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    /*
     * mCaptcha - A proof of work based DoS protection system
     * Copyright © 2021 Aravinth Manivannan <realravinth@batsense.net>
     *
     * This program is free software: you can redistribute it and/or modify
     * it under the terms of the GNU Affero General Public License as
     * published by the Free Software Foundation, either version 3 of the
     * License, or (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU Affero General Public License for more details.
     *
     * You should have received a copy of the GNU Affero General Public License
     * along with this program.  If not, see <http://www.gnu.org/licenses/>.
     */
    //! In-memory cache implementation that uses [HashMap]
    use std::collections::HashMap;

    use actix::prelude::*;

    use super::messages::*;
    use super::Save;
    use crate::errors::*;

    #[derive(Clone, Default)]
    /// cache datastructure implementing [Save]
    pub struct HashCache(HashMap<String, u32>);

    impl HashCache {
        // save [PoWConfig] to cache
        fn save(&mut self, config: Cache) -> CaptchaResult<()> {
            self.0.insert(config.string, config.difficulty_factor);
            Ok(())
        }

        // retrive [PoWConfig] from cache. Deletes config post retrival
        fn retrive(&mut self, string: String) -> CaptchaResult<Option<u32>> {
            if let Some(difficulty_factor) = self.remove(&string) {
                Ok(Some(difficulty_factor.to_owned()))
            } else {
                Ok(None)
            }
        }

        // delete [PoWConfig] from cache
        fn remove(&mut self, string: &str) -> Option<u32> {
            self.0.remove(string)
        }
    }

    impl Save for HashCache {}

    impl Actor for HashCache {
        type Context = Context<Self>;
    }

    /// cache a PoWConfig
    impl Handler<Cache> for HashCache {
        type Result = MessageResult<Cache>;
        fn handle(&mut self, msg: Cache, ctx: &mut Self::Context) -> Self::Result {
            use actix::clock::sleep;
            use std::time::Duration;

            let addr = ctx.address();
            let del_msg = DeleteString(msg.string.clone());

            let duration: Duration = Duration::new(msg.duration.clone(), 0);
            let wait_for = async move {
                sleep(duration).await;
                addr.send(del_msg).await.unwrap().unwrap();
            }
            .into_actor(self);
            ctx.spawn(wait_for);

            MessageResult(self.save(msg))
        }
    }

    /// Delte a PoWConfig
    impl Handler<DeleteString> for HashCache {
        type Result = MessageResult<DeleteString>;
        fn handle(&mut self, msg: DeleteString, _ctx: &mut Self::Context) -> Self::Result {
            self.remove(&msg.0);
            MessageResult(Ok(()))
        }
    }

    /// Retrive PoW difficulty_factor for a PoW string
    impl Handler<Retrive> for HashCache {
        type Result = MessageResult<Retrive>;
        fn handle(&mut self, msg: Retrive, _ctx: &mut Self::Context) -> Self::Result {
            MessageResult(self.retrive(msg.0))
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;
        use crate::mcaptcha::AddVisitorResult;
        use crate::pow::PoWConfig;

        async fn sleep(time: u64) {
            use actix::clock::sleep;
            use std::time::Duration;

            let duration: Duration = Duration::new(time, 0);
            sleep(duration).await;
        }

        #[actix_rt::test]
        async fn hashcache_works() {
            const DIFFICULTY_FACTOR: u32 = 54;
            const DURATION: u64 = 5;
            let addr = HashCache::default().start();
            let pow: PoWConfig = PoWConfig::new(DIFFICULTY_FACTOR);
            let visitor_result = AddVisitorResult {
                difficulty_factor: DIFFICULTY_FACTOR,
                duration: DURATION,
            };
            let string = pow.string.clone();
            let msg = Cache::new(&pow, &visitor_result);

            addr.send(msg).await.unwrap().unwrap();

            let cache_difficulty_factor = addr.send(Retrive(string.clone())).await.unwrap().unwrap();
            assert_eq!(DIFFICULTY_FACTOR, cache_difficulty_factor.unwrap());

            sleep(DURATION + DURATION).await;

            let expired_string = addr.send(Retrive(string)).await.unwrap().unwrap();
            assert_eq!(None, expired_string);
        }
    }