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

#include <AK/Assertions.h>
#include <AK/HashMap.h>
#include <AK/NumberFormat.h>
#include <AK/QuickSort.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/URL.h>
#include <AK/Utf8View.h>
#include <AK/Vector.h>
#include <LibCore/ArgsParser.h>
#include <LibCore/DateTime.h>
#include <LibCore/DirIterator.h>
#include <LibCore/File.h>
#include <LibCore/System.h>
#include <LibMain/Main.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <inttypes.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

struct FileMetadata {
    String name;
    String path;
    struct stat stat {
    };
};

static int do_file_system_object_long(char const* path);
static int do_file_system_object_short(char const* path);

static bool print_names(char const* path, size_t longest_name, Vector<FileMetadata> const& files);

static bool filemetadata_comparator(FileMetadata& a, FileMetadata& b);

static bool flag_classify = false;
static bool flag_colorize = false;
static bool flag_long = false;
static bool flag_show_dotfiles = false;
static bool flag_show_almost_all_dotfiles = false;
static bool flag_ignore_backups = false;
static bool flag_list_directories_only = false;
static bool flag_show_inode = false;
static bool flag_print_numeric = false;
static bool flag_hide_group = false;
static bool flag_human_readable = false;
static bool flag_sort_by_timestamp = false;
static bool flag_reverse_sort = false;
static bool flag_disable_hyperlinks = false;
static bool flag_recursive = false;
static bool flag_force_newline = false;

static size_t terminal_rows = 0;
static size_t terminal_columns = 0;
static bool output_is_terminal = false;

static HashMap<uid_t, String> users;
static HashMap<gid_t, String> groups;

static bool is_a_tty = false;

ErrorOr<int> serenity_main(Main::Arguments arguments)
{
    TRY(Core::System::pledge("stdio rpath tty"));

    struct winsize ws;
    int rc = ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);
    if (rc == 0) {
        terminal_rows = ws.ws_row;
        terminal_columns = ws.ws_col;
        output_is_terminal = true;
    }

    is_a_tty = isatty(STDOUT_FILENO);
    if (!is_a_tty) {
        flag_disable_hyperlinks = true;
    } else {
        flag_colorize = true;
    }

    TRY(Core::System::pledge("stdio rpath"));

    Vector<StringView> paths;

    Core::ArgsParser args_parser;
    args_parser.set_general_help("List files in a directory.");
    args_parser.add_option(flag_show_dotfiles, "Show dotfiles", "all", 'a');
    args_parser.add_option(flag_show_almost_all_dotfiles, "Do not list implied . and .. directories", nullptr, 'A');
    args_parser.add_option(flag_ignore_backups, "Do not list implied entries ending with ~", "ignore-backups", 'B');
    args_parser.add_option(flag_list_directories_only, "List directories themselves, not their contents", "directory", 'd');
    args_parser.add_option(flag_long, "Display long info", "long", 'l');
    args_parser.add_option(flag_sort_by_timestamp, "Sort files by timestamp", nullptr, 't');
    args_parser.add_option(flag_reverse_sort, "Reverse sort order", "reverse", 'r');
    args_parser.add_option(flag_classify, "Append a file type indicator to entries", "classify", 'F');
    args_parser.add_option(flag_colorize, "Use pretty colors", nullptr, 'G');
    args_parser.add_option(flag_show_inode, "Show inode ids", "inode", 'i');
    args_parser.add_option(flag_print_numeric, "In long format, display numeric UID/GID", "numeric-uid-gid", 'n');
    args_parser.add_option(flag_hide_group, "In long format, do not show group information", nullptr, 'o');
    args_parser.add_option(flag_human_readable, "Print human-readable sizes", "human-readable", 'h');
    args_parser.add_option(flag_disable_hyperlinks, "Disable hyperlinks", "no-hyperlinks", 'K');
    args_parser.add_option(flag_recursive, "List subdirectories recursively", "recursive", 'R');
    args_parser.add_option(flag_force_newline, "List one file per line", nullptr, '1');
    args_parser.add_positional_argument(paths, "Directory to list", "path", Core::ArgsParser::Required::No);
    args_parser.parse(arguments);

    if (flag_show_almost_all_dotfiles)
        flag_show_dotfiles = true;

    if (flag_long) {
        setpwent();
        for (auto* pwd = getpwent(); pwd; pwd = getpwent())
            users.set(pwd->pw_uid, pwd->pw_name);
        endpwent();
        setgrent();
        for (auto* grp = getgrent(); grp; grp = getgrent())
            groups.set(grp->gr_gid, grp->gr_name);
        endgrent();
    }

    auto do_file_system_object = [&](char const* path) {
        if (flag_long)
            return do_file_system_object_long(path);
        return do_file_system_object_short(path);
    };

    if (paths.is_empty())
        paths.append("."sv);

