/**
 * Session Persistence - Automatic session data persistence for L4 self-evolution
 *
 * Provides automatic persistence of conversation sessions:
 * - Periodic auto-save of session state
 * - Memory extraction at session end
 * - Context compaction for long sessions
 * - Session history and recovery
 *
 * Reference: ZCLAW_AGENT_INTELLIGENCE_EVOLUTION.md §6.4.4
 */

import { getVikingClient, type VikingHttpClient } from './viking-client';
import { getMemoryExtractor } from './memory-extractor';
import { canAutoExecute } from './autonomy-manager';

// === Types ===

export interface SessionMessage {
  id: string;
  role: 'user' | 'assistant' | 'system';
  content: string;
  timestamp: string;
  metadata?: Record<string, unknown>;
}

export interface SessionState {
  id: string;
  agentId: string;
  startedAt: string;
  lastActivityAt: string;
  messageCount: number;
  status: 'active' | 'paused' | 'ended';
  messages: SessionMessage[];
  metadata: {
    model?: string;
    workspaceId?: string;
    conversationId?: string;
    [key: string]: unknown;
  };
}

export interface SessionPersistenceConfig {
  enabled: boolean;
  autoSaveIntervalMs: number;      // Auto-save interval (default: 60s)
  maxMessagesBeforeCompact: number; // Trigger compaction at this count
  extractMemoriesOnEnd: boolean;    // Extract memories when session ends
  persistToViking: boolean;         // Use OpenViking for persistence
  fallbackToLocal: boolean;         // Fall back to localStorage
  maxSessionHistory: number;        // Max sessions to keep in history
  sessionTimeoutMs: number;         // Session timeout (default: 30min)
}

export interface SessionSummary {
  id: string;
  agentId: string;
  startedAt: string;
  endedAt: string;
  messageCount: number;
  topicsDiscussed: string[];
  memoriesExtracted: number;
  compacted: boolean;
}

export interface PersistenceResult {
  saved: boolean;
  sessionId: string;
  messageCount: number;
  extractedMemories: number;
  compacted: boolean;
  error?: string;
}

// === Default Config ===

export const DEFAULT_SESSION_CONFIG: SessionPersistenceConfig = {
  enabled: true,
  autoSaveIntervalMs: 60000,       // 1 minute
  maxMessagesBeforeCompact: 100,   // Compact after 100 messages
  extractMemoriesOnEnd: true,
  persistToViking: true,
  fallbackToLocal: true,
  maxSessionHistory: 50,
  sessionTimeoutMs: 1800000,       // 30 minutes
};

// === Storage Keys ===

const SESSION_STORAGE_KEY = 'zclaw-sessions';
const CURRENT_SESSION_KEY = 'zclaw-current-session';

// === Session Persistence Service ===

export class SessionPersistenceService {
  private config: SessionPersistenceConfig;
  private currentSession: SessionState | null = null;
  private vikingClient: VikingHttpClient | null = null;
  private autoSaveTimer: ReturnType<typeof setInterval> | null = null;
  private sessionHistory: SessionSummary[] = [];

  constructor(config?: Partial<SessionPersistenceConfig>) {
    this.config = { ...DEFAULT_SESSION_CONFIG, ...config };
    this.loadSessionHistory();
    this.initializeVikingClient();
  }

  private async initializeVikingClient(): Promise<void> {
    try {
      this.vikingClient = getVikingClient();
    } catch (error) {
      console.warn('[SessionPersistence] Viking client initialization failed:', error);
    }
  }

  // === Session Lifecycle ===

  /**
   * Start a new session.
   */
  startSession(agentId: string, metadata?: Record<string, unknown>): SessionState {
    // End any existing session first
    if (this.currentSession && this.currentSession.status === 'active') {
      this.endSession();
    }

    const sessionId = `session_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`;

    this.currentSession = {
      id: sessionId,
      agentId,
      startedAt: new Date().toISOString(),
      lastActivityAt: new Date().toISOString(),
      messageCount: 0,
      status: 'active',
      messages: [],
      metadata: metadata || {},
    };

    this.saveCurrentSession();
    this.startAutoSave();

    console.log(`[SessionPersistence] Started session: ${sessionId}`);
    return this.currentSession;
  }

