/**
 * Test suite for position sizing calculations
 */
import { describe, it, expect } from 'bun:test';
import {
  fixedRiskPositionSize,
  kellyPositionSize,
  fractionalKellyPositionSize,
  volatilityTargetPositionSize,
  equalWeightPositionSize,
  atrBasedPositionSize,
  expectancyPositionSize,
  monteCarloPositionSize,
  sharpeOptimizedPositionSize,
  fixedFractionalPositionSize,
  volatilityAdjustedPositionSize,
  correlationAdjustedPositionSize,
  calculatePortfolioHeat,
  dynamicPositionSize,
  liquidityConstrainedPositionSize,
  multiTimeframePositionSize,
  riskParityPositionSize,
  validatePositionSize,
  type PositionSizeParams,
  type KellyParams,
  type VolatilityParams
} from '../../src/calculations/position-sizing';

describe('Position Sizing Calculations', () => {
  describe('fixedRiskPositionSize', () => {
    it('should calculate correct position size for long position', () => {
      const params: PositionSizeParams = {
        accountSize: 100000,
        riskPercentage: 2,
        entryPrice: 100,
        stopLoss: 95,
        leverage: 1
      };
      
      const result = fixedRiskPositionSize(params);
      // Risk amount: 100000 * 0.02 = 2000
      // Risk per share: 100 - 95 = 5
      // Position size: 2000 / 5 = 400 shares
      expect(result).toBe(400);
    });

    it('should calculate correct position size for short position', () => {
      const params: PositionSizeParams = {
        accountSize: 100000,
        riskPercentage: 2,
        entryPrice: 100,
        stopLoss: 105,
        leverage: 1
      };
      
      const result = fixedRiskPositionSize(params);
      // Risk per share: |100 - 105| = 5
      // Position size: 2000 / 5 = 400 shares
      expect(result).toBe(400);
    });

    it('should return 0 for invalid inputs', () => {
      const params: PositionSizeParams = {
        accountSize: 0,
        riskPercentage: 2,
        entryPrice: 100,
        stopLoss: 95
      };
      
      expect(fixedRiskPositionSize(params)).toBe(0);
    });

    it('should return 0 when entry price equals stop loss', () => {
      const params: PositionSizeParams = {
        accountSize: 100000,
        riskPercentage: 2,
        entryPrice: 100,
        stopLoss: 100
      };
      
      expect(fixedRiskPositionSize(params)).toBe(0);
    });
  });

  describe('kellyPositionSize', () => {
    it('should calculate correct Kelly position size', () => {
      const params: KellyParams = {
        winRate: 0.6,
        averageWin: 150,
        averageLoss: -100
      };
      
      const result = kellyPositionSize(params, 100000);
      
      // Kelly formula: f = (bp - q) / b
      // b = 150/100 = 1.5, p = 0.6, q = 0.4
      // f = (1.5 * 0.6 - 0.4) / 1.5 = (0.9 - 0.4) / 1.5 = 0.5 / 1.5 = 0.333
      // With safety factor of 0.25: 0.333 * 0.25 = 0.083
      // Capped at 0.25, so result should be 0.083
      // Position: 100000 * 0.083 = 8300
      expect(result).toBeCloseTo(8333, 0);
    });

    it('should return 0 for negative expectancy', () => {
      const params: KellyParams = {
        winRate: 0.3,
        averageWin: 100,
        averageLoss: -200
      };
      
      const result = kellyPositionSize(params, 100000);
      expect(result).toBe(0);
    });

    it('should return 0 for invalid inputs', () => {
      const params: KellyParams = {
        winRate: 0,
        averageWin: 100,
        averageLoss: -100
      };
      
      expect(kellyPositionSize(params, 100000)).toBe(0);
    });
  });

  describe('volatilityTargetPositionSize', () => {
    it('should calculate correct volatility-targeted position size', () => {
      const params: VolatilityParams = {
        price: 100,
        volatility: 0.20,
        targetVolatility: 0.10,
        lookbackDays: 30
      };
      
      const result = volatilityTargetPositionSize(params, 100000);
      
      // Volatility ratio: 0.10 / 0.20 = 0.5
      // Position value: 100000 * 0.5 = 50000
      // Position size: 50000 / 100 = 500 shares
      expect(result).toBe(500);
    });

    it('should cap leverage at 2x', () => {
      const params: VolatilityParams = {
        price: 100,
        volatility: 0.05,
        targetVolatility: 0.20,
        lookbackDays: 30
      };
      
      const result = volatilityTargetPositionSize(params, 100000);
      
