static/main.js

const VAT_OPTIONS = [
  { value: "23", label: "23%" },
  { value: "8", label: "8%" },
  { value: "5", label: "5%" },
  { value: "0", label: "0% (ZW)" },
  { value: "ZW", label: "ZW - zwolnione" },
  { value: "NP", label: "NP - poza zakresem" },
];

const VAT_RATE_VALUES = {
  "23": 0.23,
  "8": 0.08,
  "5": 0.05,
  "0": 0,
  ZW: 0,
  NP: 0,
};

const setupSection = document.getElementById("setup-section");
const loginSection = document.getElementById("login-section");
const appSection = document.getElementById("app-section");

const setupForm = document.getElementById("setup-form");
const loginForm = document.getElementById("login-form");
const invoiceForm = document.getElementById("invoice-form");
const businessForm = document.getElementById("business-form");

const setupFeedback = document.getElementById("setup-feedback");
const loginFeedback = document.getElementById("login-feedback");
const businessFeedback = document.getElementById("business-feedback");

const businessDisplay = document.getElementById("business-display");
const toggleBusinessFormButton = document.getElementById("toggle-business-form");
const cancelBusinessUpdateButton = document.getElementById("cancel-business-update");

const itemsBody = document.getElementById("items-body");
const addItemButton = document.getElementById("add-item-button");

const totalNetLabel = document.getElementById("total-net");
const totalVatLabel = document.getElementById("total-vat");
const totalGrossLabel = document.getElementById("total-gross");
const rateSummaryContainer = document.getElementById("rate-summary");

const exemptionNoteWrapper = document.getElementById("exemption-note-wrapper");
const exemptionNoteInput = document.getElementById("exemption-note");

const invoiceResult = document.getElementById("invoice-result");
const invoiceOutput = document.getElementById("invoice-output");
const downloadButton = document.getElementById("download-button");
const logoutButton = document.getElementById("logout-button");

let authToken = sessionStorage.getItem("invoiceAuthToken") || null;
let currentBusiness = null;
let lastInvoice = null;
let pdfFontPromise = null;
let pdfFontBase64 = null;

function setState(state) {
  setupSection.classList.add("hidden");
  loginSection.classList.add("hidden");
  appSection.classList.add("hidden");

  if (state === "setup") {
    setupSection.classList.remove("hidden");
  } else if (state === "login") {
    loginSection.classList.remove("hidden");
  } else if (state === "app") {
    appSection.classList.remove("hidden");
  }
}

function clearFeedback(element) {
  element.textContent = "";
  element.classList.remove("error", "success");
}

function showFeedback(element, message, type = "error") {
  element.textContent = message;
  element.classList.remove("error", "success");
  if (type) {
    element.classList.add(type);
  }
}

function parseNumber(value) {
  if (typeof value === "number") {
    return Number.isFinite(value) ? value : 0;
  }
  if (!value) {
    return 0;
  }
  const normalized = value.toString().replace(",", ".");
  const parsed = Number.parseFloat(normalized);
  return Number.isFinite(parsed) ? parsed : 0;
}

function formatCurrency(value) {
  const number = parseNumber(value);
  return `${number.toFixed(2)} PLN`;
}

function vatLabelFromCode(code) {
  if (code === "ZW" || code === "0") {
    return "ZW";
  }
  if (code === "NP") {
    return "NP";
  }
  return `${code}%`;
}

function requiresExemption(code) {
  return code === "ZW" || code === "0";
}

async function apiRequest(path, { method = "GET", body, headers = {} } = {}, requireAuth = false) {
  const options = {
    method,
    headers: {
      "Content-Type": "application/json",
      ...headers,
    },
  };

  if (body !== undefined) {
    options.body = JSON.stringify(body);
  }

  if (requireAuth) {
    if (!authToken) {
      throw new Error("Brak tokenu autoryzacyjnego.");
    }
    options.headers.Authorization = `Bearer ${authToken}`;
  }

  const response = await fetch(path, options);
  const isJson = response.headers.get("content-type")?.includes("application/json");
  const data = isJson ? await response.json() : {};

  if (response.status === 401) {
    authToken = null;
    sessionStorage.removeItem("invoiceAuthToken");
    setState("login");
    throw new Error(data.error || "Sesja wygasla. Zaloguj sie ponownie.");
  }

