package financial

import (
	"testing"
)

func TestCO2Calculator_CalculateCO2Reduction(t *testing.T) {
	config := DefaultConfig()
	cc := NewCO2Calculator(config)

	tests := []struct {
		name         string
		resourceType string
		annualVolume float64
		expectedMin  float64
		expectedMax  float64
	}{
		{
			name:         "Heat energy",
			resourceType: "heat",
			annualVolume: 1000.0,
			expectedMin:  189.0, // 1000 MWh * 0.3 t/MWh * 0.9 efficiency * 0.7 utilization
			expectedMax:  191.0,
		},
		{
			name:         "Steam energy",
			resourceType: "steam",
			annualVolume: 1000.0,
			expectedMin:  189.0,
			expectedMax:  191.0,
		},
		{
			name:         "Water treatment",
			resourceType: "water",
			annualVolume: 1000000.0, // 1 million liters
			expectedMin:  300.0,     // 1M liters * 1 kWh/m³ * 0.3 t/MWh / 1000
			expectedMax:  310.0,
		},
		{
			name:         "Biowaste",
			resourceType: "biowaste",
			annualVolume: 1000.0, // 1000 tonnes
			expectedMin:  500.0,  // 1000 tonnes * 0.5 t CO2/tonne
			expectedMax:  510.0,
		},
		{
			name:         "Cooling",
			resourceType: "cooling",
			annualVolume: 1000.0,
			expectedMin:  189.0,
			expectedMax:  191.0,
		},
		{
			name:         "Unknown resource",
			resourceType: "unknown",
			annualVolume: 1000.0,
			expectedMin:  0.0,
			expectedMax:  0.1,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			result := cc.CalculateCO2Reduction(tt.resourceType, tt.annualVolume)

			if result < tt.expectedMin || result > tt.expectedMax {
				t.Errorf("CalculateCO2Reduction(%s, %v) = %v, expected between %v and %v",
					tt.resourceType, tt.annualVolume, result, tt.expectedMin, tt.expectedMax)
			}
		})
	}
}

func TestCO2Calculator_ZeroVolume(t *testing.T) {
	config := DefaultConfig()
	cc := NewCO2Calculator(config)

	result := cc.CalculateCO2Reduction("heat", 0.0)

	if result != 0.0 {
		t.Errorf("CalculateCO2Reduction with zero volume = %v, want 0.0", result)
	}
}

func TestCO2Calculator_NegativeVolume(t *testing.T) {
	config := DefaultConfig()
	cc := NewCO2Calculator(config)

	result := cc.CalculateCO2Reduction("heat", -1000.0)

	if result != 0.0 {
		t.Errorf("CalculateCO2Reduction with negative volume = %v, want 0.0", result)
	}
}