      // Volatility ratio would be 4, but capped at 2
      // Position value: 100000 * 2 = 200000
      // Position size: 200000 / 100 = 2000 shares
      expect(result).toBe(2000);
    });
  });

  describe('equalWeightPositionSize', () => {
    it('should calculate equal weight position size', () => {
      const result = equalWeightPositionSize(100000, 5, 100);
      
      // Position value per asset: 100000 / 5 = 20000
      // Position size: 20000 / 100 = 200 shares
      expect(result).toBe(200);
    });

    it('should return 0 for invalid inputs', () => {
      expect(equalWeightPositionSize(100000, 0, 100)).toBe(0);
      expect(equalWeightPositionSize(100000, 5, 0)).toBe(0);
    });
  });

  describe('atrBasedPositionSize', () => {
    it('should calculate ATR-based position size', () => {
      const result = atrBasedPositionSize(100000, 2, 5, 2, 100);
      
      // Risk amount: 100000 * 0.02 = 2000
      // Stop distance: 5 * 2 = 10
      // Position size: 2000 / 10 = 200 shares
      expect(result).toBe(200);
    });

    it('should return 0 for zero ATR', () => {
      const result = atrBasedPositionSize(100000, 2, 0, 2, 100);
      expect(result).toBe(0);
    });
  });

  describe('expectancyPositionSize', () => {
    it('should calculate expectancy-based position size', () => {
      const result = expectancyPositionSize(100000, 0.6, 150, -100, 5);
      
      // Expectancy: 0.6 * 150 - 0.4 * 100 = 90 - 40 = 50
      // Expectancy ratio: 50 / 100 = 0.5
      // Risk percentage: min(0.5 * 0.5, 5) = min(0.25, 5) = 0.25
      // Position: 100000 * 0.0025 = 250
      expect(result).toBe(250);
    });

    it('should return 0 for negative expectancy', () => {
      const result = expectancyPositionSize(100000, 0.3, 100, -200);
      expect(result).toBe(0);
    });
  });

  describe('correlationAdjustedPositionSize', () => {
    it('should adjust position size based on correlation', () => {
      const existingPositions = [
        { size: 1000, correlation: 0.5 },
        { size: 500, correlation: 0.3 }
      ];
      
      const result = correlationAdjustedPositionSize(1000, existingPositions, 0.5);
      
      // Should reduce position size based on correlation risk
      expect(result).toBeLessThan(1000);
      expect(result).toBeGreaterThan(0);
    });

    it('should return original size when no existing positions', () => {
      const result = correlationAdjustedPositionSize(1000, [], 0.5);
      expect(result).toBe(1000);
    });
  });

  describe('calculatePortfolioHeat', () => {
    it('should calculate portfolio heat correctly', () => {
      const positions = [
        { value: 10000, risk: 500 },
        { value: 15000, risk: 750 },
        { value: 20000, risk: 1000 }
      ];
      
      const result = calculatePortfolioHeat(positions, 100000);
      
      // Total risk: 500 + 750 + 1000 = 2250
      // Heat: (2250 / 100000) * 100 = 2.25%
      expect(result).toBe(2.25);
    });

    it('should handle empty positions array', () => {
      const result = calculatePortfolioHeat([], 100000);
      expect(result).toBe(0);
    });

    it('should cap heat at 100%', () => {
      const positions = [
        { value: 50000, risk: 150000 }
      ];
      
      const result = calculatePortfolioHeat(positions, 100000);
      expect(result).toBe(100);
    });
  });

  describe('dynamicPositionSize', () => {
    it('should adjust position size based on market conditions', () => {
      const result = dynamicPositionSize(1000, 0.25, 0.15, 0.05, 0.10);
      
      // Volatility adjustment: 0.15 / 0.25 = 0.6
      // Drawdown adjustment: 1 - (0.05 / 0.10) = 0.5
      // Adjusted size: 1000 * 0.6 * 0.5 = 300
      expect(result).toBe(300);
    });

    it('should handle high drawdown', () => {
      const result = dynamicPositionSize(1000, 0.20, 0.15, 0.15, 0.10);
      
      // Should significantly reduce position size due to high drawdown
      expect(result).toBeLessThan(500);
    });
  });

  describe('liquidityConstrainedPositionSize', () => {
    it('should constrain position size based on liquidity', () => {
      const result = liquidityConstrainedPositionSize(1000, 10000, 0.05, 100);
      
      // Max shares: 10000 * 0.05 = 500
      // Should return min(1000, 500) = 500
      expect(result).toBe(500);
    });

    it('should return desired size when liquidity allows', () => {
      const result = liquidityConstrainedPositionSize(500, 20000, 0.05, 100);
      