  if (!response.ok) {
    throw new Error(data.error || "Wystapil blad podczas komunikacji z serwerem.");
  }

  return data;
}

function renderBusinessDisplay(business) {
  if (!business) {
    businessDisplay.textContent = "Brak zapisanych danych firmy.";
    return;
  }

  businessDisplay.innerHTML = `
    <p><strong>${business.company_name}</strong></p>
    <p>${business.owner_name}</p>
    <p>${business.address_line}</p>
    <p>${business.postal_code} ${business.city}</p>
    <p>NIP: ${business.tax_id}</p>
    <p>Konto: ${business.bank_account}</p>
  `;
}

function fillBusinessForm(business) {
  if (!business) {
    return;
  }
  businessForm.elements.company_name.value = business.company_name || "";
  businessForm.elements.owner_name.value = business.owner_name || "";
  businessForm.elements.address_line.value = business.address_line || "";
  businessForm.elements.postal_code.value = business.postal_code || "";
  businessForm.elements.city.value = business.city || "";
  businessForm.elements.tax_id.value = business.tax_id || "";
  businessForm.elements.bank_account.value = business.bank_account || "";
}

function vatSelectElement(initialValue = "23") {
  const select = document.createElement("select");
  select.className = "item-vat";
  VAT_OPTIONS.forEach((option) => {
    const element = document.createElement("option");
    element.value = option.value;
    element.textContent = option.label;
    select.appendChild(element);
  });
  select.value = VAT_OPTIONS.some((option) => option.value === initialValue) ? initialValue : "23";
  return select;
}

function createItemRow(initialValues = {}) {
  const row = document.createElement("tr");

  const nameCell = document.createElement("td");
  const nameInput = document.createElement("input");
  nameInput.type = "text";
  nameInput.className = "item-name";
  nameInput.placeholder = "Nazwa towaru lub uslugi";
  if (initialValues.name) {
    nameInput.value = initialValues.name;
  }
  nameCell.appendChild(nameInput);

  const quantityCell = document.createElement("td");
  const quantityInput = document.createElement("input");
  quantityInput.type = "number";
  quantityInput.className = "item-quantity";
  quantityInput.min = "0.01";
  quantityInput.step = "0.01";
  quantityInput.value = initialValues.quantity ?? "1";
  quantityCell.appendChild(quantityInput);

  const unitGrossCell = document.createElement("td");
  const unitGrossInput = document.createElement("input");
  unitGrossInput.type = "number";
  unitGrossInput.className = "item-gross";
  unitGrossInput.min = "0.01";
  unitGrossInput.step = "0.01";
  unitGrossInput.placeholder = "Brutto";
  if (initialValues.unit_price_gross) {
    unitGrossInput.value = initialValues.unit_price_gross;
  }
  unitGrossCell.appendChild(unitGrossInput);

  const vatCell = document.createElement("td");
  const vatSelect = vatSelectElement(initialValues.vat_code);
  vatCell.appendChild(vatSelect);

  const totalCell = document.createElement("td");
  totalCell.className = "item-total";
  totalCell.textContent = "0.00 PLN";

  const actionsCell = document.createElement("td");
  const removeButton = document.createElement("button");
  removeButton.type = "button";
  removeButton.className = "remove-item";
  removeButton.textContent = "Usun";
  actionsCell.appendChild(removeButton);

  row.appendChild(nameCell);
  row.appendChild(quantityCell);
  row.appendChild(unitGrossCell);
  row.appendChild(vatCell);
  row.appendChild(totalCell);
  row.appendChild(actionsCell);

  const handleChange = () => updateTotals();
  nameInput.addEventListener("input", handleChange);
  quantityInput.addEventListener("input", handleChange);
  unitGrossInput.addEventListener("input", handleChange);
  vatSelect.addEventListener("change", handleChange);

  removeButton.addEventListener("click", () => {
    if (itemsBody.children.length === 1) {
      nameInput.value = "";
      quantityInput.value = "1";
      unitGrossInput.value = "";
      vatSelect.value = "23";
      updateTotals();
      return;
    }
    row.remove();
    updateTotals();
  });

