#!/usr/bin/env node
/**
 * 依工作日與相依關係計算工作包的日期、CPM 與 PERT。
 *
 * 政府辦公日曆只影響日期，不影響人天估算；取不到某年度資料時仍會跳過週末，
 * 並把警告寫到 stderr。輸出的日期採結束日不含在工期內，延續原本 dueDate 契約。
 *
 * 用法：node scripts/schedule.js --plan-file <計畫檔>
 *
 * 計畫檔格式：
 *   {
 *     "startDate": "2026-09-22",
 *     "workPackages": [
 *       { "index": 12, "title": "建立抽取契約", "days": 3, "depends": [11] },
 *       {
 *         "index": 13, "title": "驗證", "optimistic": 2,
 *         "mostLikely": 3, "pessimistic": 5, "depends": [12]
 *       }
 *     ]
 *   }
 */
import { existsSync, readFileSync } from 'node:fs';
import { ScriptError, main, parseFlags } from './lib.js';

const CALENDAR_METADATA_URL = 'https://data.gov.tw/api/front/dataset/detail?nid=14718';
const CALENDAR_URL_OVERRIDE = 'TEA_SDLC_CALENDAR_URL';
const calendarCache = new Map();

main(async () => {
  const flags = parseFlags(process.argv.slice(2), { required: ['plan-file'] });
  const plan = readPlan(flags['plan-file']);
  const order = topologicalOrder(plan.workPackages);
  const estimates = new Map(plan.workPackages.map((wp) => [wp.index, pertFor(wp)]));
  const holidays = await loadHolidays(plan, order, estimates);
  const schedule = buildSchedule(plan, order, estimates, holidays);

  return {
    startDate: plan.startDate,
    order,
    schedule: schedule.items,
    criticalPath: schedule.criticalPath,
    project: schedule.project,
  };
});

function readPlan(planFile) {
  if (!existsSync(planFile)) {
    throw new ScriptError('PLAN_FILE_MISSING', `找不到 --plan-file 指定的檔案 ${planFile}`);
  }

  let plan;
  try {
    plan = JSON.parse(readFileSync(planFile, 'utf8'));
  } catch (error) {
    throw new ScriptError('BAD_PLAN', `${planFile} 不是合法的 JSON：${error.message}`);
  }

  if (!/^\d{4}-\d{2}-\d{2}$/.test(plan.startDate ?? '') || !validDate(plan.startDate)) {
    throw new ScriptError('BAD_PLAN', `startDate 需為 YYYY-MM-DD，收到的是 ${plan.startDate}`);
  }
  if (!Array.isArray(plan.workPackages) || plan.workPackages.length === 0) {
    throw new ScriptError('BAD_PLAN', 'workPackages 需為非空陣列');
  }

  const seen = new Set();
  for (const wp of plan.workPackages) {
    // 同一個 index 出現兩次時，相依看的是後者、標題與人天卻取到前者。
    if (seen.has(wp.index)) {
      throw new ScriptError('BAD_PLAN', `工作包 #${wp.index} 在計畫裡出現了不只一次`);
    }
    seen.add(wp.index);

    if (!Number.isInteger(wp.index) || wp.index <= 0) {
      throw new ScriptError('BAD_PLAN', `工作包的 index 需為正整數，收到的是 ${wp.index}`);
    }
    if (
      wp.depends !== undefined &&
      (!Array.isArray(wp.depends) || wp.depends.some((dep) => !Number.isInteger(dep)))
    ) {
      throw new ScriptError('BAD_PLAN', `工作包 #${wp.index} 的 depends 需為整數陣列`);
    }
    const estimate = pertFor(wp);
    if (estimate === null && (!Number.isFinite(wp.days) || wp.days <= 0)) {
      throw new ScriptError('BAD_PLAN', `工作包 #${wp.index} 的 days 需為正數，收到的是 ${wp.days}`);
    }
  }
  return plan;
}

function pertFor(wp) {
  const source = wp.pert ?? wp.estimates ?? wp;
  const names = [
    ['optimistic', 'mostLikely', 'pessimistic'],
    ['optimisticDays', 'mostLikelyDays', 'pessimisticDays'],
    ['o', 'm', 'p'],
  ];
  const fields = names.find(([o, m, p]) => [o, m, p].some((name) => source[name] !== undefined));
  if (!fields) return null;

  const [optimistic, mostLikely, pessimistic] = fields.map((name) => Number(source[name]));
  if (
    ![optimistic, mostLikely, pessimistic].every((value) => Number.isFinite(value) && value > 0) ||
    optimistic > mostLikely ||
    mostLikely > pessimistic
  ) {
    throw new ScriptError(
      'BAD_PLAN',
      `工作包 #${wp.index} 的 PERT 估算需為正數且符合 optimistic ≤ mostLikely ≤ pessimistic`,
    );
  }
  const expected = (optimistic + 4 * mostLikely + pessimistic) / 6;
  const variance = ((pessimistic - optimistic) / 6) ** 2;
  return { optimistic, mostLikely, pessimistic, expected, variance };
}

