package internal

import (
	"context"
	"fmt"
	stdmath "math"
	"math/big"
	"math/rand"
	"time"

	pkgmath "github.com/fraktal/mev-beta/pkg/math"
)

// PropertyTestSuite implements mathematical property testing
type PropertyTestSuite struct {
	auditor   *MathAuditor
	converter *pkgmath.DecimalConverter
	rand      *rand.Rand
}

// NewPropertyTestSuite creates a new property test suite
func NewPropertyTestSuite(auditor *MathAuditor) *PropertyTestSuite {
	return &PropertyTestSuite{
		auditor:   auditor,
		converter: pkgmath.NewDecimalConverter(),
		rand:      rand.New(rand.NewSource(42)), // Deterministic seed
	}
}

// PropertyTestResult represents the result of a property test
type PropertyTestResult struct {
	PropertyName string             `json:"property_name"`
	TestCount    int                `json:"test_count"`
	PassCount    int                `json:"pass_count"`
	FailCount    int                `json:"fail_count"`
	MaxError     float64            `json:"max_error_bp"`
	AvgError     float64            `json:"avg_error_bp"`
	Duration     time.Duration      `json:"duration"`
	Failures     []*PropertyFailure `json:"failures,omitempty"`
}

// PropertyFailure represents a property test failure
type PropertyFailure struct {
	Input       string  `json:"input"`
	Expected    string  `json:"expected"`
	Actual      string  `json:"actual"`
	ErrorBP     float64 `json:"error_bp"`
	Description string  `json:"description"`
}

// RunAllPropertyTests runs all mathematical property tests
func (pts *PropertyTestSuite) RunAllPropertyTests(ctx context.Context) ([]*PropertyTestResult, error) {
	var results []*PropertyTestResult

	// Test monotonicity properties
	if result, err := pts.TestPriceMonotonicity(ctx, 1000); err == nil {
		results = append(results, result)
	}

	// Test round-trip properties
	if result, err := pts.TestRoundTripProperties(ctx, 1000); err == nil {
		results = append(results, result)
	}

	// Test symmetry properties
	if result, err := pts.TestSymmetryProperties(ctx, 1000); err == nil {
		results = append(results, result)
	}

	// Test boundary properties
	if result, err := pts.TestBoundaryProperties(ctx, 500); err == nil {
		results = append(results, result)
	}

	// Test arithmetic properties
	if result, err := pts.TestArithmeticProperties(ctx, 1000); err == nil {
		results = append(results, result)
	}

	return results, nil
}

// TestPriceMonotonicity tests that price functions are monotonic
func (pts *PropertyTestSuite) TestPriceMonotonicity(ctx context.Context, testCount int) (*PropertyTestResult, error) {
	startTime := time.Now()
	result := &PropertyTestResult{
		PropertyName: "Price Monotonicity",
		TestCount:    testCount,
	}

	var totalError float64

	for i := 0; i < testCount; i++ {
		// Generate two reserve ratios where ratio1 > ratio2
		reserve0_1 := pts.generateRandomReserve()
		reserve1_1 := pts.generateRandomReserve()

		reserve0_2 := reserve0_1
		reserve1_2 := new(big.Int).Mul(reserve1_1, big.NewInt(2)) // Double reserve1 to decrease price

		// Calculate prices
		price1, _ := pts.auditor.calculateUniswapV2Price(
			&pkgmath.UniversalDecimal{Value: reserve0_1, Decimals: 18, Symbol: "TOKEN0"},
			&pkgmath.UniversalDecimal{Value: reserve1_1, Decimals: 18, Symbol: "TOKEN1"},
		)

		price2, _ := pts.auditor.calculateUniswapV2Price(
			&pkgmath.UniversalDecimal{Value: reserve0_2, Decimals: 18, Symbol: "TOKEN0"},
			&pkgmath.UniversalDecimal{Value: reserve1_2, Decimals: 18, Symbol: "TOKEN1"},
		)

		if price1 == nil || price2 == nil {
			continue
		}

		// Price2 should be greater than Price1 (more reserve1 means higher price per token0)
		if price2.Value.Cmp(price1.Value) <= 0 {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("Reserve0: %s, Reserve1_1: %s, Reserve1_2: %s", reserve0_1.String(), reserve1_1.String(), reserve1_2.String()),
				Expected:    fmt.Sprintf("Price2 > Price1 (%s)", price1.Value.String()),
				Actual:      fmt.Sprintf("Price2 = %s", price2.Value.String()),
				ErrorBP:     100.0, // Categorical error
				Description: "Monotonicity violation: increasing reserve should increase price",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
			totalError += 100.0
		} else {
			result.PassCount++
		}
	}

	if result.TestCount > 0 {
		result.AvgError = totalError / float64(result.TestCount)
	}
	result.Duration = time.Since(startTime)

	return result, nil
}

// TestRoundTripProperties tests that conversions are reversible
func (pts *PropertyTestSuite) TestRoundTripProperties(ctx context.Context, testCount int) (*PropertyTestResult, error) {
	startTime := time.Now()
	result := &PropertyTestResult{
		PropertyName: "Round Trip Properties",
		TestCount:    testCount,
	}

	var totalError float64

	for i := 0; i < testCount; i++ {
		// Generate random price
		originalPrice := pts.generateRandomPrice()

