app/src/app.js

@@ -5,7 +5,7 @@ const archiver = require('archiver');
 const PDFDocument = require('pdfkit');
 const QRCode = require('qrcode');
 const { pool, initializeDatabase } = require('./db');
-const { normalizeInvoiceData } = require('./invoice-data');
+const { isValidSignatureDataUrl, normalizeInvoiceData } = require('./invoice-data');
 
 const app = express();
 const sessionDurationMs = 1000 * 60 * 60 * 24 * 30;
@@ -362,6 +362,57 @@ app.delete('/api/payment-presets/:id', requireAuth, async (req, res, next) => {
     }
 });
 
+const signaturePresetResponse = (row) => ({
+    id: row.id,
+    name: row.name,
+    dataUrl: row.data_url
+});
+
+app.get('/api/signature-presets', requireAuth, async (req, res, next) => {
+    try {
+        const result = await pool.query(
+            'SELECT * FROM signature_presets WHERE user_id = $1 ORDER BY name',
+            [req.userId]
+        );
+        res.json({ presets: result.rows.map(signaturePresetResponse) });
+    } catch (error) {
+        next(error);
+    }
+});
+
+app.post('/api/signature-presets', requireAuth, async (req, res, next) => {
+    try {
+        const name = String(req.body.name || '').trim();
+        const dataUrl = req.body.dataUrl;
+        if (!name) {
+            res.status(400).json({ error: 'Zadejte název podpisu.' });
+            return;
+        }
+        if (!isValidSignatureDataUrl(dataUrl)) {
+            res.status(400).json({ error: 'Podpis musí být platný obrázek JPG nebo PNG.' });
+            return;
+        }
+        const result = await pool.query(`
+            INSERT INTO signature_presets (user_id, name, data_url)
+            VALUES ($1, $2, $3)
+            ON CONFLICT (user_id, name) DO UPDATE SET data_url = EXCLUDED.data_url
+            RETURNING *
+        `, [req.userId, name, dataUrl]);
+        res.status(201).json({ preset: signaturePresetResponse(result.rows[0]) });
+    } catch (error) {
+        next(error);
+    }
+});
+
+app.delete('/api/signature-presets/:id', requireAuth, async (req, res, next) => {
+    try {
+        await pool.query('DELETE FROM signature_presets WHERE id = $1 AND user_id = $2', [req.params.id, req.userId]);
+        res.status(204).end();
+    } catch (error) {
+        next(error);
+    }
+});
+
 const invoiceResponse = (row) => ({
     id: row.id,
     invoiceNumber: row.invoice_number,

app/src/db.js

@@ -81,6 +81,15 @@ const initializeDatabase = () => {
                 UNIQUE (user_id, name)
             );
 
+            CREATE TABLE IF NOT EXISTS signature_presets (
+                id SERIAL PRIMARY KEY,
+                user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+                name TEXT NOT NULL,
+                data_url TEXT NOT NULL,
+                created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+                UNIQUE (user_id, name)
+            );
+
             ALTER TABLE supplier_profiles ADD COLUMN IF NOT EXISTS nazev_spolecnosti TEXT NOT NULL DEFAULT '';
             ALTER TABLE supplier_profiles ADD COLUMN IF NOT EXISTS typ_subjektu TEXT NOT NULL DEFAULT 'osoba';
             ALTER TABLE clients ADD COLUMN IF NOT EXISTS nazev_spolecnosti TEXT NOT NULL DEFAULT '';

app/src/invoice-data.js

@@ -1,5 +1,8 @@
 const SIGNATURE_DATA_URL_PATTERN = /^data:image\/(png|jpeg);base64,[A-Za-z0-9+/]+=*$/;
 
+const isValidSignatureDataUrl = (value) => typeof value === 'string'
+    && SIGNATURE_DATA_URL_PATTERN.test(value);
+
 const normalizeInvoiceData = (data) => {
     if (!data || !Array.isArray(data.items)) {
         return null;
@@ -18,7 +21,7 @@ const normalizeInvoiceData = (data) => {
         return null;
     }
 
-    const signature = typeof data.signature === 'string' && SIGNATURE_DATA_URL_PATTERN.test(data.signature)
+    const signature = isValidSignatureDataUrl(data.signature)
         ? data.signature
         : null;
 
@@ -32,4 +35,4 @@ const normalizeInvoiceData = (data) => {
     };
 };
 
