import type { FastifyInstance } from 'fastify';
import { z } from 'zod';
import { randomUUID } from 'node:crypto';
import type { PoolConnection } from 'mysql2/promise';
import { calculatePrice } from '@kc/platform/pricing';
import { one, query, run, tx } from '../../core/db.js';
import { audit } from '../../core/audit.js';
import { enqueue } from '../../core/jobs.js';
import { clientIp, requireAuth, requirePermission } from '../../core/auth.js';
import { badRequest, conflict, forbidden, notFound } from '../../core/errors.js';
import { can, canInOrg } from '../../core/policy.js';
import type { KcModule } from '../../core/module.js';
import { renderInvoicePdf, type CompanySettings, type InvoiceForPdf } from './pdf.js';

/** Kaufmännisches Runden (halb auf), wie in @kc/platform/pricing – hier lokal, weil Rechnungspositionen
 *  (Freitext, Dezimalmenge) sich nicht in das Produkt-Preisschema von calculatePrice pressen lassen. */
const divRound = (n: number, d: number): number => Math.floor((n * 2 + d) / (d * 2));
function lineAmounts(unitNetCents: number, quantity: number, taxBp: number) {
  const net = Math.round(unitNetCents * quantity);
  const tax = divRound(net * taxBp, 10000);
  return { net, tax, gross: net + tax };
}
async function nextInvoiceNumber(c: PoolConnection, prefix: string): Promise<string> {
  await run("UPDATE number_sequences SET next_value = LAST_INSERT_ID(next_value + 1) WHERE name = 'invoice'", [], c);
  return `${prefix}-${(await one('SELECT LAST_INSERT_ID() AS n', [], c))!.n}`;
}
async function settings(): Promise<CompanySettings> {
  const s = await one('SELECT * FROM company_settings WHERE id = 1');
  return {
    name: s?.name ?? null, street: s?.street ?? null, zip: s?.zip ?? null, city: s?.city ?? null, country: s?.country ?? 'DE',
    taxNumber: s?.tax_number ?? null, vatId: s?.vat_id ?? null, bankName: s?.bank_name ?? null, iban: s?.iban ?? null, bic: s?.bic ?? null,
    invoicePrefix: s?.invoice_prefix ?? 'RE', defaultDueDays: Number(s?.default_due_days ?? 14),
    paymentMethods: (typeof s?.payment_methods === 'string' ? JSON.parse(s.payment_methods) : s?.payment_methods) ?? ['Überweisung'],
    footerText: s?.footer_text ?? null,
  };
}
const complete = (s: CompanySettings) => !!(s.name && s.street && s.zip && s.city && (s.taxNumber || s.vatId));

const itemView = (i: any) => ({ id: i.id, contractId: i.contract_id, description: i.description, quantity: Number(i.quantity), unitPriceNetCents: i.unit_price_net_cents, taxBp: i.tax_bp, netCents: i.net_cents, taxCents: i.tax_cents, grossCents: i.gross_cents });
const invoiceView = (v: any) => ({
  id: v.id, number: v.number, orgId: v.org_id, orgName: v.org_name, customerNumber: v.customer_number, status: v.status,
  issueDate: v.issue_date, dueDate: v.due_date, overdue: v.status === 'open' && v.due_date && new Date(v.due_date) < new Date(),
  currency: v.currency, totalNetCents: v.total_net_cents, totalTaxCents: v.total_tax_cents, totalGrossCents: v.total_gross_cents,
  paymentMethod: v.payment_method, note: v.note, paidAt: v.paid_at, cancelsInvoiceId: v.cancels_invoice_id, cancelledByInvoiceId: v.cancelled_by_invoice_id,
  createdAt: v.created_at, issuedAt: v.issued_at, cancelledAt: v.cancelled_at,
});
const INVOICE_SQL = 'SELECT v.*, g.name AS org_name, g.customer_number FROM invoices v JOIN organizations g ON g.id = v.org_id';

async function loadInvoice(id: string) {
  const v = await one(`${INVOICE_SQL} WHERE v.id = ?`, [id]);
  if (!v) return null;
  const items = await query('SELECT * FROM invoice_items WHERE invoice_id = ? ORDER BY sort_order', [id]);
  return { v, items };
}
const notify = (event: string, extra: Record<string, unknown>, key: string, correlationId: string) => enqueue('discord.notify', { event, ...extra }, { idempotencyKey: key, correlationId });

