/*
  Copyright (c) 2008-2012 Red Hat, Inc. <http://www.redhat.com>
  This file is part of GlusterFS.

  This file is licensed to you under your choice of the GNU Lesser
  General Public License, version 3 or any later version (LGPLv3 or
  later), or the GNU General Public License, version 2 (GPLv2), in all
  cases as published by the Free Software Foundation.
*/

#include "glusterfs.h"
#include "logging.h"
#include "dict.h"
#include "xlator.h"
#include "list.h"
#include "compat.h"
#include "compat-errno.h"
#include "common-utils.h"
#include "symlink-cache-messages.h"

struct symlink_cache {
    time_t ctime;
    char *readlink;
};

static int
symlink_inode_ctx_get(inode_t *inode, xlator_t *this, void **ctx)
{
    int ret = 0;
    uint64_t tmp_ctx = 0;
    ret = inode_ctx_get(inode, this, &tmp_ctx);
    if (-1 == ret)
        gf_msg(this->name, GF_LOG_ERROR, EINVAL,
               SYMLINK_CACHE_MSG_DICT_GET_FAILED, "dict get failed");
    else
        *ctx = (void *)(long)tmp_ctx;

    return 0;
}

static int
symlink_inode_ctx_set(inode_t *inode, xlator_t *this, void *ctx)
{
    int ret = 0;
    ret = inode_ctx_put(inode, this, (uint64_t)(long)ctx);
    if (-1 == ret)
        gf_msg(this->name, GF_LOG_ERROR, EINVAL,
               SYMLINK_CACHE_MSG_DICT_SET_FAILED, "dict set failed");

    return 0;
}

int
sc_cache_update(xlator_t *this, inode_t *inode, const char *link)
{
    struct symlink_cache *sc = NULL;

    symlink_inode_ctx_get(inode, this, VOID(&sc));
    if (!sc)
        return 0;

    if (!sc->readlink) {
        gf_msg_debug(this->name, 0, "updating cache: %s", link);

        sc->readlink = strdup(link);
    } else
        gf_msg_debug(this->name, 0, "not updating existing cache: %s with %s",
                     sc->readlink, link);

    return 0;
}

int
sc_cache_set(xlator_t *this, inode_t *inode, struct iatt *buf, const char *link)
{
    struct symlink_cache *sc = NULL;
    int ret = -1;
    int need_set = 0;

    symlink_inode_ctx_get(inode, this, VOID(&sc));
    if (!sc) {
        need_set = 1;
        sc = CALLOC(1, sizeof(*sc));
        if (!sc) {
            gf_msg(this->name, GF_LOG_ERROR, ENOMEM,
                   SYMLINK_CACHE_MSG_NO_MEMORY, "out of memory :(");
            goto err;
        }
    }

    if (sc->readlink) {
        gf_msg_debug(this->name, 0,
                     "replacing old cache: %s with new cache: %s", sc->readlink,
                     link);
        FREE(sc->readlink);
        sc->readlink = NULL;
    }

    if (link) {
        sc->readlink = strdup(link);
        if (!sc->readlink) {
            gf_msg(this->name, GF_LOG_ERROR, ENOMEM,
                   SYMLINK_CACHE_MSG_NO_MEMORY, "out of memory :(");
            goto err;
        }
    }

    sc->ctime = buf->ia_ctime;

    gf_msg_debug(this->name, 0, "setting symlink cache: %s", link);

    if (need_set) {
        ret = symlink_inode_ctx_set(inode, this, sc);

        if (ret < 0) {
            gf_msg(this->name, GF_LOG_ERROR, -ret, SYMLINK_CACHE_MSG_NO_MEMORY,
                   "could not set inode context ");
            goto err;
        }
    }

    return 0;
err:

    if (sc) {
        FREE(sc->readlink);
        sc->readlink = NULL;
        FREE(sc);
    }

    return -1;
}

int
sc_cache_flush(xlator_t *this, inode_t *inode)
{
    struct symlink_cache *sc = NULL;

    symlink_inode_ctx_get(inode, this, VOID(&sc));
    if (!sc)
        return 0;

    if (sc->readlink) {
        gf_msg_debug(this->name, 0, "flushing cache: %s", sc->readlink);

        FREE(sc->readlink);
        sc->readlink = NULL;
    }

    FREE(sc);

    return 0;
}

int
sc_cache_validate(xlator_t *this, inode_t *inode, struct iatt *buf)
{
    struct symlink_cache *sc = NULL;
    uint64_t tmp_sc = 0;

    if (!IA_ISLNK(buf->ia_type)) {
        sc_cache_flush(this, inode);
        return 0;
    }

    symlink_inode_ctx_get(inode, this, VOID(&sc));

    if (!sc) {
        sc_cache_set(this, inode, buf, NULL);
        inode_ctx_get(inode, this, &tmp_sc);

        if (!tmp_sc) {
            gf_msg(this->name, GF_LOG_ERROR, 0, SYMLINK_CACHE_MSG_NO_MEMORY,
                   "out of memory :(");
            return 0;
        }
        sc = (struct symlink_cache *)(long)tmp_sc;
    }

    if (sc->ctime == buf->ia_ctime)
        return 0;