  itemsBody.appendChild(row);
  updateTotals();
}

function calculateRowTotals(row) {
  const name = row.querySelector(".item-name")?.value.trim() ?? "";
  const quantity = parseNumber(row.querySelector(".item-quantity")?.value);
  const unitGross = parseNumber(row.querySelector(".item-gross")?.value);
  const vatCode = row.querySelector(".item-vat")?.value ?? "23";
  const rate = VAT_RATE_VALUES[vatCode] ?? 0;

  const hasValues = name || quantity > 0 || unitGross > 0;
  if (!hasValues) {
    return {
      valid: false,
      vatCode,
      vatLabel: vatLabelFromCode(vatCode),
      requiresExemption: requiresExemption(vatCode),
      quantity,
      unitGross,
      unitNet: 0,
      netTotal: 0,
      vatAmount: 0,
      grossTotal: 0,
    };
  }

  if (quantity <= 0 || unitGross <= 0) {
    return {
      valid: false,
      vatCode,
      vatLabel: vatLabelFromCode(vatCode),
      requiresExemption: requiresExemption(vatCode),
      quantity,
      unitGross,
      unitNet: 0,
      netTotal: 0,
      vatAmount: 0,
      grossTotal: quantity * unitGross,
    };
  }

  const grossTotal = quantity * unitGross;
  const netTotal = rate > 0 ? grossTotal / (1 + rate) : grossTotal;
  const vatAmount = grossTotal - netTotal;
  const unitNet = netTotal / quantity;

  return {
    valid: true,
    vatCode,
    vatLabel: vatLabelFromCode(vatCode),
    requiresExemption: requiresExemption(vatCode),
    quantity,
    unitGross,
    unitNet,
    netTotal,
    vatAmount,
    grossTotal,
  };
}

function updateTotals() {
  let totalNet = 0;
  let totalVat = 0;
  let totalGross = 0;
  const summary = new Map();
  let exemptionNeeded = false;

  const rows = Array.from(itemsBody.querySelectorAll("tr"));
  rows.forEach((row) => {
    const totals = calculateRowTotals(row);
    if (totals.requiresExemption) {
      exemptionNeeded = true;
    }
    const totalCell = row.querySelector(".item-total");
    totalCell.textContent = formatCurrency(totals.grossTotal);

    if (!totals.valid) {
      return;
    }

    totalNet += totals.netTotal;
    totalVat += totals.vatAmount;
    totalGross += totals.grossTotal;

    const existing = summary.get(totals.vatLabel) || { net: 0, vat: 0, gross: 0 };
    existing.net += totals.netTotal;
    existing.vat += totals.vatAmount;
    existing.gross += totals.grossTotal;
    summary.set(totals.vatLabel, existing);
  });

  totalNetLabel.textContent = `Suma netto: ${totalNet.toFixed(2)} PLN`;
  totalVatLabel.textContent = `Kwota VAT: ${totalVat.toFixed(2)} PLN`;
  totalGrossLabel.textContent = `Suma brutto: ${totalGross.toFixed(2)} PLN`;
  renderRateSummary(summary);

  if (exemptionNeeded) {
    exemptionNoteWrapper.classList.remove("hidden");
  } else {
    exemptionNoteWrapper.classList.add("hidden");
    exemptionNoteInput.value = "";
  }
}

function renderRateSummary(summary) {
  if (!summary || summary.size === 0) {
    rateSummaryContainer.innerHTML = "";
    return;
  }

  const entries = Array.from(summary.entries()).sort(([a], [b]) => a.localeCompare(b));
  const markup = entries
    .map(
      ([label, totals]) =>
        `<div class="rate-summary-item">
          <span>${label}</span>
          <span>Netto: ${totals.net.toFixed(2)} PLN</span>
          <span>VAT: ${totals.vat.toFixed(2)} PLN</span>
          <span>Brutto: ${totals.gross.toFixed(2)} PLN</span>
        </div>`
    )
    .join("");
  rateSummaryContainer.innerHTML = `<h4>Podsumowanie stawek</h4>${markup}`;
}

function collectInvoicePayload() {
  const items = [];
  const rows = Array.from(itemsBody.querySelectorAll("tr"));

