import { BehaviorSubject, Observable } from 'rxjs';
import { FieldSetModel } from './set';
import { BasicModel } from './basic';
import { ValidateOption } from '../validate';
import UniqueId from '../unique-id';

enum FormStrategy {
  /**
   * 指定 model 模式
   */
  Model,

  /**
   * 视图驱动模式
   */
  View,
}

const FORM_ID = Symbol('form');

const uniqueId = new UniqueId('form');

class FormModel<
  Children extends Record<string, BasicModel<unknown>> = Record<string, BasicModel<unknown>>
> extends FieldSetModel<Children> {
  /**
   * @internal
   */
  [FORM_ID]!: boolean;

  /** @internal */
  private readonly workingValidators = new Set<Observable<unknown>>();
  readonly isValidating$ = new BehaviorSubject(false);

  get owner(): BasicModel<any> | null {
    return this;
  }

  set owner(owner: BasicModel<any> | null) {
    // noop
  }

  get form(): FormModel | null | undefined {
    return this as FormModel<any>;
  }

  constructor(public readonly children: Children) {
    super(children, uniqueId.get());
    const keys = Object.keys(children);
    const keysLength = keys.length;
    for (let index = 0; index < keysLength; index++) {
      const name = keys[index];
      const child = children[name];
      this.registerChild(name, child);
    }
  }

  /**
   * 执行整个 `Form` 的校验，默认会递归触发所有表单元素的校验
   * @param option 表单校验的参数
   */
  validate(option: ValidateOption = ValidateOption.Default | ValidateOption.IncludeChildrenRecursively) {
    return super.validate(option);
  }

  /** @internal */
  addWorkingValidator(v: Observable<unknown>) {
    this.workingValidators.add(v);
    this.updateIsValidating();
  }

  /** @internal */
  removeWorkingValidator(v: Observable<unknown>) {
    this.workingValidators.delete(v);
    this.updateIsValidating();
  }

  /** @internal */
  private updateIsValidating() {
    const isValidating = this.workingValidators.size > 0;
    if (isValidating !== this.isValidating$.getValue()) {
      this.isValidating$.next(isValidating);
    }
  }
}

FormModel.prototype[FORM_ID] = true;

function isFormModel<Children extends Record<string, BasicModel<any>> = Record<string, BasicModel<any>>>(
  maybeModel: any,
): maybeModel is FormModel<Children> {
  return !!(maybeModel && maybeModel[FORM_ID]);
}

export { FormStrategy, FormModel, isFormModel };