/*-
 * Copyright (c) 2017 Juniper Networks, Inc.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 *
 */
/*-
 * 9P filesystem subroutines. This file consists of all the Non VFS subroutines.
 * It contains all of the functions related to the driver submission which form
 * the upper layer i.e, p9fs driver. This will interact with the client to make
 * sure we have correct API calls in the header.
 */

#include <sys/cdefs.h>
#include <sys/systm.h>
#include <sys/limits.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>

#include "p9fs_proto.h"

#include <fs/p9fs/p9_client.h>
#include <fs/p9fs/p9_debug.h>
#include <fs/p9fs/p9_protocol.h>
#include <fs/p9fs/p9fs.h>

int
p9fs_proto_dotl(struct p9fs_session *vses)
{

        return (vses->flags & P9FS_PROTO_2000L);
}

/* Initialize a p9fs session */
struct p9_fid *
p9fs_init_session(struct mount *mp, int *error)
{
        struct p9fs_session *vses;
        struct p9fs_mount *virtmp;
        struct p9_fid *fid;
        char *access;

        virtmp = VFSTOP9(mp);
        vses = &virtmp->p9fs_session;
        vses->uid = P9_NONUNAME;
        vses->uname = P9_DEFUNAME;
        vses->aname = P9_DEFANAME;

        /*
         * Create the client structure. Call into the driver to create
         * driver structures for the actual IO transfer.
         */
        vses->clnt = p9_client_create(mp, error, virtmp->mount_tag);

        if (vses->clnt == NULL) {
                P9_DEBUG(ERROR, "%s: p9_client_create failed\n", __func__);
                return (NULL);
        }
        /*
         * Find the client version and cache the copy. We will use this copy
         * throughout FS layer.
         */
        if (p9_is_proto_dotl(vses->clnt))
                vses->flags |= P9FS_PROTO_2000L;
        else if (p9_is_proto_dotu(vses->clnt))
                vses->flags |= P9FS_PROTO_2000U;

        /* Set the access mode */
        access = vfs_getopts(mp->mnt_optnew, "access", error);
        if (access == NULL)
                vses->flags |= P9_ACCESS_USER;
        else if (!strcmp(access, "any"))
                vses->flags |= P9_ACCESS_ANY;
        else if (!strcmp(access, "single"))
                vses->flags |= P9_ACCESS_SINGLE;
        else if (!strcmp(access, "user"))
                vses->flags |= P9_ACCESS_USER;
        else {
                P9_DEBUG(ERROR, "%s: unknown access mode\n", __func__);
                *error = EINVAL;
                goto out;
        }

        *error = 0;
        /* Attach with the backend host*/
        fid = p9_client_attach(vses->clnt, NULL, vses->uname, P9_NONUNAME,
            vses->aname, error);
        vses->mnt_fid = fid;

        if (*error != 0) {
                P9_DEBUG(ERROR, "%s: attach failed: %d\n", __func__, *error);
                goto out;
        }
        P9_DEBUG(SUBR, "%s: attach successful fid :%p\n", __func__, fid);
        fid->uid = vses->uid;

        /* initialize the node list for the session */
        STAILQ_INIT(&vses->virt_node_list);
        P9FS_LOCK_INIT(vses);

        P9_DEBUG(SUBR, "%s: INIT session successful\n", __func__);

        return (fid);
out:
        p9_client_destroy(vses->clnt);
        return (NULL);
}

/* Begin to terminate a session */
void
p9fs_prepare_to_close(struct mount *mp)
{
        struct p9fs_session *vses;
        struct p9fs_mount *vmp;
        struct p9fs_node *np, *pnp, *tmp;

        vmp = VFSTOP9(mp);
        vses = &vmp->p9fs_session;

        /* break the node->parent references */
        STAILQ_FOREACH_SAFE(np, &vses->virt_node_list, p9fs_node_next, tmp) {
                if (np->parent && np->parent != np) {
                        pnp = np->parent;
                        np->parent = NULL;
                        vrele(P9FS_NTOV(pnp));
                }
        }

