//! MessagePack voice cache (D-138, Spike 2).
//!
//! Stores re-voiced text keyed by (npc, content, tell state, culture).
//! Length-gated variant count: short lines cache neutral only, medium lines
//! cache 3 variants, long lines cache all applicable tells.
//!
//! Baked content is just pre-populated cache — `make voice-bake` writes to
//! the same directory. No separate baked path.

use serde::{Deserialize, Serialize};
use std::collections::BTreeMap;
use std::fs;
use std::io;
use std::path::PathBuf;

use crate::npc::tell_state::TellCategory;
use crate::voice::prompt_builder::ContentType;

/// Cache key for a single voiced line.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct CacheKey {
    pub culture_id: String,
    pub npc_stable_id: u64,
    pub content_type: ContentType,
    pub content_index: u16,
    /// Tell state variant. `None` = neutral (used for short content).
    pub tell_state: Option<TellCategory>,
}

/// A single zone's voice cache — maps cache keys to voiced text.
#[derive(Debug, Default, Serialize, Deserialize)]
pub struct ZoneVoiceCache {
    /// Model version hash — cache miss if this doesn't match.
    pub model_version: String,
    /// Injector version hash — cache miss if this doesn't match.
    pub injector_version: String,
    /// Cached voiced lines.
    pub entries: BTreeMap<CacheKey, String>,
}

impl ZoneVoiceCache {
    pub fn new(model_version: String, injector_version: String) -> Self {
        Self {
            model_version,
            injector_version,
            entries: BTreeMap::new(),
        }
    }

    /// Look up a cached voiced line. Returns `None` on miss.
    pub fn lookup(&self, key: &CacheKey) -> Option<&str> {
        self.entries.get(key).map(|s| s.as_str())
    }

    /// Store a voiced line in the cache.
    pub fn store(&mut self, key: CacheKey, text: String) {
        self.entries.insert(key, text);
    }

    /// Number of cached entries.
    pub fn len(&self) -> usize {
        self.entries.len()
    }

    pub fn is_empty(&self) -> bool {
        self.entries.is_empty()
    }
}

/// Manages voice caches across zones with disk persistence.
#[derive(Debug)]
pub struct VoiceCacheStore {
    /// Base directory for cache files.
    base_dir: PathBuf,
    /// World seed — part of the directory path.
    world_seed: u64,
    /// Current model version hash.
    model_version: String,
    /// Current injector version hash.
    injector_version: String,
    /// Loaded zone caches.
    zones: BTreeMap<u32, ZoneVoiceCache>,
}

impl VoiceCacheStore {
    /// Create a new cache store. Does not load any zones yet.
    pub fn new(
        base_dir: PathBuf,
        world_seed: u64,
        model_version: String,
        injector_version: String,
    ) -> Self {
        Self {
            base_dir,
            world_seed,
            model_version,
            injector_version,
            zones: BTreeMap::new(),
        }
    }

    /// Get or load the cache for a zone.
    pub fn zone_cache(&mut self, zone_id: u32) -> &mut ZoneVoiceCache {
        if !self.zones.contains_key(&zone_id) {
            let cache = self.load_zone(zone_id).unwrap_or_else(|| {
                ZoneVoiceCache::new(self.model_version.clone(), self.injector_version.clone())
            });
            self.zones.insert(zone_id, cache);
        }
        self.zones.get_mut(&zone_id).unwrap()
    }

    /// Look up a voiced line across the right zone cache.
    pub fn lookup(&mut self, zone_id: u32, key: &CacheKey) -> Option<String> {
        let cache = self.zone_cache(zone_id);
        cache.lookup(key).map(|s| s.to_string())
    }

    /// Store a voiced line and return the stored text.
    pub fn store(&mut self, zone_id: u32, key: CacheKey, text: String) {
        let cache = self.zone_cache(zone_id);
        cache.store(key, text);
    }

