// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <fbl/auto_call.h>
#include <fcntl.h>
#include <fdio/remoteio.h>
#include <fdio/watcher.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#ifdef __Fuchsia__
#include <fbl/auto_lock.h>
#include <fbl/ref_ptr.h>
#include <fs/connection.h>
#include <fs/remote.h>
#include <threads.h>
#include <zircon/assert.h>
#include <zircon/process.h>
#include <zircon/syscalls.h>
#include <zx/event.h>
#endif

#include <fs/trace.h>
#include <fs/vfs.h>
#include <fs/vnode.h>

uint32_t __trace_bits;

namespace fs {
namespace {

// Trim a name before sending it to internal filesystem functions.
// Trailing '/' characters imply that the name must refer to a directory.
zx_status_t vfs_name_trim(fbl::StringPiece name, fbl::StringPiece* name_out,
                          bool* dir_out) {
    size_t len = name.length();
    bool is_dir = false;
    while ((len > 0) && name[len - 1] == '/') {
        len--;
        is_dir = true;
    }

    // 'name' should not contain paths consisting of exclusively '/' characters.
    if (len == 0) {
        return ZX_ERR_INVALID_ARGS;
    } else if (len > NAME_MAX) {
        return ZX_ERR_BAD_PATH;
    }

    name_out->set(name.data(), len);
    *dir_out = is_dir;
    return ZX_OK;
}

zx_status_t vfs_lookup(fbl::RefPtr<Vnode> vn, fbl::RefPtr<Vnode>* out,
                       fbl::StringPiece name) {
    if (name == "..") {
        return ZX_ERR_INVALID_ARGS;
    } else if (name == ".") {
        *out = fbl::move(vn);
        return ZX_OK;
    }
    return vn->Lookup(out, name);
}

// Validate open flags as much as they can be validated
// independently of the target node.
zx_status_t vfs_prevalidate_flags(uint32_t flags) {
    switch (flags & O_ACCMODE) {
    case O_PATH:
        ZX_DEBUG_ASSERT((flags & (O_TRUNC | O_CREAT | O_RDWR)) == 0);
        return ZX_OK;
    case O_RDONLY:
        if (flags & O_TRUNC) {
            return ZX_ERR_INVALID_ARGS;
        }
    case O_WRONLY:
    case O_RDWR:
        return ZX_OK;
    default:
        return ZX_ERR_INVALID_ARGS;
    }
}

} // namespace

#ifdef __Fuchsia__

bool RemoteContainer::IsRemote() const {
    return remote_.is_valid();
}

zx::channel RemoteContainer::DetachRemote() {
    return fbl::move(remote_);
}

zx_handle_t RemoteContainer::GetRemote() const {
    return remote_.get();
}

void RemoteContainer::SetRemote(zx::channel remote) {
    ZX_DEBUG_ASSERT(!remote_.is_valid());
    remote_ = fbl::move(remote);
}

#endif

Vfs::Vfs() = default;
Vfs::~Vfs() = default;

#ifdef __Fuchsia__
Vfs::Vfs(async_t* async)
    : async_(async) {}
#endif

zx_status_t Vfs::Open(fbl::RefPtr<Vnode> vndir, fbl::RefPtr<Vnode>* out,
                      fbl::StringPiece path, fbl::StringPiece* pathout, uint32_t flags,
                      uint32_t mode) {
#ifdef __Fuchsia__
    fbl::AutoLock lock(&vfs_lock_);
#endif
    return OpenLocked(fbl::move(vndir), out, path, pathout, flags, mode);
}

