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

use actix_web::cookie::time::Duration;
use redis::{
    cluster::{ClusterClient, ClusterClientBuilder},
    cluster_async::ClusterConnection,
};
use tokio::sync::Mutex;

use super::SessionKey;
use crate::storage::{
    SessionStore,
    format::{deserialize_session_state, serialize_session_state},
    interface::{LoadError, SaveError, SessionState, UpdateError},
    utils::generate_session_key,
};

#[derive(Clone)]
pub struct RedisClusterSessionStore {
    client: ClusterClient,
    connection: Arc<Mutex<ClusterConnection>>,
    configuration: CacheConfiguration,
}

#[derive(Clone)]
struct CacheConfiguration {
    cache_keygen: Arc<dyn Fn(&str) -> String + Send + Sync>,
}

impl Default for CacheConfiguration {
    fn default() -> Self {
        Self {
            cache_keygen: Arc::new(str::to_owned),
        }
    }
}

impl RedisClusterSessionStore {
    const DEFAULT_CONNECTION_TIMEOUT: StdDuration = StdDuration::from_secs(2);
    const DEFAULT_RESPONSE_TIMEOUT: StdDuration = StdDuration::from_secs(2);
    const DEFAULT_COMMAND_TIMEOUT: StdDuration = StdDuration::from_secs(3);
    const DEFAULT_RETRIES: u32 = 1;
    const DEFAULT_RETRY_MIN_WAIT_MS: u64 = 25;
    const DEFAULT_RETRY_MAX_WAIT_MS: u64 = 100;
    const DEFAULT_RETRY_FACTOR: u64 = 10;
    const DEFAULT_RETRY_EXPONENT_BASE: u64 = 2;

    pub fn builder(
        connection_strings: Vec<String>,
    ) -> RedisClusterSessionStoreBuilder {
        RedisClusterSessionStoreBuilder {
            configuration: CacheConfiguration::default(),
            connection_strings,
        }
    }

    pub async fn new(
        connection_strings: Vec<String>,
    ) -> anyhow::Result<RedisClusterSessionStore> {
        Self::builder(connection_strings).build().await
    }

    fn client_builder(connection_strings: Vec<String>) -> ClusterClientBuilder {
        ClusterClient::builder(connection_strings)
            .connection_timeout(Self::DEFAULT_CONNECTION_TIMEOUT)
            .response_timeout(Self::DEFAULT_RESPONSE_TIMEOUT)
            .retries(Self::DEFAULT_RETRIES)
            .min_retry_wait(Self::DEFAULT_RETRY_MIN_WAIT_MS)
            .max_retry_wait(Self::DEFAULT_RETRY_MAX_WAIT_MS)
            .retry_wait_formula(
                Self::DEFAULT_RETRY_FACTOR,
                Self::DEFAULT_RETRY_EXPONENT_BASE,
            )
    }

    async fn connect(
        client: &ClusterClient,
    ) -> anyhow::Result<ClusterConnection> {
        let started = std::time::Instant::now();
        let connection = tokio::time::timeout(
            Self::DEFAULT_COMMAND_TIMEOUT,
            client.get_async_connection(),
        )
        .await
        .map_err(|_| anyhow::anyhow!("session redis async connect timed out"))?
        .map_err(|e| anyhow::anyhow!(e))?;

        tracing::debug!(
            elapsed_ms = started.elapsed().as_millis() as u64,
            "session redis async connect finished"
        );
        Ok(connection)
    }

    async fn execute_cmd<T, F>(
        &self,
        op_name: &'static str,
        make_cmd: F,
    ) -> anyhow::Result<T>
    where
        T: redis::FromRedisValue,
        F: Fn() -> redis::Cmd,
    {
        let first_try: anyhow::Result<T> = {
            let mut connection = self.connection.lock().await;
            let started = std::time::Instant::now();
            tracing::debug!(op = op_name, "session redis command start");
            match tokio::time::timeout(
                Self::DEFAULT_COMMAND_TIMEOUT,
                make_cmd().query_async(&mut *connection),
            )
            .await
            .map_err(|_| anyhow::anyhow!("session redis command timed out"))?
            {
                Ok(value) => {
                    tracing::debug!(
                        op = op_name,
                        elapsed_ms = started.elapsed().as_millis() as u64,
                        "session redis command finished"
                    );
                    return Ok(value);
                }
                Err(err) => Err(anyhow::anyhow!(err)),
            }
        };

        if let Err(error) = &first_try {
            tracing::warn!(op = op_name, error = %error, "session redis command failed, reconnecting");
        }

        let new_connection = Self::connect(&self.client).await?;
        {
            let mut connection = self.connection.lock().await;
            *connection = new_connection;
        }

