/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1987, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 */

#include <sys/param.h>
#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <libutil.h>
#include <limits.h>
#include <locale.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <regex.h>
#include <sysexits.h>

#define DEFLINE 1000                    /* Default num lines per file. */

static off_t     bytecnt;               /* Byte count to split on. */
static long      chunks;                /* Chunks count to split into. */
static bool      clobber = true;        /* Whether to overwrite existing output files. */
static long      numlines;              /* Line count to split on. */
static int       file_open;             /* If a file open. */
static int       ifd = -1, ofd = -1;    /* Input/output file descriptors. */
static char      fname[MAXPATHLEN];     /* File name prefix. */
static regex_t   rgx;
static int       pflag;
static bool      dflag;
static long      sufflen = 2;           /* File name suffix length. */
static bool      autosfx = true;        /* Whether to auto-extend the suffix length. */

static void newfile(void);
static void split1(void);
static void split2(void);
static void split3(void);
static void usage(void) __dead2;

int
main(int argc, char **argv)
{
        char errbuf[64];
        const char *p, *errstr;
        int ch, error;

        setlocale(LC_ALL, "");

        dflag = false;
        while ((ch = getopt(argc, argv, "0::1::2::3::4::5::6::7::8::9::a:b:cdl:n:p:")) != -1)
                switch (ch) {
                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        /*
                         * Undocumented kludge: split was originally designed
                         * to take a number after a dash.
                         */
                        if (numlines != 0)
                                usage();
                        numlines = ch - '0';
                        p = optarg ? optarg : "";
                        while (numlines >= 0 && *p >= '0' && *p <= '9')
                                numlines = numlines * 10 + *p++ - '0';
                        if (numlines <= 0 || *p != '\0')
                                errx(EX_USAGE, "%c%s: line count is invalid",
                                    ch, optarg ? optarg : "");
                        break;
                case 'a':               /* Suffix length */
                        sufflen = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL) {
                                errx(EX_USAGE, "%s: suffix length is %s",
                                    optarg, errstr);
                        }
                        if (sufflen == 0) {
                                sufflen = 2;
                                autosfx = true;
                        } else {
                                autosfx = false;
                        }
                        break;
                case 'b':               /* Byte count. */
                        if (expand_number(optarg, &bytecnt) != 0) {
                                errx(EX_USAGE, "%s: byte count is invalid",
                                    optarg);
                        }
                        break;
                case 'c':               /* Continue, don't overwrite output files. */
                        clobber = false;
                        break;
                case 'd':               /* Decimal suffix */
                        dflag = true;
                        break;
                case 'l':               /* Line count. */
                        if (numlines != 0)
                                usage();
                        numlines = strtonum(optarg, 1, LONG_MAX, &errstr);
                        if (errstr != NULL) {
                                errx(EX_USAGE, "%s: line count is %s",
                                    optarg, errstr);
                        }
                        break;
                case 'n':               /* Chunks. */
                        chunks = strtonum(optarg, 1, LONG_MAX, &errstr);
                        if (errstr != NULL) {
                                errx(EX_USAGE, "%s: number of chunks is %s",
                                    optarg, errstr);
                        }
                        break;

                case 'p':               /* pattern matching. */
                        error = regcomp(&rgx, optarg, REG_EXTENDED|REG_NOSUB);
                        if (error != 0) {
                                regerror(error, &rgx, errbuf, sizeof(errbuf));
                                errx(EX_USAGE, "%s: regex is invalid: %s",
                                    optarg, errbuf);
                        }
                        pflag = 1;
                        break;
                default:
                        usage();
                }
        argv += optind;
        argc -= optind;

        if (argc > 0) {                 /* Input file. */
                if (strcmp(*argv, "-") == 0)
                        ifd = STDIN_FILENO;
                else if ((ifd = open(*argv, O_RDONLY, 0)) < 0)
                        err(EX_NOINPUT, "%s", *argv);
                ++argv;
                --argc;
        }
        if (argc > 0) {                 /* File name prefix. */
                if (strlcpy(fname, *argv, sizeof(fname)) >= sizeof(fname)) {
                        errx(EX_USAGE, "%s: file name prefix is too long",
                            *argv);
                }
                ++argv;
                --argc;
        }
        if (argc > 0)
                usage();

