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use swc_atoms::JsWord;
use swc_common::DUMMY_SP;
use swc_ecma_ast::*;
use swc_ecma_transforms_base::perf::Parallel;
use swc_ecma_transforms_macros::parallel;
use swc_ecma_utils::{quote_ident, ExprFactory};
use swc_ecma_visit::{as_folder, noop_visit_mut_type, Fold, VisitMut, VisitMutWith};

/// Compile ES2015 sticky regex to an ES5 RegExp constructor
///
///# Example
///## In
///
/// ```js
/// /o+/y;
/// ```
///
///## Out
///
/// ```js
/// new RegExp("o+", "y")
/// ```
pub fn sticky_regex() -> impl 'static + Fold + VisitMut {
    as_folder(StickyRegex)
}

struct StickyRegex;

impl Parallel for StickyRegex {
    fn merge(&mut self, _: Self) {}

    fn create(&self) -> Self {
        StickyRegex
    }
}

#[parallel]
impl VisitMut for StickyRegex {
    noop_visit_mut_type!();

    fn visit_mut_expr(&mut self, e: &mut Expr) {
        e.visit_mut_children_with(self);

        match e {
            Expr::Lit(Lit::Regex(Regex { exp, flags, span })) => {
                if flags.contains('y') {
                    let str_lit = |s: JsWord| {
                        Box::new(Expr::Lit(Lit::Str(Str {
                            span: DUMMY_SP,
                            value: s,
                            has_escape: false,
                            kind: StrKind::Normal {
                                contains_quote: false,
                            },
                        })))
                    };

                    *e = Expr::New(NewExpr {
                        span: *span,
                        callee: Box::new(quote_ident!(*span, "RegExp").into()),
                        args: Some(vec![
                            str_lit(exp.clone()).as_arg(),
                            str_lit(flags.clone()).as_arg(),
                        ]),
                        type_args: Default::default(),
                    })
                }
            }
            _ => {}
        }
    }
}

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

    test!(
        ::swc_ecma_parser::Syntax::default(),
        |_| sticky_regex(),
        babel_basic,
        "var re = /o+/y;",
        "var re = new RegExp('o+', 'y');"
    );

    test!(
        ::swc_ecma_parser::Syntax::default(),
        |_| sticky_regex(),
        babel_ignore_non_sticky,
        "var re = /o+/;",
        "var re = /o+/;"
    );
}