  rows.forEach((row) => {
    const name = row.querySelector(".item-name")?.value.trim() ?? "";
    const quantity = parseNumber(row.querySelector(".item-quantity")?.value);
    const unitGross = parseNumber(row.querySelector(".item-gross")?.value);
    const vatCode = row.querySelector(".item-vat")?.value ?? "23";

    const hasValues = name || quantity > 0 || unitGross > 0;
    if (!hasValues) {
      return;
    }

    if (!name) {
      throw new Error("Kazda pozycja musi miec nazwe.");
    }
    if (quantity <= 0) {
      throw new Error("Ilosc musi byc wieksza od zera.");
    }
    if (unitGross <= 0) {
      throw new Error("Cena brutto musi byc wieksza od zera.");
    }

    items.push({
      name,
      quantity: quantity.toFixed(2),
      unit_price_gross: unitGross.toFixed(2),
      vat_code: vatCode,
    });
  });

  if (items.length === 0) {
    throw new Error("Dodaj przynajmniej jedna pozycje.");
  }

  const saleDate = invoiceForm.elements.saleDate.value || null;
  const exemptionNote = exemptionNoteInput.value.trim();
  const requiresExemptionNote = items.some((item) => item.vat_code === "ZW" || item.vat_code === "0");
  if (requiresExemptionNote && !exemptionNote) {
    throw new Error("Podaj podstawe prawna zwolnienia dla pozycji rozliczanych jako ZW.");
  }

  const client = {
    name: (invoiceForm.elements.clientName.value || "").trim(),
    tax_id: (invoiceForm.elements.clientTaxId.value || "").trim(),
    address_line: (invoiceForm.elements.clientAddress.value || "").trim(),
    postal_code: (invoiceForm.elements.clientPostalCode.value || "").trim(),
    city: (invoiceForm.elements.clientCity.value || "").trim(),
  };

  return {
    sale_date: saleDate,
    client,
    items,
    exemption_note: exemptionNote,
  };
}

function renderInvoicePreview(invoice) {
  if (!invoice || !currentBusiness) {
    invoiceOutput.innerHTML = "<p>Brak danych faktury.</p>";
    return;
  }

  const client = invoice.client || {};
  const hasClientData = client.name || client.address_line || client.postal_code || client.city || client.tax_id;

  const itemsRows = invoice.items
    .map(
      (item) => `
        <tr>
          <td>${item.name}</td>
          <td>${parseNumber(item.quantity).toFixed(2)}</td>
          <td>${formatCurrency(item.unit_price_net)}</td>
          <td>${formatCurrency(item.net_total)}</td>
          <td>${item.vat_label}</td>
          <td>${formatCurrency(item.vat_amount)}</td>
          <td>${formatCurrency(item.gross_total)}</td>
        </tr>`
    )
    .join("");

  const summaryRows = (invoice.summary || [])
    .map(
      (entry) =>
        `<div class="rate-summary-item">
          <span>${entry.vat_label}</span>
          <span>Netto: ${formatCurrency(entry.net_total)}</span>
          <span>VAT: ${formatCurrency(entry.vat_total)}</span>
          <span>Brutto: ${formatCurrency(entry.gross_total)}</span>
        </div>`
    )
    .join("");