		// Convert to UniversalDecimal and back
		priceDecimal, err := pts.converter.FromString(fmt.Sprintf("%.18f", originalPrice), 18, "PRICE")
		if err != nil {
			continue
		}

		// Convert back to float - use a simple division approach
		recoveredPrice := 0.0
		if priceDecimal.Value.Cmp(big.NewInt(0)) > 0 {
			priceFloat := new(big.Float).SetInt(priceDecimal.Value)
			scaleFactor := new(big.Float).SetInt(new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(priceDecimal.Decimals)), nil))
			priceFloat.Quo(priceFloat, scaleFactor)
			recoveredPrice, _ = priceFloat.Float64()
		}

		// Calculate error
		errorBP := stdmath.Abs(recoveredPrice-originalPrice) / originalPrice * 10000
		totalError += errorBP

		if errorBP > pts.auditor.tolerance*10000 {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("%.18f", originalPrice),
				Expected:    fmt.Sprintf("%.18f", originalPrice),
				Actual:      fmt.Sprintf("%.18f", recoveredPrice),
				ErrorBP:     errorBP,
				Description: "Round-trip conversion error exceeds tolerance",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
		} else {
			result.PassCount++
		}

		if errorBP > result.MaxError {
			result.MaxError = errorBP
		}
	}

	if result.TestCount > 0 {
		result.AvgError = totalError / float64(result.TestCount)
	}
	result.Duration = time.Since(startTime)

	return result, nil
}

// TestSymmetryProperties tests mathematical symmetries
func (pts *PropertyTestSuite) TestSymmetryProperties(ctx context.Context, testCount int) (*PropertyTestResult, error) {
	startTime := time.Now()
	result := &PropertyTestResult{
		PropertyName: "Symmetry Properties",
		TestCount:    testCount,
	}

	var totalError float64

	for i := 0; i < testCount; i++ {
		// Test that swapping tokens gives reciprocal price
		reserve0 := pts.generateRandomReserve()
		reserve1 := pts.generateRandomReserve()

		// Calculate price TOKEN1/TOKEN0
		price1, _ := pts.auditor.calculateUniswapV2Price(
			&pkgmath.UniversalDecimal{Value: reserve0, Decimals: 18, Symbol: "TOKEN0"},
			&pkgmath.UniversalDecimal{Value: reserve1, Decimals: 18, Symbol: "TOKEN1"},
		)

		// Calculate price TOKEN0/TOKEN1 (swapped)
		price2, _ := pts.auditor.calculateUniswapV2Price(
			&pkgmath.UniversalDecimal{Value: reserve1, Decimals: 18, Symbol: "TOKEN1"},
			&pkgmath.UniversalDecimal{Value: reserve0, Decimals: 18, Symbol: "TOKEN0"},
		)

		if price1 == nil || price2 == nil {
			continue
		}

		// price1 * price2 should equal 1 (within tolerance)
		product := new(big.Int).Mul(price1.Value, price2.Value)
		// Scale product to compare with 10^36 (18 + 18 decimals)
		expected := new(big.Int).Exp(big.NewInt(10), big.NewInt(36), nil)

		// Calculate relative error
		diff := new(big.Int).Sub(product, expected)
		if diff.Sign() < 0 {
			diff.Neg(diff)
		}

		expectedFloat, _ := new(big.Float).SetInt(expected).Float64()
		diffFloat, _ := new(big.Float).SetInt(diff).Float64()

		errorBP := 0.0
		if expectedFloat > 0 {
			errorBP = (diffFloat / expectedFloat) * 10000
		}

		totalError += errorBP

		if errorBP > pts.auditor.tolerance*10000 {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("Reserve0: %s, Reserve1: %s", reserve0.String(), reserve1.String()),
				Expected:    "price1 * price2 = 1",
				Actual:      fmt.Sprintf("price1 * price2 = %s", product.String()),
				ErrorBP:     errorBP,
				Description: "Symmetry violation: reciprocal prices don't multiply to 1",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
		} else {
			result.PassCount++
		}

		if errorBP > result.MaxError {
			result.MaxError = errorBP
		}
	}

	if result.TestCount > 0 {
		result.AvgError = totalError / float64(result.TestCount)
	}
	result.Duration = time.Since(startTime)

