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/*

 * Copyright (c) 2008 Jakub Jermar

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - 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.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * 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.

 */

/** @addtogroup fs

 * @{

 */

/**

 * @file    tmpfs_ops.c

 * @brief   Implementation of VFS operations for the TMPFS file system

 *      server.

 */

#include "tmpfs.h"

#include "../../vfs/vfs.h"

#include <ipc/ipc.h>

#include <async.h>

#include <errno.h>

#include <atomic.h>

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <assert.h>

#include <sys/types.h>

#include <libadt/hash_table.h>

#include <as.h>

#include <libfs.h>

#define min(a, b)       ((a) < (b) ? (a) : (b))

#define max(a, b)       ((a) > (b) ? (a) : (b))

#define DENTRIES_BUCKETS    256

#define NAMES_BUCKETS       4

/*

 * For now, we don't distinguish between different dev_handles/instances. All

 * requests resolve to the only instance, rooted in the following variable.

 */

static tmpfs_dentry_t *root;

/*

 * Implementation of the libfs interface.

 */

/* Forward declarations of static functions. */

static bool tmpfs_match(void *, void *, const char *);

static void *tmpfs_node_get(fs_handle_t, dev_handle_t, fs_index_t);

static void *tmpfs_create_node(int);

static bool tmpfs_link_node(void *, void *, const char *);

static int tmpfs_unlink_node(void *, void *);

static void tmpfs_destroy_node(void *);

/* Implementation of helper functions. */

static fs_index_t tmpfs_index_get(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->index;

}

static size_t tmpfs_size_get(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->size;

}

static unsigned tmpfs_lnkcnt_get(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->lnkcnt;

}

static void *tmpfs_child_get(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->child;

}

static void *tmpfs_sibling_get(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->sibling;

}

static void *tmpfs_root_get(void)

{

    return root;

}

static char tmpfs_plb_get_char(unsigned pos)

{

    return tmpfs_reg.plb_ro[pos % PLB_SIZE];

}

static bool tmpfs_is_directory(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->type == TMPFS_DIRECTORY;

}

static bool tmpfs_is_file(void *nodep)

{

    return ((tmpfs_dentry_t *) nodep)->type == TMPFS_FILE;

}

/** libfs operations */

libfs_ops_t tmpfs_libfs_ops = {

    .match = tmpfs_match,

    .node_get = tmpfs_node_get,

    .create = tmpfs_create_node,

    .destroy = tmpfs_destroy_node,

    .link = tmpfs_link_node,

    .unlink = tmpfs_unlink_node,

    .index_get = tmpfs_index_get,

    .size_get = tmpfs_size_get,

    .lnkcnt_get = tmpfs_lnkcnt_get,

    .child_get = tmpfs_child_get,

    .sibling_get = tmpfs_sibling_get,

    .root_get = tmpfs_root_get,

    .plb_get_char = tmpfs_plb_get_char,

    .is_directory = tmpfs_is_directory,

    .is_file = tmpfs_is_file

};

/** Hash table of all directory entries. */

hash_table_t dentries;

/* Implementation of hash table interface for the dentries hash table. */

static hash_index_t dentries_hash(unsigned long *key)

{

    return *key % DENTRIES_BUCKETS;

}

static int dentries_compare(unsigned long *key, hash_count_t keys,

    link_t *item)

{

    tmpfs_dentry_t *dentry = hash_table_get_instance(item, tmpfs_dentry_t,

        dh_link);

    return dentry->index == *key;

}

static void dentries_remove_callback(link_t *item)

{

}

/** TMPFS dentries hash table operations. */

hash_table_operations_t dentries_ops = {

    .hash = dentries_hash,

    .compare = dentries_compare,

    .remove_callback = dentries_remove_callback

};

fs_index_t tmpfs_next_index = 1;

typedef struct {

    char *name;

    tmpfs_dentry_t *parent;

    link_t link;

} tmpfs_name_t;

/* Implementation of hash table interface for the names hash table. */

static hash_index_t names_hash(unsigned long *key)

{

    tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) *key;

    return dentry->index % NAMES_BUCKETS;

}

static int names_compare(unsigned long *key, hash_count_t keys, link_t *item)

{

    tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) *key;

    tmpfs_name_t *namep = hash_table_get_instance(item, tmpfs_name_t,

        link);

    return dentry == namep->parent;

}

static void names_remove_callback(link_t *item)

{

    tmpfs_name_t *namep = hash_table_get_instance(item, tmpfs_name_t,

        link);

    free(namep->name);

    free(namep);