  invoiceOutput.innerHTML = `
    <div class="invoice-preview-meta">
      <span><strong>Numer:</strong> ${invoice.invoice_id}</span>
      <span><strong>Data wystawienia:</strong> ${invoice.issued_at}</span>
      <span><strong>Data sprzedazy:</strong> ${invoice.sale_date}</span>
    </div>
    <div class="invoice-preview-header">
      <div class="invoice-preview-card">
        <h4>Nabywca</h4>
        ${
          hasClientData
            ? `
              <p>${client.name || "---"}</p>
              <p>${client.address_line || "---"}</p>
              <p>${client.postal_code || ""} ${client.city || ""}</p>
              <p>${client.tax_id ? `NIP: ${client.tax_id}` : ""}</p>
            `
            : "<p>Brak danych nabywcy.</p>"
        }
      </div>
      <div class="invoice-preview-card">
        <h4>Sprzedawca</h4>
        <p>${currentBusiness.company_name}</p>
        <p>${currentBusiness.owner_name}</p>
        <p>${currentBusiness.address_line}</p>
        <p>${currentBusiness.postal_code} ${currentBusiness.city}</p>
        <p>NIP: ${currentBusiness.tax_id}</p>
        <p>Konto: ${currentBusiness.bank_account}</p>
      </div>
    </div>
    <table>
      <thead>
        <tr>
          <th>Nazwa</th>
          <th>Ilość</th>
          <th>Cena jedn. netto</th>
          <th>Wartość netto (pozycja)</th>
          <th>Stawka VAT</th>
          <th>Kwota VAT (pozycja)</th>
          <th>Wartość brutto</th>
        </tr>
      </thead>
      <tbody>${itemsRows}</tbody>
    </table>
    <div class="rate-summary">
      <h4>Podsumowanie stawek</h4>
      ${summaryRows}
    </div>
    <div class="invoice-preview-summary">
      <span>Netto: ${formatCurrency(invoice.totals.net)}</span>
      <span>VAT: ${formatCurrency(invoice.totals.vat)}</span>
      <span>Brutto: ${formatCurrency(invoice.totals.gross)}</span>
    </div>
    ${
      invoice.exemption_note
        ? `<div class="invoice-preview-note"><strong>Podstawa prawna zwolnienia:</strong> ${invoice.exemption_note}</div>`
        : ""
    }
  `;
}

function drawPartyBox(doc, title, lines, x, y, width) {
  const lineHeight = 5;
  const wrappedLines = lines.flatMap((line) => doc.splitTextToSize(line, width));
  const boxHeight = wrappedLines.length * lineHeight + 14;

  doc.roundedRect(x - 4, y - 8, width + 8, boxHeight, 2, 2);
  doc.setFontSize(11);
  doc.text(title, x, y);
  doc.setFontSize(10);

  let cursor = y + 5;
  wrappedLines.forEach((line) => {
    doc.text(line, x, cursor);
    cursor += lineHeight;
  });

  return y - 8 + boxHeight;
}

function arrayBufferToBase64(buffer) {
  const bytes = new Uint8Array(buffer);
  const chunkSize = 0x8000;
  let binary = "";
  for (let offset = 0; offset < bytes.length; offset += chunkSize) {
    const chunk = bytes.subarray(offset, Math.min(offset + chunkSize, bytes.length));
    binary += String.fromCharCode.apply(null, chunk);
  }
  return btoa(binary);
}

const PDF_FONT_FILE = "Roboto-VariableFont_wdth,wght.ttf";
const PDF_FONT_NAME = "RobotoPolish";

async function ensurePdfFont() {
  if (pdfFontPromise) {
    return pdfFontPromise;
  }

  if (!window.jspdf || !window.jspdf.jsPDF) {
    throw new Error("Biblioteka jsPDF nie zostala zaladowana.");
  }

  const { jsPDF } = window.jspdf;
  const loadBase64 = async () => {
    if (typeof window !== "undefined" && window.PDF_FONT_BASE64) {
      return window.PDF_FONT_BASE64;
    }
    const response = await fetch(`/${encodeURIComponent(PDF_FONT_FILE)}`);
    if (!response.ok) {
      throw new Error(`Nie udalo sie pobrac czcionki Roboto (status ${response.status}).`);
    }
    const buffer = await response.arrayBuffer();
    return arrayBufferToBase64(buffer);
  };

  pdfFontPromise = loadBase64().then((data) => {
    pdfFontBase64 = data;
    return data;
  });

  return pdfFontPromise;
}

async function generatePdf(business, invoice) {
  if (!window.jspdf || !window.jspdf.jsPDF) {
    alert("Biblioteka jsPDF nie zostala zaladowana. Sprawdz polaczenie z internetem.");
    return;
  }

  let fontBase64;
  try {
    fontBase64 = await ensurePdfFont();
  } catch (error) {
    alert(error.message || "Nie udalo sie przygotowac czcionki do PDF.");
    return;
  }

  const { jsPDF } = window.jspdf;
  const doc = new jsPDF({ orientation: "portrait", unit: "mm", format: "a4" });
  const marginX = 18;
  let cursorY = 20;

