/**
 * React Hook for DuckDB-WASM Database Interaction
 * Provides in-browser OLAP database for analytics on heritage institution data
 */

import { useState, useEffect, useCallback, useRef } from 'react';
import type { AsyncDuckDB, AsyncDuckDBConnection, DuckDBBundles } from '@duckdb/duckdb-wasm';
import * as duckdb from '@duckdb/duckdb-wasm';

export interface DuckDBStats {
  totalTables: number;
  totalRows: number;
  tables: Array<{
    name: string;
    rowCount: number;
    columns: Array<{
      name: string;
      type: string;
    }>;
  }>;
  memoryUsageMB: number;
}

export interface DuckDBStatus {
  isConnected: boolean;
  version: string;
  lastChecked: Date | null;
  responseTimeMs?: number;
}

export interface UseDuckDBReturn {
  status: DuckDBStatus;
  stats: DuckDBStats | null;
  isLoading: boolean;
  error: Error | null;
  refresh: () => Promise<void>;
  executeQuery: (query: string) => Promise<unknown[]>;
  loadData: (tableName: string, data: unknown[], columns?: string[]) => Promise<void>;
  dropTable: (tableName: string) => Promise<void>;
  exportTable: (tableName: string, format?: 'json' | 'csv' | 'parquet') => Promise<string>;
  db: AsyncDuckDB | null;
}

// Local bundles for DuckDB-WASM (served from same origin to avoid CORS issues)
const DUCKDB_BUNDLES: DuckDBBundles = {
  mvp: {
    mainModule: '/duckdb/duckdb-mvp.wasm',
    mainWorker: '/duckdb/duckdb-browser-mvp.worker.js',
  },
  eh: {
    mainModule: '/duckdb/duckdb-eh.wasm',
    mainWorker: '/duckdb/duckdb-browser-eh.worker.js',
  },
};

/**
 * Hook for interacting with DuckDB-WASM in-browser database
 */
export function useDuckDB(): UseDuckDBReturn {
  const [db, setDb] = useState<AsyncDuckDB | null>(null);
  const [conn, setConn] = useState<AsyncDuckDBConnection | null>(null);
  const [status, setStatus] = useState<DuckDBStatus>({
    isConnected: false,
    version: '',
    lastChecked: null,
  });
  const [stats, setStats] = useState<DuckDBStats | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<Error | null>(null);
  
  const initializingRef = useRef(false);

  /**
   * Initialize DuckDB-WASM
   */
  const initDB = useCallback(async () => {
    if (initializingRef.current || db) return;
    initializingRef.current = true;

    const startTime = performance.now();
    
    try {
      // Select the best bundle for this browser
      const bundle = await duckdb.selectBundle(DUCKDB_BUNDLES);
      
      // Create worker and database
      const worker = new Worker(bundle.mainWorker!);
      const logger = new duckdb.ConsoleLogger(duckdb.LogLevel.WARNING);
      const database = new duckdb.AsyncDuckDB(logger, worker);
      
      await database.instantiate(bundle.mainModule);
      
      // Create connection
      const connection = await database.connect();
      
      // Get version
      const versionResult = await connection.query('SELECT version() as version');
      const version = versionResult.toArray()[0]?.version || 'unknown';
      
      const responseTimeMs = Math.round(performance.now() - startTime);
      
      setDb(database);
      setConn(connection);
      setStatus({
        isConnected: true,
        version,
        lastChecked: new Date(),
        responseTimeMs,
      });
      
    } catch (err) {
      console.error('Failed to initialize DuckDB:', err);
      setError(err instanceof Error ? err : new Error('Failed to initialize DuckDB'));
      setStatus({
        isConnected: false,
        version: '',
        lastChecked: new Date(),
      });
    } finally {
      setIsLoading(false);
      initializingRef.current = false;
    }
  }, [db]);

  // Initialize on mount
  useEffect(() => {
    initDB();
    
    // Cleanup on unmount
    return () => {
      conn?.close();
      db?.terminate();
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  /**
   * Refresh database statistics
   */
  const refresh = useCallback(async () => {
    if (!conn) return;
    
    setIsLoading(true);
    setError(null);
    
    const startTime = performance.now();
    
    try {
      // Get list of tables
      const tablesResult = await conn.query(`
        SELECT table_name 
        FROM information_schema.tables 
        WHERE table_schema = 'main'
      `);
      const tableNames = tablesResult.toArray().map((row: Record<string, unknown>) => row.table_name as string);
      