export const invoicesModule: KcModule = {
  name: 'invoices',
  permissions: {
    staff: { support: ['invoices.read'], accounting: ['invoices.read', 'invoices.write'], admin: ['invoices.read', 'invoices.write'], superadmin: ['invoices.read', 'invoices.write', 'settings.write'] },
    org: { owner: ['invoices.read'], admin: ['invoices.read'], member: ['invoices.read'] },
  },
  register(app: FastifyInstance) {
    // ---- Firmenstammdaten (für den Rechnungskopf) ---------------------------
    app.get('/admin/company-settings', async (req) => { requirePermission(req, 'invoices.read'); const s = await settings(); return { ...s, complete: complete(s) }; });
    app.put('/admin/company-settings', async (req) => {
      const a = requirePermission(req, 'settings.write');
      const b = z.object({
        name: z.string().trim().max(200).optional(), street: z.string().trim().max(200).optional(), zip: z.string().trim().max(20).optional(), city: z.string().trim().max(100).optional(), country: z.string().length(2).optional(),
        taxNumber: z.string().trim().max(50).optional(), vatId: z.string().trim().max(30).optional(), bankName: z.string().trim().max(150).optional(), iban: z.string().trim().max(34).optional(), bic: z.string().trim().max(11).optional(),
        invoicePrefix: z.string().trim().regex(/^[A-Za-z0-9]{1,10}$/).optional(), defaultDueDays: z.number().int().min(0).max(180).optional(),
        paymentMethods: z.array(z.string().trim().min(1).max(50)).min(1).max(10).optional(), footerText: z.string().trim().max(500).nullable().optional(),
      }).parse(req.body);
      const cols: Record<string, string> = { name: 'name', street: 'street', zip: 'zip', city: 'city', country: 'country', taxNumber: 'tax_number', vatId: 'vat_id', bankName: 'bank_name', iban: 'iban', bic: 'bic', invoicePrefix: 'invoice_prefix', defaultDueDays: 'default_due_days', footerText: 'footer_text' };
      const sets: string[] = []; const params: unknown[] = [];
      for (const [k, col] of Object.entries(cols)) if ((b as Record<string, unknown>)[k] !== undefined) { sets.push(`${col} = ?`); params.push((b as Record<string, unknown>)[k]); }
      if (b.paymentMethods) { sets.push('payment_methods = ?'); params.push(JSON.stringify(b.paymentMethods)); }
      if (sets.length) await run(`UPDATE company_settings SET ${sets.join(', ')} WHERE id = 1`, params);
      await audit({ actorType: 'user', actorId: a.user.id, action: 'company_settings.update', resourceType: 'company_settings', resourceId: '1', correlationId: req.correlationId, ip: clientIp(req), after: { ...b, iban: b.iban ? '***' : undefined } });
      return { ok: true };
    });

    // ---- Rechnungen: Entwurf, Positionen, Ausstellen, Bezahlt, Storno -------
    app.get('/invoices', async (req) => {
      const a = requireAuth(req);
      const q = z.object({ org: z.string().uuid().optional(), status: z.enum(['draft', 'open', 'paid', 'cancelled']).optional() }).parse(req.query);
      const staff = can(a.principal, 'invoices.read');
      const myOrgs = a.principal.memberships.map((m) => m.orgId);
      if (!staff && myOrgs.length === 0) return [];
      if (staff && q.org && !(await one('SELECT 1 AS x FROM organizations WHERE id = ?', [q.org]))) throw notFound();
      const orgs = staff ? (q.org ? [q.org] : null) : myOrgs;
      const orgPlaceholders = orgs ? orgs.map(() => '?').join(',') : '';
      const rows = await query(
        `${INVOICE_SQL} WHERE (${orgs ? `v.org_id IN (${orgPlaceholders})` : '1=1'}) AND (? IS NULL OR v.status = ?)${staff ? '' : " AND v.status != 'draft'"} ORDER BY v.created_at DESC LIMIT 200`,
        [...(orgs ?? []), q.status ?? null, q.status ?? null]);
      return rows.map(invoiceView);
    });