zx_status_t Vfs::OpenLocked(fbl::RefPtr<Vnode> vndir, fbl::RefPtr<Vnode>* out,
                            fbl::StringPiece path, fbl::StringPiece* pathout,
                            uint32_t flags, uint32_t mode) {
    FS_TRACE(VFS, "VfsOpen: path='%s' flags=%d\n", path.begin(), flags);
    zx_status_t r;
    if ((r = vfs_prevalidate_flags(flags)) != ZX_OK) {
        return r;
    }
    if ((r = Vfs::Walk(vndir, &vndir, path, &path)) < 0) {
        return r;
    }
#ifdef __Fuchsia__
    if (vndir->IsRemote()) {
        // remote filesystem, return handle and path through to caller
        *out = fbl::move(vndir);
        *pathout = path;
        return ZX_OK;
    }
#endif

    fbl::RefPtr<Vnode> vn;

    bool must_be_dir = false;
    if ((r = vfs_name_trim(path, &path, &must_be_dir)) != ZX_OK) {
        return r;
    } else if (path == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    if (flags & O_CREAT) {
        if (must_be_dir && !S_ISDIR(mode)) {
            return ZX_ERR_INVALID_ARGS;
        } else if (path == ".") {
            return ZX_ERR_INVALID_ARGS;
        } else if (ReadonlyLocked()) {
            return ZX_ERR_ACCESS_DENIED;
        }
        if ((r = vndir->Create(&vn, path, mode)) < 0) {
            if ((r == ZX_ERR_ALREADY_EXISTS) && (!(flags & O_EXCL))) {
                goto try_open;
            }
            if (r == ZX_ERR_NOT_SUPPORTED) {
                // filesystem may not support create (like devfs)
                // in which case we should still try to open() the file
                goto try_open;
            }
            return r;
        }
        vndir->Notify(path, VFS_WATCH_EVT_ADDED);
    } else {
    try_open:
        r = vfs_lookup(fbl::move(vndir), &vn, path);
        if (r < 0) {
            return r;
        }
#ifdef __Fuchsia__
        if (!(flags & O_NOREMOTE) && vn->IsRemote()) {
            // Opening a mount point: Traverse across remote.
            *pathout = ".";

            if ((r = vn->GetRemote()) > 0) {
                *out = fbl::move(vn);
                return ZX_OK;
            }
        }

        flags |= (must_be_dir ? O_DIRECTORY : 0);
#endif
        if (ReadonlyLocked() && IsWritable(flags)) {
            return ZX_ERR_ACCESS_DENIED;
        }
        if ((r = vn->ValidateFlags(flags)) != ZX_OK) {
            return r;
        }
        // O_PATH requests that we don't actually open the underlying
        // Vnode.
        if (!IsPathOnly(flags)) {
            if ((r = OpenVnode(flags, &vn)) != ZX_OK) {
                return r;
            }
            if ((flags & O_TRUNC) && ((r = vn->Truncate(0)) < 0)) {
                vn->Close();
                return r;
            }
        }
    }
    FS_TRACE(VFS, "VfsOpen: vn=%p\n", vn.get());
    *pathout = "";
    *out = vn;
    return ZX_OK;
}

zx_status_t Vfs::Unlink(fbl::RefPtr<Vnode> vndir, fbl::StringPiece path) {
    bool must_be_dir;
    zx_status_t r;
    if ((r = vfs_name_trim(path, &path, &must_be_dir)) != ZX_OK) {
        return r;
    } else if (path == ".") {
        return ZX_ERR_UNAVAILABLE;
    } else if (path == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    {
#ifdef __Fuchsia__
        fbl::AutoLock lock(&vfs_lock_);
#endif
        if (ReadonlyLocked()) {
            r = ZX_ERR_ACCESS_DENIED;
        } else {
            r = vndir->Unlink(path, must_be_dir);
        }
    }
    if (r != ZX_OK) {
        return r;
    }
    vndir->Notify(path, VFS_WATCH_EVT_REMOVED);
    return ZX_OK;
}

