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    use std::{borrow::Cow, sync::Arc, time::Duration};

    #[cfg(feature = "session")]
    use actix_session::SessionExt as _;
    use actix_web::dev::ServiceRequest;
    use redis::Client;

    use crate::{errors::Error, GetArcBoxKeyFn, Limiter};

    /// Rate limiter builder.
    #[derive(Debug)]
    pub struct Builder {
        pub(crate) redis_url: String,
        pub(crate) limit: usize,
        pub(crate) period: Duration,
        pub(crate) get_key_fn: Option<GetArcBoxKeyFn>,
        pub(crate) cookie_name: Cow<'static, str>,
        #[cfg(feature = "session")]
        pub(crate) session_key: Cow<'static, str>,
    }

    impl Builder {
        /// Set upper limit.
        pub fn limit(&mut self, limit: usize) -> &mut Self {
            self.limit = limit;
            self
        }

        /// Set limit window/period.
        pub fn period(&mut self, period: Duration) -> &mut Self {
            self.period = period;
            self
        }

        /// Sets rate limit key derivation function.
        ///
        /// Should not be used in combination with `cookie_name` or `session_key` as they conflict.
        pub fn key_by<F>(&mut self, resolver: F) -> &mut Self
        where
            F: Fn(&ServiceRequest) -> Option<String> + Send + Sync + 'static,
        {
            self.get_key_fn = Some(Arc::new(resolver));
            self
        }

        /// Sets name of cookie to be sent.
        ///
        /// This method should not be used in combination of `key_by` as they conflict.
        #[deprecated = "Prefer `key_by`."]
        pub fn cookie_name(&mut self, cookie_name: impl Into<Cow<'static, str>>) -> &mut Self {
            if self.get_key_fn.is_some() {
                panic!("This method should not be used in combination of get_key as they overwrite each other")
            }
            self.cookie_name = cookie_name.into();
            self
        }

        /// Sets session key to be used in backend.
        ///
        /// This method should not be used in combination of `key_by` as they conflict.
        #[deprecated = "Prefer `key_by`."]
        #[cfg(feature = "session")]
        pub fn session_key(&mut self, session_key: impl Into<Cow<'static, str>>) -> &mut Self {
            if self.get_key_fn.is_some() {
                panic!("This method should not be used in combination of get_key as they overwrite each other")
            }
            self.session_key = session_key.into();
            self
        }

        /// Finalizes and returns a `Limiter`.
        ///
        /// Note that this method will connect to the Redis server to test its connection which is a
        /// **synchronous** operation.
        pub fn build(&mut self) -> Result<Limiter, Error> {
            let get_key = if let Some(resolver) = self.get_key_fn.clone() {
                resolver
            } else {
                let cookie_name = self.cookie_name.clone();

                #[cfg(feature = "session")]
                let session_key = self.session_key.clone();

                let closure: GetArcBoxKeyFn = Arc::new(Box::new(move |req: &ServiceRequest| {
                    #[cfg(feature = "session")]
                    let res = req
                        .get_session()
                        .get(&session_key)
                        .unwrap_or_else(|_| req.cookie(&cookie_name).map(|c| c.to_string()));

                    #[cfg(not(feature = "session"))]
                    let res = req.cookie(&cookie_name).map(|c| c.to_string());

                    res
                }));
                closure
            };

            Ok(Limiter {
                client: Client::open(self.redis_url.as_str())?,
                limit: self.limit,
                period: self.period,
                get_key_fn: get_key,
            })
        }
    }

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

        #[test]
        fn test_create_builder() {
            let redis_url = "redis://127.0.0.1";
            let period = Duration::from_secs(10);
            let builder = Builder {
                redis_url: redis_url.to_owned(),
                limit: 100,
                period,
                get_key_fn: Some(Arc::new(|_| None)),
                cookie_name: Cow::Owned("session".to_string()),
                #[cfg(feature = "session")]
                session_key: Cow::Owned("rate-api".to_string()),
            };

            assert_eq!(builder.redis_url, redis_url);
            assert_eq!(builder.limit, 100);
            assert_eq!(builder.period, period);
            #[cfg(feature = "session")]
            assert_eq!(builder.session_key, "rate-api");
            assert_eq!(builder.cookie_name, "session");
        }

        #[test]
        fn test_create_limiter() {
            let redis_url = "redis://127.0.0.1";
            let period = Duration::from_secs(20);
            let mut builder = Builder {
                redis_url: redis_url.to_owned(),
                limit: 100,
                period: Duration::from_secs(10),
                get_key_fn: Some(Arc::new(|_| None)),
                cookie_name: Cow::Borrowed("sid"),
                #[cfg(feature = "session")]
                session_key: Cow::Borrowed("key"),
            };

            let limiter = builder.limit(200).period(period).build().unwrap();

            assert_eq!(limiter.limit, 200);
            assert_eq!(limiter.period, period);
        }

        #[test]
        #[should_panic = "Redis URL did not parse"]
        fn test_create_limiter_error() {
            let redis_url = "127.0.0.1";
            let period = Duration::from_secs(20);
            let mut builder = Builder {
                redis_url: redis_url.to_owned(),
                limit: 100,
                period: Duration::from_secs(10),
                get_key_fn: Some(Arc::new(|_| None)),
                cookie_name: Cow::Borrowed("sid"),
                #[cfg(feature = "session")]
                session_key: Cow::Borrowed("key"),
            };

            builder.limit(200).period(period).build().unwrap();
        }
    }