what-core 1.7.0

//! Caching system for What framework
//!
//! Provides multi-level caching with support for:
//! - Per-page caching
//! - Per-user caching
//! - Per-content caching
//! - External API response caching

use moka::future::Cache;
use std::collections::{HashMap, HashSet};
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::RwLock;

/// Cache key types for different caching strategies
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum CacheKey {
    /// Cache by page path only (global cache)
    Page(String),
    /// Cache by page + user ID
    UserPage { path: String, user_id: String },
    /// Cache by content ID (e.g., post ID)
    Content { content_type: String, id: String },
    /// Cache by user + content
    UserContent {
        user_id: String,
        content_type: String,
        id: String,
    },
    /// Cache for external API responses
    External { url: String },
    /// Custom cache key
    Custom(String),
}

impl CacheKey {
    /// Create a page cache key
    pub fn page(path: impl Into<String>) -> Self {
        Self::Page(path.into())
    }

    /// Create a user-specific page cache key
    pub fn user_page(path: impl Into<String>, user_id: impl Into<String>) -> Self {
        Self::UserPage {
            path: path.into(),
            user_id: user_id.into(),
        }
    }

    /// Create a content cache key
    pub fn content(content_type: impl Into<String>, id: impl Into<String>) -> Self {
        Self::Content {
            content_type: content_type.into(),
            id: id.into(),
        }
    }

    /// Create a user-specific content cache key
    pub fn user_content(
        user_id: impl Into<String>,
        content_type: impl Into<String>,
        id: impl Into<String>,
    ) -> Self {
        Self::UserContent {
            user_id: user_id.into(),
            content_type: content_type.into(),
            id: id.into(),
        }
    }

    /// Create an external API cache key
    pub fn external(url: impl Into<String>) -> Self {
        Self::External { url: url.into() }
    }

    /// Create a custom cache key
    pub fn custom(key: impl Into<String>) -> Self {
        Self::Custom(key.into())
    }

    /// Convert to string representation for the cache
    fn to_cache_key(&self) -> String {
        match self {
            Self::Page(path) => format!("page:{}", path),
            Self::UserPage { path, user_id } => format!("user:{}:page:{}", user_id, path),
            Self::Content { content_type, id } => format!("content:{}:{}", content_type, id),
            Self::UserContent {
                user_id,
                content_type,
                id,
            } => format!("user:{}:content:{}:{}", user_id, content_type, id),
            Self::External { url } => format!("external:{}", url),
            Self::Custom(key) => format!("custom:{}", key),
        }
    }
}

/// Cached value with metadata
#[derive(Debug, Clone)]
pub struct CachedValue {
    /// The cached content
    pub content: String,
    /// ETag for conditional requests
    pub etag: Option<String>,
    /// Content type
    pub content_type: String,
}

impl CachedValue {
    pub fn html(content: String) -> Self {
        Self {
            content,
            etag: None,
            content_type: "text/html".to_string(),
        }
    }

    pub fn json(content: String) -> Self {
        Self {
            content,
            etag: None,
            content_type: "application/json".to_string(),
        }
    }

    pub fn with_etag(mut self, etag: impl Into<String>) -> Self {
        self.etag = Some(etag.into());
        self
    }
}

/// Multi-level cache for the What framework
#[derive(Clone)]
pub struct WhatCache {
    /// Main content cache
    content_cache: Cache<String, CachedValue>,
    /// External API response cache
    api_cache: Cache<String, String>,
    /// Default TTL for content
    #[allow(dead_code)]
    default_ttl: Duration,
    /// Default TTL for API responses
    #[allow(dead_code)]
    api_ttl: Duration,
    /// Tag index: maps tag (e.g., collection name) → set of cache keys
    /// Used for targeted invalidation instead of clearing the entire cache.
    tag_index: Arc<RwLock<HashMap<String, HashSet<String>>>>,
}

impl WhatCache {
    /// Create a new cache with default settings
    pub fn new() -> Self {
        Self::with_config(CacheConfig::default())
    }

    /// Create a cache with custom configuration
    pub fn with_config(config: CacheConfig) -> Self {
        let content_cache = Cache::builder()
            .max_capacity(config.max_content_entries)
            .time_to_live(Duration::from_secs(config.content_ttl_secs))
            .build();

        let api_cache = Cache::builder()
            .max_capacity(config.max_api_entries)
            .time_to_live(Duration::from_secs(config.api_ttl_secs))
            .build();

        Self {
            content_cache,
            api_cache,
            default_ttl: Duration::from_secs(config.content_ttl_secs),
            api_ttl: Duration::from_secs(config.api_ttl_secs),
            tag_index: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// Get a cached page/content
    pub async fn get(&self, key: &CacheKey) -> Option<CachedValue> {
        self.content_cache.get(&key.to_cache_key()).await
    }

    /// Cache a page/content
    pub async fn set(&self, key: &CacheKey, value: CachedValue) {
        self.content_cache.insert(key.to_cache_key(), value).await;
    }

