/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * 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 <stdio.h>      /* defines BUFSIZ */
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

/*
 * This file implements the input routines used by the parser.
 */

#include "shell.h"
#include "redir.h"
#include "syntax.h"
#include "input.h"
#include "output.h"
#include "options.h"
#include "memalloc.h"
#include "error.h"
#include "alias.h"
#include "parser.h"
#ifndef NO_HISTORY
#include "myhistedit.h"
#endif
#include "trap.h"

#define EOF_NLEFT -99           /* value of parsenleft when EOF pushed back */

struct strpush {
        struct strpush *prev;   /* preceding string on stack */
        const char *prevstring;
        int prevnleft;
        int prevlleft;
        struct alias *ap;       /* if push was associated with an alias */
};

/*
 * The parsefile structure pointed to by the global variable parsefile
 * contains information about the current file being read.
 */

struct parsefile {
        struct parsefile *prev; /* preceding file on stack */
        int linno;              /* current line */
        int fd;                 /* file descriptor (or -1 if string) */
        int nleft;              /* number of chars left in this line */
        int lleft;              /* number of lines left in this buffer */
        const char *nextc;      /* next char in buffer */
        char *buf;              /* input buffer */
        size_t bufsize;         /* input buffer size */
        struct strpush *strpush; /* for pushing strings at this level */
        struct strpush basestrpush; /* so pushing one is fast */
};


int plinno = 1;                 /* input line number */
int parsenleft;                 /* copy of parsefile->nleft */
static int parselleft;          /* copy of parsefile->lleft */
const char *parsenextc;         /* copy of parsefile->nextc */
static char basebuf[BUFSIZ + 1];/* buffer for top level input file */
static struct parsefile basepf = {      /* top level input file */
        .nextc = basebuf,
        .buf = basebuf,
        .bufsize = sizeof(basebuf),
};
static struct parsefile *parsefile = &basepf;   /* current input file */
int whichprompt;                /* 1 == PS1, 2 == PS2 */

static void pushfile(void);
static int preadfd(void);
static void popstring(void);

void
resetinput(void)
{
        popallfiles();
        parselleft = parsenleft = 0;    /* clear input buffer */
}



/*
 * Read a character from the script, returning PEOF on end of file.
 * Nul characters in the input are silently discarded.
 */

int
pgetc(void)
{
        return pgetc_macro();
}


static int
preadfd(void)
{
        int nr;

retry:
#ifndef NO_HISTORY
        if (parsefile->fd == 0 && el) {
                const char *line;

                el_resize(el);
                line = el_gets(el, &nr);
                if (nr > 0 && parsefile->bufsize < (size_t)nr + 1) {
                        size_t bufsize;

                        INTOFF;
                        if (parsefile->buf != basebuf) {
                                ckfree(parsefile->buf);
                                parsefile->buf = NULL;
                                parsefile->bufsize = 0;
                        }
                        bufsize = (size_t)nr + BUFSIZ + 1;
                        bufsize -= bufsize % BUFSIZ;
                        parsefile->buf = ckmalloc(bufsize);
                        parsefile->bufsize = bufsize;
                        INTON;
                }
                if (nr > 0 && line != NULL)
                        memcpy(parsefile->buf, line, nr);
                else
                        nr = nr ? -1 : 0;
        } else
#endif
        nr = read(parsefile->fd, parsefile->buf, parsefile->bufsize - 1);

        if (nr < 0)
                switch (errno) {
                        int flags;

                case EINTR:
                        goto retry;
                case EWOULDBLOCK:
                        if (parsefile->fd != 0)
                                break;
                        if ((flags = fcntl(0, F_GETFL, 0)) < 0)
                                break;
                        if (!(flags & O_NONBLOCK))
                                break;
                        if (fcntl(0, F_SETFL, flags & ~O_NONBLOCK) < 0)
                                break;
                        out2fmt_flush("sh: turning off NDELAY mode\n");
                        goto retry;
                }
        else if (nr > 0)
                parsefile->buf[nr] = '\0';
        else
                nr = -1;

