feat: sum available for budgeting

Author: morremeyer

api/docs.go

@@ -2676,6 +2676,10 @@ const docTemplate = `{
         "models.BudgetMonth": {
             "type": "object",
             "properties": {
+                "available": {
+                    "type": "number",
+                    "example": 217.34
+                },
                 "budgeted": {
                     "type": "number",
                     "example": 2100

api/swagger.json

@@ -2664,6 +2664,10 @@
         "models.BudgetMonth": {
             "type": "object",
             "properties": {
+                "available": {
+                    "type": "number",
+                    "example": 217.34
+                },
                 "budgeted": {
                     "type": "number",
                     "example": 2100

api/swagger.yaml

@@ -430,6 +430,9 @@ definitions:
     type: object
   models.BudgetMonth:
     properties:
+      available:
+        example: 217.34
+        type: number
       budgeted:
         example: 2100
         type: number

pkg/controllers/budget.go

@@ -358,13 +358,21 @@ func GetBudgetMonth(c *gin.Context) {
 		return
 	}
 
+	// Get the available sum for budgeting
+	available, err := budget.Available(month.Month)
+	if err != nil {
+		httperrors.Handler(c, err)
+		return
+	}
+
 	c.JSON(http.StatusOK, BudgetMonthResponse{Data: models.BudgetMonth{
 		ID:        budget.ID,
 		Name:      budget.Name,
 		Month:     month.Month,
 		Income:    income,
 		Budgeted:  budgeted,
 		Envelopes: envelopeMonths,
+		Available: available,
 	}})
 }
 

pkg/models/budget.go

@@ -31,6 +31,7 @@ type BudgetMonth struct {
 	Month     time.Time       `json:"month" example:"2006-05-01T00:00:00.000000Z"`       // This is always set to 00:00 UTC on the first of the month.
 	Budgeted  decimal.Decimal `json:"budgeted" example:"2100"`
 	Income    decimal.Decimal `json:"income" example:"2317.34"`
+	Available decimal.Decimal `json:"available" example:"217.34"`
 	Envelopes []EnvelopeMonth `json:"envelopes"`
 }
 
@@ -88,6 +89,26 @@ func (b Budget) Income(t time.Time) (decimal.Decimal, error) {
 	return income.Decimal, nil
 }
 
+// Available calculates the amount that is available to be budgeted in the specified monht.
+func (b Budget) Available(month time.Time) (decimal.Decimal, error) {
+	income, err := b.TotalIncome(month)
+	if err != nil {
+		return decimal.Zero, err
+	}
+
+	overspent, err := b.Overspent(month)
+	if err != nil {
+		return decimal.Zero, err
+	}
+
+	budgeted, err := b.TotalBudgeted(month)
+	if err != nil {
+		return decimal.Zero, err
+	}
+
+	return income.Sub(overspent).Sub(budgeted), nil
+}
+
 // TotalIncome calculates the total income over all time.
 func (b Budget) TotalIncome(month time.Time) (decimal.Decimal, error) {
 	// Only use the year and month values, everything else is reset to the start
@@ -169,7 +190,7 @@ func (b Budget) Overspent(month time.Time) (decimal.Decimal, error) {
 
 	var overspent decimal.Decimal
 	for _, envelope := range envelopes {
-		spent := envelope.Spent(month)
+		spent := envelope.Spent(month.AddDate(0, -1, 0))
 		if spent.IsNegative() {
 			overspent = overspent.Add(spent.Neg())
 		}

pkg/models/budget_test.go

@@ -275,7 +275,11 @@ func (suite *TestSuiteEnv) TestBudgetCalculations() {
 	// Verify overspent calculation for month with spend
 	overspent, err = budget.Overspent(marchFifteenthTwentyTwentyTwo)
 	assert.Nil(suite.T(), err)
-	assert.True(suite.T(), overspent.Equal(decimal.NewFromFloat(130.62)), "Overspent is %s, should be 130.62", overspent)
+	assert.True(suite.T(), overspent.Equal(decimal.NewFromFloat(20)), "Overspent is %s, should be 20", overspent)
+
+	available, err := budget.Available(marchFifteenthTwentyTwentyTwo)
+	assert.Nil(suite.T(), err)
+	assert.True(suite.T(), available.Equal(decimal.NewFromFloat(4513)), "Available is %s, should be 4513", available)
 }
 
 func (suite *TestSuiteEnv) TestMonthIncomeNoTransactions() {