//
// sdn: simple directory navigator
//
// Copyright (c) 2017, Přemysl Janouch <p.janouch@gmail.com>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//

#include <string>
#include <vector>
#include <locale>
#include <iostream>
#include <algorithm>
#include <cwchar>
#include <climits>

#include <ncurses.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/inotify.h>
#include <fcntl.h>

// Unicode is complex enough already and we might make assumptions
#ifndef __STDC_ISO_10646__
#error Unicode required for wchar_t
#endif

using namespace std;

// For some reason handling of encoding in C and C++ is extremely annoying
// and C++17 ironically obsoletes C++11 additions that made it less painful
static wstring
to_wide (const string &multi) {
	wstring wide; wchar_t w; mbstate_t mb {};
	size_t n = 0, len = multi.length () + 1;
	while (auto res = mbrtowc (&w, multi.c_str () + n, len - n, &mb)) {
		if (res == size_t (-1) || res == size_t (-2))
			return L"/invalid encoding/";

		n += res;
		wide += w;
	}
	return wide;
}

static string
to_mb (const wstring &wide) {
	string mb; char buf[MB_LEN_MAX + 1]; mbstate_t mbs {};
	for (size_t n = 0; n <= wide.length (); n++) {
		auto res = wcrtomb (buf, wide.c_str ()[n], &mbs);
		if (res == size_t (-1))
			throw invalid_argument ("invalid encoding");
		mb.append (buf, res);
	}
	// There's one extra NUL character added by wcrtomb()
	mb.erase (mb.length () - 1);
	return mb;
}

static int
print (const wstring &wide, int limit) {
	int total_width = 0;
	for (wchar_t w : wide) {
		// TODO: controls as ^X, show in inverse
		if (!isprint (w))
			w = L'?';

		int width = wcwidth (w);
		if (total_width + width > limit)
			break;

		cchar_t c = {};
		c.chars[0] = w;
		add_wch (&c);
		total_width += width;
	}
	return total_width;
}

static int
prefix (const wstring &in, const wstring &of) {
	int score = 0;
	for (size_t i = 0; i < of.size () && in.size () >= i && in[i] == of[i]; i++)
		score++;
	return score;
}

static string
shell_escape (const string &v) {
	string result;
	for (auto c : v)
		if (c == '\'')
			result += "'\\''";
		else
			result += c;
	return "'" + result + "'";
}

// --- Application -------------------------------------------------------------

#define CTRL 31 &

struct entry {
	string filename;
	struct stat info;
	bool operator< (const entry &other) {
		auto a = S_ISDIR (info.st_mode);
		auto b = S_ISDIR (other.info.st_mode);
		return (a && !b) || (a == b && filename < other.filename);
	}
};

// Between std and ncurses, make at least the globals stand out
static struct {
	string cwd;
	vector<entry> entries;
	int offset, cursor;
	string chosen;
	bool chosen_full;
	int inotify_fd, inotify_wd = -1;
	bool out_of_date;

	wchar_t editor;
	wstring editor_line;
} g;

static inline int visible_lines () { return max (0, LINES - 2); }

static void
update () {
	erase ();

	int available = visible_lines ();
	int used = min (available, int (g.entries.size ()) - g.offset);
	for (int i = 0; i < used; i++) {
		attrset (0);
		int index = g.offset + i;
		if (index == g.cursor)
			attron (A_REVERSE);

		move (available - used + i, 0);
		auto &entry = g.entries[index];

		// TODO display more information from "info"
		char modes[] = "- ";
		const auto &stat = entry.info;
		if (S_ISDIR  (stat.st_mode)) modes[0] = 'd';
		if (S_ISBLK  (stat.st_mode)) modes[0] = 'b';
		if (S_ISCHR  (stat.st_mode)) modes[0] = 'c';
		if (S_ISLNK  (stat.st_mode)) modes[0] = 'l';
		if (S_ISFIFO (stat.st_mode)) modes[0] = 'p';
		if (S_ISSOCK (stat.st_mode)) modes[0] = 's';
		addstr (modes);

