<template>
  <AuthLayout>
    <div class="space-y-6">
      <div class="text-center">
        <h2 class="text-2xl font-bold text-gray-900 dark:text-white">
          {{ t('auth.oidc.callbackTitle', { providerName }) }}
        </h2>
        <p class="mt-2 text-sm text-gray-500 dark:text-dark-400">
          {{
            isProcessing
              ? t('auth.oidc.callbackProcessing', { providerName })
              : t('auth.oidc.callbackHint')
          }}
        </p>
      </div>

      <transition name="fade">
        <div v-if="needsInvitation || needsAdoptionConfirmation" class="space-y-4">
          <div
            v-if="adoptionRequired && (suggestedDisplayName || suggestedAvatarUrl)"
            class="rounded-xl border border-gray-200 bg-gray-50 p-4 dark:border-dark-600 dark:bg-dark-800/60"
          >
            <div class="space-y-3">
              <div class="space-y-1">
                <p class="text-sm font-medium text-gray-900 dark:text-white">
                  Use {{ providerName }} profile details
                </p>
                <p class="text-xs text-gray-500 dark:text-dark-400">
                  Choose whether to apply the nickname or avatar from {{ providerName }} to this account.
                </p>
              </div>

              <label
                v-if="suggestedDisplayName"
                class="flex items-start gap-3 rounded-lg border border-gray-200 bg-white p-3 text-sm dark:border-dark-600 dark:bg-dark-900/50"
              >
                <input v-model="adoptDisplayName" type="checkbox" class="mt-1 h-4 w-4" />
                <span class="space-y-1">
                  <span class="block font-medium text-gray-900 dark:text-white">
                    Use display name
                  </span>
                  <span class="block text-gray-500 dark:text-dark-400">
                    {{ suggestedDisplayName }}
                  </span>
                </span>
              </label>

              <label
                v-if="suggestedAvatarUrl"
                class="flex items-start gap-3 rounded-lg border border-gray-200 bg-white p-3 text-sm dark:border-dark-600 dark:bg-dark-900/50"
              >
                <input v-model="adoptAvatar" type="checkbox" class="mt-1 h-4 w-4" />
                <img
                  :src="suggestedAvatarUrl"
                  :alt="`${providerName} avatar`"
                  class="h-10 w-10 rounded-full border border-gray-200 object-cover dark:border-dark-600"
                />
                <span class="space-y-1">
                  <span class="block font-medium text-gray-900 dark:text-white">
                    Use avatar
                  </span>
                  <span class="block break-all text-gray-500 dark:text-dark-400">
                    {{ suggestedAvatarUrl }}
                  </span>
                </span>
              </label>
            </div>
          </div>

          <template v-if="needsInvitation">
            <p class="text-sm text-gray-700 dark:text-gray-300">
              {{ t('auth.oidc.invitationRequired', { providerName }) }}
            </p>
            <div>
              <input
                v-model="invitationCode"
                type="text"
                class="input w-full"
                :placeholder="t('auth.invitationCodePlaceholder')"
                :disabled="isSubmitting"
                @keyup.enter="handleSubmitInvitation"
              />
            </div>
            <transition name="fade">
              <p v-if="invitationError" class="text-sm text-red-600 dark:text-red-400">
                {{ invitationError }}
              </p>
            </transition>
            <button
              class="btn btn-primary w-full"
              :disabled="isSubmitting || !invitationCode.trim()"
              @click="handleSubmitInvitation"
            >
              {{
                isSubmitting
                  ? t('auth.oidc.completing')
                  : t('auth.oidc.completeRegistration')
              }}
            </button>

            <div
              class="rounded-xl border border-gray-200 bg-gray-50 p-4 dark:border-dark-600 dark:bg-dark-800/60"
            >
              <div class="space-y-3">
                <div class="space-y-1">
                  <p class="text-sm font-medium text-gray-900 dark:text-white">
                    {{ t('auth.alreadyHaveAccount') }}
                  </p>
                  <p class="text-xs text-gray-500 dark:text-dark-400">
                    Sign in to an existing account, then bind this WeChat identity to it.
                  </p>
                </div>

                <input
                  v-model="existingAccountEmail"
                  data-testid="existing-account-email"
                  type="email"
                  class="input w-full"
                  :placeholder="t('auth.emailPlaceholder')"
                  :disabled="isSubmitting"
                />

                <button
                  data-testid="existing-account-submit"
                  type="button"
                  class="btn btn-secondary w-full"
                  :disabled="isSubmitting"
                  @click="handleExistingAccountBinding"
                >
                  {{ t('auth.signIn') }}
                </button>
              </div>
            </div>
          </template>

