import React from "react";
import { Document, Page, View, Text, StyleSheet, renderToBuffer } from "@react-pdf/renderer";
import { formatDate } from "./format";

// Generated synchronously in the checkout request (see app/lib/orderEmail.ts)
// and attached to the order-confirmation email, plus available on-demand via
// app/api/account/orders/[orderNumber]/invoice/route.ts — same render
// function both times, so a re-download always matches what was emailed.
//
// Built-in Helvetica, not a registered web font — this renders inside the
// checkout request's own fire-and-forget email step; a font-fetch failure
// there is one more way to lose the invoice attachment for no real design
// benefit. Same choice as the Payload-side correction-invoice PDF
// (src/lib/correctionInvoicePdf.tsx in the backend repo, kept visually in
// sync with this file by eye — not shared code, two separate deployments).
const BRAND = "#f6a701";
const TEXT_MUTED = "#6b6b69";
const BORDER = "#e5e0d8";
const BG_MUTED = "#f8f5f1";
const SUCCESS = "#2f8f4e";
const SUCCESS_TINT = "#e7f5eb";

const styles = StyleSheet.create({
  page: { padding: 0, fontSize: 10, fontFamily: "Helvetica", color: "#1a1a18" },
  // A rule, not a filled band — a bold brand-colored line with a thin
  // muted second line underneath, rather than a plain 1pt gray divider.
  headerBand: {
    padding: 32,
    paddingBottom: 24,
    flexDirection: "row",
    justifyContent: "space-between",
    alignItems: "center",
    borderBottomWidth: 3,
    borderBottomColor: BRAND,
  },
  headerRuleThin: { height: 1, backgroundColor: BORDER, marginHorizontal: 32 },
  wordmark: { fontFamily: "Helvetica-Bold", fontSize: 14 },
  kindLabel: { fontFamily: "Helvetica-Bold", fontSize: 22, color: BRAND, letterSpacing: 1 },
  body: { padding: 32, paddingBottom: 90 },
  addressRow: { flexDirection: "row", justifyContent: "space-between", marginBottom: 24 },
  addressBlock: { width: "45%" },
  addressLabel: { fontSize: 8, color: TEXT_MUTED, marginBottom: 4, textTransform: "uppercase" },
  addressLine: { fontSize: 10, lineHeight: 1.5 },
  metaRow: { flexDirection: "row", gap: 10, marginBottom: 16, flexWrap: "wrap" },
  metaBox: { borderWidth: 1, borderColor: BORDER, borderRadius: 6, paddingVertical: 8, paddingHorizontal: 12 },
  metaLabel: { fontSize: 7, color: TEXT_MUTED, textTransform: "uppercase", marginBottom: 2 },
  metaValue: { fontSize: 10, fontFamily: "Helvetica-Bold" },
  paidBadge: { backgroundColor: SUCCESS_TINT, borderRadius: 6, paddingVertical: 8, paddingHorizontal: 12, justifyContent: "center" },
  paidBadgeText: { fontSize: 10, fontFamily: "Helvetica-Bold", color: SUCCESS },
  table: { borderRadius: 6, overflow: "hidden", borderWidth: 1, borderColor: BORDER, marginTop: 8, marginBottom: 16 },
  tableHeader: { flexDirection: "row", backgroundColor: BG_MUTED, paddingVertical: 8, paddingHorizontal: 10 },
  tableRow: { flexDirection: "row", paddingVertical: 8, paddingHorizontal: 10, borderTopWidth: 1, borderTopColor: BORDER },
  tableRowAlt: { backgroundColor: BG_MUTED },
  colName: { flex: 3 },
  colQty: { flex: 1, textAlign: "right" },
  colPrice: { flex: 1, textAlign: "right" },
  colTotal: { flex: 1, textAlign: "right" },
  headerCell: { fontSize: 8, color: TEXT_MUTED, textTransform: "uppercase" },
  bundleLine: { fontSize: 8, color: TEXT_MUTED, marginTop: 2 },
  summary: { alignItems: "flex-end", marginBottom: 24 },
  summaryBox: { width: 240, backgroundColor: BG_MUTED, borderRadius: 6, padding: 14 },
  summaryRow: { flexDirection: "row", justifyContent: "space-between", paddingVertical: 2 },
  summaryLabel: { fontSize: 10, color: TEXT_MUTED },
  summaryValue: { fontSize: 10 },
  grandTotalRow: { flexDirection: "row", justifyContent: "space-between", paddingTop: 8, marginTop: 6, borderTopWidth: 1, borderTopColor: BORDER },
  grandTotalLabel: { fontSize: 12, fontFamily: "Helvetica-Bold" },
  grandTotalValue: { fontSize: 12, fontFamily: "Helvetica-Bold" },
  // `fixed` (below, on the element) + absolute positioning — always pinned
  // to the bottom of the page regardless of how much content is above it,
  // rather than just following wherever the content flow happens to end.
  footer: {
    position: "absolute",
    bottom: 32,
    left: 32,
    right: 32,
    borderTopWidth: 1,
    borderTopColor: BORDER,
    paddingTop: 12,
    fontSize: 8,
    color: TEXT_MUTED,
  },
});

