From 31e1a86795a376ee55109f7d2c4e30457a4e6c7a Mon Sep 17 00:00:00 2001
From: Bel LaPointe <breel@qualtrics.com>
Date: Wed, 25 Oct 2023 15:47:29 -0600
Subject: [PATCH] wip ledger/register.go

---
 cmd/clitest/main.go     | 20 +++++++++++++++
 ledger/register.go      | 57 +++++++++++++++++++++++++++++++++++++++++
 ledger/register_test.go | 39 ++++++++++++++++++++++++++++
 3 files changed, 116 insertions(+)
 create mode 100644 ledger/register.go
 create mode 100644 ledger/register_test.go

diff --git a/cmd/clitest/main.go b/cmd/clitest/main.go
index 94da0ce..c25d3f3 100644
--- a/cmd/clitest/main.go
+++ b/cmd/clitest/main.go
@@ -10,7 +10,9 @@ import (
 	"os"
 	"slices"
 	"sort"
+	"strconv"
 	"strings"
+	"time"
 
 	"github.com/go-echarts/go-echarts/v2/charts"
 	"github.com/go-echarts/go-echarts/v2/opts"
@@ -82,6 +84,24 @@ func main() {
 					register[date] = register[date].WithBPIs(bpis)
 				}
 			}
+			if predictionMonths, err := strconv.ParseInt(r.URL.Query().Get("predictionMonths"), 10, 8); err == nil && predictionMonths > 0 {
+				predictionDuration := time.Hour * 24 * 365 / 12 * time.Duration(predictionMonths)
+				if r.URL.Query().Get("predictContributions") != "" {
+					register = ledger.RegisterWithContributionPrediction(register, predictionDuration)
+				}
+				for _, nameRate := range r.URL.Query()["predictCompoundingInterest"] {
+					splits := strings.Split(nameRate, "=")
+					if len(splits) != 2 {
+						panic(splits)
+					}
+					name := splits[0]
+					rate, err := strconv.ParseFloat(splits[1], 64)
+					if err != nil {
+						panic(err)
+					}
+					register = ledger.RegisterWithCompoundingInterestPrediction(register, predictionDuration, name, rate)
+				}
+			}
 			// /MODIFIERS
 
 			nameCurrencyDateValue := map[string]map[ledger.Currency]map[string]float64{}
diff --git a/ledger/register.go b/ledger/register.go
new file mode 100644
index 0000000..09154ab
--- /dev/null
+++ b/ledger/register.go
@@ -0,0 +1,57 @@
+package ledger
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"slices"
+	"time"
+)
+
+func RegisterWithContributionPrediction(reg map[string]Balances, windowAsPercentOfTotalDuration float64) (map[string]Balances, error) {
+	times, err := registerTimesInUnix(reg)
+	if err != nil {
+		return nil, err
+	}
+	windowDuration := time.Second * time.Duration(float64(slices.Max(times)-slices.Min(times))*windowAsPercentOfTotalDuration)
+	log.Println(windowDuration)
+
+	lastReal := time.Unix(slices.Max(times), 0)
+	lastPredicted := lastReal
+	for lastPredicted.Before(lastReal.Add(windowDuration)) {
+		lastPredicted = lastPredicted.Add(time.Hour * 24 * time.Duration((45 - lastPredicted.Day())))
+		log.Println(lastPredicted)
+	}
+
+	result := make(map[string]Balances)
+	return result, io.EOF
+}
+
+func RegisterWithCompoundingInterestPrediction(reg map[string]Balances, windowAsPercentOfTotalDuration float64, name string, rate float64) (map[string]Balances, error) {
+	result := make(map[string]Balances)
+	return result, io.EOF
+}
+
+func registerTimesInUnix(reg map[string]Balances) ([]int64, error) {
+	result := make([]int64, 0, len(reg))
+	for k := range reg {
+		v, err := registerTime(k)
+		if err != nil {
+			return nil, err
+		}
+		result = append(result, v.Unix())
+	}
+	return result, nil
+}
+
+func registerTime(s string) (time.Time, error) {
+	for _, layout := range []string{
+		"2006-01-02",
+		"2006-01",
+	} {
+		if t, err := time.ParseInLocation(layout, s, time.Local); err == nil {
+			return t, err
+		}
+	}
+	return time.Time{}, fmt.Errorf("no layout matching %q", s)
+}
diff --git a/ledger/register_test.go b/ledger/register_test.go
new file mode 100644
index 0000000..b17cc0f
--- /dev/null
+++ b/ledger/register_test.go
@@ -0,0 +1,39 @@
+package ledger
+
+import (
+	"testing"
+)
+
+func TestRegisterPredictContribution(t *testing.T) {
+	// 1n t0 w weight 4
+	// 2n t1 w weight 2
+	// 4n t2 w weight 1
+	input := map[string]Balances{
+		"2001-01": Balances{"X": Balance{USD: 1}},
+		"2001-02": Balances{"X": Balance{USD: 2}},
+		"2001-03": Balances{"X": Balance{USD: 3}},
+		"2001-04": Balances{"X": Balance{USD: 4}},
+		"2001-05": Balances{"X": Balance{USD: 5}},
+		"2001-06": Balances{"X": Balance{USD: 6}},
+		"2001-07": Balances{"X": Balance{USD: 8}},
+		"2001-08": Balances{"X": Balance{USD: 10}},
+		"2001-09": Balances{"X": Balance{USD: 12}},
+		"2001-10": Balances{"X": Balance{USD: 16}},
+	}
+	// 1x4 weight 4 = 16
+	// 2x2 weight 2 = 8
+	// 4x1 weight 1 = 4
+	// (16+8+4) / (4+2+1) = 4
+	got, err := RegisterWithContributionPrediction(input, .12)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != len(input)+1 {
+		t.Error(len(got))
+	}
+	if balance, ok := got["2001-11"]; !ok {
+		t.Error(ok)
+	} else if balance["X"][USD] != 20.0 {
+		t.Error(balance)
+	}
+}