-module.exports = { normalizeInvoiceData };
+module.exports = { isValidSignatureDataUrl, normalizeInvoiceData };

app/src/static/index.html

@@ -338,11 +338,22 @@
                 <div class="form-chapter signature-row">
                     <div class="form-group signature-group">
                         <label for="signatureInput">Podpis (nepovinné)</label>
+                        <div class="form-group">
+                            <label for="signaturePresetSelect">Uložený podpis</label>
+                            <select id="signaturePresetSelect">
+                                <option value="">Vyberte podpis</option>
+                            </select>
+                        </div>
                         <div id="signatureDropzone" class="signature-dropzone" tabindex="0" role="button" aria-label="Nahrát podpis kliknutím nebo přetažením souboru">
-                            <img id="signaturePreview" class="signature-preview" alt="Náhled podpisu" hidden />
+                            <img id="signaturePreview" class="signature-preview" alt="Náhled podpisu" src="data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=" hidden />
                             <p id="signatureDropzoneText" class="signature-dropzone-text">Přetáhněte sem obrázek podpisu (420×210 px, JPG nebo PNG) nebo klikněte pro výběr souboru</p>
                             <input type="file" id="signatureInput" accept="image/png,image/jpeg" hidden />
                         </div>
+                        <div class="signature-save-row">
+                            <input id="signaturePresetName" type="text" placeholder="Název podpisu" aria-label="Název podpisu" />
+                            <button type="button" id="saveSignaturePresetButton">Uložit podpis</button>
+                            <button type="button" id="deleteSignaturePresetButton" class="secondary-button" disabled>Smazat</button>
+                        </div>
                         <div class="signature-actions">
                             <button type="button" id="removeSignatureButton" class="secondary-button" hidden>Odstranit podpis</button>
                         </div>

app/src/static/script.js

@@ -57,6 +57,10 @@ const signaturePreview = document.getElementById("signaturePreview");
 const signatureDropzoneText = document.getElementById("signatureDropzoneText");
 const removeSignatureButton = document.getElementById("removeSignatureButton");
 const signatureStatus = document.getElementById("signatureStatus");
+const signaturePresetSelect = document.getElementById("signaturePresetSelect");
+const signaturePresetName = document.getElementById("signaturePresetName");
+const saveSignaturePresetButton = document.getElementById("saveSignaturePresetButton");
+const deleteSignaturePresetButton = document.getElementById("deleteSignaturePresetButton");
 const loadPaymentPresetButton = document.getElementById("loadPaymentPresetButton");
 const deletePaymentPresetButton = document.getElementById("deletePaymentPresetButton");
 
@@ -78,6 +82,7 @@ let itemIndex = 0;
 let clients = [];
 let invoices = [];
 let paymentPresets = [];
+let signaturePresets = [];
 let currentInvoiceId = null;
 let isRegistrationMode = false;
 let signatureDataUrl = null;
@@ -99,12 +104,30 @@ const applySignaturePreview = (dataUrl) => {
         removeSignatureButton.hidden = false;
     } else {
         signaturePreview.hidden = true;
-        signaturePreview.src = "";
+        signaturePreview.removeAttribute("src");
         signatureDropzoneText.hidden = false;
         removeSignatureButton.hidden = true;
     }
 };
 