function formatPrice(amount: number): string {
  return new Intl.NumberFormat("de-DE", { style: "currency", currency: "EUR" }).format(amount);
}

export type InvoiceItem = { productName: string; quantity: number; unitPrice: number; taxRatePercent: number; bundleContents?: string | null };

export type InvoiceOrder = {
  orderNumber: string;
  invoiceNumber: string;
  invoiceIssuedAt: string;
  customerFirstName: string;
  customerLastName: string;
  deliveryMethod: "address" | "packstation";
  street?: string | null;
  packstationNumber?: string | null;
  postNumber?: string | null;
  zip: string;
  city: string;
  country: string;
  paymentMethodTitle: string;
  items: InvoiceItem[];
  subtotal: number;
  shippingCost: number;
  discountAmount: number;
  discountCode: string | null;
  total: number;
};

export type InvoiceSeller = {
  sellerName: string;
  sellerStreet: string;
  sellerZip: string;
  sellerCity: string;
  sellerCountry: string;
  sellerEmail: string;
  vatId: string;
  taxRatePercent: number;
  bankDetails?: string | null;
};

// Used only by /company-settings-preview's Live Preview — a fixed sample
// order so the admin sees a realistic-looking invoice while editing
// company-settings fields, without depending on any real order existing.
export const SAMPLE_INVOICE_ORDER: InvoiceOrder = {
  orderNumber: "#EP-0001-A7K2",
  invoiceNumber: "RE-0001",
  invoiceIssuedAt: new Date().toISOString(),
  customerFirstName: "Max",
  customerLastName: "Mustermann",
  deliveryMethod: "address",
  street: "Musterweg 5",
  zip: "10115",
  city: "Berlin",
  country: "Deutschland",
  paymentMethodTitle: "Kreditkarte",
  items: [
    { productName: "ToDo-Karten – Set", quantity: 1, unitPrice: 12.9, taxRatePercent: 19, bundleContents: null },
    { productName: "Wochenplaner – Überblick", quantity: 2, unitPrice: 14.9, taxRatePercent: 19, bundleContents: null },
  ],
  subtotal: 42.7,
  shippingCost: 0,
  discountAmount: 5,
  discountCode: "WILLKOMMEN10",
  total: 37.7,
};

// "Überweisung" (bank transfer) is the only payment method on this shop
// that ISN'T settled immediately — Kreditkarte/PayPal both capture at
// checkout. Rather than hardcode a list of "immediate" method titles
// (fragile the moment a new one is added in Payload's payment-methods
// collection), the only method that's ever NOT immediate is named
// explicitly — everything else defaults to "paid already".
function isPaidImmediately(paymentMethodTitle: string): boolean {
  return paymentMethodTitle !== "Überweisung";
}

