (c == NEWLINE) {
                int n = write (fdout, &NEWLINE, sizeof (char));
                if (n != 1) {
                    perror("write()");
                    throw (ReadWriteError());
                }
            }
            else
                /* EOF */
                loop = false;
        }
    }
    catch (...) {
        cerr << "Exception caught" << endl;
        return (-1);
    }
    return (0);
}	// processFileNumbers()

int processFilenames (const char *infile, const char*outfile)
{
    int fdin,
        fdout;
    struct stat stat;
    int status;
    fdin = open (infile, O_RDONLY | O_LARGEFILE);
    if (fdin == -1) {
        perror (infile);
        return (-1);
    }
    status = fstat (fdin, &stat);
    if (status == -1) {
        perror (infile);
        return (-1);
    }
    fdout = open (outfile, O_CREAT | O_TRUNC | O_WRONLY | O_LARGEFILE,
                  stat.st_mode);
    if (fdout == -1) {
        perror (outfile);
        close (fdin);
        return (-1);
    }
    /* Replace tabs with space */
    status = processFileNumbers (fdin, fdout);
    close (fdin);
    close (fdout);
    return (0);
}	// processFilenames()

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

    /* Check commandline parameters */
    bool         fUsage = 0;
    for (char c; (c = getopt (argc, argv, "ht:")) != EOF;)
        switch (c) {
            case 'h':          // Help
                fUsage = 1;
                break;
            case 't':          // Key value
                m_tabSz = atoi (optarg);
                fUsage |= ((m_tabSz < 2) || (m_tabSz > 8));
                break;
            case '?':
            default:
                fUsage = 1;
        }
    int nfiles = argc - optind;
    fUsage |= (nfiles > 2);
    if (fUsage) {
        usage(basename (argv[0]));	// GNU version
        exit (1);
    }

    /* Replace tabs with spaces */
    string filename1,
           filename2;
    int status;
    switch (nfiles) {
        case 0:
            status = processFileNumbers (0, 1);	// (stdin, stdout)
            break;
        case 1:
            filename2 = string(argv[optind]);
            filename1 = filename2 + ".BAK";
            status = rename (filename2.c_str(), filename1.c_str());
            if (status == -1) {
                perror (filename2.c_str());
                exit (~0);
            }
            status = processFilenames (filename1.c_str(), filename2.c_str());
            break;
        case 2:
            filename1 = string(argv[optind]);
            filename2 = string(argv[optind + 1]);
            status = processFilenames (filename1.c_str(), filename2.c_str());
            break;
    }
    return (status);
}	// main()

/*
$Log: expandtabs.C,v $
Revision 1.1  2020/08/29 10:36:45  RogerSeguin
Initial revision

*/