import { CONTROLS, GENERATES, STEM_INFO } from './constants';
import type {
  FiveElement,
  HeavenlyStemName,
  Relation,
  TenGod,
} from './types';

export function getElementRelation(
  dayMaster: FiveElement,
  other: FiveElement,
): Relation {
  if (other === dayMaster) return 'companion';
  if (GENERATES[other] === dayMaster) return 'resource';
  if (GENERATES[dayMaster] === other) return 'output';
  if (CONTROLS[dayMaster] === other) return 'wealth';
  return 'officer';
}

export function isSupportingRelation(relation: Relation): boolean {
  return relation === 'companion' || relation === 'resource';
}

export function getTenGod(
  dayStem: HeavenlyStemName,
  otherStem: HeavenlyStemName,
): TenGod {
  const day = STEM_INFO[dayStem];
  const other = STEM_INFO[otherStem];
  const relation = getElementRelation(day.element, other.element);
  const samePolarity = day.yinYang === other.yinYang;

  switch (relation) {
    case 'companion':
      return samePolarity ? '比肩' : '劫财';
    case 'resource':
      return samePolarity ? '偏印' : '正印';
    case 'output':
      return samePolarity ? '食神' : '伤官';
    case 'wealth':
      return samePolarity ? '偏财' : '正财';
    case 'officer':
      return samePolarity ? '七杀' : '正官';
  }
}