martin-core 0.5.0

use std::sync::Arc;
use std::time::Duration;

use moka::future::Cache;
use tracing::{info, trace};

#[cfg(feature = "metrics")]
use crate::metrics::CACHE_REQUESTS_TOTAL;

/// Optional wrapper for `FontCache`.
pub type OptFontCache = Option<FontCache>;

/// Constant representing no font cache configuration.
pub const NO_FONT_CACHE: OptFontCache = None;

/// Font cache for storing generated font ranges.
#[derive(Clone, Debug)]
pub struct FontCache {
    cache: Cache<FontCacheKey, Vec<u8>>,
}

impl FontCache {
    /// Creates a new font cache with the specified maximum size in bytes.
    #[must_use]
    pub fn new(
        max_size_bytes: u64,
        expiry: Option<Duration>,
        idle_timeout: Option<Duration>,
    ) -> Self {
        let mut builder = Cache::builder()
            .name("font_cache")
            .weigher(|_key: &FontCacheKey, value: &Vec<u8>| -> u32 {
                value.len().try_into().unwrap_or(u32::MAX)
            })
            .max_capacity(max_size_bytes);
        if let Some(ttl) = expiry {
            builder = builder.time_to_live(ttl);
        }
        if let Some(tti) = idle_timeout {
            builder = builder.time_to_idle(tti);
        }
        Self {
            cache: builder.build(),
        }
    }

    /// Gets a font range from cache or computes it using the provided function.
    pub async fn get_or_insert<F, E>(
        &self,
        ids: String,
        start: u32,
        end: u32,
        compute: F,
    ) -> Result<Vec<u8>, Arc<E>>
    where
        F: FnOnce() -> Result<Vec<u8>, E>,
        E: Send + Sync + 'static,
    {
        let key = FontCacheKey::new(ids, start, end);
        let entry = self
            .cache
            .entry(key.clone())
            .or_try_insert_with(async move { compute() })
            .await?;

        if entry.is_fresh() {
            #[cfg(feature = "metrics")]
            CACHE_REQUESTS_TOTAL
                .with_label_values(&["font", "miss"])
                .inc();
            hotpath::gauge!("font_cache_misses").inc(1.0);
            trace!("Font cache MISS for {key:?}");
        } else {
            #[cfg(feature = "metrics")]
            CACHE_REQUESTS_TOTAL
                .with_label_values(&["font", "hit"])
                .inc();
            hotpath::gauge!("font_cache_hits").inc(1.0);
            trace!(
                "Font cache HIT for {key:?} (entries={}, size={})",
                self.cache.entry_count(),
                self.cache.weighted_size()
            );
        }

        Ok(entry.into_value())
    }

    /// Invalidates all cached font ranges that use the specified font ID.
    pub fn invalidate_font(&self, font_id: &str) {
        let font_id_owned = font_id.to_string();
        self.cache
            .invalidate_entries_if(move |key, _| key.ids.contains(&font_id_owned))
            .expect("invalidate_entries_if predicate should not error");
        info!("Invalidated font cache for font: {font_id}");
    }

    /// Invalidates all cached font ranges.
    pub fn invalidate_all(&self) {
        self.cache.invalidate_all();
        info!("Invalidated all font cache entries");
    }

    /// Returns the number of cached entries.
    #[must_use]
    pub fn entry_count(&self) -> u64 {
        self.cache.entry_count()
    }

    /// Returns the total size of cached data in bytes.
    #[must_use]
    pub fn weighted_size(&self) -> u64 {
        self.cache.weighted_size()
    }

    /// Runs pending maintenance tasks (e.g. processing invalidation predicates).
    pub async fn run_pending_tasks(&self) {
        self.cache.run_pending_tasks().await;
    }
}

/// Cache key for font data.
#[derive(Debug, Hash, PartialEq, Eq, Clone)]
struct FontCacheKey {
    ids: String,
    start: u32,
    end: u32,
}

impl FontCacheKey {
    fn new(ids: String, start: u32, end: u32) -> Self {
        Self { ids, start, end }
    }
}