impl and test src.ledger.Files.Amend(old, new Delta)

src/ledger/file.go

@@ -26,10 +26,15 @@ func NewFiles(p string, q ...string) (Files, error) {
 }
 
 func (files Files) Amend(old, now Delta) error {
+	if now.isSet {
+		return fmt.Errorf("cannot ammend: immutable isSet is set")
+	}
+
 	xactions, err := files.transactions()
 	if err != nil {
 		return err
 	}
+
 	var transaction transaction
 	for _, xaction := range xactions {
 		if xaction.name != old.transaction {
@@ -39,23 +44,13 @@ func (files Files) Amend(old, now Delta) error {
 		break
 	}
 
-	inverted := transaction.deltas()
-	for i := range inverted {
-		inverted[i].Value *= -1
-	}
-
-	if now.isSet {
-		return fmt.Errorf("cannot ammend: immutable isSet is set")
-	}
-	transaction.date = now.Date
-	transaction.description = now.Description
 	if transaction.payee == old.Name {
 		if len(transaction.recipients) != 1 {
 			return fmt.Errorf("cannot amend: modifying original payee, but many recipients cant share new value")
 		}
-		old.Value *= -1
-		old.Name = transaction.recipients[0].name
+		transaction.payee, transaction.recipients[0].name, transaction.recipients[0].value = transaction.recipients[0].name, transaction.payee, transaction.recipients[0].value*-1.0
 	}
+
 	idx := -1
 	for i, recipient := range transaction.recipients {
 		if recipient.name == old.Name && recipient.value == old.Value {
@@ -63,16 +58,11 @@ func (files Files) Amend(old, now Delta) error {
 		}
 	}
 	if idx == -1 {
-		return fmt.Errorf("cannot amend: no recipient with name %s found to set new value", old.Name)
+		return fmt.Errorf("cannot amend: no recipient with name %q value %.2f found in %+v to set new value", old.Name, old.Value, transaction)
 	}
-	transaction.recipients[idx].name = now.Name
-	transaction.recipients[idx].value = now.Value
-	transaction.recipients[idx].currency = string(now.Currency)
-	amendedDeltas := transaction.deltas().Like(func(d Delta) bool {
-		return d.Name != transaction.payee
-	})
 
-	return files.Add(transaction.payee, append(inverted, amendedDeltas...)...)
+	old.Value *= -1
+	return files.Add(transaction.payee, []Delta{old, now}...)
 }
 
 func (files Files) TempGetLastNLines(n int) ([]string, error) {

src/ledger/file_test.go

@@ -17,13 +17,94 @@ func TestFileAmend(t *testing.T) {
 		now  Delta
 		want string
 	}{
-		//"was set payee": {
-		//"payee": {
-		//"recipient": {
-		//"multi recipient": {
+		"multi recipient": {
+			from: `
+2006-01-02  description
+               recipientA  $3.45
+               recipientB  $6.45
+               payee
+         `,
+			old: Delta{
+				Date:        "2006-01-02",
+				Name:        "recipientB",
+				Value:       6.45,
+				Currency:    "$",
+				Description: "description",
+			},
+			now: Delta{
+				Date:        "2106-11-12",
+				Name:        "recipientC",
+				Value:       16.45,
+				Currency:    "T",
+				Description: "1description",
+			},
+			want: `
+2006-01-02   description
+	recipientB			$-6.45
+	payee
+2106-11-12   1description
+	recipientC			16.45 T
+	payee`,
+		},
+		"recipient": {
+			from: `
+2006-01-02  description
+               recipient  $3.45
+               payee      $-3.45
+         `,
+			old: Delta{
+				Date:        "2006-01-02",
+				Name:        "recipient",
+				Value:       3.45,
+				Currency:    "$",
+				Description: "description",
+			},
+			now: Delta{
+				Date:        "2106-11-12",
+				Name:        "1recipient",
+				Value:       13.45,
+				Currency:    "T",
+				Description: "1description",
+			},
+			want: `
+2006-01-02   description
+	recipient			$-3.45
+	payee
+2106-11-12   1description
+	1recipient			13.45 T
+	payee`,
+		},
+		"payee": {
+			from: `
+2006-01-02  description
+               recipient  $3.45
+               payee
+         `,
+			old: Delta{
+				Date:        "2006-01-02",
+				Name:        "payee",
+				Value:       -3.45,
+				Currency:    "$",
+				Description: "description",
+			},
+			now: Delta{
+				Date:        "2106-11-12",
+				Name:        "1payee",
+				Value:       -13.45,
+				Currency:    "T",
+				Description: "1description",
+			},
+			want: `
+2006-01-02   description
+	payee			$3.45
+	recipient
+2106-11-12   1description
+	1payee			-13.45 T
+	recipient`,
+		},
 		"was set": {
 			from: `
-            2006-01-02  description
+2006-01-02  description
                recipient  $3.45
                payee
          `,
@@ -36,11 +117,18 @@ func TestFileAmend(t *testing.T) {
 			},
 			now: Delta{
 				Date:        "2106-11-12",
-				Name:        "recipient",
-				Value:       3.45,
-				Currency:    "$",
-				Description: "description",
+				Name:        "1recipient",
+				Value:       13.45,
+				Currency:    "T",
+				Description: "1description",
 			},
+			want: `
+2006-01-02   description
+	recipient			$-3.45
+	payee
+2106-11-12   1description
+	1recipient			13.45 T
+	payee`,
 		},
 	}
 
