feat(web): panneau Fichiers — navigation projet + téléchargements fichier/dossier ZIP — #211

frontend/src/adapters/http/httpInvoker.ts

@@ -39,6 +39,7 @@ export type FetchLike = (
   /** Parsed JSON body (may reject/return undefined for empty bodies). */
   json(): Promise<unknown>;
   text(): Promise<string>;
+  blob?(): Promise<Blob>;
 }>;
 
 /**
@@ -182,4 +183,51 @@ export class HttpInvoker {
     }
     return parsed as T;
   }
+
+  async download(path: string, filename: string, what = `GET ${path}`): Promise<void> {
+    const headers: Record<string, string> = {};
+    if (this.token) headers.Authorization = `Bearer ${this.token}`;
+
+    let res: Awaited<ReturnType<FetchLike>>;
+    try {
+      res = await this.fetchImpl(`${this.baseUrl}${path}`, {
+        method: "GET",
+        headers,
+        credentials: "same-origin",
+      });
+    } catch (networkError) {
+      const err: GatewayError = {
+        code: "TRANSPORT_ERROR",
+        message: `HTTP request for ${what} failed: ${String(networkError)}`,
+      };
+      throw err;
+    }
+
+    if (!res.ok) {
+      if (res.status === 401) this.onUnauthorized?.();
+      let parsed: unknown;
+      try {
+        parsed = await res.json();
+      } catch {
+        parsed = undefined;
+      }
+      throw toGatewayError(parsed, `${what} failed (HTTP ${res.status})`);
+    }
+
+    const blob = res.blob ? await res.blob() : new Blob([await res.text()]);
+    triggerBrowserDownload(blob, filename);
+  }
+}
+
+function triggerBrowserDownload(blob: Blob, filename: string): void {
+  if (typeof document === "undefined" || typeof URL === "undefined") return;
+  const href = URL.createObjectURL(blob);
+  const link = document.createElement("a");
+  link.href = href;
+  link.download = filename;
+  link.rel = "noopener";
+  document.body.appendChild(link);
+  link.click();
+  link.remove();
+  URL.revokeObjectURL(href);
 }