/* Copyright (C) 2014 Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * shim_fs.h
 *
 * Definitions of types and functions for file system bookkeeping.
 */

#ifndef _SHIM_FS_H_
#define _SHIM_FS_H_

#include <stdbool.h>

#include <list.h>
#include <pal.h>
#include <shim_defs.h>
#include <shim_handle.h>
#include <shim_types.h>
#include <shim_utils.h>

struct shim_handle;

#define FS_POLL_RD 0x01
#define FS_POLL_WR 0x02
#define FS_POLL_ER 0x04
#define FS_POLL_SZ 0x08

struct shim_fs_ops {
    /* mount: mount an uri to the certain location */
    int (*mount)(const char* uri, void** mount_data);
    int (*unmount)(void* mount_data);

    /* close: clean up the file state inside the handle */
    int (*close)(struct shim_handle* hdl);

    /* read: the content from the file opened as handle */
    ssize_t (*read)(struct shim_handle* hdl, void* buf, size_t count);

    /* write: the content from the file opened as handle */
    ssize_t (*write)(struct shim_handle* hdl, const void* buf, size_t count);

    /* mmap: mmap handle to address */
    int (*mmap)(struct shim_handle* hdl, void** addr, size_t size, int prot, int flags,
                off_t offset);

    /* flush: flush out user buffer */
    int (*flush)(struct shim_handle* hdl);

    /* seek: the content from the file opened as handle */
    off_t (*seek)(struct shim_handle* hdl, off_t offset, int wence);

    /* move, copy: rename or duplicate the file */
    int (*move)(const char* trim_old_name, const char* trim_new_name);
    int (*copy)(const char* trim_old_name, const char* trim_new_name);

    /* Returns 0 on success, -errno on error */
    int (*truncate)(struct shim_handle* hdl, off_t len);

    /* hstat: get status of the file */
    int (*hstat)(struct shim_handle* hdl, struct stat* buf);

    /* setflags: set flags of the file */
    int (*setflags)(struct shim_handle* hdl, int flags);

    /* hput: delete the handle and close the PAL handle. */
    void (*hput)(struct shim_handle* hdl);

    /* lock and unlock the file */
    int (*lock)(const char* trim_name);
    int (*unlock)(const char* trim_name);

    /* lock and unlock the file system */
    int (*lockfs)(void);
    int (*unlockfs)(void);

    /* checkout/reowned/checkin a single handle for migration */
    int (*checkout)(struct shim_handle* hdl);
    int (*checkin)(struct shim_handle* hdl);

    /* poll a single handle */
    /* POLL_RD|POLL_WR: return POLL_RD|POLL_WR for readable|writable,
       POLL_ER for failure, -EAGAIN for unknown. */
    /* POLL_SZ: return total size */
    off_t (*poll)(struct shim_handle* hdl, int poll_type);

    /* checkpoint/migrate the file system */
    ssize_t (*checkpoint)(void** checkpoint, void* mount_data);
    int (*migrate)(void* checkpoint, void** mount_data);
};

#define DENTRY_VALID       0x0001 /* this dentry is verified to be valid */
#define DENTRY_NEGATIVE    0x0002 /* recently deleted or inaccessible */
#define DENTRY_RECENTLY    0x0004 /* recently used */
#define DENTRY_PERSIST     0x0008 /* added as a persistent dentry */
#define DENTRY_HASHED      0x0010 /* added in the dcache */
#define DENTRY_MOUNTPOINT  0x0040 /* this dentry is a mount point */
#define DENTRY_ISLINK      0x0080 /* this dentry is a link */
#define DENTRY_ISDIRECTORY 0x0100 /* this dentry is a directory */
#define DENTRY_LOCKED      0x0200 /* locked by mountpoints at children */
/* These flags are not used */
//#define DENTRY_REACHABLE    0x0400  /* permission checked to be reachable */
//#define DENTRY_UNREACHABLE  0x0800  /* permission checked to be unreachable */
#define DENTRY_LISTED      0x1000 /* children in directory listed */
#define DENTRY_INO_UPDATED 0x2000 /* ino updated */
#define DENTRY_ANCESTOR    0x4000 /* Auto-generated dentry to connect a mount point in the        \
                                   * manifest to the root, when one or more intermediate          \
                                   * directories do not exist on the underlying FS. The semantics \
                                   * of subsequent changes to such directories (or attempts to    \
                                   * really create them) are not currently well-defined. */

