moving ledger predictions to /ana

ana/bpi.go

@@ -0,0 +1,42 @@
+package ana
+
+import (
+	"maps"
+	"regexp"
+	"time"
+
+	"gogs.inhome.blapointe.com/ana-ledger/ledger"
+)
+
+func BPIsWithFixedGrowthPrediction(bpis ledger.BPIs, window time.Duration, pattern string, apy float64) (ledger.BPIs, error) {
+	last := map[ledger.Currency]struct {
+		t string
+		v float64
+	}{}
+	for currency, bpi := range bpis {
+		for date, value := range bpi {
+			if date > last[currency].t {
+				was := last[currency]
+				was.t = date
+				was.v = value
+				last[currency] = was
+			}
+		}
+	}
+
+	result := make(ledger.BPIs)
+	p := regexp.MustCompile(pattern)
+	for currency, v := range bpis {
+		result[currency] = maps.Clone(v)
+		if p.MatchString(string(currency)) {
+			for _, predictionTime := range predictionTimes(window) {
+				k2 := predictionTime.Format("2006-01")
+				was := last[currency]
+				was.v *= 1.0 + (apy / 12.0)
+				result[currency][k2] = was.v
+				last[currency] = was
+			}
+		}
+	}
+	return result, nil
+}