Added check for a valid game type specification when creating a new

match for a player. Also consolidated error types a little bit.

Author: Zbynek Novotny

core/core.go

@@ -127,11 +127,15 @@ func (c *Core) JoinMatch(mid MatchID, pid PlayerID, gt GameType) (MatchID, error
 	if mid != InvalidMatchID {
 		match, ok = c.matches[mid]
 		if !ok {
-			return InvalidMatchID, MatchNotFoundError{mid}
+			return InvalidMatchID, InvalidArgumentError{"Match not found:" + MatchIDToString(mid)}
 		}
 
 		match.Add(pid)
 	} else {
+		if gt == InvalidGameType {
+			return InvalidMatchID, InvalidArgumentError{"Game type specification required if no match ID defined"}
+		}
+
 		ids := PlayerIDs{pid}
 		match = NewMatchWithPlayers(gt, ids)
 		c.matches[match.ID] = match

core/errors.go

@@ -12,14 +12,12 @@ func (err IntegrityError) Error() string {
 	return "Integrity error:" + err.Message
 }
 
-// MatchNotFoundError indicates that a match
-// with the given ID could not be found
-type MatchNotFoundError struct {
-	MID MatchID
+// InvalidArgumentError indicates an
+// invalid input to a function
+type InvalidArgumentError struct {
+	Message string
 }
 
-// Error converts the error object into
-// a string presentable to the user
-func (err MatchNotFoundError) Error() string {
-	return "Match not found: " + MatchIDToString(err.MID)
+func (err InvalidArgumentError) Error() string {
+	return "Invalid argument error: " + err.Message
 }