#ifdef __Fuchsia__

#define TOKEN_RIGHTS (ZX_RIGHT_DUPLICATE | ZX_RIGHT_TRANSFER)

void Vfs::TokenDiscard(zx::event ios_token) {
    fbl::AutoLock lock(&vfs_lock_);
    if (ios_token) {
        // The token is cleared here to prevent the following race condition:
        // 1) Open
        // 2) GetToken
        // 3) Close + Release Vnode
        // 4) Use token handle to access defunct vnode (or a different vnode,
        //    if the memory for it is reallocated).
        //
        // By cleared the token cookie, any remaining handles to the event will
        // be ignored by the filesystem server.
        ios_token.set_cookie(zx_process_self(), 0);
    }
}

zx_status_t Vfs::VnodeToToken(fbl::RefPtr<Vnode> vn, zx::event* ios_token,
                              zx::event* out) {
    uint64_t vnode_cookie = reinterpret_cast<uint64_t>(vn.get());
    zx_status_t r;

    fbl::AutoLock lock(&vfs_lock_);
    if (ios_token->is_valid()) {
        // Token has already been set for this iostate
        if ((r = ios_token->duplicate(TOKEN_RIGHTS, out) != ZX_OK)) {
            return r;
        }
        return ZX_OK;
    }

    zx::event new_token;
    zx::event new_ios_token;
    if ((r = zx::event::create(0, &new_ios_token)) != ZX_OK) {
        return r;
    } else if ((r = new_ios_token.duplicate(TOKEN_RIGHTS, &new_token) != ZX_OK)) {
        return r;
    } else if ((r = new_ios_token.set_cookie(zx_process_self(), vnode_cookie)) != ZX_OK) {
        return r;
    }
    *ios_token = fbl::move(new_ios_token);
    *out = fbl::move(new_token);
    return ZX_OK;
}

zx_status_t Vfs::TokenToVnode(zx::event token, fbl::RefPtr<Vnode>* out) {
    uint64_t vcookie;
    zx_status_t r;
    if ((r = token.get_cookie(zx_process_self(), &vcookie)) < 0) {
        // TODO(smklein): Return a more specific error code for "token not from this server"
        return ZX_ERR_INVALID_ARGS;
    }

    if (vcookie == 0) {
        // Client closed the channel associated with the token
        return ZX_ERR_INVALID_ARGS;
    }

    *out = fbl::RefPtr<fs::Vnode>(reinterpret_cast<fs::Vnode*>(vcookie));
    return ZX_OK;
}

zx_status_t Vfs::Rename(zx::event token, fbl::RefPtr<Vnode> oldparent,
                        fbl::StringPiece oldStr, fbl::StringPiece newStr) {
    // Local filesystem
    bool old_must_be_dir;
    bool new_must_be_dir;
    zx_status_t r;
    if ((r = vfs_name_trim(oldStr, &oldStr, &old_must_be_dir)) != ZX_OK) {
        return r;
    } else if (oldStr == ".") {
        return ZX_ERR_UNAVAILABLE;
    } else if (oldStr == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    if ((r = vfs_name_trim(newStr, &newStr, &new_must_be_dir)) != ZX_OK) {
        return r;
    } else if (newStr == "." || newStr == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    fbl::RefPtr<fs::Vnode> newparent;
    {
        fbl::AutoLock lock(&vfs_lock_);
        if (ReadonlyLocked()) {
            return ZX_ERR_ACCESS_DENIED;
        }
        if ((r = TokenToVnode(fbl::move(token), &newparent)) != ZX_OK) {
            return r;
        }

        r = oldparent->Rename(newparent, oldStr, newStr, old_must_be_dir,
                              new_must_be_dir);
    }
    if (r != ZX_OK) {
        return r;
    }
    oldparent->Notify(oldStr, VFS_WATCH_EVT_REMOVED);
    newparent->Notify(newStr, VFS_WATCH_EVT_ADDED);
    return ZX_OK;
}

zx_status_t Vfs::Readdir(Vnode* vn, vdircookie_t* cookie,
                         void* dirents, size_t len, size_t* out_actual) {
    fbl::AutoLock lock(&vfs_lock_);
    return vn->Readdir(cookie, dirents, len, out_actual);
}