  if (!doc.getFontList()[PDF_FONT_NAME]) {
    const embeddedFont = pdfFontBase64 || fontBase64;
    doc.addFileToVFS(PDF_FONT_FILE, embeddedFont);
    doc.addFont(PDF_FONT_FILE, PDF_FONT_NAME, "normal");
  }

  doc.setFont(PDF_FONT_NAME, "normal");
  doc.setFontSize(16);
  doc.text(`Faktura ${invoice.invoice_id}`, marginX, cursorY);
  doc.setFontSize(10);
  doc.text(`Data wystawienia: ${invoice.issued_at}`, marginX, cursorY + 6);
  doc.text(`Data sprzedaży: ${invoice.sale_date}`, marginX, cursorY + 12);

  cursorY += 22;
  const columnWidth = 85;
  const sellerX = marginX + columnWidth + 12;

  const clientLines = invoice.client && (invoice.client.name || invoice.client.address_line || invoice.client.city || invoice.client.tax_id)
    ? [
        invoice.client.name || "---",
        invoice.client.address_line || "",
        `${(invoice.client.postal_code || "").trim()} ${(invoice.client.city || "").trim()}`.trim(),
        invoice.client.tax_id ? `NIP: ${invoice.client.tax_id}` : "",
      ].filter((line) => line && line.trim())
    : ["Brak danych nabywcy"];

  const sellerLines = [
    business.company_name,
    business.owner_name,
    business.address_line,
    `${business.postal_code} ${business.city}`.trim(),
    `NIP: ${business.tax_id}`,
    `Konto: ${business.bank_account}`,
  ];

  const buyerBottom = drawPartyBox(doc, "NABYWCA", clientLines, marginX, cursorY, columnWidth);
  const sellerBottom = drawPartyBox(doc, "SPRZEDAWCA", sellerLines, sellerX, cursorY, columnWidth);
  cursorY = Math.max(buyerBottom, sellerBottom) + 12;

  const tableColumns = [
    { key: "name", label: "Nazwa", width: 52 },
    { key: "quantity", label: "Ilość", width: 16 },
    { key: "unitNet", label: "Cena jedn. netto", width: 24 },
    { key: "netTotal", label: "Wartość netto", width: 24 },
    { key: "vatLabel", label: "Stawka VAT", width: 15 },
    { key: "vatAmount", label: "Kwota VAT", width: 22 },
    { key: "grossTotal", label: "Wartość brutto", width: 21 },
  ];
  const tableWidth = tableColumns.reduce((sum, col) => sum + col.width, 0);
  const lineHeight = 5;
  const headerLineHeight = 4.2;
  tableColumns.forEach((column) => {
    column.headerLines = doc.splitTextToSize(column.label, column.width - 4);
  });
  const headerHeight = Math.max(...tableColumns.map((column) => column.headerLines.length * headerLineHeight + 3));

  doc.setFillColor(241, 243, 247);
  doc.rect(marginX, cursorY, tableWidth, headerHeight, "F");
  doc.rect(marginX, cursorY, tableWidth, headerHeight);
  let offsetX = marginX;
  doc.setFontSize(10);
  tableColumns.forEach((column) => {
    doc.rect(offsetX, cursorY, column.width, headerHeight);
    column.headerLines.forEach((line, index) => {
      const textY = cursorY + 4 + index * headerLineHeight;
      doc.text((line || "").trim(), offsetX + 2, textY);
    });
    offsetX += column.width;
  });
  cursorY += headerHeight;

  invoice.items.forEach((item) => {
    const quantity = parseNumber(item.quantity).toFixed(2);
    const unitNet = formatCurrency(item.unit_price_net);
    const netTotal = formatCurrency(item.net_total);
    const vatAmount = formatCurrency(item.vat_amount);
    const grossTotal = formatCurrency(item.gross_total);

    const wrapText = (text, width) =>
      doc
        .splitTextToSize(text ?? "", width)
        .map((line) => line.trim());

    const columnData = tableColumns.map((column) => {
      switch (column.key) {
        case "name":
          return wrapText(item.name, column.width - 4);
        case "quantity":
          return [quantity];
        case "unitNet":
          return [unitNet];
        case "netTotal":
          return [netTotal];
        case "vatLabel":
          return [item.vat_label];
        case "vatAmount":
          return [vatAmount];
        case "grossTotal":
          return [grossTotal];
        default:
          return [""];
      }
    });

