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

use moka::future::{Cache, CacheBuilder};
use serde::{Serialize, de::DeserializeOwned};

use crate::{CacheError, CacheResult};

const DEFAULT_LOCAL_MAX_CAPACITY: u64 = 10_000;

#[derive(Clone, Debug)]
pub struct LocalCacheConfig {
    pub max_capacity: u64,
    pub time_to_live: Option<Duration>,
    pub time_to_idle: Option<Duration>,
}

impl Default for LocalCacheConfig {
    fn default() -> Self {
        Self {
            max_capacity: DEFAULT_LOCAL_MAX_CAPACITY,
            time_to_live: Some(Duration::from_secs(300)),
            time_to_idle: None,
        }
    }
}

#[derive(Clone)]
pub struct MokaCache {
    pub inner: Cache<Arc<str>, Arc<[u8]>>,
}

impl MokaCache {
    pub fn init() -> Self {
        Self::with_config(LocalCacheConfig::default())
    }

    pub fn with_config(config: LocalCacheConfig) -> Self {
        let mut builder = CacheBuilder::new(config.max_capacity);
        if let Some(time_to_live) = config.time_to_live {
            builder = builder.time_to_live(time_to_live);
        }
        if let Some(time_to_idle) = config.time_to_idle {
            builder = builder.time_to_idle(time_to_idle);
        }

        Self {
            inner: builder.build(),
        }
    }

    pub async fn get<T>(&self, key: &str) -> CacheResult<Option<T>>
    where
        T: DeserializeOwned,
    {
        match self.inner.get(key).await {
            Some(value) => serde_json::from_slice(value.as_ref())
                .map(Some)
                .map_err(CacheError::Serialize),
            None => Ok(None),
        }
    }

    pub async fn get_json(
        &self,
        key: &str,
    ) -> CacheResult<Option<serde_json::Value>> {
        self.get(key).await
    }

    pub async fn set<T>(&self, key: &str, value: &T) -> CacheResult<()>
    where
        T: Serialize + ?Sized,
    {
        let value = serde_json::to_vec(value).map_err(CacheError::Serialize)?;
        self.inner
            .insert(Arc::<str>::from(key), Arc::<[u8]>::from(value))
            .await;
        Ok(())
    }

    pub async fn remove(&self, key: &str) {
        self.inner.remove(key).await;
    }

    pub async fn contains_key(&self, key: &str) -> bool {
        self.inner.contains_key(key)
    }

    pub async fn invalidate_all(&self) {
        self.inner.invalidate_all();
    }

    pub fn invalidate_entries_if<F>(&self, predicate: F)
    where
        F: Fn(&str) -> bool + Send + Sync + 'static,
    {
        let _ = self
            .inner
            .invalidate_entries_if(move |key, _| predicate(key));
    }
}

#[cfg(test)]
mod tests {
    use std::time::Duration;

    use serde::{Deserialize, Serialize};

    use super::{LocalCacheConfig, MokaCache};

    #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
    struct User {
        id: u64,
        name: String,
    }

    #[tokio::test]
    async fn stores_and_reads_typed_values() {
        let cache = MokaCache::init();
        let user = User {
            id: 7,
            name: "alice".to_string(),
        };

        cache.set("user:7", &user).await.unwrap();

        assert_eq!(cache.get::<User>("user:7").await.unwrap(), Some(user));
    }

    #[tokio::test]
    async fn expires_values_by_ttl() {
        let cache = MokaCache::with_config(LocalCacheConfig {
            max_capacity: 16,
            time_to_live: Some(Duration::from_millis(25)),
            time_to_idle: None,
        });

        cache.set("short", &"value").await.unwrap();
        tokio::time::sleep(Duration::from_millis(60)).await;

        assert_eq!(cache.get::<String>("short").await.unwrap(), None);
    }
}