import { downloadBytes, type AppServiceResult } from "./app-services.js";
import { ProjectSessionStore } from "./project-session.js";

const EXTENSIONS = new Set([".fcstd", ".step", ".stp", ".brep", ".brp", ".iges", ".igs", ".stl", ".obj", ".ply", ".svg", ".dxf", ".csv"]);

export interface NativeByteResult { module: string; format: string; fileName: string; bytes: ArrayBuffer; }

function extension(fileName: string): string { const index = fileName.lastIndexOf("."); return index >= 0 ? fileName.slice(index).toLowerCase() : ""; }

export class ExportService {
  constructor(private readonly project?: ProjectSessionStore) {}

  download(native: Partial<NativeByteResult>): AppServiceResult<{ fileName: string; bytes: number }> {
    const fileName = native.fileName ?? "FreeCAD-export";
    const bytes = native.bytes;
    const ext = extension(fileName);
    if (!bytes || !(bytes instanceof ArrayBuffer)) return { schema: "freecad-web-app-service-result/v1", service: "file.download", status: "error", error: { code: "native_bytes_unavailable", message: "Native Worker response did not include export bytes" } };
    if (!EXTENSIONS.has(ext)) return { schema: "freecad-web-app-service-result/v1", service: "file.download", status: "error", error: { code: "unsupported_extension", message: `Unsupported CAD export extension ${ext || "(none)"}` } };
    const result = downloadBytes(fileName, bytes, native.format || "application/octet-stream");
    if (result.status === "ok") this.project?.touchFile({ path: fileName, module: native.module ?? "", format: native.format ?? ext, updatedAt: new Date().toISOString() });
    return result;
  }
}