Reorganization. Split remote/result/request. Split picsum specific api.

src/request.ts

@@ -0,0 +1,71 @@
+import { z } from "zod"
+import { Result } from "./result"
+
+// === Request Errors ===
+export type RequestError =
+  | { tag: "networkError"; error: unknown }
+  | { tag: "httpError"; status: number; statusText: string }
+  | { tag: "jsonParseError"; error: unknown }
+  | { tag: "invalidResponse"; error: z.ZodError }
+
+export const RequestError = {
+  toString(error: RequestError): string {
+    switch (error.tag) {
+      case "networkError":
+        return "Network error. Check your connection and try again."
+      case "httpError":
+        return `Server returned ${String(error.status)} ${error.statusText}.`
+      case "jsonParseError":
+        return "The server returned an invalid response."
+      case "invalidResponse":
+        return "The image data had an unexpected format."
+    }
+  },
+}
+
+// === Generic safe fetch functions ===
+export async function fetchJsonSafe(url: string): Promise<Result<unknown, RequestError>> {
+  let response: Response
+  try {
+    response = await fetch(url)
+  } catch (error: unknown) {
+    return Result.err({ tag: "networkError", error })
+  }
+
+  if (!response.ok) {
+    return Result.err({
+      tag: "httpError",
+      status: response.status,
+      statusText: response.statusText,
+    })
+  } else {
+    try {
+      const json: unknown = await response.json()
+      return Result.ok(json)
+    } catch (error: unknown) {
+      return Result.err({ tag: "jsonParseError", error })
+    }
+  }
+}
+
+// Assumes `f` is some sort of a zod parsing function that may throw `z.ZodError`
+export async function fetchJsonSafeWith<A>(
+  url: string,
+  f: (json: unknown) => A,
+): Promise<Result<A, RequestError>> {
+  const result = await fetchJsonSafe(url)
+  switch (result.tag) {
+    case "error":
+      return Result.err(result.error)
+    case "ok":
+      try {
+        return Result.ok(f(result.value))
+      } catch (error: unknown) {
+        if (error instanceof z.ZodError) {
+          return Result.err({ tag: "invalidResponse", error })
+        } else {
+          throw error
+        }
+      }
+  }
+}