use tui;
use tui::widget;
use io;
use unix::tty;
use memio;
use strings;

export type scrolllist = struct {
	widget: widget::widget,
	items: []str,
	frame: frame,
	cursor: u16,
};

// Return an instance of list. out is the tty file, pos the starting position,
// sz is the size of the widget (if void is used, the maximum possible
// size is used), items is the slice of items of the list.
export fn newscrolllist(state: *tui::tui, pos: widget::coords, sz: widget::widgetsize,
style: (*widget::style | void), items: str...) (scrolllist | tty::error) = {
	const tsz = tty::winsize(state.out)?;

	let end = match (sz) {
	case let sz: tty::ttysize =>
		yield if (tsz.rows < sz.rows) tsz.rows else sz.rows;
	case void =>
		yield tsz.rows;
	};

	if (end > len(items)) {
		end = len(items): u16;
	};

	return scrolllist {
		widget = widget::widget {
			state = state,
			print = &printscrolllist,
			resize = &resizescrolllist,
			finish = &finishscrolllist,
			pos = pos,
			sz = sz,
			style = style,
			damage = widget::damageall,
			...
		},
		items = items,
		frame = frame {
			start = 0,
			end = end,
		},
		cursor = 0u16,
	};
};

fn printscrolllist(widget: *widget::widget) void = {
	const list = widget: *scrolllist;
	let st = memio::dynamic();
	defer io::close(&st)!;
	for (let i = list.frame.start; i < list.frame.end; i += 1) {
		//let item = match (list.widget.sz) {
		//case let sz: tty::ttysize =>
		//	yield strings::sub(list.items[i], 0z, sz.columns);
		//case widget::nosize =>
		//	yield list.items[i];
		//};
		//memio::concat(&st, item)!;
		if (i == list.cursor) {
			memio::concat(&st, "\x1B[7m")!;
		};
		memio::concat(&st, list.items[i])!;
		if (i == list.cursor) {
			memio::concat(&st, "\x1B[27m")!;
		};
		if (i != list.frame.end - 1) {
			memio::concat(&st, widget::NEWLINE)!;
		};
	};
	list.widget.buf = memio::string(&st)!;
	widget::print(list);
};

fn resizescrolllist(widget: *widget::widget, ttysize: tty::ttysize) void = {
	return;
};

fn finishscrolllist(widget: *widget::widget) void = {
	widget::finish(widget);
};

export fn down(li: *scrolllist) void = {
	if (li.cursor == li.frame.end - 1) {
		framedown(li);
	};
	if (li.cursor < len(li.items) - 1) {
		li.cursor += 1;
	};
};

export fn up(li: *scrolllist) void = {
	if (li.cursor == li.frame.start) {
		frameup(li);
	};
	if (li.cursor > 0) {
		li.cursor -= 1;
	};
};

export fn frameup(li: *scrolllist) void = {
	if (li.frame.start > 0) {
		li.frame.start -= 1;
		li.frame.end -= 1;
	};
};

export fn framedown(li: *scrolllist) void = {
	if (li.frame.end < len(li.items)) {
		li.frame.start += 1;
		li.frame.end += 1;
	};
};

export fn top(li: *scrolllist) void = {
	const sz = li.frame.end - li.frame.start;
	li.cursor = 0;
	li.frame.end = sz;
	li.frame.start = 0;
};

export fn bottom(li: *scrolllist) void = {
	const sz = li.frame.end - li.frame.start;
	li.cursor = len(li.items): u16 - 1;
	li.frame.end = len(li.items): u16;
	li.frame.start = len(li.items): u16 - sz;
};