refactor code to fewer files; remove unused code

core/keypad_dimension.go

@@ -0,0 +1,40 @@
+package core
+
+import "errors"
+
+type KeypadDimension struct {
+	AttrsPerKey int `json:"attrs_per_key"`
+	NumbOfKeys  int `json:"numb_of_keys"`
+}
+
+func (kp *KeypadDimension) TotalAttrs() int {
+	return kp.AttrsPerKey * kp.NumbOfKeys
+}
+
+func (kp *KeypadDimension) IsDispersable() bool {
+	return kp.AttrsPerKey <= kp.NumbOfKeys
+}
+
+func (kp *KeypadDimension) IsValidKeypadDimension() error {
+	if KeypadMin.AttrsPerKey > kp.AttrsPerKey || KeypadMax.AttrsPerKey < kp.AttrsPerKey || KeypadMin.NumbOfKeys > kp.NumbOfKeys || KeypadMax.NumbOfKeys < kp.NumbOfKeys {
+		return errors.New("keypad dimensions out of range")
+	}
+	return nil
+}
+
+var (
+	KeypadMax = KeypadDimension{
+		AttrsPerKey: 16,
+		NumbOfKeys:  15,
+	}
+
+	KeypadMin = KeypadDimension{
+		AttrsPerKey: 5,
+		NumbOfKeys:  4,
+	}
+
+	KeypadDefault = KeypadDimension{
+		AttrsPerKey: 14,
+		NumbOfKeys:  7,
+	}
+)