#include <AK/String.h>
#include <AK/QuickSort.h>
#include <AK/StringBuilder.h>
#include <AK/Vector.h>
#include <LibCore/CDirIterator.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>

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

static bool flag_colorize = true;
static bool flag_long = false;
static bool flag_show_dotfiles = false;
static bool flag_show_inode = false;
static bool flag_print_numeric = false;

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

int main(int argc, char** argv)
{
    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;
    }

    static const char* valid_option_characters = "laiGn";
    int opt;
    while ((opt = getopt(argc, argv, valid_option_characters)) != -1) {
        switch (opt) {
        case 'a':
            flag_show_dotfiles = true;
            break;
        case 'l':
            flag_long = true;
            break;
        case 'G':
            flag_colorize = false;
            break;
        case 'i':
            flag_show_inode = true;
            break;
        case 'n':
            flag_print_numeric = true;
            break;

        default:
            fprintf(stderr, "usage: ls [-%s] [paths...]\n", valid_option_characters);
            return 1;
        }
    }

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

    int status = 0;
    if (optind >= argc) {
        status = do_file_system_object(".");
    } else if (optind + 1 >= argc) {
        status = do_file_system_object(argv[optind]);
    } else {
        for (; optind < argc; ++optind) {
            printf("%s:\n", argv[optind]);
            status = do_file_system_object(argv[optind]);
        }
    }
    return status;
}

int print_name(struct stat& st, const char* name, const char* path_for_link_resolution = nullptr)
{
    int nprinted = strlen(name);
    if (!flag_colorize || !output_is_terminal) {
        printf("%s", name);
    } else {
        const char* begin_color = "";
        const char* end_color = "\033[0m";

        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%s%s", begin_color, name, end_color);
    }
    if (S_ISLNK(st.st_mode)) {
        if (path_for_link_resolution) {
            char linkbuf[256];
            ssize_t nread = readlink(path_for_link_resolution, linkbuf, sizeof(linkbuf));
            if (nread < 0)
                perror("readlink failed");
            else
                nprinted += printf(" -> %s", linkbuf);
        } else {
            nprinted += printf("@");
        }
    } else if (S_ISDIR(st.st_mode)) {
        nprinted += printf("/");
    } else if (st.st_mode & 0111) {
        nprinted += printf("*");
    }
    return nprinted;
}

bool print_filesystem_object(const char* path, const char* name)
{
    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("%08u ", st.st_ino);

    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' : '-');

    passwd* pwd = getpwuid(st.st_uid);
    group* grp = getgrgid(st.st_gid);
    if (!flag_print_numeric && pwd) {
        printf(" %5s", pwd->pw_name);
    } else {
        printf(" %5u", st.st_uid);
    }
    if (!flag_print_numeric && grp) {
        printf(" %5s", grp->gr_name);
    } else {
        printf(" %5u", 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
        printf(" %10u ", st.st_size);

    auto* tm = localtime(&st.st_mtime);
    printf("  %4u-%02u-%02u %02u:%02u:%02u  ",
        tm->tm_year + 1900,
        tm->tm_mon + 1,
        tm->tm_mday,
        tm->tm_hour,
        tm->tm_min,
        tm->tm_sec);

    print_name(st, name, path);

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

int do_file_system_object_long(const char* path)
{
    CDirIterator di(path, !flag_show_dotfiles ? CDirIterator::SkipDots : CDirIterator::Flags::NoFlags);
    if (di.has_error()) {
        if (di.error() == ENOTDIR) {
            if (print_filesystem_object(path, path))
                return 0;
            return 2;
        }
        fprintf(stderr, "CDirIterator: %s\n", di.error_string());
        return 1;
    }

    Vector<String, 1024> names;
    while (di.has_next())
        names.append(di.next_path());
    quick_sort(names.begin(), names.end(), [](auto& a, auto& b) { return a < b; });

    for (auto& name : names) {
        ASSERT(!name.is_empty());
        if (name[0] == '.' && !flag_show_dotfiles)
            continue;
        StringBuilder builder;
        builder.append(path);
        builder.append('/');
        builder.append(name);
        if (!print_filesystem_object(builder.to_string().characters(), name.characters()))
            return 2;
    }
    return 0;
}

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

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

int do_file_system_object_short(const char* path)
{
    CDirIterator di(path, !flag_show_dotfiles ? CDirIterator::SkipDots : CDirIterator::Flags::NoFlags);
    if (di.has_error()) {
        if (di.error() == ENOTDIR) {
            int nprinted;
            bool status = print_filesystem_object_short(path, path, &nprinted);
            printf("\n");
            if (status)
                return 0;
            return 2;
        }
        fprintf(stderr, "CDirIterator: %s\n", di.error_string());
        return 1;
    }

    Vector<String, 1024> names;
    int longest_name = 0;
    while (di.has_next()) {
        String name = di.next_path();
        names.append(name);
        if (names.last().length() > longest_name)
            longest_name = name.length();
    }
    quick_sort(names.begin(), names.end(), [](auto& a, auto& b) { return a < b; });

    int printed_on_row = 0;
    int nprinted;
    for (int i = 0; i < names.size(); ++i) {
        auto& name = names[i];
        StringBuilder builder;
        builder.append(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 aditional char is printed e.g. '@','*'.
        // - Each filename must be separated by a space.
        int column_width = longest_name + (offset > 0 ? offset : 2);
        printed_on_row += column_width;

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