mx-cache 0.1.0

//! Mock implementations for testing cache operations without external dependencies.
//!
//! This module provides mock implementations that can be used in tests to simulate
//! Redis behavior without requiring a live Redis server.

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

use crate::Cache;

/// Helper macro to check error mode and return an error if enabled.
/// Reduces boilerplate in mock implementations.
macro_rules! check_error_mode {
    ($error_mode:expr) => {{
        let guard = $error_mode.lock().unwrap();
        if let Some(ref msg) = *guard {
            return Err(anyhow::anyhow!("{}", msg));
        }
    }};
}

/// Entry in the mock cache with value and expiration time.
#[derive(Clone, Debug)]
struct MockEntry {
    value: Vec<u8>,
    expires_at: Option<Instant>,
}

impl MockEntry {
    fn is_expired(&self) -> bool {
        self.expires_at
            .map(|t| Instant::now() >= t)
            .unwrap_or(false)
    }
}

/// Mock cache implementation for testing purposes.
///
/// Provides an in-memory cache that mimics Redis behavior including:
/// - TTL expiration
/// - NX (not exists) semantics
/// - Error injection for testing error handling
///
/// # Example
///
/// ```
/// use mx_cache::mock::MockCache;
/// use mx_cache::Cache;
/// use std::time::Duration;
///
/// # tokio_test::block_on(async {
/// let cache = MockCache::new();
///
/// cache.set(b"key", b"value", Duration::from_secs(60)).await.unwrap();
/// let result = cache.get(b"key").await.unwrap();
/// assert_eq!(result, Some(b"value".to_vec()));
/// # });
/// ```
#[derive(Clone, Debug)]
pub struct MockCache {
    data: Arc<Mutex<HashMap<Vec<u8>, MockEntry>>>,
    /// When set, all operations will return this error message
    error_mode: Arc<Mutex<Option<String>>>,
    /// Count of operations performed (for verification in tests)
    operation_count: Arc<Mutex<OperationCounts>>,
}

/// Tracks operation counts for test verification.
#[derive(Clone, Debug, Default)]
pub struct OperationCounts {
    pub gets: usize,
    pub sets: usize,
    pub set_nx_px: usize,
    pub deletes: usize,
}

impl MockCache {
    /// Creates a new empty mock cache.
    pub fn new() -> Self {
        Self {
            data: Arc::new(Mutex::new(HashMap::new())),
            error_mode: Arc::new(Mutex::new(None)),
            operation_count: Arc::new(Mutex::new(OperationCounts::default())),
        }
    }

    /// Creates a mock cache with pre-populated data.
    ///
    /// # Arguments
    ///
    /// * `entries` - Iterator of (key, value) pairs to pre-populate
    pub fn with_data<I, K, V>(entries: I) -> Self
    where
        I: IntoIterator<Item = (K, V)>,
        K: AsRef<[u8]>,
        V: AsRef<[u8]>,
    {
        let cache = Self::new();
        {
            let mut data = cache.data.lock().unwrap();
            for (key, value) in entries {
                data.insert(
                    key.as_ref().to_vec(),
                    MockEntry {
                        value: value.as_ref().to_vec(),
                        expires_at: None,
                    },
                );
            }
        }
        cache
    }

    /// Enables error mode - all subsequent operations will fail with the given message.
    ///
    /// This is useful for testing error handling paths.
    pub fn enable_error_mode(&self, message: &str) {
        let mut error_mode = self.error_mode.lock().unwrap();
        *error_mode = Some(message.to_owned());
    }

    /// Disables error mode - operations will proceed normally.
    pub fn disable_error_mode(&self) {
        let mut error_mode = self.error_mode.lock().unwrap();
        *error_mode = None;
    }

    /// Returns the current operation counts.
    pub fn operation_counts(&self) -> OperationCounts {
        self.operation_count.lock().unwrap().clone()
    }

    /// Resets operation counts to zero.
    pub fn reset_counts(&self) {
        let mut counts = self.operation_count.lock().unwrap();
        *counts = OperationCounts::default();
    }

    /// Returns the number of non-expired entries in the cache.
    pub fn len(&self) -> usize {
        let data = self.data.lock().unwrap();
        data.values().filter(|e| !e.is_expired()).count()
    }

    /// Returns true if the cache has no non-expired entries.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Clears all entries from the cache.
    pub fn clear(&self) {
        let mut data = self.data.lock().unwrap();
        data.clear();
    }