zx_status_t Vfs::Link(zx::event token, fbl::RefPtr<Vnode> oldparent,
                      fbl::StringPiece oldStr, fbl::StringPiece newStr) {
    fbl::AutoLock lock(&vfs_lock_);
    fbl::RefPtr<fs::Vnode> newparent;
    zx_status_t r;
    if ((r = TokenToVnode(fbl::move(token), &newparent)) != ZX_OK) {
        return r;
    }
    // Local filesystem
    bool old_must_be_dir;
    bool new_must_be_dir;
    if (ReadonlyLocked()) {
        return ZX_ERR_ACCESS_DENIED;
    } else if ((r = vfs_name_trim(oldStr, &oldStr, &old_must_be_dir)) != ZX_OK) {
        return r;
    } else if (old_must_be_dir) {
        return ZX_ERR_NOT_DIR;
    } else if (oldStr == ".") {
        return ZX_ERR_UNAVAILABLE;
    } else if (oldStr == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    if ((r = vfs_name_trim(newStr, &newStr, &new_must_be_dir)) != ZX_OK) {
        return r;
    } else if (new_must_be_dir) {
        return ZX_ERR_NOT_DIR;
    } else if (newStr == "." || newStr == "..") {
        return ZX_ERR_INVALID_ARGS;
    }

    // Look up the target vnode
    fbl::RefPtr<Vnode> target;
    if ((r = oldparent->Lookup(&target, oldStr)) < 0) {
        return r;
    }
    r = newparent->Link(newStr, target);
    if (r != ZX_OK) {
        return r;
    }
    newparent->Notify(newStr, VFS_WATCH_EVT_ADDED);
    return ZX_OK;
}

zx_status_t Vfs::ServeConnection(fbl::unique_ptr<Connection> connection) {
    ZX_DEBUG_ASSERT(connection);

    zx_status_t status = connection->Serve();
    if (status == ZX_OK) {
        RegisterConnection(fbl::move(connection));
    }
    return status;
}

void Vfs::OnConnectionClosedRemotely(Connection* connection) {
    ZX_DEBUG_ASSERT(connection);

    UnregisterAndDestroyConnection(connection);
}

zx_status_t Vfs::ServeDirectory(fbl::RefPtr<fs::Vnode> vn, zx::channel channel) {
    uint32_t flags = O_DIRECTORY;
    zx_status_t r;
    if ((r = vn->ValidateFlags(flags)) != ZX_OK) {
        return r;
    } else if ((r = OpenVnode(flags, &vn)) != ZX_OK) {
        return r;
    }

    // Tell the calling process that we've mounted the directory.
    if ((r = channel.signal_peer(0, ZX_USER_SIGNAL_0)) != ZX_OK) {
        return r;
    }

    return vn->Serve(this, fbl::move(channel), O_ADMIN);
}

void Vfs::RegisterConnection(fbl::unique_ptr<Connection> connection) {
    // The connection will be destroyed by |UnregisterAndDestroyConnection()|
    connection.release();
}

void Vfs::UnregisterAndDestroyConnection(Connection* connection) {
    delete connection;
}