    app.post('/invoices', async (req) => {
      const a = requirePermission(req, 'invoices.write');
      const b = z.object({ orgId: z.string().uuid(), note: z.string().trim().max(500).optional(), paymentMethod: z.string().max(50).optional() }).parse(req.body);
      if (!(await one('SELECT 1 AS x FROM organizations WHERE id = ?', [b.orgId]))) throw notFound();
      const id = randomUUID();
      await run('INSERT INTO invoices (id, org_id, note, payment_method, created_by) VALUES (?,?,?,?,?)', [id, b.orgId, b.note ?? null, b.paymentMethod ?? null, a.user.id]);
      await audit({ actorType: 'user', actorId: a.user.id, orgId: b.orgId, action: 'invoice.create', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req) });
      return { id };
    });

    app.get('/invoices/:id', async (req) => {
      const a = requireAuth(req); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const staff = can(a.principal, 'invoices.read');
      const res = await loadInvoice(id);
      if (!res || !canInOrg(a.principal, res.v.org_id, 'invoices.read', 'invoices.read') || (!staff && res.v.status === 'draft')) throw notFound();
      return { ...invoiceView(res.v), items: res.items.map(itemView), canWrite: staff };
    });

    /** Ersetzt die Positionen eines Entwurfs vollständig (einfacher als Einzel-CRUD, ausreichend für eine Entwurfsphase). */
    app.put('/invoices/:id/items', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const b = z.object({ items: z.array(z.object({
        description: z.string().trim().min(1).max(300), quantity: z.number().positive().max(100000), unitPriceNetCents: z.number().int().min(0).max(100_000_00), taxBp: z.number().int().min(0).max(3000), contractId: z.string().uuid().optional(),
      })).min(1).max(100) }).parse(req.body);
      const v = await one('SELECT * FROM invoices WHERE id = ?', [id]); if (!v) throw notFound();
      if (v.status !== 'draft') throw conflict('Nur Entwürfe können bearbeitet werden. Ausgestellte Rechnungen sind unveränderlich (nur Storno möglich).', 'INVOICE_NOT_DRAFT');
      let net = 0, tax = 0, gross = 0;
      await tx(async (c) => {
        await run('DELETE FROM invoice_items WHERE invoice_id = ?', [id], c);
        for (const [idx, it] of b.items.entries()) {
          const a2 = lineAmounts(it.unitPriceNetCents, it.quantity, it.taxBp); net += a2.net; tax += a2.tax; gross += a2.gross;
          await run('INSERT INTO invoice_items (id, invoice_id, contract_id, description, quantity, unit_price_net_cents, tax_bp, net_cents, tax_cents, gross_cents, sort_order) VALUES (?,?,?,?,?,?,?,?,?,?,?)',
            [randomUUID(), id, it.contractId ?? null, it.description, it.quantity, it.unitPriceNetCents, it.taxBp, a2.net, a2.tax, a2.gross, idx], c);
        }
        await run('UPDATE invoices SET total_net_cents = ?, total_tax_cents = ?, total_gross_cents = ? WHERE id = ?', [net, tax, gross, id], c);
      });
      await audit({ actorType: 'user', actorId: a.user.id, orgId: v.org_id, action: 'invoice.items.update', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req), after: { items: b.items.length, totalGrossCents: gross } });
      return { ok: true };
    });

