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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/>.
     */
    //! module describing mCaptcha system
    use actix::dev::*;
    use derive_builder::Builder;
    use pow_sha256::{Config, PoW};

    use crate::cache::messages;
    use crate::cache::Save;
    use crate::errors::*;
    use crate::master::Master;
    use crate::pow::*;

    /// struct describing various bits of data required for an mCaptcha system
    #[derive(Clone, Builder)]
    pub struct System<T: Save> {
        pub master: Addr<Master>,
        cache: Addr<T>,
        pow: Config,
    }

    impl<T> System<T>
    where
        T: Save,
        <T as actix::Actor>::Context: ToEnvelope<T, messages::Cache> + ToEnvelope<T, messages::Retrive>,
    {
        /// utility function to get difficulty factor of site `id` and cache it
        pub async fn get_pow(&self, id: String) -> Option<PoWConfig> {
            use crate::cache::messages::Cache;
            use crate::master::GetSite;
            use crate::mcaptcha::AddVisitor;

            let site_addr = self.master.send(GetSite(id)).await.unwrap();
            if site_addr.is_none() {
                return None;
            }
            let mcaptcha = site_addr.unwrap().send(AddVisitor).await.unwrap();
            let pow_config = PoWConfig::new(mcaptcha.difficulty_factor);

            let cache_msg = Cache::new(&pow_config, &mcaptcha);
            self.cache.send(cache_msg).await.unwrap().unwrap();
            Some(pow_config)
        }

        /// utility function to verify [Work]
        pub async fn verify_pow(&self, work: Work) -> CaptchaResult<bool> {
            use crate::cache::messages::Retrive;

            let string = work.string.clone();
            let msg = Retrive(string.clone());
            let pow: PoW<String> = work.into();

            let difficulty = self.cache.send(msg).await.unwrap()?;
            match difficulty {
                Some(difficulty) => {
                    if self.pow.is_sufficient_difficulty(&pow, difficulty) {
                        Ok(self.pow.is_valid_proof(&pow, &string))
                    } else {
                        Err(CaptchaError::InsuffiencientDifficulty)
                    }
                }
                None => Err(CaptchaError::StringNotFound),
            }
        }
    }

    #[cfg(test)]
    mod tests {

        use pow_sha256::ConfigBuilder;

        use super::System;
        use super::*;
        use crate::cache::HashCache;
        use crate::master::*;
        use crate::mcaptcha::tests::*;

        const MCAPTCHA_NAME: &str = "batsense.net";

        async fn boostrap_system(gc: u64) -> System<HashCache> {
            let master = Master::new(gc).start();
            let mcaptcha = get_counter().start();
            let pow = get_config();

            let cache = HashCache::default().start();
            let msg = AddSiteBuilder::default()
                .id(MCAPTCHA_NAME.into())
                .addr(mcaptcha.clone())
                .build()
                .unwrap();

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

            SystemBuilder::default()
                .master(master)
                .cache(cache)
                .pow(pow)
                .build()
                .unwrap()
        }

        fn get_config() -> Config {
            ConfigBuilder::default()
                .salt("myrandomsaltisnotlongenoug".into())
                .build()
                .unwrap()
        }

        #[actix_rt::test]
        async fn get_pow_works() {
            let actors = boostrap_system(10).await;
            let pow = actors.get_pow(MCAPTCHA_NAME.into()).await.unwrap();
            assert_eq!(pow.difficulty_factor, LEVEL_1.0);
        }

        #[actix_rt::test]
        async fn verify_pow_works() {
            let actors = boostrap_system(10).await;
            let work_req = actors.get_pow(MCAPTCHA_NAME.into()).await.unwrap();
            let config = get_config();

            let work = config
                .prove_work(&work_req.string, work_req.difficulty_factor)
                .unwrap();
            let mut payload = Work {
                string: work_req.string,
                result: work.result,
                nonce: work.nonce,
            };

            let res = actors.verify_pow(payload.clone()).await.unwrap();
            assert!(res);

            payload.string = "wrongstring".into();
            let res = actors.verify_pow(payload.clone()).await;
            assert_eq!(res, Err(CaptchaError::StringNotFound));

            let insufficient_work_req = actors.get_pow(MCAPTCHA_NAME.into()).await.unwrap();
            let insufficient_work = config.prove_work(&insufficient_work_req.string, 1).unwrap();
            let insufficient_work_payload = Work {
                string: insufficient_work_req.string,
                result: insufficient_work.result,
                nonce: insufficient_work.nonce,
            };
            let res = actors.verify_pow(insufficient_work_payload.clone()).await;
            assert_eq!(res, Err(CaptchaError::InsuffiencientDifficulty));
        }
    }