package spread

import "math"

func round(x float64, places int) float64 {
	p := math.Pow(10, float64(places))
	return math.Round(x*p) / p
}

// spreadPrice returns our unit price for a line and whether it was an exact
// catalog match. It never returns a price above the customer's current price.
func spreadPrice(li LineItem, cat Catalog) (price float64, matched bool) {
	if p, ok := cat.Lookup(li.PartNumber); ok {
		matched = true
		price = p
	} else {
		price = li.UnitPrice * (1 - modelDiscount(li))
	}
	price = round(price, 4)
	if price > li.UnitPrice || li.UnitPrice <= 0 {
		price = li.UnitPrice
	}
	return price, matched
}

// Analyze re-quotes every line against the built-in catalog (public demo).
func Analyze(ref string, items []LineItem) Report {
	return AnalyzeWith(ref, items, BuiltinCatalog{})
}

// AnalyzeWith re-quotes every line against the given catalog and rolls up the
// totals. Parts not found in the catalog are priced by the category model.
func AnalyzeWith(ref string, items []LineItem, cat Catalog) Report {
	rep := Report{BOMRef: ref}
	rep.Totals.CutRate = CutRate

	for _, li := range items {
		price, matched := spreadPrice(li, cat)
		unitSave := round(li.UnitPrice-price, 4)
		if unitSave < 0 {
			unitSave = 0
		}
		al := AnalyzedLine{
			LineItem:    li,
			SpreadPrice: price,
			UnitSaving:  unitSave,
			LineMarket:  round(li.UnitPrice*li.Quantity, 2),
			LineSpread:  round(price*li.Quantity, 2),
			Matched:     matched,
		}
		al.LineSaving = round(al.LineMarket-al.LineSpread, 2)
		if al.LineSaving < 0 {
			al.LineSaving = 0
		}

		rep.Lines = append(rep.Lines, al)
		rep.Totals.Market += al.LineMarket
		rep.Totals.Spread += al.LineSpread
		rep.Totals.Savings += al.LineSaving
	}

	rep.Totals.Lines = len(rep.Lines)
	rep.Totals.Market = round(rep.Totals.Market, 2)
	rep.Totals.Spread = round(rep.Totals.Spread, 2)
	rep.Totals.Savings = round(rep.Totals.Savings, 2)
	rep.Totals.OurCut = round(rep.Totals.Savings*CutRate, 2)
	rep.Totals.NetSavings = round(rep.Totals.Savings-rep.Totals.OurCut, 2)
	return rep
}