import { BasicBuilder } from './basic';
import { FieldSetModel, $FieldSetValue } from '../models';
import { Maybe, Some, None, or } from '../maybe';

export type $FieldSetBuilderChildren<ChildBuilders extends Record<string, BasicBuilder<any, any>>> = {
  [Key in keyof ChildBuilders]: ChildBuilders[Key]['phantomModel'];
};

export type $FieldSetBuilderDefaultValue<ChildBuilders extends Record<string, BasicBuilder<any, any>>> = Partial<
  $FieldSetValue<$FieldSetBuilderChildren<ChildBuilders>>
>;

export class FieldSetBuilder<ChildBuilders extends Record<string, BasicBuilder<any, any>>> extends BasicBuilder<
  $FieldSetValue<$FieldSetBuilderChildren<ChildBuilders>>,
  FieldSetModel<$FieldSetBuilderChildren<ChildBuilders>>
> {
  constructor(private readonly _childBuilders: ChildBuilders) {
    super();
  }

  build(defaultValues?: Maybe<$FieldSetBuilderDefaultValue<ChildBuilders>>) {
    const defaults = or<$FieldSetBuilderDefaultValue<ChildBuilders>>(defaultValues, () => ({}));
    const children = {} as $FieldSetBuilderChildren<ChildBuilders>;
    Object.keys(this._childBuilders).forEach((key: keyof ChildBuilders) => {
      const childBuilder = this._childBuilders[key];
      if (defaults.hasOwnProperty(key)) {
        children[key] = childBuilder.build(Some(defaults[key]));
      } else {
        children[key] = childBuilder.build(None());
      }
    });
    const model = new FieldSetModel<$FieldSetBuilderChildren<ChildBuilders>>(children);
    model.validators = this._validators;
    return model;
  }
}