import type { Document, Id, Registry } from '../canvas-core/types.ts';
import { fault, readMap } from '../canvas-core/values.ts';
import { openProjectEngine, type EngineOptions } from './engine.ts';
import type { StoragePort } from './storage.ts';

export type ProjectEngine = Awaited<ReturnType<typeof openProjectEngine>>;
export type WorkspaceOptions = {
  accountId: Id; workspaceId: Id; authEpoch: number; registry: Registry; storage: StoragePort;
  isCurrentIdentity(): boolean;
  adapters(projectId: Id, current: () => boolean): Pick<EngineOptions, 'persistence' | 'assets' | 'runs'>;
  onError?: (error: unknown) => void;
};

/** Workspace owns persistent projects; a view only borrows one and never closes it. */
export function createWorkspaceRuntime(options: WorkspaceOptions) {
  const projects = new Map<Id, Promise<ProjectEngine>>();
  let accepting = true, closed = false, closing: Promise<void> | undefined;
  const current = () => accepting && !closed && options.isCurrentIdentity();
  return Object.freeze({
    accountId: options.accountId, workspaceId: options.workspaceId, authEpoch: options.authEpoch, registry: options.registry,
    isCurrentIdentity: current,
    getProjects: () => readMap(projects),
    open(document: Document, versions: ReadonlyMap<Id, number>) {
      if (!current()) return Promise.reject(fault('identity_changed'));
      const existing = projects.get(document.projectId);
      if (existing) return existing.then(engine => { if (!current()) throw fault('identity_changed'); engine.refresh(document, versions); return engine; });
      const opening = openProjectEngine({ scope: { accountId: options.accountId, workspaceId: options.workspaceId, projectId: document.projectId }, registry: options.registry, document, versions, storage: options.storage, ...options.adapters(document.projectId, current), onError: options.onError,
        traversalPolicy: () => current() ? { enabled: true } : { enabled: false, code: 'identity_changed', targets: [] },
        policy: () => current() ? { enabled: true } : { enabled: false, code: 'identity_changed', targets: [] },
      });
      projects.set(document.projectId, opening);
      void opening.catch(() => { if (projects.get(document.projectId) === opening) projects.delete(document.projectId); });
      return opening.then(engine => { if (!current()) throw fault('identity_changed'); engine.refresh(document, versions); return engine; });
    },
    close() {
      accepting = false; // Fence commands/transports before awaiting pending opens or storage.
      if (closed) return Promise.resolve();
      if (closing) return closing;
      const task = (async () => {
        const results = await Promise.allSettled([...projects.values()].map(async pending => {
          let engine: ProjectEngine;
          try { engine = await pending; } catch { return; }
          await engine.close();
        }));
        const errors = results.flatMap(result => result.status === 'rejected' ? [result.reason] : []);
        if (errors.length) throw new AggregateError(errors, 'workspace_close_failed');
        options.storage.close(); projects.clear(); closed = true;
      })();
      closing = task.finally(() => { closing = undefined; });
      return closing;
    },
  });
}
export type WorkspaceRuntime = ReturnType<typeof createWorkspaceRuntime>;