		// TODO show symbolic link target
		auto width = COLS - 2;
		hline (' ', width - print (to_wide (entry.filename), width));
	}

	attrset (A_BOLD);
	mvprintw (LINES - 2, 0, "%s", g.cwd.c_str ());
	if (g.out_of_date)
		addstr (" [+]");

	attrset (0);
	if (g.editor) {
		move (LINES - 1, 0);
		wchar_t prefix[] = { g.editor, L' ', L'\0' };
		addwstr (prefix);
		move (LINES - 1, print (g.editor_line, COLS - 3) + 2);
		curs_set (1);
	} else
		curs_set (0);

	refresh ();
}

static void
reload () {
	char buf[4096];
	g.cwd = getcwd (buf, sizeof buf);

	auto dir = opendir (".");
	g.entries.clear ();
	while (auto f = readdir (dir)) {
		// Two dots are for navigation but this ain't as useful
		if (f->d_name == string ("."))
			continue;

		struct stat sb = {};
		lstat (f->d_name, &sb);
		g.entries.push_back ({ f->d_name, sb });
	}
	closedir (dir);
	sort (begin (g.entries), end (g.entries));
	g.out_of_date = false;

	g.cursor = min (g.cursor, int (g.entries.size ()) - 1);
	g.offset = min (g.offset, int (g.entries.size ()) - 1);
	update ();

	if (g.inotify_wd != -1)
		inotify_rm_watch (g.inotify_fd, g.inotify_wd);

	g.inotify_wd = inotify_add_watch (g.inotify_fd, buf,
		IN_ALL_EVENTS | IN_ONLYDIR);
}

static void
search (const wstring &needle) {
	int best = g.cursor, best_n = 0;
	for (int i = 0; i < int (g.entries.size ()); i++) {
		auto o = (i + g.cursor) % g.entries.size ();
		int n = prefix (to_wide (g.entries[o].filename), needle);
		if (n > best_n) {
			best = o;
			best_n = n;
		}
	}
	g.cursor = best;
}

static void
handle_editor (wint_t c, bool is_char) {
	if (c == 27 || c == (CTRL L'g')) {
		g.editor_line.clear ();
		g.editor = 0;
	} else if (c == L'\r' || (!is_char && c == KEY_ENTER)) {
		if (g.editor == L'e') {
			auto mb = to_mb (g.editor_line);
			rename (g.entries[g.cursor].filename.c_str (), mb.c_str ());
			reload ();
		}
		g.editor_line.clear ();
		g.editor = 0;
	} else if (is_char) {
		g.editor_line += c;
		if (g.editor == L'/'
		 || g.editor == L's')
			search (g.editor_line);
	} else if (c == KEY_BACKSPACE) {
		if (!g.editor_line.empty ())
			g.editor_line.erase (g.editor_line.length () - 1);
	} else
		beep ();
}

static bool
handle (wint_t c, bool is_char) {
	// If an editor is active, let it handle the key instead and eat it
	if (g.editor) {
		handle_editor (c, is_char);
		c = WEOF;
	}

	// Translate the Alt key into a bit outside the range of Unicode
	enum { ALT = 1 << 24 };
	if (c == 27) {
		if (get_wch (&c) == ERR) {
			beep ();
			return true;
		}
		c |= ALT;
	}

	const auto &current = g.entries[g.cursor];
	switch (c) {
	case ALT | L'\r':
	case ALT | KEY_ENTER:
		g.chosen_full = true;
		g.chosen = current.filename;
		return false;
	case L'\r':
	case KEY_ENTER:
	{
		bool is_dir = S_ISDIR (current.info.st_mode) != 0;
		// Dive into directories and accessible symlinks to them
		if (S_ISLNK (current.info.st_mode)) {
			char buf[PATH_MAX];
			struct stat sb = {};
			auto len = readlink (current.filename.c_str (), buf, sizeof buf);
			is_dir = len > 0 && size_t (len) < sizeof buf
				&& !stat (current.filename.c_str (), &sb)
				&& S_ISDIR (sb.st_mode) != 0;
		}
		if (!is_dir) {
			g.chosen = current.filename;
			return false;
		}
		if (!chdir (current.filename.c_str ())) {
			g.cursor = 0;
			reload ();
		}
		break;
	}

