DID implements Scanner and Valuer interfaces (#161)

* Implement Scanner and Valuer interfaces

* lint

dids/did/did.go

@@ -1,7 +1,9 @@
 package did
 
 import (
+	"database/sql/driver"
 	"errors"
+	"fmt"
 	"regexp"
 	"strings"
 )
@@ -65,6 +67,26 @@ func (d *DID) UnmarshalText(text []byte) error {
 	return nil
 }
 
+// Scan implements the Scanner interface
+func (d *DID) Scan(src any) error {
+	switch obj := src.(type) {
+	case nil:
+		return nil
+	case string:
+		if src == "" {
+			return nil
+		}
+		return d.UnmarshalText([]byte(obj))
+	default:
+		return fmt.Errorf("unsupported scan type %T", obj)
+	}
+}
+
+// Value implements the driver Valuer interface
+func (d DID) Value() (driver.Value, error) {
+	return d.String(), nil
+}
+
 // relevant ABNF rules: https://www.w3.org/TR/did-core/#did-syntax
 var (
 	pctEncodedPattern = `(?:%[0-9a-fA-F]{2})`

dids/did/did_test.go

@@ -115,3 +115,59 @@ func TestParse(t *testing.T) {
 		}
 	}
 }
+
+func TestDID_ScanValueRoundtrip(t *testing.T) {
+	tests := []struct {
+		object  did.DID
+		raw     string
+		wantErr bool
+	}{
+		{
+			raw:    "did:example:123456789abcdefghi",
+			object: MustParse("did:example:123456789abcdefghi"),
+		},
+		{
+			raw:    "did:example:123456789abcdefghi;foo=bar;baz=qux",
+			object: MustParse("did:example:123456789abcdefghi;foo=bar;baz=qux"),
+		},
+		{
+			raw:    "did:example:123456789abcdefghi?foo=bar&baz=qux",
+			object: MustParse("did:example:123456789abcdefghi?foo=bar&baz=qux"),
+		},
+		{
+			raw:    "did:example:123456789abcdefghi#keys-1",
+			object: MustParse("did:example:123456789abcdefghi#keys-1"),
+		},
+		{
+			raw:    "did:example:123456789abcdefghi?foo=bar&baz=qux#keys-1",
+			object: MustParse("did:example:123456789abcdefghi?foo=bar&baz=qux#keys-1"),
+		},
+		{
+			raw:    "did:example:123456789abcdefghi;foo=bar;baz=qux?foo=bar&baz=qux#keys-1",
+			object: MustParse("did:example:123456789abcdefghi;foo=bar;baz=qux?foo=bar&baz=qux#keys-1"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.raw, func(t *testing.T) {
+			var d did.DID
+			if err := d.Scan(tt.raw); (err != nil) != tt.wantErr {
+				t.Errorf("Scan() error = %v, wantErr %v", err, tt.wantErr)
+			}
+			assert.Equal(t, tt.object, d)
+
+			value, err := d.Value()
+			assert.NoError(t, err)
+			actual, ok := value.(string)
+			assert.True(t, ok)
+			assert.Equal(t, tt.raw, actual)
+		})
+	}
+}
+
+func MustParse(input string) did.DID {
+	d, err := did.Parse(input)
+	if err != nil {
+		panic(err)
+	}
+	return d
+}