        if (strlen(fname) + (unsigned long)sufflen >= sizeof(fname))
                errx(EX_USAGE, "suffix is too long");
        if (pflag && (numlines != 0 || bytecnt != 0 || chunks != 0))
                usage();

        if (numlines == 0)
                numlines = DEFLINE;
        else if (bytecnt != 0 || chunks != 0)
                usage();

        if (bytecnt != 0 && chunks != 0)
                usage();

        if (ifd == -1)                          /* Stdin by default. */
                ifd = 0;

        if (bytecnt != 0) {
                split1();
                exit (0);
        } else if (chunks != 0) {
                split3();
                exit (0);
        }
        split2();
        if (pflag)
                regfree(&rgx);
        exit(0);
}

/*
 * split1 --
 *      Split the input by bytes.
 */
static void
split1(void)
{
        static char bfr[MAXBSIZE];
        off_t bcnt;
        char *C;
        ssize_t dist, len;
        int nfiles;

        nfiles = 0;

        for (bcnt = 0;;)
                switch ((len = read(ifd, bfr, sizeof(bfr)))) {
                case 0:
                        exit(0);
                case -1:
                        err(EX_IOERR, "read");
                        /* NOTREACHED */
                default:
                        if (!file_open) {
                                if (chunks == 0 || nfiles < chunks) {
                                        newfile();
                                        nfiles++;
                                }
                        }
                        if (bcnt + len >= bytecnt) {
                                dist = bytecnt - bcnt;
                                if (write(ofd, bfr, dist) != dist)
                                        err(EX_IOERR, "write");
                                len -= dist;
                                for (C = bfr + dist; len >= bytecnt;
                                     len -= bytecnt, C += bytecnt) {
                                        if (chunks == 0 || nfiles < chunks) {
                                                newfile();
                                                nfiles++;
                                        }
                                        if (write(ofd, C, bytecnt) != bytecnt)
                                                err(EX_IOERR, "write");
                                }
                                if (len != 0) {
                                        if (chunks == 0 || nfiles < chunks) {
                                                newfile();
                                                nfiles++;
                                        }
                                        if (write(ofd, C, len) != len)
                                                err(EX_IOERR, "write");
                                } else {
                                        file_open = 0;
                                }
                                bcnt = len;
                        } else {
                                bcnt += len;
                                if (write(ofd, bfr, len) != len)
                                        err(EX_IOERR, "write");
                        }
                }
}

/*
 * split2 --
 *      Split the input by lines.
 */
static void
split2(void)
{
        char *buf;
        size_t bufsize;
        ssize_t len;
        long lcnt = 0;
        FILE *infp;

        buf = NULL;
        bufsize = 0;

        /* Stick a stream on top of input file descriptor */
        if ((infp = fdopen(ifd, "r")) == NULL)
                err(EX_NOINPUT, "fdopen");

        /* Process input one line at a time */
        while ((errno = 0, len = getline(&buf, &bufsize, infp)) > 0) {
                /* Check if we need to start a new file */
                if (pflag) {
                        regmatch_t pmatch;

                        pmatch.rm_so = 0;
                        pmatch.rm_eo = len - 1;
                        if (regexec(&rgx, buf, 0, &pmatch, REG_STARTEND) == 0)
                                newfile();
                } else if (lcnt++ == numlines) {
                        newfile();
                        lcnt = 1;
                }

                /* Open output file if needed */
                if (!file_open)
                        newfile();

                /* Write out line */
                if (write(ofd, buf, len) != len)
                        err(EX_IOERR, "write");
        }

        /* EOF or error? */
        if ((len == -1 && errno != 0) || ferror(infp))
                err(EX_IOERR, "read");
        else
                exit(0);
}

