/**
 * AAMOS Ledger — Checkpoint Engine v2 (refactored)
 * Fullständig kontroll: kassa, skulder, löner, moms, AGA, AWS, fordran, perioder, balans
 *
 * C001 Moms förfallen (2650)
 * C002 Personalskatt obetalda (2710)
 * C003 AGA obetalda (2731)  
 * C004 Oöverförd utgående moms kvar i 2611
 * C005 Fordran >60 dagar (klass 16xx)
 * C006 Konto 2990 residual
 * C007 Konto 1689 oklassificerat
 * C008 Öppen period >35 dagar
 * C009 Förra månaden ej stängd >10 dagar
 * C010 AWS/IT-kostnad >100k i månaden (6230)
 * C011 Burn rate vs kassa — månader kvar
 * C012 Balans D≠C (nödbromsen)
 */

// Pool is now injected via parameter instead of creating a new one
let _pool = null;

function getPool() {
  if (!_pool) throw new Error('Checkpoint engine not initialized: pool not set. Call initCheckpointEngine(pool) first.');
  return _pool;
}

export function initCheckpointEngine(pool) {
  _pool = pool;
}

async function q(sql, params=[]) {
  const { rows } = await getPool().query(sql, params);
  return rows;
}

function num(v) { return parseFloat(v || 0); }
function fmt(n) { return Math.round(n).toLocaleString('sv-SE') + ' kr'; }

export async function runCheckpoints(tenantId = 'landvex') {
  const tasks = [];
  const now = new Date();

  // ── Hämta alla nyckeltal i ett svep ─────────────────────────────────────
  const skulder = await q(`
    SELECT l.account_number,
           COALESCE(SUM(COALESCE(l.credit,0)-COALESCE(l.debit,0)),0) AS skuld
    FROM ledger_journal_lines l
    JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND e.status='posted'
      AND l.account_number IN ('2650','2710','2731','2611','2615','1689','2990')
    GROUP BY l.account_number`, [tenantId]);

  const sk = {};
  for (const r of skulder) sk[r.account_number] = num(r.skuld);

  // Kassa (alla likvidakonton)
  const kassaRows = await q(`
    SELECT COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS kassa
    FROM ledger_journal_lines l
    JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND e.status='posted'
      AND l.account_number IN ('1930','1932','1934','1935')`, [tenantId]);
  const kassa = num(kassaRows[0]?.kassa);

  // Burn rate — snitt senaste 3 månaderna
  const burnRows = await q(`
    SELECT AVG(period_cost) AS avg_burn FROM (
      SELECT e.period, COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS period_cost
      FROM ledger_journal_lines l
      JOIN ledger_journal_entries e ON e.id=l.entry_id
      WHERE e.tenant_id=$1 AND e.status='posted'
        AND LEFT(l.account_number,1) IN ('4','5','6','7')
        AND e.period >= to_char(NOW()-INTERVAL '3 months','YYYY-MM')
      GROUP BY e.period
    ) s`, [tenantId]);
  const burnRate = num(burnRows[0]?.avg_burn);

  // IT/AWS kostnad senaste månaden
  const currentPeriod = `${now.getFullYear()}-${String(now.getMonth()+1).padStart(2,'0')}`;
  const awsRows = await q(`
    SELECT COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS kostnad
    FROM ledger_journal_lines l
    JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND e.status='posted'
      AND l.account_number='6230' AND e.period=$2`, [tenantId, currentPeriod]);
  const awsThisMonth = num(awsRows[0]?.kostnad);

  // Fordran klass 16xx
  const fordranRows = await q(`
    SELECT l.account_number,
           MAX(COALESCE(a.name,l.account_name)) AS name,
           COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS bal,
           MIN(e.entry_date) AS earliest
    FROM ledger_journal_lines l
    JOIN ledger_journal_entries e ON e.id=l.entry_id
    LEFT JOIN ledger_accounts a ON a.tenant_id=e.tenant_id AND a.account_number=l.account_number AND a.coa_standard='BAS'
    WHERE e.tenant_id=$1 AND l.account_number LIKE '16%' AND e.status='posted'
    GROUP BY l.account_number
    HAVING COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0)>100`, [tenantId]);

  // Öppna perioder
  const openPeriods = await q(
    `SELECT period, opened_at FROM ledger_periods WHERE tenant_id=$1 AND status='open'`, [tenantId]);

  // Total balans
  const balRows = await q(`
    SELECT COALESCE(SUM(COALESCE(l.debit,0)),0) AS td,
           COALESCE(SUM(COALESCE(l.credit,0)),0) AS tc
    FROM ledger_journal_lines l
    JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND e.status='posted'`, [tenantId]);
  const td = num(balRows[0]?.td), tc = num(balRows[0]?.tc);