/**
 * 拓撲排序：先決一定排在後續之前。排不完就代表有環。
 */
function topologicalOrder(workPackages) {
  const known = new Set(workPackages.map((wp) => wp.index));
  const remaining = new Map();

  for (const wp of workPackages) {
    for (const dep of wp.depends ?? []) {
      if (!known.has(dep)) {
        throw new ScriptError(
          'UNKNOWN_DEPENDENCY',
          `工作包 #${wp.index} 的先決 #${dep} 不在這份計畫裡`,
        );
      }
    }
    remaining.set(wp.index, new Set(wp.depends ?? []));
  }

  const order = [];
  while (remaining.size > 0) {
    const ready = [...remaining.entries()]
      .filter(([, deps]) => deps.size === 0)
      .map(([index]) => index)
      .sort((a, b) => a - b);

    if (ready.length === 0) {
      throw new ScriptError(
        'CYCLE_DETECTED',
        `相依關係成環，這些工作包彼此卡住：${[...remaining.keys()].sort((a, b) => a - b).join('、')}`,
      );
    }

    for (const index of ready) {
      order.push(index);
      remaining.delete(index);
    }
    for (const deps of remaining.values()) {
      for (const index of ready) deps.delete(index);
    }
  }
  return order;
}

async function loadHolidays(plan, order, estimates) {
  const totalDays = order.reduce((total, index) => {
    const wp = plan.workPackages.find((item) => item.index === index);
    return total + Math.ceil(estimates.get(index)?.expected ?? wp.days);
  }, 0);
  const lastDate = addCalendarDays(plan.startDate, totalDays + 366);
  const years = [];
  for (let year = yearOf(plan.startDate); year <= yearOf(lastDate); year += 1) years.push(year);

  const holidays = new Map();
  for (const year of years) holidays.set(year, await holidaysForYear(year));
  return holidays;
}

async function holidaysForYear(year) {
  if (calendarCache.has(year)) return calendarCache.get(year);

  try {
    const url = process.env[CALENDAR_URL_OVERRIDE]?.trim() || (await calendarResourceUrl(year));
    const response = await fetch(url, { signal: AbortSignal.timeout(10_000) });
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    const holidays = parseCalendar(await response.text(), year);
    calendarCache.set(year, holidays);
    return holidays;
  } catch (error) {
    const fallback = new Set();
    calendarCache.set(year, fallback);
    console.error(`警告：無法取得 ${year} 年台灣辦公日曆（${error.message}），改以週末作為非工作日`);
    return fallback;
  }
}

async function calendarResourceUrl(year) {
  const response = await fetch(CALENDAR_METADATA_URL, { signal: AbortSignal.timeout(10_000) });
  if (!response.ok) throw new Error(`日曆中繼資料 HTTP ${response.status}`);
  const body = await response.json();
  const rocYear = year - 1911;
  const resources = body.payload?.resources ?? [];
  const resource = [...resources].reverse().find(
    (item) =>
      item.file_format?.toUpperCase() === 'CSV' &&
      item.description?.startsWith(`${rocYear}年`) &&
      item.description.includes('政府行政機關辦公日曆表') &&
      !item.description.includes('Google'),
  );
  if (!resource?.url) throw new Error(`資料集沒有 ${year} 年 CSV`);
  return resource.url;
}

function parseCalendar(text, year) {
  const lines = text.replace(/^\uFEFF/, '').split(/\r?\n/).filter((line) => line.trim() !== '');
  if (lines.length < 2) throw new Error('日曆 CSV 沒有資料');
  const header = parseCsvLine(lines[0]).map((field) => field.trim());
  const dateColumn = header.indexOf('西元日期');
  const holidayColumn = header.indexOf('是否放假');
  if (dateColumn < 0 || holidayColumn < 0) throw new Error('日曆 CSV 缺少必要欄位');

  const holidays = new Set();
  for (const line of lines.slice(1)) {
    const fields = parseCsvLine(line);
    const date = fields[dateColumn]?.trim();
    const holiday = fields[holidayColumn]?.trim();
    if (/^\d{8}$/.test(date) && Number(date.slice(0, 4)) === year && holiday !== '0') {
      holidays.add(`${date.slice(0, 4)}-${date.slice(4, 6)}-${date.slice(6, 8)}`);
    }
  }
  return holidays;
}