@@ -48,21 +136,28 @@ func TestFileAmend(t *testing.T) {
 		c := d
 		t.Run(name, func(t *testing.T) {
 			p := path.Join(t.TempDir(), "dat")
-			if err := os.WriteFile(p, bytes.TrimSpace([]byte(c.from)), os.ModePerm); err != nil {
+			if err := os.WriteFile(p, []byte(c.from), os.ModePerm); err != nil {
 				t.Fatal(err)
 			}
 
 			files, err := NewFiles(p)
 			if err != nil {
 				t.Fatal(err)
+			} else if deltas, err := files.Deltas(); err != nil {
+				t.Fatal(err)
+			} else if filtered := deltas.Like(func(d Delta) bool {
+				c.old.transaction = d.transaction
+				return d == c.old
+			}); len(filtered) != 1 {
+				t.Fatalf("input %s didnt include old %+v in %+v", c.from, c.old, deltas)
 			}
 
 			if err := files.Amend(c.old, c.now); err != nil {
 				t.Fatal(err)
-			} else if b, err := os.ReadFile(path.Join(path.Dir(p), "inbox.dat")); err != nil {
+			} else if b, err := os.ReadFile(path.Join(path.Dir(p), "inbox.txt")); err != nil {
 				t.Fatal(err)
-			} else if b := bytes.TrimSpace(b); string(b) != c.want {
-				t.Fatalf("expected \n\t%s\nbut got\n\t%s", c.want, b)
+			} else if string(b) != c.want {
+				t.Fatalf("expected \n\t%q\nbut got\n\t%q\n\t%s", c.want, b, b)
 			}
 		})
 	}

src/ledger/transaction.go

@@ -3,10 +3,12 @@ package ledger
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"os"
 	"regexp"
+	"slices"
 	"strconv"
 	"unicode"
 )
@@ -112,19 +114,47 @@ func (files Files) _transactions(file string) ([]transaction, error) {
 
 func readTransaction(name string, r *bufio.Reader) (transaction, error) {
 	result, err := _readTransaction(name, r)
-	if err != nil {
+	if err != nil && !errors.Is(err, io.EOF) {
 		return result, err
 	}
 	if result.empty() {
-		return result, nil
-	}
-	if result.payee == "" && len(result.recipients) < 2 {
-		return result, fmt.Errorf("found a transaction with no payee and less than 2 recipeints: %+v", result)
+		return result, err
 	}
 	if result.payee != "" && len(result.recipients) < 1 {
 		return result, fmt.Errorf("found a transaction with payee but no recipeints: %+v", result)
 	}
-	return result, nil
+	if result.payee == "" {
+		if len(result.recipients) < 2 {
+			return result, fmt.Errorf("found a transaction with no payee and less than 2 recipeints: %+v", result)
+		}
+		func() {
+			sumPerRecipient := map[string]float64{}
+			recipients := []string{}
+			for _, recipient := range result.recipients {
+				recipients = append(recipients, recipient.name)
+				sumPerRecipient[recipient.name] += recipient.value
+			}
+			slices.Sort(recipients)
+			for _, k := range recipients {
+				v := sumPerRecipient[k]
+				everyoneElse := 0.0
+				for j := range sumPerRecipient {
+					if k != j {
+						everyoneElse += sumPerRecipient[j]
+					}
+				}
+				if -1.0*v == everyoneElse {
+					result.payee = k
+					result.recipients = slices.DeleteFunc(result.recipients, func(recipient transactionRecipient) bool {
+						return recipient.name == k
+					})
+					return
+				}
+			}
+			return
+		}()
+	}
+	return result, err
 }
 
 func _readTransaction(name string, r *bufio.Reader) (transaction, error) {

src/ledger/transaction_test.go

@@ -33,13 +33,8 @@ func TestReadTransaction(t *testing.T) {
 			want: transaction{
 				date:        "2003-04-05",
 				description: "Reasoning here",
-				payee:       "",
+				payee:       "A:B",
 				recipients: []transactionRecipient{
-					{
-						name:     "A:B",
-						value:    1.0,
-						currency: "$",
-					},
 					{
 						name:     "C:D",
 						value:    -1.0,