/*
**  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 <unistd.h>
#include <signal.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 */

/* declare private channel configuration */
typedef struct {
    int piFd[2];               /* pipe file descriptor           */
    int iMode;                 /* execution mode direct or shell */
    char *szCmdpath;          /* path to command and arguments  */
    char *pVec[L2_PIPE_MAXARGS]; /* vector of command and params */
} l2_ch_pipe_t;

static void catchsignal(int sig, ...)
{
    va_list ap;
    static l2_ch_pipe_t *cfg = NULL;

    va_start(ap, sig);
    if (sig == 0)
        cfg = va_arg(ap, l2_ch_pipe_t *);
    else if (sig == SIGCHLD) {
        fprintf(stderr, "Pipe: SIGCHLD caught\n");
        close(cfg->piFd[1]);
        cfg->piFd[1] = -1; /* TODO: Fill in with new pipe fd */
    }
    else if (sig == SIGPIPE) {
        fprintf(stderr, "Pipe: SIGPIPE caught\n");
        close(cfg->piFd[1]);
        cfg->piFd[1] = -1; /* TODO: Fill in with new pipe fd */
        /* ((l2_ch_pipe_t *)(int *)ctx->vp)->piFd[1] = -1; */
    }
    va_end(ap);
}

/* 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->piFd[0]    = -1; 
    cfg->piFd[1]    = -1; 
    cfg->iMode      = -1; 
    cfg->szCmdpath = NULL;
    memset(cfg->pVec, 0, sizeof(cfg->pVec));

    /* 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;
    char szMode[16]; /* just eneough for double-byte "direct" and NULL */

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

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

    catchsignal(0, cfg); /* initialize signal handler with incoming context */
    signal(SIGCHLD, (void(*)())catchsignal); /* pipe changes descriptor     */
    signal(SIGPIPE, (void(*)())catchsignal); /* pipe closes reading fd      */

    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;
    while ((iCnt++ < L2_PIPE_MAXARGS) && (*szBuf != NULL)) {
        while ((*szBuf == ' ') || (*szBuf == '\t'))
            *szBuf++ = '\0';
        *szArgs++ = szBuf;
        while ((*szBuf != '\0') && (*szBuf != ' ') && (*szBuf != '\t'))
            szBuf++;
    }
    *szArgs = NULL;

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

/**********************************************************
 * child_exec: Helper method to hook_open                 *
 *   Redirect stdin to read from cfg->piFd. Exec a given  *
 *   command or passes it to the sh shell for execution.  *
 **********************************************************/
static l2_result_t child_exec(l2_ch_pipe_t *cfg)
{
    /* make sure a command path was set */
    if (cfg->szCmdpath == NULL)
        return L2_ERR_USE;

        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    */

        return execvp(*cfg->pVec, cfg->pVec); /* launch                  */
}

/* 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;
    l2_result_t rv;
    pid_t Pid;

    if ((rv = parse_cmdpath(cfg->szCmdpath, cfg->pVec)) != L2_OK)
        return rv;

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

    if ((Pid = fork()) > 0) {       /* parent process */
        close(cfg->piFd[0]);
        cfg->piFd[0] = -1;
    }
    else if ((Pid = fork()) == 0) { /* child process  */
        /* if child returns, there was an error       */
        if (child_exec(cfg) == -1) {
            close(cfg->piFd[0]);
            cfg->piFd[0] = -1;
            return L2_ERR_SYS;
        }
    }
    else /* fork failed  */
        return L2_ERR_SYS;

    return L2_OK;
}

/* write to channel */
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;

    /* validate the pipe fd */
    if (cfg->piFd[1] == -1)  /* TODO: possibly remove this validation in */
        return L2_ERR_ARG;   /*       lieu of incoming SIGPIPE signal    */

    /* write message to channel pipe */
    if (write(cfg->piFd[1], buf, buf_size) == -1)
        return L2_ERR_SYS;

    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;

    /* close channel pipe for parent process created in hook_open() */
    close(cfg->piFd[1]);
    cfg->piFd[1] = -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
};