//! Persistent Memory Storage - SQLite-backed memory for ZCLAW
//!
//! This module provides persistent storage for agent memories,
//! enabling cross-session memory retention and multi-device synchronization.
//!
//! Phase 1 of Intelligence Layer Migration:
//! - Replaces localStorage with SQLite
//! - Provides memory persistence API
//! - Enables data migration from frontend

use serde::{Deserialize, Serialize};
use std::path::PathBuf;
use std::sync::Arc;
use tokio::sync::Mutex;
use uuid::Uuid;
use tauri::Manager;
use sqlx::{SqliteConnection, Connection, Row, sqlite::SqliteRow};
use chrono::{DateTime, Utc};

/// Memory entry stored in SQLite
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PersistentMemory {
    pub id: String,
    pub agent_id: String,
    pub memory_type: String,
    pub content: String,
    pub importance: i32,
    pub source: String,
    pub tags: String, // JSON array stored as string
    pub conversation_id: Option<String>,
    pub created_at: String,
    pub last_accessed_at: String,
    pub access_count: i32,
    pub embedding: Option<Vec<u8>>, // Vector embedding for semantic search
}

// Manual implementation of FromRow since sqlx::FromRow derive has issues with Option<Vec<u8>>
impl<'r> sqlx::FromRow<'r, SqliteRow> for PersistentMemory {
    fn from_row(row: &'r SqliteRow) -> Result<Self, sqlx::Error> {
        Ok(PersistentMemory {
            id: row.try_get("id")?,
            agent_id: row.try_get("agent_id")?,
            memory_type: row.try_get("memory_type")?,
            content: row.try_get("content")?,
            importance: row.try_get("importance")?,
            source: row.try_get("source")?,
            tags: row.try_get("tags")?,
            conversation_id: row.try_get("conversation_id")?,
            created_at: row.try_get("created_at")?,
            last_accessed_at: row.try_get("last_accessed_at")?,
            access_count: row.try_get("access_count")?,
            embedding: row.try_get("embedding")?,
        })
    }
}

/// Memory search options
#[derive(Debug, Clone)]
pub struct MemorySearchQuery {
    pub agent_id: Option<String>,
    pub memory_type: Option<String>,
    pub tags: Option<Vec<String>>,
    pub query: Option<String>,
    pub min_importance: Option<i32>,
    pub limit: Option<usize>,
    pub offset: Option<usize>,
}

/// Memory statistics
#[derive(Debug, Clone, Serialize)]
pub struct MemoryStats {
    pub total_entries: i64,
    pub by_type: std::collections::HashMap<String, i64>,
    pub by_agent: std::collections::HashMap<String, i64>,
    pub oldest_entry: Option<String>,
    pub newest_entry: Option<String>,
    pub storage_size_bytes: i64,
}

/// Persistent memory store backed by SQLite
pub struct PersistentMemoryStore {
    path: PathBuf,
    conn: Arc<Mutex<SqliteConnection>>,
}

impl PersistentMemoryStore {
    /// Create a new persistent memory store
    pub async fn new(app_handle: &tauri::AppHandle) -> Result<Self, String> {
        let app_dir = app_handle
            .path()
            .app_data_dir()
            .map_err(|e| format!("Failed to get app data dir: {}", e))?;

        let memory_dir = app_dir.join("memory");
        std::fs::create_dir_all(&memory_dir)
            .map_err(|e| format!("Failed to create memory dir: {}", e))?;

        let db_path = memory_dir.join("memories.db");

        Self::open(db_path).await
    }

    /// Open an existing memory store
    pub async fn open(path: PathBuf) -> Result<Self, String> {
        let db_url = format!("sqlite:{}?mode=rwc", path.display());
        let conn = SqliteConnection::connect(&db_url)
            .await
            .map_err(|e| format!("Failed to open database: {}", e))?;

        let conn = Arc::new(Mutex::new(conn));

        let store = Self { path, conn };

        // Initialize database schema
        store.init_schema().await?;

