package financial

import (
	"math"
	"testing"
)

func TestNPVCalculator_CalculateNPV(t *testing.T) {
	calc := NewNPVCalculator()

	tests := []struct {
		name         string
		capex        float64
		cashFlow     float64
		discountRate float64
		years        int
		wantPositive bool
	}{
		{
			name:         "Positive NPV",
			capex:        50000.0,
			cashFlow:     8000.0,
			discountRate: 0.08,
			years:        10,
			wantPositive: true,
		},
		{
			name:         "Negative NPV",
			capex:        100000.0,
			cashFlow:     5000.0,
			discountRate: 0.08,
			years:        10,
			wantPositive: false,
		},
		{
			name:         "Zero NPV",
			capex:        50000.0,
			cashFlow:     5525.0, // Approximately breakeven at 8%
			discountRate: 0.08,
			years:        10,
			wantPositive: false, // Will be very close to zero
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			npv := calc.CalculateNPV(tt.capex, tt.cashFlow, tt.discountRate, tt.years)

			if tt.wantPositive && npv <= 0 {
				t.Errorf("CalculateNPV() = %v, expected positive", npv)
			}
			if !tt.wantPositive && npv > 100 { // Allow small positive due to rounding
				t.Errorf("CalculateNPV() = %v, expected negative or near zero", npv)
			}
		})
	}
}

func TestIRRCalculator_CalculateIRR(t *testing.T) {
	calc := NewIRRCalculator()

	tests := []struct {
		name      string
		capex     float64
		cashFlow  float64
		years     int
		expected  float64
		tolerance float64
	}{
		{
			name:      "Reasonable IRR",
			capex:     50000.0,
			cashFlow:  8000.0,
			years:     10,
			expected:  9.6, // Approximately 9.6%
			tolerance: 1.0,
		},
		{
			name:      "High IRR",
			capex:     50000.0,
			cashFlow:  15000.0,
			years:     10,
			expected:  27.0, // Approximately 27%
			tolerance: 3.0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			irr := calc.CalculateIRR(tt.capex, tt.cashFlow, tt.years)

			if math.Abs(irr-tt.expected) > tt.tolerance {
				t.Errorf("CalculateIRR() = %v, expected ~%v (tolerance: %v)",
					irr, tt.expected, tt.tolerance)
			}
		})
	}
}

func TestPaybackCalculator_CalculatePaybackPeriod(t *testing.T) {
	calc := NewPaybackCalculator()

	tests := []struct {
		name     string
		capex    float64
		cashFlow float64
		expected float64
	}{
		{
			name:     "Quick payback",
			capex:    50000.0,
			cashFlow: 25000.0,
			expected: 2.0, // 2 years
		},
		{
			name:     "Long payback",
			capex:    100000.0,
			cashFlow: 20000.0,
			expected: 5.0, // 5 years
		},
		{
			name:     "Fractional payback",
			capex:    30000.0,
			cashFlow: 15000.0,
			expected: 2.0, // 2 years
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			payback := calc.CalculatePaybackPeriod(tt.capex, tt.cashFlow)

			if math.Abs(payback-tt.expected) > 0.01 {
				t.Errorf("CalculatePaybackPeriod() = %v, expected %v", payback, tt.expected)
			}
		})
	}
}

func TestCapexEstimator_EstimateCapex(t *testing.T) {
	config := DefaultConfig()
	calc := NewCapexEstimator(config)

	tests := []struct {
		name         string
		resourceType string
		distanceKm   float64
		annualVolume float64
		expectedMin  float64
		expectedMax  float64
	}{
		{
			name:         "Heat short distance",
			resourceType: "heat",
			distanceKm:   5.0,
			annualVolume: 1000.0,
			expectedMin:  270000.0, // (5km * 50000 + 20000) * scaleFactor
			expectedMax:  280000.0,
		},
		{
			name:         "Heat long distance",
			resourceType: "heat",
			distanceKm:   50.0,
			annualVolume: 1000.0,
			expectedMin:  2520000.0, // (50km * 50000 + 20000) * scaleFactor
			expectedMax:  2530000.0,
		},
		{
			name:         "Biowaste",
			resourceType: "biowaste",
			distanceKm:   10.0,
			annualVolume: 1000.0,
			expectedMin:  70000.0, // (10km * 5000 + 20000) * scaleFactor
			expectedMax:  80000.0,
		},
		{
			name:         "Service",
			resourceType: "service",
			distanceKm:   10.0,
			annualVolume: 1000.0,
			expectedMin:  20000.0, // (10km * 0 + 20000) * scaleFactor
			expectedMax:  25000.0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			capex := calc.EstimateCapex(tt.resourceType, tt.distanceKm, tt.annualVolume)

			if capex < tt.expectedMin || capex > tt.expectedMax {
				t.Errorf("EstimateCapex() = %v, expected between %v and %v",
					capex, tt.expectedMin, tt.expectedMax)
			}
		})
	}
}

func TestTransportCostCalculator_CalculateTransportCost(t *testing.T) {
	config := DefaultConfig()
	calc := NewTransportCostCalculator(config)

	tests := []struct {
		name         string
		resourceType string
		distanceKm   float64
		expectedMin  float64
		expectedMax  float64
	}{
		{
			name:         "Heat transport",
			resourceType: "heat",
			distanceKm:   10.0,
			expectedMin:  0.005, // 10km * 0.0005/€km
			expectedMax:  0.006,
		},
		{
			name:         "Water transport",
			resourceType: "water",
			distanceKm:   10.0,
			expectedMin:  0.01, // 10km * 0.001/€km
			expectedMax:  0.011,
		},
		{
			name:         "Service transport",
			resourceType: "service",
			distanceKm:   10.0,
			expectedMin:  0.0,
			expectedMax:  0.1,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			cost := calc.CalculateTransportCost(tt.resourceType, tt.distanceKm)

			if cost < tt.expectedMin || cost > tt.expectedMax {
				t.Errorf("CalculateTransportCost() = %v, expected between %v and %v",
					cost, tt.expectedMin, tt.expectedMax)
			}
		})
	}
}