import { defineStore } from 'pinia'
import { ref } from 'vue'
import { api } from '@/services/api'

export interface ChatMessage {
  id: string
  role: 'USER' | 'ASSISTANT'
  content: string
  sources: Array<{ bookTitle: string; page: number | null }>
  createdAt: string
}

export interface ChatSession {
  sessionId: string
  topicId: string | null
  createdAt: string
}

export const useChatStore = defineStore('chat', () => {
  const session = ref<ChatSession | null>(null)
  const messages = ref<ChatMessage[]>([])
  const loading = ref(false)
  const sending = ref(false)
  const error = ref<string | null>(null)

  async function createSession(topicId?: string): Promise<boolean> {
    loading.value = true
    error.value = null
    try {
      const body = topicId ? { topicId } : {}
      const response = await api.post<ChatSession>('/chat/sessions', body)
      session.value = response.data
      messages.value = []
      return true
    } catch (err: any) {
      error.value = err.message
      return false
    } finally {
      loading.value = false
    }
  }

  async function loadMessages(): Promise<void> {
    if (!session.value) return
    loading.value = true
    error.value = null
    try {
      const response = await api.get<ChatMessage[]>(
        `/chat/sessions/${session.value.sessionId}/messages`
      )
      messages.value = response.data
    } catch (err: any) {
      error.value = err.message
    } finally {
      loading.value = false
    }
  }

  async function sendMessage(content: string): Promise<boolean> {
    if (!session.value) return false
    sending.value = true
    error.value = null

    // Optimistically add user message
    const tempUserMsg: ChatMessage = {
      id: crypto.randomUUID(),
      role: 'USER',
      content,
      sources: [],
      createdAt: new Date().toISOString()
    }
    messages.value.push(tempUserMsg)

    try {
      const response = await api.post<ChatMessage>(
        `/chat/sessions/${session.value.sessionId}/messages`,
        { content }
      )
      // Replace temp message & add assistant response
      messages.value = messages.value.filter((m) => m.id !== tempUserMsg.id)
      // Reload full conversation to stay in sync
      await loadMessages()
      return true
    } catch (err: any) {
      // Remove optimistic message on failure
      messages.value = messages.value.filter((m) => m.id !== tempUserMsg.id)
      error.value = err.message
      return false
    } finally {
      sending.value = false
    }
  }

  async function deleteSession(): Promise<boolean> {
    if (!session.value) return false
    loading.value = true
    error.value = null
    try {
      await api.delete(`/chat/sessions/${session.value.sessionId}`)
      session.value = null
      messages.value = []
      return true
    } catch (err: any) {
      error.value = err.message
      return false
    } finally {
      loading.value = false
    }
  }

  return {
    session,
    messages,
    loading,
    sending,
    error,
    createSession,
    loadMessages,
    sendMessage,
    deleteSession
  }
})