      // Max shares: 20000 * 0.05 = 1000
      // Should return min(500, 1000) = 500
      expect(result).toBe(500);
    });
  });

  describe('multiTimeframePositionSize', () => {
    it('should weight signals correctly', () => {
      const result = multiTimeframePositionSize(100000, 0.8, 0.6, 0.4, 2);
      
      // Weighted signal: 0.8 * 0.2 + 0.6 * 0.3 + 0.4 * 0.5 = 0.16 + 0.18 + 0.2 = 0.54
      // Adjusted risk: 2 * 0.54 = 1.08%
      // Position: 100000 * 0.0108 = 1080
      expect(result).toBe(1080);
    });

    it('should clamp signals to valid range', () => {
      const result = multiTimeframePositionSize(100000, 2, -2, 1.5, 2);
      
      // Signals should be clamped to [-1, 1]
      // Weighted: 1 * 0.2 + (-1) * 0.3 + 1 * 0.5 = 0.2 - 0.3 + 0.5 = 0.4
      // Adjusted risk: 2 * 0.4 = 0.8%
      expect(result).toBe(800);
    });
  });

  describe('riskParityPositionSize', () => {
    it('should allocate based on inverse volatility', () => {
      const assets = [
        { volatility: 0.10, price: 100 },
        { volatility: 0.20, price: 200 }
      ];
      
      const result = riskParityPositionSize(assets, 0.15, 100000);
      
      // Asset 1: 1/0.10 = 10, Asset 2: 1/0.20 = 5
      // Total inverse vol: 15
      // Weights: Asset 1: 10/15 = 0.667, Asset 2: 5/15 = 0.333
      expect(result).toHaveLength(2);
      expect(result[0]).toBeGreaterThan(result[1]);
    });

    it('should handle zero volatility assets', () => {
      const assets = [
        { volatility: 0, price: 100 },
        { volatility: 0.20, price: 200 }
      ];
      
      const result = riskParityPositionSize(assets, 0.15, 100000);
      
      expect(result[0]).toBe(0);
      expect(result[1]).toBeGreaterThan(0);
    });
  });

  describe('sharpeOptimizedPositionSize', () => {
    it('should calculate position size based on Sharpe optimization', () => {
      const result = sharpeOptimizedPositionSize(100000, 0.15, 0.20, 0.02, 3);
      
      // Kelly formula for continuous returns: f = (μ - r) / σ²
      // Expected return: 0.15, Risk-free: 0.02, Volatility: 0.20
      // f = (0.15 - 0.02) / (0.20)² = 0.13 / 0.04 = 3.25
      // But capped at maxLeverage=3, so should be 3.0
      // Final position: 100000 * 3 = 300000
      expect(result).toBe(300000);
    });
    
    it('should return 0 for invalid inputs', () => {
      // Invalid volatility
      expect(sharpeOptimizedPositionSize(100000, 0.15, 0, 0.02)).toBe(0);
      
      // Invalid account size
      expect(sharpeOptimizedPositionSize(0, 0.15, 0.20, 0.02)).toBe(0);
      
      // Expected return less than risk-free rate
      expect(sharpeOptimizedPositionSize(100000, 0.01, 0.20, 0.02)).toBe(0);
    });
    
    it('should respect maximum leverage', () => {
      const result = sharpeOptimizedPositionSize(100000, 0.30, 0.20, 0.02, 2);
      
      // Kelly fraction would be (0.30 - 0.02) / (0.20)² = 7, but capped at 2
      // Position: 100000 * 2 = 200000
      expect(result).toBe(200000);
    });
  });

  describe('validatePositionSize', () => {
    it('should validate position size against limits', () => {
      const result = validatePositionSize(500, 100, 100000, 10, 2);
      
      // Position value: 500 * 100 = 50000 (50% of account)
      // This exceeds 10% limit
      expect(result.isValid).toBe(false);
      expect(result.violations).toContain('Position exceeds maximum 10% of account');
      expect(result.adjustedSize).toBe(100); // 10000 / 100
    });

    it('should pass validation for reasonable position', () => {
      const result = validatePositionSize(50, 100, 100000, 10, 2);
      
      // Position value: 50 * 100 = 5000 (5% of account)
      expect(result.isValid).toBe(true);
      expect(result.violations).toHaveLength(0);
      expect(result.adjustedSize).toBe(50);
    });

    it('should handle fractional shares', () => {
      const result = validatePositionSize(0.5, 100, 100000, 10, 2);
      
      expect(result.isValid).toBe(false);
      expect(result.violations).toContain('Position size too small (less than 1 share)');
      expect(result.adjustedSize).toBe(0);
    });
  });
});