  // ── C001: Moms förfallen ──────────────────────────────────────────────────
  const momsSkuld = num(sk['2650']);
  if (momsSkuld > 100) {
    tasks.push({
      id: 'C001-moms', severity: 'critical',
      title: `Momsdeklaration att betala: ${fmt(momsSkuld)}`,
      description: `Konto 2650. Deklarera och betala till Skatteverket omgående. Förseningsavgift tillkommer. Bokför sedan: Debit 2650 / Kredit 1930.`,
      amount: momsSkuld, account: '2650',
      action_url: 'https://skatteverket.se/foretagochorganisationer/moms',
    });
  }

  // ── C002: Personalskatt (2710) ────────────────────────────────────────────
  const persSk = num(sk['2710']);
  if (persSk > 100) {
    tasks.push({
      id: 'C002-personalskatt', severity: 'critical',
      title: `Personalskatt att betala: ${fmt(persSk)}`,
      description: `Konto 2710. Betalas till Skatteverket senast 12:e månaden efter löneutbetalning. Bokför: Debit 2710 / Kredit 1930.`,
      amount: persSk, account: '2710',
    });
  }

  // ── C003: Arbetsgivaravgift (2731) ────────────────────────────────────────
  const agaSk = num(sk['2731']);
  if (agaSk > 100) {
    tasks.push({
      id: 'C003-aga', severity: 'critical',
      title: `Arbetsgivaravgift att betala: ${fmt(agaSk)}`,
      description: `Konto 2731. Betalas tillsammans med personalskatt. Bokför: Debit 2731 / Kredit 1930.`,
      amount: agaSk, account: '2731',
    });
  }

  // ── C004: Oöverförd utgående moms i 2611 ─────────────────────────────────
  const moms2611 = num(sk['2611']);
  if (moms2611 > 1000) {
    tasks.push({
      id: 'C004-moms2611', severity: 'high',
      title: `Oöverförd utgående moms i 2611: ${fmt(moms2611)}`,
      description: `Konto 2611 har ${fmt(moms2611)} som ej omförts till 2650. Kräver momsöverföring vid periodens slut.`,
      amount: moms2611, account: '2611',
    });
  }

  // ── C005: Fordran >60 dagar ────────────────────────────────────────────────
  for (const f of fordranRows) {
    const days = Math.floor((now - new Date(f.earliest)) / 86400000);
    const bal = num(f.bal);
    const sev = days > 90 ? 'critical' : days > 60 ? 'high' : 'medium';
    if (days > 60) {
      tasks.push({
        id: `C005-${f.account_number}`, severity: sev,
        title: `Fordran ${f.account_number} (${f.name || ''}): ${fmt(bal)} — ${days} dagar`,
        description: `Fordran är ${days} dagar gammal. Kräv betalning eller avskriv.`,
        amount: bal, account: f.account_number,
      });
    }
  }

  // ── C006: Konto 2990 residual ─────────────────────────────────────────────
  const omfRows = await q(`
    SELECT COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS bal
    FROM ledger_journal_lines l JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND l.account_number='2990' AND e.status='posted'`, [tenantId]);
  const real2990 = Math.abs(num(omfRows[0]?.bal));
  if (real2990 > 500) {
    tasks.push({
      id: 'C006-2990', severity: 'medium',
      title: `Omföringskonto 2990: ${fmt(real2990)} residual`,
      description: `Ska alltid vara 0. Kontrollera Nordea→Revolut-matchning.`,
      amount: real2990, account: '2990',
    });
  }

  // ── C007: Konto 1689 oklassificerat ──────────────────────────────────────
  const obs1689Rows = await q(`
    SELECT COALESCE(SUM(COALESCE(l.debit,0)-COALESCE(l.credit,0)),0) AS bal
    FROM ledger_journal_lines l JOIN ledger_journal_entries e ON e.id=l.entry_id
    WHERE e.tenant_id=$1 AND l.account_number='1689' AND e.status='posted'`, [tenantId]);
  const bal1689 = Math.abs(num(obs1689Rows[0]?.bal));
  if (bal1689 > 1) {
    tasks.push({
      id: 'C007-1689', severity: 'high',
      title: `Observationskonto 1689: ${fmt(bal1689)} oklassificerat`,
      description: `Poster utan styrkt kontering. Kategorisera omgående.`,
      amount: bal1689, account: '1689',
    });
  }

  // ── C008: Öppen period >35 dagar ─────────────────────────────────────────
  for (const p of openPeriods) {
    const days = Math.floor((now - new Date(p.opened_at)) / 86400000);
    if (days > 35) {
      tasks.push({
        id: `C008-${p.period}`, severity: 'high',
        title: `Period ${p.period} ej stängd (${days} dagar)`,
        description: `Stäng via period-close workflow: submit-review → approve → close.`,
        period: p.period, action_url: `/api/ledger/periods/${p.period}/submit-review`,
      });
    }
  }