        /* We are about to teardown, we dont allow anything other than clunk after this.*/
        p9_client_begin_disconnect(vses->clnt);
}

/* Shutdown a session */
void
p9fs_complete_close(struct mount *mp)
{
        struct p9fs_session *vses;
        struct p9fs_mount *vmp;

        vmp = VFSTOP9(mp);
        vses = &vmp->p9fs_session;

        /* Finish the close*/
        p9_client_disconnect(vses->clnt);
}


/* Call from unmount. Close the session. */
void
p9fs_close_session(struct mount *mp)
{
        struct p9fs_session *vses;
        struct p9fs_mount *vmp;

        vmp = VFSTOP9(mp);
        vses = &vmp->p9fs_session;

        p9fs_complete_close(mp);
        /* Clean up the clnt structure. */
        p9_client_destroy(vses->clnt);
        P9FS_LOCK_DESTROY(vses);
        P9_DEBUG(SUBR, "%s: Clean close session .\n", __func__);
}

/*
 * Remove all the fids of a particular type from a p9fs node
 * as well as destroy/clunk them.
 */
void
p9fs_fid_remove_all(struct p9fs_node *np, int leave_ofids)
{
        struct p9_fid *fid, *tfid;

        STAILQ_FOREACH_SAFE(fid, &np->vfid_list, fid_next, tfid) {
                STAILQ_REMOVE(&np->vfid_list, fid, p9_fid, fid_next);
                p9_client_clunk(fid);
        }

        if (!leave_ofids) {
                STAILQ_FOREACH_SAFE(fid, &np->vofid_list, fid_next, tfid) {
                        STAILQ_REMOVE(&np->vofid_list, fid, p9_fid, fid_next);
                        p9_client_clunk(fid);
                }
        }
}


/* Remove a fid from its corresponding fid list */
void
p9fs_fid_remove(struct p9fs_node *np, struct p9_fid *fid, int fid_type)
{

        switch (fid_type) {
        case VFID:
                P9FS_VFID_LOCK(np);
                STAILQ_REMOVE(&np->vfid_list, fid, p9_fid, fid_next);
                P9FS_VFID_UNLOCK(np);
                break;
        case VOFID:
                P9FS_VOFID_LOCK(np);
                STAILQ_REMOVE(&np->vofid_list, fid, p9_fid, fid_next);
                P9FS_VOFID_UNLOCK(np);
                break;
        }
}

/* Add a fid to the corresponding fid list */
void
p9fs_fid_add(struct p9fs_node *np, struct p9_fid *fid, int fid_type)
{

        switch (fid_type) {
        case VFID:
                P9FS_VFID_LOCK(np);
                STAILQ_INSERT_TAIL(&np->vfid_list, fid, fid_next);
                P9FS_VFID_UNLOCK(np);
                break;
        case VOFID:
                P9FS_VOFID_LOCK(np);
                STAILQ_INSERT_TAIL(&np->vofid_list, fid, fid_next);
                P9FS_VOFID_UNLOCK(np);
                break;
        }
}

/* Build the path from root to current directory */
static int
p9fs_get_full_path(struct p9fs_node *np, char ***names)
{
        int i, n;
        struct p9fs_node *node;
        char **wnames;

        n = 0;
        for (node = np ; (node != NULL) && !IS_ROOT(node) ; node = node->parent)
                n++;

        if (node == NULL)
                return (0);

        wnames = malloc(n * sizeof(char *), M_TEMP, M_ZERO|M_WAITOK);

        for (i = n-1, node = np; i >= 0 ; i--, node = node->parent)
                wnames[i] = node->inode.i_name;

        *names = wnames;
        return (n);
}

/*
 * Return TRUE if this fid can be used for the requested mode.
 */
static int
p9fs_compatible_mode(struct p9_fid *fid, int mode)
{
        /*
         * Return TRUE for an exact match. For OREAD and OWRITE, allow
         * existing ORDWR fids to match. Only check the low two bits
         * of mode.
         *
         * TODO: figure out if this is correct for O_APPEND
         */
        int fid_mode = fid->mode & 3;
        if (fid_mode == mode)
                return (TRUE);
        if (fid_mode == P9PROTO_ORDWR)
                return (mode == P9PROTO_OREAD || mode == P9PROTO_OWRITE);
        return (FALSE);
}

