/**
 * Paper Trading Service
 * Simulates trading with virtual funds using PostgreSQL
 */

import { db } from '../../../shared/database';
import { marketService } from './market.service';
import { logger } from '../../../shared/utils/logger';

// ============================================================================
// Types (matching trading.paper_trading_accounts and paper_trading_positions)
// ============================================================================

export type TradeDirection = 'long' | 'short';
export type PositionStatus = 'open' | 'closed' | 'pending';

export interface PaperAccount {
  id: string;
  userId: string;
  name: string;
  initialBalance: number;
  currentBalance: number;
  currency: string;
  totalTrades: number;
  winningTrades: number;
  totalPnl: number;
  maxDrawdown: number;
  isActive: boolean;
  createdAt: Date;
  updatedAt: Date;
}

export interface PaperPosition {
  id: string;
  accountId: string;
  userId: string;
  symbol: string;
  direction: TradeDirection;
  lotSize: number;
  entryPrice: number;
  stopLoss?: number;
  takeProfit?: number;
  exitPrice?: number;
  status: PositionStatus;
  openedAt: Date;
  closedAt?: Date;
  closeReason?: string;
  realizedPnl?: number;
  createdAt: Date;
  updatedAt: Date;
  // Calculated fields
  currentPrice?: number;
  unrealizedPnl?: number;
  unrealizedPnlPercent?: number;
}

export interface CreateAccountInput {
  name?: string;
  initialBalance?: number;
  currency?: string;
}

export interface CreatePositionInput {
  symbol: string;
  direction: TradeDirection;
  lotSize: number;
  entryPrice?: number; // If not provided, uses market price
  stopLoss?: number;
  takeProfit?: number;
}

export interface ClosePositionInput {
  exitPrice?: number; // If not provided, uses market price
  closeReason?: string;
}

export interface AccountSummary {
  account: PaperAccount;
  openPositions: number;
  totalEquity: number;
  unrealizedPnl: number;
  todayPnl: number;
  winRate: number;
}

// ============================================================================
// Helper Functions
// ============================================================================

function mapAccount(row: Record<string, unknown>): PaperAccount {
  return {
    id: row.id as string,
    userId: row.user_id as string,
    name: row.name as string,
    initialBalance: parseFloat(row.initial_balance as string),
    currentBalance: parseFloat(row.current_balance as string),
    currency: (row.currency as string).trim(),
    totalTrades: row.total_trades as number,
    winningTrades: row.winning_trades as number,
    totalPnl: parseFloat(row.total_pnl as string),
    maxDrawdown: parseFloat(row.max_drawdown as string),
    isActive: row.is_active as boolean,
    createdAt: new Date(row.created_at as string),
    updatedAt: new Date(row.updated_at as string),
  };
}

function mapPosition(row: Record<string, unknown>): PaperPosition {
  return {
    id: row.id as string,
    accountId: row.account_id as string,
    userId: row.user_id as string,
    symbol: row.symbol as string,
    direction: row.direction as TradeDirection,
    lotSize: parseFloat(row.lot_size as string),
    entryPrice: parseFloat(row.entry_price as string),
    stopLoss: row.stop_loss ? parseFloat(row.stop_loss as string) : undefined,
    takeProfit: row.take_profit ? parseFloat(row.take_profit as string) : undefined,
    exitPrice: row.exit_price ? parseFloat(row.exit_price as string) : undefined,
    status: row.status as PositionStatus,
    openedAt: new Date(row.opened_at as string),
    closedAt: row.closed_at ? new Date(row.closed_at as string) : undefined,
    closeReason: row.close_reason as string | undefined,
    realizedPnl: row.realized_pnl ? parseFloat(row.realized_pnl as string) : undefined,
    createdAt: new Date(row.created_at as string),
    updatedAt: new Date(row.updated_at as string),
  };
}

// ============================================================================
// Paper Trading Service
// ============================================================================

class PaperTradingService {
  // ==========================================================================
  // Account Management
  // ==========================================================================

  /**
   * Get or create default paper trading account for user
   */
  async getOrCreateAccount(userId: string): Promise<PaperAccount> {
    // Try to find existing active account
    const existing = await db.query<Record<string, unknown>>(
      `SELECT * FROM trading.paper_trading_accounts
       WHERE user_id = $1 AND is_active = TRUE
       ORDER BY created_at DESC LIMIT 1`,
      [userId]
    );

    if (existing.rows.length > 0) {
      return mapAccount(existing.rows[0]);
    }

    // Create new account with default $100,000
    return this.createAccount(userId, {});
  }