    /// Cache a page/content and associate it with tags for targeted invalidation.
    /// Tags are typically collection names (e.g., "posts", "users").
    pub async fn set_with_tags(&self, key: &CacheKey, value: CachedValue, tags: &[&str]) {
        let cache_key = key.to_cache_key();
        self.content_cache.insert(cache_key.clone(), value).await;

        if !tags.is_empty() {
            let mut index = self.tag_index.write().await;
            for tag in tags {
                index
                    .entry(tag.to_string())
                    .or_default()
                    .insert(cache_key.clone());
            }
        }
    }

    /// Cache a page/content with custom TTL
    pub async fn set_with_ttl(&self, key: &CacheKey, value: CachedValue, _ttl: Duration) {
        // Note: moka doesn't support per-entry TTL easily,
        // so we use the default TTL. For production, consider
        // using a different cache backend or custom expiry logic.
        self.content_cache.insert(key.to_cache_key(), value).await;
    }

    /// Get cached API response
    pub async fn get_api(&self, url: &str) -> Option<String> {
        self.api_cache.get(&format!("api:{}", url)).await
    }

    /// Cache API response
    pub async fn set_api(&self, url: &str, response: String) {
        self.api_cache
            .insert(format!("api:{}", url), response)
            .await;
    }

    /// Invalidate a specific cache entry
    pub async fn invalidate(&self, key: &CacheKey) {
        self.content_cache.invalidate(&key.to_cache_key()).await;
    }

    /// Invalidate all entries matching a tag.
    /// If no entries are tagged, falls back to full cache clear.
    pub async fn invalidate_by_tag(&self, tag: &str) {
        let mut index = self.tag_index.write().await;
        if let Some(keys) = index.remove(tag) {
            for key in &keys {
                self.content_cache.invalidate(key).await;
            }
            self.content_cache.run_pending_tasks().await;
            tracing::debug!(
                "Cache: invalidated {} entries for tag '{}'",
                keys.len(),
                tag
            );
        }
        // Also clean up any references to this tag's keys from other tags
        // (a key can have multiple tags)
    }

    /// Invalidate all content cache entries for a specific content type / collection.
    /// Uses the tag index for targeted invalidation. If no entries are tagged,
    /// falls back to full cache clear for safety.
    pub async fn invalidate_content_type(&self, content_type: &str) {
        let index = self.tag_index.read().await;
        if index.contains_key(content_type) {
            drop(index); // Release read lock before taking write lock
            self.invalidate_by_tag(content_type).await;
        } else {
            drop(index);
            // Fallback: no tagged entries, clear all content cache
            self.content_cache.invalidate_all();
            self.content_cache.run_pending_tasks().await;
        }
    }

    /// Invalidate all cache entries for a specific user.
    /// Uses prefix matching on cache keys.
    pub async fn invalidate_user(&self, user_id: &str) {
        let prefix = format!("user:{}:", user_id);
        let index = self.tag_index.read().await;
        if let Some(keys) = index.get(user_id) {
            let keys_to_remove: Vec<String> = keys.iter().cloned().collect();
            drop(index);
            for key in &keys_to_remove {
                self.content_cache.invalidate(key).await;
            }
        } else {
            drop(index);
            // Fallback: scan for keys with user prefix (best effort)
            // Moka doesn't support prefix scanning, so we clear all
            let _ = prefix; // Used for documentation, not runtime
            self.content_cache.invalidate_all();
        }
        self.content_cache.run_pending_tasks().await;
    }

    /// Clear all caches
    pub async fn clear_all(&self) {
        self.content_cache.invalidate_all();
        self.api_cache.invalidate_all();
        self.content_cache.run_pending_tasks().await;
        self.api_cache.run_pending_tasks().await;
        self.tag_index.write().await.clear();
    }

    /// Get cache statistics
    pub fn stats(&self) -> CacheStats {
        CacheStats {
            content_entries: self.content_cache.entry_count(),
            api_entries: self.api_cache.entry_count(),
        }
    }
}

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

/// Cache configuration
#[derive(Debug, Clone)]
pub struct CacheConfig {
    /// Max entries in content cache
    pub max_content_entries: u64,
    /// Max entries in API cache
    pub max_api_entries: u64,
    /// TTL for content in seconds
    pub content_ttl_secs: u64,
    /// TTL for API responses in seconds
    pub api_ttl_secs: u64,
}

impl Default for CacheConfig {
    fn default() -> Self {
        Self {
            max_content_entries: 10_000,
            max_api_entries: 1_000,
            content_ttl_secs: 300, // 5 minutes
            api_ttl_secs: 60,      // 1 minute
        }
    }
}

/// Cache statistics
#[derive(Debug, Clone)]
pub struct CacheStats {
    pub content_entries: u64,
    pub api_entries: u64,
}

/// Cache control directives for responses
#[derive(Debug, Clone, Default)]
pub struct CacheControl {
    /// Cache scope
    pub scope: CacheScope,
    /// Max age in seconds
    pub max_age: Option<u64>,
    /// Whether to revalidate
    pub must_revalidate: bool,
    /// Whether this is immutable
    pub immutable: bool,
}

