/**
 * @file FileSystem.cpp
 * @author apio (cloudapio.eu)
 * @brief APIs to read and modify the general file system.
 *
 * @copyright Copyright (c) 2023, the Luna authors.
 *
 */

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <luna/Buffer.h>
#include <luna/PathParser.h>
#include <luna/String.h>
#include <os/Directory.h>
#include <os/FileSystem.h>
#include <pwd.h>
#include <stdlib.h>
#include <unistd.h>

namespace os::FileSystem
{
    bool exists(const Path& path, bool follow_symlinks)
    {
        struct stat st;

        if (stat(path, st, follow_symlinks).has_error()) return false;

        return true;
    }

    bool is_directory(const Path& path, bool follow_symlinks)
    {
        struct stat st;

        if (stat(path, st, follow_symlinks).has_error()) return false;

        return S_ISDIR(st.st_mode);
    }

    Result<void> stat(const Path& path, struct stat& st, bool follow_symlinks)
    {
        int rc = fstatat(path.dirfd(), path.name().chars(), &st,
                         (int)(path.is_empty_path() | (follow_symlinks ? 0 : AT_SYMLINK_NOFOLLOW)));

        if (rc < 0) return err(errno);
        return {};
    }

    Result<void> create_directory(StringView path, mode_t mode)
    {
        int rc = mkdir(path.chars(), mode);
        if (rc < 0) return err(errno);
        return {};
    }

    Result<void> remove(const Path& path)
    {
        // FIXME: This will not work on many operating systems that require rmdir() for directories.
        int rc = unlinkat(path.dirfd(), path.name().chars(), 0);
        if (rc < 0) return err(errno);
        return {};
    }

    Result<String> readlink(const Path& path)
    {
        struct stat st;
        TRY(stat(path, st, false));
        if (!S_ISLNK(st.st_mode)) return String {};

        Buffer buf = TRY(Buffer::create_sized(st.st_size + 1));
        memset(buf.data(), 0, buf.size());

        ssize_t nread = readlinkat(path.dirfd(), path.name().chars(), (char*)buf.data(), st.st_size);
        if (nread < 0) return err(errno);

        return String { (char*)buf.release_data(), (usize)nread };
    }

    Result<String> working_directory()
    {
        char* ptr = getcwd(NULL, 0);
        if (!ptr) return err(errno);
        return String { ptr };
    }

    Result<String> home_directory()
    {
        char* home = getenv("HOME");
        if (home) return String::from_cstring(home);

        struct passwd* pw = getpwuid(getuid());
        if (!pw) return err(ENOENT);

        return String::from_cstring(pw->pw_dir);
    }

    Result<void> change_directory(StringView path)
    {
        int rc = chdir(path.chars());
        if (rc < 0) return err(errno);
        return {};
    }
}