  /**
   * Create a new paper trading account
   */
  async createAccount(userId: string, input: CreateAccountInput): Promise<PaperAccount> {
    const result = await db.query<Record<string, unknown>>(
      `INSERT INTO trading.paper_trading_accounts
       (user_id, name, initial_balance, current_balance, currency)
       VALUES ($1, $2, $3, $3, $4)
       RETURNING *`,
      [
        userId,
        input.name || 'Paper Account',
        input.initialBalance || 100000,
        input.currency || 'USD',
      ]
    );

    logger.info('[PaperTrading] Account created:', {
      userId,
      accountId: result.rows[0].id,
      initialBalance: input.initialBalance || 100000,
    });

    return mapAccount(result.rows[0]);
  }

  /**
   * Get account by ID
   */
  async getAccount(accountId: string, userId: string): Promise<PaperAccount | null> {
    const result = await db.query<Record<string, unknown>>(
      `SELECT * FROM trading.paper_trading_accounts WHERE id = $1 AND user_id = $2`,
      [accountId, userId]
    );
    if (result.rows.length === 0) return null;
    return mapAccount(result.rows[0]);
  }

  /**
   * Get all accounts for user
   */
  async getUserAccounts(userId: string): Promise<PaperAccount[]> {
    const result = await db.query<Record<string, unknown>>(
      `SELECT * FROM trading.paper_trading_accounts
       WHERE user_id = $1
       ORDER BY created_at DESC`,
      [userId]
    );
    return result.rows.map(mapAccount);
  }

  /**
   * Reset account to initial state
   */
  async resetAccount(accountId: string, userId: string): Promise<PaperAccount | null> {
    const client = await db.getClient();
    try {
      await client.query('BEGIN');

      // Get account
      const accountResult = await client.query<Record<string, unknown>>(
        `SELECT * FROM trading.paper_trading_accounts WHERE id = $1 AND user_id = $2`,
        [accountId, userId]
      );

      if (accountResult.rows.length === 0) {
        await client.query('ROLLBACK');
        return null;
      }

      // Close all open positions
      await client.query(
        `UPDATE trading.paper_trading_positions
         SET status = 'closed', closed_at = NOW(), close_reason = 'account_reset'
         WHERE account_id = $1 AND status = 'open'`,
        [accountId]
      );

      // Reset account
      const result = await client.query<Record<string, unknown>>(
        `UPDATE trading.paper_trading_accounts
         SET current_balance = initial_balance,
             total_trades = 0,
             winning_trades = 0,
             total_pnl = 0,
             max_drawdown = 0,
             updated_at = NOW()
         WHERE id = $1
         RETURNING *`,
        [accountId]
      );

      await client.query('COMMIT');

      logger.info('[PaperTrading] Account reset:', { accountId, userId });
      return mapAccount(result.rows[0]);
    } catch (error) {
      await client.query('ROLLBACK');
      throw error;
    } finally {
      client.release();
    }
  }

  // ==========================================================================
  // Position Management
  // ==========================================================================

  /**
   * Open a new position
   */
  async openPosition(userId: string, input: CreatePositionInput): Promise<PaperPosition> {
    // Get or create account
    const account = await this.getOrCreateAccount(userId);

    // Get market price if not provided
    let entryPrice = input.entryPrice;
    if (!entryPrice) {
      try {
        const priceData = await marketService.getPrice(input.symbol);
        entryPrice = priceData.price;
      } catch {
        throw new Error(`Could not get price for ${input.symbol}`);
      }
    }

    // Calculate required margin (simplified: lot_size * entry_price)
    const requiredMargin = input.lotSize * entryPrice;
    if (requiredMargin > account.currentBalance) {
      throw new Error(
        `Insufficient balance. Required: ${requiredMargin.toFixed(2)}, Available: ${account.currentBalance.toFixed(2)}`
      );
    }

    const client = await db.getClient();
    try {
      await client.query('BEGIN');

      // Create position
      const result = await client.query<Record<string, unknown>>(
        `INSERT INTO trading.paper_trading_positions
         (account_id, user_id, symbol, direction, lot_size, entry_price, stop_loss, take_profit)
         VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
         RETURNING *`,
        [
          account.id,
          userId,
          input.symbol.toUpperCase(),
          input.direction,
          input.lotSize,
          entryPrice,
          input.stopLoss || null,
          input.takeProfit || null,
        ]
      );

