import { BRANCHES } from './constants';
import type {
  EarthlyBranchName,
  FiveElement,
  HeavenlyStemName,
} from './types';

const STEM_ORDER = '甲乙丙丁戊己庚辛壬癸';

const STEM_COMBINATIONS = new Map<string, FiveElement>([
  ['甲己', 'earth'],
  ['乙庚', 'metal'],
  ['丙辛', 'water'],
  ['丁壬', 'wood'],
  ['戊癸', 'fire'],
]);

const BRANCH_SIX_COMBINATIONS = new Map<string, FiveElement>([
  ['子丑', 'earth'],
  ['寅亥', 'wood'],
  ['卯戌', 'fire'],
  ['辰酉', 'metal'],
  ['巳申', 'water'],
  ['午未', 'earth'],
]);

const BRANCH_CLASHES = new Set([
  '子午', '丑未', '寅申', '卯酉', '辰戌', '巳亥',
]);

const BRANCH_HARMS = new Set([
  '子未', '丑午', '寅巳', '卯辰', '申亥', '酉戌',
]);

export const BRANCH_THREE_COMBINATION_RULES: ReadonlyArray<{
  branches: readonly [EarthlyBranchName, EarthlyBranchName, EarthlyBranchName];
  element: FiveElement;
  label: string;
}> = [
  { branches: ['申', '子', '辰'], element: 'water', label: '申子辰三合' },
  { branches: ['亥', '卯', '未'], element: 'wood', label: '亥卯未三合' },
  { branches: ['寅', '午', '戌'], element: 'fire', label: '寅午戌三合' },
  { branches: ['巳', '酉', '丑'], element: 'metal', label: '巳酉丑三合' },
];

export const BRANCH_TRIPLE_PUNISHMENT_RULES: ReadonlyArray<{
  branches: readonly [EarthlyBranchName, EarthlyBranchName, EarthlyBranchName];
  pattern: 'yin-si-shen' | 'chou-xu-wei';
  label: string;
}> = [
  { branches: ['寅', '巳', '申'], pattern: 'yin-si-shen', label: '寅巳申三刑' },
  { branches: ['丑', '戌', '未'], pattern: 'chou-xu-wei', label: '丑戌未三刑' },
];

export const SELF_PUNISHMENT_BRANCHES: readonly EarthlyBranchName[] = [
  '辰', '午', '酉', '亥',
];

export function stemPairKey(
  left: HeavenlyStemName,
  right: HeavenlyStemName,
): string {
  return [left, right].sort((a, b) =>
    STEM_ORDER.indexOf(a) - STEM_ORDER.indexOf(b)
  ).join('');
}

export function branchPairKey(
  left: EarthlyBranchName,
  right: EarthlyBranchName,
): string {
  return [left, right].sort((a, b) =>
    BRANCHES.indexOf(a) - BRANCHES.indexOf(b)
  ).join('');
}

export function getStemCombinationElement(
  left: HeavenlyStemName,
  right: HeavenlyStemName,
): FiveElement | undefined {
  return STEM_COMBINATIONS.get(stemPairKey(left, right));
}

export function getBranchSixCombinationElement(
  left: EarthlyBranchName,
  right: EarthlyBranchName,
): FiveElement | undefined {
  return BRANCH_SIX_COMBINATIONS.get(branchPairKey(left, right));
}

export function isBranchClash(
  left: EarthlyBranchName,
  right: EarthlyBranchName,
): boolean {
  return BRANCH_CLASHES.has(branchPairKey(left, right));
}

export function isBranchHarm(
  left: EarthlyBranchName,
  right: EarthlyBranchName,
): boolean {
  return BRANCH_HARMS.has(branchPairKey(left, right));
}