/*
 * Retrieve fid structure corresponding to a particular
 * uid and fid type for a p9fs node
 */
static struct p9_fid *
p9fs_get_fid_from_uid(struct p9fs_node *np, uid_t uid, int fid_type, int mode)
{
        struct p9_fid *fid;

        switch (fid_type) {
        case VFID:
                P9FS_VFID_LOCK(np);
                STAILQ_FOREACH(fid, &np->vfid_list, fid_next) {
                        if (fid->uid == uid) {
                                P9FS_VFID_UNLOCK(np);
                                return (fid);
                        }
                }
                P9FS_VFID_UNLOCK(np);
                break;
        case VOFID:
                P9FS_VOFID_LOCK(np);
                STAILQ_FOREACH(fid, &np->vofid_list, fid_next) {
                        if (fid->uid == uid && p9fs_compatible_mode(fid, mode)) {
                                P9FS_VOFID_UNLOCK(np);
                                return (fid);
                        }
                }
                P9FS_VOFID_UNLOCK(np);
                break;
        }

        return (NULL);
}

/*
 * Function returns the fid sturcture for a file corresponding to current user id.
 * First it searches in the fid list of the corresponding p9fs node.
 * New fid will be created if not already present and added in the corresponding
 * fid list in the p9fs node.
 * If the user is not already attached then this will attach the user first
 * and then create a new fid for this particular file by doing dir walk.
 */
struct p9_fid *
p9fs_get_fid(struct p9_client *clnt, struct p9fs_node *np, struct ucred *cred,
    int fid_type, int mode, int *error)
{
        uid_t uid;
        struct p9_fid *fid, *oldfid;
        struct p9fs_node *root;
        struct p9fs_session *vses;
        int i, l, clone;
        char **wnames = NULL;
        uint16_t nwnames;

        oldfid = NULL;
        vses = np->p9fs_ses;

        if (vses->flags & P9_ACCESS_ANY)
                uid = vses->uid;
        else if (cred)
                uid = cred->cr_uid;
        else
                uid = 0;

        /*
         * Search for the fid in corresponding fid list.
         * We should return NULL for VOFID if it is not present in the list.
         * Because VOFID should have been created during the file open.
         * If VFID is not present in the list then we should create one.
         */
        fid = p9fs_get_fid_from_uid(np, uid, fid_type, mode);
        if (fid != NULL || fid_type == VOFID)
                return (fid);

        /* Check root if the user is attached */
        root = &np->p9fs_ses->rnp;
        fid = p9fs_get_fid_from_uid(root, uid, fid_type, mode);
        if(fid == NULL) {
                /* Attach the user */
                fid = p9_client_attach(clnt, NULL, NULL, uid,
                    vses->aname, error);
                if (*error != 0)
                        return (NULL);
                p9fs_fid_add(root, fid, fid_type);
        }

        /* If we are looking for root then return it */
        if (IS_ROOT(np))
                return (fid);

        /* Get full path from root to p9fs node */
        nwnames = p9fs_get_full_path(np, &wnames);

        /*
         * Could not get full path.
         * If p9fs node is not deleted, parent should exist.
         */
        KASSERT(nwnames != 0, ("%s: Directory of %s doesn't exist", __func__, np->inode.i_name));

        clone = 1;
        i = 0;
        while (i < nwnames) {
                l = MIN(nwnames - i, P9_MAXWELEM);

                fid = p9_client_walk(fid, l, wnames, clone, error);
                if (*error != 0) {
                        if (oldfid)
                                p9_client_clunk(oldfid);
                        fid = NULL;
                        goto bail_out;
                }
                oldfid = fid;
                clone = 0;
                i += l ;
        }
        p9fs_fid_add(np, fid, fid_type);
bail_out:
        free(wnames, M_TEMP);
        return (fid);
}