impl NewBPIs(path)[currency].Get(date)

ledger/bpi.go

@@ -3,24 +3,17 @@ package ledger
 import (
 	"bufio"
 	"bytes"
-	"fmt"
 	"io"
 	"os"
 	"strconv"
 )
 
-type BPIs string
+type BPIs map[Currency]BPI
 
 type BPI map[string]float64
 
 func NewBPIs(p string) (BPIs, error) {
-	bpis := BPIs(p)
-	_, err := bpis.values()
-	return bpis, err
-}
-
-func (bpis BPIs) values() (map[Currency]BPI, error) {
-	f, err := os.Open(string(bpis))
+	f, err := os.Open(p)
 	if os.IsNotExist(err) {
 		return nil, nil
 	}
@@ -37,15 +30,17 @@ func (bpis BPIs) values() (map[Currency]BPI, error) {
 		if len(line) > 0 {
 			fields := bytes.Fields(line)
 			if len(fields) > 3 {
-				date := fields[1]
-				currency := fields[len(fields)-2]
+				date := string(fields[1])
+				currency := Currency(fields[len(fields)-2])
 				value, err := strconv.ParseFloat(string(fields[len(fields)-1][1:]), 64)
 				if err != nil {
 					return nil, err
 				}
-				return nil, fmt.Errorf("what do with %s/%s/%.2f?", date, currency, value)
+				if _, ok := result[currency]; !ok {
+					result[currency] = make(BPI)
+				}
+				result[currency][date] = value
 			}
-			return nil, fmt.Errorf("what do: %s", line)
 		}
 		if err == io.EOF {
 			return result, nil
@@ -54,3 +49,16 @@ func (bpis BPIs) values() (map[Currency]BPI, error) {
 		}
 	}
 }
+
+func (bpi BPI) Lookup(date string) float64 {
+	var closestWithoutGoingOver string
+	for k := range bpi {
+		if k <= date && k > closestWithoutGoingOver {
+			closestWithoutGoingOver = k
+		}
+	}
+	if closestWithoutGoingOver == "" {
+		return 0
+	}
+	return bpi[closestWithoutGoingOver]
+}

ledger/bpi_test.go

@@ -157,5 +157,17 @@ P 2023-10-22 07:33:56 GME $17.18
 		t.Fatal(err)
 	}
 
+	if got := got["USDC"].Lookup("2099-01-01"); got != 0 {
+		t.Error("default got != 0:", got)
+	}
+	if got := got["GME"].Lookup("2099-01-01"); got != 17.18 {
+		t.Errorf("shouldve returned latest but got %v", got)
+	}
+	if got := got["GME"].Lookup("2023-09-19"); got != 18.22 {
+		t.Errorf("shouldve returned one day before but got %v", got)
+	}
+	if got := got["GME"].Lookup("2023-09-18"); got != 18.22 {
+		t.Errorf("shouldve returned day of but got %v", got)
+	}
 	t.Log(got)
 }