    /// Persist a zone's cache to disk as MessagePack.
    ///
    /// Not atomic (no rename-into-place) — a crash mid-write can produce a
    /// partial file. This is acceptable: worst case is a cache miss on next
    /// load, triggering re-inference or base text fallback.
    pub fn save_zone(&self, zone_id: u32) -> io::Result<()> {
        let Some(cache) = self.zones.get(&zone_id) else {
            return Ok(());
        };

        let dir = self.zone_dir();
        fs::create_dir_all(&dir)?;

        let path = dir.join(format!("{}.msgpack", zone_id));
        let data = rmp_serde::to_vec(cache).map_err(io::Error::other)?;
        fs::write(path, data)
    }

    /// Save all loaded zone caches to disk.
    pub fn save_all(&self) -> io::Result<()> {
        for &zone_id in self.zones.keys() {
            self.save_zone(zone_id)?;
        }
        Ok(())
    }

    /// Load a zone cache from disk. Returns `None` if file doesn't exist
    /// or version mismatch (cache invalidation).
    fn load_zone(&self, zone_id: u32) -> Option<ZoneVoiceCache> {
        let path = self.zone_dir().join(format!("{}.msgpack", zone_id));
        let data = fs::read(&path).ok()?;
        let cache: ZoneVoiceCache = rmp_serde::from_slice(&data).ok()?;

        // Version check — invalidate on mismatch
        if cache.model_version != self.model_version
            || cache.injector_version != self.injector_version
        {
            tracing::info!(zone_id, "voice cache version mismatch — invalidating");
            return None;
        }

        tracing::debug!(zone_id, entries = cache.entries.len(), "loaded voice cache");
        Some(cache)
    }

    fn zone_dir(&self) -> PathBuf {
        self.base_dir.join(format!("{}", self.world_seed))
    }
}

impl Drop for VoiceCacheStore {
    fn drop(&mut self) {
        if let Err(e) = self.save_all() {
            tracing::warn!(error = %e, "failed to save voice cache on shutdown");
        }
    }
}

/// Determine which tell states should be cached for a given base text.
///
/// Length-gated variant count (Spike 1 finding):
/// - Short (≤7 words): neutral only — 2B model can't differentiate
/// - Medium (8–15 words): neutral + Angry + Guarded (3 variants)
/// - Long (16+ words): all 5 tells + neutral (6 variants)
pub fn cacheable_tells(base_text: &str) -> Vec<Option<TellCategory>> {
    let words = base_text.split_whitespace().count();
    if words <= 7 {
        vec![None] // neutral only
    } else if words <= 15 {
        vec![None, Some(TellCategory::Angry), Some(TellCategory::Guarded)]
    } else {
        vec![
            None,
            Some(TellCategory::Nervous),
            Some(TellCategory::Angry),
            Some(TellCategory::Friendly),
            Some(TellCategory::Guarded),
            Some(TellCategory::RoutineDeviation),
        ]
    }
}

// ---------------------------------------------------------------------------
// Make ContentType serializable for cache keys
// ---------------------------------------------------------------------------

impl Serialize for ContentType {
    fn serialize<S: serde::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        match self {
            ContentType::Dialogue => serializer.serialize_u8(0),
            ContentType::Behavior => serializer.serialize_u8(1),
            ContentType::Factual => serializer.serialize_u8(2),
        }
    }
}

impl<'de> Deserialize<'de> for ContentType {
    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        let v = u8::deserialize(deserializer)?;
        match v {
            0 => Ok(ContentType::Dialogue),
            1 => Ok(ContentType::Behavior),
            2 => Ok(ContentType::Factual),
            _ => Err(serde::de::Error::custom("invalid ContentType")),
        }
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

