import { ref, computed } from 'vue'

const userToken = ref(null)
const refreshToken = ref(null)
const userProfile = ref(null)
const userRoles = ref([])
const isAuthenticated = ref(false)
const isInitialized = ref(false)

let sessionPollTimer = null

const extractRolesFromToken = (token) => {
  if (!token) return []
  try {
    const payloadBase64 = token.split('.')[1]
    const base64 = payloadBase64.replace(/-/g, '+').replace(/_/g, '/')
    const jsonPayload = decodeURIComponent(
      atob(base64)
        .split('')
        .map(c => '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2))
        .join('')
    )
    const payload = JSON.parse(jsonPayload)

    const realmRoles = payload?.realm_access?.roles || []
    const clientRoles = Object.values(payload?.resource_access || {})
      .flatMap(client => client.roles || [])
    const directRoles = payload?.roles || []

    return [...realmRoles, ...clientRoles, ...directRoles].map(r => String(r).toLowerCase())
  } catch (e) {
    console.warn('Failed to parse roles from token:', e)
    return []
  }
}

const getStoredRefreshToken = () => {
  if (refreshToken.value) {
    return refreshToken.value
  }

  if (import.meta.client) {
    return localStorage.getItem('keycloak_refresh_token')
  }

  return null
}

export const useAuth = () => {
  const fetchUserProfile = async () => {
    if (!userToken.value) return
    try {
      const profile = await $fetch('/api/user/profile', {
        headers: {
          Authorization: `Bearer ${userToken.value}`
        }
      })
      userProfile.value = profile
    } catch (err) {
      console.error('Failed to fetch user profile:', err)
    }
  }

  const setSession = (data) => {
    userToken.value = data.access_token
    userRoles.value = extractRolesFromToken(data.access_token)

    if (data.refresh_token) {
      refreshToken.value = data.refresh_token
      if (import.meta.client) {
        localStorage.setItem('keycloak_refresh_token', data.refresh_token)
      }
    }
    isAuthenticated.value = true
  }

  const clearSession = () => {
    stopLiveSessionPolling()
    userToken.value = null
    refreshToken.value = null
    userProfile.value = null
    userRoles.value = []
    isAuthenticated.value = false
    if (import.meta.client) {
      localStorage.removeItem('keycloak_refresh_token')
    }
  }

  const exchangeCodeForToken = async (code) => {
    try {
      const data = await $fetch('/api/auth/token', {
        method: 'POST',
        body: {
          code,
          redirectUri: `${window.location.origin}/oauth`
        }
      })

      setSession(data)
      window.history.replaceState({}, document.title, window.location.pathname)
      
      await fetchUserProfile()
      startLiveSessionPolling()

      return { success: true, isFirstLogin: data.isFirstLogin }
    } catch (error) {
      console.error('Code exchange failed:', error)
      clearSession()
      return { success: false, isFirstLogin: false }
    } finally {
      isInitialized.value = true
    }
  }

  const silentRefresh = async () => {
    const storedRefreshToken = getStoredRefreshToken()

    if (!storedRefreshToken) {
      clearSession()
      isInitialized.value = true
      return false
    }

    try {
      const data = await $fetch('/api/auth/refresh', {
        method: 'POST',
        body: { refreshToken: storedRefreshToken }
      })

      setSession(data)
      await fetchUserProfile()
      startLiveSessionPolling()
      return true
    } catch (error) {
      console.warn('Silent refresh failed:', error)
      clearSession()
      return false
    } finally {
      isInitialized.value = true
    }
  }

  const verifySession = async () => {
    if (!userToken.value) {
      return await silentRefresh()
    }

    try {
      const res = await $fetch('/api/auth/check-session', {
        method: 'POST',
        body: { token: userToken.value }
      })

      if (res.active) {
        isAuthenticated.value = true
        
        if (!userProfile.value) {
          await fetchUserProfile()
        }

        return true
      } else {
        return await silentRefresh()
      }
    } catch (e) {
      return await silentRefresh()
    } finally {
      isInitialized.value = true
    }
  }

  const initializeAuth = async ({ code, redirectTo = '/oauth', replace = false } = {}) => {
    if (code) {
      const result = await exchangeCodeForToken(code)
      if (!result.success) {
        await navigateTo(redirectTo, { replace })
        return false
      }

      if (result.isFirstLogin) {
        await navigateTo('/welcome', { replace: true })
        return true
      }

      return true
    }

    if (isAuthenticated.value) {
      const valid = await verifySession()
      if (!valid) {
        await navigateTo(redirectTo, { replace })
        return false
      }
      return true
    }

    const success = await silentRefresh()
    if (!success) {
      await navigateTo(redirectTo, { replace })
      return false
    }

    return true
  }

  const startLiveSessionPolling = () => {
    if (import.meta.server) return
    stopLiveSessionPolling()

    sessionPollTimer = setInterval(async () => {
      if (isAuthenticated.value) {
        const valid = await verifySession()
        if (!valid) {
          handleLocalLogout()
        }
      }
    }, 5000)
  }

  const stopLiveSessionPolling = () => {
    if (sessionPollTimer) {
      clearInterval(sessionPollTimer)
      sessionPollTimer = null
    }
  }

  const handleLocalLogout = () => {
    clearSession()
    isInitialized.value = true
    navigateTo('/oauth')
  }

  const logout = async () => {
    try {
      await $fetch('/api/auth/logout', {
        method: 'POST',
        body: { refreshToken: refreshToken.value }
      })
    } catch (e) {
      console.warn('Server logout failed:', e)
    } finally {
      handleLocalLogout()
    }
  }

  return {
    userToken,
    token: userToken, 
    userProfile,
    userRoles,
    isAuthenticated,
    isInitialized,
    exchangeCodeForToken,
    initializeAuth,
    silentRefresh,
    verifySession,
    fetchUserProfile,
    logout
  }
}