use sqlx::Row;
use std::sync::OnceLock;

use jieba_rs::Jieba;

use crate::memory::{MemoryCategory, MemoryEntry};

use super::StorageError;

fn jieba() -> &'static Jieba {
    static INSTANCE: OnceLock<Jieba> = OnceLock::new();
    INSTANCE.get_or_init(Jieba::new)
}

impl super::Storage {
    /// Store or update a memory entry (upsert by key).
    pub async fn upsert_memory(&self, entry: &MemoryEntry) -> Result<(), StorageError> {
        let category_str = entry.category.as_str();
        sqlx::query(
            r#"
            INSERT INTO memories (id, key, content, category, importance, session_id, created_at, updated_at)
            VALUES (?, ?, ?, ?, ?, ?, ?, ?)
            ON CONFLICT(key) DO UPDATE SET
                content = excluded.content,
                category = excluded.category,
                importance = excluded.importance,
                session_id = excluded.session_id,
                updated_at = excluded.updated_at
            "#,
        )
        .bind(&entry.id)
        .bind(&entry.key)
        .bind(&entry.content)
        .bind(category_str)
        .bind(entry.importance)
        .bind(&entry.session_id)
        .bind(&entry.created_at)
        .bind(&entry.updated_at)
        .execute(self.pool())
        .await?;
        Ok(())
    }

    /// Delete a memory entry by key.
    pub async fn delete_memory(&self, key: &str) -> Result<(), StorageError> {
        sqlx::query("DELETE FROM memories WHERE key = ?")
            .bind(key)
            .execute(self.pool())
            .await?;
        Ok(())
    }

    /// Search memories by keyword using FTS5.
    /// Falls back to LIKE query if FTS5 returns no results.
    pub async fn search_memories(
        &self,
        query: &str,
        category: Option<&MemoryCategory>,
        session_id: Option<&str>,
        limit: usize,
    ) -> Result<Vec<MemoryEntry>, StorageError> {
        // Build FTS5 query: segment with jieba, wrap each term in quotes, join with OR
        let fts_query = jieba()
            .cut(query, true)
            .into_iter()
            .filter(|w| w.len() > 1 || w.bytes().any(|b| b > 127))
            .map(|w| format!("\"{}\"", w.replace('"', "")))
            .collect::<Vec<_>>()
            .join(" OR ");

        let category_filter = category.map(|c| c.as_str());

        // Try FTS5 first
        let rows = sqlx::query(
            r#"
            SELECT m.id, m.key, m.content, m.category, m.importance,
                   m.session_id, m.created_at, m.updated_at
            FROM memory_fts f
            JOIN memories m ON f.rowid = m.rowid
            WHERE memory_fts MATCH ? AND (? IS NULL OR m.category = ?) AND (? IS NULL OR m.session_id = ?)
            ORDER BY rank
            LIMIT ?
            "#,
        )
        .bind(&fts_query)
        .bind(category_filter)
        .bind(category_filter)
        .bind(session_id)
        .bind(session_id)
        .bind(limit as i64)
        .fetch_all(self.pool())
        .await?;

        let mut entries = parse_memory_rows(&rows)?;

        // Fallback to term-based LIKE query if FTS5 returned nothing
        if entries.is_empty() {
            let terms: Vec<String> = jieba()
                .cut(query, true)
                .into_iter()
                .filter(|w| w.len() > 1 || w.bytes().any(|b| b > 127))
                .map(|w| w.replace(['%', '_'], ""))
                .collect();

            if !terms.is_empty() {
                let like_clauses = terms
                    .iter()
                    .map(|_| "(key LIKE ? OR content LIKE ?)")
                    .collect::<Vec<_>>()
                    .join(" OR ");

                let sql = format!(
                    r#"
                    SELECT id, key, content, category, importance,
                           session_id, created_at, updated_at
                    FROM memories
                    WHERE ({})
                      AND (? IS NULL OR category = ?)
                      AND (? IS NULL OR session_id = ?)
                    ORDER BY importance DESC, updated_at DESC
                    LIMIT ?
                    "#,
                    like_clauses
                );

                let mut query_builder = sqlx::query(&sql);
                for term in &terms {
                    let pattern = format!("%{}%", term);
                    query_builder = query_builder.bind(pattern.clone()).bind(pattern);
                }
                query_builder = query_builder
                    .bind(category_filter)
                    .bind(category_filter)
                    .bind(session_id)
                    .bind(session_id)
                    .bind(limit as i64);

                let rows = query_builder.fetch_all(self.pool()).await?;
                entries = parse_memory_rows(&rows)?;
            }
        }