	// M-o ought to be the same shortcut the navigator is launched with
	case ALT | L'o':
	case L'q':
		return false;

	case L'k': case CTRL L'p': case KEY_UP:
		g.cursor--;
		break;
	case L'j': case CTRL L'n': case KEY_DOWN:
		g.cursor++;
		break;
	case L'g': case ALT | L'<': case KEY_HOME:
		g.cursor = 0;
		break;
	case L'G': case ALT | L'>': case KEY_END:
		g.cursor = int (g.entries.size ()) - 1;
		break;

	case KEY_PPAGE: g.cursor -= LINES; break;
	case KEY_NPAGE: g.cursor += LINES; break;

	case CTRL L'e': g.offset++; break;
	case CTRL L'y': g.offset--; break;

	case ALT | L'e':
		g.editor_line = to_wide (current.filename);
		// Fall-through
	case L'e':
		g.editor = c & ~ALT;
		break;
	case L'/':
	case L's':
		g.editor = c;
		break;

	case CTRL L'L':
		clear ();
		break;
	case L'r':
		reload ();
		break;
	case KEY_RESIZE:
	case WEOF:
		break;
	default:
		beep ();
	}
	g.cursor = max (g.cursor, 0);
	g.cursor = min (g.cursor, int (g.entries.size ()) - 1);

	// Make sure cursor is visible
	g.offset = max (g.offset, 0);
	g.offset = min (g.offset, int (g.entries.size ()) - 1);

	if (g.offset > g.cursor)
		g.offset = g.cursor;
	if (g.cursor - g.offset >= visible_lines ())
		g.offset = g.cursor - visible_lines () + 1;

	update ();
	return true;
}

static void
inotify_check () {
	// Only provide simple indication that contents might have changed
	char buf[4096]; ssize_t len;
	bool changed = false;
	while ((len = read (g.inotify_fd, buf, sizeof buf)) > 0) {
		const inotify_event *e;
		for (char *ptr = buf; ptr < buf + len; ptr += sizeof *e + e->len) {
			e = (const inotify_event *) buf;
			if (e->wd == g.inotify_wd)
				changed = true;
		}
	}
	if (changed)
		update ();
}

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

	// That bitch zle closes stdin before exec without redirection
	(void) close (STDIN_FILENO);
	if (open ("/dev/tty", O_RDWR)) {
		cerr << "cannot open tty" << endl;
		return 1;
	}

	// Save the original stdout and force ncurses to use the terminal directly
	auto output_fd = dup (STDOUT_FILENO);
	dup2 (STDIN_FILENO, STDOUT_FILENO);

	if ((g.inotify_fd = inotify_init1 (IN_NONBLOCK)) < 0) {
		cerr << "cannot initialize inotify" << endl;
		return 1;
	}

	locale::global (locale (""));
	if (!initscr () || cbreak () == ERR || noecho () == ERR || nonl () == ERR
	 || halfdelay (1) == ERR || keypad (stdscr, TRUE) == ERR) {
		cerr << "cannot initialize screen" << endl;
		return 1;
	}

	reload ();
	auto start_dir = g.cwd;

	wint_t c;
	while (1) {
		inotify_check ();
		int res = get_wch (&c);
		if (res != ERR && !handle (c, res == OK))
			break;
	}
	endwin ();

	// Presumably it is going to end up as an argument, so quote it
	if (!g.chosen.empty ())
		g.chosen = shell_escape (g.chosen);

	// We can't portably create a standard stream from an FD, so modify the FD
	dup2 (output_fd, STDOUT_FILENO);

	if (g.chosen_full) {
		auto full_path = g.cwd + "/" + g.chosen;
		cout << "local insert=" << shell_escape (full_path) << endl;
		return 0;
	}
	if (g.cwd != start_dir)
		cout << "local cd=" << shell_escape (g.cwd) << endl;
	if (!g.chosen.empty ())
		cout << "local insert=" << shell_escape (g.chosen) << endl;
	return 0;
}