// Catch memory corruption issues by checking for invalid state values
#define DENTRY_INVALID_FLAGS (~0x7FFF)

#define DCACHE_HASH_SIZE  1024
#define DCACHE_HASH(hash) ((hash) & (DCACHE_HASH_SIZE - 1))

DEFINE_LIST(shim_dentry);
DEFINE_LISTP(shim_dentry);
struct shim_dentry {
    int state; /* flags for managing state */

    struct shim_mount* fs;     /* this dentry's mounted fs */
    struct shim_qstr rel_path; /* the path is relative to its mount point */
    struct shim_qstr name;     /* caching the file's name. */

    /* DEP 6/16/17: For now, let's try not hashing; I suspect it is overkill for most purposes.
     * I'll leave the field here for now, but propose we move to a per-directory table to accelerate
     * lookups, rather than a global table, since this just supports one process.
     */
    LIST_TYPE(shim_dentry) hlist; /* to resolve collisions in the hash table */
    LIST_TYPE(shim_dentry) list; /* put dentry to different list according to its availability, \
                                  * persistent or freeable */

    struct shim_dentry* parent;
    int nchildren;
    LISTP_TYPE(shim_dentry) children; /* These children and siblings link */
    LIST_TYPE(shim_dentry) siblings;

    struct shim_mount* mounted;
    void* data;
    unsigned long ino;
    mode_t type;
    mode_t mode;

    struct shim_lock lock;
    REFTYPE ref_count;
};

struct shim_d_ops {
    /* open: provide a filename relative to the mount point and flags,
       modify the shim handle, file_data is "inode" equivalent */
    int (*open)(struct shim_handle* hdl, struct shim_dentry* dent, int flags);

    /* look up dentry and allocate internal data.
     *
     * On a successful lookup  (non-error, can be negative),
     * this function should call get_new_dentry(), populating additional fields,
     * and storing the new dentry in dent.
     */
    int (*lookup)(struct shim_dentry* dent);

    /* this is to check file type and access, returning the stat.st_mode */
    int (*mode)(struct shim_dentry* dent, mode_t* mode);

    /* detach internal data from dentry */
    int (*dput)(struct shim_dentry* dent);

    /* create a dentry inside a directory */
    int (*creat)(struct shim_handle* hdl, struct shim_dentry* dir, struct shim_dentry* dent,
                 int flags, mode_t mode);

    /* unlink a dentry inside a directory */
    int (*unlink)(struct shim_dentry* dir, struct shim_dentry* dent);

    /* create a directory inside a directory */
    int (*mkdir)(struct shim_dentry* dir, struct shim_dentry* dent, mode_t mode);

    /* stat: get status of the file */
    int (*stat)(struct shim_dentry* dent, struct stat* buf);

    /* extracts the symlink name and saves in link */
    int (*follow_link)(struct shim_dentry* dent, struct shim_qstr* link);
    /* set up symlink name to a dentry */
    int (*set_link)(struct shim_dentry* dent, const char* link);

    /* change the mode or owner of a dentry */
    int (*chmod)(struct shim_dentry* dent, mode_t mode);
    int (*chown)(struct shim_dentry* dent, int uid, int gid);

    /* change the name of a dentry */
    int (*rename)(struct shim_dentry* old, struct shim_dentry* new);

    /* readdir: given the path relative to the mount point, read the childs
       into the the buffer.  This call always returns everything under
       the directory in one big buffer; you do not need to try again
       or keep a cursor in the directory.  You do need to free the
       returned buffer. */
    int (*readdir)(struct shim_dentry* dent, struct shim_dirent** dirent);
};

#define MAX_PATH     4096
#define MAX_FILENAME 255

DEFINE_LIST(shim_mount);
struct shim_mount {
    char type[8];  // Null-terminated.

