/**
 * ═══════════════════════════════════════════════════════════════════════════
 * AAMOS Ledger Engine — Ekonomimodulens sanning
 * Port: 3250
 * Etapp 1 — Vertikal stängning
 *
 * Principer (BYGGPLAN 0.001):
 *  • Determinism före AI — alla beslut reproducerbara
 *  • Audit First — varje operation genererar event + auditpost
 *  • Tenant Isolation — kunddata korsas aldrig
 *  • Hermes — alla ekonomiska händelser publiceras via event fabric
 *  • Inga direktberoenden till andra moduler
 * ═══════════════════════════════════════════════════════════════════════════
 */

import express   from 'express';
import cors      from 'cors';
import pg        from 'pg';
import { readFileSync } from 'fs';
import { fileURLToPath } from 'url';
import { dirname, join } from 'path';
import { randomUUID }    from 'crypto';
import hermes            from './hermes.mjs';

const __dir  = dirname(fileURLToPath(import.meta.url));
const PORT   = process.env.AAMOS_LEDGER_PORT || process.env.PORT || 3250;
const { Pool } = pg;

// ── Database ─────────────────────────────────────────────────────────────────
const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  ssl: { rejectUnauthorized: false },
  max: 10,
  idleTimeoutMillis: 30000,
});

async function initSchema() {
  const sql = readFileSync(join(__dir, 'schema.sql'), 'utf8');
  await pool.query(sql);
  console.log('[ledger] Schema initialiserat');
}

// ── App ───────────────────────────────────────────────────────────────────────
const app = express();
app.use(cors());
app.use(express.json());

// ── Context helper ────────────────────────────────────────────────────────────
// Bygger trace-kontext från inkommande request.
// Propagerar trace_id om den redan finns (t.ex. från anropande service).
function buildCtx(req, entityType = null, entityId = null, decisionSource = 'user') {
  return {
    trace_id:        req.headers['x-trace-id']       || randomUUID(),
    correlation_id:  req.headers['x-correlation-id'] || randomUUID(),
    tenant_id:       req.headers['x-tenant-id']      || req.body?.tenant_id || 'wavult-group',
    user_id:         req.headers['x-user-id']        || req.body?.user_id   || 'system',
    entity_type:     entityType,
    entity_id:       entityId,
    decision_source: decisionSource,
  };
}

// ── Audit helper ──────────────────────────────────────────────────────────────
async function writeAudit(ctx, action, before = null, after = null, client = pool) {
  await client.query(
    `INSERT INTO ledger_audit_log
       (tenant_id, trace_id, correlation_id, user_id,
        entity_type, entity_id, action, decision_source, before_state, after_state)
     VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10)`,
    [
      ctx.tenant_id, ctx.trace_id, ctx.correlation_id, ctx.user_id,
      ctx.entity_type, ctx.entity_id, action, ctx.decision_source,
      before ? JSON.stringify(before) : null,
      after  ? JSON.stringify(after)  : null,
    ]
  );
}

// ══════════════════════════════════════════════════════════════════════════════
// CHART OF ACCOUNTS
// ══════════════════════════════════════════════════════════════════════════════

// GET /api/ledger/accounts — hämta kontoplan
app.get('/api/ledger/accounts', async (req, res) => {
  const tenant_id   = req.headers['x-tenant-id'] || 'wavult-group';
  const coa_standard = req.query.standard || 'BAS';
  try {
    const { rows } = await pool.query(
      `SELECT * FROM ledger_accounts
       WHERE tenant_id = $1 AND coa_standard = $2 AND is_active = TRUE
       ORDER BY account_number`,
      [tenant_id, coa_standard]
    );
    res.json({ ok: true, accounts: rows, count: rows.length });
  } catch (e) {
    res.status(500).json({ ok: false, error: e.message });
  }
});

// POST /api/ledger/accounts — lägg till konto
app.post('/api/ledger/accounts', async (req, res) => {
  const ctx = buildCtx(req, 'account');
  const { account_number, name, account_type, normal_balance,
          coa_standard = 'BAS', parent_account, vat_code, metadata = {} } = req.body;

  if (!account_number || !name || !account_type || !normal_balance) {
    return res.status(400).json({ ok: false, error: 'account_number, name, account_type, normal_balance krävs' });
  }
  if (!['asset','liability','equity','revenue','expense'].includes(account_type)) {
    return res.status(400).json({ ok: false, error: 'Ogiltigt account_type' });
  }

  try {
    const { rows } = await pool.query(
      `INSERT INTO ledger_accounts
         (tenant_id, account_number, name, account_type, normal_balance,
          coa_standard, parent_account, vat_code, metadata)
       VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9)
       ON CONFLICT (tenant_id, account_number, coa_standard) DO UPDATE
         SET name=EXCLUDED.name, account_type=EXCLUDED.account_type,
             updated_at=NOW()
       RETURNING *`,
      [ctx.tenant_id, account_number, name, account_type, normal_balance,
       coa_standard, parent_account, vat_code, JSON.stringify(metadata)]
    );
    const account = rows[0];
    ctx.entity_id = account.id;
    await writeAudit(ctx, 'created', null, account);
    await hermes.emit('finance.account.created', ctx, { account_number, name, coa_standard });
    res.status(201).json({ ok: true, account });
  } catch (e) {
    res.status(500).json({ ok: false, error: e.message });
  }
});