          <template v-else-if="needsAdoptionConfirmation">
            <p class="text-sm text-gray-700 dark:text-gray-300">
              Review the {{ providerName }} profile details before continuing.
            </p>
            <button class="btn btn-primary w-full" :disabled="isSubmitting" @click="handleContinueLogin">
              {{ isSubmitting ? t('common.processing') : 'Continue' }}
            </button>
          </template>
        </div>
      </transition>

      <transition name="fade">
        <div
          v-if="errorMessage"
          class="rounded-xl border border-red-200 bg-red-50 p-4 dark:border-red-800/50 dark:bg-red-900/20"
        >
          <div class="flex items-start gap-3">
            <div class="flex-shrink-0">
              <Icon name="exclamationCircle" size="md" class="text-red-500" />
            </div>
            <div class="space-y-2">
              <p class="text-sm text-red-700 dark:text-red-400">
                {{ errorMessage }}
              </p>
              <router-link to="/login" class="btn btn-primary">
                {{ t('auth.oidc.backToLogin') }}
              </router-link>
            </div>
          </div>
        </div>
      </transition>
    </div>
  </AuthLayout>
</template>

<script setup lang="ts">
import { onMounted, ref } from 'vue'
import { useRoute, useRouter } from 'vue-router'
import { useI18n } from 'vue-i18n'
import { AuthLayout } from '@/components/layout'
import Icon from '@/components/icons/Icon.vue'
import { useAuthStore, useAppStore } from '@/stores'
import {
  completeWeChatOAuthRegistration,
  exchangePendingOAuthCompletion,
  getAuthToken,
  getOAuthCompletionKind,
  isOAuthLoginCompletion,
  prepareOAuthBindAccessTokenCookie,
  persistOAuthTokenContext,
  type OAuthAdoptionDecision,
  type PendingOAuthExchangeResponse
} from '@/api/auth'

const route = useRoute()
const router = useRouter()
const { t } = useI18n()

const authStore = useAuthStore()
const appStore = useAppStore()

const isProcessing = ref(true)
const errorMessage = ref('')
const needsInvitation = ref(false)
const invitationCode = ref('')
const isSubmitting = ref(false)
const invitationError = ref('')
const redirectTo = ref('/dashboard')
const adoptionRequired = ref(false)
const suggestedDisplayName = ref('')
const suggestedAvatarUrl = ref('')
const existingAccountEmail = ref('')
const adoptDisplayName = ref(true)
const adoptAvatar = ref(true)
const needsAdoptionConfirmation = ref(false)
const bindSuccessMessage = t('profile.authBindings.bindSuccess')

const providerName = 'WeChat'

function parseFragmentParams(): URLSearchParams {
  const raw = typeof window !== 'undefined' ? window.location.hash : ''
  const hash = raw.startsWith('#') ? raw.slice(1) : raw
  return new URLSearchParams(hash)
}

function sanitizeRedirectPath(path: string | null | undefined): string {
  if (!path) return '/dashboard'
  if (!path.startsWith('/')) return '/dashboard'
  if (path.startsWith('//')) return '/dashboard'
  if (path.includes('://')) return '/dashboard'
  if (path.includes('\n') || path.includes('\r')) return '/dashboard'
  return path
}

function resolveWeChatOAuthMode(): 'open' | 'mp' {
  if (typeof navigator === 'undefined') {
    return 'open'
  }
  return /MicroMessenger/i.test(navigator.userAgent) ? 'mp' : 'open'
}

function resolveRedirectTarget(): string {
  return sanitizeRedirectPath(
    (route.query.redirect as string | undefined) || redirectTo.value || '/dashboard'
  )
}

function resolveWeChatStartURL(intent: 'bind_current_user' | 'adopt_existing_user_by_email'): string {
  const apiBase = (import.meta.env.VITE_API_BASE_URL as string | undefined) || '/api/v1'
  const normalized = apiBase.replace(/\/$/, '')
  const params = new URLSearchParams({
    mode: resolveWeChatOAuthMode(),
    redirect: resolveRedirectTarget(),
    intent,
  })

  const email = existingAccountEmail.value.trim()
  if (email) {
    params.set('email', email)
  }

  return `${normalized}/auth/oauth/wechat/start?${params.toString()}`
}

function buildExistingAccountResumePath(): string {
  const params = new URLSearchParams({
    wechat_bind_existing: '1',
    redirect: resolveRedirectTarget(),
  })

  const email = existingAccountEmail.value.trim()
  if (email) {
    params.set('email', email)
  }

  return `/auth/wechat/callback?${params.toString()}`
}

function currentAdoptionDecision(): OAuthAdoptionDecision {
  return {
    adoptDisplayName: adoptDisplayName.value,
    adoptAvatar: adoptAvatar.value
  }
}

async function handleExistingAccountBinding() {
  if (getAuthToken()) {
    prepareOAuthBindAccessTokenCookie()
    window.location.href = resolveWeChatStartURL('bind_current_user')
    return
  }

