'use strict';

/**
 * 智能问数 · LMDI 归因工具
 * ----------------------------------------------------------------------------
 * attribution：把营业额变化分解为 曝光效应 × 进店率效应 × 客单价效应
 * （对数平均迪氏指数法，V = expUv × clkExpRate × perActualPay）。
 * 仅在可比门店集（两期都在线）上计算；比率取加权口径。
 * 单店场景恒等式严格成立（残差≈0）；多店聚合存在混合残差，如实输出。
 */

const nlQuery = require('../../../nl-query.js');
const { ymdDash } = require('./lake.js');

const z2 = (n) => String(n).padStart(2, '0');
function dayShift(ymd, delta) {
  const d = new Date(Number(ymd.slice(0, 4)), Number(ymd.slice(4, 6)) - 1, Number(ymd.slice(6, 8)));
  d.setDate(d.getDate() + delta);
  return `${d.getFullYear()}${z2(d.getMonth() + 1)}${z2(d.getDate())}`;
}

function attributionSanitize(args, ctx) {
  const a = args || {};
  const { dateRange } = ctx;
  const dates = ctx.svc.store.datesInLake(ctx.entityKey);
  let from = /^\d{8}$/.test(String(a.from || '')) ? String(a.from) : '';
  let to = /^\d{8}$/.test(String(a.to || '')) ? String(a.to) : '';
  from = from && from >= dateRange.from && from <= dateRange.to ? from : '';
  to = to && to >= dateRange.from && to <= dateRange.to ? to : '';
  if (!from || !to || from > to) {
    if (!dates.length) return { empty: true };
    to = dates[dates.length - 1];
    from = dates[Math.max(0, dates.length - 7)];
  }
  const len = Math.max(1, Math.round(
    (new Date(Number(to.slice(0, 4)), Number(to.slice(4, 6)) - 1, Number(to.slice(6, 8)))
      - new Date(Number(from.slice(0, 4)), Number(from.slice(4, 6)) - 1, Number(from.slice(6, 8)))) / 86400000) + 1);
  const prevTo = dayShift(from, -1);
  const prevFrom = dayShift(prevTo, -(len - 1));
  let shopIds = null;
  if (Array.isArray(a.shops) && a.shops.length) {
    shopIds = nlQuery.matchShopsByName(ctx.shops, a.shops);
    if (!shopIds) throw new Error(`门店名未匹配：${a.shops.join('、')}`);
  }
  return { from, to, prevFrom, prevTo, shopIds, empty: false };
}

function windowSummary(ctx, from, to, shopIds) {
  const { svc, entityKey } = ctx;
  let rows = svc.store.queryRows(entityKey, { from, to, scope: 'shop' });
  if (shopIds) {
    const wanted = new Set(shopIds.map(String));
    rows = rows.filter((r) => wanted.has(String(r.shopId)));
  }
  const s = svc.summarizeRows(rows);
  return { rows: rows.length, expUv: s.expUv, clk: s.clkExpRate, pay: s.perActualPay, gross: s.grossAmt };
}

function attributionHandler(ctx, args) {
  const { svc } = ctx;
  if (args.empty) return { summary: '湖内暂无数据，无法归因。', data: { empty: true } };
  const { from, to, prevFrom, prevTo, shopIds } = args;
  const cur = windowSummary(ctx, from, to, shopIds);
  const prev = windowSummary(ctx, prevFrom, prevTo, shopIds);
  if (!cur.rows || !prev.rows) {
    return { summary: `本期或上期无可比数据（本期 ${cur.rows} 行 / 上期 ${prev.rows} 行），无法归因。`, data: { from, to, prevFrom, prevTo } };
  }
  const v0 = prev.gross;
  const v1 = cur.gross;
  const delta = v1 - v0;
  const factors = [
    { key: 'expUv', name: '曝光效应', cur: cur.expUv, prev: prev.expUv },
    { key: 'clkExpRate', name: '进店率效应', cur: cur.clk, prev: prev.clk },
    { key: 'perActualPay', name: '客单价效应', cur: cur.pay, prev: prev.pay },
  ];
  let lines;
  let outFactors = [];
  let residual = null;
  if (v0 <= 0 || v1 <= 0 || delta === 0 || !v0 || !v1) {
    lines = [`营业额 ${Math.round(v0)} → ${Math.round(v1)}：基期为 0 或无变化，LMDI 分解不适用。`];
  } else {
    const L = delta / (Math.log(v1) - Math.log(v0)); // 对数平均权重
    let sum = 0;
    for (const f of factors) {
      let contribution = null;
      let note = '';
      if (!f.cur || !f.prev || f.cur <= 0 || f.prev <= 0) note = '（某期为 0，无法对数分解）';
      else {
        contribution = +(L * Math.log(f.cur / f.prev)).toFixed(2);
        sum += contribution;
      }
      outFactors.push({ key: f.key, name: f.name, cur: f.cur, prev: f.prev, contribution, note });
    }
    residual = +(delta - sum).toFixed(2);
    lines = [`营业额归因（LMDI，${ymdDash(from)} ~ ${ymdDash(to)} vs ${ymdDash(prevFrom)} ~ ${ymdDash(prevTo)}，可比口径）：总变化 ${Math.round(delta)} 元，分解为——`];
    for (const f of outFactors) {
      const share = f.contribution != null && delta !== 0 ? `（占 ${(f.contribution / delta * 100).toFixed(0)}%）` : '';
      lines.push(`  ${f.name}：${f.contribution == null ? note : `${f.contribution >= 0 ? '+' : ''}${f.contribution} 元${share}`}`);
    }
    if (Math.abs(residual) > Math.abs(delta) * 0.02 + 1) {
      lines.push(`  混合残差 ${residual} 元（多店聚合与店间结构变化的交叉项，非某单一因素）。`);
    }
    const top = outFactors.filter((f) => f.contribution != null).sort((a, b) => Math.abs(b.contribution) - Math.abs(a.contribution))[0];
    if (top) lines.push(`主因：${top.name}（${top.contribution >= 0 ? '拉动' : '拖累'} ${Math.abs(top.contribution)} 元）。结论请结合业务事件解读。`);
  }
  return {
    summary: lines.join('\n'),
    data: { from, to, prevFrom, prevTo, cur, prev, factors: outFactors, residual, delta },
  };
}

module.exports = { attributionSanitize, attributionHandler };