        parsenextc = parsefile->buf;
        return nr;
}

/*
 * Refill the input buffer and return the next input character:
 *
 * 1) If a string was pushed back on the input, pop it;
 * 2) If an EOF was pushed back (parsenleft == EOF_NLEFT) or we are reading
 *    from a string so we can't refill the buffer, return EOF.
 * 3) If there is more in this buffer, use it else call read to fill it.
 * 4) Process input up to the next newline, deleting nul characters.
 */

int
preadbuffer(void)
{
        const char *end;
        char *q, *r;
        char savec;

        while (parsefile->strpush) {
                /*
                 * Add a space to the end of an alias to ensure that the
                 * alias remains in use while parsing its last word.
                 * This avoids alias recursions.
                 */
                if (parsenleft == -1 && parsefile->strpush->ap != NULL)
                        return ' ';
                popstring();
                if (--parsenleft >= 0)
                        return (*parsenextc++);
        }
        if (parsenleft == EOF_NLEFT || parsefile->buf == NULL)
                return PEOF;

again:
        if (parselleft <= 0 && (parselleft = preadfd()) == -1) {
                parselleft = parsenleft = EOF_NLEFT;
                return (PEOF);
        }
        end = parsenextc + parselleft;
        q = strchrnul(parsenextc, '\n');
        if (*q == '\0' && q != end) {
                /* delete nul characters */
                for (r = q++; q != end; q++)
                        if (*q != '\0')
                                *r++ = *q;
                *r = '\0';
                parselleft = r - parsenextc;
                goto again;
        }
        if (*q == '\0') {
                parsenleft = parselleft;
                parselleft = 0;
        } else /* *q == '\n' */ {
                q++;
                parsenleft = q - parsenextc;
                parselleft -= parsenleft;
        }
        parsenleft--;

        savec = *q;
        *q = '\0';

#ifndef NO_HISTORY
        if (parsefile->fd == 0 && hist &&
            parsenextc[strspn(parsenextc, " \t\n")] != '\0') {
                HistEvent he;
                INTOFF;
                history(hist, &he, whichprompt == 1 ? H_ENTER : H_ADD,
                    parsenextc);
                INTON;
        }
#endif

        if (vflag) {
                out2str(parsenextc);
                flushout(out2);
        }

        *q = savec;

        return *parsenextc++;
}

/*
 * Returns if we are certain we are at EOF. Does not cause any more input
 * to be read from the outside world.
 */

int
preadateof(void)
{
        if (parsenleft > 0)
                return 0;
        if (parsefile->strpush)
                return 0;
        if (parsenleft == EOF_NLEFT || parsefile->buf == NULL)
                return 1;
        return 0;
}

/*
 * Undo the last call to pgetc.  Only one character may be pushed back.
 * PEOF may be pushed back.
 */

void
pungetc(void)
{
        parsenleft++;
        parsenextc--;
}

/*
 * Push a string back onto the input at this current parsefile level.
 * We handle aliases this way.
 */
void
pushstring(const char *s, int len, struct alias *ap)
{
        struct strpush *sp;

        INTOFF;
/*out2fmt_flush("*** calling pushstring: %s, %d\n", s, len);*/
        if (parsefile->strpush) {
                sp = ckmalloc(sizeof(struct strpush));
                sp->prev = parsefile->strpush;
                parsefile->strpush = sp;
        } else
                sp = parsefile->strpush = &(parsefile->basestrpush);
        sp->prevstring = parsenextc;
        sp->prevnleft = parsenleft;
        sp->prevlleft = parselleft;
        sp->ap = ap;
        if (ap)
                ap->flag |= ALIASINUSE;
        parsenextc = s;
        parsenleft = len;
        INTON;
}

static void
popstring(void)
{
        struct strpush *sp = parsefile->strpush;

        INTOFF;
        if (sp->ap) {
                if (parsenextc != sp->ap->val &&
                    (parsenextc[-1] == ' ' || parsenextc[-1] == '\t'))
                        forcealias();
                sp->ap->flag &= ~ALIASINUSE;
        }
        parsenextc = sp->prevstring;
        parsenleft = sp->prevnleft;
        parselleft = sp->prevlleft;
/*out2fmt_flush("*** calling popstring: restoring to '%s'\n", parsenextc);*/
        parsefile->strpush = sp->prev;
        if (sp != &(parsefile->basestrpush))
                ckfree(sp);
        INTON;
}