    Vector<FileMetadata> files;
    for (auto& path : paths) {
        FileMetadata metadata;
        metadata.name = path;

        int rc = lstat(String(path).characters(), &metadata.stat);
        if (rc < 0) {
            perror("lstat");
            continue;
        }

        files.append(metadata);
    }
    quick_sort(files, filemetadata_comparator);

    int status = 0;

    for (size_t i = 0; i < files.size(); i++) {
        auto path = files[i].name;

        if (flag_recursive && Core::File::is_directory(path)) {
            size_t subdirs = 0;
            Core::DirIterator di(path, Core::DirIterator::SkipParentAndBaseDir);

            if (di.has_error()) {
                status = 1;
                fprintf(stderr, "%s: %s\n", path.characters(), di.error_string());
            }

            while (di.has_next()) {
                String directory = di.next_full_path();
                if (Core::File::is_directory(directory) && !Core::File::is_link(directory)) {
                    ++subdirs;
                    FileMetadata new_file;
                    new_file.name = move(directory);
                    files.insert(i + subdirs, move(new_file));
                }
            }
        }

        bool show_dir_separator = files.size() > 1 && Core::File::is_directory(path) && !flag_list_directories_only;
        if (show_dir_separator) {
            printf("%s:\n", path.characters());
        }
        auto rc = do_file_system_object(path.characters());
        if (rc != 0)
            status = rc;
        if (show_dir_separator && i != files.size() - 1) {
            puts("");
        }
    }

    return status;
}

static int print_escaped(StringView name)
{
    int printed = 0;

    Utf8View utf8_name(name);
    if (utf8_name.validate()) {
        out("{}", name);
        return utf8_name.length();
    }

    for (int i = 0; name[i] != '\0'; i++) {
        if (isprint(name[i])) {
            putchar(name[i]);
            printed++;
        } else {
            printed += printf("\\%03d", name[i]);
        }
    }

    return printed;
}

static String& hostname()
{
    static String s_hostname;
    if (s_hostname.is_null()) {
        char buffer[HOST_NAME_MAX];
        if (gethostname(buffer, sizeof(buffer)) == 0)
            s_hostname = buffer;
        else
            s_hostname = "localhost";
    }
    return s_hostname;
}

static size_t print_name(const struct stat& st, String const& name, char const* path_for_link_resolution, char const* path_for_hyperlink)
{
    if (!flag_disable_hyperlinks) {
        auto full_path = Core::File::real_path_for(path_for_hyperlink);
        if (!full_path.is_null()) {
            auto url = URL::create_with_file_scheme(full_path, {}, hostname());
            out("\033]8;;{}\033\\", url.serialize());
        }
    }

    size_t nprinted = 0;

    if (!flag_colorize || !output_is_terminal) {
        nprinted = printf("%s", name.characters());
    } else {
        char const* begin_color = "";
        char const* end_color = "\033[0m";

        if (st.st_mode & S_ISVTX)
            begin_color = "\033[42;30;1m";
        else if (st.st_mode & S_ISUID)
            begin_color = "\033[41;1m";
        else if (st.st_mode & S_ISGID)
            begin_color = "\033[43;1m";
        else if (S_ISLNK(st.st_mode))
            begin_color = "\033[36;1m";
        else if (S_ISDIR(st.st_mode))
            begin_color = "\033[34;1m";
        else if (st.st_mode & 0111)
            begin_color = "\033[32;1m";
        else if (S_ISSOCK(st.st_mode))
            begin_color = "\033[35;1m";
        else if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))
            begin_color = "\033[33;1m";
        printf("%s", begin_color);
        nprinted = print_escaped(name);
        printf("%s", end_color);
    }
    if (S_ISLNK(st.st_mode)) {
        if (path_for_link_resolution) {
            auto link_destination_or_error = Core::File::read_link(path_for_link_resolution);
            if (link_destination_or_error.is_error()) {
                perror("readlink");
            } else {
                nprinted += printf(" -> ") + print_escaped(link_destination_or_error.value());
            }
        } else {
            if (flag_classify)
                nprinted += printf("@");
        }
    } else if (S_ISDIR(st.st_mode)) {
        if (flag_classify)
            nprinted += printf("/");
    } else if (st.st_mode & 0111) {
        if (flag_classify)
            nprinted += printf("*");
    }

