use nom::{
    branch::alt,
    bytes::complete::{escaped, is_not, tag, take_until},
    character::complete::{alpha1, alphanumeric1, char, multispace0, one_of, space0},
    combinator::{cut, map, opt, recognize, value},
    error::ParseError,
    multi::{fold_many0, many0, separated_list0},
    number::complete::double,
    sequence::{delimited, pair, preceded, terminated, tuple},
    IResult, Parser,
};

use crate::ast::*;

fn sc<'a, E>(i: &'a str) -> IResult<&'a str, (), E>
where
    E: ParseError<&'a str>,
{
    alt((value((), multispace0), pinline_comment, peol_comment))(i)
}
fn pinline_comment<'a, E>(i: &'a str) -> IResult<&'a str, (), E>
where
    E: ParseError<&'a str>,
{
    value((), tuple((tag("/*"), take_until("*/"), tag("*/"))))(i)
}

fn peol_comment<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, (), E> {
    value((), pair(char('/'), is_not("\n\r")))(i)
}

fn semi(i: &str) -> IResult<&str, &str> {
    preceded(sc, tag(";"))(i)
}

fn braces<'a, P, O, E>(a: P) -> impl FnMut(&'a str) -> IResult<&'a str, O, E>
where
    P: Parser<&'a str, O, E>,
    E: ParseError<&'a str>,
{
    map(tuple((tag("{"), sc, a, sc, tag("}"))), |(_, _, a, _, _)| a)
}
fn parens<'a, P, O, E>(a: P) -> impl FnMut(&'a str) -> IResult<&'a str, O, E>
where
    P: Parser<&'a str, O, E>,
    E: ParseError<&'a str>,
{
    map(tuple((tag("("), sc, a, sc, tag(")"))), |(_, _, a, _, _)| a)
}
fn identifier(i: &str) -> IResult<&str, &str> {
    println!("identifier: {}", i);
    preceded(
        sc,
        recognize(pair(
            alt((alpha1, tag("_"))),
            many0(alt((alphanumeric1, tag("_")))),
        )),
    )(i)
}

fn variable(i: &str) -> IResult<&str, Expr> {
    println!("variable: {}", i);
    map(identifier, |a| Expr::Var(a.to_string()))(i)
}

fn parse_str<'a>(i: &'a str) -> IResult<&'a str, &'a str> {
    escaped(alphanumeric1, '\\', one_of("\"n\\"))(i)
}

fn string<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("string: {}", i);
    map(
        preceded(char('\"'), cut(terminated(parse_str, char('\"')))),
        |s| Expr::LStr(String::from(s)),
    )(i)
}

fn boolean<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("boolean: {}", i);
    alt((
        map(tag("true"), |_| Expr::LBool(true)),
        map(tag("false"), |_| Expr::LBool(false)),
    ))(i)
}

fn call<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("call: {}", i);
    map(
        tuple((
            identifier,
            sc,
            alt((
                value(vec![], tuple((char('('), sc, char(')')))),
                delimited(
                    char('('),
                    separated_list0(tuple((sc, tag(","), sc)), expr),
                    char(')'),
                ),
            )),
        )),
        |(i, _, v)| Expr::Call(i.to_string(), v),
    )(i)
}

fn num(i: &str) -> IResult<&str, Expr> {
    println!("num: {}", i);
    map(double, Expr::LNum)(i)
}
fn literal(i: &str) -> IResult<&str, Expr> {
    println!("literal: {}", i);
    alt((num, string, map(tag("null"), |_| Expr::LNull), boolean))(i)
}
fn receive<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("receive: {}", i);
    map(tuple((sc, tag("<-"), expr)), |(_, _, expr)| {
        Expr::Receive(Box::new(expr))
    })(i)
}

fn factor_bin(i: &str) -> IResult<&str, Expr> {
    println!("factor bin: {}", i);
    alt((delimited(space0, alt((receive, term)), space0), expr))(i)
}

fn bin_less_greater(i: &str) -> IResult<&str, Expr> {
    let (i, init) = factor_bin(i)?;

    fold_many0(
        pair(alt((char('<'), char('>'))), factor_bin),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '<' {
                Expr::Binary(BinOp::LessThan, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::GreaterThan, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn bin_equal_not(i: &str) -> IResult<&str, Expr> {
    let (i, init) = bin_less_greater(i)?;