  /**
   * Add a message to the current session.
   */
  addMessage(message: Omit<SessionMessage, 'id' | 'timestamp'>): SessionMessage | null {
    if (!this.currentSession || this.currentSession.status !== 'active') {
      console.warn('[SessionPersistence] No active session');
      return null;
    }

    const fullMessage: SessionMessage = {
      id: `msg_${Date.now()}_${Math.random().toString(36).slice(2, 6)}`,
      ...message,
      timestamp: new Date().toISOString(),
    };

    this.currentSession.messages.push(fullMessage);
    this.currentSession.messageCount++;
    this.currentSession.lastActivityAt = fullMessage.timestamp;

    // Check if compaction is needed
    if (this.currentSession.messageCount >= this.config.maxMessagesBeforeCompact) {
      this.compactSession();
    }

    return fullMessage;
  }

  /**
   * Pause the current session.
   */
  pauseSession(): void {
    if (!this.currentSession) return;

    this.currentSession.status = 'paused';
    this.stopAutoSave();
    this.saveCurrentSession();

    console.log(`[SessionPersistence] Paused session: ${this.currentSession.id}`);
  }

  /**
   * Resume a paused session.
   */
  resumeSession(): SessionState | null {
    if (!this.currentSession || this.currentSession.status !== 'paused') {
      return this.currentSession;
    }

    this.currentSession.status = 'active';
    this.currentSession.lastActivityAt = new Date().toISOString();
    this.startAutoSave();
    this.saveCurrentSession();

    console.log(`[SessionPersistence] Resumed session: ${this.currentSession.id}`);
    return this.currentSession;
  }

  /**
   * End the current session and extract memories.
   */
  async endSession(): Promise<PersistenceResult> {
    if (!this.currentSession) {
      return {
        saved: false,
        sessionId: '',
        messageCount: 0,
        extractedMemories: 0,
        compacted: false,
        error: 'No active session',
      };
    }

    const session = this.currentSession;
    session.status = 'ended';
    this.stopAutoSave();

    let extractedMemories = 0;
    let compacted = false;

    try {
      // Extract memories from the session
      if (this.config.extractMemoriesOnEnd && session.messageCount >= 4) {
        extractedMemories = await this.extractMemories(session);
      }

      // Persist to OpenViking if available
      if (this.config.persistToViking && this.vikingClient) {
        await this.persistToViking(session);
      }

      // Save to local storage
      this.saveToLocalStorage(session);

      // Add to history
      this.addToHistory(session, extractedMemories, compacted);

      console.log(`[SessionPersistence] Ended session: ${session.id}, extracted ${extractedMemories} memories`);

      return {
        saved: true,
        sessionId: session.id,
        messageCount: session.messageCount,
        extractedMemories,
        compacted,
      };
    } catch (error) {
      console.error('[SessionPersistence] Error ending session:', error);
      return {
        saved: false,
        sessionId: session.id,
        messageCount: session.messageCount,
        extractedMemories: 0,
        compacted: false,
        error: String(error),
      };
    } finally {
      this.clearCurrentSession();
    }
  }

  // === Memory Extraction ===

  private async extractMemories(session: SessionState): Promise<number> {
    const extractor = getMemoryExtractor();

    // Check if we can auto-extract
    const { canProceed } = canAutoExecute('memory_save', 5);

    if (!canProceed) {
      console.log('[SessionPersistence] Memory extraction requires approval');
      return 0;
    }

    try {
      const messages = session.messages.map(m => ({
        role: m.role,
        content: m.content,
      }));

      const result = await extractor.extractFromConversation(
        messages,
        session.agentId,
        session.id
      );

      return result.saved;
    } catch (error) {
      console.error('[SessionPersistence] Memory extraction failed:', error);
      return 0;
    }
  }

  // === Session Compaction ===

  private async compactSession(): Promise<void> {
    if (!this.currentSession || !this.vikingClient) return;

    try {
      const messages = this.currentSession.messages.map(m => ({
        role: m.role,
        content: m.content,
      }));

      // Use OpenViking to compact the session
      const summary = await this.vikingClient.compactSession(messages);

      // Keep recent messages, replace older ones with summary
      const recentMessages = this.currentSession.messages.slice(-20);

