feat: create helper function to read env variables with type safety

Summary:

Test Plan:

src/libs/readEnvVariable.spec.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from "bun:test";
+
+import { readEnvVariable } from "./readEnvVariable";
+
+describe("readEnvVariable", () => {
+  it("env & variable defined, returns env value", () => {
+    expect(
+      readEnvVariable<boolean>({ ENABLE_ANIFY: "false" }, "ENABLE_ANIFY"),
+    ).toBe(false);
+  });
+
+  it("env defined but variable not defined, returns default value", () => {
+    expect(readEnvVariable<boolean>({ FOO: "bar" }, "ENABLE_ANIFY")).toBe(true);
+  });
+
+  it("env not defined, returns default value", () => {
+    expect(readEnvVariable<boolean>(undefined, "ENABLE_ANIFY")).toBe(true);
+  });
+});

src/libs/readEnvVariable.ts

@@ -0,0 +1,15 @@
+import type { Bindings } from "hono/types";
+
+import type { Env } from "~/types/env";
+
+type EnvVariable = keyof Omit<Env, "Bindings" | "Variables">;
+const defaultValues: Record<EnvVariable, any> = {
+  ENABLE_ANIFY: true,
+};
+
+export function readEnvVariable<T>(
+  env: Bindings | undefined,
+  envVariable: EnvVariable,
+): T {
+  return JSON.parse(env?.[envVariable] ?? null) ?? defaultValues[envVariable];
+}