use std::fmt;

#[derive(Clone, Copy, Default, Debug, PartialEq, Eq)]
pub struct Pos {
	pub idx: u32,
	pub line: u32,
	pub col: u32,
}

impl std::cmp::PartialOrd for Pos {
	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
		Some(self.cmp(other))
	}
}

impl std::cmp::Ord for Pos {
	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
		self.idx.cmp(&other.idx)
	}
}

impl Pos {
	pub const fn new() -> Self {
		Self {
			idx: 0,
			line: 1,
			col: 1,
		}
	}

	#[must_use]
	pub fn advance(self, c: char) -> Self {
		let idx = self.idx + u32::try_from(c.len_utf8()).unwrap_or_default();
		if c == '\n' {
			Self {
				idx,
				line: self.line + 1,
				col: 1,
			}
		} else {
			Self {
				idx,
				line: self.line,
				col: self.col + 1,
			}
		}
	}
}

impl fmt::Display for Pos {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		write!(f, "{}:{}", self.line, self.col)
	}
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Span {
	pub start: Pos,
	pub end: Pos,
}

impl Span {
	pub const fn new(start: Pos, end: Pos) -> Self {
		if end.idx < start.idx {
			Self {
				start: end,
				end: start,
			}
		} else {
			Self { start, end }
		}
	}

	pub fn of<'a>(&self, s: &'a str) -> &'a str {
		&s[(self.start.idx as usize)..(self.end.idx as usize)]
	}
}

impl fmt::Display for Span {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		write!(f, "{}-{}", self.start, self.end)
	}
}