      // Create a summary message
      const summaryMessage: SessionMessage = {
        id: `summary_${Date.now()}`,
        role: 'system',
        content: `[会话摘要]\n${summary}`,
        timestamp: new Date().toISOString(),
        metadata: { type: 'compaction-summary' },
      };

      this.currentSession.messages = [summaryMessage, ...recentMessages];
      this.currentSession.messageCount = this.currentSession.messages.length;

      console.log(`[SessionPersistence] Compacted session: ${this.currentSession.id}`);
    } catch (error) {
      console.error('[SessionPersistence] Compaction failed:', error);
    }
  }

  // === Persistence ===

  private async persistToViking(session: SessionState): Promise<void> {
    if (!this.vikingClient) return;

    try {
      const sessionContent = session.messages
        .map(m => `[${m.role}]: ${m.content}`)
        .join('\n\n');

      await this.vikingClient.addResource(
        `viking://sessions/${session.agentId}/${session.id}`,
        sessionContent,
        {
          metadata: {
            startedAt: session.startedAt,
            endedAt: new Date().toISOString(),
            messageCount: String(session.messageCount || 0),
            agentId: session.agentId || 'default',
          },
          wait: false,
        }
      );
    } catch (error) {
      console.error('[SessionPersistence] Viking persistence failed:', error);
      if (!this.config.fallbackToLocal) {
        throw error;
      }
    }
  }

  private saveToLocalStorage(session: SessionState): void {
    try {
      localStorage.setItem(
        `${SESSION_STORAGE_KEY}/${session.id}`,
        JSON.stringify(session)
      );
    } catch (error) {
      console.error('[SessionPersistence] Local storage failed:', error);
    }
  }

  private saveCurrentSession(): void {
    if (!this.currentSession) return;

    try {
      localStorage.setItem(CURRENT_SESSION_KEY, JSON.stringify(this.currentSession));
    } catch (error) {
      console.error('[SessionPersistence] Failed to save current session:', error);
    }
  }

  private loadCurrentSession(): SessionState | null {
    try {
      const raw = localStorage.getItem(CURRENT_SESSION_KEY);
      if (raw) {
        return JSON.parse(raw);
      }
    } catch (error) {
      console.error('[SessionPersistence] Failed to load current session:', error);
    }
    return null;
  }

  private clearCurrentSession(): void {
    this.currentSession = null;
    try {
      localStorage.removeItem(CURRENT_SESSION_KEY);
    } catch {
      // Ignore
    }
  }

  // === Auto-save ===

  private startAutoSave(): void {
    if (this.autoSaveTimer) {
      clearInterval(this.autoSaveTimer);
    }

    this.autoSaveTimer = setInterval(() => {
      if (this.currentSession && this.currentSession.status === 'active') {
        this.saveCurrentSession();
      }
    }, this.config.autoSaveIntervalMs);
  }

  private stopAutoSave(): void {
    if (this.autoSaveTimer) {
      clearInterval(this.autoSaveTimer);
      this.autoSaveTimer = null;
    }
  }

  // === Session History ===

  private loadSessionHistory(): void {
    try {
      const raw = localStorage.getItem(SESSION_STORAGE_KEY);
      if (raw) {
        this.sessionHistory = JSON.parse(raw);
      }
    } catch {
      this.sessionHistory = [];
    }
  }

  private saveSessionHistory(): void {
    try {
      localStorage.setItem(SESSION_STORAGE_KEY, JSON.stringify(this.sessionHistory));
    } catch (error) {
      console.error('[SessionPersistence] Failed to save session history:', error);
    }
  }

  private addToHistory(session: SessionState, extractedMemories: number, compacted: boolean): void {
    const summary: SessionSummary = {
      id: session.id,
      agentId: session.agentId,
      startedAt: session.startedAt,
      endedAt: new Date().toISOString(),
      messageCount: session.messageCount,
      topicsDiscussed: this.extractTopics(session),
      memoriesExtracted: extractedMemories,
      compacted,
    };

    this.sessionHistory.unshift(summary);

    // Trim to max size
    if (this.sessionHistory.length > this.config.maxSessionHistory) {
      this.sessionHistory = this.sessionHistory.slice(0, this.config.maxSessionHistory);
    }

    this.saveSessionHistory();
  }

  private extractTopics(session: SessionState): string[] {
    // Simple topic extraction from user messages
    const userMessages = session.messages
      .filter(m => m.role === 'user')
      .map(m => m.content);