    /// Manually expires an entry (for testing TTL behavior).
    pub fn force_expire(&self, key: &[u8]) {
        let mut data = self.data.lock().unwrap();
        if let Some(entry) = data.get_mut(&key.to_vec()) {
            entry.expires_at = Some(Instant::now() - Duration::from_secs(1));
        }
    }
}

impl Default for MockCache {
    fn default() -> Self {
        Self::new()
    }
}

impl Cache for MockCache {
    fn set_nx_px(
        &self,
        key: &[u8],
        value: &[u8],
        ttl: Duration,
    ) -> impl Future<Output = anyhow::Result<bool>> + Send {
        let key_vec = key.to_vec();
        let value_vec = value.to_vec();
        let data = Arc::clone(&self.data);
        let error_mode = Arc::clone(&self.error_mode);
        let operation_count = Arc::clone(&self.operation_count);

        async move {
            check_error_mode!(error_mode);
            operation_count.lock().unwrap().set_nx_px += 1;

            let mut data = data.lock().unwrap();

            // Check if key exists and is not expired
            if let Some(entry) = data.get(&key_vec)
                && !entry.is_expired()
            {
                return Ok(false);
            }

            // Insert new entry
            let expires_at = if ttl.is_zero() {
                Some(Instant::now())
            } else {
                Some(Instant::now() + ttl)
            };

            data.insert(
                key_vec,
                MockEntry {
                    value: value_vec,
                    expires_at,
                },
            );

            Ok(true)
        }
    }

    fn set(
        &self,
        key: &[u8],
        value: &[u8],
        ttl: Duration,
    ) -> impl Future<Output = anyhow::Result<()>> + Send {
        let key_vec = key.to_vec();
        let value_vec = value.to_vec();
        let data = Arc::clone(&self.data);
        let error_mode = Arc::clone(&self.error_mode);
        let operation_count = Arc::clone(&self.operation_count);

        async move {
            check_error_mode!(error_mode);
            operation_count.lock().unwrap().sets += 1;

            let expires_at = if ttl.is_zero() {
                Some(Instant::now())
            } else {
                Some(Instant::now() + ttl)
            };

            let mut data = data.lock().unwrap();
            data.insert(
                key_vec,
                MockEntry {
                    value: value_vec,
                    expires_at,
                },
            );

            Ok(())
        }
    }

    fn get(&self, key: &[u8]) -> impl Future<Output = anyhow::Result<Option<Vec<u8>>>> + Send {
        let key_vec = key.to_vec();
        let data = Arc::clone(&self.data);
        let error_mode = Arc::clone(&self.error_mode);
        let operation_count = Arc::clone(&self.operation_count);

        async move {
            check_error_mode!(error_mode);
            operation_count.lock().unwrap().gets += 1;

            let data = data.lock().unwrap();

            match data.get(&key_vec) {
                Some(entry) if !entry.is_expired() => Ok(Some(entry.value.clone())),
                _ => Ok(None),
            }
        }
    }

    fn del(&self, key: &[u8]) -> impl Future<Output = anyhow::Result<()>> + Send {
        let key_vec = key.to_vec();
        let data = Arc::clone(&self.data);
        let error_mode = Arc::clone(&self.error_mode);
        let operation_count = Arc::clone(&self.operation_count);

        async move {
            check_error_mode!(error_mode);
            operation_count.lock().unwrap().deletes += 1;

            let mut data = data.lock().unwrap();
            data.remove(&key_vec);

            Ok(())
        }
    }
}

/// Mock set implementation for testing `RedisSet` operations.
#[derive(Clone, Debug)]
pub struct MockSet {
    data: Arc<Mutex<std::collections::HashSet<String>>>,
    error_mode: Arc<Mutex<Option<String>>>,
}

impl MockSet {
    /// Creates a new empty mock set.
    pub fn new() -> Self {
        Self {
            data: Arc::new(Mutex::new(std::collections::HashSet::new())),
            error_mode: Arc::new(Mutex::new(None)),
        }
    }

    /// Enables error mode for testing error handling.
    pub fn enable_error_mode(&self, message: &str) {
        let mut error_mode = self.error_mode.lock().unwrap();
        *error_mode = Some(message.to_owned());
    }

    /// Disables error mode.
    pub fn disable_error_mode(&self) {
        let mut error_mode = self.error_mode.lock().unwrap();
        *error_mode = None;
    }

    /// Adds items to the set.
    pub async fn add_items(&self, items: &[String]) -> anyhow::Result<()> {
        check_error_mode!(self.error_mode);

        if items.is_empty() {
            return Ok(());
        }

        let mut data = self.data.lock().unwrap();
        for item in items {
            data.insert(item.clone());
        }
        Ok(())
    }