    fold_many0(
        pair(alt((tag("=="), tag("!="))), bin_less_greater),
        move || init.clone(),
        |acc, (op, val)| {
            if op == "==" {
                Expr::Binary(BinOp::Equals, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::NotEquals, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn bin_mult_div(i: &str) -> IResult<&str, Expr> {
    let (i, init) = bin_equal_not(i)?;

    fold_many0(
        pair(alt((char('*'), char('/'))), bin_equal_not),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '*' {
                Expr::Binary(BinOp::Mult, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::Div, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn binary<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("binary: {}", i);
    let (i, init) = bin_mult_div(i)?;

    fold_many0(
        pair(alt((char('+'), char('-'))), bin_mult_div),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '+' {
                Expr::Binary(BinOp::Plus, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::Minus, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}

fn term<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("expr: {}", i);
    delimited(sc, alt((literal, call, variable, parens(expr))), sc)(i)
}

pub fn expr<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    binary(i)
}

fn if_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("if: {}", i);
    map(
        tuple((tag("if"), sc, parens(expr), sc, braces(many0(stmt)))),
        |(_, _, expr, _, stmts)| Stmt::If(expr, stmts),
    )(i)
}
fn while_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("while: {}", i);
    map(
        tuple((tag("while"), sc, parens(expr), sc, braces(many0(stmt)))),
        |(_, _, expr, _, stmts)| Stmt::While(expr, stmts),
    )(i)
}
fn let_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("let: {}", i);
    map(
        tuple((
            tag("let"),
            sc,
            identifier,
            tuple((sc, tag("="), sc)),
            expr,
            semi,
        )),
        |(_, _, id, _, expr, _)| Stmt::Let(id.to_string(), expr),
    )(i)
}
fn yield_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("yield: {}", i);
    map(tuple((tag("yield"), semi)), |_| Stmt::Yield)(i)
}
fn spawn_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("spawn: {}", i);
    map(tuple((tag("spawn"), sc, expr, semi)), |(_, _, expr, _)| {
        Stmt::Spawn(expr)
    })(i)
}
fn return_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("return: {}", i);
    map(
        tuple((tag("return"), sc, opt(expr), semi)),
        |(_, _, expr, _)| Stmt::Return(expr),
    )(i)
}
fn func_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("func: {}", i);
    map(
        tuple((
            tag("fn"),
            sc,
            identifier,
            sc,
            alt((
                value(vec![], tuple((char('('), sc, char(')')))),
                delimited(
                    char('('),
                    separated_list0(
                        tuple((sc, tag(","), sc)),
                        map(identifier, |a| a.to_string()),
                    ),
                    char(')'),
                ),
            )),
            sc,
            braces(many0(stmt)),
        )),
        |(_, _, id, _, params, _, stmts)| Stmt::Func(id.to_string(), params, stmts),
    )(i)
}
fn assign_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("assign: {}", i);
    map(
        tuple((identifier, tuple((sc, tag("="), sc)), expr, semi)),
        |(id, _, expr, _)| Stmt::Assign(id.to_string(), expr),
    )(i)
}
fn send_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("send: {}", i);
    map(
        tuple((expr, tuple((sc, tag("->"), sc)), identifier, semi)),
        |(expr, _, id, _)| Stmt::Send(expr, id.to_string()),
    )(i)
}
fn expr_stmt(i: &str) -> IResult<&str, Stmt> {
    println!("expr: {}", i);
    map(tuple((expr, semi)), |(expr, _)| Stmt::Expr(expr))(i)
}

pub fn stmt(i: &str) -> IResult<&str, Stmt> {
    preceded(
        sc,
        alt((
            if_stmt,
            while_stmt,
            let_stmt,
            yield_stmt,
            spawn_stmt,
            return_stmt,
            func_stmt,
            assign_stmt,
            send_stmt,
            expr_stmt,
        )),
    )(i)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn can_parse_string_lit() {
        let a = r#""hey"  "#;
        let (rest, res) = string(a).unwrap();

        assert_eq!(res, Expr::LStr("hey".to_string()));
        assert_eq!(rest, "  ");
    }

    #[test]
    fn can_parse_binary_op() {
        let a = "3 +3 +  6";
        let (_rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Binary(
                BinOp::Plus,
                Box::new(Expr::Binary(
                    BinOp::Plus,
                    Box::new(Expr::LNum(3.0)),
                    Box::new(Expr::LNum(3.0)),
                )),
                Box::new(Expr::LNum(6.0))
            )
        );
    }

