Enhance tender estimated value resolution and add unit tests

- Updated the `ResolvedEstimatedValueAndCurrency` method to aggregate procurement lot values when the tender-level estimated value is not set, improving accuracy in value retrieval.
- Introduced the `AggregateProcurementLotEstimatedValue` function to sum estimated values from procurement lots and return the first found currency.
- Modified the `ToResponseWithLanguage` method to utilize the new estimated value resolution logic.
- Added unit tests for the new functionality, ensuring correct behavior for various scenarios in the `entity_test.go` and `budget_test.go` files.

This update improves the handling of estimated values in tenders, enhancing the overall reliability of the tender management system.

internal/tender/entity.go

@@ -305,20 +305,55 @@ func (t *Tender) GetMainOrganization() *Organization {
 
 // HasEstimatedValue returns true if the tender has an estimated value
 func (t *Tender) HasEstimatedValue() bool {
-	return t.EstimatedValue > 0
+	value, _ := t.ResolvedEstimatedValueAndCurrency()
+	return value > 0
+}
+
+// AggregateProcurementLotEstimatedValue sums lot-level estimated values and returns the first lot currency found.
+func AggregateProcurementLotEstimatedValue(lots []ProcurementLot) (value float64, currency string) {
+	for _, lot := range lots {
+		if lot.EstimatedValue <= 0 {
+			continue
+		}
+		value += lot.EstimatedValue
+		if currency == "" {
+			currency = strings.TrimSpace(lot.Currency)
+		}
+	}
+	return value, currency
+}
+
+// ResolvedEstimatedValueAndCurrency returns the tender-level estimated value when set,
+// otherwise aggregates procurement lot values for API and display use.
+func (t *Tender) ResolvedEstimatedValueAndCurrency() (float64, string) {
+	if t == nil {
+		return 0, ""
+	}
+	if t.EstimatedValue > 0 {
+		return t.EstimatedValue, strings.TrimSpace(t.Currency)
+	}
+	value, currency := AggregateProcurementLotEstimatedValue(t.ProcurementLots)
+	if value > 0 {
+		if currency == "" {
+			currency = strings.TrimSpace(t.Currency)
+		}
+		return value, currency
+	}
+	return 0, strings.TrimSpace(t.Currency)
 }
 
 // GetFormattedEstimatedValue returns formatted estimated value with currency
 func (t *Tender) GetFormattedEstimatedValue() string {
-	if !t.HasEstimatedValue() {
+	value, currency := t.ResolvedEstimatedValueAndCurrency()
+	if value <= 0 {
 		return ""
 	}
 
-	if t.Currency != "" {
-		return fmt.Sprintf("%.2f %s", t.EstimatedValue, t.Currency)
+	if currency != "" {
+		return fmt.Sprintf("%.2f %s", value, currency)
 	}
 
-	return fmt.Sprintf("%.2f", t.EstimatedValue)
+	return fmt.Sprintf("%.2f", value)
 }
 
 // UpdateStatus updates the tender status and updated timestamp

internal/tender/entity_test.go

@@ -0,0 +1,51 @@
+package tender
+
+import "testing"
+
+func TestAggregateProcurementLotEstimatedValue(t *testing.T) {
+	value, currency := AggregateProcurementLotEstimatedValue([]ProcurementLot{
+		{EstimatedValue: 100000, Currency: "EUR"},
+		{EstimatedValue: 250000, Currency: "EUR"},
+	})
+	if value != 350000 {
+		t.Fatalf("expected total 350000, got %v", value)
+	}
+	if currency != "EUR" {
+		t.Fatalf("expected currency EUR, got %q", currency)
+	}
+}
+
+func TestResolvedEstimatedValueAndCurrencyUsesLotsWhenTopLevelMissing(t *testing.T) {
+	tender := &Tender{
+		Currency: "EUR",
+		ProcurementLots: []ProcurementLot{
+			{LotID: "LOT-0001", EstimatedValue: 500000, Currency: "EUR"},
+		},
+	}
+
+	value, currency := tender.ResolvedEstimatedValueAndCurrency()
+	if value != 500000 {
+		t.Fatalf("expected 500000, got %v", value)
+	}
+	if currency != "EUR" {
+		t.Fatalf("expected EUR, got %q", currency)
+	}
+}
+
+func TestResolvedEstimatedValueAndCurrencyPrefersTopLevel(t *testing.T) {
+	tender := &Tender{
+		EstimatedValue: 900000,
+		Currency:       "USD",
+		ProcurementLots: []ProcurementLot{
+			{EstimatedValue: 100000, Currency: "EUR"},
+		},
+	}
+
+	value, currency := tender.ResolvedEstimatedValueAndCurrency()
+	if value != 900000 {
+		t.Fatalf("expected 900000, got %v", value)
+	}
+	if currency != "USD" {
+		t.Fatalf("expected USD, got %q", currency)
+	}
+}

internal/tender/form.go

@@ -277,6 +277,8 @@ func (t *Tender) ToResponseWithLanguage(language string) *TenderResponse {
 		documentURL = strings.TrimSpace(t.TenderURL)
 	}
 
+	estimatedValue, currency := t.ResolvedEstimatedValueAndCurrency()
+
 	response := &TenderResponse{
 		ID:                          t.ID.Hex(),
 		NoticePublicationID:         t.NoticePublicationID,
@@ -307,8 +309,8 @@ func (t *Tender) ToResponseWithLanguage(language string) *TenderResponse {
 		MainClassificationDescription: mainDesc,
 		MainClassificationDisplay:     classificationDisplay(mainCode, mainDesc),
 		AdditionalClassifications:     append([]string(nil), t.AdditionalClassifications...),
-		EstimatedValue:                t.EstimatedValue,
-		Currency:                      strings.TrimSpace(t.Currency),
+		EstimatedValue:                estimatedValue,
+		Currency:                      currency,
 		EstimatedValueVATBasis:        vatBasisUnspecified,
 
 		Duration:     t.Duration,