#include <BAN/Sort.h>
#include <BAN/String.h>
#include <BAN/Time.h>
#include <BAN/Vector.h>

#include <dirent.h>
#include <fcntl.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <sys/stat.h>
#include <termios.h>

struct Config
{
	enum class Visibility {
		Normal,
		AlmostAll,
		All
	};
	Visibility visibility { Visibility::Normal };
	bool show_as_list     { false };
	bool human_readable   { false };
	bool directory        { false };
};

struct simple_entry_t
{
	BAN::String name;
	struct stat st;
	BAN::String link;
};

struct full_entry_t
{
	BAN::String access;
	BAN::String hard_links;
	BAN::String owner_name;
	BAN::String owner_group;
	BAN::String size;
	BAN::String month;
	BAN::String day;
	BAN::String time;
	BAN::String full_name;
};

bool g_stdout_terminal { false };
winsize g_terminal_size {};

const char* entry_color(mode_t mode)
{
	// TODO: handle suid, sgid, sticky

	if (S_ISFIFO(mode) || S_ISCHR(mode) || S_ISBLK(mode))
		return "\e[33m";
	if (S_ISDIR(mode))
		return "\e[34m";
	if (S_ISSOCK(mode))
		return "\e[35m";
	if (S_ISLNK(mode))
		return "\e[36m";
	if (mode & (S_IXUSR | S_IXGRP | S_IXOTH))
		return "\e[32m";
	return "\e[0m";
}

BAN::String build_access_string(mode_t mode, const Config&)
{
	BAN::String access;
	MUST(access.resize(10));
	access[0] = S_ISBLK(mode) ? 'b' : S_ISCHR(mode) ? 'c' : S_ISDIR(mode) ? 'd' : S_ISFIFO(mode) ? 'f' : S_ISLNK(mode) ? 'l' : S_ISSOCK(mode) ? 's' : '-';
	access[1] = (mode & S_IRUSR) ? 'r' : '-';
	access[2] = (mode & S_IWUSR) ? 'w' : '-';
	access[3] = (mode & S_ISUID) ? ((mode & S_IXUSR) ? 's' : 'S') : (mode & S_IXUSR) ? 'x' : '-';
	access[4] = (mode & S_IRGRP) ? 'r' : '-';
	access[5] = (mode & S_IWGRP) ? 'w' : '-';
	access[6] = (mode & S_ISGID) ? ((mode & S_IXGRP) ? 's' : 'S') : (mode & S_IXGRP) ? 'x' : '-';
	access[7] = (mode & S_IROTH) ? 'r' : '-';
	access[8] = (mode & S_IWOTH) ? 'w' : '-';
	access[9] = (mode & S_ISVTX) ? ((mode & S_IXOTH) ? 't' : 'T') : (mode & S_IXOTH) ? 'x' : '-';
	return access;
}

BAN::String build_hard_links_string(nlink_t links, const Config&)
{
	return MUST(BAN::String::formatted("{}", links));
}

BAN::String build_owner_name_string(uid_t uid, const Config&)
{
	struct passwd* passwd = getpwuid(uid);
	if (passwd == nullptr)
		return MUST(BAN::String::formatted("{}", uid));
	return BAN::String(BAN::StringView(passwd->pw_name));
}

BAN::String build_owner_group_string(gid_t gid, const Config&)
{
	struct group* grp = getgrgid(gid);
	if (grp == nullptr)
		return MUST(BAN::String::formatted("{}", gid));
	return BAN::String(BAN::StringView(grp->gr_name));
}

BAN::String build_size_string(off_t size, const Config& config)
{
	if (!config.human_readable || size < 1024)
		return MUST(BAN::String::formatted("{}", size));

	size = size / 1024 * 10;

	size_t suffix_idx = 0;
	for (; size >= 10240; size /= 1024)
		suffix_idx++;

	constexpr char suffix[] { 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y', 'R', 'Q' };
	if (size >= 100)
		return MUST(BAN::String::formatted("{}{}", size / 10, suffix[suffix_idx]));
	return MUST(BAN::String::formatted("{}.{}{}", size / 10, size % 10, suffix[suffix_idx]));
}