    const rowHeight = Math.max(...columnData.map((data) => data.length)) * lineHeight + 2;
    offsetX = marginX;
    tableColumns.forEach((column, index) => {
      doc.rect(offsetX, cursorY, column.width, rowHeight);
      const lines = columnData[index];
      lines.forEach((line, lineIndex) => {
        const textY = cursorY + (lineIndex + 1) * lineHeight;
        const content = (line || "").trim();
        doc.text(content, offsetX + 2, textY);
      });
      offsetX += column.width;
    });

    cursorY += rowHeight;
  });

  cursorY += 10;
  doc.setFontSize(11);
  doc.text("Podsumowanie stawek:", marginX, cursorY);
  cursorY += 6;

  const summaryEntries = Array.isArray(invoice.summary) ? invoice.summary : [];
  summaryEntries.forEach((entry) => {
    const summaryLine = `${entry.vat_label} – Netto: ${formatCurrency(entry.net_total)} / VAT: ${formatCurrency(entry.vat_total)} / Brutto: ${formatCurrency(entry.gross_total)}`;
    const wrapped = doc.splitTextToSize(summaryLine, 170);
    wrapped.forEach((line) => {
      doc.text((line || "").trim(), marginX, cursorY);
      cursorY += lineHeight;
    });
  });

  cursorY += 6;
  doc.setFontSize(12);
  doc.text(`Suma netto: ${formatCurrency(invoice.totals.net)}`, marginX, cursorY);
  doc.text(`Suma VAT: ${formatCurrency(invoice.totals.vat)}`, marginX, cursorY + 6);
  doc.text(`Suma brutto: ${formatCurrency(invoice.totals.gross)}`, marginX, cursorY + 12);
  cursorY += 20;

  if (invoice.exemption_note) {
    doc.setFontSize(10);
    const noteLines = doc.splitTextToSize(`Podstawa prawna zwolnienia: ${invoice.exemption_note}`, 170);
    doc.text(noteLines, marginX, cursorY);
  }

  doc.save(`${invoice.invoice_id}.pdf`);
}

async function loadBusinessData() {
  const data = await apiRequest("/api/business", {}, true);
  currentBusiness = data.business;
  renderBusinessDisplay(currentBusiness);
  fillBusinessForm(currentBusiness);
}

function resetInvoiceForm() {
  invoiceForm.reset();
  exemptionNoteInput.value = "";
  exemptionNoteWrapper.classList.add("hidden");
  itemsBody.innerHTML = "";
  createItemRow();
  const today = new Date().toISOString().slice(0, 10);
  invoiceForm.elements.saleDate.value = today;
}

async function bootstrapApp() {
  try {
    await loadBusinessData();
    setState("app");
  } catch (error) {
    console.error(error);
    authToken = null;
    sessionStorage.removeItem("invoiceAuthToken");
    showFeedback(loginFeedback, error.message || "Nie udalo sie pobrac danych firmy.");
    setState("login");
  }
}

async function initialize() {
  resetInvoiceForm();
  try {
    const status = await apiRequest("/api/status");
    if (!status.configured) {
      setState("setup");
      return;
    }

    if (authToken) {
      await bootstrapApp();
    } else {
      setState("login");
    }
  } catch (error) {
    console.error(error);
    setState("setup");
    showFeedback(setupFeedback, "Nie udalo sie nawiazac polaczenia z serwerem.");
  }
}

setupForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  clearFeedback(setupFeedback);

  const formData = new FormData(setupForm);
  const password = formData.get("password")?.toString() ?? "";
  const confirmPassword = formData.get("confirm_password")?.toString() ?? "";

  if (password !== confirmPassword) {
    showFeedback(setupFeedback, "Hasla musza byc identyczne.");
    return;
  }

  if (password.trim().length < 4) {
    showFeedback(setupFeedback, "Haslo musi miec co najmniej 4 znaki.");
    return;
  }

