#include <luna/String.h>
#include <os/FileSystem.h>

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <unistd.h>

namespace os::FileSystem
{
    bool exists(StringView path)
    {
        struct stat st;

        if (stat(path.chars(), &st) < 0) return false;

        return true;
    }

    bool is_directory(StringView path)
    {
        struct stat st;

        if (stat(path.chars(), &st) < 0) return false;

        return S_ISDIR(st.st_mode);
    }

    Result<void> create_directory(StringView path, mode_t mode)
    {
        long rc = syscall(SYS_mkdir, path.chars(), mode);

        return Result<void>::from_syscall(rc);
    }

    Result<void> remove(StringView path)
    {
        return removeat(AT_FDCWD, path);
    }

    Result<void> removeat(int dirfd, StringView path)
    {
        long rc = syscall(SYS_unlinkat, dirfd, path.chars(), 0);

        return Result<void>::from_syscall(rc);
    }

    Result<void> remove_tree(StringView path)
    {
        return remove_tree_at(AT_FDCWD, path);
    }

    Result<void> remove_tree_at(int dirfd, StringView path)
    {
        auto rc = removeat(dirfd, path);
        if (!rc.has_error()) return {};
        if (rc.error() != ENOTEMPTY) return rc.release_error();

        DIR* dp = opendir(path.chars());
        if (!dp) return err(errno);

        Vector<String> entries;

        // FIXME: This is done because the kernel doesn't appreciate us deleting entries while iterating over
        // directories. This means that we have to iterate first, then delete.

        struct dirent* ent;
        while ((ent = readdir(dp)))
        {
            if ("."_sv == ent->d_name || ".."_sv == ent->d_name) continue;
            auto entry = TRY(String::from_cstring(ent->d_name));
            TRY(entries.try_append(move(entry)));
        }

        for (const auto& entry : entries) { TRY(remove_tree_at(dp->_fd, entry.view())); }

        closedir(dp);

        return removeat(dirfd, path);
    }

    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)
    {
        long rc = syscall(SYS_chdir, path.chars());

        return Result<void>::from_syscall(rc);
    }
}