    if (!flag_disable_hyperlinks) {
        printf("\033]8;;\033\\");
    }

    return nprinted;
}

static bool print_filesystem_object(String const& path, String const& name, const struct stat& st)
{
    if (flag_show_inode)
        printf("%s ", String::formatted("{}", st.st_ino).characters());

    if (S_ISDIR(st.st_mode))
        printf("d");
    else if (S_ISLNK(st.st_mode))
        printf("l");
    else if (S_ISBLK(st.st_mode))
        printf("b");
    else if (S_ISCHR(st.st_mode))
        printf("c");
    else if (S_ISFIFO(st.st_mode))
        printf("f");
    else if (S_ISSOCK(st.st_mode))
        printf("s");
    else if (S_ISREG(st.st_mode))
        printf("-");
    else
        printf("?");

    printf("%c%c%c%c%c%c%c%c",
        st.st_mode & S_IRUSR ? 'r' : '-',
        st.st_mode & S_IWUSR ? 'w' : '-',
        st.st_mode & S_ISUID ? 's' : (st.st_mode & S_IXUSR ? 'x' : '-'),
        st.st_mode & S_IRGRP ? 'r' : '-',
        st.st_mode & S_IWGRP ? 'w' : '-',
        st.st_mode & S_ISGID ? 's' : (st.st_mode & S_IXGRP ? 'x' : '-'),
        st.st_mode & S_IROTH ? 'r' : '-',
        st.st_mode & S_IWOTH ? 'w' : '-');

    if (st.st_mode & S_ISVTX)
        printf("t");
    else
        printf("%c", st.st_mode & S_IXOTH ? 'x' : '-');

    printf(" %3u", st.st_nlink);

    auto username = users.get(st.st_uid);
    if (!flag_print_numeric && username.has_value()) {
        printf(" %7s", username.value().characters());
    } else {
        printf(" %7u", st.st_uid);
    }

    if (!flag_hide_group) {
        auto groupname = groups.get(st.st_gid);
        if (!flag_print_numeric && groupname.has_value()) {
            printf(" %7s", groupname.value().characters());
        } else {
            printf(" %7u", st.st_gid);
        }
    }

    if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
        printf("  %4u,%4u ", major(st.st_rdev), minor(st.st_rdev));
    } else {
        if (flag_human_readable) {
            printf(" %10s ", human_readable_size(st.st_size).characters());
        } else {
            printf(" %10" PRIu64 " ", (uint64_t)st.st_size);
        }
    }

    printf("  %s  ", Core::DateTime::from_timestamp(st.st_mtime).to_string().characters());

    print_name(st, name, path.characters(), path.characters());

    printf("\n");
    return true;
}

static int do_file_system_object_long(char const* path)
{
    if (flag_list_directories_only) {
        struct stat stat {
        };
        int rc = lstat(path, &stat);
        if (rc < 0)
            perror("lstat");
        if (print_filesystem_object(path, path, stat))
            return 0;
        return 2;
    }

    auto flags = Core::DirIterator::SkipDots;
    if (flag_show_dotfiles)
        flags = Core::DirIterator::Flags::NoFlags;
    if (flag_show_almost_all_dotfiles)
        flags = Core::DirIterator::SkipParentAndBaseDir;

    Core::DirIterator di(path, flags);

    if (di.has_error()) {
        if (di.error() == ENOTDIR) {
            struct stat stat {
            };
            int rc = lstat(path, &stat);
            if (rc < 0)
                perror("lstat");
            if (print_filesystem_object(path, path, stat))
                return 0;
            return 2;
        }
        fprintf(stderr, "%s: %s\n", path, di.error_string());
        return 1;
    }

    Vector<FileMetadata> files;
    while (di.has_next()) {
        FileMetadata metadata;
        metadata.name = di.next_path();
        VERIFY(!metadata.name.is_empty());

        if (metadata.name.ends_with('~') && flag_ignore_backups && metadata.name != path)
            continue;

