Add purchase price per month to item details

backend/internal/data/repo/repo_items.go

@@ -170,8 +170,9 @@ type (
 		WarrantyDetails  string     `json:"warrantyDetails"`
 
 		// Purchase
-		PurchaseTime types.Date `json:"purchaseTime"`
-		PurchaseFrom string     `json:"purchaseFrom"`
+		PurchaseTime          types.Date `json:"purchaseTime"`
+		PurchaseFrom          string     `json:"purchaseFrom"`
+		PurchasePricePerMonth float64    `json:"purchasePricePerMonth"`
 
 		// Sold
 		SoldTime  types.Date `json:"soldTime"`
@@ -265,6 +266,26 @@ func mapFields(fields []*ent.ItemField) []ItemField {
 	return result
 }
 
+// countMonths calculates the number of complete months between two time.Time values.
+func countMonths(start, end time.Time) int {
+	// Start after end? Doesn't make sense. Handle with care.
+	if start.After(end) {
+		return 0
+	}
+	yearDiff := end.Year() - start.Year()
+	monthDiff := int(end.Month()) - int(start.Month())
+	totalMonths := yearDiff*12 + monthDiff
+	// Adjust for cases where the end day is before the start day in the month
+	if end.Day() < start.Day() {
+		totalMonths--
+	}
+	// Double check to avoid start after end.
+	if totalMonths < 0 {
+		return 0
+	}
+	return totalMonths
+}
+
 func mapItemOut(item *ent.Item) ItemOut {
 	var attachments []ItemAttachment
 	if item.Edges.Attachments != nil {
@@ -282,6 +303,16 @@ func mapItemOut(item *ent.Item) ItemOut {
 		parent = &v
 	}
 
+	// Purchase price per month := purchase price / age in month.
+	// If age unknown -> purchase price per month = purchase price.
+	var pppm float64
+	months := countMonths(item.PurchaseTime, time.Now())
+	if item.PurchaseTime.IsZero() || months <= 0 {
+		pppm = item.PurchasePrice
+	} else {
+		pppm = item.PurchasePrice / float64(months)
+	}
+
 	return ItemOut{
 		Parent:                  parent,
 		AssetID:                 AssetID(item.AssetID),
@@ -297,8 +328,9 @@ func mapItemOut(item *ent.Item) ItemOut {
 		Manufacturer: item.Manufacturer,
 
 		// Purchase
-		PurchaseTime: types.DateFromTime(item.PurchaseTime),
-		PurchaseFrom: item.PurchaseFrom,
+		PurchaseTime:          types.DateFromTime(item.PurchaseTime),
+		PurchaseFrom:          item.PurchaseFrom,
+		PurchasePricePerMonth: pppm,
 
 		// Sold
 		SoldTime:  types.DateFromTime(item.SoldTime),

frontend/locales/en.json

@@ -457,6 +457,7 @@
         "purchase_date": "Purchase Date",
         "purchase_details": "Purchase Details",
         "purchase_price": "Purchase Price",
+        "purchase_price_per_month": "Purchase Price per Month",
         "purchased_from": "Purchased From",
         "quantity": "Quantity",
         "query_id": "Querying Asset ID Number: { id }",

frontend/pages/item/[id]/index.vue

@@ -381,6 +381,11 @@
         text: String(item.value?.purchasePrice) || "",
         type: "currency",
       },
+      {
+        name: "items.purchase_price_per_month",
+        text: String(item.value?.purchasePricePerMonth) || "",
+        type: "currency",
+      },
       {
         name: "items.purchase_date",
         text: item.value?.purchaseTime || "",