function parseCsvLine(line) {
  const fields = [];
  let field = '';
  let quoted = false;
  for (let i = 0; i < line.length; i += 1) {
    const char = line[i];
    if (char === '"' && line[i + 1] === '"' && quoted) {
      field += '"';
      i += 1;
    } else if (char === '"') {
      quoted = !quoted;
    } else if (char === ',' && !quoted) {
      fields.push(field);
      field = '';
    } else {
      field += char;
    }
  }
  fields.push(field);
  return fields;
}

function buildSchedule(plan, order, estimates, holidays) {
  const byIndex = new Map(plan.workPackages.map((wp) => [wp.index, wp]));
  const early = new Map();
  for (const index of order) {
    const wp = byIndex.get(index);
    const duration = Math.ceil(estimates.get(index)?.expected ?? wp.days);
    const ES = (wp.depends ?? []).reduce(
      (latest, dep) => (early.get(dep).EF > latest ? early.get(dep).EF : latest),
      plan.startDate,
    );
    const EF = addWorkdays(ES, duration, holidays);
    early.set(index, { ES, EF, duration });
  }

  const projectFinish = [...early.values()].reduce(
    (latest, item) => (item.EF > latest ? item.EF : latest),
    plan.startDate,
  );
  const successors = new Map(order.map((index) => [index, []]));
  for (const wp of plan.workPackages) {
    for (const dep of wp.depends ?? []) successors.get(dep).push(wp.index);
  }

  const late = new Map();
  for (const index of [...order].reverse()) {
    const { duration } = early.get(index);
    const successorStarts = successors.get(index).map((successor) => late.get(successor).LS);
    const LF = successorStarts.length === 0 ? projectFinish : successorStarts.reduce(minDate);
    const LS = subtractWorkdays(LF, duration, holidays);
    late.set(index, { LS, LF });
  }

  const items = order.map((index) => {
    const wp = byIndex.get(index);
    const estimate = estimates.get(index);
    const { ES, EF, duration } = early.get(index);
    const { LS, LF } = late.get(index);
    const float = workdayDistance(ES, LS, holidays);
    return {
      index,
      title: wp.title,
      days: wp.days,
      dueDate: EF,
      ES,
      EF,
      LS,
      LF,
      float,
      critical: float === 0,
      expectedDays: estimate?.expected ?? wp.days,
      ...(estimate ? { pert: estimate } : {}),
    };
  });
  const criticalPath = items.filter((item) => item.critical).map((item) => item.index);
  const variance = items.reduce((total, item) => total + (item.pert?.variance ?? 0), 0);
  const expectedDuration = items.reduce((total, item) => total + (item.pert?.expected ?? item.days), 0);
  return {
    items,
    criticalPath,
    project: {
      finishDate: projectFinish,
      expectedDuration,
      variance,
      standardDeviation: Math.sqrt(variance),
    },
  };
}

function addWorkdays(date, days, holidays) {
  let current = date;
  let remaining = days;
  while (remaining > 0) {
    current = addCalendarDays(current, 1);
    if (isWorkday(current, holidays)) remaining -= 1;
  }
  return current;
}

function subtractWorkdays(date, days, holidays) {
  let current = date;
  let remaining = days;
  while (remaining > 0) {
    current = addCalendarDays(current, -1);
    if (isWorkday(current, holidays)) remaining -= 1;
  }
  return current;
}

function workdayDistance(start, end, holidays) {
  if (start === end) return 0;
  let current = start;
  let distance = 0;
  while (current < end) {
    current = addCalendarDays(current, 1);
    if (isWorkday(current, holidays)) distance += 1;
  }
  return distance;
}

function isWorkday(date, holidays) {
  const day = new Date(`${date}T00:00:00Z`).getUTCDay();
  return day !== 0 && day !== 6 && !holidays.get(yearOf(date))?.has(date);
}

function minDate(a, b) {
  return a < b ? a : b;
}

function addCalendarDays(date, days) {
  const moment = new Date(`${date}T00:00:00Z`);
  moment.setUTCDate(moment.getUTCDate() + days);
  return moment.toISOString().slice(0, 10);
}

function validDate(date) {
  const moment = new Date(`${date}T00:00:00Z`);
  return !Number.isNaN(moment.valueOf()) && moment.toISOString().slice(0, 10) === date;
}

function yearOf(date) {
  return Number(date.slice(0, 4));
}