/*
 * Copyright (c) 2018-2021, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2023, Cameron Youell <cameronyouell@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/LexicalPath.h>
#include <AK/ScopeGuard.h>
#include <LibCore/DirIterator.h>
#include <LibCore/System.h>
#include <LibFileSystem/FileSystem.h>

#if !defined(AK_OS_IOS) && defined(AK_OS_BSD_GENERIC)
#    include <sys/disk.h>
#elif defined(AK_OS_LINUX)
#    include <linux/fs.h>
#endif

// On Linux distros that use glibc `basename` is defined as a macro that expands to `__xpg_basename`, so we undefine it
#if defined(AK_OS_LINUX) && defined(basename)
#    undef basename
#endif

namespace FileSystem {

ErrorOr<ByteString> current_working_directory()
{
    return Core::System::getcwd();
}

ErrorOr<ByteString> absolute_path(StringView path)
{
#ifndef AK_OS_WINDOWS
    if (exists(path))
        return real_path(path);
#endif

    if (LexicalPath::is_absolute_path(path))
        return LexicalPath::canonicalized_path(path);

    auto working_directory = TRY(current_working_directory());
    return LexicalPath::absolute_path(working_directory, path);
}

#ifndef AK_OS_WINDOWS
ErrorOr<ByteString> real_path(StringView path)
{
    if (path.is_null())
        return Error::from_errno(ENOENT);

    ByteString dep_path = path;
    char* real_path = realpath(dep_path.characters(), nullptr);
    ScopeGuard free_path = [real_path]() { free(real_path); };

    if (!real_path)
        return Error::from_syscall("realpath"sv, -errno);

    return ByteString { real_path, strlen(real_path) };
}
#else
// NOTE: real_path on Windows does not resolve symlinks
ErrorOr<ByteString> real_path(StringView path)
{
    return absolute_path(path);
}
#endif

bool exists(StringView path)
{
    return !Core::System::stat(path).is_error();
}

bool exists(int fd)
{
    return !Core::System::fstat(fd).is_error();
}

bool is_regular_file(StringView path)
{
    auto st_or_error = Core::System::stat(path);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISREG(st.st_mode);
}

bool is_regular_file(int fd)
{
    auto st_or_error = Core::System::fstat(fd);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISREG(st.st_mode);
}

bool is_directory(StringView path)
{
    auto st_or_error = Core::System::stat(path);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISDIR(st.st_mode);
}

bool is_directory(int fd)
{
    auto st_or_error = Core::System::fstat(fd);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISDIR(st.st_mode);
}

#ifdef AK_OS_WINDOWS
bool is_link(StringView path)
{
    ByteString string_path = path;
    auto attr = GetFileAttributes(string_path.characters());
    if (attr == INVALID_FILE_ATTRIBUTES)
        return false;
    return attr & FILE_ATTRIBUTE_REPARSE_POINT;
}
#else
bool is_link(StringView path)
{
    auto st_or_error = Core::System::lstat(path);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISLNK(st.st_mode);
}

bool is_link(int fd)
{
    auto st_or_error = Core::System::fstat(fd);
    if (st_or_error.is_error())
        return false;
    auto st = st_or_error.release_value();
    return S_ISLNK(st.st_mode);
}

static ErrorOr<ByteString> get_duplicate_file_name(StringView path)
{
    int duplicate_count = 0;
    LexicalPath lexical_path(path);
    auto parent_path = LexicalPath::canonicalized_path(lexical_path.dirname());
    auto basename = lexical_path.basename();
    auto current_name = LexicalPath::join(parent_path, basename).string();

    while (exists(current_name)) {
        ++duplicate_count;
        current_name = LexicalPath::join(parent_path, ByteString::formatted("{} ({})", basename, duplicate_count)).string();
    }

    return current_name;
}

ErrorOr<void> copy_file(StringView destination_path, StringView source_path, struct stat const& source_stat, Core::File& source, PreserveMode preserve_mode)
{
    auto destination_or_error = Core::File::open(destination_path, Core::File::OpenMode::Write, 0666);
    if (destination_or_error.is_error()) {
        if (destination_or_error.error().code() != EISDIR)
            return destination_or_error.release_error();

        auto destination_dir_path = ByteString::formatted("{}/{}", destination_path, LexicalPath::basename(source_path));
        destination_or_error = TRY(Core::File::open(destination_dir_path, Core::File::OpenMode::Write, 0666));
    }
    auto destination = destination_or_error.release_value();

    if (source_stat.st_size > 0)
        TRY(destination->truncate(source_stat.st_size));

    while (true) {
        auto bytes_read = TRY(source.read_until_eof());

        if (bytes_read.is_empty())
            break;

        TRY(destination->write_until_depleted(bytes_read));
    }

    auto my_umask = umask(0);
    umask(my_umask);
    // NOTE: We don't copy the set-uid and set-gid bits unless requested.
    if (!has_flag(preserve_mode, PreserveMode::Permissions))
        my_umask |= 06000;

    if (auto result = Core::System::fchmod(destination->fd(), source_stat.st_mode & ~my_umask); result.is_error())
        if (result.error().is_errno() && result.error().code() != ENOTSUP)
            return result.release_error();

    if (has_flag(preserve_mode, PreserveMode::Ownership))
        if (auto result = Core::System::fchown(destination->fd(), source_stat.st_uid, source_stat.st_gid); result.is_error())
            if (result.error().is_errno() && result.error().code() != ENOTSUP)
                return result.release_error();

    if (has_flag(preserve_mode, PreserveMode::Timestamps)) {
        struct timespec times[2] = {
#    if defined(AK_OS_MACOS) || defined(AK_OS_IOS)
            source_stat.st_atimespec,
            source_stat.st_mtimespec,
#    else
            source_stat.st_atim,
            source_stat.st_mtim,
#    endif
        };
        TRY(Core::System::utimensat(AT_FDCWD, destination_path, times, 0));
    }
    return {};
}

