feat(layout): plan 02 — provider consumption + layout WS + localStorage migration

2 files changed, 253 insertions, 0 deletions

diff --git a/src/features/layout/adapter/http.test.ts b/src/features/layout/adapter/http.test.ts
new file mode 100644
index 0000000..5b50715
--- /dev/null
+++ b/src/features/layout/adapter/http.test.ts
@@ -0,0 +1,136 @@
+import { DEFAULT_LAYOUT } from "@dispatch/layout-contract";
+import { describe, expect, it } from "vitest";
+import { createLayoutHttp } from "./http";
+
+/**
+ * Layout HTTP adapter tests — the OUTERMOST edge (fetch) is the only fake:
+ * a scripted `fetchImpl` returning canned Responses. No internal mocks.
+ */
+
+const LAYOUT_URL = "http://backend.test/workspaces/ws-a/layout";
+
+function fetchReturning(
+  status: number,
+  body: unknown,
+  capture?: { url?: string; init?: RequestInit | undefined },
+): typeof fetch {
+  return async (input: string | URL | Request, init?: RequestInit): Promise<Response> => {
+    if (capture !== undefined) {
+      capture.url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+      capture.init = init;
+    }
+    return new Response(JSON.stringify(body), {
+      status,
+      headers: { "Content-Type": "application/json" },
+    });
+  };
+}
+
+describe("createLayoutHttp — getTree", () => {
+  it("GETs the well-known route and unwraps { tree }", async () => {
+    const capture: { url?: string; init?: RequestInit } = {};
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(200, { tree: DEFAULT_LAYOUT }, capture),
+    );
+    const result = await http.getTree("ws-a");
+    expect(result).toEqual({ ok: true, tree: DEFAULT_LAYOUT });
+    expect(capture.url).toBe(LAYOUT_URL);
+    expect(capture.init?.method).toBeUndefined(); // GET is the default
+  });
+
+  it("maps a 404 to the no-provider signal (notFound: true)", async () => {
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(404, { error: "No layout provider is active" }),
+    );
+    const result = await http.getTree("ws-a");
+    expect(result).toEqual({
+      ok: false,
+      notFound: true,
+      error: "No layout provider is active",
+    });
+  });
+
+  it("maps a 500 to a non-notFound failure carrying the body's error", async () => {
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(500, { error: "Layout storage failure" }),
+    );
+    const result = await http.getTree("ws-a");
+    expect(result).toEqual({ ok: false, notFound: false, error: "Layout storage failure" });
+  });
+
+  it("a network failure degrades to notFound (the no-provider mode)", async () => {
+    const http = createLayoutHttp("http://backend.test", async () => {
+      throw new TypeError("Failed to fetch");
+    });
+    const result = await http.getTree("ws-a");
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.notFound).toBe(true);
+      expect(result.error).toContain("Failed to fetch");
+    }
+  });
+
+  it("a malformed 200 (SPA-fallback JSON without a tree) degrades to notFound", async () => {
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(200, { chunks: [], latestSeq: 0 }),
+    );
+    const result = await http.getTree("ws-a");
+    expect(result).toMatchObject({ ok: false, notFound: true });
+  });
+});
+
+describe("createLayoutHttp — putTree", () => {
+  it("PUTs { tree } as JSON and unwraps the echo", async () => {
+    const capture: { url?: string; init?: RequestInit } = {};
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(200, { tree: DEFAULT_LAYOUT }, capture),
+    );
+    const result = await http.putTree("ws-a", DEFAULT_LAYOUT);
+    expect(result).toEqual({ ok: true, tree: DEFAULT_LAYOUT });
+    expect(capture.init?.method).toBe("PUT");
+    expect(capture.init?.body).toBe(JSON.stringify({ tree: DEFAULT_LAYOUT }));
+  });
+
+  it("maps a 400 { error } to a validation failure (not notFound)", async () => {
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(400, { error: "root: split has no children" }),
+    );
+    const result = await http.putTree("ws-a", DEFAULT_LAYOUT);
+    expect(result).toEqual({
+      ok: false,
+      notFound: false,
+      error: "root: split has no children",
+    });
+  });
+
+  it("maps a 404 to the no-provider signal", async () => {
+    const http = createLayoutHttp("http://backend.test", fetchReturning(404, {}));
+    const result = await http.putTree("ws-a", DEFAULT_LAYOUT);
+    expect(result).toMatchObject({ ok: false, notFound: true });
+  });
+});
+
+describe("createLayoutHttp — deleteTree", () => {
+  it("DELETEs and unwraps the fresh seed", async () => {
+    const capture: { url?: string; init?: RequestInit } = {};
+    const http = createLayoutHttp(
+      "http://backend.test",
+      fetchReturning(200, { tree: DEFAULT_LAYOUT }, capture),
+    );
+    const result = await http.deleteTree("ws-a");
+    expect(result).toEqual({ ok: true, tree: DEFAULT_LAYOUT });
+    expect(capture.init?.method).toBe("DELETE");
+  });
+
+  it("maps a 404 to the no-provider signal", async () => {
+    const http = createLayoutHttp("http://backend.test", fetchReturning(404, {}));
+    const result = await http.deleteTree("ws-a");
+    expect(result).toMatchObject({ ok: false, notFound: true });
+  });
+});
diff --git a/src/features/layout/adapter/http.ts b/src/features/layout/adapter/http.ts
new file mode 100644
index 0000000..2f91e43
--- /dev/null
+++ b/src/features/layout/adapter/http.ts
@@ -0,0 +1,117 @@
+import type { LayoutTree } from "@dispatch/layout-contract";
+
+/**
+ * Layout HTTP effects (plan 02 §2.6) — the injected edge that talks to the
+ * ACTIVE layout provider's well-known routes:
+ * - `GET /workspaces/:id/layout` → `{ tree }` (read seeds a fresh workspace)
+ * - `PUT /workspaces/:id/layout` body `{ tree }` → 200 `{ tree }` / 400 `{ error }`
+ * - `DELETE /workspaces/:id/layout` → the fresh seed (reset; plan 04 adds the UI)
+ *
+ * Mirrors the plugins adapter's pattern: `httpBase` + an injected `fetchImpl`
+ * (testable without the network). The 404 is a SIGNAL, not an error: it means
+ * no layout provider is active, and the store renders its local default with
+ * ephemeral edits (never an error UI). A network failure degrades the same way.