// Distributes the order-level discount/shipping proportionally across each
// item's gross line total before computing that line's net/tax — so the
// per-rate summary still reconciles exactly to `order.total` even when a
// discount or shipping cost is present alongside items taxed at different
// rates. Falls back to the seller's default rate for any line that
// predates this field (older orders had no per-item snapshot).
function groupByTaxRate(order: InvoiceOrder, defaultRate: number): { rate: number; net: number; tax: number; gross: number }[] {
  const groups = new Map<number, number>();
  for (const item of order.items) {
    const rate = item.taxRatePercent ?? defaultRate;
    const lineGross = item.quantity * item.unitPrice;
    groups.set(rate, (groups.get(rate) ?? 0) + lineGross);
  }
  const scale = order.subtotal > 0 ? (order.subtotal - order.discountAmount + order.shippingCost) / order.subtotal : 1;
  return Array.from(groups.entries())
    .map(([rate, lineGross]) => {
      const gross = lineGross * scale;
      const net = gross / (1 + rate / 100);
      return { rate, net, tax: gross - net, gross };
    })
    .sort((a, b) => b.rate - a.rate);
}

// Exported (not just used internally by renderInvoicePdf below) so
// /company-settings-preview's client component can mount it directly with
// @react-pdf/renderer's browser-side <PDFViewer> — a live, in-browser
// rendered PDF that re-renders as the admin edits company-settings fields
// via Payload's postMessage-based useLivePreview(), no server round-trip
// needed for each keystroke the way an HTML preview would.
export function InvoiceDocument({ order, seller }: { order: InvoiceOrder; seller: InvoiceSeller }) {
  const rateGroups = groupByTaxRate(order, seller.taxRatePercent);
  const paid = isPaidImmediately(order.paymentMethodTitle);
  const deliveryLine =
    order.deliveryMethod === "address" ? order.street : `Packstation ${order.packstationNumber} · Postnummer ${order.postNumber}`;

  return (
    <Document>
      <Page size="A4" style={styles.page}>
        <View style={styles.headerBand}>
          <Text style={styles.wordmark}>einfach produktiv.</Text>
          <Text style={styles.kindLabel}>RECHNUNG</Text>
        </View>

        <View style={styles.body}>
          <View style={styles.addressRow}>
            <View style={styles.addressBlock}>
              <Text style={styles.addressLabel}>Von</Text>
              <Text style={styles.addressLine}>{seller.sellerName}</Text>
              <Text style={styles.addressLine}>{seller.sellerStreet}</Text>
              <Text style={styles.addressLine}>
                {seller.sellerZip} {seller.sellerCity}
              </Text>
              <Text style={styles.addressLine}>{seller.sellerCountry}</Text>
            </View>
            <View style={styles.addressBlock}>
              <Text style={styles.addressLabel}>An</Text>
              <Text style={styles.addressLine}>
                {order.customerFirstName} {order.customerLastName}
              </Text>
              <Text style={styles.addressLine}>{deliveryLine}</Text>
              <Text style={styles.addressLine}>
                {order.zip} {order.city}
              </Text>
              <Text style={styles.addressLine}>{order.country}</Text>
            </View>
          </View>

          <View style={styles.metaRow}>
            <View style={styles.metaBox}>
              <Text style={styles.metaLabel}>Rechnungs-Nr.</Text>
              <Text style={styles.metaValue}>{order.invoiceNumber}</Text>
            </View>
            <View style={styles.metaBox}>
              <Text style={styles.metaLabel}>Datum</Text>
              <Text style={styles.metaValue}>{formatDate(order.invoiceIssuedAt)}</Text>
            </View>
            <View style={styles.metaBox}>
              <Text style={styles.metaLabel}>Bestellnummer</Text>
              <Text style={styles.metaValue}>{order.orderNumber}</Text>
            </View>
            <View style={styles.metaBox}>
              <Text style={styles.metaLabel}>USt-IdNr.</Text>
              <Text style={styles.metaValue}>{seller.vatId}</Text>
            </View>
            {paid && (
              <View style={styles.paidBadge}>
                <Text style={styles.paidBadgeText}>✓ Bereits beglichen ({order.paymentMethodTitle})</Text>
              </View>
            )}
          </View>