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

    #[test]
    fn zone_cache_store_and_lookup() {
        let mut cache = ZoneVoiceCache::new("v1".into(), "i1".into());
        let key = CacheKey {
            culture_id: "van-maanens-star".into(),
            npc_stable_id: 42,
            content_type: ContentType::Dialogue,
            content_index: 0,
            tell_state: None,
        };
        cache.store(key.clone(), "Look, that's not mine to say.".into());
        assert_eq!(cache.lookup(&key), Some("Look, that's not mine to say."));
    }

    #[test]
    fn zone_cache_miss_returns_none() {
        let cache = ZoneVoiceCache::new("v1".into(), "i1".into());
        let key = CacheKey {
            culture_id: "van-maanens-star".into(),
            npc_stable_id: 42,
            content_type: ContentType::Dialogue,
            content_index: 0,
            tell_state: None,
        };
        assert_eq!(cache.lookup(&key), None);
    }

    #[test]
    fn zone_cache_round_trips_through_msgpack() {
        let mut cache = ZoneVoiceCache::new("v1".into(), "i1".into());
        let key = CacheKey {
            culture_id: "van-maanens-star".into(),
            npc_stable_id: 42,
            content_type: ContentType::Behavior,
            content_index: 3,
            tell_state: Some(TellCategory::Nervous),
        };
        cache.store(key.clone(), "Hands are steady. Eyes aren't.".into());

        let data = rmp_serde::to_vec(&cache).unwrap();
        let restored: ZoneVoiceCache = rmp_serde::from_slice(&data).unwrap();
        assert_eq!(
            restored.lookup(&key),
            Some("Hands are steady. Eyes aren't.")
        );
        assert_eq!(restored.model_version, "v1");
    }

    #[test]
    fn cache_store_persists_and_loads() {
        let dir = std::env::temp_dir().join("sr-voice-cache-test");
        let _ = fs::remove_dir_all(&dir);

        let mut store = VoiceCacheStore::new(dir.clone(), 12345, "v1".into(), "i1".into());
        let key = CacheKey {
            culture_id: "van-maanens-star".into(),
            npc_stable_id: 1,
            content_type: ContentType::Dialogue,
            content_index: 0,
            tell_state: None,
        };
        store.store(100, key.clone(), "Hey.".into());
        store.save_zone(100).unwrap();

        // New store instance — loads from disk
        let mut store2 = VoiceCacheStore::new(dir.clone(), 12345, "v1".into(), "i1".into());
        assert_eq!(store2.lookup(100, &key), Some("Hey.".into()));

        let _ = fs::remove_dir_all(&dir);
    }

    #[test]
    fn cache_invalidation_on_version_mismatch() {
        let dir = std::env::temp_dir().join("sr-voice-cache-invalidation-test");
        let _ = fs::remove_dir_all(&dir);

        let mut store = VoiceCacheStore::new(dir.clone(), 42, "v1".into(), "i1".into());
        let key = CacheKey {
            culture_id: "van-maanens-star".into(),
            npc_stable_id: 1,
            content_type: ContentType::Dialogue,
            content_index: 0,
            tell_state: None,
        };
        store.store(1, key.clone(), "Old text.".into());
        store.save_zone(1).unwrap();

        // Different model version — should invalidate
        let mut store2 = VoiceCacheStore::new(dir.clone(), 42, "v2".into(), "i1".into());
        assert_eq!(store2.lookup(1, &key), None);

        let _ = fs::remove_dir_all(&dir);
    }

    #[test]
    fn cacheable_tells_short() {
        let tells = cacheable_tells("Hello there.");
        assert_eq!(tells.len(), 1);
        assert_eq!(tells[0], None);
    }

    #[test]
    fn cacheable_tells_medium() {
        let tells = cacheable_tells("The overnight delivery came in clean and it was logged");
        assert_eq!(tells.len(), 3);
    }

    #[test]
    fn cacheable_tells_long() {
        let tells = cacheable_tells(
            "I heard the night crew had to stop the line twice because the coupling was faulty and nobody had flagged it"
        );
        assert_eq!(tells.len(), 6);
    }
}