use rusqlite::params;

use crate::error::Result;
use crate::serde_helpers::serialize_f32;

use super::{now, YantrikDB};

impl YantrikDB {
    /// Archive a hot memory to cold storage (compress embedding, remove from vec index).
    /// Returns true if the memory was archived, false if not found or already cold.
    #[tracing::instrument(skip(self))]
    pub fn archive(&self, rid: &str) -> Result<bool> {
        let row = self.conn.query_row(
            "SELECT embedding FROM memories WHERE rid = ?1 AND storage_tier = 'hot' AND consolidation_status = 'active'",
            params![rid],
            |row| row.get::<_, Vec<u8>>(0),
        );

        let stored_blob = match row {
            Ok(blob) => blob,
            Err(rusqlite::Error::QueryReturnedNoRows) => return Ok(false),
            Err(e) => return Err(e.into()),
        };

        // Decrypt if encrypted, then compress, then re-encrypt for cold storage
        let raw_blob = self.decrypt_embedding(&stored_blob)?;
        let embedding = crate::serde_helpers::deserialize_f32(&raw_blob);
        let compressed = crate::compression::compress_embedding(&embedding);
        let stored_compressed = self.encrypt_embedding(&compressed)?;
        let ts = now();

        self.conn.execute(
            "UPDATE memories SET storage_tier = 'cold', embedding = ?1, updated_at = ?2 WHERE rid = ?3",
            params![stored_compressed, ts, rid],
        )?;

        self.vec_index.borrow_mut().remove(rid);

        self.log_op(
            "archive",
            Some(rid),
            &serde_json::json!({
                "rid": rid,
                "updated_at": ts,
            }),
            None,
        )?;

        Ok(true)
    }

    /// Hydrate a cold memory back to hot storage (decompress embedding, re-insert into vec index).
    /// Returns true if the memory was hydrated, false if not found or already hot.
    #[tracing::instrument(skip(self))]
    pub fn hydrate(&self, rid: &str) -> Result<bool> {
        let row = self.conn.query_row(
            "SELECT embedding FROM memories WHERE rid = ?1 AND storage_tier = 'cold'",
            params![rid],
            |row| row.get::<_, Vec<u8>>(0),
        );

        let stored_blob = match row {
            Ok(blob) => blob,
            Err(rusqlite::Error::QueryReturnedNoRows) => return Ok(false),
            Err(e) => return Err(e.into()),
        };

        // Decrypt if encrypted, decompress, then re-encrypt for hot storage
        let compressed_blob = self.decrypt_embedding(&stored_blob)?;
        let embedding = crate::compression::decompress_embedding(&compressed_blob);
        let raw_blob = serialize_f32(&embedding);
        let stored_raw = self.encrypt_embedding(&raw_blob)?;
        let ts = now();

        self.conn.execute(
            "UPDATE memories SET storage_tier = 'hot', embedding = ?1, updated_at = ?2 WHERE rid = ?3",
            params![stored_raw, ts, rid],
        )?;

        self.vec_index.borrow_mut().insert(rid, &embedding)?;

        self.log_op(
            "hydrate",
            Some(rid),
            &serde_json::json!({
                "rid": rid,
                "updated_at": ts,
            }),
            None,
        )?;

        Ok(true)
    }

    /// Evict memories to cold storage based on decay scores.
    /// Archives the lowest-scoring memories until at most `max_active` hot memories remain.
    /// Returns the list of archived RIDs.
    #[tracing::instrument(skip(self))]
    pub fn evict(&self, max_active: usize) -> Result<Vec<String>> {
        let hot_count: i64 = self.conn.query_row(
            "SELECT COUNT(*) FROM memories WHERE consolidation_status = 'active' AND storage_tier = 'hot'",
            [],
            |row| row.get(0),
        )?;

        if hot_count as usize <= max_active {
            return Ok(vec![]);
        }

        let to_evict = hot_count as usize - max_active;
        let ts = now();

        let mut stmt = self.conn.prepare(
            "SELECT rid, importance, half_life, last_access, created_at FROM memories \
             WHERE consolidation_status = 'active' AND storage_tier = 'hot'",
        )?;

        let mut scored: Vec<(String, f64)> = stmt
            .query_map([], |row| {
                let rid: String = row.get("rid")?;
                let importance: f64 = row.get("importance")?;
                let half_life: f64 = row.get("half_life")?;
                let last_access: f64 = row.get("last_access")?;
                let created_at: f64 = row.get("created_at")?;
                let elapsed = ts - last_access;
                let decay = crate::scoring::decay_score(importance, half_life, elapsed);
                let age = ts - created_at;
                let recency = crate::scoring::recency_score(age);
                let score = crate::scoring::eviction_score(decay, recency);
                Ok((rid, score))
            })?
            .collect::<std::result::Result<Vec<_>, _>>()?;

        // Sort ascending — lowest score = most evictable
        scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap_or(std::cmp::Ordering::Equal));

        let mut archived_rids = Vec::new();
        for (rid, _) in scored.into_iter().take(to_evict) {
            if self.archive(&rid)? {
                archived_rids.push(rid);
            }
        }

        Ok(archived_rids)
    }
}