    /** Aus einem Vertrag die letzte Preisangabe als Positionsvorschlag übernehmen (nichts wird automatisch gespeichert). */
    /** Vorschlag für eine Rechnungsposition aus dem eingefrorenen Preis-Snapshot eines Vertrags (die laufende Periode). */
    app.get('/invoices/suggest-from-contract/:contractId', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { contractId } = z.object({ contractId: z.string().uuid() }).parse(req.params);
      const c = await one('SELECT * FROM contracts WHERE id = ?', [contractId]); if (!c) throw notFound();
      const snap = typeof c.price_snapshot_json === 'string' ? JSON.parse(c.price_snapshot_json) : c.price_snapshot_json;
      return { orgId: c.org_id, items: [{ description: snap.name, quantity: 1, unitPriceNetCents: snap.recurring?.net ?? 0, taxBp: snap.taxBp ?? 1900, contractId }] };
    });
    /** Vorschlag aus dem aktuellen Katalogpreis eines Produkts (Einrichtung und/oder wiederkehrender Preis als eigene Positionen). */
    app.get('/invoices/suggest-from-product/:productId', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { productId } = z.object({ productId: z.string().uuid() }).parse(req.params);
      const p = await one('SELECT p.*, v.name, v.tax_bp, v.price_basis, v.setup_cents, v.recurring_cents, v.billing_interval FROM products p JOIN product_versions v ON v.id = p.current_version_id WHERE p.id = ?', [productId]);
      if (!p) throw notFound();
      const price = calculatePrice({ basis: p.price_basis, setupCents: p.setup_cents, recurringCents: p.recurring_cents, taxBp: p.tax_bp, interval: p.billing_interval, quantity: 1, discountBp: 0 });
      const items = [];
      if (price.setup.net > 0) items.push({ description: `Einrichtung: ${p.name}`, quantity: 1, unitPriceNetCents: price.setup.net, taxBp: p.tax_bp });
      if (price.recurring.net > 0) items.push({ description: p.name, quantity: 1, unitPriceNetCents: price.recurring.net, taxBp: p.tax_bp });
      if (items.length === 0) items.push({ description: p.name, quantity: 1, unitPriceNetCents: 0, taxBp: p.tax_bp });
      return { items };
    });

    app.post('/invoices/:id/issue', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const b = z.object({ dueDate: z.string().date().optional() }).parse(req.body ?? {});
      const v = await one('SELECT * FROM invoices WHERE id = ?', [id]); if (!v) throw notFound();
      if (v.status !== 'draft') throw conflict('Die Rechnung wurde bereits ausgestellt.', 'INVOICE_NOT_DRAFT');
      const items = await query('SELECT 1 AS x FROM invoice_items WHERE invoice_id = ?', [id]);
      if (items.length === 0) throw badRequest('Eine Rechnung ohne Positionen kann nicht ausgestellt werden.', 'NO_ITEMS');
      const s = await settings(); if (!complete(s)) throw badRequest('Die Firmenstammdaten sind unvollständig (Name, Anschrift, Steuernummer/USt-IdNr.). Bitte unter Einstellungen ergänzen, bevor Rechnungen ausgestellt werden.', 'COMPANY_SETTINGS_INCOMPLETE');
      const due = b.dueDate ?? new Date(Date.now() + s.defaultDueDays * 86400000).toISOString().slice(0, 10);
      const number = await tx(async (c) => {
        const n = await nextInvoiceNumber(c, s.invoicePrefix);
        await run("UPDATE invoices SET number = ?, status = 'open', issue_date = CURDATE(), due_date = ?, issued_at = UTC_TIMESTAMP(3) WHERE id = ?", [n, due, id], c);
        return n;
      });
      await audit({ actorType: 'user', actorId: a.user.id, orgId: v.org_id, action: 'invoice.issue', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req), after: { number } });
      await notify('invoice.issued', { number, gross: v.total_gross_cents }, `invoice.issued:${id}`, req.correlationId);
      return { ok: true, number };
    });

    app.post('/invoices/:id/mark-paid', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const v = await one('SELECT * FROM invoices WHERE id = ?', [id]); if (!v) throw notFound();
      if (v.status !== 'open') throw conflict('Nur ausgestellte, noch offene Rechnungen können als bezahlt markiert werden.', 'INVOICE_NOT_OPEN');
      await run("UPDATE invoices SET status = 'paid', paid_at = UTC_TIMESTAMP(3) WHERE id = ?", [id]);
      await audit({ actorType: 'user', actorId: a.user.id, orgId: v.org_id, action: 'invoice.paid', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req) });
      return { ok: true };
    });

