Add Parse function

CHANGELOG

@@ -1,4 +1,5 @@
 0.1.2:
+- Add Parse function
 - Add Permutations method to Cards
 - Rename library from cards to joker
 

card.go

@@ -15,6 +15,68 @@ type Card struct {
 	Suit CardSuit
 }
 
+// Parse parses a card identifier to construct a card.
+func Parse(identifier string) (Card, bool) {
+	identifier = strings.TrimSpace(strings.ToUpper(identifier))
+
+	l := len(identifier)
+	if l != 2 && l != 3 {
+		return Card{}, false
+	}
+
+	var cardFace CardFace
+	switch identifier[:l-1] {
+	case "A":
+		cardFace = FaceAce
+	case "2":
+		cardFace = Face2
+	case "3":
+		cardFace = Face3
+	case "4":
+		cardFace = Face4
+	case "5":
+		cardFace = Face5
+	case "6":
+		cardFace = Face6
+	case "7":
+		cardFace = Face7
+	case "8":
+		cardFace = Face8
+	case "9":
+		cardFace = Face9
+	case "10":
+		cardFace = Face10
+	case "J":
+		cardFace = FaceJack
+	case "Q":
+		cardFace = FaceQueen
+	case "K":
+		cardFace = FaceKing
+	case "!":
+		cardFace = FaceJoker
+	default:
+		return Card{}, false
+	}
+
+	var cardSuit CardSuit
+	switch identifier[l-1:] {
+	case "H":
+		cardSuit = SuitHearts
+	case "D":
+		cardSuit = SuitDiamonds
+	case "C":
+		cardSuit = SuitClubs
+	case "S":
+		cardSuit = SuitSpades
+	case "!":
+		cardSuit = SuitJoker
+	default:
+		return Card{}, false
+	}
+
+	return Card{cardFace, cardSuit}, true
+}
+
 // Value returns the numeric value of a card.
 func (c Card) Value() int {
 	return (int(c.Face) * 100) + int(c.Suit)
@@ -74,64 +136,12 @@ func (c Card) MarshalJSON() ([]byte, error) {
 
 // UnmarshalJSON unmarshals a Card.
 func (c *Card) UnmarshalJSON(b []byte) error {
-	var s string
-	if err := json.Unmarshal(b, &s); err != nil {
+	var identifier string
+	if err := json.Unmarshal(b, &identifier); err != nil {
 		return err
 	}
-	if sLen := len(s); sLen < 2 || sLen > 3 {
-		return fmt.Errorf("invalid card identifier: %s", s)
-	}
-
-	var cardFace CardFace
-	switch s[:len(s)-1] {
-	case "A":
-		cardFace = FaceAce
-	case "2":
-		cardFace = Face2
-	case "3":
-		cardFace = Face3
-	case "4":
-		cardFace = Face4
-	case "5":
-		cardFace = Face5
-	case "6":
-		cardFace = Face6
-	case "7":
-		cardFace = Face7
-	case "8":
-		cardFace = Face8
-	case "9":
-		cardFace = Face9
-	case "10":
-		cardFace = Face10
-	case "J":
-		cardFace = FaceJack
-	case "Q":
-		cardFace = FaceQueen
-	case "K":
-		cardFace = FaceKing
-	case "!":
-		cardFace = FaceJoker
-	default:
-		return fmt.Errorf("invalid face identifier %s", s)
-	}
-
-	var cardSuit CardSuit
-	switch s[len(s)-1:] {
-	case "H":
-		cardSuit = SuitHearts
-	case "D":
-		cardSuit = SuitDiamonds
-	case "C":
-		cardSuit = SuitClubs
-	case "S":
-		cardSuit = SuitSpades
-	case "!":
-		cardSuit = SuitJoker
-	default:
-		return fmt.Errorf("invalid suit identifier %s", s)
-	}
 
-	*c = Card{cardFace, cardSuit}
+	card, _ := Parse(identifier) // Ignore ok
+	*c = card
 	return nil
 }