use std::collections::HashMap;
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};

#[cfg(test)]
use serde_json::json;

/// Cached ingest response with expiry
#[derive(Clone, Debug)]
struct CachedResponse {
    response: serde_json::Value,
    inserted_at: Instant,
    ttl: Duration,
}

impl CachedResponse {
    fn is_expired(&self) -> bool {
        self.inserted_at.elapsed() > self.ttl
    }
}

/// Idempotency store for ingest operations
pub struct IdempotencyStore {
    cache: Arc<Mutex<HashMap<String, CachedResponse>>>,
    ttl: Duration,
}

impl IdempotencyStore {
    pub fn new(ttl_seconds: u64) -> Self {
        Self {
            cache: Arc::new(Mutex::new(HashMap::new())),
            ttl: Duration::from_secs(ttl_seconds),
        }
    }

    /// Get cached response for ingest_id. Returns None if not found or expired.
    pub fn get(&self, ingest_id: &str) -> Option<serde_json::Value> {
        let mut cache = self.cache.lock().unwrap();
        
        if let Some(cached) = cache.get(ingest_id) {
            if !cached.is_expired() {
                return Some(cached.response.clone());
            }
        }

        // Clean up expired entry
        cache.remove(ingest_id);
        None
    }

    /// Store response for ingest_id
    pub fn set(&self, ingest_id: String, response: serde_json::Value) {
        let mut cache = self.cache.lock().unwrap();
        cache.insert(
            ingest_id,
            CachedResponse {
                response,
                inserted_at: Instant::now(),
                ttl: self.ttl,
            },
        );
    }

    /// Evict expired entries (background maintenance)
    pub fn evict_expired(&self) {
        let mut cache = self.cache.lock().unwrap();
        cache.retain(|_, v| !v.is_expired());
    }

    /// Clear all entries (for testing)
    #[cfg(test)]
    pub fn clear(&self) {
        let mut cache = self.cache.lock().unwrap();
        cache.clear();
    }

    /// Get cache size (for testing)
    #[cfg(test)]
    pub fn len(&self) -> usize {
        let cache = self.cache.lock().unwrap();
        cache.len()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_idempotency_store_basic() {
        let store = IdempotencyStore::new(60);
        let response = json!({"ingest_id": "test-123", "status": "pending"});

        store.set("test-123".to_string(), response.clone());
        assert_eq!(store.get("test-123"), Some(response));
    }

    #[test]
    fn test_idempotency_store_expiry() {
        let store = IdempotencyStore::new(0);
        let response = json!({"ingest_id": "test-123", "status": "pending"});

        store.set("test-123".to_string(), response);
        std::thread::sleep(Duration::from_millis(10));

        assert_eq!(store.get("test-123"), None);
    }

    #[test]
    fn test_idempotency_missing_key() {
        let store = IdempotencyStore::new(60);
        assert_eq!(store.get("nonexistent"), None);
    }

    #[test]
    fn test_idempotency_evict_expired() {
        let store = IdempotencyStore::new(1);
        store.set("key1".to_string(), json!({"data": "value1"}));
        store.set("key2".to_string(), json!({"data": "value2"}));

        assert_eq!(store.len(), 2);

        std::thread::sleep(Duration::from_secs(1));
        std::thread::sleep(Duration::from_millis(100));

        store.evict_expired();
        assert_eq!(store.len(), 0);
    }
}