    /** Storno: erzeugt eine neue, ausgestellte Rechnung mit umgekehrten Vorzeichen und verweist auf das Original.
     *  Die ursprüngliche Rechnung wird NIE gelöscht oder verändert (gesetzliche Vorgabe). */
    app.post('/invoices/:id/cancel', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const b = z.object({ reason: z.string().trim().max(300).optional() }).parse(req.body ?? {});
      const res = await loadInvoice(id); if (!res) throw notFound(); const v = res.v;
      if (v.status !== 'open') throw conflict('Nur offene Rechnungen können storniert werden. Eine bezahlte Rechnung erst als Storno mit Rückzahlungsvermerk erfassen.', 'INVOICE_NOT_OPEN');
      const s = await settings();
      const creditId = randomUUID();
      const number = await tx(async (c) => {
        const n = await nextInvoiceNumber(c, s.invoicePrefix);
        await run('INSERT INTO invoices (id, number, org_id, status, issue_date, due_date, total_net_cents, total_tax_cents, total_gross_cents, note, cancels_invoice_id, created_by, issued_at) VALUES (?,?,?,\'open\',CURDATE(),CURDATE(),?,?,?,?,?,?,UTC_TIMESTAMP(3))',
          [creditId, n, v.org_id, -v.total_net_cents, -v.total_tax_cents, -v.total_gross_cents, b.reason ? `Storno zu ${v.number}: ${b.reason}` : `Storno zu ${v.number}`, id, a.user.id], c);
        for (const it of res.items) await run('INSERT INTO invoice_items (id, invoice_id, contract_id, description, quantity, unit_price_net_cents, tax_bp, net_cents, tax_cents, gross_cents, sort_order) VALUES (?,?,?,?,?,?,?,?,?,?,?)',
          [randomUUID(), creditId, it.contract_id, it.description, -Number(it.quantity), it.unit_price_net_cents, it.tax_bp, -it.net_cents, -it.tax_cents, -it.gross_cents, it.sort_order], c);
        await run("UPDATE invoices SET status = 'cancelled', cancelled_at = UTC_TIMESTAMP(3), cancelled_by_invoice_id = ? WHERE id = ?", [creditId, id], c);
        return n;
      });
      await audit({ actorType: 'user', actorId: a.user.id, orgId: v.org_id, action: 'invoice.cancel', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req), after: { creditNumber: number } });
      return { ok: true, creditInvoiceId: creditId, creditNumber: number };
    });

    app.delete('/invoices/:id', async (req) => {
      const a = requirePermission(req, 'invoices.write'); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const v = await one('SELECT * FROM invoices WHERE id = ?', [id]); if (!v) throw notFound();
      if (v.status !== 'draft') throw forbidden('Ausgestellte Rechnungen können nicht gelöscht werden, nur storniert.', 'INVOICE_NOT_DRAFT');
      await run('DELETE FROM invoice_items WHERE invoice_id = ?', [id]); await run('DELETE FROM invoices WHERE id = ?', [id]);
      await audit({ actorType: 'user', actorId: a.user.id, orgId: v.org_id, action: 'invoice.delete_draft', resourceType: 'invoice', resourceId: id, correlationId: req.correlationId, ip: clientIp(req) });
      return { ok: true };
    });

    app.get('/invoices/:id/pdf', async (req, reply) => {
      const a = requireAuth(req); const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
      const staff = can(a.principal, 'invoices.read');
      const res = await loadInvoice(id);
      if (!res || !canInOrg(a.principal, res.v.org_id, 'invoices.read', 'invoices.read') || (!staff && res.v.status === 'draft')) throw notFound();
      if (res.v.status === 'draft') throw badRequest('Für Entwürfe gibt es noch kein PDF. Bitte zuerst ausstellen.', 'INVOICE_DRAFT');
      const org = await one('SELECT o.name, b.company, b.street, b.zip, b.city, b.country, b.vat_id FROM organizations o LEFT JOIN billing_profiles b ON b.org_id = o.id WHERE o.id = ?', [res.v.org_id]);
      const s = await settings();
      const inv: InvoiceForPdf = {
        number: res.v.number, issueDate: res.v.issue_date, dueDate: res.v.due_date, status: res.v.status, paymentMethod: res.v.payment_method, note: res.v.note,
        totalNetCents: res.v.total_net_cents, totalTaxCents: res.v.total_tax_cents, totalGrossCents: res.v.total_gross_cents,
        customer: { name: org!.company || org!.name, street: org!.street, zip: org!.zip, city: org!.city, country: org!.country ?? 'DE', vatId: org!.vat_id ?? null },
        items: res.items.map((i) => ({ description: i.description, quantity: Number(i.quantity), unitPriceNetCents: i.unit_price_net_cents, taxBp: i.tax_bp, netCents: i.net_cents, taxCents: i.tax_cents, grossCents: i.gross_cents })),
      };
      reply.header('content-type', 'application/pdf').header('content-disposition', `inline; filename="${res.v.number}.pdf"`);
      return reply.send(renderInvoicePdf(inv, s));
    });
  },
};