BAN::String build_month_string(BAN::Time time, const Config&)
{
	static const char* months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
	return BAN::String(BAN::StringView(months[(time.month - 1) % 12]));
}

BAN::String build_day_string(BAN::Time time, const Config&)
{
	return MUST(BAN::String::formatted("{}", time.day));
}

BAN::String build_time_string(BAN::Time time, const Config&)
{
	static uint32_t current_year = ({ timespec real_time; clock_gettime(CLOCK_REALTIME, &real_time); BAN::from_unix_time(real_time.tv_sec).year; });
	if (time.year != current_year)
		return MUST(BAN::String::formatted("{}", time.year));
	return MUST(BAN::String::formatted("{2}:{2}", time.hour, time.minute));
}

BAN::Vector<size_t> resolve_column_widths(const BAN::Vector<simple_entry_t>& entries, size_t columns)
{
	BAN::Vector<size_t> widths;
	MUST(widths.resize(columns));

	const size_t rows = BAN::Math::div_round_up(entries.size(), columns);
	for (size_t i = 0; i < entries.size(); i++)
		widths[i / rows] = BAN::Math::max(widths[i / rows], entries[i].name.size());

	size_t full_width = (columns - 1);
	for (auto width : widths)
	{
		if (width == 0)
			return {};
		full_width += width;
	}

	if (full_width <= g_terminal_size.ws_col)
		return widths;

	return {};
}

BAN::Vector<size_t> resolve_layout(const BAN::Vector<simple_entry_t>& entries)
{
	for (size_t columns = entries.size(); columns > 1; columns--)
		if (auto widths = resolve_column_widths(entries, columns); !widths.empty())
			return widths;
	return {};
}

int list_directory(const BAN::String& path, Config config)
{
	static char link_buffer[PATH_MAX];

	BAN::Vector<simple_entry_t> entries;

	struct stat st;

	auto stat_func = config.directory ? lstat : stat;
	if (stat_func(path.data(), &st) == -1)
	{
		perror("stat");
		return 2;
	}

	const bool is_directory = S_ISDIR(st.st_mode);

	const size_t block_size = st.st_blksize;
	size_t blocks_used = 0;

	int ret = 0;

	if (!is_directory)
	{
		MUST(entries.emplace_back(path, st, BAN::String()));
		if (S_ISLNK(st.st_mode))
		{
			if (readlink(path.data(), link_buffer, sizeof(link_buffer)) == -1)
				perror("readlink");
			else
				MUST(entries.back().link.append(link_buffer));
		}
	}
	else
	{
		DIR* dirp = opendir(path.data());
		if (dirp == NULL)
		{
			perror("opendir");
			return 2;
		}

		struct dirent* dirent;
		while ((dirent = readdir(dirp)))
		{
			switch (config.visibility)
			{
				case Config::Visibility::Normal:
					if (dirent->d_name[0] == '.')
						continue;
					break;
				case Config::Visibility::AlmostAll:
					if (strcmp(dirent->d_name, ".") == 0 || strcmp(dirent->d_name, "..") == 0)
						continue;
					break;
				case Config::Visibility::All:
					break;
			}

			if (fstatat(dirfd(dirp), dirent->d_name, &st, AT_SYMLINK_NOFOLLOW) == -1)
			{
				perror("fstatat");
				ret = 1;
				continue;
			}

			blocks_used += st.st_blocks;