    /// Removes items from the set.
    pub async fn remove_items(&self, items: &[String]) -> anyhow::Result<()> {
        check_error_mode!(self.error_mode);

        if items.is_empty() {
            return Ok(());
        }

        let mut data = self.data.lock().unwrap();
        for item in items {
            data.remove(item);
        }
        Ok(())
    }

    /// Adds a single item to the set.
    pub async fn add_item(&self, item: &str) -> anyhow::Result<()> {
        self.add_items(&[item.to_owned()]).await
    }

    /// Removes a single item from the set.
    pub async fn remove_item(&self, item: &str) -> anyhow::Result<()> {
        self.remove_items(&[item.to_owned()]).await
    }

    /// Returns all items in the set.
    pub async fn load_items(&self) -> anyhow::Result<Vec<String>> {
        check_error_mode!(self.error_mode);

        let data = self.data.lock().unwrap();
        Ok(data.iter().cloned().collect())
    }

    /// Trims the set to `max_entries` by removing arbitrary entries.
    pub async fn trim_to(&self, max_entries: usize) -> anyhow::Result<()> {
        check_error_mode!(self.error_mode);

        if max_entries == 0 {
            return Ok(());
        }

        let mut data = self.data.lock().unwrap();
        while data.len() > max_entries {
            // Remove an arbitrary element
            if let Some(item) = data.iter().next().cloned() {
                data.remove(&item);
            }
        }
        Ok(())
    }

    /// Returns the number of items in the set.
    pub fn len(&self) -> usize {
        self.data.lock().unwrap().len()
    }

    /// Returns true if the set is empty.
    pub fn is_empty(&self) -> bool {
        self.data.lock().unwrap().is_empty()
    }

    /// Clears all items from the set.
    pub fn clear(&self) {
        self.data.lock().unwrap().clear();
    }

    /// Checks if the set contains an item.
    pub fn contains(&self, item: &str) -> bool {
        self.data.lock().unwrap().contains(item)
    }
}

impl Default for MockSet {
    fn default() -> Self {
        Self::new()
    }
}

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

    #[tokio::test]
    async fn test_mock_cache_basic_operations() {
        let cache = MockCache::new();

        // Test set and get
        cache
            .set(b"key1", b"value1", Duration::from_secs(60))
            .await
            .unwrap();
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, Some(b"value1".to_vec()));

        // Test get non-existent
        let result = cache.get(b"nonexistent").await.unwrap();
        assert_eq!(result, None);

        // Test delete
        cache.del(b"key1").await.unwrap();
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, None);
    }

    #[tokio::test]
    async fn test_mock_cache_set_nx_px() {
        let cache = MockCache::new();

        // First set should succeed
        let was_set = cache
            .set_nx_px(b"key1", b"value1", Duration::from_secs(60))
            .await
            .unwrap();
        assert!(was_set);

        // Second set should fail
        let was_set = cache
            .set_nx_px(b"key1", b"value2", Duration::from_secs(60))
            .await
            .unwrap();
        assert!(!was_set);

        // Value should be original
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, Some(b"value1".to_vec()));
    }

    #[tokio::test]
    async fn test_mock_cache_error_mode() {
        let cache = MockCache::new();

        // Normal operation should succeed
        cache
            .set(b"key1", b"value1", Duration::from_secs(60))
            .await
            .unwrap();

        // Enable error mode
        cache.enable_error_mode("Redis connection failed");

        // All operations should fail
        let result = cache.get(b"key1").await;
        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("connection failed")
        );

        let result = cache.set(b"key2", b"value2", Duration::from_secs(60)).await;
        assert!(result.is_err());

        let result = cache
            .set_nx_px(b"key3", b"value3", Duration::from_secs(60))
            .await;
        assert!(result.is_err());

        let result = cache.del(b"key1").await;
        assert!(result.is_err());

        // Disable error mode
        cache.disable_error_mode();

        // Operations should succeed again
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, Some(b"value1".to_vec()));
    }

    #[tokio::test]
    async fn test_mock_cache_operation_counts() {
        let cache = MockCache::new();

        cache
            .set(b"k1", b"v1", Duration::from_secs(60))
            .await
            .unwrap();
        cache
            .set(b"k2", b"v2", Duration::from_secs(60))
            .await
            .unwrap();
        cache.get(b"k1").await.unwrap();
        cache.get(b"k2").await.unwrap();
        cache.get(b"k3").await.unwrap();
        cache
            .set_nx_px(b"k4", b"v4", Duration::from_secs(60))
            .await
            .unwrap();
        cache.del(b"k1").await.unwrap();

        let counts = cache.operation_counts();
        assert_eq!(counts.sets, 2);
        assert_eq!(counts.gets, 3);
        assert_eq!(counts.set_nx_px, 1);
        assert_eq!(counts.deletes, 1);

        cache.reset_counts();
        let counts = cache.operation_counts();
        assert_eq!(counts.sets, 0);
        assert_eq!(counts.gets, 0);
    }