  const payload = {
    company_name: formData.get("company_name")?.toString().trim(),
    owner_name: formData.get("owner_name")?.toString().trim(),
    address_line: formData.get("address_line")?.toString().trim(),
    postal_code: formData.get("postal_code")?.toString().trim(),
    city: formData.get("city")?.toString().trim(),
    tax_id: formData.get("tax_id")?.toString().trim(),
    bank_account: formData.get("bank_account")?.toString().trim(),
    password,
  };

  try {
    await apiRequest("/api/setup", { method: "POST", body: payload });
    showFeedback(setupFeedback, "Dane zapisane. Mozesz sie zalogowac.", "success");
    setTimeout(() => {
      setState("login");
      clearFeedback(setupFeedback);
      setupForm.reset();
    }, 1500);
  } catch (error) {
    showFeedback(setupFeedback, error.message || "Nie udalo sie zapisac danych.");
  }
});

loginForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  clearFeedback(loginFeedback);

  const password = loginForm.elements.password.value;
  if (!password) {
    showFeedback(loginFeedback, "Podaj haslo.");
    return;
  }

  try {
    const response = await apiRequest("/api/login", { method: "POST", body: { password } });
    authToken = response.token;
    sessionStorage.setItem("invoiceAuthToken", authToken);
    loginForm.reset();
    await bootstrapApp();
  } catch (error) {
    showFeedback(loginFeedback, error.message || "Logowanie nie powiodlo sie.");
  }
});

toggleBusinessFormButton.addEventListener("click", () => {
  const isHidden = businessForm.classList.contains("hidden");
  if (isHidden) {
    fillBusinessForm(currentBusiness);
    businessForm.classList.remove("hidden");
    toggleBusinessFormButton.textContent = "Ukryj formularz";
  } else {
    businessForm.classList.add("hidden");
    toggleBusinessFormButton.textContent = "Edytuj dane";
    clearFeedback(businessFeedback);
  }
});

cancelBusinessUpdateButton.addEventListener("click", () => {
  businessForm.classList.add("hidden");
  toggleBusinessFormButton.textContent = "Edytuj dane";
  clearFeedback(businessFeedback);
});

businessForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  clearFeedback(businessFeedback);

  const formData = new FormData(businessForm);
  const payload = {
    company_name: formData.get("company_name")?.toString().trim(),
    owner_name: formData.get("owner_name")?.toString().trim(),
    address_line: formData.get("address_line")?.toString().trim(),
    postal_code: formData.get("postal_code")?.toString().trim(),
    city: formData.get("city")?.toString().trim(),
    tax_id: formData.get("tax_id")?.toString().trim(),
    bank_account: formData.get("bank_account")?.toString().trim(),
  };

  try {
    const data = await apiRequest("/api/business", { method: "PUT", body: payload }, true);
    currentBusiness = data.business;
    renderBusinessDisplay(currentBusiness);
    showFeedback(businessFeedback, "Dane sprzedawcy zaktualizowane.", "success");
    setTimeout(() => clearFeedback(businessFeedback), 2000);
  } catch (error) {
    showFeedback(businessFeedback, error.message || "Nie udalo sie zaktualizowac danych.");
  }
});

invoiceForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  try {
    const payload = collectInvoicePayload();
    const response = await apiRequest("/api/invoices", { method: "POST", body: payload }, true);
    lastInvoice = response.invoice;
    renderInvoicePreview(lastInvoice);
    invoiceResult.classList.remove("hidden");
    resetInvoiceForm();
  } catch (error) {
    alert(error.message || "Nie udalo sie wygenerowac faktury.");
  }
});

addItemButton.addEventListener("click", () => {
  createItemRow();
});

downloadButton.addEventListener("click", async () => {
  if (!lastInvoice || !currentBusiness) {
    alert("Brak faktury do pobrania. Wygeneruj ja najpierw.");
    return;
  }
  await generatePdf(currentBusiness, lastInvoice);
});

logoutButton.addEventListener("click", () => {
  authToken = null;
  sessionStorage.removeItem("invoiceAuthToken");
  lastInvoice = null;
  currentBusiness = null;
  invoiceResult.classList.add("hidden");
  setState("login");
});

initialize().catch((error) => {
  console.error(error);
  showFeedback(setupFeedback, "Nie udalo sie uruchomic aplikacji.");
});