package unit

import (
	"github.com/damirmukimov/city_resource_graph/models/customer"
	"github.com/damirmukimov/city_resource_graph/models/params"
	"github.com/damirmukimov/city_resource_graph/models/revenue"
)

// UnitEconomics contains all unit economics metrics for a year.
type UnitEconomics struct {
	LTV           TierMetrics `json:"ltv"`            // Lifetime Value by tier
	CAC           float64     `json:"cac"`            // Customer Acquisition Cost
	LTVToCACRatio float64     `json:"ltv_cac_ratio"`  // LTV/CAC ratio
	ChurnRate     float64     `json:"churn_rate"`     // Blended annual churn rate
	PaybackPeriod float64     `json:"payback_period"` // Months to recover CAC
}

// TierMetrics contains metrics for each tier.
type TierMetrics struct {
	Basic      float64 `json:"basic"`
	Business   float64 `json:"business"`
	Enterprise float64 `json:"enterprise"`
	Blended    float64 `json:"blended"`
}

// CalculateUnitEconomics computes unit economics for a given year.
func CalculateUnitEconomics(year int, custMetrics customer.CustomerMetrics, tierDist customer.TierDistribution, revBreakdown revenue.RevenueBreakdown, p *params.Params) UnitEconomics {
	uep := p.UnitEconomics

	// Calculate LTV for each tier
	ltv := calculateLTVByTier(p)

	// Calculate blended LTV based on tier distribution
	totalCustomers := float64(custMetrics.PayingOrgs)
	if totalCustomers == 0 {
		totalCustomers = 1 // Avoid division by zero
	}

	blendedLTV := (ltv.Basic*float64(tierDist.Basic) +
		ltv.Business*float64(tierDist.Business) +
		ltv.Enterprise*float64(tierDist.Enterprise)) / totalCustomers

	// Calculate CAC (marketing & sales costs / new customers)
	marketingSalesCosts := p.Costs.MarketingSales.GetYear(year)
	cac := marketingSalesCosts / float64(custMetrics.PayingOrgs)
	if custMetrics.PayingOrgs == 0 {
		cac = 0
	}

	// Calculate LTV/CAC ratio
	ltvToCACRatio := 0.0
	if cac > 0 {
		ltvToCACRatio = blendedLTV / cac
	}

	// Calculate blended churn rate (weighted by tier distribution)
	blendedChurn := (uep.ChurnRates.Basic*float64(tierDist.Basic) +
		uep.ChurnRates.Business*float64(tierDist.Business) +
		uep.ChurnRates.Enterprise*float64(tierDist.Enterprise)) / totalCustomers

	// Calculate payback period (months to recover CAC)
	avgMonthlyRevenue := revBreakdown.Total / float64(custMetrics.PayingOrgs) / 12
	paybackPeriod := 0.0
	if avgMonthlyRevenue > 0 {
		paybackPeriod = cac / avgMonthlyRevenue
	}

	return UnitEconomics{
		LTV: TierMetrics{
			Basic:      ltv.Basic,
			Business:   ltv.Business,
			Enterprise: ltv.Enterprise,
			Blended:    blendedLTV,
		},
		CAC:           cac,
		LTVToCACRatio: ltvToCACRatio,
		ChurnRate:     blendedChurn,
		PaybackPeriod: paybackPeriod,
	}
}

// calculateLTVByTier calculates Lifetime Value for each tier.
func calculateLTVByTier(p *params.Params) TierMetrics {
	uep := p.UnitEconomics

	// Get blended monthly subscription prices (including transaction uplifts)
	basicMonthly := p.Pricing.Basic * (1.0 + p.Pricing.BlendedUplift.Basic)
	businessMonthly := p.Pricing.Business * (1.0 + p.Pricing.BlendedUplift.Business)
	enterpriseMonthly := p.Pricing.Enterprise * (1.0 + p.Pricing.BlendedUplift.Enterprise)

	// Calculate LTV for Basic tier
	basicLTV := calculateTierLTV(
		basicMonthly,
		uep.RetentionMonths.Basic,
		uep.TransactionFees.Basic,
		0, // No upsell revenue for basic (it's the entry tier)
		uep.PlatformCosts,
	)

	// Calculate LTV for Business tier
	businessUpsellRevenue := uep.UpsellRates.BusinessToEnterprise * calculateTierLTV(
		enterpriseMonthly,
		uep.RetentionMonths.Enterprise,
		uep.TransactionFees.Enterprise,
		0, // No further upsell
		uep.PlatformCosts,
	)
	businessLTV := calculateTierLTV(
		businessMonthly,
		uep.RetentionMonths.Business,
		uep.TransactionFees.Business,
		businessUpsellRevenue,
		uep.PlatformCosts,
	)

	// Calculate LTV for Enterprise tier
	enterpriseExpansionRevenue := uep.EnterpriseExpansion.MultiSiteRate *
		uep.EnterpriseExpansion.AdditionalSites *
		uep.EnterpriseExpansion.SiteRevenue * 12 * uep.RetentionMonths.Enterprise // Annual expansion revenue

	enterpriseLTV := calculateTierLTV(
		enterpriseMonthly,
		uep.RetentionMonths.Enterprise,
		uep.TransactionFees.Enterprise,
		enterpriseExpansionRevenue,
		uep.PlatformCosts,
	)

	return TierMetrics{
		Basic:      basicLTV,
		Business:   businessLTV,
		Enterprise: enterpriseLTV,
	}
}

// calculateTierLTV calculates LTV for a specific tier.
func calculateTierLTV(monthlyRevenue, retentionMonths, transactionFees, upsellRevenue, platformCosts float64) float64 {
	// Gross subscription revenue over lifetime
	grossSubscriptionRevenue := monthlyRevenue * retentionMonths

	// Transaction revenue over lifetime (annual fees × years)
	years := retentionMonths / 12
	grossTransactionRevenue := transactionFees * years

	// Total gross revenue
	totalGrossRevenue := grossSubscriptionRevenue + grossTransactionRevenue + upsellRevenue

	// Net of platform costs
	totalNetRevenue := totalGrossRevenue * (1.0 - platformCosts)

	return totalNetRevenue
}