//! Cache module providing flexible caching with Redis and in-memory backends.
//!
//! This module provides a unified caching interface with automatic fallback
//! from Redis to in-memory caching when Redis is unavailable.

mod in_memory;
mod redis;

use anyhow::Result;
use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use std::collections::HashSet;
use tracing::{info, warn};

pub use in_memory::InMemoryCache;
pub use redis::RedisCache;

/// Generic cache trait implemented by all cache backends.
///
/// Provides async methods for get, set, delete, and bulk operations.
#[async_trait]
pub trait Cache: Send + Sync {
    /// Get a value from cache, returning None if not found or expired.
    async fn get<T>(&mut self, key: &str) -> Result<Option<T>>
    where
        T: for<'de> Deserialize<'de> + Send;

    /// Set a value in cache with optional TTL in seconds.
    async fn set<T>(&mut self, key: &str, value: &T, ttl_seconds: Option<u64>) -> Result<()>
    where
        T: Serialize + Send + Sync;

    /// Delete a key from cache.
    async fn delete(&mut self, key: &str) -> Result<()>;

    /// Set multiple key-value pairs efficiently (uses pipelining for Redis).
    async fn set_multiple<T>(&mut self, items: Vec<(&str, &T, Option<u64>)>) -> Result<()>
    where
        T: Serialize + Send + Sync;

    /// Test cache connection/health.
    async fn ping(&mut self) -> Result<bool>;

    /// Get cache info/statistics for monitoring.
    async fn get_info(&mut self) -> Result<String>;
}

/// Cache backend implementation enum to avoid trait object overhead.
pub enum CacheBackendImpl {
    InMemory(InMemoryCache),
    Redis(RedisCache),
}

impl CacheBackendImpl {
    pub async fn get<T>(&mut self, key: &str) -> Result<Option<T>>
    where
        T: for<'de> Deserialize<'de> + Send,
    {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.get(key).await,
            CacheBackendImpl::Redis(cache) => cache.get(key).await,
        }
    }

    pub async fn set<T>(&mut self, key: &str, value: &T, ttl_seconds: Option<u64>) -> Result<()>
    where
        T: Serialize + Send + Sync,
    {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.set(key, value, ttl_seconds).await,
            CacheBackendImpl::Redis(cache) => cache.set(key, value, ttl_seconds).await,
        }
    }

    pub async fn delete(&mut self, key: &str) -> Result<()> {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.delete(key).await,
            CacheBackendImpl::Redis(cache) => cache.delete(key).await,
        }
    }

    pub async fn set_multiple<T>(&mut self, items: Vec<(&str, &T, Option<u64>)>) -> Result<()>
    where
        T: Serialize + Send + Sync,
    {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.set_multiple(items).await,
            CacheBackendImpl::Redis(cache) => cache.set_multiple(items).await,
        }
    }

    pub async fn ping(&mut self) -> Result<bool> {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.ping().await,
            CacheBackendImpl::Redis(cache) => cache.ping().await,
        }
    }

    pub async fn get_info(&mut self) -> Result<String> {
        match self {
            CacheBackendImpl::InMemory(cache) => cache.get_info().await,
            CacheBackendImpl::Redis(cache) => cache.get_info().await,
        }
    }
}

/// Domain-specific cache wrapper with convenience methods for Slices operations.
///
/// Provides typed methods for actors, lexicons, domains, collections, auth, and DID resolution.
pub struct SliceCache {
    cache: CacheBackendImpl,
}

impl SliceCache {
    pub fn new(cache: CacheBackendImpl) -> Self {
        Self { cache }
    }

    /// Actor cache methods (permanent cache - no TTL)
    pub async fn is_actor(&mut self, did: &str, slice_uri: &str) -> Result<Option<bool>> {
        let key = format!("actor:{}:{}", did, slice_uri);
        self.cache.get::<bool>(&key).await
    }

    pub async fn cache_actor_exists(&mut self, did: &str, slice_uri: &str) -> Result<()> {
        let key = format!("actor:{}:{}", did, slice_uri);
        self.cache.set(&key, &true, None).await
    }

    pub async fn remove_actor(&mut self, did: &str, slice_uri: &str) -> Result<()> {
        let key = format!("actor:{}:{}", did, slice_uri);
        self.cache.delete(&key).await
    }

    pub async fn preload_actors(&mut self, actors: Vec<(String, String)>) -> Result<()> {
        if actors.is_empty() {
            return Ok(());
        }

        let items: Vec<(String, bool, Option<u64>)> = actors
            .into_iter()
            .map(|(did, slice_uri)| (format!("actor:{}:{}", did, slice_uri), true, None))
            .collect();

        let items_ref: Vec<(&str, &bool, Option<u64>)> = items
            .iter()
            .map(|(key, value, ttl)| (key.as_str(), value, *ttl))
            .collect();

        self.cache.set_multiple(items_ref).await
    }

    /// Lexicon cache methods (2 hour TTL)
    pub async fn cache_lexicons(
        &mut self,
        slice_uri: &str,
        lexicons: &Vec<serde_json::Value>,
    ) -> Result<()> {
        let key = format!("lexicons:{}", slice_uri);
        self.cache.set(&key, lexicons, Some(7200)).await
    }

    pub async fn get_lexicons(
        &mut self,
        slice_uri: &str,
    ) -> Result<Option<Vec<serde_json::Value>>> {
        let key = format!("lexicons:{}", slice_uri);
        self.cache.get::<Vec<serde_json::Value>>(&key).await
    }