	return result, nil
}

// TestBoundaryProperties tests behavior at boundaries
func (pts *PropertyTestSuite) TestBoundaryProperties(ctx context.Context, testCount int) (*PropertyTestResult, error) {
	startTime := time.Now()
	result := &PropertyTestResult{
		PropertyName: "Boundary Properties",
		TestCount:    testCount,
	}

	boundaryValues := []*big.Int{
		big.NewInt(1),    // Minimum
		big.NewInt(1000), // Small
		new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil), // 1 token
		new(big.Int).Exp(big.NewInt(10), big.NewInt(21), nil), // 1000 tokens
		new(big.Int).Exp(big.NewInt(10), big.NewInt(25), nil), // Large value
	}

	for i := 0; i < testCount; i++ {
		// Test combinations of boundary values
		reserve0 := boundaryValues[pts.rand.Intn(len(boundaryValues))]
		reserve1 := boundaryValues[pts.rand.Intn(len(boundaryValues))]

		// Skip if reserves are equal to zero
		if reserve0.Cmp(big.NewInt(0)) == 0 || reserve1.Cmp(big.NewInt(0)) == 0 {
			continue
		}

		price, err := pts.auditor.calculateUniswapV2Price(
			&pkgmath.UniversalDecimal{Value: reserve0, Decimals: 18, Symbol: "TOKEN0"},
			&pkgmath.UniversalDecimal{Value: reserve1, Decimals: 18, Symbol: "TOKEN1"},
		)

		if err != nil {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("Reserve0: %s, Reserve1: %s", reserve0.String(), reserve1.String()),
				Expected:    "Valid price calculation",
				Actual:      fmt.Sprintf("Error: %v", err),
				ErrorBP:     10000.0,
				Description: "Boundary value calculation failed",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
		} else if price == nil || price.Value.Cmp(big.NewInt(0)) <= 0 {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("Reserve0: %s, Reserve1: %s", reserve0.String(), reserve1.String()),
				Expected:    "Positive price",
				Actual:      "Zero or negative price",
				ErrorBP:     10000.0,
				Description: "Boundary value produced invalid price",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
		} else {
			result.PassCount++
		}
	}

	result.Duration = time.Since(startTime)
	return result, nil
}

// TestArithmeticProperties tests arithmetic operation properties
func (pts *PropertyTestSuite) TestArithmeticProperties(ctx context.Context, testCount int) (*PropertyTestResult, error) {
	startTime := time.Now()
	result := &PropertyTestResult{
		PropertyName: "Arithmetic Properties",
		TestCount:    testCount,
	}

	var totalError float64

	for i := 0; i < testCount; i++ {
		// Test that addition is commutative: a + b = b + a
		a := pts.generateRandomAmount()
		b := pts.generateRandomAmount()

		decimalA, _ := pkgmath.NewUniversalDecimal(a, 18, "TOKENA")
		decimalB, _ := pkgmath.NewUniversalDecimal(b, 18, "TOKENB")

		// Calculate a + b
		sum1 := new(big.Int).Add(decimalA.Value, decimalB.Value)

		// Calculate b + a
		sum2 := new(big.Int).Add(decimalB.Value, decimalA.Value)

		if sum1.Cmp(sum2) != 0 {
			failure := &PropertyFailure{
				Input:       fmt.Sprintf("A: %s, B: %s", a.String(), b.String()),
				Expected:    sum1.String(),
				Actual:      sum2.String(),
				ErrorBP:     10000.0,
				Description: "Addition is not commutative",
			}
			result.Failures = append(result.Failures, failure)
			result.FailCount++
			totalError += 10000.0
		} else {
			result.PassCount++
		}
	}

	if result.TestCount > 0 {
		result.AvgError = totalError / float64(result.TestCount)
	}
	result.Duration = time.Since(startTime)

	return result, nil
}

// Helper functions for generating test data

func (pts *PropertyTestSuite) generateRandomPrice() float64 {
	// Generate prices between 0.000001 and 1000000
	exponent := pts.rand.Float64()*12 - 6 // -6 to 6
	return stdmath.Pow(10, exponent)
}

func (pts *PropertyTestSuite) generateRandomReserve() *big.Int {
	// Generate reserves between 1 and 10^25
	exp := pts.rand.Intn(25) + 1
	base := big.NewInt(int64(pts.rand.Intn(9) + 1))
	return new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(exp)), nil).Mul(base, new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(exp)), nil))
}

func (pts *PropertyTestSuite) generateRandomAmount() *big.Int {
	// Generate amounts between 1 and 10^24
	exp := pts.rand.Intn(24) + 1
	base := big.NewInt(int64(pts.rand.Intn(9) + 1))
	return new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(exp)), nil).Mul(base, new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(exp)), nil))
}