    #[test]
    fn can_parse_binary_op_with_str() {
        let a = r#"3 +3 +  6 + "hey""#;
        let (_rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Binary(
                BinOp::Plus,
                Box::new(Expr::Binary(
                    BinOp::Plus,
                    Box::new(Expr::Binary(
                        BinOp::Plus,
                        Box::new(Expr::LNum(3.0)),
                        Box::new(Expr::LNum(3.0)),
                    )),
                    Box::new(Expr::LNum(6.0))
                )),
                Box::new(Expr::LStr("hey".to_string()))
            )
        );
    }

    #[test]
    fn can_parse_var() {
        let a = "hello";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(res, Expr::Var("hello".to_string()));
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_empty_call() {
        let a = "hello()";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(res, Expr::Call("hello".to_string(), vec![]));
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call_with_var() {
        let a = "hello(hey)";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call("hello".to_string(), vec![Expr::Var("hey".to_string())])
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call() {
        let a = "hello(1.0, 45 , yeah)";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call(
                "hello".to_string(),
                vec![
                    Expr::LNum(1.0),
                    Expr::LNum(45.0),
                    Expr::Var("yeah".to_string())
                ]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call_with_bin_op() {
        let a = "hello(1.0, 45 + 33, yeah)";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call(
                "hello".to_string(),
                vec![
                    Expr::LNum(1.0),
                    Expr::Binary(
                        BinOp::Plus,
                        Box::new(Expr::LNum(45.0)),
                        Box::new(Expr::LNum(33.0))
                    ),
                    Expr::Var("yeah".to_string())
                ]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call_with_string_binop() {
        let a = r#"funFun(null == "ss" + 12, true)"#;
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call(
                "funFun".to_string(),
                vec![
                    Expr::Binary(
                        BinOp::Plus,
                        Box::new(Expr::Binary(
                            BinOp::Equals,
                            Box::new(Expr::LNull),
                            Box::new(Expr::LStr("ss".to_string())),
                        )),
                        Box::new(Expr::LNum(12.0))
                    ),
                    Expr::LBool(true)
                ]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_binop_with_receive() {
        let a = r#"1 + a < 9 - <- chan"#;
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Binary(
                BinOp::Minus,
                Box::new(Expr::Binary(
                    BinOp::Plus,
                    Box::new(Expr::LNum(1.0)),
                    Box::new(Expr::Binary(
                        BinOp::LessThan,
                        Box::new(Expr::Var("a".to_string())),
                        Box::new(Expr::LNum(9.0)),
                    )),
                )),
                Box::new(Expr::Receive(Box::new(Expr::Var("chan".to_string())))),
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_binop_with_receive_and_fun_call() {
        let a = r#"-99 - <- chan + funkyFun(a, false, "hey")"#;
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Binary(
                BinOp::Minus,
                Box::new(Expr::LNum(-99.0)),
                Box::new(Expr::Receive(Box::new(Expr::Binary(
                    BinOp::Plus,
                    Box::new(Expr::Var("chan".to_string())),
                    Box::new(Expr::Call(
                        "funkyFun".to_string(),
                        vec![
                            Expr::Var("a".to_string()),
                            Expr::LBool(false),
                            Expr::LStr("hey".to_string())
                        ]
                    ))
                ))))
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_let_stmt() {
        let a = r#"let a = 0;"#;
        let (rest, res) = stmt(a).unwrap();

        assert_eq!(res, Stmt::Let("a".to_string(), Expr::LNum(0.0)));
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_if_stmt() {
        let a = r#"
  if (n < 2) {
    return n;
  }
"#;
        let (rest, res) = stmt(a).unwrap();

        assert_eq!(
            res,
            Stmt::If(
                Expr::Binary(
                    BinOp::LessThan,
                    Box::new(Expr::Var("n".to_string())),
                    Box::new(Expr::LNum(2.0)),
                ),
                vec![Stmt::Return(Some(Expr::Var("n".to_string())))]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_func() {
        let a = r#"
fn fib(n) {
  if (n < 2) {
    return n;
  }
  return fib(n - 2)
    + fib(n - 1);
}
"#;
        let (rest, res) = stmt(a).unwrap();

        assert_eq!(res, Stmt::Let("a".to_string(), Expr::LNum(0.0)));
        assert_eq!(rest, "");
    }
}