      // Deduct margin from balance
      await client.query(
        `UPDATE trading.paper_trading_accounts
         SET current_balance = current_balance - $1,
             updated_at = NOW()
         WHERE id = $2`,
        [requiredMargin, account.id]
      );

      await client.query('COMMIT');

      logger.info('[PaperTrading] Position opened:', {
        positionId: result.rows[0].id,
        userId,
        symbol: input.symbol,
        direction: input.direction,
        lotSize: input.lotSize,
        entryPrice,
      });

      return mapPosition(result.rows[0]);
    } catch (error) {
      await client.query('ROLLBACK');
      throw error;
    } finally {
      client.release();
    }
  }

  /**
   * Close a position
   */
  async closePosition(
    positionId: string,
    userId: string,
    input: ClosePositionInput = {}
  ): Promise<PaperPosition | null> {
    const client = await db.getClient();
    try {
      await client.query('BEGIN');

      // Get position
      const positionResult = await client.query<Record<string, unknown>>(
        `SELECT * FROM trading.paper_trading_positions
         WHERE id = $1 AND user_id = $2 AND status = 'open'`,
        [positionId, userId]
      );

      if (positionResult.rows.length === 0) {
        await client.query('ROLLBACK');
        return null;
      }

      const position = mapPosition(positionResult.rows[0]);

      // Get exit price
      let exitPrice = input.exitPrice;
      if (!exitPrice) {
        try {
          const priceData = await marketService.getPrice(position.symbol);
          exitPrice = priceData.price;
        } catch {
          throw new Error(`Could not get price for ${position.symbol}`);
        }
      }

      // Calculate P&L
      const priceDiff = exitPrice - position.entryPrice;
      const realizedPnl =
        position.direction === 'long'
          ? priceDiff * position.lotSize
          : -priceDiff * position.lotSize;

      // Update position
      const result = await client.query<Record<string, unknown>>(
        `UPDATE trading.paper_trading_positions
         SET status = 'closed',
             exit_price = $1,
             closed_at = NOW(),
             close_reason = $2,
             realized_pnl = $3,
             updated_at = NOW()
         WHERE id = $4
         RETURNING *`,
        [exitPrice, input.closeReason || 'manual', realizedPnl, positionId]
      );

      // Update account balance and stats
      const marginReturn = position.lotSize * position.entryPrice;
      const isWin = realizedPnl > 0;

      await client.query(
        `UPDATE trading.paper_trading_accounts
         SET current_balance = current_balance + $1 + $2,
             total_trades = total_trades + 1,
             winning_trades = winning_trades + $3,
             total_pnl = total_pnl + $2,
             updated_at = NOW()
         WHERE id = $4`,
        [marginReturn, realizedPnl, isWin ? 1 : 0, position.accountId]
      );

      // Update max drawdown if needed
      await this.updateMaxDrawdown(client, position.accountId);

      await client.query('COMMIT');

      logger.info('[PaperTrading] Position closed:', {
        positionId,
        userId,
        exitPrice,
        realizedPnl,
      });

      return mapPosition(result.rows[0]);
    } catch (error) {
      await client.query('ROLLBACK');
      throw error;
    } finally {
      client.release();
    }
  }

  /**
   * Get position by ID
   */
  async getPosition(positionId: string, userId: string): Promise<PaperPosition | null> {
    const result = await db.query<Record<string, unknown>>(
      `SELECT * FROM trading.paper_trading_positions WHERE id = $1 AND user_id = $2`,
      [positionId, userId]
    );

    if (result.rows.length === 0) return null;

    const position = mapPosition(result.rows[0]);

    // Add current price and unrealized P&L for open positions
    if (position.status === 'open') {
      await this.enrichPositionWithMarketData(position);
    }

    return position;
  }

  /**
   * Get user positions
   */
  async getPositions(
    userId: string,
    options: { accountId?: string; status?: PositionStatus; symbol?: string; limit?: number } = {}
  ): Promise<PaperPosition[]> {
    const conditions: string[] = ['user_id = $1'];
    const params: (string | number)[] = [userId];
    let paramIndex = 2;

    if (options.accountId) {
      conditions.push(`account_id = $${paramIndex++}`);
      params.push(options.accountId);
    }
    if (options.status) {
      conditions.push(`status = $${paramIndex++}`);
      params.push(options.status);
    }
    if (options.symbol) {
      conditions.push(`symbol = $${paramIndex++}`);
      params.push(options.symbol.toUpperCase());
    }

    let query = `SELECT * FROM trading.paper_trading_positions
                 WHERE ${conditions.join(' AND ')}
                 ORDER BY opened_at DESC`;

    if (options.limit) {
      query += ` LIMIT $${paramIndex}`;
      params.push(options.limit);
    }

    const result = await db.query<Record<string, unknown>>(query, params);
    const positions = result.rows.map(mapPosition);

