import { WorkflowVirtualMachine } from '../WorkflowVirtualMachine';

import { Activity, ActivityElement } from './Activity.js';
import { NativeActivity } from './NativeActivity.js';

export abstract class DataContextFactory<TDataContext> {
  public abstract initDataContext(vmContext: WorkflowVirtualMachine.Context, dataContext: TDataContext): void;
  public abstract createDataContext(vmContext: WorkflowVirtualMachine.Context): TDataContext;
}

export abstract class DataContextActivity<TDataContext> extends NativeActivity {
  private readonly _dataContextFactory: DataContextFactory<TDataContext>;

  public constructor(dataContextFactory: DataContextFactory<TDataContext>, ...children: ReadonlyArray<Activity>) {
    super(...children);
    this._dataContextFactory = dataContextFactory;
  }

  public get dataContextFactory(): DataContextFactory<TDataContext> {
    return this._dataContextFactory;
  }
}
export class DataContextActivityElement<
  TDataContext,
  TActivity extends DataContextActivity<TDataContext>,
> extends ActivityElement<TActivity> {
  private readonly _dataContextFactory: DataContextFactory<TDataContext>;
  private _dataContext: TDataContext | null;

  public constructor(stackFrame: WorkflowVirtualMachine.StackFrame<TActivity>) {
    super(stackFrame);
    this._dataContextFactory = stackFrame.activity.dataContextFactory;
    this._dataContext = null;
  }

  public get dataContext(): TDataContext {
    if (this._dataContext === null) {
      this._dataContext = this._dataContextFactory.createDataContext(this.vmContext);
    }
    return this._dataContext;
  }
}