    /// Domain cache methods (4 hour TTL)
    pub async fn cache_slice_domain(&mut self, slice_uri: &str, domain: &str) -> Result<()> {
        let key = format!("domain:{}", slice_uri);
        self.cache.set(&key, &domain.to_string(), Some(14400)).await
    }

    pub async fn get_slice_domain(&mut self, slice_uri: &str) -> Result<Option<String>> {
        let key = format!("domain:{}", slice_uri);
        self.cache.get::<String>(&key).await
    }

    /// Collections cache methods (2 hour TTL)
    pub async fn cache_slice_collections(
        &mut self,
        slice_uri: &str,
        collections: &HashSet<String>,
    ) -> Result<()> {
        let key = format!("collections:{}", slice_uri);
        self.cache.set(&key, collections, Some(7200)).await
    }

    pub async fn get_slice_collections(
        &mut self,
        slice_uri: &str,
    ) -> Result<Option<HashSet<String>>> {
        let key = format!("collections:{}", slice_uri);
        self.cache.get::<HashSet<String>>(&key).await
    }

    /// Auth cache methods (5 minute TTL)
    pub async fn get_cached_oauth_userinfo(
        &mut self,
        token: &str,
    ) -> Result<Option<serde_json::Value>> {
        let key = format!("oauth_userinfo:{}", token);
        self.cache.get(&key).await
    }

    pub async fn cache_oauth_userinfo(
        &mut self,
        token: &str,
        userinfo: &serde_json::Value,
        ttl_seconds: u64,
    ) -> Result<()> {
        let key = format!("oauth_userinfo:{}", token);
        self.cache.set(&key, userinfo, Some(ttl_seconds)).await
    }

    pub async fn get_cached_atproto_session(
        &mut self,
        token: &str,
    ) -> Result<Option<serde_json::Value>> {
        let key = format!("atproto_session:{}", token);
        self.cache.get(&key).await
    }

    pub async fn cache_atproto_session(
        &mut self,
        token: &str,
        session: &serde_json::Value,
        ttl_seconds: u64,
    ) -> Result<()> {
        let key = format!("atproto_session:{}", token);
        self.cache.set(&key, session, Some(ttl_seconds)).await
    }

    /// DID resolution cache methods (24 hour TTL)
    pub async fn get_cached_did_resolution(
        &mut self,
        did: &str,
    ) -> Result<Option<serde_json::Value>> {
        let key = format!("did_resolution:{}", did);
        self.cache.get(&key).await
    }

    pub async fn cache_did_resolution(
        &mut self,
        did: &str,
        actor_data: &serde_json::Value,
    ) -> Result<()> {
        let key = format!("did_resolution:{}", did);
        self.cache.set(&key, actor_data, Some(86400)).await
    }

    pub async fn invalidate_did_resolution(&mut self, did: &str) -> Result<()> {
        let key = format!("did_resolution:{}", did);
        self.cache.delete(&key).await
    }

    /// Generic get/set for custom caching needs
    pub async fn get<T>(&mut self, key: &str) -> Result<Option<T>>
    where
        T: for<'de> Deserialize<'de> + Send,
    {
        self.cache.get(key).await
    }

    pub async fn set<T>(&mut self, key: &str, value: &T, ttl_seconds: Option<u64>) -> Result<()>
    where
        T: Serialize + Send + Sync,
    {
        self.cache.set(key, value, ttl_seconds).await
    }

    /// Utility methods
    pub async fn ping(&mut self) -> Result<bool> {
        self.cache.ping().await
    }

    pub async fn get_info(&mut self) -> Result<String> {
        self.cache.get_info().await
    }
}

/// Cache backend configuration enum.
#[derive(Debug, Clone)]
pub enum CacheBackend {
    InMemory {
        ttl_seconds: Option<u64>,
    },
    Redis {
        url: String,
        ttl_seconds: Option<u64>,
    },
}

/// Factory for creating cache instances with automatic Redis fallback.
pub struct CacheFactory;

impl CacheFactory {
    /// Create a cache backend, falling back to in-memory if Redis fails.
    pub async fn create_cache(backend: CacheBackend) -> Result<CacheBackendImpl> {
        match backend {
            CacheBackend::InMemory { ttl_seconds } => {
                let ttl_display = ttl_seconds
                    .map(|t| format!("{}s", t))
                    .unwrap_or_else(|| "default".to_string());
                info!("Creating in-memory cache with TTL: {}", ttl_display);
                Ok(CacheBackendImpl::InMemory(InMemoryCache::new(ttl_seconds)))
            }
            CacheBackend::Redis { url, ttl_seconds } => {
                info!("Attempting to create Redis cache at: {}", url);
                match RedisCache::new(&url, ttl_seconds).await {
                    Ok(redis_cache) => {
                        info!("Created Redis cache successfully");
                        Ok(CacheBackendImpl::Redis(redis_cache))
                    }
                    Err(e) => {
                        warn!(
                            error = ?e,
                            "Failed to create Redis cache, falling back to in-memory"
                        );
                        Ok(CacheBackendImpl::InMemory(InMemoryCache::new(ttl_seconds)))
                    }
                }
            }
        }
    }

    /// Create a SliceCache with the specified backend.
    pub async fn create_slice_cache(backend: CacheBackend) -> Result<SliceCache> {
        let cache = Self::create_cache(backend).await?;
        Ok(SliceCache::new(cache))
    }
}