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FUNCTIONS.md

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+# Standalone Functions
+
+> [!NOTE]
+> This section is useful if you are using a bundler and targetting browsers and
+> runtimes where the size of an application affects performance and load times. 
+
+Every method in this SDK is also available as a standalone function. This
+alternative API is suitable when targetting the browser or serverless runtimes
+and using a bundler to build your application since all unused functionality
+will be tree-shaken away. This includes code for unused methods, Zod schemas,
+encoding helpers and response handlers. The result is dramatically smaller
+impact on the application's final bundle size which grows very slowly as you use
+more and more functionality from this SDK.
+
+Calling methods through the main SDK class remains a valid and generally more
+more ergonomic option. Standalone functions represent an optimisation for a
+specific category of applications.
+
+## Example
+
+```typescript
+import { ProwlarrCore } from "prowlarr/core.js";
+import { apiInfoGetApi } from "prowlarr/funcs/apiInfoGetApi.js";
+import { SDKValidationError } from "prowlarr/models/errors/sdkvalidationerror.js";
+
+// Use `ProwlarrCore` for best tree-shaking performance.
+// You can create one instance of it to use across an application.
+const prowlarr = new ProwlarrCore({
+  security: {
+    xApiKey: process.env["PROWLARR_X_API_KEY"] ?? "",
+  },
+});
+
+async function run() {
+  const res = await apiInfoGetApi(prowlarr);
+
+  switch (true) {
+    case res.ok:
+      // The success case will be handled outside of the switch block
+      break;
+    case res.error instanceof SDKValidationError:
+      // Pretty-print validation errors.
+      return console.log(res.error.pretty());
+    case res.error instanceof Error:
+      return console.log(res.error);
+    default:
+      // TypeScript's type checking will fail on the following line if the above
+      // cases were not exhaustive.
+      res.error satisfies never;
+      throw new Error("Assertion failed: expected error checks to be exhaustive: " + res.error);
+  }
+
+
+  const { value: result } = res;
+
+  // Handle the result
+  console.log(result);
+}
+
+run();
+```
+
+## Result types
+
+Standalone functions differ from SDK methods in that they return a
+`Result<Value, Error>` type to capture _known errors_ and document them using
+the type system. By avoiding throwing errors, application code maintains clear
+control flow and error-handling become part of the regular flow of application
+code.
+
+> We use the term "known errors" because standalone functions, and JavaScript
+> code in general, can still throw unexpected errors such as `TypeError`s,
+> `RangeError`s and `DOMException`s. Exhaustively catching all errors may be
+> something this SDK addresses in the future. Nevertheless, there is still a lot
+> of benefit from capturing most errors and turning them into values.
+
+The second reason for this style of programming is because these functions will
+typically be used in front-end applications where exception throwing is
+sometimes discouraged or considered unidiomatic. React and similar ecosystems
+and libraries tend to promote this style of programming so that components
+render useful content under all states (loading, success, error and so on).
+
+The general pattern when calling standalone functions looks like this:
+
+```typescript
+import { Core } from "<sdk-package-name>";
+import { fetchSomething } from "<sdk-package-name>/funcs/fetchSomething.js";
+
+const client = new Core();
+
+async function run() {
+  const result = await fetchSomething(client, { id: "123" });
+  if (!result.ok) {
+    // You can throw the error or handle it. It's your choice now.
+    throw result.error;
+  }
+
+  console.log(result.value);
+}
+
+run();
+```
+
+Notably, `result.error` above will have an explicit type compared to a try-catch
+variation where the error in the catch block can only be of type `unknown` (or
+`any` depending on your TypeScript settings).