Class CompositionImpl

packages/sdk/src/session.ts:68–619

// ─── Implementation ───────────────────────────────────────────────────────────

class CompositionImpl implements Composition {
  private readonly parsed: ParsedDocument;
  private readonly persist: PersistAdapter | undefined;
  readonly preview: PreviewAdapter | undefined;

  /** Accumulated override-set — T3 embedded mode fold contract. */
  private overrides: OverrideSet;

  /** Lazily-built element snapshot, invalidated on every mutation. */
  private elementsCache: ElementSnapshot[] | null = null;

  private currentSelection: string[] = [];

  private changeHandlers: Array<() => void> = [];
  private selectionHandlers: Array<(ids: string[]) => void> = [];
  private patchHandlers: Array<(e: PatchEvent) => void> = [];
  private errorHandlers: Array<(e: PersistErrorEvent) => void> = [];
  private previewSelectionUnsubscribe: (() => void) | null = null;

  /** Attached by openComposition() for standalone mode. */
  private historyModule: HistoryModule | null = null;
  private persistQueueModule: PersistQueueModule | null = null;

  /** Batching state: accumulates patches from multiple dispatches. */
  private batchDepth = 0;
  private batchForward: JsonPatchOp[] = [];
  private batchInverse: JsonPatchOp[] = [];
  private batchOpTypes: string[] = [];
  private batchOrigin: unknown = ORIGIN_LOCAL;
  /** Override-set state at outermost batch entry — restored if the batch throws. */
  private batchOverridesSnapshot: OverrideSet = {};

  constructor(parsed: ParsedDocument, opts: OpenCompositionOptions) {
    this.parsed = parsed;
    this.persist = opts.persist;
    this.preview = opts.preview;
    this.overrides = { ...(opts.overrides ?? {}) };
    this.previewSelectionUnsubscribe =
      this.preview?.on("selection", (ids) => this.updateSelection(ids)) ?? null;
  }

  attachHistory(module: HistoryModule): void {
    this.historyModule = module;
  }

  attachPersistQueue(module: PersistQueueModule): void {
    this.persistQueueModule = module;
  }

  _fireError(e: PersistErrorEvent): void {
    this.errorHandlers.forEach((h) => h(e));
  }

  // ── Typed methods (F10 layer 1) ─────────────────────────────────────────────

  setStyle(id: HfId, styles: Record<string, string | null>): void {
    this.dispatch({ type: "setStyle", target: id, styles });
  }