    // Enrich open positions with market data
    for (const position of positions) {
      if (position.status === 'open') {
        await this.enrichPositionWithMarketData(position);
      }
    }

    return positions;
  }

  /**
   * Update position stop loss / take profit
   */
  async updatePosition(
    positionId: string,
    userId: string,
    updates: { stopLoss?: number; takeProfit?: number }
  ): Promise<PaperPosition | null> {
    const fields: string[] = [];
    const params: (string | number | null)[] = [];
    let paramIndex = 1;

    if (updates.stopLoss !== undefined) {
      fields.push(`stop_loss = $${paramIndex++}`);
      params.push(updates.stopLoss);
    }
    if (updates.takeProfit !== undefined) {
      fields.push(`take_profit = $${paramIndex++}`);
      params.push(updates.takeProfit);
    }

    if (fields.length === 0) {
      return this.getPosition(positionId, userId);
    }

    fields.push(`updated_at = NOW()`);
    params.push(positionId, userId);

    const result = await db.query<Record<string, unknown>>(
      `UPDATE trading.paper_trading_positions
       SET ${fields.join(', ')}
       WHERE id = $${paramIndex++} AND user_id = $${paramIndex} AND status = 'open'
       RETURNING *`,
      params
    );

    if (result.rows.length === 0) return null;
    return mapPosition(result.rows[0]);
  }

  // ==========================================================================
  // Account Summary & Analytics
  // ==========================================================================

  /**
   * Get account summary with live data
   */
  async getAccountSummary(userId: string, accountId?: string): Promise<AccountSummary | null> {
    // Get account
    let account: PaperAccount | null;
    if (accountId) {
      account = await this.getAccount(accountId, userId);
    } else {
      account = await this.getOrCreateAccount(userId);
    }

    if (!account) return null;

    // Get open positions
    const openPositions = await this.getPositions(userId, {
      accountId: account.id,
      status: 'open',
    });

    // Calculate unrealized P&L
    let unrealizedPnl = 0;
    for (const position of openPositions) {
      unrealizedPnl += position.unrealizedPnl || 0;
    }

    // Calculate total equity
    const totalEquity = account.currentBalance + unrealizedPnl;

    // Calculate today's P&L
    const todayStart = new Date();
    todayStart.setHours(0, 0, 0, 0);

    const todayResult = await db.query<{ today_pnl: string }>(
      `SELECT COALESCE(SUM(realized_pnl), 0) as today_pnl
       FROM trading.paper_trading_positions
       WHERE account_id = $1 AND closed_at >= $2`,
      [account.id, todayStart.toISOString()]
    );
    const todayPnl = parseFloat(todayResult.rows[0].today_pnl) + unrealizedPnl;

    // Calculate win rate
    const winRate = account.totalTrades > 0
      ? (account.winningTrades / account.totalTrades) * 100
      : 0;

    return {
      account,
      openPositions: openPositions.length,
      totalEquity,
      unrealizedPnl,
      todayPnl,
      winRate,
    };
  }

  /**
   * Get trade history
   */
  async getTradeHistory(
    userId: string,
    options: {
      accountId?: string;
      symbol?: string;
      startDate?: Date;
      endDate?: Date;
      limit?: number;
    } = {}
  ): Promise<PaperPosition[]> {
    const conditions: string[] = ['user_id = $1', "status = 'closed'"];
    const params: (string | number)[] = [userId];
    let paramIndex = 2;

    if (options.accountId) {
      conditions.push(`account_id = $${paramIndex++}`);
      params.push(options.accountId);
    }
    if (options.symbol) {
      conditions.push(`symbol = $${paramIndex++}`);
      params.push(options.symbol.toUpperCase());
    }
    if (options.startDate) {
      conditions.push(`closed_at >= $${paramIndex++}`);
      params.push(options.startDate.toISOString());
    }
    if (options.endDate) {
      conditions.push(`closed_at <= $${paramIndex++}`);
      params.push(options.endDate.toISOString());
    }

    let query = `SELECT * FROM trading.paper_trading_positions
                 WHERE ${conditions.join(' AND ')}
                 ORDER BY closed_at DESC`;

    if (options.limit) {
      query += ` LIMIT $${paramIndex}`;
      params.push(options.limit);
    }

    const result = await db.query<Record<string, unknown>>(query, params);
    return result.rows.map(mapPosition);
  }

