/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2021, sin-ack <sin-ack@protonmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Function.h>
#include <AK/HashTable.h>
#include <AK/InlineLinkedList.h>
#include <AK/RefCounted.h>
#include <AK/String.h>
#include <AK/WeakPtr.h>
#include <Kernel/FileSystem/FIFO.h>
#include <Kernel/FileSystem/FileSystem.h>
#include <Kernel/FileSystem/InodeIdentifier.h>
#include <Kernel/FileSystem/InodeMetadata.h>
#include <Kernel/Forward.h>
#include <Kernel/KResult.h>
#include <Kernel/Lock.h>

namespace Kernel {

class Inode : public RefCounted<Inode>
    , public Weakable<Inode>
    , public InlineLinkedListNode<Inode> {
    friend class VFS;
    friend class FS;

public:
    virtual ~Inode();

    virtual void one_ref_left() { }

    FS& fs() { return m_fs; }
    const FS& fs() const { return m_fs; }
    unsigned fsid() const { return m_fs.fsid(); }
    InodeIndex index() const { return m_index; }

    size_t size() const { return metadata().size; }
    bool is_symlink() const { return metadata().is_symlink(); }
    bool is_directory() const { return metadata().is_directory(); }
    bool is_character_device() const { return metadata().is_character_device(); }
    mode_t mode() const { return metadata().mode; }

    InodeIdentifier identifier() const { return { fsid(), index() }; }
    virtual InodeMetadata metadata() const = 0;

    KResultOr<NonnullOwnPtr<KBuffer>> read_entire(FileDescription* = nullptr) const;

    virtual KResult attach(FileDescription&) { return KSuccess; }
    virtual void detach(FileDescription&) { }
    virtual void did_seek(FileDescription&, off_t) { }
    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const = 0;
    virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const = 0;
    virtual RefPtr<Inode> lookup(StringView name) = 0;
    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) = 0;
    virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) = 0;
    virtual KResult add_child(Inode&, const StringView& name, mode_t) = 0;
    virtual KResult remove_child(const StringView& name) = 0;
    virtual KResultOr<size_t> directory_entry_count() const = 0;
    virtual KResult chmod(mode_t) = 0;
    virtual KResult chown(uid_t, gid_t) = 0;
    virtual KResult truncate(u64) { return KSuccess; }
    virtual KResultOr<NonnullRefPtr<Custody>> resolve_as_link(Custody& base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level) const;

    virtual KResultOr<int> get_block_address(int) { return ENOTSUP; }

    LocalSocket* socket() { return m_socket.ptr(); }
    const LocalSocket* socket() const { return m_socket.ptr(); }
    bool bind_socket(LocalSocket&);
    bool unbind_socket();

    virtual FileDescription* preopen_fd() { return nullptr; };

    bool is_metadata_dirty() const { return m_metadata_dirty; }

    virtual KResult set_atime(time_t);
    virtual KResult set_ctime(time_t);
    virtual KResult set_mtime(time_t);
    virtual KResult increment_link_count();
    virtual KResult decrement_link_count();

    virtual void flush_metadata() = 0;

    void will_be_destroyed();

    void set_shared_vmobject(SharedInodeVMObject&);
    RefPtr<SharedInodeVMObject> shared_vmobject() const;
    bool is_shared_vmobject(const SharedInodeVMObject&) const;

    static InlineLinkedList<Inode>& all_with_lock();
    static void sync();

    bool has_watchers() const { return !m_watchers.is_empty(); }

    void register_watcher(Badge<InodeWatcher>, InodeWatcher&);
    void unregister_watcher(Badge<InodeWatcher>, InodeWatcher&);

    NonnullRefPtr<FIFO> fifo();

    // For InlineLinkedListNode.
    Inode* m_next { nullptr };
    Inode* m_prev { nullptr };

    static SpinLock<u32>& all_inodes_lock();

protected:
    Inode(FS& fs, InodeIndex);
    void set_metadata_dirty(bool);
    KResult prepare_to_write_data();

    void did_add_child(InodeIdentifier const& child_id, String const& name);
    void did_remove_child(InodeIdentifier const& child_id, String const& name);
    void did_modify_contents();
    void did_delete_self();

    mutable Lock m_lock { "Inode" };

private:
    FS& m_fs;
    InodeIndex m_index { 0 };
    WeakPtr<SharedInodeVMObject> m_shared_vmobject;
    RefPtr<LocalSocket> m_socket;
    HashTable<InodeWatcher*> m_watchers;
    bool m_metadata_dirty { false };
    RefPtr<FIFO> m_fifo;
};

}