        let mut connection = self.connection.lock().await;
        let started = std::time::Instant::now();
        tracing::debug!(op = op_name, "session redis command retry start");
        let result = tokio::time::timeout(
            Self::DEFAULT_COMMAND_TIMEOUT,
            make_cmd().query_async(&mut *connection),
        )
        .await
        .map_err(|_| anyhow::anyhow!("session redis command retry timed out"))?
        .map_err(|e| anyhow::anyhow!(e))?;
        tracing::debug!(
            op = op_name,
            elapsed_ms = started.elapsed().as_millis() as u64,
            "session redis command retry finished"
        );
        Ok(result)
    }

    fn ttl_seconds(ttl: &Duration) -> anyhow::Result<u64> {
        let ttl_secs = ttl.whole_seconds();
        if ttl_secs <= 0 {
            anyhow::bail!("session TTL must be positive");
        }
        u64::try_from(ttl_secs).map_err(anyhow::Error::new)
    }
}

#[must_use]
pub struct RedisClusterSessionStoreBuilder {
    configuration: CacheConfiguration,
    connection_strings: Vec<String>,
}

impl RedisClusterSessionStoreBuilder {
    pub fn cache_keygen<F>(mut self, keygen: F) -> Self
    where
        F: Fn(&str) -> String + 'static + Send + Sync,
    {
        self.configuration.cache_keygen = Arc::new(keygen);
        self
    }

    pub async fn build(self) -> anyhow::Result<RedisClusterSessionStore> {
        let client =
            RedisClusterSessionStore::client_builder(self.connection_strings)
                .build()?;
        let connection = RedisClusterSessionStore::connect(&client).await?;

        Ok(RedisClusterSessionStore {
            client,
            connection: Arc::new(Mutex::new(connection)),
            configuration: self.configuration,
        })
    }
}

impl SessionStore for RedisClusterSessionStore {
    async fn load(
        &self,
        session_key: &SessionKey,
    ) -> Result<Option<SessionState>, LoadError> {
        let cache_key =
            self.configuration.cache_keygen.as_ref()(session_key.as_ref());
        let value: Option<String> = self
            .execute_cmd("get", move || {
                let mut cmd = redis::cmd("GET");
                cmd.arg(&cache_key);
                cmd
            })
            .await
            .map_err(LoadError::Other)?;

        match value {
            None => Ok(None),
            Some(value) => Ok(Some(
                deserialize_session_state(&value)
                    .map_err(LoadError::Deserialization)?,
            )),
        }
    }

    async fn save(
        &self,
        session_state: SessionState,
        ttl: &Duration,
    ) -> Result<SessionKey, SaveError> {
        let body = serialize_session_state(&session_state)
            .map_err(SaveError::Serialization)?;
        let session_key = generate_session_key();
        let cache_key =
            self.configuration.cache_keygen.as_ref()(session_key.as_ref());
        let ttl_secs = Self::ttl_seconds(ttl).map_err(SaveError::Other)?;

        self.execute_cmd::<(), _>("set_ex", move || {
            let mut cmd = redis::cmd("SETEX");
            cmd.arg(&cache_key).arg(ttl_secs).arg(&body);
            cmd
        })
        .await
        .map_err(SaveError::Other)?;

        Ok(session_key)
    }

    async fn update(
        &self,
        session_key: SessionKey,
        session_state: SessionState,
        ttl: &Duration,
    ) -> Result<SessionKey, UpdateError> {
        let body = serialize_session_state(&session_state)
            .map_err(UpdateError::Serialization)?;
        let cache_key =
            self.configuration.cache_keygen.as_ref()(session_key.as_ref());
        let ttl_secs = Self::ttl_seconds(ttl).map_err(UpdateError::Other)?;

        self.execute_cmd::<(), _>("set_ex", move || {
            let mut cmd = redis::cmd("SETEX");
            cmd.arg(&cache_key).arg(ttl_secs).arg(&body);
            cmd
        })
        .await
        .map_err(UpdateError::Other)?;

        Ok(session_key)
    }

    async fn update_ttl(
        &self,
        session_key: &SessionKey,
        ttl: &Duration,
    ) -> anyhow::Result<()> {
        let cache_key =
            self.configuration.cache_keygen.as_ref()(session_key.as_ref());
        let ttl_secs = Self::ttl_seconds(ttl)?;

        self.execute_cmd("expire", move || {
            let mut cmd = redis::cmd("EXPIRE");
            cmd.arg(&cache_key).arg(ttl_secs);
            cmd
        })
        .await
        .map(|_: bool| ())
    }

    async fn delete(
        &self,
        session_key: &SessionKey,
    ) -> Result<(), anyhow::Error> {
        let cache_key =
            self.configuration.cache_keygen.as_ref()(session_key.as_ref());

        self.execute_cmd("del", move || {
            let mut cmd = redis::cmd("DEL");
            cmd.arg(&cache_key);
            cmd
        })
        .await
        .map(|_: i64| ())
    }
}