chore: add envelope.Month method for monthly calculations

Author: morremeyer

internal/controllers/envelope.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/envelope-zero/backend/internal/models"
 	"github.com/gin-gonic/gin"
-	"github.com/rs/zerolog/log"
 )
 
 // RegisterEnvelopeRoutes registers the routes for envelopes with
@@ -82,28 +81,8 @@ func GetEnvelope(c *gin.Context) {
 
 	// If a month is requested, return only month specfic data
 	if !month.Month.IsZero() {
-		spent, err := envelope.Spent(month.Month)
-		if err != nil {
-			FetchErrorHandler(c, err)
-			return
-		}
-
-		var allocation models.Allocation
-		models.DB.First(&allocation, &models.Allocation{
-			Month: uint8(month.Month.UTC().Month()),
-			Year:  uint(month.Month.UTC().Year()),
-		})
-
-		balance := allocation.Amount.Add(spent)
-		log.Info().Str("spent", spent.String()).Str("allocation", allocation.Amount.String()).Str("balance", balance.String()).Msg("GetEnvelope")
-
 		c.JSON(http.StatusOK, gin.H{
-			"data": map[string]interface{}{
-				"allocation": allocation.Amount,
-				"spent":      spent,
-				"balance":    balance,
-				"month":      month.Month,
-			},
+			"data": envelope.Month(month.Month),
 		})
 		return
 	}

internal/controllers/envelope_test.go

@@ -24,12 +24,7 @@ type EnvelopeDetailResponse struct {
 
 type EnvelopeMonthResponse struct {
 	test.APIResponse
-	Data struct {
-		Month      time.Time       `json:"month"`
-		Spent      decimal.Decimal `json:"spent"`
-		Balance    decimal.Decimal `json:"balance"`
-		Allocation decimal.Decimal `json:"allocation"`
-	}
+	Data models.EnvelopeMonth
 }
 
 func TestGetEnvelopes(t *testing.T) {

internal/models/envelope.go

@@ -16,8 +16,16 @@ type Envelope struct {
 	Note       string   `json:"note,omitempty"`
 }
 
+// EnvelopeMonth contains data about an Envelope for a specific month.
+type EnvelopeMonth struct {
+	Month      time.Time       `json:"month"`
+	Spent      decimal.Decimal `json:"spent"`
+	Balance    decimal.Decimal `json:"balance"`
+	Allocation decimal.Decimal `json:"allocation"`
+}
+
 // Spent returns the amount spent for the month the time.Time instance is in.
-func (e Envelope) Spent(t time.Time) (decimal.Decimal, error) {
+func (e Envelope) Spent(t time.Time) decimal.Decimal {
 	// All transactions where the Envelope ID matches and that have an external account as source and an internal account as destination
 	incoming, _ := RawTransactions(
 		fmt.Sprintf("SELECT transactions.* FROM transactions, accounts AS source_accounts, accounts AS destination_accounts WHERE transactions.source_account_id = source_accounts.id AND source_accounts.external AND transactions.destination_account_id = destination_accounts.id AND NOT destination_accounts.external AND transactions.envelope_id = %v", e.ID),
@@ -44,5 +52,25 @@ func (e Envelope) Spent(t time.Time) (decimal.Decimal, error) {
 		}
 	}
 
-	return incomingSum.Sub(outgoingSum), nil
+	return incomingSum.Sub(outgoingSum)
+}
+
+// Month calculates the month specific values for an envelope and returns an EnvelopeMonth for them.
+func (e Envelope) Month(t time.Time) EnvelopeMonth {
+	spent := e.Spent(t)
+
+	var allocation Allocation
+	DB.First(&allocation, &Allocation{
+		Month: uint8(t.UTC().Month()),
+		Year:  uint(t.UTC().Year()),
+	})
+
+	balance := allocation.Amount.Add(spent)
+
+	return EnvelopeMonth{
+		Month:      t,
+		Spent:      spent,
+		Balance:    balance,
+		Allocation: allocation.Amount,
+	}
 }

internal/models/envelope_test.go

@@ -45,11 +45,9 @@ func TestEnvelopeMonthSum(t *testing.T) {
 	}
 	models.DB.Create(&transactionIn)
 
-	envelopeSpent, err := envelope.Spent(time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC))
-	assert.Nil(t, err)
-	assert.True(t, envelopeSpent.Equal(spent.Neg()), "Month calculation for 2022-01 is wrong: should be %v, but is %v", spent.Neg(), envelopeSpent)
+	envelopeMonth := envelope.Month(time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC))
+	assert.True(t, envelopeMonth.Spent.Equal(spent.Neg()), "Month calculation for 2022-01 is wrong: should be %v, but is %v", spent.Neg(), envelopeMonth.Spent)
 
-	envelopeSpent, err = envelope.Spent(time.Date(2022, 2, 1, 0, 0, 0, 0, time.UTC))
-	assert.Nil(t, err)
-	assert.True(t, envelopeSpent.Equal(spent.Neg()), "Month calculation for 2022-02 is wrong: should be %v, but is %v", spent, envelopeSpent)
+	envelopeMonth = envelope.Month(time.Date(2022, 2, 1, 0, 0, 0, 0, time.UTC))
+	assert.True(t, envelopeMonth.Spent.Equal(spent.Neg()), "Month calculation for 2022-02 is wrong: should be %v, but is %v", spent, envelopeMonth.Spent)
 }