feat(frontend): wire Documents tab to live document endpoints

frontend/app/page.tsx

@@ -1,13 +1,76 @@
 'use client'
 
-import { useState } from 'react'
-import { askQuestion, listDocuments, listMessages } from '@/lib/api'
+import { useEffect, useState } from 'react'
+import {
+  askQuestion,
+  getDocument,
+  listDocuments,
+  type Document,
+  type DocumentDetail,
+} from '@/lib/api'
+
+function formatDate(value?: string | null) {
+  if (!value) return ''
+  const date = new Date(value)
+  if (Number.isNaN(date.getTime())) return ''
+  return date.toLocaleDateString('en-AU', {
+    day: 'numeric',
+    month: 'short',
+    year: 'numeric',
+  })
+}
 
 export default function Home() {
   const [question, setQuestion] = useState('')
   const [answer, setAnswer] = useState('')
   const [loading, setLoading] = useState(false)
   const [activeTab, setActiveTab] = useState<'ask' | 'documents' | 'messages'>('ask')
+  const [documents, setDocuments] = useState<Document[]>([])
+  const [documentsTotal, setDocumentsTotal] = useState(0)
+  const [documentsLoading, setDocumentsLoading] = useState(false)
+  const [documentsError, setDocumentsError] = useState('')
+  const [selectedDocument, setSelectedDocument] = useState<DocumentDetail | null>(null)
+  const [detailLoading, setDetailLoading] = useState(false)
+  const [detailError, setDetailError] = useState('')
+
+  useEffect(() => {
+    if (activeTab !== 'documents') return
+    let cancelled = false
+    setDocumentsLoading(true)
+    setDocumentsError('')
+    listDocuments()
+      .then((data) => {
+        if (cancelled) return
+        setDocuments(data.items)
+        setDocumentsTotal(data.total)
+      })
+      .catch(() => {
+        if (cancelled) return
+        setDocuments([])
+        setDocumentsTotal(0)
+        setDocumentsError('Could not load documents. Check the backend is running and try again.')
+      })
+      .finally(() => {
+        if (!cancelled) setDocumentsLoading(false)
+      })
+    return () => {
+      cancelled = true
+    }
+  }, [activeTab])
+
+  const handleSelectDocument = async (doc: Document) => {
+    setDetailLoading(true)
+    setDetailError('')
+    try {
+      const detail = await getDocument(doc.id)
+      setSelectedDocument(detail)
+    } catch {
+      setSelectedDocument(null)
+      setDetailError('Could not load this document. Try again.')
+    } finally {
+      setDetailLoading(false)
+    }
+  }
 
   const handleAsk = async () => {
     if (!question.trim()) return
@@ -135,20 +198,91 @@ export default function Home() {
         {activeTab === 'documents' && (
           <div className="max-w-3xl mx-auto">
             <div className="bg-white rounded-xl shadow-lg p-8">
-              <h2 className="text-2xl font-semibold text-gray-800 mb-6">
+              <h2 className="text-2xl font-semibold text-gray-800 mb-2">
                 Knowledge Base Documents
               </h2>
-              <p className="text-gray-600">
-                Documents are indexed for retrieval-augmented generation.
-                Use the API to add new documents to the knowledge base.
+              <p className="text-gray-600 mb-6">
+                Indexed documents used for retrieval-augmented generation. Select one to read its full content.
               </p>
-              <div className="mt-6">
-                <code className="bg-gray-100 p-4 rounded-lg block text-sm text-gray-800">
-                  POST /api/documents
-                  <br />
-                  {`{ "title": "...", "content": "...", "source": "..." }`}
-                </code>
-              </div>
+
+              {documentsLoading && (
+                <p className="text-gray-600">Loading documents...</p>
+              )}
+
+              {!documentsLoading && documentsError && (
+                <div className="p-4 bg-red-50 rounded-lg">
+                  <p className="text-red-700">{documentsError}</p>
+                </div>
+              )}
+
+              {!documentsLoading && !documentsError && documents.length === 0 && (
+                <p className="text-gray-600">
+                  No documents yet. Add one with POST /api/documents and it will appear here.
+                </p>
+              )}
+
+              {!documentsLoading && !documentsError && documents.length > 0 && (
+                <>
+                  <p className="text-sm text-gray-500 mb-4">
+                    {documentsTotal} {documentsTotal === 1 ? 'document' : 'documents'}
+                  </p>
+                  <ul className="divide-y divide-gray-100">
+                    {documents.map((doc) => (
+                      <li key={doc.id}>
+                        <button
+                          onClick={() => handleSelectDocument(doc)}
+                          className={`w-full text-left py-4 px-3 rounded-lg transition-colors ${
+                            selectedDocument?.id === doc.id
+                              ? 'bg-blue-50'
+                              : 'hover:bg-gray-50'
+                          }`}
+                        >
+                          <span className="flex items-center justify-between gap-4">
+                            <span className="font-medium text-gray-800">{doc.title}</span>
+                            <span className="shrink-0 text-xs bg-gray-100 text-gray-600 px-2 py-1 rounded-full">
+                              {doc.source}
+                            </span>
+                          </span>
+                          {formatDate(doc.created_at) && (
+                            <span className="block text-sm text-gray-500 mt-1">
+                              {formatDate(doc.created_at)}
+                            </span>
+                          )}
+                          {doc.content_preview && (
+                            <span className="block text-sm text-gray-600 mt-1 line-clamp-2">
+                              {doc.content_preview}
+                            </span>
+                          )}
+                        </button>
+                      </li>
+                    ))}
+                  </ul>
+                </>
+              )}
+
+              {detailLoading && (
+                <p className="text-gray-600 mt-6">Loading document...</p>
+              )}
+
+              {!detailLoading && detailError && (
+                <div className="mt-6 p-4 bg-red-50 rounded-lg">
+                  <p className="text-red-700">{detailError}</p>
+                </div>
+              )}
+
+              {!detailLoading && !detailError && selectedDocument && (
+                <div className="mt-6 p-6 bg-blue-50 rounded-lg">
+                  <h3 className="text-lg font-semibold text-gray-800 mb-1">
+                    {selectedDocument.title}
+                  </h3>
+                  <p className="text-sm text-gray-500 mb-3">
+                    {selectedDocument.source}
+                    {formatDate(selectedDocument.created_at) &&
+                      ` - ${formatDate(selectedDocument.created_at)}`}
+                  </p>
+                  <p className="text-gray-700 whitespace-pre-wrap">{selectedDocument.content}</p>
+                </div>
+              )}
             </div>
           </div>
         )}