import {
  BRANCH_ELEMENT,
  BRANCHES,
  HIDDEN_STEMS,
  STEM_INFO,
  STEMS,
} from './constants';
import { getTenGod } from './relations';
import type {
  BaziChart,
  EarthlyBranchName,
  FourPillarsInput,
  HeavenlyStemName,
  HiddenStem,
  Pillar,
  PillarKey,
} from './types';

function isStem(value: string): value is HeavenlyStemName {
  return (STEMS as readonly string[]).includes(value);
}

function isBranch(value: string): value is EarthlyBranchName {
  return (BRANCHES as readonly string[]).includes(value);
}

export function parseGanZhi(
  ganZhi: string,
  source: string,
): [HeavenlyStemName, EarthlyBranchName] {
  const characters = [...ganZhi.trim()];
  const stem = characters[0];
  const branch = characters[1];
  if (characters.length !== 2 || !stem || !branch || !isStem(stem) || !isBranch(branch)) {
    throw new RangeError(`${source} 必须是有效的两字干支，例如“甲子”；收到：${ganZhi}`);
  }
  return [stem, branch];
}

function hiddenOrder(index: number): HiddenStem['order'] {
  if (index === 0) return 'main';
  if (index === 1) return 'middle';
  return 'residual';
}

function createPillar(
  key: PillarKey,
  ganZhi: string,
  dayStem: HeavenlyStemName,
): Pillar {
  const [stemName, branchName] = parseGanZhi(ganZhi, key);
  const stemInfo = STEM_INFO[stemName];
  const hiddenStems = HIDDEN_STEMS[branchName].map((hiddenStem, index) => {
    const info = STEM_INFO[hiddenStem];
    return {
      name: hiddenStem,
      element: info.element,
      yinYang: info.yinYang,
      tenGod: getTenGod(dayStem, hiddenStem),
      order: hiddenOrder(index),
    } satisfies HiddenStem;
  });

  return {
    key,
    ganZhi: `${stemName}${branchName}`,
    stem: {
      name: stemName,
      element: stemInfo.element,
      yinYang: stemInfo.yinYang,
      tenGod: key === 'day' ? '日主' : getTenGod(dayStem, stemName),
    },
    branch: {
      name: branchName,
      element: BRANCH_ELEMENT[branchName],
      hiddenStems,
    },
  };
}

export function createChart(pillars: FourPillarsInput): BaziChart {
  const [dayStem] = parseGanZhi(pillars.day, 'day');
  const dayInfo = STEM_INFO[dayStem];
  const year = createPillar('year', pillars.year, dayStem);
  const month = createPillar('month', pillars.month, dayStem);
  const day = createPillar('day', pillars.day, dayStem);
  const hour = createPillar('hour', pillars.hour, dayStem);

  return {
    pillars: { year, month, day, hour },
    dayMaster: {
      stem: dayStem,
      element: dayInfo.element,
      yinYang: dayInfo.yinYang,
    },
  };
}