1 files changed, 39 insertions, 0 deletions
diff --git a/FrontEnd/src/common.ts b/FrontEnd/src/common.ts
new file mode 100644
index 00000000..1a4f6dda
--- /dev/null
+++ b/FrontEnd/src/common.ts
@@ -0,0 +1,39 @@
+import { TFunction } from "i18next";
+
+export type BootstrapThemeColor =
+  | "primary"
+  | "secondary"
+  | "success"
+  | "danger"
+  | "warning"
+  | "info";
+
+// This error is thrown when ui goes wrong with bad logic.
+// Such as a variable should not be null, but it does.
+// This error should never occur. If it does, it indicates there is some logic bug in codes.
+export class UiLogicError extends Error {}
+
+export type I18nText =
+  | string
+  | { type: "custom"; value: string }
+  | { type: "i18n"; value: string };
+
+export function convertI18nText(text: I18nText, t: TFunction): string;
+export function convertI18nText(
+  text: I18nText | null | undefined,
+  t: TFunction
+): string | null;
+export function convertI18nText(
+  text: I18nText | null | undefined,
+  t: TFunction
+): string | null {
+  if (text == null) {
+    return null;
+  } else if (typeof text === "string") {
+    return t(text);
+  } else if (text.type === "i18n") {
+    return t(text.value);
+  } else {
+    return text.value;
+  }
+}