// ══════════════════════════════════════════════════════════════════════════════
// JOURNAL — Verifikationer
// ══════════════════════════════════════════════════════════════════════════════

// POST /api/ledger/journal — skapa verifikation (draft)
app.post('/api/ledger/journal', async (req, res) => {
  const ctx = buildCtx(req, 'journal_entry');
  const {
    entry_date, description, reference, source_type = 'manual',
    source_id, lines = [], period, fiscal_year, metadata = {}
  } = req.body;

  if (!entry_date || !description || lines.length < 2) {
    return res.status(400).json({ ok: false, error: 'entry_date, description, minst 2 rader krävs' });
  }

  // Validera dubbel bokföring
  const totalDebit  = lines.reduce((s, l) => s + (parseFloat(l.debit)  || 0), 0);
  const totalCredit = lines.reduce((s, l) => s + (parseFloat(l.credit) || 0), 0);
  if (Math.abs(totalDebit - totalCredit) > 0.01) {
    return res.status(400).json({
      ok: false,
      error: `Dubbelbokföring bruten: debet ${totalDebit.toFixed(2)} ≠ kredit ${totalCredit.toFixed(2)}`
    });
  }

  const entryDate = new Date(entry_date);
  const fy  = fiscal_year || entryDate.getFullYear();
  const per = period      || `${fy}-${String(entryDate.getMonth() + 1).padStart(2,'0')}`;

  const client = await pool.connect();
  try {
    await client.query('BEGIN');

    const { rows } = await client.query(
      `INSERT INTO ledger_journal_entries
         (tenant_id, fiscal_year, period, entry_date, description, reference,
          source_type, source_id, status, trace_id, correlation_id, user_id,
          decision_source, metadata)
       VALUES ($1,$2,$3,$4,$5,$6,$7,$8,'draft',$9,$10,$11,$12,$13)
       RETURNING *`,
      [ctx.tenant_id, fy, per, entry_date, description, reference,
       source_type, source_id, ctx.trace_id, ctx.correlation_id,
       ctx.user_id, ctx.decision_source, JSON.stringify(metadata)]
    );
    const entry = rows[0];
    ctx.entity_id = entry.id;

    // Lägg in rader
    const insertedLines = [];
    for (let i = 0; i < lines.length; i++) {
      const l = lines[i];
      if (!l.account_number) {
        throw new Error(`Rad ${i+1}: account_number saknas`);
      }
      if ((l.debit == null) === (l.credit == null)) {
        throw new Error(`Rad ${i+1}: ange antingen debit ELLER credit, inte båda/ingen`);
      }
      const { rows: lr } = await client.query(
        `INSERT INTO ledger_journal_lines
           (entry_id, tenant_id, line_number, account_number, account_name,
            debit, credit, currency, amount_base, vat_code, vat_amount,
            cost_center, project_code, description, metadata)
         VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15)
         RETURNING *`,
        [entry.id, ctx.tenant_id, i+1, l.account_number, l.account_name,
         l.debit || null, l.credit || null,
         l.currency || 'SEK', l.amount_base || (l.debit || l.credit),
         l.vat_code || null, l.vat_amount || null,
         l.cost_center || null, l.project_code || null,
         l.description || null, JSON.stringify(l.metadata || {})]
      );
      insertedLines.push(lr[0]);
    }

    await writeAudit(ctx, 'created', null, { entry, lines: insertedLines }, client);
    await client.query('COMMIT');

    await hermes.emit('finance.journal.created', ctx, {
      entry_id: entry.id, period: per, fiscal_year: fy,
      total_debit: totalDebit, description, source_type,
    });

    res.status(201).json({ ok: true, entry, lines: insertedLines });
  } catch (e) {
    await client.query('ROLLBACK');
    res.status(400).json({ ok: false, error: e.message });
  } finally {
    client.release();
  }
});