        Ok(store)
    }

    /// Initialize the database schema
    async fn init_schema(&self) -> Result<(), String> {
        let mut conn = self.conn.lock().await;

        sqlx::query(
            r#"
            CREATE TABLE IF NOT EXISTS memories (
                id TEXT PRIMARY KEY,
                agent_id TEXT NOT NULL,
                memory_type TEXT NOT NULL,
                content TEXT NOT NULL,
                importance INTEGER DEFAULT 5,
                source TEXT DEFAULT 'auto',
                tags TEXT DEFAULT '[]',
                conversation_id TEXT,
                created_at TEXT NOT NULL,
                last_accessed_at TEXT NOT NULL,
                access_count INTEGER DEFAULT 0,
                embedding BLOB
            );

            CREATE INDEX IF NOT EXISTS idx_agent_id ON memories(agent_id);
            CREATE INDEX IF NOT EXISTS idx_memory_type ON memories(memory_type);
            CREATE INDEX IF NOT EXISTS idx_created_at ON memories(created_at);
            CREATE INDEX IF NOT EXISTS idx_importance ON memories(importance);
            "#,
        )
        .execute(&mut *conn)
        .await
        .map_err(|e| format!("Failed to create schema: {}", e))?;

        Ok(())
    }

    /// Store a new memory
    pub async fn store(&self, memory: &PersistentMemory) -> Result<(), String> {
        let mut conn = self.conn.lock().await;

        sqlx::query(
            r#"
            INSERT INTO memories (
                id, agent_id, memory_type, content, importance, source,
                tags, conversation_id, created_at, last_accessed_at,
                access_count, embedding
            ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
            "#,
        )
        .bind(&memory.id)
        .bind(&memory.agent_id)
        .bind(&memory.memory_type)
        .bind(&memory.content)
        .bind(memory.importance)
        .bind(&memory.source)
        .bind(&memory.tags)
        .bind(&memory.conversation_id)
        .bind(&memory.created_at)
        .bind(&memory.last_accessed_at)
        .bind(memory.access_count)
        .bind(&memory.embedding)
        .execute(&mut *conn)
        .await
        .map_err(|e| format!("Failed to store memory: {}", e))?;

        Ok(())
    }

    /// Get a memory by ID
    pub async fn get(&self, id: &str) -> Result<Option<PersistentMemory>, String> {
        let mut conn = self.conn.lock().await;

        let result: Option<PersistentMemory> = sqlx::query_as(
            "SELECT * FROM memories WHERE id = ?",
        )
        .bind(id)
        .fetch_optional(&mut *conn)
        .await
        .map_err(|e| format!("Failed to get memory: {}", e))?;

        // Update access stats if found
        if result.is_some() {
            let now = Utc::now().to_rfc3339();
            sqlx::query(
                "UPDATE memories SET last_accessed_at = ?, access_count = access_count + 1 WHERE id = ?",
            )
            .bind(&now)
            .bind(id)
            .execute(&mut *conn)
            .await
            .ok();
        }

        Ok(result)
    }

    /// Search memories with simple query
    pub async fn search(&self, query: MemorySearchQuery) -> Result<Vec<PersistentMemory>, String> {
        let mut conn = self.conn.lock().await;

        let mut sql = String::from("SELECT * FROM memories WHERE 1=1");
        let mut params: Vec<String> = Vec::new();

        if let Some(agent_id) = &query.agent_id {
            sql.push_str(" AND agent_id = ?");
            params.push(agent_id.clone());
        }

        if let Some(memory_type) = &query.memory_type {
            sql.push_str(" AND memory_type = ?");
            params.push(memory_type.clone());
        }

        if let Some(min_importance) = query.min_importance {
            sql.push_str(" AND importance >= ?");
            params.push(min_importance.to_string());
        }

        if let Some(query_text) = &query.query {
            sql.push_str(" AND content LIKE ?");
            params.push(format!("%{}%", query_text));
        }

        sql.push_str(" ORDER BY created_at DESC");

        if let Some(limit) = query.limit {
            sql.push_str(&format!(" LIMIT {}", limit));
        }

        if let Some(offset) = query.offset {
            sql.push_str(&format!(" OFFSET {}", offset));
        }

        // Build and execute query dynamically
        let mut query_builder = sqlx::query_as::<_, PersistentMemory>(&sql);
        for param in params {
            query_builder = query_builder.bind(param);
        }

        let results = query_builder
            .fetch_all(&mut *conn)
            .await
            .map_err(|e| format!("Failed to search memories: {}", e))?;