    #[tokio::test]
    async fn test_mock_cache_ttl_expiration() {
        let cache = MockCache::new();

        cache
            .set(b"key1", b"value1", Duration::from_millis(50))
            .await
            .unwrap();

        // Should exist immediately
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, Some(b"value1".to_vec()));

        // Wait for expiration
        tokio::time::sleep(Duration::from_millis(100)).await;

        // Should be expired
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, None);
    }

    #[tokio::test]
    async fn test_mock_cache_force_expire() {
        let cache = MockCache::new();

        cache
            .set(b"key1", b"value1", Duration::from_secs(60))
            .await
            .unwrap();

        // Force expire
        cache.force_expire(b"key1");

        // Should be expired
        let result = cache.get(b"key1").await.unwrap();
        assert_eq!(result, None);
    }

    #[tokio::test]
    async fn test_mock_cache_with_data() {
        let cache = MockCache::with_data([
            (b"key1".as_slice(), b"value1".as_slice()),
            (b"key2", b"value2"),
        ]);

        let result1 = cache.get(b"key1").await.unwrap();
        assert_eq!(result1, Some(b"value1".to_vec()));

        let result2 = cache.get(b"key2").await.unwrap();
        assert_eq!(result2, Some(b"value2".to_vec()));
    }

    #[tokio::test]
    async fn test_mock_cache_len_and_clear() {
        let cache = MockCache::new();

        assert!(cache.is_empty());
        assert_eq!(cache.len(), 0);

        cache
            .set(b"k1", b"v1", Duration::from_secs(60))
            .await
            .unwrap();
        cache
            .set(b"k2", b"v2", Duration::from_secs(60))
            .await
            .unwrap();

        assert!(!cache.is_empty());
        assert_eq!(cache.len(), 2);

        cache.clear();

        assert!(cache.is_empty());
        assert_eq!(cache.len(), 0);
    }

    #[tokio::test]
    async fn test_mock_set_basic_operations() {
        let set = MockSet::new();

        assert!(set.is_empty());

        // Add items
        set.add_item("item1").await.unwrap();
        set.add_item("item2").await.unwrap();

        assert_eq!(set.len(), 2);
        assert!(set.contains("item1"));
        assert!(set.contains("item2"));
        assert!(!set.contains("item3"));

        // Load items
        let items = set.load_items().await.unwrap();
        assert_eq!(items.len(), 2);

        // Remove item
        set.remove_item("item1").await.unwrap();
        assert!(!set.contains("item1"));
        assert_eq!(set.len(), 1);

        // Clear
        set.clear();
        assert!(set.is_empty());
    }

    #[tokio::test]
    async fn test_mock_set_batch_operations() {
        let set = MockSet::new();

        // Add multiple items
        set.add_items(&["a".to_owned(), "b".to_owned(), "c".to_owned()])
            .await
            .unwrap();
        assert_eq!(set.len(), 3);

        // Remove multiple items
        set.remove_items(&["a".to_owned(), "c".to_owned()])
            .await
            .unwrap();
        assert_eq!(set.len(), 1);
        assert!(set.contains("b"));
    }

    #[tokio::test]
    async fn test_mock_set_trim_to() {
        let set = MockSet::new();

        for i in 0..10 {
            set.add_item(&format!("item{i}")).await.unwrap();
        }
        assert_eq!(set.len(), 10);

        set.trim_to(5).await.unwrap();
        assert_eq!(set.len(), 5);

        // trim_to(0) should do nothing (matches RedisSet behavior)
        set.trim_to(0).await.unwrap();
        assert_eq!(set.len(), 5);
    }

    #[tokio::test]
    async fn test_mock_set_error_mode() {
        let set = MockSet::new();

        set.add_item("item1").await.unwrap();

        set.enable_error_mode("Redis error");

        assert!(set.add_item("item2").await.is_err());
        assert!(set.remove_item("item1").await.is_err());
        assert!(set.load_items().await.is_err());
        assert!(set.trim_to(1).await.is_err());

        set.disable_error_mode();

        assert!(set.load_items().await.is_ok());
    }

    #[tokio::test]
    async fn test_mock_set_empty_operations() {
        let set = MockSet::new();

        // Empty operations should succeed
        set.add_items(&[]).await.unwrap();
        set.remove_items(&[]).await.unwrap();

        assert!(set.is_empty());
    }
}