}

/** TMPFS node names hash table operations. */

static hash_table_operations_t names_ops = {

    .hash = names_hash,

    .compare = names_compare,

    .remove_callback = names_remove_callback

};

static void tmpfs_name_initialize(tmpfs_name_t *namep)

{

    namep->name = NULL;

    namep->parent = NULL;

    link_initialize(&namep->link);

}

static bool tmpfs_dentry_initialize(tmpfs_dentry_t *dentry)

{

    dentry->index = 0;

    dentry->sibling = NULL;

    dentry->child = NULL;

    dentry->type = TMPFS_NONE;

    dentry->lnkcnt = 0;

    dentry->size = 0;

    dentry->data = NULL;

    link_initialize(&dentry->dh_link);

    return (bool)hash_table_create(&dentry->names, NAMES_BUCKETS, 1,

        &names_ops);

}

static bool tmpfs_init(void)

{

    if (!hash_table_create(&dentries, DENTRIES_BUCKETS, 1, &dentries_ops))

        return false;

    root = (tmpfs_dentry_t *) tmpfs_create_node(L_DIRECTORY);

    if (!root) {

        hash_table_destroy(&dentries);

        return false;

    }

    root->lnkcnt = 1;

    return true;

}

/** Compare one component of path to a directory entry.

 *

 * @param prnt      Node from which we descended.

 * @param chld      Node to compare the path component with.

 * @param component Array of characters holding component name.

 *

 * @return      True on match, false otherwise.

 */

bool tmpfs_match(void *prnt, void *chld, const char *component)

{

    tmpfs_dentry_t *parentp = (tmpfs_dentry_t *) prnt;

    tmpfs_dentry_t *childp = (tmpfs_dentry_t *) chld;

    unsigned long key = (unsigned long) parentp;

    link_t *hlp = hash_table_find(&childp->names, &key);

    assert(hlp);

    tmpfs_name_t *namep = hash_table_get_instance(hlp, tmpfs_name_t, link);

    return !strcmp(namep->name, component);

}

void *

tmpfs_node_get(fs_handle_t fs_handle, dev_handle_t dev_handle, fs_index_t index)

{

    unsigned long key = index;

    link_t *lnk = hash_table_find(&dentries, &key);

    if (!lnk)

        return NULL;

    return hash_table_get_instance(lnk, tmpfs_dentry_t, dh_link);

}

void *tmpfs_create_node(int lflag)

{

    assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));

    tmpfs_dentry_t *node = malloc(sizeof(tmpfs_dentry_t));

    if (!node)

        return NULL;

    if (!tmpfs_dentry_initialize(node)) {

        free(node);

        return NULL;

    }

    node->index = tmpfs_next_index++;

    if (lflag & L_DIRECTORY)

        node->type = TMPFS_DIRECTORY;

    else

        node->type = TMPFS_FILE;

    /* Insert the new node into the dentry hash table. */

    unsigned long key = node->index;

    hash_table_insert(&dentries, &key, &node->dh_link);

    return (void *) node;

}

bool tmpfs_link_node(void *prnt, void *chld, const char *nm)

{

    tmpfs_dentry_t *parentp = (tmpfs_dentry_t *) prnt;

    tmpfs_dentry_t *childp = (tmpfs_dentry_t *) chld;

    assert(parentp->type == TMPFS_DIRECTORY);

    tmpfs_name_t *namep = malloc(sizeof(tmpfs_name_t));

    if (!namep)

        return false;

    tmpfs_name_initialize(namep);

    size_t len = strlen(nm);

    namep->name = malloc(len + 1);

    if (!namep->name) {

        free(namep);

        return false;

    }

    strcpy(namep->name, nm);

    namep->parent = parentp;

    childp->lnkcnt++;

    unsigned long key = (unsigned long) parentp;

    hash_table_insert(&childp->names, &key, &namep->link);

    /* Insert the new node into the namespace. */

    if (parentp->child) {

        tmpfs_dentry_t *tmp = parentp->child;

        while (tmp->sibling)

            tmp = tmp->sibling;

        tmp->sibling = childp;

    } else {

        parentp->child = childp;

    }

    return true;

}

int tmpfs_unlink_node(void *prnt, void *chld)

{

    tmpfs_dentry_t *parentp = (tmpfs_dentry_t *)prnt;

    tmpfs_dentry_t *childp = (tmpfs_dentry_t *)chld;

    if (!parentp)

        return EBUSY;

    if (childp->child)

        return ENOTEMPTY;

    if (parentp->child == childp) {

        parentp->child = childp->sibling;

    } else {

        /* TODO: consider doubly linked list for organizing siblings. */

        tmpfs_dentry_t *tmp = parentp->child;

        while (tmp->sibling != childp)

            tmp = tmp->sibling;

        tmp->sibling = childp->sibling;