      // Get details for each table
      const tables = await Promise.all(tableNames.map(async (tableName: string) => {
        // Get row count
        const countResult = await conn.query(`SELECT COUNT(*) as cnt FROM "${tableName}"`);
        const rowCount = Number(countResult.toArray()[0]?.cnt || 0);
        
        // Get columns
        const columnsResult = await conn.query(`
          SELECT column_name, data_type 
          FROM information_schema.columns 
          WHERE table_name = '${tableName}' AND table_schema = 'main'
        `);
        const columns = columnsResult.toArray().map((row: Record<string, unknown>) => ({
          name: row.column_name as string,
          type: row.data_type as string,
        }));
        
        return { name: tableName, rowCount, columns };
      }));
      
      const totalRows = tables.reduce((sum: number, t: { rowCount: number }) => sum + t.rowCount, 0);
      
      const responseTimeMs = Math.round(performance.now() - startTime);
      
      setStats({
        totalTables: tables.length,
        totalRows,
        tables,
        memoryUsageMB: 0, // Memory tracking not easily available in WASM
      });
      
      setStatus(prev => ({
        ...prev,
        isConnected: true,
        lastChecked: new Date(),
        responseTimeMs,
      }));
      
    } catch (err) {
      console.error('Failed to refresh DuckDB stats:', err);
      setError(err instanceof Error ? err : new Error('Failed to refresh stats'));
    } finally {
      setIsLoading(false);
    }
  }, [conn]);

  // Refresh stats when connection is established
  useEffect(() => {
    if (conn && status.isConnected) {
      refresh();
    }
  }, [conn, status.isConnected, refresh]);

  /**
   * Execute a SQL query
   */
  const executeQuery = useCallback(async (query: string): Promise<unknown[]> => {
    if (!conn) throw new Error('DuckDB not initialized');
    
    const result = await conn.query(query);
    return result.toArray().map((row: Record<string, unknown> & { toJSON?: () => unknown }) => row.toJSON ? row.toJSON() : row);
  }, [conn]);

  /**
   * Load data into a table
   */
  const loadData = useCallback(async (
    tableName: string,
    data: unknown[],
    columns?: string[]
  ): Promise<void> => {
    if (!conn || !db) throw new Error('DuckDB not initialized');
    
    // Register JSON data as a file
    const jsonString = JSON.stringify(data);
    await db.registerFileText(`${tableName}.json`, jsonString);
    
    // Create table from JSON
    if (columns && columns.length > 0) {
      await conn.query(`
        CREATE OR REPLACE TABLE "${tableName}" AS 
        SELECT ${columns.join(', ')} 
        FROM read_json_auto('${tableName}.json')
      `);
    } else {
      await conn.query(`
        CREATE OR REPLACE TABLE "${tableName}" AS 
        SELECT * FROM read_json_auto('${tableName}.json')
      `);
    }
    
    await refresh();
  }, [conn, db, refresh]);

  /**
   * Drop a table
   */
  const dropTable = useCallback(async (tableName: string): Promise<void> => {
    if (!conn) throw new Error('DuckDB not initialized');
    
    await conn.query(`DROP TABLE IF EXISTS "${tableName}"`);
    await refresh();
  }, [conn, refresh]);

  /**
   * Export table data
   */
  const exportTable = useCallback(async (
    tableName: string,
    format: 'json' | 'csv' | 'parquet' = 'json'
  ): Promise<string> => {
    if (!conn) throw new Error('DuckDB not initialized');
    
    const result = await conn.query(`SELECT * FROM "${tableName}"`);
    const rows = result.toArray().map((row: Record<string, unknown> & { toJSON?: () => unknown }) => row.toJSON ? row.toJSON() : row);
    
    if (format === 'json') {
      return JSON.stringify(rows, null, 2);
    } else if (format === 'csv') {
      if (rows.length === 0) return '';
      const headers = Object.keys(rows[0] as object);
      const csvRows = rows.map((row: unknown) => 
        headers.map(h => JSON.stringify((row as Record<string, unknown>)[h] ?? '')).join(',')
      );
      return [headers.join(','), ...csvRows].join('\n');
    }
    
    // Parquet would require special handling - for now return JSON
    return JSON.stringify(rows, null, 2);
  }, [conn]);

  return {
    status,
    stats,
    isLoading,
    error,
    refresh,
    executeQuery,
    loadData,
    dropTable,
    exportTable,
    db,
  };
}