/*
**  L2 - OSSP Logging Library
**  Copyright (c) 2001 The OSSP Project (http://www.ossp.org/)
**  Copyright (c) 2001 Cable & Wireless Deutschland (http://www.cw.com/de/)
**
**  This file is part of OSSP L2, a flexible logging library which
**  can be found at http://www.ossp.org/pkg/l2/.
**
**  Permission to use, copy, modify, and distribute this software for
**  any purpose with or without fee is hereby granted, provided that
**  the above copyright notice and this permission notice appear in all
**  copies.
**
**  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 AUTHORS AND COPYRIGHT HOLDERS AND THEIR
**  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.
**
**  l2_ch_pipe.c: pipe channel implementation
*/

#include "l2.h"
#include "l2_p.h"              /* for TRACE() */

#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>

#define L2_PIPE_MODEDIRECT   1 /* direct command execution */
#define L2_PIPE_MODESHELL    2 /* shell  command execution */
#define L2_PIPE_MAXARGS    256 /* shell  command execution */

static l2_result_t hook_close(l2_context_t *, l2_channel_t *); /* prototypes */


/* declare private channel configuration */
typedef struct {
    pid_t            Pid;        /* process id of child command          */
    int              iWritefail; /* counter to failed write() operations */
    int              piFd[2];    /* pipe file descriptor                 */
    int              iMode;      /* execution mode direct or shell       */
    char            *szCmdpath;  /* path to command and arguments        */
    struct sigaction sigchld;    /* initial state of chld signal handler */
    struct sigaction sigpipe;    /* initial state of pipe signal handler */
} l2_ch_pipe_t;

static void catchsignal(int sig, ...)
{
    pid_t Pid;         /* for wait() */
    int   iStatus = 0; /* for wait() */

    if (sig == SIGCHLD) {
        TRACE("SIGCHLD caught\n");
        Pid = waitpid(-1, &iStatus, WUNTRACED);
        if (WIFEXITED(iStatus))
            TRACE("EXITED child\n");   /* child finished and returned       */
        else if (WIFSIGNALED(iStatus))
            TRACE("SIGNALED child\n"); /* child finished due to a signal    */
        else if (WIFSTOPPED(iStatus))
            TRACE("STOPPED child\n");  /* child stopped due to a signal     */
    }
    else if (sig == SIGPIPE);          /* noop for now                      */
}

/* create channel */
static l2_result_t hook_create(l2_context_t *ctx, l2_channel_t *ch)
{
    l2_ch_pipe_t *cfg;

    /* allocate private channel configuration */
    if ((cfg = (l2_ch_pipe_t *)malloc(sizeof(l2_ch_pipe_t))) == NULL)
        return L2_ERR_ARG;

    /* initialize configuration with reasonable defaults */
    cfg->Pid        = -1;
    cfg->iWritefail =  0; 
    cfg->piFd[0]    = -1; 
    cfg->piFd[1]    = -1; 
    cfg->iMode      = -1; 
    cfg->szCmdpath  = NULL;
    memset(&cfg->sigchld, 0, sizeof(cfg->sigchld));
    memset(&cfg->sigpipe, 0, sizeof(cfg->sigpipe));

    /* link private channel configuration into channel context */
    ctx->vp = cfg;

    return L2_OK;
}

/* configure channel */
static l2_result_t hook_configure(l2_context_t *ctx, l2_channel_t *ch, const char *fmt, va_list ap)
{
    l2_ch_pipe_t *cfg = (l2_ch_pipe_t *)ctx->vp;
    l2_param_t pa[3]; 
    l2_result_t rv;
    FILE *File;
    char *szTemp;
    char *pbIndex;

    /* feed and call generic parameter parsing engine */
    L2_PARAM_SET(pa[0], mode, CHARPTR, &szTemp);
    L2_PARAM_SET(pa[1], path, STRING, &cfg->szCmdpath);
    L2_PARAM_END(pa[2]);
    if ((rv = l2_util_setparams(pa, fmt, ap)) != L2_OK)
        return rv;

    if (strcmp(szTemp, "direct") == NULL)
        cfg->iMode = L2_PIPE_MODEDIRECT;
    else if (strcmp(szTemp, "shell") == NULL)
        cfg->iMode = L2_PIPE_MODESHELL;
    else
        return L2_ERR_ARG;

    /* check to see if a file exists at the user specified path */
    if (cfg->iMode != L2_PIPE_MODESHELL) {
        szTemp = strdup(cfg->szCmdpath);
        for (pbIndex = szTemp; (*pbIndex != ' ') && (*pbIndex != NULL); pbIndex++);
        *pbIndex = NULL;
        if (!(File = fopen(szTemp, "r")))
            return L2_ERR_ARG; /* the command does not exist at the given path  */
        else
            fclose(File);
        free(szTemp);
        szTemp = NULL;
        pbIndex = NULL;
    }

    return rv;
}

/**********************************************************
 * parse_cmdpath: Helper method to hook_open              *
 *   Parses szBuf into an argv-style string vector szArgs *
 **********************************************************/
static l2_result_t parse_cmdpath (char *szBuf, char *szArgs[]) {
    int iCnt = 0;

    if (szBuf == NULL)     /* check for bad input before we  */
        return L2_ERR_ARG; /* dereference and throw a SIGSEV */

    while ((iCnt++ < L2_PIPE_MAXARGS) && (*szBuf != NULL)) {
        while ((*szBuf == ' ') || (*szBuf == '\t'))
            *szBuf++ = '\0'; /* overwrite whitespace with EOL  */
        *szArgs++ = szBuf;   /* found the start of a new token */
        while ((*szBuf != '\0') && (*szBuf != ' ') && (*szBuf != '\t'))
            szBuf++;
    }
    *szArgs = NULL; /* add a NULL to mark the end of the chain */

    if (iCnt <= L2_PIPE_MAXARGS)
        return L2_OK;
    else
        return L2_ERR_ARG;
}

