add gates.NotFound and gates.MultipleCandidates errors

README.md

@@ -4,6 +4,8 @@ Go package for working with architectural elements, in a SFO Museum context.
 
 ## Documentation
 
+[![Go Reference](https://pkg.go.dev/badge/github.com/sfomuseum/go-sfomuseum-architecture.svg)](https://pkg.go.dev/github.com/sfomuseum/go-sfomuseum-architecture)
+
 Documentation is incomplete at this time.
 
 ## Important

gates/errors.go

@@ -0,0 +1,45 @@
+package gates
+
+import (
+	"fmt"
+)
+
+type NotFound struct{ code string }
+
+func (e NotFound) Error() string {
+	return fmt.Sprintf("Gate '%s' not found", e.code)
+}
+
+func (e NotFound) String() string {
+	return e.Error()
+}
+
+type MultipleCandidates struct{ code string }
+
+func (e MultipleCandidates) Error() string {
+	return fmt.Sprintf("Multiple candidates for gate '%s'", e.code)
+}
+
+func (e MultipleCandidates) String() string {
+	return e.Error()
+}
+
+func IsNotFound(e error) bool {
+
+	switch e.(type) {
+	case NotFound, *NotFound:
+		return true
+	default:
+		return false
+	}
+}
+
+func IsMultipleCandidates(e error) bool {
+
+	switch e.(type) {
+	case MultipleCandidates, *MultipleCandidates:
+		return true
+	default:
+		return false
+	}
+}

gates/errors_test.go

@@ -0,0 +1,32 @@
+package gates
+
+import (
+	_ "fmt"
+	"testing"
+)
+
+func TestNotFound(t *testing.T) {
+
+	e := NotFound{"A6"}
+
+	if !IsNotFound(e) {
+		t.Fatalf("Expected NotFound error")
+	}
+
+	if e.String() != "Gate 'A6' not found" {
+		t.Fatalf("Invalid stringification")
+	}
+}
+
+func TestMultipleCandidates(t *testing.T) {
+
+	e := MultipleCandidates{"A6"}
+
+	if !IsMultipleCandidates(e) {
+		t.Fatalf("Expected MultipleCandidates error")
+	}
+
+	if e.String() != "Multiple candidates for gate 'A6'" {
+		t.Fatalf("Invalid stringification")
+	}
+}

gates/gates.go

@@ -45,11 +45,11 @@ func FindCurrentGateWithLookup(ctx context.Context, lookup architecture.Lookup,
 
 	switch len(current) {
 	case 0:
-		return nil, fmt.Errorf("No matches for %s", code)
+		return nil, NotFound{code}
 	case 1:
 		return current[0], nil
 	default:
-		return nil, fmt.Errorf("Multiple matches for %s (%v)", code, current)
+		return nil, MultipleCandidates{code}
 	}
 
 }