use yazi_shared::{event::Cmd, render};

use crate::select::Select;

pub struct Opt {
	step: isize,
}

impl From<Cmd> for Opt {
	fn from(mut c: Cmd) -> Self {
		Self { step: c.take_first_str().and_then(|s| s.parse().ok()).unwrap_or(0) }
	}
}

impl Select {
	fn next(&mut self, step: usize) {
		let len = self.items.len();
		if len == 0 {
			return;
		}

		let old = self.cursor;
		self.cursor = (self.cursor + step).min(len - 1);

		let limit = self.limit();
		if self.cursor >= len.min(self.offset + limit) {
			self.offset = len.saturating_sub(limit).min(self.offset + self.cursor - old);
		}

		render!(old != self.cursor);
	}

	fn prev(&mut self, step: usize) {
		let old = self.cursor;
		self.cursor = self.cursor.saturating_sub(step);

		if self.cursor < self.offset {
			self.offset = self.offset.saturating_sub(old - self.cursor);
		}

		render!(old != self.cursor);
	}

	pub fn arrow(&mut self, opt: impl Into<Opt>) {
		let opt = opt.into() as Opt;
		if opt.step > 0 { self.next(opt.step as usize) } else { self.prev(opt.step.unsigned_abs()) }
	}
}