        Ok(results)
    }

    /// Delete a memory by ID
    pub async fn delete(&self, id: &str) -> Result<bool, String> {
        let mut conn = self.conn.lock().await;

        let result = sqlx::query("DELETE FROM memories WHERE id = ?")
            .bind(id)
            .execute(&mut *conn)
            .await
            .map_err(|e| format!("Failed to delete memory: {}", e))?;

        Ok(result.rows_affected() > 0)
    }

    /// Delete all memories for an agent
    pub async fn delete_by_agent(&self, agent_id: &str) -> Result<usize, String> {
        let mut conn = self.conn.lock().await;

        let result = sqlx::query("DELETE FROM memories WHERE agent_id = ?")
            .bind(agent_id)
            .execute(&mut *conn)
            .await
            .map_err(|e| format!("Failed to delete agent memories: {}", e))?;

        Ok(result.rows_affected() as usize)
    }

    /// Get memory statistics
    pub async fn stats(&self) -> Result<MemoryStats, String> {
        let mut conn = self.conn.lock().await;

        let total: i64 = sqlx::query_scalar("SELECT COUNT(*) FROM memories")
            .fetch_one(&mut *conn)
            .await
            .unwrap_or(0);

        let by_type: std::collections::HashMap<String, i64> = sqlx::query_as(
            "SELECT memory_type, COUNT(*) as count FROM memories GROUP BY memory_type",
        )
        .fetch_all(&mut *conn)
        .await
        .unwrap_or_default()
        .into_iter()
        .map(|row: (String, i64)| row)
        .collect();

        let by_agent: std::collections::HashMap<String, i64> = sqlx::query_as(
            "SELECT agent_id, COUNT(*) as count FROM memories GROUP BY agent_id",
        )
        .fetch_all(&mut *conn)
        .await
        .unwrap_or_default()
        .into_iter()
        .map(|row: (String, i64)| row)
        .collect();

        let oldest: Option<String> = sqlx::query_scalar(
            "SELECT MIN(created_at) FROM memories",
        )
        .fetch_optional(&mut *conn)
        .await
        .unwrap_or_default();

        let newest: Option<String> = sqlx::query_scalar(
            "SELECT MAX(created_at) FROM memories",
        )
        .fetch_optional(&mut *conn)
        .await
        .unwrap_or_default();

        let storage_size: i64 = sqlx::query_scalar(
            "SELECT SUM(LENGTH(content) + LENGTH(tags) + COALESCE(LENGTH(embedding), 0)) FROM memories",
        )
        .fetch_optional(&mut *conn)
        .await
        .unwrap_or(Some(0))
        .unwrap_or(0);

        Ok(MemoryStats {
            total_entries: total,
            by_type,
            by_agent,
            oldest_entry: oldest,
            newest_entry: newest,
            storage_size_bytes: storage_size,
        })
    }

    /// Export memories for backup
    pub async fn export_all(&self) -> Result<Vec<PersistentMemory>, String> {
        let mut conn = self.conn.lock().await;

        let memories = sqlx::query_as::<_, PersistentMemory>(
            "SELECT * FROM memories ORDER BY created_at ASC",
        )
        .fetch_all(&mut *conn)
        .await
        .map_err(|e| format!("Failed to export memories: {}", e))?;

        Ok(memories)
    }

    /// Import memories from backup
    pub async fn import_batch(&self, memories: &[PersistentMemory]) -> Result<usize, String> {
        let mut imported = 0;
        for memory in memories {
            self.store(memory).await?;
            imported += 1;
        }
        Ok(imported)
    }

    /// Get the database path
    pub fn path(&self) -> &PathBuf {
        &self.path
    }
}

/// Generate a unique memory ID
pub fn generate_memory_id() -> String {
    let uuid_str = Uuid::new_v4().to_string().replace("-", "");
    let short_uuid = &uuid_str[..8];
    format!("mem_{}_{}", Utc::now().timestamp(), short_uuid)
}

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

    #[test]
    fn test_generate_memory_id() {
        let memory_id = generate_memory_id();
        assert!(memory_id.starts_with("mem_"));
    }
}