feat: implement script review workflow in App component

- Add 'review' phase to application state
- Add scriptSegments state variable for storing AI-generated segments
- Add isGeneratingScript loading state for script generation
- Implement handleGenerateScript() to call API and transition to review phase
- Implement handleSkipReview() to bypass review and go directly to generation
- Implement handleSegmentChange() to update speaker assignments in segments
- Update handleGenerate() to use edited segments when available
- Wire up ScriptReviewSection component in review phase
- Update phase transitions: input → assignment → review → generated
- Add loading indicator for script generation

Validates Requirements: 15.1, 15.3, 15.6, 15.7, 15.8
Task: 22. Update App component for script review workflow

frontend/src/App.tsx

@@ -2,18 +2,21 @@ import { useState } from 'react'
 import './App.css'
 import TextInputSection from './components/TextInputSection'
 import VoiceAssignmentSection from './components/VoiceAssignmentSection'
+import ScriptReviewSection from './components/ScriptReviewSection'
 import AudioPlayerSection from './components/AudioPlayerSection'
-import type { Role } from './api/tts'
-import { detectRoles, generateAudiobook } from './api/tts'
+import type { Role, ScriptSegment } from './api/tts'
+import { detectRoles, generateScript, generateAudiobook } from './api/tts'
 
 function App() {
   const [text, setText] = useState('')
-  const [phase, setPhase] = useState<'input' | 'assignment' | 'generated'>('input')
+  const [phase, setPhase] = useState<'input' | 'assignment' | 'review' | 'generated'>('input')
   const [isLoading, setIsLoading] = useState(false)
   const [roles, setRoles] = useState<Role[]>([])
   const [voiceAssignments, setVoiceAssignments] = useState<Map<string, string>>(new Map())
+  const [scriptSegments, setScriptSegments] = useState<ScriptSegment[]>([])
   const [language, setLanguage] = useState('a') // Default: American English
   const [speed, setSpeed] = useState(1.0) // Default: 1.0x
+  const [isGeneratingScript, setIsGeneratingScript] = useState(false)
   const [isGenerating, setIsGenerating] = useState(false)
   const [error, setError] = useState<string | null>(null)
   const [audioUrl, setAudioUrl] = useState<string | null>(null)
@@ -60,6 +63,45 @@ function App() {
     setSpeed(newSpeed)
   }
 
+  const handleGenerateScript = async () => {
+    setIsGeneratingScript(true)
+    setError(null)
+    
+    try {
+      // Generate script preview with AI segmentation
+      const roleIds = roles.map(role => role.id)
+      const response = await generateScript({
+        text,
+        roles: roleIds
+      })
+      
+      setScriptSegments(response.segments)
+      
+      // Move to review phase
+      setPhase('review')
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'Failed to generate script')
+      console.error('Script generation error:', err)
+    } finally {
+      setIsGeneratingScript(false)
+    }
+  }
+
+  const handleSkipReview = async () => {
+    // Skip review and go directly to generation
+    await handleGenerate()
+  }
+
+  const handleSegmentChange = (segmentId: string, newSpeaker: string) => {
+    setScriptSegments(prev => 
+      prev.map(segment => 
+        segment.id === segmentId 
+          ? { ...segment, speaker: newSpeaker }
+          : segment
+      )
+    )
+  }
+
   const handleGenerate = async () => {
     setIsGenerating(true)
     setError(null)
@@ -72,8 +114,11 @@ function App() {
       }))
       
       // Generate the audiobook
+      // If we have script segments (from review phase), use them
+      // Otherwise, fall back to text-based generation
       const audioBlob = await generateAudiobook({
-        text,
+        segments: scriptSegments.length > 0 ? scriptSegments : undefined,
+        text: scriptSegments.length > 0 ? undefined : text,
         lang: language,
         roles: rolesArray,
         speed
@@ -149,13 +194,31 @@ function App() {
               onLanguageChange={handleLanguageChange}
               speed={speed}
               onSpeedChange={handleSpeedChange}
-              onGenerate={handleGenerate}
-              isGenerating={isGenerating}
+              onGenerate={handleGenerateScript}
+              isGenerating={isGeneratingScript}
               allRolesAssigned={allRolesAssigned}
             />
           </>
         )}
 
+        {phase === 'review' && (
+          <>
+            {isLongText && (
+              <div className="max-w-4xl mx-auto mb-4 p-3 sm:p-4 bg-yellow-100 border border-yellow-400 text-yellow-800 rounded text-sm sm:text-base">
+                Generation may take several minutes for very long content.
+              </div>
+            )}
+            <ScriptReviewSection
+              segments={scriptSegments}
+              roles={roles}
+              onSegmentChange={handleSegmentChange}
+              onGenerate={handleGenerate}
+              onSkipReview={handleSkipReview}
+              isGenerating={isGenerating}
+            />
+          </>
+        )}
+
         {phase === 'generated' && audioUrl && (
           <AudioPlayerSection
             audioUrl={audioUrl}
@@ -168,6 +231,12 @@ function App() {
             Generation may take several minutes for very long content. Please be patient...
           </div>
         )}
+
+        {isGeneratingScript && (
+          <div className="max-w-4xl mx-auto mt-4 p-3 sm:p-4 bg-blue-100 border border-blue-400 text-blue-800 rounded text-center text-sm sm:text-base">
+            Generating script preview... This may take a moment.
+          </div>
+        )}
       </div>
     </div>
   )