+const renderSignaturePresetOptions = (selectedId = signaturePresetSelect.value) => {
+    signaturePresetSelect.innerHTML = "<option value=\"\">Vyberte podpis</option>";
+    signaturePresets.forEach((preset) => {
+        const option = document.createElement("option");
+        option.value = preset.id;
+        option.textContent = preset.name;
+        signaturePresetSelect.appendChild(option);
+    });
+    signaturePresetSelect.value = selectedId;
+    deleteSignaturePresetButton.disabled = !signaturePresetSelect.value;
+};
+
+const loadSignaturePresets = async () => {
+    const response = await apiRequest("/api/signature-presets");
+    signaturePresets = response.presets;
+    renderSignaturePresetOptions();
+};
+
 const readImageDimensions = (dataUrl) => new Promise((resolve, reject) => {
     const image = new Image();
     image.onload = () => resolve({ width: image.naturalWidth, height: image.naturalHeight });
@@ -162,6 +185,53 @@ signatureInput.addEventListener("change", () => {
     handleSignatureFile(signatureInput.files[0]);
     signatureInput.value = "";
 });
+signaturePresetSelect.addEventListener("change", () => {
+    const preset = signaturePresets.find(({ id }) => String(id) === signaturePresetSelect.value);
+    deleteSignaturePresetButton.disabled = !preset;
+    if (preset) {
+        signaturePresetName.value = preset.name;
+        applySignaturePreview(preset.dataUrl);
+        setSignatureStatus("Uložený podpis načten.");
+    }
+});
+saveSignaturePresetButton.addEventListener("click", async () => {
+    if (!signatureDataUrl) {
+        setSignatureStatus("Nejprve nahrajte nebo vyberte podpis.", true);
+        return;
+    }
+    try {
+        const response = await apiRequest("/api/signature-presets", {
+            method: "POST",
+            body: JSON.stringify({
+                name: signaturePresetName.value,
+                dataUrl: signatureDataUrl
+            })
+        });
+        const preset = response.preset;
+        signaturePresets = [
+            ...signaturePresets.filter((entry) => entry.id !== preset.id && entry.name !== preset.name),
+            preset
+        ].sort((left, right) => left.name.localeCompare(right.name));
+        renderSignaturePresetOptions(String(preset.id));
+        signaturePresetName.value = preset.name;
+        setSignatureStatus("Podpis byl uložen.");
+    } catch (error) {
+        setSignatureStatus(error.message, true);
+    }
+});
+deleteSignaturePresetButton.addEventListener("click", async () => {
+    if (!signaturePresetSelect.value) {
+        return;
+    }
+    try {
+        await apiRequest(`/api/signature-presets/${signaturePresetSelect.value}`, { method: "DELETE" });
+        signaturePresets = signaturePresets.filter(({ id }) => String(id) !== signaturePresetSelect.value);
+        signaturePresetName.value = "";
+        renderSignaturePresetOptions();
+    } catch (error) {
+        setSignatureStatus(error.message, true);
+    }
+});
 removeSignatureButton.addEventListener("click", (event) => {
     event.stopPropagation();
     applySignaturePreview(null);
@@ -374,6 +444,9 @@ const clearInvoiceEditor = () => {
     paymentPresetSelect.value = "";
     paymentPresetName.value = "";
     deletePaymentPresetButton.disabled = true;
+    signaturePresetSelect.value = "";
+    signaturePresetName.value = "";
+    deleteSignaturePresetButton.disabled = true;
     ["cisloUctu", "iban", "swift"].forEach((id) => {
         document.getElementById(id).value = "";
     });
@@ -403,6 +476,9 @@ const loadInvoiceIntoEditor = (invoice) => {
         document.getElementById(id).value = invoice.data.payment?.[id] || "";
     });
     applySignaturePreview(invoice.data.signature || null);
+    signaturePresetSelect.value = "";
+    signaturePresetName.value = "";
+    deleteSignaturePresetButton.disabled = true;
     setSignatureStatus("");
     itemsContainer.replaceChildren();
     itemIndex = 0;
@@ -629,7 +705,7 @@ deleteClientButton.addEventListener("click", async () => {
 const showInvoiceApp = async () => {
     authScreen.hidden = true;
     document.getElementById("main-container").hidden = false;
-    await Promise.all([loadSupplier(), loadClients(), loadInvoices(), loadPaymentPresets(), loadNumberingSettings()]);
+    await Promise.all([loadSupplier(), loadClients(), loadInvoices(), loadPaymentPresets(), loadSignaturePresets(), loadNumberingSettings()]);
     showInvoiceScreen("list");
 };
 

app/src/static/style.css

@@ -682,6 +682,56 @@ body {
     margin-top: 0.5rem;
 }
 
+.signature-save-row {
+    display: grid;
+    grid-template-columns: minmax(0, 1fr) auto auto;
+    gap: 0.5rem;
+    margin-top: 0.75rem;
+}
+
+.signature-save-row input {
+    min-width: 0;
+    padding: 0.55rem 0.7rem;
+    color: var(--ink);
+    background: #fff;
+    border: 1px solid #c8d0d5;
+    border-radius: 0.25rem;
+    font: inherit;
+}
+
+.signature-save-row button {
+    padding: 0.55rem 0.7rem;
+    color: var(--navy);
+    background: transparent;
+    border: 1px solid var(--blue);
+    border-radius: 0.25rem;
+    cursor: pointer;
+    font: inherit;
+    font-size: 0.85rem;
+    font-weight: 700;
+    white-space: nowrap;
+}
+
+.signature-save-row button:hover:not(:disabled) {
+    color: #fff;
+    background: var(--blue);
+}
+
+.signature-save-row .secondary-button {
+    color: #8c3c36;
+    border-color: #c47a72;
+}
+
+.signature-save-row .secondary-button:hover:not(:disabled) {
+    color: #fff;
+    background: #a53c36;
+}
+
+.signature-save-row button:disabled {
+    cursor: not-allowed;
+    opacity: 0.45;
+}
+
 .signature-status {
     margin: 0.4rem 0 0;
     min-height: 1.1rem;
@@ -963,6 +1013,10 @@ select:focus {
         grid-template-columns: 1fr;
     }
 
+    .signature-save-row {
+        grid-template-columns: 1fr;
+    }
+
     .delete-item-button {
         justify-self: end;
     }

app/test/app.test.js

@@ -1,4 +1,4 @@
-const { normalizeInvoiceData } = require('../src/invoice-data');
+const { isValidSignatureDataUrl, normalizeInvoiceData } = require('../src/invoice-data');
 
 describe('normalizeInvoiceData', () => {
     test('calculates the total from validated line items', () => {
@@ -49,4 +49,10 @@ describe('normalizeInvoiceData', () => {
         });
         expect(withoutSignature.signature).toBeNull();
     });
+
+    test('validates only supported base64 signature image data URLs', () => {
+        expect(isValidSignatureDataUrl('data:image/jpeg;base64,aGVsbG8=')).toBe(true);
+        expect(isValidSignatureDataUrl('data:image/gif;base64,aGVsbG8=')).toBe(false);
+        expect(isValidSignatureDataUrl('data:image/png;base64,not valid')).toBe(false);
+    });
 });