feat(ext): draft extension structure (single-page mode)

packages/extension/src/entrypoints/background.ts

@@ -0,0 +1,178 @@
+/**
+ * Background Script Entry Point
+ *
+ * This script runs as the extension's service worker and hosts:
+ * - PageAgentCore (headless agent)
+ * - RemotePageController (proxy to ContentScript)
+ * - Command handlers for SidePanel
+ * - Event broadcasting to SidePanel
+ */
+import { PageAgentCore } from '@page-agent/core'
+
+import { RemotePageController } from '../agent/RemotePageController'
+import { eventBroadcaster } from '../messaging/events'
+import {
+	type AgentActivity,
+	type AgentState,
+	type AgentStatus,
+	type HistoricalEvent,
+	agentCommands,
+} from '../messaging/protocol'
+import { DEMO_API_KEY, DEMO_BASE_URL, DEMO_MODEL } from '../utils/constants'
+
+// Agent instance (singleton for now - single page control)
+let agent: PageAgentCore | null = null
+
+// LLM configuration (persisted in storage)
+interface LLMConfig {
+	apiKey: string
+	baseURL: string
+	model: string
+}
+
+// Default to demo config
+let llmConfig: LLMConfig = {
+	apiKey: DEMO_API_KEY,
+	baseURL: DEMO_BASE_URL,
+	model: DEMO_MODEL,
+}
+
+export default defineBackground(() => {
+	console.log('[PageAgentExt] Background script started')
+
+	// Load saved config from storage
+	loadConfig()
+
+	// Register command handlers
+	registerCommandHandlers()
+
+	// Open sidepanel on action click
+	chrome.sidePanel
+		.setPanelBehavior({ openPanelOnActionClick: true })
+		.catch((error) => console.error('[PageAgentExt] Failed to set panel behavior:', error))
+})
+
+/**
+ * Load LLM configuration from storage (falls back to demo config)
+ */
+async function loadConfig(): Promise<void> {
+	const result = await chrome.storage.local.get('llmConfig')
+	if (result.llmConfig) {
+		llmConfig = result.llmConfig as LLMConfig
+		console.log('[PageAgentExt] Loaded LLM config from storage')
+	} else {
+		console.log('[PageAgentExt] Using default demo config')
+	}
+}
+
+/**
+ * Save LLM configuration to storage
+ */
+async function saveConfig(config: LLMConfig): Promise<void> {
+	llmConfig = config
+	await chrome.storage.local.set({ llmConfig: config })
+	console.log('[PageAgentExt] Saved LLM config')
+}
+
+/**
+ * Get current agent state snapshot
+ */
+function getAgentState(): AgentState {
+	if (!agent) {
+		return {
+			status: 'idle',
+			task: '',
+			history: [],
+		}
+	}
+
+	return {
+		status: agent.status as AgentStatus,
+		task: agent.task,
+		history: agent.history as HistoricalEvent[],
+	}
+}
+
+/**
+ * Create and configure agent instance
+ */
+function createAgent(): PageAgentCore {
+	const pageController = new RemotePageController()
+
+	const newAgent = new PageAgentCore({
+		...llmConfig,
+		pageController: pageController as any, // Type assertion for interface compatibility
+		language: 'en-US',
+	})
+
+	// Forward agent events to SidePanel
+	newAgent.addEventListener('statuschange', () => {
+		eventBroadcaster.status(newAgent.status as AgentStatus)
+	})
+
+	newAgent.addEventListener('historychange', () => {
+		eventBroadcaster.history(newAgent.history as HistoricalEvent[])
+	})
+
+	newAgent.addEventListener('activity', (e) => {
+		const activity = (e as CustomEvent).detail as AgentActivity
+		eventBroadcaster.activity(activity)
+	})
+
+	newAgent.addEventListener('dispose', () => {
+		if (agent === newAgent) {
+			agent = null
+		}
+		eventBroadcaster.status('idle')
+	})
+
+	return newAgent
+}
+
+/**
+ * Register command handlers for SidePanel communication
+ */
+function registerCommandHandlers(): void {
+	// Execute task
+	agentCommands.onMessage('agent:execute', async ({ data: task }) => {
+		console.log('[PageAgentExt] Executing task:', task)
+
+		// Create new agent if needed
+		if (!agent || agent.disposed) {
+			agent = createAgent()
+		}
+
+		// Execute task (don't await - runs in background)
+		agent.execute(task).catch((error) => {
+			console.error('[PageAgentExt] Task execution error:', error)
+			eventBroadcaster.status('error')
+		})
+	})
+
+	// Stop agent
+	agentCommands.onMessage('agent:stop', async () => {
+		console.log('[PageAgentExt] Stopping agent')
+		if (agent) {
+			agent.dispose('User requested stop')
+			agent = null
+		}
+	})
+
+	// Get current state
+	agentCommands.onMessage('agent:getState', async () => {
+		return getAgentState()
+	})
+
+	// Configure LLM
+	agentCommands.onMessage('agent:configure', async ({ data: config }) => {
+		await saveConfig(config)
+
+		// Recreate agent with new config if it exists
+		if (agent && !agent.disposed) {
+			agent.dispose('Configuration changed')
+			agent = null
+		}
+	})
+
+	console.log('[PageAgentExt] Command handlers registered')
+}