        Ok(entries)
    }

    /// Retrieve memories within a time range, optionally filtered by keyword query.
    pub async fn search_memories_by_time(
        &self,
        since: i64,
        until: i64,
        query: Option<&str>,
        category: Option<&MemoryCategory>,
        session_id: Option<&str>,
        limit: usize,
    ) -> Result<Vec<MemoryEntry>, StorageError> {
        let category_filter = category.map(|c| c.as_str());
        let since_dt = chrono::DateTime::from_timestamp_millis(since)
            .unwrap_or_default()
            .to_rfc3339();
        let until_dt = chrono::DateTime::from_timestamp_millis(until)
            .unwrap_or_default()
            .to_rfc3339();

        let rows = if let Some(q) = query {
            let terms: Vec<String> = jieba()
                .cut(q, true)
                .into_iter()
                .filter(|w| w.len() > 1 || w.bytes().any(|b| b > 127))
                .map(|w| w.replace(['%', '_'], ""))
                .collect();

            if terms.is_empty() {
                return Ok(Vec::new());
            }

            let like_clauses = terms
                .iter()
                .map(|_| "(key LIKE ? OR content LIKE ?)")
                .collect::<Vec<_>>()
                .join(" OR ");

            let sql = format!(
                r#"
                SELECT id, key, content, category, importance,
                       session_id, created_at, updated_at
                FROM memories
                WHERE ({})
                  AND created_at >= ? AND created_at <= ?
                  AND (? IS NULL OR category = ?)
                  AND (? IS NULL OR session_id = ?)
                ORDER BY created_at DESC
                LIMIT ?
                "#,
                like_clauses
            );

            let mut query_builder = sqlx::query(&sql);
            for term in &terms {
                let pattern = format!("%{}%", term);
                query_builder = query_builder.bind(pattern.clone()).bind(pattern);
            }
            query_builder = query_builder
                .bind(&since_dt)
                .bind(&until_dt)
                .bind(category_filter)
                .bind(category_filter)
                .bind(session_id)
                .bind(session_id)
                .bind(limit as i64);

            query_builder.fetch_all(self.pool()).await?
        } else {
            sqlx::query(
                r#"
                SELECT id, key, content, category, importance,
                       session_id, created_at, updated_at
                FROM memories
                WHERE created_at >= ? AND created_at <= ?
                  AND (? IS NULL OR category = ?)
                  AND (? IS NULL OR session_id = ?)
                ORDER BY created_at DESC
                LIMIT ?
                "#,
            )
            .bind(&since_dt)
            .bind(&until_dt)
            .bind(category_filter)
            .bind(category_filter)
            .bind(session_id)
            .bind(session_id)
            .bind(limit as i64)
            .fetch_all(self.pool())
            .await?
        };

        parse_memory_rows(&rows)
    }

    /// Delete old timeline entries beyond retention period.
    pub async fn cleanup_old_timelines(&self, retention_days: u64) -> Result<u64, StorageError> {
        let cutoff = chrono::Utc::now() - chrono::Duration::days(retention_days as i64);
        let cutoff_str = cutoff.to_rfc3339();

        let result = sqlx::query(
            "DELETE FROM memories WHERE category = 'timeline' AND created_at < ?",
        )
        .bind(&cutoff_str)
        .execute(self.pool())
        .await?;

        Ok(result.rows_affected())
    }
}

fn parse_memory_rows(
    rows: &[sqlx::sqlite::SqliteRow],
) -> Result<Vec<MemoryEntry>, StorageError> {
    rows.iter()
        .map(|row| {
            Ok(MemoryEntry {
                id: row.try_get("id")?,
                key: row.try_get("key")?,
                content: row.try_get("content")?,
                category: MemoryCategory::from_str(&row.try_get::<String, _>("category")?)
                    .unwrap_or(MemoryCategory::Knowledge),
                importance: row.try_get::<f64, _>("importance")?,
                session_id: row.try_get::<Option<String>, _>("session_id")?,
                created_at: row.try_get("created_at")?,
                updated_at: row.try_get("updated_at")?,
            })
        })
        .collect()
}