    struct shim_dentry* mount_point;

    struct shim_qstr path;
    struct shim_qstr uri;

    struct shim_fs_ops* fs_ops;
    struct shim_d_ops* d_ops;

    struct shim_dentry* root;

    void* data;

    void* cpdata;
    size_t cpsize;

    REFTYPE ref_count;
    LIST_TYPE(shim_mount) hlist;
    LIST_TYPE(shim_mount) list;
};

extern struct shim_dentry* dentry_root;

#define LOOKUP_FOLLOW    001
#define LOOKUP_DIRECTORY 002
#define LOOKUP_CONTINUE  004  // No longer needed
#define LOOKUP_PARENT    010  // Not sure we need this

#define F_OK 0
// XXX: Duplicate definition; should probably weed out includes of host system
// include of unistd.h in future work
//#define R_OK        001
//#define W_OK        002
//#define X_OK        004
#define MAY_EXEC  001
#define MAY_WRITE 002
#define MAY_READ  004
#if 0
#define MAY_APPEND 010
#endif

#define NO_MODE ((mode_t)-1)

#define ACC_MODE(x)                                        \
    ((((x) == O_RDONLY || (x) == O_RDWR) ? MAY_READ : 0) | \
     (((x) == O_WRONLY || (x) == O_RDWR) ? MAY_WRITE : 0))

#define LOOKUP_OPEN   0100  // Appears to be ignored
#define LOOKUP_CREATE 0200
#define LOOKUP_ACCESS 0400  // Appears to be ignored
#define LOOKUP_SYNC   (LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_ACCESS)

enum lookup_type {
    LAST_NORM,
    LAST_ROOT,
    LAST_DOT,
    LAST_DOTDOT,
    LAST_BIND
};

struct lookup {
    struct shim_dentry* dentry;
    struct shim_mount* mount;
    const char* last;
    int depth;
    int flags;
    enum lookup_type last_type;
};

/* initialization for fs and mounts */
int init_fs(void);
int init_mount_root(void);
int init_mount(void);

/* path utilities */
const char* get_file_name(const char* path, size_t len);

/* file system operations */
int mount_fs(const char* mount_type, const char* mount_uri, const char* mount_point,
             struct shim_dentry* parent, struct shim_dentry** dentp, bool make_ancestor);
int unmount_fs(const char* mount_point);
int search_builtin_fs(const char* type, struct shim_mount** fs);

void get_mount(struct shim_mount* mount);
void put_mount(struct shim_mount* mount);

struct shim_mount* find_mount_from_uri(const char* uri);

#include <shim_utils.h>

static inline void set_handle_fs(struct shim_handle* hdl, struct shim_mount* fs) {
    get_mount(fs);
    hdl->fs = fs;
    memcpy(hdl->fs_type, fs->type, sizeof(hdl->fs_type));
}

int walk_mounts(int (*walk)(struct shim_mount* mount, void* arg), void* arg);

/* functions for dcache supports */
int init_dcache(void);

extern struct shim_lock dcache_lock;

/* Checks permission (specified by mask) of a dentry. If force is not set, permission is considered
 * granted on invalid dentries.
 * Assumes that caller has acquired dcache_lock. */
int permission(struct shim_dentry* dent, mode_t mask);

/* This function looks up a single dentry based on its parent dentry pointer and the name. `namelen`
 * is the length of char* name. The dentry is returned in pointer *new.
 *
 * The caller should hold the dcache_lock.
 */
int lookup_dentry(struct shim_dentry* parent, const char* name, int namelen,
                  struct shim_dentry** new, struct shim_mount* fs);

/* Looks up path under start dentry. Saves in dent.
 *
 * Assumes dcache_lock is held; main difference from path_lookupat is that dcache_lock is not
 * released on return.
 *
 * The refcount is dropped by one on the returned dentry.
 *
 * The make_ancestor flag creates pseudo-dentries for any parent paths that are not in cache and do
 * not exist on the underlying file system. This is intended for use only in setting up the
 * file system view specified in the manifest.
 *
 * If the file isnt' found, returns -ENOENT.
 *
 * If the LOOKUP_DIRECTORY flag is set, and the found file isn't a directory, returns -ENOTDIR.
 */
int __path_lookupat(struct shim_dentry* start, const char* path, int flags,
                    struct shim_dentry** dent, int link_depth, struct shim_mount* fs,
                    bool make_ancestor);

