// SPDX-License-Identifier: AGPL-3.0-or-later

//! Lexer implementation using logos.

use logos::{Lexer, Logos};

/// List of operator codes for the lexer
/// Note: Any input symbol that is not in this list is a comment

fn loop_callback(lex: &Lexer<Token>) -> (usize, usize) {
	let span = lex.span();

	(span.start, span.len())
}

/// List of Tokens for the lexer
/// Note: Any input symbol that is not in this list is a comment
#[derive(Clone, Copy, Debug, Logos, PartialEq, Eq)]
#[logos(skip r"[^<>+\-.,\[\]]+")]
pub enum Token {
	/// `>`
	///
	/// Increment the data pointer by one (to point to the next cell to the
	/// right).
	#[token(">")]
	IncrementPointer,

	/// `<`
	///
	/// Decrement the data pointer by one (to point to the next cell to the
	/// left).
	#[token("<")]
	DecrementPointer,

	/// `+`
	///
	/// Increment the byte at the data pointer by one.
	#[token("+")]
	IncrementByte,

	/// `-`
	///
	/// Decrement the byte at the data pointer by one.
	#[token("-")]
	DecrementByte,

	/// `.`
	///
	/// Output the byte at the data pointer.
	#[token(".")]
	OutputByte,

	/// `,`
	///
	/// Accept one byte of input, storing its value in the byte at the data
	/// pointer.
	#[token(",")]
	InputByte,

	/// `[`
	///
	/// If the byte at the data pointer is zero, then instead of moving the
	/// instruction pointer forward to the next command, jump it forward to the
	/// command after the matching ] command.
	#[token("[", loop_callback)]
	StartLoop((usize, usize)),

	/// `]`
	///
	/// If the byte at the data pointer is nonzero, then instead of moving the
	/// instruction pointer forward to the next command, jump it back to the
	/// command after the matching [ command.
	#[token("]", loop_callback)]
	EndLoop((usize, usize)),
}