#endif // ifdef __Fuchsia__

zx_status_t Vfs::Ioctl(fbl::RefPtr<Vnode> vn, uint32_t op, const void* in_buf, size_t in_len,
                       void* out_buf, size_t out_len, size_t* out_actual) {
    switch (op) {
#ifdef __Fuchsia__
    case IOCTL_VFS_WATCH_DIR: {
        if (in_len != sizeof(vfs_watch_dir_t)) {
            return ZX_ERR_INVALID_ARGS;
        }
        const vfs_watch_dir_t* request = reinterpret_cast<const vfs_watch_dir_t*>(in_buf);
        *out_actual = 0;
        return vn->WatchDir(this, request);
    }
    case IOCTL_VFS_MOUNT_FS: {
        if ((in_len != sizeof(zx_handle_t)) || (out_len != 0)) {
            return ZX_ERR_INVALID_ARGS;
        }
        MountChannel h = MountChannel(*reinterpret_cast<const zx_handle_t*>(in_buf));
        *out_actual = 0;
        return Vfs::InstallRemote(vn, fbl::move(h));
    }
    case IOCTL_VFS_MOUNT_MKDIR_FS: {
        size_t namelen = in_len - sizeof(mount_mkdir_config_t);
        const mount_mkdir_config_t* config = reinterpret_cast<const mount_mkdir_config_t*>(in_buf);
        fbl::StringPiece name(config->name, namelen - 1);
        if ((in_len < sizeof(mount_mkdir_config_t)) ||
            (namelen < 1) || (namelen > PATH_MAX) || (name[namelen - 1] != 0) ||
            (out_len != 0)) {
            return ZX_ERR_INVALID_ARGS;
        }

        *out_actual = 0;
        return Vfs::MountMkdir(fbl::move(vn), fbl::move(name),
                               MountChannel(config->fs_root), config->flags);
    }
    case IOCTL_VFS_UNMOUNT_NODE: {
        if ((in_len != 0) || (out_len != sizeof(zx_handle_t))) {
            return ZX_ERR_INVALID_ARGS;
        }
        zx_handle_t* h = (zx_handle_t*)out_buf;
        zx::channel c;
        *out_actual = 0;
        zx_status_t s = Vfs::UninstallRemote(vn, &c);
        *h = c.release();
        return s;
    }
    case IOCTL_VFS_UNMOUNT_FS: {
        Vfs::UninstallAll(ZX_TIME_INFINITE);
        *out_actual = 0;
        vn->Ioctl(op, in_buf, in_len, out_buf, out_len, out_actual);
        return ZX_OK;
    }
#endif
    default:
        return vn->Ioctl(op, in_buf, in_len, out_buf, out_len, out_actual);
    }
}

void Vfs::SetReadonly(bool value) {
#ifdef __Fuchsia__
    fbl::AutoLock lock(&vfs_lock_);
#endif
    readonly_ = value;
}

zx_status_t Vfs::Walk(fbl::RefPtr<Vnode> vn, fbl::RefPtr<Vnode>* out,
                      fbl::StringPiece pathStr, fbl::StringPiece* pathout) {
    zx_status_t r;
    const char* path = pathStr.data();
    size_t new_len = pathStr.length();

    for (;;) {
        while (path[0] == '/') {
            // discard extra leading /s
            path++;
        }
        if (path[0] == 0) {
            // convert empty initial path of final path segment to "."
            path = ".";
            new_len = 1;
        } else {
            new_len = pathStr.length() - (path - pathStr.data());
        }
#ifdef __Fuchsia__
        if (vn->IsRemote()) {
            // remote filesystem mount, caller must resolve
            *out = fbl::move(vn);
            pathout->set(path, new_len);
            return ZX_OK;
        }
#endif

        const char* nextpath = strchr(path, '/');
        bool additional_segment = false;
        if (nextpath != nullptr) {
            const char* end = nextpath;
            while (*end != '\0') {
                if (*end != '/') {
                    additional_segment = true;
                    break;
                }
                end++;
            }
        }
        if (additional_segment) {
            // path has at least one additional segment
            // traverse to the next segment
            size_t len = nextpath - path;
            nextpath++;
            if ((r = vfs_lookup(fbl::move(vn), &vn, fbl::StringPiece(path, len))) < 0) {
                return r;
            }
            path = nextpath;
        } else {
            // final path segment, we're done here
            *out = vn;

            if (pathStr.length() > 0) {
                new_len = pathStr.length() - (path - pathStr.data());
            }

            pathout->set(path, new_len);
            return ZX_OK;
        }
    }
}

} // namespace fs