/* open channel */
static l2_result_t hook_open(l2_context_t *ctx, l2_channel_t *ch)
{
    l2_ch_pipe_t *cfg = (l2_ch_pipe_t *)ctx->vp;
    char *pVec[L2_PIPE_MAXARGS];
    struct sigaction locact;
    l2_result_t rv;

    /* initialize auto vars before using them */
    memset(pVec, 0, sizeof(pVec));
    memset(&locact, 0, sizeof(locact));

    locact.sa_handler = (void(*)())catchsignal;
    sigemptyset(&locact.sa_mask);
    locact.sa_flags = 0;

    /* save old signal context before replacing with our own */
    if (sigaction(SIGCHLD, &locact, &cfg->sigchld) < 0)
        return L2_ERR_SYS;
    if (sigaction(SIGPIPE, &locact, &cfg->sigpipe) < 0)
        return L2_ERR_SYS;

    /* the distinction between modes is necessary, because only executing */
    /* commands in a shell environment allows usage of variables and such */
    if (cfg->iMode == L2_PIPE_MODESHELL) {
        pVec[0] = "/bin/sh";
        pVec[1] = "-c";
        pVec[2] = cfg->szCmdpath;
        pVec[3] = NULL; /* add a NULL to mark the end of the chain   */
    }

    else /* plain direct command execution */
        if ((rv = parse_cmdpath(cfg->szCmdpath, pVec)) != L2_OK)
            return rv;

    if (pipe(cfg->piFd) == -1)                /* open the pipe            */
        return L2_ERR_SYS;

    if ((cfg->Pid = fork()) > 0) {            /* parent process           */
        close(cfg->piFd[0]);                  /* half-duplex (no reading) */
        cfg->piFd[0] = -1;
    }
    else if (cfg->Pid == 0) {                 /* child process            */
        close(cfg->piFd[1]);                  /* close the writing end,   */
        cfg->piFd[1] = -1;                    /* because we don't use it  */
        dup2(cfg->piFd[0], fileno(stdin));    /* copy the reading end     */

        if (execvp(*pVec, pVec) == -1) {      /* launch                   */
            close(cfg->piFd[0]);              /* cleanup in case we fail  */
            cfg->piFd[0] = -1; /* if execvp() doesn't swap our context or */
            return L2_ERR_SYS; /* if child returns, we have an error      */
        }
    }
    else /* fork failed  */
        return L2_ERR_SYS;

    return L2_OK;
}

/* write to channel, possibly recursively */
static l2_result_t hook_write(l2_context_t *ctx, l2_channel_t *ch,
                              l2_level_t level, const char *buf, size_t buf_size)
{
    l2_ch_pipe_t *cfg = (l2_ch_pipe_t *)ctx->vp;

    /* write message to channel pipe */
    if (write(cfg->piFd[1], buf, buf_size) == -1) {
        if ((errno == EPIPE) && (cfg->iWritefail++ < 6)) {
            hook_close(ctx, ch);
            hook_open(ctx, ch);
            return hook_write(ctx, ch, level, buf, buf_size);
        }
        else { /* not broken pipe problem or over the fail limit */
            cfg->iWritefail = 0; /* reset pipe failure counter   */
            return L2_ERR_SYS;
        }
    }
    else {                   /* write() to pipe succeeded  */
        cfg->iWritefail = 0; /* reset pipe failure counter */
        return L2_OK;
    }
}

/* close channel */
static l2_result_t hook_close(l2_context_t *ctx, l2_channel_t *ch)
{
    l2_ch_pipe_t *cfg = (l2_ch_pipe_t *)ctx->vp;

    /* restore previous signal context */
    if (sigaction(SIGCHLD, &cfg->sigchld, NULL) < 0)
        return L2_ERR_SYS;
    if (sigaction(SIGPIPE, &cfg->sigpipe, NULL) < 0)
        return L2_ERR_SYS;

    /* close channel pipe for parent process created in hook_open() */
    close(cfg->piFd[1]);
    cfg->piFd[1] = -1;
    if ((kill (cfg->Pid, SIGTERM)) && (errno != ESRCH))
        return L2_ERR_SYS;

    cfg->Pid = -1;
    return L2_OK;
}

/* destroy channel */
static l2_result_t hook_destroy(l2_context_t *ctx, l2_channel_t *ch)
{
    l2_ch_pipe_t *cfg = (l2_ch_pipe_t *)ctx->vp;

    /* destroy channel configuration */
    free(cfg->szCmdpath);
    cfg->szCmdpath = NULL;
    free(cfg);

    return L2_OK;
}

/* exported channel handler structure */
l2_handler_t l2_handler_pipe = {
    L2_CHANNEL_OUTPUT,
    hook_create,
    hook_configure,
    hook_open,
    hook_write,
    NULL,
    hook_close,
    hook_destroy
};