/* Just wraps __path_lookupat, but also acquires and releases the dcache_lock. */
int path_lookupat(struct shim_dentry* start, const char* name, int flags, struct shim_dentry** dent,
                  struct shim_mount* fs);

/*
 * This function returns a dentry (in *dir) from a handle corresponding to dirfd.
 * If dirfd == AT_FDCWD returns current working directory.
 *
 * Returned dentry must be a directory.
 *
 * Increments dentry ref count by one.
 */
int get_dirfd_dentry(int dirfd, struct shim_dentry** dir);

/* Open path with given flags, in mode, similar to Unix open.
 *
 * The start dentry specifies where to begin the search.
 * `hdl` is an optional argument; if passed in, it is initialized to refer to the opened path.
 *
 * The result is stored in `dent`.
 */

int open_namei(struct shim_handle* hdl, struct shim_dentry* start, const char* path, int flags,
               int mode, struct shim_dentry** dent);

/* This function calls the low-level file system to do the work of opening file indicated by dent,
 * and initializing it in hdl. Flags are standard open flags.
 *
 * If O_TRUNC is specified, this function is responsible for calling the underlying truncate
 * function.
 */

int dentry_open(struct shim_handle* hdl, struct shim_dentry* dent, int flags);

/* This function enumerates a directory and caches the results in the dentry.
 *
 * Input: A dentry for a directory in the DENTRY_ISDIRECTORY and not in the DENTRY_LISTED state.
 * The dentry DENTRY_LISTED flag is set upon success.
 *
 * Return value: 0 on success, <0 on error
 */
int list_directory_dentry(struct shim_dentry* dir);

/* This function caches the contents of a directory (dent), already in the listed state, in a buffer
 * associated with a handle (hdl).
 *
 * This function should only be called once on a handle.
 *
 * Returns 0 on success, <0 on failure.
 */
int list_directory_handle(struct shim_dentry* dent, struct shim_handle* hdl);

/* Increment the reference count on dent */
void get_dentry(struct shim_dentry* dent);
/* Decrement the reference count on dent */
void put_dentry(struct shim_dentry* dent);

static_always_inline void fast_pathcpy(char* dst, const char* src, size_t size, char** ptr) {
    char* d       = dst;
    const char* s = src;
    for (size_t i = 0; i < size; i++, s++, d++)
        *d = *s;
    *ptr = d;
}

static_always_inline char* dentry_get_path(struct shim_dentry* dent, bool on_stack,
                                           size_t* sizeptr) {
    struct shim_mount* fs = dent->fs;
    char* buffer;
    char* c;
    size_t bufsize = dent->rel_path.len + 1;

    if (fs)
        bufsize += fs->path.len + 1;

    if (on_stack) {
        c = buffer = __alloca(bufsize);
    } else {
        if (!(c = buffer = malloc(bufsize)))
            return NULL;
    }

    if (fs && !qstrempty(&fs->path))
        fast_pathcpy(c, qstrgetstr(&fs->path), fs->path.len, &c);

    if (dent->rel_path.len) {
        const char* path = qstrgetstr(&dent->rel_path);
        int len          = dent->rel_path.len;

        if (c > buffer && *(c - 1) == '/') {
            if (*path == '/')
                path++;
        } else {
            if (*path != '/')
                *(c++) = '/';
        }

        fast_pathcpy(c, path, len, &c);
    }

    if (sizeptr)
        *sizeptr = c - buffer;

    *c = 0;
    return buffer;
}

static_always_inline const char* dentry_get_name(struct shim_dentry* dent) {
    return qstrgetstr(&dent->name);
}

