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

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

#ifdef AK_OS_SERENITY
#    include <serenity.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<String> current_working_directory()
{
    auto cwd = TRY(Core::System::getcwd());
    return TRY(String::from_deprecated_string({ cwd }));
}

ErrorOr<String> absolute_path(StringView path)
{
    if (exists(path))
        return TRY(real_path(path));

    if (path.starts_with("/"sv))
        return TRY(String::from_deprecated_string(LexicalPath::canonicalized_path(path)));

    auto working_directory = TRY(current_working_directory());
    auto full_path = LexicalPath::join(working_directory, path).string();

    return TRY(String::from_deprecated_string(LexicalPath::canonicalized_path(full_path)));
}

ErrorOr<String> real_path(StringView path)
{
    if (path.is_null())
        return Error::from_errno(ENOENT);

    char buffer[PATH_MAX];
    DeprecatedString dep_path = path;
    auto* real_path = realpath(dep_path.characters(), buffer);

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

    return TRY(String::from_utf8({ real_path, strlen(real_path) }));
}

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

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

bool is_device(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_ISBLK(st.st_mode) || S_ISCHR(st.st_mode);
}

bool is_device(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_ISBLK(st.st_mode) || S_ISCHR(st.st_mode);
}

bool is_block_device(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_ISBLK(st.st_mode);
}

bool is_block_device(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_ISBLK(st.st_mode);
}

bool is_char_device(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_ISCHR(st.st_mode);
}

bool is_char_device(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_ISCHR(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);
}

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<String> 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 = TRY(String::from_deprecated_string(LexicalPath::join(parent_path, basename).string()));

    while (exists(current_name)) {
        ++duplicate_count;
        current_name = TRY(String::from_deprecated_string(LexicalPath::join(parent_path, TRY(String::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 = TRY(String::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;

    TRY(Core::System::fchmod(destination->fd(), source_stat.st_mode & ~my_umask));

    if (has_flag(preserve_mode, PreserveMode::Ownership))
        TRY(Core::System::fchown(destination->fd(), source_stat.st_uid, source_stat.st_gid));

    if (has_flag(preserve_mode, PreserveMode::Timestamps)) {
        struct timespec times[2] = {
#ifdef AK_OS_MACOS
            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 = TRY(String::formatted("{}/", source_rp));

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

    if (!destination_rp.is_empty() && destination_rp.starts_with_bytes(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 = TRY(String::from_deprecated_string(di.next_path()));
        TRY(copy_file_or_directory(
            TRY(String::formatted("{}/{}", destination_path, filename)),
            TRY(String::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] = {
#ifdef AK_OS_MACOS
            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)
{
    String final_destination_path;
    if (add_duplicate_file_marker == AddDuplicateFileMarker::Yes)
        final_destination_path = TRY(get_duplicate_file_name(destination_path));
    else
        final_destination_path = TRY(String::from_utf8(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> 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<size_t> size(StringView path)
{
    auto st = TRY(Core::System::stat(path));
    return st.st_size;
}

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;
}

ErrorOr<String> read_link(StringView link_path)
{
    return TRY(String::from_deprecated_string(TRY(Core::System::readlink(link_path))));
}

ErrorOr<void> link_file(StringView destination_path, StringView source_path)
{
    return TRY(Core::System::symlink(source_path, TRY(get_duplicate_file_name(destination_path))));
}

ErrorOr<String> resolve_executable_from_environment(StringView filename, int flags)
{
    if (filename.is_empty())
        return Error::from_errno(ENOENT);

    // Paths that aren't just a file name generally count as already resolved.
    if (filename.contains('/')) {
        TRY(Core::System::access(filename, X_OK, flags));
        return TRY(String::from_utf8(filename));
    }

    auto const* path_str = ::getenv("PATH");
    StringView path;
    if (path_str)
        path = { path_str, strlen(path_str) };
    if (path.is_empty())
        path = DEFAULT_PATH_SV;

    auto directories = path.split_view(':');

    for (auto directory : directories) {
        auto file = TRY(String::formatted("{}/{}", directory, filename));

        if (!Core::System::access(file, X_OK, flags).is_error())
            return file;
    }

    return Error::from_errno(ENOENT);
}

bool looks_like_shared_library(StringView path)
{
    return path.ends_with(".so"sv) || path.contains(".so."sv);
}

}