    }

    childp->sibling = NULL;

    unsigned long key = (unsigned long) parentp;

    hash_table_remove(&childp->names, &key, 1);

    childp->lnkcnt--;

    return EOK;

}

void tmpfs_destroy_node(void *nodep)

{

    tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) nodep;

    assert(!dentry->lnkcnt);

    assert(!dentry->child);

    assert(!dentry->sibling);

    unsigned long key = dentry->index;

    hash_table_remove(&dentries, &key, 1);

    hash_table_destroy(&dentry->names);

    if (dentry->type == TMPFS_FILE)

        free(dentry->data);

    free(dentry);

}

void tmpfs_lookup(ipc_callid_t rid, ipc_call_t *request)

{

    /* Initialize TMPFS. */

    if (!root && !tmpfs_init()) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    libfs_lookup(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);

}

void tmpfs_read(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    off_t pos = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    unsigned long key = index;

    hlp = hash_table_find(&dentries, &key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    /*

     * Receive the read request.

     */

    ipc_callid_t callid;

    size_t len;

    if (!ipc_data_read_receive(&callid, &len)) {

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    size_t bytes;

    if (dentry->type == TMPFS_FILE) {

        bytes = max(0, min(dentry->size - pos, len));

        (void) ipc_data_read_finalize(callid, dentry->data + pos,

            bytes);

    } else {

        int i;

        tmpfs_dentry_t *cur;

        assert(dentry->type == TMPFS_DIRECTORY);

        /*

         * Yes, we really use O(n) algorithm here.

         * If it bothers someone, it could be fixed by introducing a

         * hash table.

         */

        for (i = 0, cur = dentry->child; i < pos && cur; i++,

            cur = cur->sibling)

            ;

        if (!cur) {

            ipc_answer_0(callid, ENOENT);

            ipc_answer_1(rid, ENOENT, 0);

            return;

        }

        unsigned long key = (unsigned long) dentry;

        link_t *hlp = hash_table_find(&cur->names, &key);

        assert(hlp);

        tmpfs_name_t *namep = hash_table_get_instance(hlp, tmpfs_name_t,

            link);

        (void) ipc_data_read_finalize(callid, namep->name,

            strlen(namep->name) + 1);

        bytes = 1;

    }

    /*

     * Answer the VFS_READ call.

     */

    ipc_answer_1(rid, EOK, bytes);

}

void tmpfs_write(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    off_t pos = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    unsigned long key = index;

    hlp = hash_table_find(&dentries, &key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    /*

     * Receive the write request.

     */

    ipc_callid_t callid;

    size_t len;

    if (!ipc_data_write_receive(&callid, &len)) {

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Check whether the file needs to grow.

     */

    if (pos + len <= dentry->size) {

        /* The file size is not changing. */

        (void) ipc_data_write_finalize(callid, dentry->data + pos, len);

        ipc_answer_2(rid, EOK, len, dentry->size);

        return;

    }

    size_t delta = (pos + len) - dentry->size;

    /*

     * At this point, we are deliberately extremely straightforward and

     * simply realloc the contents of the file on every write that grows the

     * file. In the end, the situation might not be as bad as it may look:

     * our heap allocator can save us and just grow the block whenever

     * possible.

     */

    void *newdata = realloc(dentry->data, dentry->size + delta);

    if (!newdata) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_2(rid, EOK, 0, dentry->size);

        return;

    }

    /* Clear any newly allocated memory in order to emulate gaps. */

    memset(newdata + dentry->size, 0, delta);

    dentry->size += delta;

    dentry->data = newdata;

    (void) ipc_data_write_finalize(callid, dentry->data + pos, len);

    ipc_answer_2(rid, EOK, len, dentry->size);

}

void tmpfs_truncate(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    size_t size = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    unsigned long key = index;

    hlp = hash_table_find(&dentries, &key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    if (size == dentry->size) {

        ipc_answer_0(rid, EOK);

        return;

    }

    void *newdata = realloc(dentry->data, size);

    if (!newdata) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    if (size > dentry->size) {

        size_t delta = size - dentry->size;

        memset(newdata + dentry->size, 0, delta);

    }

    dentry->size = size;

    dentry->data = newdata;

    ipc_answer_0(rid, EOK);

}

void tmpfs_destroy(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    link_t *hlp;

    unsigned long key = index;

    hlp = hash_table_find(&dentries, &key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    tmpfs_destroy_node(dentry);

    ipc_answer_0(rid, EOK);

}

/**

 * @}

 */