/*
 * Set the input to take input from a file.  If push is set, push the
 * old input onto the stack first.
 * About verify:
 *   -1: Obey verifyflag
 *    0: Do not verify
 *    1: Do verify
 */

void
setinputfile(const char *fname, int push, int verify)
{
        int e;
        int fd;
        int fd2;
        int oflags = O_RDONLY | O_CLOEXEC;

        if (verify == 1 || (verify == -1 && verifyflag))
                oflags |= O_VERIFY;

        INTOFF;
        if ((fd = open(fname, oflags)) < 0) {
                e = errno;
                errorwithstatus(e == ENOENT || e == ENOTDIR ? 127 : 126,
                    "cannot open %s: %s", fname, strerror(e));
        }
        if (fd < 10) {
                fd2 = fcntl(fd, F_DUPFD_CLOEXEC, 10);
                close(fd);
                if (fd2 < 0)
                        error("Out of file descriptors");
                fd = fd2;
        }
        setinputfd(fd, push);
        INTON;
}


/*
 * Like setinputfile, but takes an open file descriptor (which should have
 * its FD_CLOEXEC flag already set).  Call this with interrupts off.
 */

void
setinputfd(int fd, int push)
{
        if (push)
                pushfile();
        if (parsefile->fd > 0)
                close(parsefile->fd);
        parsefile->fd = fd;
        if (parsefile->buf == NULL) {
                parsefile->buf = ckmalloc(BUFSIZ + 1);
                parsefile->bufsize = BUFSIZ + 1;
        }
        parselleft = parsenleft = 0;
        plinno = 1;
}


/*
 * Like setinputfile, but takes input from a string.
 */

void
setinputstring(const char *string)
{
        INTOFF;
        pushfile();
        parsenextc = string;
        parselleft = parsenleft = strlen(string);
        plinno = 1;
        INTON;
}



/*
 * To handle the "." command, a stack of input files is used.  Pushfile
 * adds a new entry to the stack and popfile restores the previous level.
 */

static void
pushfile(void)
{
        struct parsefile *pf;

        pf = (struct parsefile *)ckmalloc(sizeof(struct parsefile));
        *pf = (struct parsefile){ .prev = parsefile, .fd = -1 };
        parsefile->nleft = parsenleft;
        parsefile->lleft = parselleft;
        parsefile->nextc = parsenextc;
        parsefile->linno = plinno;
        parsefile = pf;
}


void
popfile(void)
{
        struct parsefile *pf = parsefile;

        INTOFF;
        if (pf->fd >= 0)
                close(pf->fd);
        if (pf->buf)
                ckfree(pf->buf);
        while (pf->strpush)
                popstring();
        parsefile = pf->prev;
        ckfree(pf);
        parsenleft = parsefile->nleft;
        parselleft = parsefile->lleft;
        parsenextc = parsefile->nextc;
        plinno = parsefile->linno;
        INTON;
}


/*
 * Return current file (to go back to it later using popfilesupto()).
 */

struct parsefile *
getcurrentfile(void)
{
        return parsefile;
}


/*
 * Pop files until the given file is on top again. Useful for regular
 * builtins that read shell commands from files or strings.
 * If the given file is not an active file, an error is raised.
 */

void
popfilesupto(struct parsefile *file)
{
        while (parsefile != file && parsefile != &basepf)
                popfile();
        if (parsefile != file)
                error("popfilesupto() misused");
}

/*
 * Return to top level.
 */

void
popallfiles(void)
{
        while (parsefile != &basepf)
                popfile();
}



/*
 * Close the file(s) that the shell is reading commands from.  Called
 * after a fork is done.
 */

void
closescript(void)
{
        popallfiles();
        if (parsefile->fd > 0) {
                close(parsefile->fd);
                parsefile->fd = 0;
        }
}