  // ── C009: Förra månaden ej stängd >10 dagar ───────────────────────────────
  if (now.getDate() > 10) {
    const lm = new Date(now.getFullYear(), now.getMonth()-1, 1);
    const lastPeriod = `${lm.getFullYear()}-${String(lm.getMonth()+1).padStart(2,'0')}`;
    const prev = await q(`SELECT status FROM ledger_periods WHERE tenant_id=$1 AND period=$2`, [tenantId, lastPeriod]);
    if (prev.length > 0 && prev[0].status !== 'closed') {
      tasks.push({
        id: `C009-${lastPeriod}`, severity: 'medium',
        title: `Period ${lastPeriod} ej stängd (${now.getDate()} dagar in i ${currentPeriod})`,
        description: `Bör stängas inom 10 dagar efter månadsslut.`,
        period: lastPeriod,
      });
    }
  }

  // ── C010: IT/AWS-kostnad hög denna månad ─────────────────────────────────
  if (awsThisMonth > 80000) {
    const sev = awsThisMonth > 150000 ? 'critical' : awsThisMonth > 100000 ? 'high' : 'medium';
    tasks.push({
      id: 'C010-aws', severity: sev,
      title: `IT/molntjänst (6230) ${currentPeriod}: ${fmt(awsThisMonth)}`,
      description: `AWS + AI-kostnader denna månad. Mål: under 80 000 kr/mån. Granska prenumerationer.`,
      amount: awsThisMonth, account: '6230',
    });
  }

  // ── C011: Burn rate vs kassa ──────────────────────────────────────────────
  if (burnRate > 0) {
    const forfalletSkulder = momsSkuld + persSk + Math.max(0, agaSk);
    const kassaEfterSkulder = kassa - forfalletSkulder;
    const manaderkvar = burnRate > 0 ? kassaEfterSkulder / burnRate : 999;

    if (manaderkvar < 3) {
      tasks.push({
        id: 'C011-runway', severity: manaderkvar < 1 ? 'critical' : 'high',
        title: `Runway: ${manaderkvar.toFixed(1)} månader kassa (burn ${fmt(burnRate)}/mån)`,
        description: `Kassa ${fmt(kassa)} − skulder ${fmt(forfalletSkulder)} = ${fmt(kassaEfterSkulder)} netto. Burn rate snitt 3 mån.`,
        amount: kassaEfterSkulder,
      });
    }

    tasks.push({
      id: 'C011-info', severity: 'info',
      title: `Kassa: ${fmt(kassa)} | Skulder: ${fmt(momsSkuld + persSk + Math.max(0, agaSk))} | Burn: ${fmt(burnRate)}/mån`,
      description: `Nordea ${fmt(198921.93)} + Revolut SEK ${fmt(176598.27)} + USD ${fmt(126314.78)}. Kassa efter skulder: ${fmt(kassa - momsSkuld - persSk - Math.max(0, agaSk))}.`,
      amount: kassa,
    });
  }

  // ── C012: Balans nödbroms ─────────────────────────────────────────────────
  if (Math.abs(td - tc) > 1) {
    tasks.push({
      id: 'C012-balance', severity: 'critical',
      title: `OBALANS: diff ${(td-tc).toFixed(2)} kr — omedelbar utredning`,
      description: `Dubbel bokföring är bruten. Debet ${td.toFixed(2)} ≠ Kredit ${tc.toFixed(2)}.`,
      amount: Math.abs(td-tc),
    });
  }

  const order = { critical:0, high:1, medium:2, info:3, low:4 };
  return tasks.sort((a,b) => (order[a.severity]??9) - (order[b.severity]??9));
}

export function registerCheckpoints(app) {
  app.get('/api/ledger/tasks', async (req, res) => {
    const tenant_id = req.headers['x-tenant-id'] || req.query.tenant || 'wavult-group';
    try {
      const tasks = await runCheckpoints(tenant_id);
      const critical = tasks.filter(t => t.severity === 'critical').length;
      const high     = tasks.filter(t => t.severity === 'high').length;
      const actionable = tasks.filter(t => t.severity !== 'info');
      res.json({
        ok: true, tenant_id,
        generated_at: new Date().toISOString(),
        count: actionable.length,
        has_critical: critical > 0,
        summary: { critical, high, medium: tasks.filter(t=>t.severity==='medium').length },
        tasks,
      });
    } catch(e) {
      res.status(500).json({ ok: false, error: e.message });
    }
  });
}