Phase 3 scaffold: chat engine (WebSocket, FCM, pricing, timer, extension, history)

- Backend: WebSocket plugin, chat/pricing/timer/extension/closure/notification services
- Client app: ChatBloc, pricing dialog, chat screen with message status, extension/goodbye flow, history
- Mitra app: MitraChatBloc, ExtensionBloc, chat screen, extension accept/reject, history
- Control center: free trial, extension timeout, early end config toggles
- DB migration: chat_messages, session_closures, session_extensions, customer_transactions tables

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/services/closure.service.js

@@ -0,0 +1,106 @@
+import { getDb } from '../db/client.js'
+import { publish } from '../plugins/valkey.js'
+import { clearSessionTimer } from './session-timer.service.js'
+import { sendToSessionParticipant } from '../plugins/websocket.js'
+
+const sql = getDb()
+
+export const submitClosureMessage = async (sessionId, userType, userId, message) => {
+  // Verify session is in closing or active state (for early end)
+  const [session] = await sql`
+    SELECT id, status FROM chat_sessions
+    WHERE id = ${sessionId} AND status IN ('closing', 'active', 'extending')
+  `
+  if (!session) {
+    throw Object.assign(new Error('Session not found or already completed'), {
+      code: 'SESSION_NOT_ACTIVE', statusCode: 409,
+    })
+  }
+
+  // Save closure message
+  const [closure] = await sql`
+    INSERT INTO session_closures (session_id, user_type, user_id, message)
+    VALUES (${sessionId}, ${userType}, ${userId}, ${message})
+    ON CONFLICT DO NOTHING
+    RETURNING id, session_id, user_type, message, created_at
+  `
+
+  // Check if both parties have submitted
+  const closures = await sql`
+    SELECT user_type FROM session_closures WHERE session_id = ${sessionId}
+  `
+  const hasCustomer = closures.some((c) => c.user_type === 'customer')
+  const hasMitra = closures.some((c) => c.user_type === 'mitra')
+
+  if (hasCustomer && hasMitra) {
+    // Both submitted — complete the session
+    await completeSession(sessionId)
+  }
+
+  return closure
+}
+
+export const completeSession = async (sessionId) => {
+  clearSessionTimer(sessionId)
+
+  const [session] = await sql`
+    UPDATE chat_sessions
+    SET status = 'completed', ended_at = NOW(), ended_by = 'system'
+    WHERE id = ${sessionId} AND status IN ('closing', 'active', 'extending')
+    RETURNING id, customer_id, mitra_id, status, ended_at
+  `
+  if (!session) return null
+
+  // Notify both parties
+  const data = { type: 'session_completed', session_id: sessionId }
+  sendToSessionParticipant(sessionId, 'customer', data)
+  sendToSessionParticipant(sessionId, 'mitra', data)
+
+  await publish(`session:${sessionId}:status`, { type: 'session_ended', session_id: sessionId })
+
+  return session
+}
+
+export const initiateEarlyEnd = async (sessionId, userType) => {
+  // Check if early end is enabled for this user type
+  const configKey = userType === 'mitra' ? 'early_end_mitra_enabled' : 'early_end_customer_enabled'
+  const [configRow] = await sql`SELECT value FROM app_config WHERE key = ${configKey}`
+  const enabled = configRow?.value?.value ?? false
+
+  if (!enabled) {
+    throw Object.assign(new Error('Early end is not enabled'), {
+      code: 'EARLY_END_DISABLED', statusCode: 403,
+    })
+  }
+
+  // Move session to closing
+  const [session] = await sql`
+    UPDATE chat_sessions
+    SET status = 'closing', ended_by = ${userType}
+    WHERE id = ${sessionId} AND status = 'active'
+    RETURNING id, customer_id, mitra_id
+  `
+  if (!session) {
+    throw Object.assign(new Error('Session not active'), {
+      code: 'SESSION_NOT_ACTIVE', statusCode: 409,
+    })
+  }
+
+  clearSessionTimer(sessionId)
+
+  // Notify both parties to enter closure flow
+  const data = { type: 'session_closing', session_id: sessionId, ended_by: userType }
+  sendToSessionParticipant(sessionId, 'customer', data)
+  sendToSessionParticipant(sessionId, 'mitra', data)
+
+  return session
+}
+
+export const getSessionClosures = async (sessionId) => {
+  return sql`
+    SELECT user_type, message, created_at
+    FROM session_closures
+    WHERE session_id = ${sessionId}
+    ORDER BY created_at ASC
+  `
+}