#[derive(Debug, Clone, Default)]
pub enum CacheScope {
    /// Can be cached by any cache (CDN, browser, etc.)
    #[default]
    Public,
    /// Only cache in user's browser
    Private,
    /// Don't cache at all
    NoCache,
    /// Don't store at all
    NoStore,
}

impl CacheControl {
    pub fn public(max_age: u64) -> Self {
        Self {
            scope: CacheScope::Public,
            max_age: Some(max_age),
            must_revalidate: false,
            immutable: false,
        }
    }

    pub fn private(max_age: u64) -> Self {
        Self {
            scope: CacheScope::Private,
            max_age: Some(max_age),
            must_revalidate: false,
            immutable: false,
        }
    }

    pub fn no_cache() -> Self {
        Self {
            scope: CacheScope::NoCache,
            max_age: None,
            must_revalidate: true,
            immutable: false,
        }
    }

    pub fn immutable() -> Self {
        Self {
            scope: CacheScope::Public,
            max_age: Some(31536000), // 1 year
            must_revalidate: false,
            immutable: true,
        }
    }

    /// Convert to HTTP Cache-Control header value
    pub fn to_header_value(&self) -> String {
        let mut parts = Vec::new();

        match self.scope {
            CacheScope::Public => parts.push("public".to_string()),
            CacheScope::Private => parts.push("private".to_string()),
            CacheScope::NoCache => parts.push("no-cache".to_string()),
            CacheScope::NoStore => parts.push("no-store".to_string()),
        }

        if let Some(max_age) = self.max_age {
            parts.push(format!("max-age={}", max_age));
        }

        if self.must_revalidate {
            parts.push("must-revalidate".to_string());
        }

        if self.immutable {
            parts.push("immutable".to_string());
        }

        parts.join(", ")
    }
}

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

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

        let key = CacheKey::page("/about");
        let value = CachedValue::html("<h1>About</h1>".to_string());

        cache.set(&key, value.clone()).await;

        let retrieved = cache.get(&key).await.unwrap();
        assert_eq!(retrieved.content, "<h1>About</h1>");
    }

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

        let key1 = CacheKey::user_page("/dashboard", "user1");
        let key2 = CacheKey::user_page("/dashboard", "user2");

        cache
            .set(&key1, CachedValue::html("User 1 Dashboard".to_string()))
            .await;
        cache
            .set(&key2, CachedValue::html("User 2 Dashboard".to_string()))
            .await;

        assert_eq!(cache.get(&key1).await.unwrap().content, "User 1 Dashboard");
        assert_eq!(cache.get(&key2).await.unwrap().content, "User 2 Dashboard");
    }

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

        let key1 = CacheKey::page("/blog");
        let key2 = CacheKey::page("/blog/post-1");
        let key3 = CacheKey::page("/about");

        // Cache pages with tags
        cache
            .set_with_tags(&key1, CachedValue::html("Blog list".into()), &["posts"])
            .await;
        cache
            .set_with_tags(&key2, CachedValue::html("Post 1".into()), &["posts"])
            .await;
        cache
            .set_with_tags(&key3, CachedValue::html("About page".into()), &["pages"])
            .await;

        // All should be cached
        assert!(cache.get(&key1).await.is_some());
        assert!(cache.get(&key2).await.is_some());
        assert!(cache.get(&key3).await.is_some());

        // Invalidate "posts" tag — should only remove blog pages
        cache.invalidate_by_tag("posts").await;

        assert!(cache.get(&key1).await.is_none());
        assert!(cache.get(&key2).await.is_none());
        assert!(cache.get(&key3).await.is_some()); // About page untouched
    }

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

        let key1 = CacheKey::page("/products");
        let key2 = CacheKey::page("/cart");

        cache
            .set_with_tags(&key1, CachedValue::html("Products".into()), &["products"])
            .await;
        cache
            .set_with_tags(&key2, CachedValue::html("Cart".into()), &["cart"])
            .await;

        // Invalidate "products" via content_type
        cache.invalidate_content_type("products").await;

        assert!(cache.get(&key1).await.is_none());
        assert!(cache.get(&key2).await.is_some());
    }

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

        let key = CacheKey::page("/test");
        // Set WITHOUT tags
        cache.set(&key, CachedValue::html("Test".into())).await;

        // Invalidate unknown content type — should fall back to clearing all
        cache.invalidate_content_type("unknown").await;

        assert!(cache.get(&key).await.is_none());
    }

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

        let key = CacheKey::page("/blog");
        cache
            .set_with_tags(&key, CachedValue::html("Blog".into()), &["posts"])
            .await;

        cache.clear_all().await;

        assert!(cache.get(&key).await.is_none());
        // Tag index should be empty
        assert!(cache.tag_index.read().await.is_empty());
    }

    #[test]
    fn test_cache_control_header() {
        let cc = CacheControl::public(3600);
        assert_eq!(cc.to_header_value(), "public, max-age=3600");

        let cc = CacheControl::private(600);
        assert_eq!(cc.to_header_value(), "private, max-age=600");

        let cc = CacheControl::no_cache();
        assert_eq!(cc.to_header_value(), "no-cache, must-revalidate");

        let cc = CacheControl::immutable();
        assert_eq!(cc.to_header_value(), "public, max-age=31536000, immutable");
    }
}