			MUST(entries.emplace_back(BAN::StringView(dirent->d_name), st, BAN::String()));
			if (S_ISLNK(st.st_mode))
			{
				if (readlinkat(dirfd(dirp), dirent->d_name, link_buffer, sizeof(link_buffer)) == -1)
					perror("readlink");
				else
					MUST(entries.back().link.append(link_buffer));
			}
		}

		closedir(dirp);
	}

	BAN::sort::sort(entries.begin(), entries.end(),
		[](const simple_entry_t& lhs, const simple_entry_t& rhs)
		{
			// sort directories first
			const bool lhs_isdir = S_ISDIR(lhs.st.st_mode);
			const bool rhs_isdir = S_ISDIR(rhs.st.st_mode);
			if (lhs_isdir != rhs_isdir)
				return lhs_isdir;

			// sort by name
			for (size_t i = 0; i < BAN::Math::min(lhs.name.size(), rhs.name.size()); i++)
				if (lhs.name[i] != rhs.name[i])
					return lhs.name[i] < rhs.name[i];
			return lhs.name.size() < rhs.name.size();
		}
	);

	if (!config.show_as_list)
	{
		if (!g_stdout_terminal)
		{
			for (const auto& entry : entries)
				printf("%s\n", entry.name.data());
			return ret;
		}

		bool should_quote = false;
		for (size_t i = 0; i < entries.size() && !should_quote; i++)
			should_quote = entries[i].name.sv().contains(' ');
		if (!should_quote)
			for (auto& entry : entries)
				MUST(entry.name.push_back(' '));
		else
		{
			for (auto& entry : entries)
			{
				const char ch = entry.name.sv().contains(' ') ? '\'' : ' ';
				MUST(entry.name.insert(ch, 0));
				MUST(entry.name.push_back(ch));
			}
		}

		auto layout = resolve_layout(entries);

		if (layout.empty())
			for (const auto& entry : entries)
				printf("%s%s\e[m\n", entry_color(entry.st.st_mode), entry.name.data());
		else
		{
			const size_t cols = layout.size();
			const size_t rows = BAN::Math::div_round_up(entries.size(), cols);

			for (size_t row = 0; row < rows; row++)
			{
				for (size_t col = 0; col < cols; col++)
				{
					const size_t i = col * rows + row;
					if (i >= entries.size())
						break;

					char format[32];
					sprintf(format, "%%s%%-%zus\e[m", layout[col]);

					if (col != 0)
						printf(" ");
					printf(format, entry_color(entries[i].st.st_mode), entries[i].name.data());
				}

				printf("\n");
			}
		}

		return ret;
	}

	BAN::Vector<full_entry_t> full_entries;
	MUST(full_entries.reserve(entries.size()));

	full_entry_t max_entry;
	for (const simple_entry_t& entry : entries)
	{
		full_entry_t full_entry;

#define GET_ENTRY_STRING(property, input)                               \
	full_entry.property = build_ ## property ## _string(input, config); \
	if (full_entry.property.size() > max_entry.property.size())         \
		max_entry.property = full_entry.property;

		GET_ENTRY_STRING(access,		entry.st.st_mode);
		GET_ENTRY_STRING(hard_links,	entry.st.st_nlink);
		GET_ENTRY_STRING(owner_name,	entry.st.st_uid);
		GET_ENTRY_STRING(owner_group,	entry.st.st_gid);
		GET_ENTRY_STRING(size,			entry.st.st_size);

		BAN::Time time = BAN::from_unix_time(entry.st.st_mtim.tv_sec);
		GET_ENTRY_STRING(month,	time);
		GET_ENTRY_STRING(day,	time);
		GET_ENTRY_STRING(time,	time);

		full_entry.full_name = MUST(BAN::String::formatted("{}{}\e[m", entry_color(entry.st.st_mode), entry.name));
		if (S_ISLNK(entry.st.st_mode))
		{
			MUST(full_entry.full_name.append(" -> "_sv));
			MUST(full_entry.full_name.append(entry.link));
		}

