package financial

// CO2CalculatorImpl implements CO2Calculator interface
type CO2CalculatorImpl struct {
	config *Config
}

// NewCO2Calculator creates a new CO2 calculator
func NewCO2Calculator(config *Config) CO2Calculator {
	return &CO2CalculatorImpl{config: config}
}

// CalculateCO2Reduction calculates annual CO₂ emissions avoided
func (cc *CO2CalculatorImpl) CalculateCO2Reduction(resourceType string, annualVolume float64) float64 {
	// Handle negative volumes
	if annualVolume <= 0 {
		return 0.0
	}

	// Only calculate for energy-related resources
	switch resourceType {
	case "heat", "steam", "cooling":
		// Assume volume is in MWh/year
		return annualVolume * cc.config.GridEmissionFactor * cc.config.HeatEfficiency * cc.config.UtilizationRate
	case "water":
		// Water treatment energy: config.WaterTreatmentKwh kWh/m³
		return annualVolume * (cc.config.WaterTreatmentKwh / 1000) * cc.config.GridEmissionFactor // Convert kWh to MWh
	case "biowaste":
		// Waste diversion avoided emissions: config.WasteDiversionCo2 t CO₂/tonne waste
		return annualVolume * cc.config.WasteDiversionCo2
	default:
		return 0.0
	}
}