import { 
  signInWithEmailAndPassword, 
  signInWithPopup, 
  GoogleAuthProvider,
  signOut as firebaseSignOut,
  onAuthStateChanged,
  getAuth
} from 'firebase/auth'
import { getApps, initializeApp } from 'firebase/app'
import type { User } from 'firebase/auth'

export const useAuth = () => {
  const user = ref<User | null>(null)
  const isLoading = ref(true)
  const error = ref<string | null>(null)
  
  const config = useRuntimeConfig()

  // Initialize Firebase if not already initialized
  const initializeFirebase = () => {
    if (process.client && getApps().length === 0) {
      const firebaseConfig = {
        apiKey: config.public.firebaseApiKey,
        authDomain: config.public.firebaseAuthDomain,
        projectId: config.public.firebaseProjectId,
        storageBucket: config.public.firebaseStorageBucket,
        messagingSenderId: config.public.firebaseMessagingSenderId,
        appId: config.public.firebaseAppId
      }
      initializeApp(firebaseConfig)
    }
  }

  // Get auth instance directly
  const getAuthInstance = () => {
    if (process.client) {
      initializeFirebase()
      return getAuth()
    }
    return null
  }

  // Initialize auth state listener
  const initAuth = () => {
    if (process.client) {
      try {
        const auth = getAuthInstance()
        if (auth) {
          onAuthStateChanged(auth, (firebaseUser) => {
            user.value = firebaseUser
            isLoading.value = false
          })
        }
      } catch (err) {
        console.error('Failed to initialize auth:', err)
        isLoading.value = false
      }
    }
  }

  // Sign in with email and password
  const signInWithEmail = async (email: string, password: string) => {
    try {
      error.value = null
      isLoading.value = true
      
      const auth = getAuthInstance()
      if (!auth) {
        throw new Error('Firebase not initialized')
      }
      
      const userCredential = await signInWithEmailAndPassword(auth, email, password)
      const idToken = await userCredential.user.getIdToken()
      
      // Send token to backend
      await authenticateWithBackend(idToken)
      
      return userCredential.user
    } catch (err: any) {
      error.value = err.message
      throw err
    } finally {
      isLoading.value = false
    }
  }

  // Sign in with Google
  const signInWithGoogle = async () => {
    try {
      error.value = null
      isLoading.value = true
      
      const auth = getAuthInstance()
      if (!auth) {
        throw new Error('Firebase not initialized')
      }
      
      const provider = new GoogleAuthProvider()
      const userCredential = await signInWithPopup(auth, provider)
      const idToken = await userCredential.user.getIdToken()
      
      // Send token to backend
      await authenticateWithBackend(idToken)
      
      return userCredential.user
    } catch (err: any) {
      error.value = err.message
      throw err
    } finally {
      isLoading.value = false
    }
  }

  // Authenticate with backend
  const authenticateWithBackend = async (idToken: string) => {
    try {
      const response = await $fetch('/auth/login', {
        baseURL: config.public.backendUrl,
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: {
          idToken
        }
      })
      
      return response
    } catch (err) {
      console.error('Backend authentication failed:', err)
      throw err
    }
  }

  // Sign out
  const signOut = async () => {
    try {
      const auth = getAuthInstance()
      if (!auth) {
        throw new Error('Firebase not initialized')
      }
      
      await firebaseSignOut(auth)
      user.value = null
    } catch (err: any) {
      error.value = err.message
      throw err
    }
  }

  // Get current user's ID token
  const getIdToken = async () => {
    if (!user.value) return null
    return await user.value.getIdToken()
  }

  return {
    user: readonly(user),
    isLoading: readonly(isLoading),
    error: readonly(error),
    initAuth,
    signInWithEmail,
    signInWithGoogle,
    signOut,
    getIdToken
  }
}