Build every ApiClient request URL in one place (closes #18)

getJSON built its URL with new URL and then overwrote the host and
path, which dropped a base path in a self-hosted apiOrigin; postJSON,
putJSON and the file and thumbnail download URLs joined strings. All of
them now go through one function next to ApiClient that accepts a path
with or without a leading slash and an origin with or without a
trailing slash or base path, and percent-encodes query parameters. A
path containing "?" or "#" is rejected.

Model: opus-5-5

test/api/client.test.ts

@@ -385,6 +385,93 @@ describe("ApiClient custom origins", () => {
     });
 });
 
+describe("ApiClient request URLs", () => {
+    it("accepts a path with or without a leading slash", async () => {
+        const { fetch, calls } = recordingFetch(
+            jsonResponse({}),
+            jsonResponse({}),
+            jsonResponse({}),
+        );
+        const client = new ApiClient({ fetch });
+        await client.getJSON("health");
+        await client.postJSON("users/ott", {});
+        await client.putJSON("/files/thumbnail", {});
+
+        expect(calls.map((c) => c.url)).toEqual([
+            "https://api.ente.io/health",
+            "https://api.ente.io/users/ott",
+            "https://api.ente.io/files/thumbnail",
+        ]);
+    });
+
+    it("accepts an apiOrigin with a trailing slash", async () => {
+        const { fetch, calls } = recordingFetch(jsonResponse({}));
+        const client = new ApiClient({
+            fetch,
+            apiOrigin: "https://my-ente.example.com/",
+        });
+        await client.getJSON("/health");
+
+        expect(calls[0]!.url).toBe("https://my-ente.example.com/health");
+    });
+
+    it("keeps a base path in a self-hosted apiOrigin for every request", async () => {
+        const body = new Uint8Array([1]);
+        const { fetch, calls } = recordingFetch(
+            jsonResponse({}),
+            jsonResponse({}),
+            jsonResponse({}),
+            streamResponse(body),
+            streamResponse(body),
+        );
+        const client = new ApiClient({
+            fetch,
+            apiOrigin: "https://example.com/ente/",
+        });
+        await client.getJSON("/collections/v2", { sinceTime: 0 });
+        await client.postJSON("/users/ott", {});
+        await client.putJSON("/files/thumbnail", {});
+        await client.getFileStream(99);
+        await client.getThumbnailStream(77);
+
+        expect(calls.map((c) => c.url)).toEqual([
+            "https://example.com/ente/collections/v2?sinceTime=0",
+            "https://example.com/ente/users/ott",
+            "https://example.com/ente/files/thumbnail",
+            "https://example.com/ente/files/download/99",
+            "https://example.com/ente/files/preview/77",
+        ]);
+    });
+
+    it("percent-encodes query parameters and skips undefined ones", async () => {
+        const { fetch, calls } = recordingFetch(jsonResponse({}));
+        const client = new ApiClient({ fetch });
+        await client.getJSON("/search", {
+            q: "a&b=c/d é",
+            limit: 5,
+            cursor: undefined,
+        });
+
+        const url = new URL(calls[0]!.url);
+        expect(url.pathname).toBe("/search");
+        expect(url.search).toBe("?q=a%26b%3Dc%2Fd+%C3%A9&limit=5");
+        expect(url.searchParams.get("q")).toBe("a&b=c/d é");
+    });
+
+    it("rejects a path that carries its own query string", async () => {
+        const { fetch, calls } = recordingFetch();
+        const client = new ApiClient({ fetch });
+
+        await expect(client.getJSON("/diff?sinceTime=0")).rejects.toThrow(
+            /must not contain "\?"/,
+        );
+        await expect(client.postJSON("/users/ott?x=1", {})).rejects.toThrow(
+            /must not contain "\?"/,
+        );
+        expect(calls).toHaveLength(0);
+    });
+});
+
 describe("ApiError", () => {
     it("throws ApiError on 4xx with status, code, requestID", async () => {
         const { fetch } = recordingFetch(