feat: expandable error details with copy-to-clipboard (closes #143)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/app/app.html

@@ -456,20 +456,42 @@
                   <fa-icon [icon]="faCheckCircle" class="text-success" />
                 }
                 @if (download.value.status === 'error') {
-                  <fa-icon [icon]="faTimesCircle" class="text-danger" />
+                  <fa-icon [icon]="faTimesCircle" class="text-danger" style="cursor: pointer;" (click)="toggleErrorDetail(download.key)" />
                 }
               </div>
               <span ngbTooltip="{{buildResultItemTooltip(download.value)}}">@if (!!download.value.filename) {
                 <a href="{{buildDownloadLink(download.value)}}" target="_blank">{{ download.value.title }}</a>
               } @else {
-                {{download.value.title}}
+                <span [style.cursor]="download.value.status === 'error' ? 'pointer' : 'default'"
-                @if (download.value.msg) {
+                  (click)="download.value.status === 'error' ? toggleErrorDetail(download.key) : null">
-                  <span><br>{{download.value.msg}}</span>
+                  {{download.value.title}}
-                }
+                  @if (download.value.status === 'error' && !isErrorExpanded(download.key)) {
-                @if (download.value.error) {
+                    <small class="text-danger ms-2">
-                  <span><br>Error: {{download.value.error}}</span>
+                      <fa-icon [icon]="faChevronRight" size="xs" class="me-1" />Click for details
-                }
+                    </small>
+                  }
+                </span>
               }</span>
+              @if (download.value.status === 'error' && isErrorExpanded(download.key)) {
+                <div class="alert alert-danger py-2 px-3 mt-2 mb-0 small" style="border-left: 4px solid var(--bs-danger);">
+                  <div class="d-flex justify-content-between align-items-start">
+                    <div class="flex-grow-1">
+                      @if (download.value.msg) {
+                        <div class="mb-1"><strong>Message:</strong> {{download.value.msg}}</div>
+                      }
+                      @if (download.value.error) {
+                        <div class="mb-1"><strong>Error:</strong> {{download.value.error}}</div>
+                      }
+                      <div class="text-muted" style="word-break: break-all;"><strong>URL:</strong> {{download.value.url}}</div>
+                    </div>
+                    <button type="button" class="btn btn-sm btn-outline-danger ms-2 flex-shrink-0"
+                      (click)="copyErrorMessage(download.value); $event.stopPropagation()"
+                      ngbTooltip="Copy error details to clipboard">
+                      <fa-icon [icon]="faCopy" />
+                    </button>
+                  </div>
+                </div>
+              }
             </td>
             <td>
               @if (download.value.size) {

ui/src/app/app.ts

@@ -6,7 +6,7 @@ import { FormsModule } from '@angular/forms';
 import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';
 import { NgbModule } from '@ng-bootstrap/ng-bootstrap';
 import { NgSelectModule } from '@ng-select/ng-select';  
-import { faTrashAlt, faCheckCircle, faTimesCircle, faRedoAlt, faSun, faMoon, faCheck, faCircleHalfStroke, faDownload, faExternalLinkAlt, faFileImport, faFileExport, faCopy, faClock, faTachometerAlt } from '@fortawesome/free-solid-svg-icons';
+import { faTrashAlt, faCheckCircle, faTimesCircle, faRedoAlt, faSun, faMoon, faCheck, faCircleHalfStroke, faDownload, faExternalLinkAlt, faFileImport, faFileExport, faCopy, faClock, faTachometerAlt, faChevronRight } from '@fortawesome/free-solid-svg-icons';
 import { faGithub } from '@fortawesome/free-brands-svg-icons';
 import { CookieService } from 'ngx-cookie-service';
 import { DownloadsService } from './services/downloads.service';
@@ -66,6 +66,7 @@ export class App implements AfterViewInit, OnInit {
   ytDlpVersion: string | null = null;
   metubeVersion: string | null = null;
   isAdvancedOpen = false;
+  expandedErrors: Set<string> = new Set();
 
   // Download metrics
   activeDownloads = 0;
@@ -100,6 +101,7 @@ export class App implements AfterViewInit, OnInit {
   faGithub = faGithub;
   faClock = faClock;
   faTachometerAlt = faTachometerAlt;
+  faChevronRight = faChevronRight;
   subtitleFormats = [
     { id: 'srt', text: 'SRT' },
     { id: 'txt', text: 'TXT (Text only)' },
@@ -699,6 +701,24 @@ export class App implements AfterViewInit, OnInit {
     this.isAdvancedOpen = !this.isAdvancedOpen;
   }
 
+  toggleErrorDetail(id: string) {
+    if (this.expandedErrors.has(id)) this.expandedErrors.delete(id);
+    else this.expandedErrors.add(id);
+  }
+
+  copyErrorMessage(download: Download) {
+    const parts: string[] = [];
+    if (download.title) parts.push(`Title: ${download.title}`);
+    if (download.url) parts.push(`URL: ${download.url}`);
+    if (download.msg) parts.push(`Message: ${download.msg}`);
+    if (download.error) parts.push(`Error: ${download.error}`);
+    navigator.clipboard.writeText(parts.join('\n')).catch(() => {});
+  }
+
+  isErrorExpanded(id: string): boolean {
+    return this.expandedErrors.has(id);
+  }
+
   private updateMetrics() {
     this.activeDownloads = Array.from(this.downloads.queue.values()).filter(d => d.status === 'downloading' || d.status === 'preparing').length;
     this.queuedDownloads = Array.from(this.downloads.queue.values()).filter(d => d.status === 'pending').length;