/*
 * split3 --
 *      Split the input into specified number of chunks
 */
static void
split3(void)
{
        struct stat sb;

        if (fstat(ifd, &sb) == -1) {
                err(1, "stat");
                /* NOTREACHED */
        }

        if (chunks > sb.st_size) {
                errx(1, "can't split into more than %d files",
                    (int)sb.st_size);
                /* NOTREACHED */
        }

        bytecnt = sb.st_size / chunks;
        split1();
}


/*
 * newfile --
 *      Open a new output file.
 */
static void
newfile(void)
{
        long i, maxfiles, tfnum;
        static long fnum;
        static char *fpnt;
        char beg, end;
        int pattlen;
        int flags = O_WRONLY | O_CREAT | O_TRUNC;

        if (!clobber)
                flags |= O_EXCL;

        if (ofd == -1) {
                if (fname[0] == '\0') {
                        fname[0] = 'x';
                        fpnt = fname + 1;
                } else {
                        fpnt = fname + strlen(fname);
                }
        } else if (close(ofd) != 0)
                err(1, "%s", fname);

        again:
        if (dflag) {
                beg = '0';
                end = '9';
        }
        else {
                beg = 'a';
                end = 'z';
        }
        pattlen = end - beg + 1;

        /*
         * If '-a' is not specified, then we automatically expand the
         * suffix length to accomodate splitting all input.  We do this
         * by moving the suffix pointer (fpnt) forward and incrementing
         * sufflen by one, thereby yielding an additional two characters
         * and allowing all output files to sort such that 'cat *' yields
         * the input in order.  I.e., the order is '... xyy xyz xzaaa
         * xzaab ... xzyzy, xzyzz, xzzaaaa, xzzaaab' and so on.
         */
        if (!dflag && autosfx && (fpnt[0] == 'y') &&
                        strspn(fpnt+1, "z") == strlen(fpnt+1)) {
                /* Ensure the generated filenames will fit into the buffer. */
                if (strlen(fname) + 2 >= sizeof(fname))
                        errx(EX_USAGE, "combined filenames would be too long");

                fpnt = fname + strlen(fname) - sufflen;
                fpnt[sufflen + 2] = '\0';
                fpnt[0] = end;
                fpnt[1] = beg;

                /*  Basename | Suffix
                 *  before:
                 *  x        | yz
                 *  after:
                 *  xz       | a.. */
                fpnt++;
                sufflen++;

                /* Reset so we start back at all 'a's in our extended suffix. */
                fnum = 0;
        }

        /* maxfiles = pattlen^sufflen, but don't use libm. */
        for (maxfiles = 1, i = 0; i < sufflen; i++)
                if (LONG_MAX / pattlen < maxfiles)
                        errx(EX_USAGE, "suffix is too long (max %ld)", i);
                else
                        maxfiles *= pattlen;

        if (fnum == maxfiles)
                errx(EX_DATAERR, "too many files");

        /* Generate suffix of sufflen letters */
        tfnum = fnum;
        i = sufflen - 1;
        do {
                fpnt[i] = tfnum % pattlen + beg;
                tfnum /= pattlen;
        } while (i-- > 0);
        fpnt[sufflen] = '\0';

        ++fnum;
        if ((ofd = open(fname, flags, DEFFILEMODE)) < 0) {
                if (!clobber && errno == EEXIST)
                        goto again;
                err(EX_IOERR, "%s", fname);
        }
        file_open = 1;
}

static void
usage(void)
{
        (void)fprintf(stderr,
"usage: split [-cd] [-l line_count] [-a suffix_length] [file [prefix]]\n"
"       split [-cd] -b byte_count[K|k|M|m|G|g] [-a suffix_length] [file [prefix]]\n"
"       split [-cd] -n chunk_count [-a suffix_length] [file [prefix]]\n"
"       split [-cd] -p pattern [-a suffix_length] [file [prefix]]\n");
        exit(EX_USAGE);
}