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

1 files changed, 117 insertions, 0 deletions

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",
+        };
+      }
+    },
+  };
+}