        StringBuilder builder;
        builder.append({ path, strlen(path) });
        builder.append('/');
        builder.append(metadata.name);
        metadata.path = builder.to_string();
        VERIFY(!metadata.path.is_null());
        int rc = lstat(metadata.path.characters(), &metadata.stat);
        if (rc < 0)
            perror("lstat");

        files.append(move(metadata));
    }

    quick_sort(files, filemetadata_comparator);

    for (auto& file : files) {
        if (!print_filesystem_object(file.path, file.name, file.stat))
            return 2;
    }
    return 0;
}

static bool print_filesystem_object_short(char const* path, char const* name, size_t* nprinted)
{
    struct stat st;
    int rc = lstat(path, &st);
    if (rc == -1) {
        printf("lstat(%s) failed: %s\n", path, strerror(errno));
        return false;
    }

    if (flag_show_inode)
        printf("%s ", String::formatted("{}", st.st_ino).characters());

    *nprinted = print_name(st, name, nullptr, path);
    return true;
}

static bool print_names(char const* path, size_t longest_name, Vector<FileMetadata> const& files)
{
    size_t printed_on_row = 0;
    size_t nprinted = 0;
    for (size_t i = 0; i < files.size(); ++i) {
        auto& name = files[i].name;
        StringBuilder builder;
        builder.append({ path, strlen(path) });
        builder.append('/');
        builder.append(name);
        if (!print_filesystem_object_short(builder.to_string().characters(), name.characters(), &nprinted))
            return 2;
        int offset = 0;
        if (terminal_columns > longest_name)
            offset = terminal_columns % longest_name / (terminal_columns / longest_name);

        // The offset must be at least 2 because:
        // - With each file an additional char is printed e.g. '@','*'.
        // - Each filename must be separated by a space.
        size_t column_width = longest_name + max(offset, 2);
        printed_on_row += column_width;

        if (is_a_tty) {
            for (size_t j = nprinted; i != (files.size() - 1) && j < column_width; ++j)
                printf(" ");
        }
        if ((printed_on_row + column_width) >= terminal_columns || flag_force_newline) {
            printf("\n");
            printed_on_row = 0;
        }
    }
    return printed_on_row;
}

int do_file_system_object_short(char const* path)
{
    if (flag_list_directories_only) {
        size_t nprinted = 0;
        bool status = print_filesystem_object_short(path, path, &nprinted);
        printf("\n");
        if (status)
            return 0;
        return 2;
    }

    auto flags = Core::DirIterator::SkipDots;
    if (flag_show_dotfiles)
        flags = Core::DirIterator::Flags::NoFlags;
    if (flag_show_almost_all_dotfiles)
        flags = Core::DirIterator::SkipParentAndBaseDir;

    Core::DirIterator di(path, flags);
    if (di.has_error()) {
        if (di.error() == ENOTDIR) {
            size_t nprinted = 0;
            bool status = print_filesystem_object_short(path, path, &nprinted);
            printf("\n");
            if (status)
                return 0;
            return 2;
        }
        fprintf(stderr, "%s: %s\n", path, di.error_string());
        return 1;
    }

    Vector<FileMetadata> files;
    size_t longest_name = 0;
    while (di.has_next()) {
        FileMetadata metadata;
        metadata.name = di.next_path();

        if (metadata.name.ends_with('~') && flag_ignore_backups && metadata.name != path)
            continue;

        StringBuilder builder;
        builder.append({ path, strlen(path) });
        builder.append('/');
        builder.append(metadata.name);
        metadata.path = builder.to_string();
        VERIFY(!metadata.path.is_null());
        int rc = lstat(metadata.path.characters(), &metadata.stat);
        if (rc < 0)
            perror("lstat");

        files.append(metadata);
        if (metadata.name.length() > longest_name)
            longest_name = metadata.name.length();
    }
    quick_sort(files, filemetadata_comparator);

    if (print_names(path, longest_name, files))
        printf("\n");
    return 0;
}

bool filemetadata_comparator(FileMetadata& a, FileMetadata& b)
{
    if (flag_sort_by_timestamp && (a.stat.st_mtime != b.stat.st_mtime))
        return (a.stat.st_mtime > b.stat.st_mtime) ^ flag_reverse_sort;
    return (a.name < b.name) ^ flag_reverse_sort;
}