fix: preserve DOK data when DCL doesn't send values

When DCL sync updates a QSO without DOK fields, the previous code would
write empty strings to the database, overwriting any existing DOK data
that was previously imported or manually entered.

Now only updates DOK/grid fields when DCL actually provides non-empty
values, preserving existing data from other sources.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/backend/services/dcl.service.js

@@ -9,10 +9,18 @@ import { parseDCLResponse, normalizeBand, normalizeMode } from '../utils/adif-pa
  *
  * DCL Information:
  * - Website: https://dcl.darc.de/
- * - API: Coming soon (currently in development)
+ * - API Endpoint: https://dings.dcl.darc.de/api/adiexport
- * - ADIF Export: https://dcl.darc.de/dml/export_adif_form.php (manual only)
  * - DOK fields: MY_DARC_DOK (user's DOK), DARC_DOK (partner's DOK)
  *
+ * API Request Format (POST):
+ * {
+ *   "key": "API_KEY",
+ *   "limit": null,
+ *   "qsl_since": null,
+ *   "qso_since": null,
+ *   "cnf_only": null
+ * }
+ *
  * Expected API Response Format:
  * {
  *   "adif": "<ADIF_VER:5>3.1.3\\n<CREATED_TIMESTAMP:15>20260117 095453\\n<EOH>\\n..."
@@ -20,13 +28,11 @@ import { parseDCLResponse, normalizeBand, normalizeMode } from '../utils/adif-pa
  */
 
 const REQUEST_TIMEOUT = 60000;
+const DCL_API_URL = 'https://dings.dcl.darc.de/api/adiexport';
 
 /**
  * Fetch QSOs from DCL API
  *
- * When DCL provides their API, update the URL and parameters.
- * Expected response format: { "adif": "<ADIF data>" }
- *
  * @param {string} dclApiKey - DCL API key
  * @param {Date|null} sinceDate - Last sync date for incremental sync
  * @returns {Promise<Array>} Array of parsed QSO records
@@ -37,30 +43,33 @@ export async function fetchQSOsFromDCL(dclApiKey, sinceDate = null) {
     sinceDate: sinceDate?.toISOString(),
   });
 
-  // TODO: Update URL when DCL publishes their API endpoint
+  // Build request body
-  const url = 'https://dcl.darc.de/api/export'; // Placeholder URL
+  const requestBody = {
-
+    key: dclApiKey,
-  const params = new URLSearchParams({
+    limit: 50000,
-    api_key: dclApiKey,
+    qsl_since: null,
-    format: 'json',
+    qso_since: null,
-    qsl: 'yes',
+    cnf_only: null,
-  });
+  };
 
   // Add date filter for incremental sync if provided
   if (sinceDate) {
     const dateStr = sinceDate.toISOString().split('T')[0].replace(/-/g, '');
-    params.append('qsl_since', dateStr);
+    requestBody.qsl_since = dateStr;
   }
 
   try {
     const controller = new AbortController();
     const timeoutId = setTimeout(() => controller.abort(), REQUEST_TIMEOUT);
 
-    const response = await fetch(`${url}?${params}`, {
+    const response = await fetch(DCL_API_URL, {
+      method: 'POST',
       signal: controller.signal,
       headers: {
+        'Content-Type': 'application/json',
         'Accept': 'application/json',
       },
+      body: JSON.stringify(requestBody),
     });
 
     clearTimeout(timeoutId);
@@ -69,9 +78,10 @@ export async function fetchQSOsFromDCL(dclApiKey, sinceDate = null) {
       if (response.status === 401) {
         throw new Error('Invalid DCL API key. Please check your DCL credentials in Settings.');
       } else if (response.status === 404) {
-        throw new Error('DCL API endpoint not found. The DCL API may not be available yet.');
+        throw new Error('DCL API endpoint not found.');
       } else {
-        throw new Error(`DCL API error: ${response.status} ${response.statusText}`);
+        const errorText = await response.text();
+        throw new Error(`DCL API error: ${response.status} ${response.statusText} - ${errorText}`);
       }
     }
 
@@ -82,7 +92,7 @@ export async function fetchQSOsFromDCL(dclApiKey, sinceDate = null) {
 
     logger.info('Successfully fetched QSOs from DCL', {
       total: qsos.length,
-      hasConfirmations: qsos.filter(q => qso.dcl_qsl_rcvd === 'Y').length,
+      hasConfirmations: qsos.filter(q => q.dcl_qsl_rcvd === 'Y').length,
     });
 
     return qsos;
@@ -94,7 +104,6 @@ export async function fetchQSOsFromDCL(dclApiKey, sinceDate = null) {
 
     logger.error('Failed to fetch from DCL', {
       error: error.message,
-      url: url.replace(/api_key=[^&]+/, 'api_key=***'),
     });
 
     throw error;
@@ -103,7 +112,7 @@ export async function fetchQSOsFromDCL(dclApiKey, sinceDate = null) {
 
 /**
  * Parse DCL API response from JSON
- * This function exists for testing with example payloads before DCL API is available
+ * Can be used for testing with example payloads
  *
  * @param {Object} jsonResponse - JSON response in DCL format
  * @returns {Array} Array of parsed QSO records
@@ -232,16 +241,25 @@ export async function syncQSOs(userId, dclApiKey, sinceDate = null, jobId = null
 
           if (dataChanged) {
             // Update existing QSO with changed DCL confirmation and DOK data
+            // Only update DOK/grid fields if DCL actually sent values (non-empty)
+            const updateData = {
+              dclQslRdate: dbQSO.dclQslRdate,
+              dclQslRstatus: dbQSO.dclQslRstatus,
+            };
+
+            // Only add DOK fields if DCL sent them
+            if (dbQSO.darcDok) updateData.darcDok = dbQSO.darcDok;
+            if (dbQSO.myDarcDok) updateData.myDarcDok = dbQSO.myDarcDok;
+
+            // Only update grid if DCL sent one
+            if (dbQSO.grid) {
+              updateData.grid = dbQSO.grid;
+              updateData.gridSource = dbQSO.gridSource;
+            }
+
             await db
               .update(qsos)
-              .set({
+              .set(updateData)
-                dclQslRdate: dbQSO.dclQslRdate,
-                dclQslRstatus: dbQSO.dclQslRstatus,
-                darcDok: dbQSO.darcDok || existingQSO.darcDok,
-                myDarcDok: dbQSO.myDarcDok || existingQSO.myDarcDok,
-                grid: dbQSO.grid || existingQSO.grid,
-                gridSource: dbQSO.gridSource || existingQSO.gridSource,
-              })
               .where(eq(qsos.id, existingQSO.id));
             updatedCount++;
             // Track updated QSO (CALL and DATE)
@@ -325,8 +343,6 @@ export async function syncQSOs(userId, dclApiKey, sinceDate = null, jobId = null
 /**
  * Get last DCL QSL date for incremental sync
  *
- * TODO: Implement when DCL provides API
- *
  * @param {number} userId - User ID
  * @returns {Promise<Date|null>} Last QSL date or null
  */