+ */
+
+/** Outcome of a layout read/write. `notFound` distinguishes the no-provider 404. */
+export type LayoutHttpResult =
+  | { readonly ok: true; readonly tree: LayoutTree }
+  | { readonly ok: false; readonly notFound: boolean; readonly error: string };
+
+export interface LayoutHttp {
+  getTree(workspaceId: string): Promise<LayoutHttpResult>;
+  putTree(workspaceId: string, tree: LayoutTree): Promise<LayoutHttpResult>;
+  deleteTree(workspaceId: string): Promise<LayoutHttpResult>;
+}
+
+/** Read an error message from a non-2xx body (`{ error }`), tolerating junk. */
+async function errorOf(res: Response): Promise<string> {
+  try {
+    const body = (await res.json()) as { error?: unknown };
+    if (typeof body.error === "string" && body.error.length > 0) return body.error;
+  } catch {
+    // fall through
+  }
+  return `HTTP ${res.status}`;
+}
+
+/** A malformed 200 (e.g. an SPA-fallback page) degrades like a 404 — never poisons the store. */
+function malformed(): LayoutHttpResult {
+  return { ok: false, notFound: true, error: "Malformed layout response" };
+}
+
+export function createLayoutHttp(httpBase: string, fetchImpl: typeof fetch): LayoutHttp {
+  return {
+    async getTree(workspaceId): Promise<LayoutHttpResult> {
+      try {
+        const res = await fetchImpl(
+          `${httpBase}/workspaces/${encodeURIComponent(workspaceId)}/layout`,
+        );
+        if (res.status === 404) {
+          return { ok: false, notFound: true, error: "No layout provider is active" };
+        }
+        if (!res.ok) return { ok: false, notFound: false, error: await errorOf(res) };
+        const body = (await res.json()) as { tree?: unknown };
+        if (body === null || typeof body !== "object" || body.tree === undefined)
+          return malformed();
+        return { ok: true, tree: body.tree as LayoutTree };
+      } catch (err) {
+        return {
+          ok: false,
+          notFound: true,
+          error: err instanceof Error ? err.message : "Layout request failed",
+        };
+      }
+    },
+
+    async putTree(workspaceId, tree): Promise<LayoutHttpResult> {
+      try {
+        const res = await fetchImpl(
+          `${httpBase}/workspaces/${encodeURIComponent(workspaceId)}/layout`,
+          {
+            method: "PUT",
+            headers: { "Content-Type": "application/json" },
+            body: JSON.stringify({ tree }),
+          },
+        );
+        if (res.status === 404) {
+          return { ok: false, notFound: true, error: "No layout provider is active" };
+        }
+        if (!res.ok) return { ok: false, notFound: false, error: await errorOf(res) };
+        const body = (await res.json()) as { tree?: unknown };
+        if (body === null || typeof body !== "object" || body.tree === undefined)
+          return malformed();
+        return { ok: true, tree: body.tree as LayoutTree };
+      } catch (err) {
+        return {
+          ok: false,
+          notFound: true,
+          error: err instanceof Error ? err.message : "Layout request failed",
+        };
+      }
+    },
+
+    async deleteTree(workspaceId): Promise<LayoutHttpResult> {
+      try {
+        const res = await fetchImpl(
+          `${httpBase}/workspaces/${encodeURIComponent(workspaceId)}/layout`,
+          { method: "DELETE" },
+        );
+        if (res.status === 404) {
+          return { ok: false, notFound: true, error: "No layout provider is active" };
+        }
+        if (!res.ok) return { ok: false, notFound: false, error: await errorOf(res) };
+        const body = (await res.json()) as { tree?: unknown };
+        if (body === null || typeof body !== "object" || body.tree === undefined)
+          return malformed();
+        return { ok: true, tree: body.tree as LayoutTree };
+      } catch (err) {
+        return {
+          ok: false,
+          notFound: true,
+          error: err instanceof Error ? err.message : "Layout request failed",
+        };
+      }
+    },
+  };
+}