/* Allocate and initialize a new dentry for path name, under parent.  Return the dentry.
 *
 * `mount` is the mountpoint the dentry is under; this is typically the parent->fs, but is passed
 * explicitly for initializing the dentry of a mountpoint.
 *
 * If hashptr is passed (as an optimization), this is a hash of the name.
 *
 * If parent is non-null, the ref count is 2; else it is 1.
 *
 * This function also sets up both a name and a relative path
 */
struct shim_dentry* get_new_dentry(struct shim_mount* mount, struct shim_dentry* parent,
                                   const char* name, int namelen, HASHTYPE* hashptr);

/* This function searches for name/namelen (as the relative path).
 *
 * If requested, the expected hash of the dentry is returned in hashptr, primarily so that the
 * hashing can be reused to add the dentry later.
 *
 * The reference count on the found dentry is incremented by one.
 *
 * Used only by shim_namei.c
 */
struct shim_dentry* __lookup_dcache(struct shim_dentry* start, const char* name, int namelen,
                                    HASHTYPE* hashptr);

/* This function recursively deletes and frees all dentries under root
 *
 * XXX: Current code doesn't do a free..
 */
int __del_dentry_tree(struct shim_dentry* root);

/*
 * Returns true if `anc` is an ancestor of `dent`.
 */
bool dentry_is_ancestor(struct shim_dentry* anc, struct shim_dentry* dent);

/* XXX: Future work: current dcache never shrinks. Would be nice to be able to do something like LRU
 * under space pressure, although for a single app, this may be over-kill. */

/* hashing utilities */
#define MOUNT_HASH_BYTE  1
#define MOUNT_HASH_WIDTH 8
#define MOUNT_HASH_SIZE  256

#define MOUNT_HASH(hash) ((hash) & (MOUNT_HASH_SIZE - 1))

HASHTYPE hash_path(const char* path, size_t size);
HASHTYPE rehash_name(HASHTYPE parent_hbuf, const char* name, size_t size);
HASHTYPE rehash_path(HASHTYPE ancester_hbuf, const char* path, size_t size);

extern struct shim_fs_ops chroot_fs_ops;
extern struct shim_d_ops chroot_d_ops;

extern struct shim_fs_ops str_fs_ops;
extern struct shim_d_ops str_d_ops;

extern struct shim_fs_ops dev_fs_ops;
extern struct shim_d_ops dev_d_ops;

extern struct shim_fs_ops config_fs_ops;
extern struct shim_d_ops config_d_ops;

extern struct shim_fs_ops proc_fs_ops;
extern struct shim_d_ops proc_d_ops;

extern struct shim_mount chroot_builtin_fs;
extern struct shim_mount pipe_builtin_fs;
extern struct shim_mount socket_builtin_fs;
extern struct shim_mount epoll_builtin_fs;
extern struct shim_mount eventfd_builtin_fs;

/* proc file system */
struct proc_nm_ops {
    int (*match_name)(const char* name);
    int (*list_name)(const char* name, struct shim_dirent** buf, int count);
};

struct proc_fs_ops {
    int (*open)(struct shim_handle* hdl, const char* name, int flags);
    int (*mode)(const char* name, mode_t* mode);
    int (*stat)(const char* name, struct stat* buf);
    int (*follow_link)(const char* name, struct shim_qstr* link);
};

struct proc_dir;

struct proc_ent {
    const char* name; /* A proc_callback should at least have a name or nm_ops. Otherwise, it is a
                       * NULL-end. */
    const struct proc_nm_ops* nm_ops;
    const struct proc_fs_ops* fs_ops;
    const struct proc_dir* dir;
};

struct proc_dir {
    int size;
    const struct proc_ent ent[];
};

/* string-type file system */
int str_add_dir(const char* path, mode_t mode, struct shim_dentry** dent);
int str_add_file(const char* path, mode_t mode, struct shim_dentry** dent);
int str_open(struct shim_handle* hdl, struct shim_dentry* dent, int flags);
int str_dput(struct shim_dentry* dent);
int str_close(struct shim_handle* hdl);
ssize_t str_read(struct shim_handle* hdl, void* buf, size_t count);
ssize_t str_write(struct shim_handle* hdl, const void* buf, size_t count);
off_t str_seek(struct shim_handle* hdl, off_t offset, int whence);
int str_flush(struct shim_handle* hdl);

#endif /* _SHIM_FS_H_ */