package ana

import (
	"maps"
	"math"
	"regexp"
	"time"

	"gogs.inhome.blapointe.com/ana-ledger/ledger"
)

func RegisterWithCompoundingInterestPrediction(reg ledger.Register, window time.Duration, pattern string, apy float64) (ledger.Register, error) {
	lastBalances := make(ledger.Balances)
	p := regexp.MustCompile(pattern)
	for _, d := range reg.Dates() {
		if t, _ := dateToTime(d); time.Now().Before(t) {
			continue
		}
		for name := range reg[d] {
			if p.MatchString(name) {
				lastBalances[name] = reg[d][name]
			}
		}
	}

	predictedTimes := predictionTimes(window)
	result := maps.Clone(reg)
	for _, predictionTime := range predictedTimes {
		k := predictionTime.Format("2006-01")
		if _, ok := result[k]; !ok {
			result[k] = make(ledger.Balances)
		}
		for k2, v2 := range lastBalances {
			if _, ok := result[k][k2]; !ok {
				result[k][k2] = maps.Clone(v2)
			}
		}
	}

	addedSoFar := make(ledger.Balances)
	for _, predictionTime := range predictedTimes {
		k := predictionTime.Format("2006-01")
		for name := range lastBalances {
			if _, ok := addedSoFar[name]; !ok {
				addedSoFar[name] = make(ledger.Balance)
			}
			for currency := range result[k][name] {
				// A = P(1 + r/n)**nt
				p := result[k][name][currency] + addedSoFar[name][currency]
				r := apy
				n := 12.0
				t := 1.0 / 12.0
				result[k][name][currency] = p * math.Pow(1.0+(r/n), n*t)
				addedSoFar[name][currency] += (result[k][name][currency] - p)
			}
		}
	}

	return result, nil
}