pub mod details;

pub use details::{DetailedModelInfo, ModelInfoRetrievalError};

use crate::Result;
use crate::types::ModelInfo;
use std::collections::HashMap;
use std::future::Future;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::RwLock;

#[derive(Default, Debug)]
struct ModelCache {
    models: Vec<ModelInfo>,
    last_refresh: Option<Instant>,
}

/// Caches model listings for improved selection performance
#[derive(Clone, Debug)]
pub struct ModelManager {
    cache: Arc<RwLock<ModelCache>>,
    ttl: Duration,
}

impl ModelManager {
    /// Create a new manager with the desired cache TTL
    pub fn new(ttl: Duration) -> Self {
        Self {
            cache: Arc::new(RwLock::new(ModelCache::default())),
            ttl,
        }
    }

    /// Get cached models, refreshing via the provided fetcher when stale. Returns the up-to-date model list.
    pub async fn get_or_refresh<F, Fut>(
        &self,
        force_refresh: bool,
        fetcher: F,
    ) -> Result<Vec<ModelInfo>>
    where
        F: FnOnce() -> Fut,
        Fut: Future<Output = Result<Vec<ModelInfo>>>,
    {
        if let (false, Some(models)) = (force_refresh, self.cached_if_fresh().await) {
            return Ok(models);
        }

        let models = fetcher().await?;
        let mut cache = self.cache.write().await;
        cache.models = models.clone();
        cache.last_refresh = Some(Instant::now());
        Ok(models)
    }

    /// Return cached models without refreshing
    pub async fn cached(&self) -> Vec<ModelInfo> {
        self.cache.read().await.models.clone()
    }

    /// Drop cached models, forcing next call to refresh
    pub async fn invalidate(&self) {
        let mut cache = self.cache.write().await;
        cache.models.clear();
        cache.last_refresh = None;
    }

    /// Select a model by id or name from the cache
    pub async fn select(&self, identifier: &str) -> Option<ModelInfo> {
        let cache = self.cache.read().await;
        cache
            .models
            .iter()
            .find(|m| m.id == identifier || m.name == identifier)
            .cloned()
    }

    async fn cached_if_fresh(&self) -> Option<Vec<ModelInfo>> {
        let cache = self.cache.read().await;
        let fresh = matches!(cache.last_refresh, Some(ts) if ts.elapsed() < self.ttl);
        if fresh && !cache.models.is_empty() {
            Some(cache.models.clone())
        } else {
            None
        }
    }
}

#[derive(Default, Debug)]
struct ModelDetailsCacheInner {
    by_key: HashMap<String, DetailedModelInfo>,
    name_to_key: HashMap<String, String>,
    fetched_at: HashMap<String, Instant>,
}

/// Cache for rich model details, indexed by digest when available.
#[derive(Clone, Debug)]
pub struct ModelDetailsCache {
    inner: Arc<RwLock<ModelDetailsCacheInner>>,
    ttl: Duration,
}

impl ModelDetailsCache {
    /// Create a new details cache with the provided TTL.
    pub fn new(ttl: Duration) -> Self {
        Self {
            inner: Arc::new(RwLock::new(ModelDetailsCacheInner::default())),
            ttl,
        }
    }

    /// Try to read cached details for the provided model name.
    pub async fn get(&self, name: &str) -> Option<DetailedModelInfo> {
        let mut inner = self.inner.write().await;
        let key = inner.name_to_key.get(name).cloned()?;
        let stale = inner
            .fetched_at
            .get(&key)
            .is_some_and(|ts| ts.elapsed() >= self.ttl);
        if stale {
            inner.by_key.remove(&key);
            inner.name_to_key.remove(name);
            inner.fetched_at.remove(&key);
            return None;
        }
        inner.by_key.get(&key).cloned()
    }

    /// Cache the provided details, overwriting existing entries.
    pub async fn insert(&self, info: DetailedModelInfo) {
        let key = info.digest.clone().unwrap_or_else(|| info.name.clone());
        let mut inner = self.inner.write().await;

        // Remove prior mappings for this model name (possibly different digest).
        if let Some(previous_key) = inner.name_to_key.get(&info.name).cloned()
            && previous_key != key
        {
            inner.by_key.remove(&previous_key);
            inner.fetched_at.remove(&previous_key);
        }

        inner.fetched_at.insert(key.clone(), Instant::now());
        inner.name_to_key.insert(info.name.clone(), key.clone());
        inner.by_key.insert(key, info);
    }

    /// Remove a specific model from the cache.
    pub async fn invalidate(&self, name: &str) {
        let mut inner = self.inner.write().await;
        if let Some(key) = inner.name_to_key.remove(name) {
            inner.by_key.remove(&key);
            inner.fetched_at.remove(&key);
        }
    }

    /// Clear the entire cache.
    pub async fn invalidate_all(&self) {
        let mut inner = self.inner.write().await;
        inner.by_key.clear();
        inner.name_to_key.clear();
        inner.fetched_at.clear();
    }

    /// Return all cached values regardless of freshness.
    pub async fn cached(&self) -> Vec<DetailedModelInfo> {
        let inner = self.inner.read().await;
        inner.by_key.values().cloned().collect()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::time::Duration;
    use tokio::time::sleep;

    fn sample_details(name: &str) -> DetailedModelInfo {
        DetailedModelInfo {
            name: name.to_string(),
            ..Default::default()
        }
    }

    #[tokio::test]
    async fn model_details_cache_returns_cached_entry() {
        let cache = ModelDetailsCache::new(Duration::from_millis(50));
        let info = sample_details("llama");
        cache.insert(info.clone()).await;
        let cached = cache.get("llama").await;
        assert!(cached.is_some());
        assert_eq!(cached.unwrap().name, "llama");
    }

    #[tokio::test]
    async fn model_details_cache_expires_based_on_ttl() {
        let cache = ModelDetailsCache::new(Duration::from_millis(10));
        cache.insert(sample_details("phi")).await;
        sleep(Duration::from_millis(30)).await;
        assert!(cache.get("phi").await.is_none());
    }

    #[tokio::test]
    async fn model_details_cache_invalidate_removes_entry() {
        let cache = ModelDetailsCache::new(Duration::from_secs(1));
        cache.insert(sample_details("mistral")).await;
        cache.invalidate("mistral").await;
        assert!(cache.get("mistral").await.is_none());
    }
}