// POST /api/ledger/journal/:id/post — konterar verifikation (draft → posted)
app.post('/api/ledger/journal/:id/post', async (req, res) => {
  const { id } = req.params;
  const ctx = buildCtx(req, 'journal_entry', id);
  const client = await pool.connect();
  try {
    await client.query('BEGIN');

    const { rows } = await client.query(
      `SELECT * FROM ledger_journal_entries WHERE id=$1 AND tenant_id=$2`,
      [id, ctx.tenant_id]
    );
    if (!rows.length) return res.status(404).json({ ok: false, error: 'Verifikation hittades inte' });

    const before = rows[0];
    if (before.status !== 'draft') {
      return res.status(409).json({ ok: false, error: `Kan inte kontera: status är '${before.status}'` });
    }

    // Hämta rader för re-validering
    const { rows: lines } = await client.query(
      `SELECT * FROM ledger_journal_lines WHERE entry_id=$1 ORDER BY line_number`,
      [id]
    );
    const td = lines.reduce((s,l) => s + (parseFloat(l.debit)  || 0), 0);
    const tc = lines.reduce((s,l) => s + (parseFloat(l.credit) || 0), 0);
    if (Math.abs(td - tc) > 0.01) throw new Error(`Dubbelbokföring bruten vid kontering: ${td} ≠ ${tc}`);

    // Tilldela löpnummer
    const { rows: seqRows } = await client.query(
      `SELECT nextval('ledger_entry_number_seq') AS num`
    );
    const entry_number = seqRows[0].num;

    const { rows: updated } = await client.query(
      `UPDATE ledger_journal_entries
       SET status='posted', posted_at=NOW(), entry_number=$1
       WHERE id=$2 AND tenant_id=$3
       RETURNING *`,
      [entry_number, id, ctx.tenant_id]
    );
    const after = updated[0];

    await writeAudit(ctx, 'posted', before, after, client);
    await client.query('COMMIT');

    await hermes.emit('finance.journal.posted', ctx, {
      entry_id: id, entry_number, period: after.period,
      fiscal_year: after.fiscal_year,
    });

    res.json({ ok: true, entry: after });
  } catch (e) {
    await client.query('ROLLBACK');
    res.status(400).json({ ok: false, error: e.message });
  } finally {
    client.release();
  }
});

// GET /api/ledger/journal — lista verifikationer
app.get('/api/ledger/journal', async (req, res) => {
  const tenant_id = req.headers['x-tenant-id'] || 'wavult-group';
  const { period, fiscal_year, status, limit = 50, offset = 0 } = req.query;
  const conditions = ['e.tenant_id = $1'];
  const params = [tenant_id];
  let idx = 2;

  if (period)      { conditions.push(`e.period = $${idx++}`);       params.push(period); }
  if (fiscal_year) { conditions.push(`e.fiscal_year = $${idx++}`);  params.push(parseInt(fiscal_year)); }
  if (status)      { conditions.push(`e.status = $${idx++}`);       params.push(status); }

  try {
    const { rows } = await pool.query(
      `SELECT e.*, json_agg(l ORDER BY l.line_number) AS lines
       FROM ledger_journal_entries e
       LEFT JOIN ledger_journal_lines l ON l.entry_id = e.id
       WHERE ${conditions.join(' AND ')}
       GROUP BY e.id
       ORDER BY e.entry_date DESC, e.created_at DESC
       LIMIT $${idx++} OFFSET $${idx}`,
      [...params, parseInt(limit), parseInt(offset)]
    );
    res.json({ ok: true, entries: rows, count: rows.length });
  } catch (e) {
    res.status(500).json({ ok: false, error: e.message });
  }
});

// ══════════════════════════════════════════════════════════════════════════════
// TRIAL BALANCE — Saldobalans
// ══════════════════════════════════════════════════════════════════════════════
app.get('/api/ledger/trial-balance', async (req, res) => {
  const tenant_id = req.headers['x-tenant-id'] || 'wavult-group';
  const { period, fiscal_year } = req.query;
  if (!fiscal_year) return res.status(400).json({ ok: false, error: 'fiscal_year krävs' });

  try {
    const conditions = ['e.tenant_id=$1', 'e.fiscal_year=$2', "e.status='posted'"];
    const params = [tenant_id, parseInt(fiscal_year)];
    if (period) { conditions.push(`e.period=$3`); params.push(period); }

    const { rows } = await pool.query(
      `SELECT
         l.account_number,
         MAX(l.account_name)        AS account_name,
         COALESCE(SUM(l.debit), 0)  AS total_debit,
         COALESCE(SUM(l.credit), 0) AS total_credit,
         COALESCE(SUM(l.debit), 0) - COALESCE(SUM(l.credit), 0) AS balance
       FROM ledger_journal_lines l
       JOIN ledger_journal_entries e ON e.id = l.entry_id
       WHERE ${conditions.join(' AND ')}
       GROUP BY l.account_number
       ORDER BY l.account_number`,
      params
    );

    const totalDebit  = rows.reduce((s,r) => s + parseFloat(r.total_debit),  0);
    const totalCredit = rows.reduce((s,r) => s + parseFloat(r.total_credit), 0);

    res.json({
      ok: true,
      fiscal_year: parseInt(fiscal_year),
      period: period || 'all',
      accounts: rows,
      totals: { debit: totalDebit, credit: totalCredit, balanced: Math.abs(totalDebit - totalCredit) < 0.01 }
    });
  } catch (e) {
    res.status(500).json({ ok: false, error: e.message });
  }
});