  const params = new URLSearchParams({
    redirect: buildExistingAccountResumePath(),
  })
  const email = existingAccountEmail.value.trim()
  if (email) {
    params.set('email', email)
  }
  await router.replace(`/login?${params.toString()}`)
}

function applyAdoptionSuggestionState(completion: PendingOAuthExchangeResponse) {
  adoptionRequired.value = completion.adoption_required === true
  suggestedDisplayName.value = completion.suggested_display_name || ''
  suggestedAvatarUrl.value = completion.suggested_avatar_url || ''

  if (!suggestedDisplayName.value) {
    adoptDisplayName.value = false
  }
  if (!suggestedAvatarUrl.value) {
    adoptAvatar.value = false
  }
}

function hasSuggestedProfile(completion: PendingOAuthExchangeResponse): boolean {
  return Boolean(completion.suggested_display_name || completion.suggested_avatar_url)
}

async function finalizeCompletion(completion: PendingOAuthExchangeResponse, redirect: string) {
  if (getOAuthCompletionKind(completion) === 'bind') {
    const bindRedirect = sanitizeRedirectPath(completion.redirect || '/profile')
    appStore.showSuccess(bindSuccessMessage)
    await router.replace(bindRedirect)
    return
  }

  if (!isOAuthLoginCompletion(completion)) {
    throw new Error(t('auth.oidc.callbackMissingToken'))
  }

  persistOAuthTokenContext(completion)
  await authStore.setToken(completion.access_token)
  appStore.showSuccess(t('auth.loginSuccess'))
  await router.replace(redirect)
}

async function handleSubmitInvitation() {
  invitationError.value = ''
  if (!invitationCode.value.trim()) return

  isSubmitting.value = true
  try {
    const tokenData = await completeWeChatOAuthRegistration(
      invitationCode.value.trim(),
      currentAdoptionDecision()
    )
    persistOAuthTokenContext(tokenData)
    await authStore.setToken(tokenData.access_token)
    appStore.showSuccess(t('auth.loginSuccess'))
    await router.replace(redirectTo.value)
  } catch (e: unknown) {
    const err = e as { message?: string; response?: { data?: { message?: string } } }
    invitationError.value =
      err.response?.data?.message || err.message || t('auth.oidc.completeRegistrationFailed')
  } finally {
    isSubmitting.value = false
  }
}

async function handleContinueLogin() {
  isSubmitting.value = true
  try {
    const completion = await exchangePendingOAuthCompletion(currentAdoptionDecision())
    await finalizeCompletion(completion, redirectTo.value)
  } catch (e: unknown) {
    const err = e as { message?: string; response?: { data?: { detail?: string; message?: string } } }
    errorMessage.value =
      err.response?.data?.detail ||
      err.response?.data?.message ||
      err.message ||
      t('auth.loginFailed')
    appStore.showError(errorMessage.value)
    needsAdoptionConfirmation.value = false
  } finally {
    isSubmitting.value = false
  }
}

onMounted(async () => {
  if (typeof route.query.email === 'string') {
    existingAccountEmail.value = route.query.email
  }

  if (route.query.wechat_bind_existing === '1' && getAuthToken()) {
    prepareOAuthBindAccessTokenCookie()
    window.location.href = resolveWeChatStartURL('bind_current_user')
    return
  }

  const params = parseFragmentParams()
  const error = params.get('error')
  const errorDesc = params.get('error_description') || params.get('error_message') || ''

  if (error) {
    errorMessage.value = errorDesc || error
    appStore.showError(errorMessage.value)
    isProcessing.value = false
    return
  }

  try {
    const completion = await exchangePendingOAuthCompletion()
    const redirect = sanitizeRedirectPath(
      completion.redirect || (route.query.redirect as string | undefined) || '/dashboard'
    )
    applyAdoptionSuggestionState(completion)
    redirectTo.value = redirect

    if (completion.error === 'invitation_required') {
      needsInvitation.value = true
      isProcessing.value = false
      return
    }

    if (adoptionRequired.value && hasSuggestedProfile(completion)) {
      needsAdoptionConfirmation.value = true
      isProcessing.value = false
      return
    }

    await finalizeCompletion(completion, redirect)
  } catch (e: unknown) {
    const err = e as { message?: string; response?: { data?: { detail?: string; message?: string } } }
    errorMessage.value =
      err.response?.data?.detail ||
      err.response?.data?.message ||
      err.message ||
      t('auth.loginFailed')
    appStore.showError(errorMessage.value)
    isProcessing.value = false
  }
})
</script>

<style scoped>
.fade-enter-active,
.fade-leave-active {
  transition: all 0.3s ease;
}

.fade-enter-from,
.fade-leave-to {
  opacity: 0;
  transform: translateY(-8px);
}
</style>