		MUST(full_entries.push_back(BAN::move(full_entry)));
	}

	if (is_directory)
	{
		if (config.human_readable)
			printf("total: %s\n", build_size_string(blocks_used * block_size, config).data());
		else
			printf("total: %zu\n", blocks_used);
	}

	for (const auto& full_entry : full_entries)
		printf("%*s %*s %*s %*s %*s %*s %*s %*s %s\n",
			(int)max_entry.access.size(),		full_entry.access.data(),
			(int)max_entry.hard_links.size(),	full_entry.hard_links.data(),
			(int)max_entry.owner_name.size(),	full_entry.owner_name.data(),
			(int)max_entry.owner_group.size(),	full_entry.owner_group.data(),
			(int)max_entry.size.size(),			full_entry.size.data(),
			(int)max_entry.month.size(),		full_entry.month.data(),
			(int)max_entry.day.size(),			full_entry.day.data(),
			(int)max_entry.time.size(),			full_entry.time.data(),
												full_entry.full_name.data()
		);

	return ret;
}

int usage(const char* argv0, int ret)
{
	FILE* fout = ret ? stderr : stdout;
	fprintf(fout, "usage: %s [OPTION]... [FILE]...\n", argv0);
	fprintf(fout, "  -a, --all        show hidden files\n");
	fprintf(fout, "  -l, --list       use list format\n");
	fprintf(fout, "  -d, --directory  show directories as directories, don't list their contents\n");
	fprintf(fout, "  -h, --help       show this message and exit\n");
	return ret;
}

int main(int argc, char* argv[])
{
	Config config;

	for (;;)
	{
		static option long_options[] {
			{ "all",            no_argument, nullptr, 'a' },
			{ "almost-all",     no_argument, nullptr, 'A' },
			{ "directory" ,     no_argument, nullptr, 'd' },
			{ "human-readable", no_argument, nullptr, 'h' },
			{ "list",           no_argument, nullptr, 'l' },
			{ "help",           no_argument, nullptr, 'x' },
		};

		int ch = getopt_long(argc, argv, "aAlh", long_options, nullptr);
		if (ch == -1)
			break;

		switch (ch)
		{
			case 'a':
				config.visibility = Config::Visibility::All;
				break;
			case 'A':
				config.visibility = Config::Visibility::AlmostAll;
				break;
			case 'd':
				config.directory = true;
				break;
			case 'h':
				config.human_readable = true;
				break;
			case 'l':
				config.show_as_list = true;
				break;
			case 'x':
				fprintf(stderr, "usage: %s [OPTION]... [FILE]...\n", argv[0]);
				fprintf(stderr, "  list information about FILEs\n");
				fprintf(stderr, "OPTIONS:\n");
				fprintf(stderr, "  -a, --all             do not ignore entries starting with .\n");
				fprintf(stderr, "  -A, --almost-all      do not list . and ..\n");
				fprintf(stderr, "  -d, --directory       list directories and not their contents\n");
				fprintf(stderr, "  -h, --human-readable  print sizes in human readable form\n");
				fprintf(stderr, "  -l, --list            use long listing format\n");
				fprintf(stderr, "      --help            show this message and exit\n");
				return 0;
			case '?':
				fprintf(stderr, "invalid option %c\n", optopt);
				fprintf(stderr, "see '%s --help' for usage\n", argv[0]);
				return 1;
		}
	}

	BAN::Vector<BAN::String> files;

	if (optind == argc)
		MUST(files.emplace_back("."_sv));
	else for (int i = optind; i < argc; i++)
		MUST(files.emplace_back(BAN::StringView(argv[i])));

	g_stdout_terminal = isatty(STDOUT_FILENO) && tcgetwinsize(STDOUT_FILENO, &g_terminal_size) == 0;

	int ret = 0;
	for (size_t i = 0; i < files.size(); i++)
	{
		if (i > 0)
			printf("\n");
		if (files.size() > 1)
			printf("%s:\n", files[i].data());
		ret = BAN::Math::max(ret, list_directory(files[i], config));
	}

	return ret;
}