    /* STALE */
    if (sc->readlink) {
        gf_msg_debug(this->name, 0, "flushing cache: %s", sc->readlink);

        FREE(sc->readlink);
        sc->readlink = NULL;
    }

    sc->ctime = buf->ia_ctime;

    return 0;
}

int
sc_cache_get(xlator_t *this, inode_t *inode, char **link)
{
    struct symlink_cache *sc = NULL;

    symlink_inode_ctx_get(inode, this, VOID(&sc));

    if (!sc)
        return 0;

    if (link && sc->readlink)
        *link = strdup(sc->readlink);
    return 0;
}

int
sc_readlink_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int op_ret,
                int op_errno, const char *link, struct iatt *sbuf,
                dict_t *xdata)
{
    if (op_ret > 0)
        sc_cache_update(this, frame->local, link);

    inode_unref(frame->local);
    frame->local = NULL;

    STACK_UNWIND_STRICT(readlink, frame, op_ret, op_errno, link, sbuf, xdata);
    return 0;
}

int
sc_readlink(call_frame_t *frame, xlator_t *this, loc_t *loc, size_t size,
            dict_t *xdata)
{
    char *link = NULL;
    int op_ret = -1;
    struct iatt buf = {
        0,
    };

    sc_cache_get(this, loc->inode, &link);

    if (link) {
        /* cache hit */
        gf_msg_debug(this->name, 0, "cache hit %s -> %s", loc->path, link);

        /*
          libglusterfsclient, nfs or any other translators
          using buf in readlink_cbk should be aware that @buf
          is 0 filled
        */
        op_ret = strlen(link);
        STACK_UNWIND_STRICT(readlink, frame, op_ret, 0, link, &buf, NULL);
        FREE(link);
        return 0;
    }

    frame->local = inode_ref(loc->inode);

    STACK_WIND(frame, sc_readlink_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->readlink, loc, size, xdata);

    return 0;
}

int
sc_symlink_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int op_ret,
               int op_errno, inode_t *inode, struct iatt *buf,
               struct iatt *preparent, struct iatt *postparent, dict_t *xdata)
{
    if (op_ret == 0) {
        if (frame->local) {
            sc_cache_set(this, inode, buf, frame->local);
        }
    }

    STACK_UNWIND_STRICT(symlink, frame, op_ret, op_errno, inode, buf, preparent,
                        postparent, xdata);
    return 0;
}

int
sc_symlink(call_frame_t *frame, xlator_t *this, const char *dst, loc_t *src,
           mode_t umask, dict_t *xdata)
{
    frame->local = strdup(dst);

    STACK_WIND(frame, sc_symlink_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->symlink, dst, src, umask, xdata);

    return 0;
}

int
sc_lookup_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int op_ret,
              int op_errno, inode_t *inode, struct iatt *buf, dict_t *xdata,
              struct iatt *postparent)
{
    if (op_ret == 0)
        sc_cache_validate(this, inode, buf);
    else
        sc_cache_flush(this, inode);

    STACK_UNWIND_STRICT(lookup, frame, op_ret, op_errno, inode, buf, xdata,
                        postparent);
    return 0;
}

int
sc_lookup(call_frame_t *frame, xlator_t *this, loc_t *loc, dict_t *xdata)
{
    STACK_WIND(frame, sc_lookup_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->lookup, loc, xdata);

    return 0;
}

int
sc_forget(xlator_t *this, inode_t *inode)
{
    sc_cache_flush(this, inode);

    return 0;
}

int32_t
init(xlator_t *this)
{
    if (!this->children || this->children->next) {
        gf_msg(this->name, GF_LOG_ERROR, 0,
               SYMLINK_CACHE_MSG_XLATOR_CHILD_MISCONFIGURED,
               "FATAL: volume (%s) not configured with exactly one "
               "child",
               this->name);
        return -1;
    }

    if (!this->parents) {
        gf_msg(this->name, GF_LOG_WARNING, 0,
               SYMLINK_CACHE_MSG_VOL_MISCONFIGURED,
               "dangling volume. check volfile ");
    }

    return 0;
}

void
fini(xlator_t *this)
{
    return;
}

struct xlator_fops fops = {
    .lookup = sc_lookup,
    .symlink = sc_symlink,
    .readlink = sc_readlink,
};

struct xlator_cbks cbks = {
    .forget = sc_forget,
};

struct volume_options options[] = {
    {.key = {NULL}},
};