// ══════════════════════════════════════════════════════════════════════════════
// PERIOD MANAGEMENT
// ══════════════════════════════════════════════════════════════════════════════
app.get('/api/ledger/periods', async (req, res) => {
  const tenant_id = req.headers['x-tenant-id'] || 'wavult-group';
  const { fiscal_year } = req.query;
  const cond   = ['tenant_id=$1'];
  const params = [tenant_id];
  if (fiscal_year) { cond.push('fiscal_year=$2'); params.push(parseInt(fiscal_year)); }
  const { rows } = await pool.query(
    `SELECT * FROM ledger_periods WHERE ${cond.join(' AND ')} ORDER BY fiscal_year, period`,
    params
  );
  res.json({ ok: true, periods: rows });
});

app.post('/api/ledger/periods/:period/close', async (req, res) => {
  const { period } = req.params;
  const ctx = buildCtx(req, 'period', period);
  const fiscal_year = req.body.fiscal_year || parseInt(period.split('-')[0]);

  const client = await pool.connect();
  try {
    await client.query('BEGIN');

    // Kräver att alla entries är posted
    const { rows: drafts } = await client.query(
      `SELECT COUNT(*) AS cnt FROM ledger_journal_entries
       WHERE tenant_id=$1 AND period=$2 AND status='draft'`,
      [ctx.tenant_id, period]
    );
    if (parseInt(drafts[0].cnt) > 0) {
      throw new Error(`${drafts[0].cnt} utkast finns kvar — kontera dem innan periodstängning`);
    }

    // Hämta trial balance som snapshot
    const { rows: tb } = await client.query(
      `SELECT l.account_number,
         COALESCE(SUM(l.debit),0) AS total_debit,
         COALESCE(SUM(l.credit),0) AS total_credit
       FROM ledger_journal_lines l
       JOIN ledger_journal_entries e ON e.id=l.entry_id
       WHERE e.tenant_id=$1 AND e.period=$2 AND e.status='posted'
       GROUP BY l.account_number`,
      [ctx.tenant_id, period]
    );

    const { rows: updated } = await client.query(
      `INSERT INTO ledger_periods
         (tenant_id, fiscal_year, period, status, closed_at, closed_by,
          trial_balance, trace_id, metadata)
       VALUES ($1,$2,$3,'closed',NOW(),$4,$5,$6,$7)
       ON CONFLICT (tenant_id, fiscal_year, period) DO UPDATE
         SET status='closed', closed_at=NOW(), closed_by=EXCLUDED.closed_by,
             trial_balance=EXCLUDED.trial_balance
       RETURNING *`,
      [ctx.tenant_id, fiscal_year, period, ctx.user_id,
       JSON.stringify(tb), ctx.trace_id, JSON.stringify({})]
    );

    await writeAudit(ctx, 'period_closed', null, updated[0], client);
    await client.query('COMMIT');

    await hermes.emit('finance.period.closed', ctx, {
      period, fiscal_year, closed_by: ctx.user_id,
      entry_count: tb.length,
    });

    res.json({ ok: true, period: updated[0] });
  } catch (e) {
    await client.query('ROLLBACK');
    res.status(400).json({ ok: false, error: e.message });
  } finally {
    client.release();
  }
});

// ── Health ────────────────────────────────────────────────────────────────────
app.get('/health', async (_req, res) => {
  try {
    await pool.query('SELECT 1');
    res.json({ ok: true, service: 'aamos-ledger', port: PORT, db: 'connected' });
  } catch (e) {
    res.status(503).json({ ok: false, service: 'aamos-ledger', db: 'disconnected', error: e.message });
  }
});

// ── Start ─────────────────────────────────────────────────────────────────────
try {
  await initSchema();
  app.listen(PORT, () => {
    console.log(`[aamos-ledger] Ledger Engine på :${PORT}`);
    console.log(`[aamos-ledger] Hermes → redis://127.0.0.1:6379 (kanal: aamos:hermes)`);
    console.log(`[aamos-ledger] Endpoints: /api/ledger/accounts · /api/ledger/journal · /api/ledger/trial-balance · /api/ledger/periods`);
  });
} catch (e) {
  console.error('[aamos-ledger] Startup misslyckades:', e.message);
  process.exit(1);
}