          <View style={styles.table}>
            <View style={styles.tableHeader}>
              <Text style={[styles.colName, styles.headerCell]}>Artikel</Text>
              <Text style={[styles.colQty, styles.headerCell]}>Menge</Text>
              <Text style={[styles.colPrice, styles.headerCell]}>Einzelpreis</Text>
              <Text style={[styles.colTotal, styles.headerCell]}>Betrag</Text>
            </View>
            {order.items.map((item, i) => (
              <View style={[styles.tableRow, i % 2 === 1 ? styles.tableRowAlt : {}]} key={i}>
                <View style={styles.colName}>
                  <Text>{item.productName}</Text>
                  {item.bundleContents ? <Text style={styles.bundleLine}>{item.bundleContents}</Text> : null}
                </View>
                <Text style={styles.colQty}>{item.quantity}</Text>
                <Text style={styles.colPrice}>{formatPrice(item.unitPrice)}</Text>
                <Text style={styles.colTotal}>{formatPrice(item.quantity * item.unitPrice)}</Text>
              </View>
            ))}
          </View>

          <View style={styles.summary}>
            <View style={styles.summaryBox}>
              {order.discountAmount > 0 && (
                <View style={styles.summaryRow}>
                  <Text style={styles.summaryLabel}>Rabatt{order.discountCode ? ` (${order.discountCode})` : ""}</Text>
                  <Text style={styles.summaryValue}>-{formatPrice(order.discountAmount)}</Text>
                </View>
              )}
              <View style={styles.summaryRow}>
                <Text style={styles.summaryLabel}>Versand</Text>
                <Text style={styles.summaryValue}>{order.shippingCost === 0 ? "Kostenlos" : formatPrice(order.shippingCost)}</Text>
              </View>
              {rateGroups.map((g) => (
                <React.Fragment key={g.rate}>
                  <View style={styles.summaryRow}>
                    <Text style={styles.summaryLabel}>Netto ({g.rate}%)</Text>
                    <Text style={styles.summaryValue}>{formatPrice(g.net)}</Text>
                  </View>
                  <View style={styles.summaryRow}>
                    <Text style={styles.summaryLabel}>zzgl. {g.rate}% MwSt.</Text>
                    <Text style={styles.summaryValue}>{formatPrice(g.tax)}</Text>
                  </View>
                </React.Fragment>
              ))}
              <View style={styles.grandTotalRow}>
                <Text style={styles.grandTotalLabel}>Gesamt</Text>
                <Text style={styles.grandTotalValue}>{formatPrice(order.total)}</Text>
              </View>
            </View>
          </View>

        </View>

        <View style={styles.footer} fixed>
          <Text>
            {seller.sellerName} · {seller.sellerStreet}, {seller.sellerZip} {seller.sellerCity} · {seller.sellerEmail} · USt-IdNr.{" "}
            {seller.vatId}
          </Text>
          {seller.bankDetails ? <Text style={{ marginTop: 4 }}>Bankverbindung (für Überweisung): {seller.bankDetails}</Text> : null}
        </View>
      </Page>
    </Document>
  );
}

export async function renderInvoicePdf(order: InvoiceOrder, seller: InvoiceSeller): Promise<Buffer> {
  return renderToBuffer(<InvoiceDocument order={order} seller={seller} />);
}

// Exported for unit testing (see app/lib/__tests__/invoicePdf.test.ts) —
// the actual money math and payment-status logic, independent of PDF
// rendering.
export const __testables = { isPaidImmediately, groupByTaxRate };