ErrorOr<void> copy_directory(StringView destination_path, StringView source_path, struct stat const& source_stat, LinkMode link, PreserveMode preserve_mode)
{
    TRY(Core::System::mkdir(destination_path, 0755));

    auto source_rp = TRY(real_path(source_path));
    source_rp = ByteString::formatted("{}/", source_rp);

    auto destination_rp = TRY(real_path(destination_path));
    destination_rp = ByteString::formatted("{}/", destination_rp);

    if (!destination_rp.is_empty() && destination_rp.starts_with(source_rp))
        return Error::from_errno(EINVAL);

    Core::DirIterator di(source_path, Core::DirIterator::SkipParentAndBaseDir);
    if (di.has_error())
        return di.error();

    while (di.has_next()) {
        auto filename = di.next_path();
        TRY(copy_file_or_directory(
            ByteString::formatted("{}/{}", destination_path, filename),
            ByteString::formatted("{}/{}", source_path, filename),
            RecursionMode::Allowed, link, AddDuplicateFileMarker::Yes, preserve_mode));
    }

    auto my_umask = umask(0);
    umask(my_umask);

    TRY(Core::System::chmod(destination_path, source_stat.st_mode & ~my_umask));

    if (has_flag(preserve_mode, PreserveMode::Ownership))
        TRY(Core::System::chown(destination_path, source_stat.st_uid, source_stat.st_gid));

    if (has_flag(preserve_mode, PreserveMode::Timestamps)) {
        struct timespec times[2] = {
#    if defined(AK_OS_MACOS) || defined(AK_OS_IOS)
            source_stat.st_atimespec,
            source_stat.st_mtimespec,
#    else
            source_stat.st_atim,
            source_stat.st_mtim,
#    endif
        };
        TRY(Core::System::utimensat(AT_FDCWD, destination_path, times, 0));
    }

    return {};
}

ErrorOr<void> copy_file_or_directory(StringView destination_path, StringView source_path, RecursionMode recursion_mode, LinkMode link_mode, AddDuplicateFileMarker add_duplicate_file_marker, PreserveMode preserve_mode)
{
    ByteString final_destination_path;
    if (add_duplicate_file_marker == AddDuplicateFileMarker::Yes)
        final_destination_path = TRY(get_duplicate_file_name(destination_path));
    else
        final_destination_path = destination_path;

    auto source = TRY(Core::File::open(source_path, Core::File::OpenMode::Read));

    auto source_stat = TRY(Core::System::fstat(source->fd()));

    if (is_directory(source_path)) {
        if (recursion_mode == RecursionMode::Disallowed) {
            return Error::from_errno(EISDIR);
        }

        return copy_directory(final_destination_path, source_path, source_stat);
    }

    if (link_mode == LinkMode::Allowed)
        return TRY(Core::System::link(source_path, final_destination_path));

    return copy_file(final_destination_path, source_path, source_stat, *source, preserve_mode);
}

ErrorOr<void> move_file(StringView destination_path, StringView source_path, PreserveMode preserve_mode)
{
    auto maybe_error = Core::System::rename(source_path, destination_path);
    if (!maybe_error.is_error())
        return {};

    if (!maybe_error.error().is_errno() || maybe_error.error().code() != EXDEV)
        return maybe_error;

    auto source = TRY(Core::File::open(source_path, Core::File::OpenMode::Read));

    auto source_stat = TRY(Core::System::fstat(source->fd()));

    TRY(copy_file(destination_path, source_path, source_stat, *source, preserve_mode));

    return Core::System::unlink(source_path);
}

bool can_delete_or_move(StringView path)
{
    VERIFY(!path.is_empty());
    auto directory = LexicalPath::dirname(path);
    auto directory_has_write_access = !Core::System::access(directory, W_OK).is_error();
    if (!directory_has_write_access)
        return false;

    auto stat_or_empty = [](StringView path) {
        auto stat_or_error = Core::System::stat(path);
        if (stat_or_error.is_error()) {
            struct stat stat { };
            return stat;
        }
        return stat_or_error.release_value();
    };

    auto directory_stat = stat_or_empty(directory);
    bool is_directory_sticky = (directory_stat.st_mode & S_ISVTX) != 0;
    if (!is_directory_sticky)
        return true;

    // Directory is sticky, only the file owner, directory owner, and root can modify (rename, remove) it.
    auto user_id = geteuid();
    return user_id == 0 || directory_stat.st_uid == user_id || stat_or_empty(path).st_uid == user_id;
}
#endif // !AK_OS_WINDOWS

ErrorOr<void> remove(StringView path, RecursionMode mode)
{
    if (is_directory(path) && mode == RecursionMode::Allowed) {
        auto di = Core::DirIterator(path, Core::DirIterator::SkipParentAndBaseDir);
        if (di.has_error())
            return di.error();

        while (di.has_next())
            TRY(remove(di.next_full_path(), RecursionMode::Allowed));

        TRY(Core::System::rmdir(path));
    } else {
        TRY(Core::System::unlink(path));
    }

    return {};
}

ErrorOr<off_t> size_from_stat(StringView path)
{
    auto st = TRY(Core::System::stat(path));
    return st.st_size;
}

ErrorOr<off_t> size_from_fstat(int fd)
{
    auto st = TRY(Core::System::fstat(fd));
    return st.st_size;
}

}