hence/src/lib/lexer.rs

use crate::assembler;
use itertools::{Itertools, PeekingNext};

#[derive(Debug)]
pub enum Token {
    Comment(String),

    StringLiteral(String),
    MacroLiteral(String),
    Literal(String),
    Number(String),

    Comma,
    Colon,
    LParen,
    RParen,

    Assign,

    Add,
    Sub,
    Mul,
    Div,
    Pow,

    Newline(String),
    Whitespace(String),
}

impl assembler::ToAssembly for Token {
    fn to_assembly(&self) -> String {
        match self {
            Token::Comment(x) => format!(";{x}"),
            Token::StringLiteral(x) => format!("\"{x}\""),
            Token::MacroLiteral(x) => x.clone(),
            Token::Literal(x) => x.clone(),
            Token::Number(x) => x.clone(),
            Token::Comma => ",".to_string(),
            Token::Colon => ":".to_string(),
            Token::LParen => "(".to_string(),
            Token::RParen => ")".to_string(),
            Token::Assign => "=".to_string(),
            Token::Add => "+".to_string(),
            Token::Sub => "-".to_string(),
            Token::Mul => "*".to_string(),
            Token::Div => "/".to_string(),
            Token::Pow => "**".to_string(),
            Token::Newline(x) | Token::Whitespace(x) => x.clone(),
        }
    }
}

pub fn lex(source: String) -> Result<Vec<Token>, String> {
    let mut chars = source.chars().peekable();
    let mut tokens = Vec::<Token>::new();

    while let Some(&ch) = chars.peek() {
        match ch {
            // ';' => {
            //     chars.next();
            //     chars.next_if(|c| *c == ';');

            //     tokens.push(Token::Comment(
            //         chars.peeking_take_while(|c| *c != '\n').collect::<String>(),
            //     ));
            // }
            ';' | '@' => {
                chars.next();
                chars.next_if(|c| *c == ';' || *c == '@');

                tokens.push(Token::Comment(
                    chars.peeking_take_while(|c| *c != '\n').collect::<String>(),
                ));
            }
            '"' => {
                chars.next();
                tokens.push(Token::StringLiteral(
                    chars.by_ref().take_while(|c| *c != '"').collect::<String>(),
                ));
            }
            '.' => {
                chars.next();
                tokens.push(Token::MacroLiteral(format!(
                    ".{}",
                    chars
                        .peeking_take_while(|c| c.is_alphabetic() || c.is_numeric() || *c == '_')
                        .collect::<String>()
                )));
            }
            ch if ch.is_alphabetic() => {
                let name: String = chars
                    .peeking_take_while(|c| c.is_alphabetic() || c.is_numeric() || *c == '_')
                    .collect();

                tokens.push(Token::Literal(name));
            }
            ch if ch.is_numeric() => {
                tokens.push(Token::Number(
                    chars
                        .peeking_take_while(|c| c.is_alphanumeric() || *c == '_')
                        .collect::<String>(),
                ));
            }
            ',' => {
                tokens.push(Token::Comma);
                chars.next();
            }
            ':' => {
                tokens.push(Token::Colon);
                chars.next();
            }
            '(' => {
                tokens.push(Token::LParen);
                chars.next();
            }
            ')' => {
                tokens.push(Token::RParen);
                chars.next();
            }
            '=' => {
                tokens.push(Token::Assign);
                chars.next();
            }
            '+' => {
                tokens.push(Token::Add);
                chars.next();
            }
            '-' => {
                tokens.push(Token::Sub);
                chars.next();
            }
            '*' => {
                chars.next();
                tokens.push(if chars.peeking_next(|c| *c == '*').is_some() {
                    Token::Pow
                } else {
                    Token::Mul
                });
            }
            '/' => {
                tokens.push(Token::Div);
                chars.next();
            }
            '\n' => {
                tokens.push(Token::Newline(
                    chars.peeking_take_while(|c| *c == '\n').collect::<String>(),
                ));
            }
            ch if ch.is_whitespace() => {
                tokens.push(Token::Whitespace(
                    chars
                        .peeking_take_while(|c| c.is_whitespace() && *c != '\n')
                        .collect::<String>(),
                ));
            }
            _ => {
                // tokens.push(Token::Error(ch.to_string()));
                // chars.next();
                return Err(format!("Unexpected token: '{ch}'"));
            }
        }
    }

    Ok(tokens)
}