    // Look for common patterns
    const topics: string[] = [];
    const patterns = [
      /(?:帮我|请|能否)(.{2,10})/g,
      /(?:问题|bug|错误|报错)(.{2,20})/g,
      /(?:实现|添加|开发)(.{2,15})/g,
    ];

    for (const msg of userMessages) {
      for (const pattern of patterns) {
        const matches = msg.matchAll(pattern);
        for (const match of matches) {
          if (match[1] && match[1].length > 2) {
            topics.push(match[1].trim());
          }
        }
      }
    }

    return [...new Set(topics)].slice(0, 10);
  }

  // === Public API ===

  /**
   * Get the current session.
   */
  getCurrentSession(): SessionState | null {
    return this.currentSession;
  }

  /**
   * Get session history.
   */
  getSessionHistory(limit: number = 20): SessionSummary[] {
    return this.sessionHistory.slice(0, limit);
  }

  /**
   * Restore a previous session.
   */
  restoreSession(sessionId: string): SessionState | null {
    try {
      const raw = localStorage.getItem(`${SESSION_STORAGE_KEY}/${sessionId}`);
      if (raw) {
        const session = JSON.parse(raw) as SessionState;
        session.status = 'active';
        session.lastActivityAt = new Date().toISOString();
        this.currentSession = session;
        this.startAutoSave();
        this.saveCurrentSession();
        return session;
      }
    } catch (error) {
      console.error('[SessionPersistence] Failed to restore session:', error);
    }
    return null;
  }

  /**
   * Delete a session from history.
   */
  deleteSession(sessionId: string): boolean {
    try {
      localStorage.removeItem(`${SESSION_STORAGE_KEY}/${sessionId}`);
      this.sessionHistory = this.sessionHistory.filter(s => s.id !== sessionId);
      this.saveSessionHistory();
      return true;
    } catch {
      return false;
    }
  }

  /**
   * Get configuration.
   */
  getConfig(): SessionPersistenceConfig {
    return { ...this.config };
  }

  /**
   * Update configuration.
   */
  updateConfig(updates: Partial<SessionPersistenceConfig>): void {
    this.config = { ...this.config, ...updates };

    // Restart auto-save if interval changed
    if (updates.autoSaveIntervalMs && this.currentSession?.status === 'active') {
      this.stopAutoSave();
      this.startAutoSave();
    }
  }

  /**
   * Check if session persistence is available.
   */
  async isAvailable(): Promise<boolean> {
    if (!this.config.enabled) return false;

    if (this.config.persistToViking && this.vikingClient) {
      return this.vikingClient.isAvailable();
    }

    return this.config.fallbackToLocal;
  }

  /**
   * Recover from crash - restore last session if valid.
   */
  recoverFromCrash(): SessionState | null {
    const lastSession = this.loadCurrentSession();

    if (!lastSession) return null;

    // Check if session timed out
    const lastActivity = new Date(lastSession.lastActivityAt).getTime();
    const now = Date.now();

    if (now - lastActivity > this.config.sessionTimeoutMs) {
      console.log('[SessionPersistence] Last session timed out, not recovering');
      this.clearCurrentSession();
      return null;
    }

    // Recover the session
    lastSession.status = 'active';
    lastSession.lastActivityAt = new Date().toISOString();
    this.currentSession = lastSession;
    this.startAutoSave();
    this.saveCurrentSession();

    console.log(`[SessionPersistence] Recovered session: ${lastSession.id}`);
    return lastSession;
  }
}

// === Singleton ===

let _instance: SessionPersistenceService | null = null;

export function getSessionPersistence(config?: Partial<SessionPersistenceConfig>): SessionPersistenceService {
  if (!_instance || config) {
    _instance = new SessionPersistenceService(config);
  }
  return _instance;
}

export function resetSessionPersistence(): void {
  _instance = null;
}

// === Helper Functions ===

/**
 * Quick start a session.
 */
export function startSession(agentId: string, metadata?: Record<string, unknown>): SessionState {
  return getSessionPersistence().startSession(agentId, metadata);
}

/**
 * Quick add a message.
 */
export function addSessionMessage(message: Omit<SessionMessage, 'id' | 'timestamp'>): SessionMessage | null {
  return getSessionPersistence().addMessage(message);
}

/**
 * Quick end session.
 */
export async function endCurrentSession(): Promise<PersistenceResult> {
  return getSessionPersistence().endSession();
}

/**
 * Get current session.
 */
export function getCurrentSession(): SessionState | null {
  return getSessionPersistence().getCurrentSession();
}