use std::io;
use std::io::Write;
use std::io::BufRead;
use std::char;

fn main() {
    println!("Unnamed language 0.01");
    repl();
}

#[derive(Debug)]
enum Token {
    EOF,
    Separator,
    LParen,
    RParen,
    Comma,
    NumLiteral(f64),
    StrLiteral(String),
    Identifier(String)
    /* Keyword(Keyword) */ //implement in future

}

#[derive(Debug)]
enum ASTNode {
    Name(String),
    Number(f64),
    BinOp(Box<ASTNode>, Box<ASTNode>, Box<ASTNode>)
}

enum ParseResult<'a> {
    Ok(ASTNode, &'a [Token]),
    Err(String, &'a [Token])
}

fn repl() {
    let stdin = io::stdin();
    let mut stdout = io::stdout();
    let mut buf = String::with_capacity(20);
    loop {
        print!(">> ");
        stdout.flush().ok();
        let line = stdin.lock().read_line(&mut buf);
        match line {
            Ok(_) => {
                if buf.is_empty() {
                    break;
                }
                let tokens = tokenize(&buf);
                buf.clear();
                println!("Tokens: {:?}", tokens);

                match parse(tokens) {
                    ParseResult::Ok(ast, _) => println!("AST: {:?}", ast),
                    ParseResult::Err(err, _) => println!("Error: {}", err)
                }

                /*
                let eval = evaluate(&ast);
                println!("{}", eval);
                */
            },
            Err(err) => {
                println!("Error: {}", err);
            }
        }
    }
}


fn tokenize(input: &str) -> Vec<Token> {
    let mut tokens = Vec::new();
    let mut iterator = input.chars().peekable();

    fn ends_identifier(c: char) -> bool {
        match c {
            c if char::is_whitespace(c) => true,
            ',' => true,
            ';' => true,
            '(' => true,
            ')' => true,
            _ => false
        }
    }

    while let Some(c) = iterator.next() {
        if char::is_whitespace(c) {
            continue;
        } else if c == '"' {

            let mut buffer = String::with_capacity(20);
            while let Some(x) = iterator.next() {
                if x == '"' {
                    break;
                }
                buffer.push(x);
            }
            tokens.push(Token::StrLiteral(buffer));

        } else if c == '#' {
            while let Some(x) = iterator.next() {
                if x == '\n' {
                    break;
                }
            }
        } else if c == ';' || c == '\n' {
            tokens.push(Token::Separator);
        } else if c == '(' {
            tokens.push(Token::LParen);
        } else if c == ')' {
            tokens.push(Token::RParen);
        } else if c == ',' {
            tokens.push(Token::Comma);
        } else {
            let mut buffer = String::with_capacity(20);
            buffer.push(c);

            while let Some(x) = iterator.peek().cloned() {
                if ends_identifier(x) {
                    break;
                }
                buffer.push(iterator.next().unwrap());
            }

            match buffer.parse::<f64>() {
                Ok(f) => tokens.push(Token::NumLiteral(f)),
                _ => tokens.push(Token::Identifier(buffer))
            }
        }
    }
    tokens.push(Token::EOF);
    tokens
}

fn parse<'a>(input: Vec<Token>) -> ParseResult<'a> {

    let mut tokens = input.iter().peekable();


    return ParseResult::Ok(ASTNode::Name("Hella".to_string()), &[]);
}