  /**
   * Get performance statistics
   */
  async getPerformanceStats(
    userId: string,
    accountId?: string
  ): Promise<{
    totalTrades: number;
    winningTrades: number;
    losingTrades: number;
    winRate: number;
    totalPnl: number;
    averageWin: number;
    averageLoss: number;
    largestWin: number;
    largestLoss: number;
    profitFactor: number;
  }> {
    const account = accountId
      ? await this.getAccount(accountId, userId)
      : await this.getOrCreateAccount(userId);

    if (!account) {
      throw new Error('Account not found');
    }

    const result = await db.query<Record<string, string>>(
      `SELECT
        COUNT(*) as total_trades,
        COUNT(*) FILTER (WHERE realized_pnl > 0) as winning_trades,
        COUNT(*) FILTER (WHERE realized_pnl <= 0) as losing_trades,
        COALESCE(SUM(realized_pnl), 0) as total_pnl,
        COALESCE(AVG(realized_pnl) FILTER (WHERE realized_pnl > 0), 0) as avg_win,
        COALESCE(AVG(realized_pnl) FILTER (WHERE realized_pnl <= 0), 0) as avg_loss,
        COALESCE(MAX(realized_pnl), 0) as largest_win,
        COALESCE(MIN(realized_pnl), 0) as largest_loss,
        COALESCE(SUM(realized_pnl) FILTER (WHERE realized_pnl > 0), 0) as gross_profit,
        COALESCE(ABS(SUM(realized_pnl) FILTER (WHERE realized_pnl < 0)), 1) as gross_loss
       FROM trading.paper_trading_positions
       WHERE account_id = $1 AND status = 'closed'`,
      [account.id]
    );

    const stats = result.rows[0];
    const totalTrades = parseInt(stats.total_trades, 10);
    const winningTrades = parseInt(stats.winning_trades, 10);
    const grossProfit = parseFloat(stats.gross_profit);
    const grossLoss = parseFloat(stats.gross_loss);

    return {
      totalTrades,
      winningTrades,
      losingTrades: parseInt(stats.losing_trades, 10),
      winRate: totalTrades > 0 ? (winningTrades / totalTrades) * 100 : 0,
      totalPnl: parseFloat(stats.total_pnl),
      averageWin: parseFloat(stats.avg_win),
      averageLoss: parseFloat(stats.avg_loss),
      largestWin: parseFloat(stats.largest_win),
      largestLoss: parseFloat(stats.largest_loss),
      profitFactor: grossLoss > 0 ? grossProfit / grossLoss : grossProfit > 0 ? Infinity : 0,
    };
  }

  // ==========================================================================
  // Private Helpers
  // ==========================================================================

  private async enrichPositionWithMarketData(position: PaperPosition): Promise<void> {
    try {
      const priceData = await marketService.getPrice(position.symbol);
      position.currentPrice = priceData.price;

      const priceDiff = priceData.price - position.entryPrice;
      position.unrealizedPnl =
        position.direction === 'long'
          ? priceDiff * position.lotSize
          : -priceDiff * position.lotSize;

      position.unrealizedPnlPercent =
        ((position.direction === 'long' ? priceDiff : -priceDiff) / position.entryPrice) * 100;
    } catch {
      // Keep position without market data if fetch fails
      logger.debug('[PaperTrading] Could not get price for position:', {
        positionId: position.id,
        symbol: position.symbol,
      });
    }
  }

  private async updateMaxDrawdown(client: { query: typeof db.query }, accountId: string): Promise<void> {
    // Calculate max drawdown from equity curve
    const result = await client.query<Record<string, string>>(
      `WITH equity_changes AS (
        SELECT
          current_balance as initial,
          current_balance + COALESCE(
            (SELECT SUM(realized_pnl) FROM trading.paper_trading_positions
             WHERE account_id = $1 AND status = 'closed'), 0
          ) as current
        FROM trading.paper_trading_accounts WHERE id = $1
      )
      SELECT
        CASE WHEN initial > 0
          THEN GREATEST(0, (initial - current) / initial * 100)
          ELSE 0
        END as drawdown
      FROM equity_changes`,
      [accountId]
    );

    if (result.rows.length > 0) {
      const currentDrawdown = parseFloat(result.rows[0].drawdown);
      await client.query(
        `UPDATE trading.paper_trading_accounts
         SET max_drawdown = GREATEST(max_drawdown, $1)
         WHERE id = $2`,
        [currentDrawdown, accountId]
      );
    }
  }
}

// Export singleton instance
export const paperTradingService = new PaperTradingService();