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use crate::util::ExprFactory;
use ast::*;
use swc_common::{Fold, FoldWith, Visit, VisitWith};

/// `@babel/plugin-transform-typeof-symbol`
///
/// # Example
/// ## In
///
/// ```js
/// typeof Symbol() === "symbol";
/// ```
///
/// ## Out
/// ```js
/// var _typeof = function (obj) {
///  return obj && obj.constructor === Symbol ? "symbol" : typeof obj;
/// };
///
/// _typeof(Symbol()) === "symbol";
/// ```
#[derive(Clone)]
pub struct TypeOfSymbol;

impl Fold<Expr> for TypeOfSymbol {
    fn fold(&mut self, expr: Expr) -> Expr {
        // fast path
        if !should_work(&expr) {
            return expr;
        }

        let expr = expr.fold_children(self);

        match expr {
            Expr::Unary(UnaryExpr {
                span,
                op: op!("typeof"),
                arg,
            }) => Expr::Call(CallExpr {
                span,
                callee: helper!(span, type_of, "typeof"),
                args: vec![arg.as_arg()],

                type_args: Default::default(),
            }),
            _ => expr,
        }
    }
}

impl Fold<BinExpr> for TypeOfSymbol {
    fn fold(&mut self, expr: BinExpr) -> BinExpr {
        match expr.op {
            op!("==") | op!("!=") | op!("===") | op!("!==") => {}
            _ => return expr.fold_children(self),
        }

        match *expr.left {
            Expr::Unary(UnaryExpr {
                op: op!("typeof"), ..
            }) => {
                if is_non_symbol_literal(&expr.right) {
                    return expr;
                }
            }
            _ => {}
        }
        match *expr.right {
            Expr::Unary(UnaryExpr {
                op: op!("typeof"), ..
            }) => {
                if is_non_symbol_literal(&expr.left) {
                    return expr;
                }
            }
            _ => {}
        }

        expr.fold_children(self)
    }
}

fn should_work(node: &Expr) -> bool {
    struct Visitor {
        found: bool,
    }
    impl Visit<UnaryExpr> for Visitor {
        fn visit(&mut self, e: &UnaryExpr) {
            if e.op == op!("typeof") {
                self.found = true
            }
        }
    }
    let mut v = Visitor { found: false };
    node.visit_with(&mut v);
    v.found
}

fn is_non_symbol_literal(e: &Expr) -> bool {
    match *e {
        Expr::Lit(Lit::Str(Str {
            value: js_word!("undefined"),
            ..
        }))
        | Expr::Lit(Lit::Str(Str {
            value: js_word!("object"),
            ..
        }))
        | Expr::Lit(Lit::Str(Str {
            value: js_word!("boolean"),
            ..
        }))
        | Expr::Lit(Lit::Str(Str {
            value: js_word!("number"),
            ..
        }))
        | Expr::Lit(Lit::Str(Str {
            value: js_word!("string"),
            ..
        }))
        | Expr::Lit(Lit::Str(Str {
            value: js_word!("function"),
            ..
        })) => true,
        _ => false,
    }
}

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

    test!(
        ::swc_ecma_parser::Syntax::default(),
        |_| TypeOfSymbol,
        dont_touch_non_symbol_comparison,
        "typeof window !== 'undefined'",
        "typeof window !== 'undefined'"
    );

    test!(
        ::swc_ecma_parser::Syntax::default(),
        |_| TypeOfSymbol,
        dont_touch_non_symbol_comparison_02,
        "'undefined' !== typeof window",
        "'undefined' !== typeof window"
    );
}