import { ChatSession, Message } from '@/types/chat'

const STORAGE_KEYS = {
  sessions: 'edge-llm-sessions',
  currentSession: 'edge-llm-current-session'
}

function generateId(): string {
  return Math.random().toString(36).substring(2) + Date.now().toString(36)
}

function generateMessageId(): string {
  return generateId()
}

class ChatStorageManager {
  getAllSessions(): ChatSession[] {
    const stored = localStorage.getItem(STORAGE_KEYS.sessions)
    return stored ? JSON.parse(stored) : []
  }

  getSession(sessionId: string): ChatSession | null {
    const sessions = this.getAllSessions()
    return sessions.find(s => s.id === sessionId) || null
  }

  createSession(title?: string, model?: string, systemPrompt?: string): ChatSession {
    const newSession: ChatSession = {
      id: generateId(),
      title: title || `New Chat ${new Date().toLocaleString()}`,
      messages: [],
      model,
      systemPrompt,
      createdAt: Date.now(),
      updatedAt: Date.now()
    }

    const sessions = this.getAllSessions()
    sessions.unshift(newSession)
    localStorage.setItem(STORAGE_KEYS.sessions, JSON.stringify(sessions))
    
    return newSession
  }

  updateSession(sessionId: string, updates: Partial<ChatSession>): void {
    const sessions = this.getAllSessions()
    const sessionIndex = sessions.findIndex(s => s.id === sessionId)
    
    if (sessionIndex !== -1) {
      sessions[sessionIndex] = {
        ...sessions[sessionIndex],
        ...updates,
        updatedAt: Date.now()
      }
      localStorage.setItem(STORAGE_KEYS.sessions, JSON.stringify(sessions))
    }
  }

  deleteSession(sessionId: string): void {
    const sessions = this.getAllSessions()
    const filtered = sessions.filter(s => s.id !== sessionId)
    localStorage.setItem(STORAGE_KEYS.sessions, JSON.stringify(filtered))
    
    if (this.getCurrentSessionId() === sessionId) {
      localStorage.removeItem(STORAGE_KEYS.currentSession)
    }
  }

  addMessageToSession(sessionId: string, message: Omit<Message, 'id' | 'timestamp'>): void {
    const sessions = this.getAllSessions()
    const sessionIndex = sessions.findIndex(s => s.id === sessionId)
    
    if (sessionIndex !== -1) {
      const newMessage: Message = {
        ...message,
        id: generateMessageId(),
        timestamp: Date.now()
      }
      
      sessions[sessionIndex].messages.push(newMessage)
      sessions[sessionIndex].updatedAt = Date.now()
      localStorage.setItem(STORAGE_KEYS.sessions, JSON.stringify(sessions))
    }
  }

  getCurrentSessionId(): string | null {
    return localStorage.getItem(STORAGE_KEYS.currentSession)
  }

  getCurrentSession(): ChatSession | null {
    const currentId = this.getCurrentSessionId()
    return currentId ? this.getSession(currentId) : null
  }

  setCurrentSession(sessionId: string): void {
    localStorage.setItem(STORAGE_KEYS.currentSession, sessionId)
  }

  clear(): void {
    localStorage.removeItem(STORAGE_KEYS.sessions)
    localStorage.removeItem(STORAGE_KEYS.currentSession)
  }
}

export const chatStorage = new ChatStorageManager()