import { computed, ref, watch } from 'vue'

import {
  buildReportAnalyticsQuery,
  getReportAnalytics,
  getReportOptions,
  type ReportAnalyticsDataset,
  type ReportOptions,
} from '@/api/workbench/report-analytics'
import { toUserMessage } from '@/utils/api-response'

import { resolveDateWindow } from './aggregate'
import { reportFilter } from './filter-store'

const dataset = ref<ReportAnalyticsDataset | null>(null)
const options = ref<ReportOptions | null>(null)
const loading = ref(false)
const errorMessage = ref('')
const optionsError = ref('')

let requestSequence = 0
let pendingOptions: Promise<void> | null = null
let filterWatcherInstalled = false
let debounceTimer: ReturnType<typeof setTimeout> | null = null

export function loadReportOptions(): Promise<void> {
  if (options.value) return Promise.resolve()
  pendingOptions ??= (async () => {
    optionsError.value = ''
    try {
      options.value = await getReportOptions()
    } catch (error) {
      optionsError.value = toUserMessage(error, '报表筛选项加载失败')
    } finally {
      pendingOptions = null
    }
  })()
  return pendingOptions
}

export async function loadReportDataset(): Promise<void> {
  const sequence = ++requestSequence
  dataset.value = null
  const dateWindow = resolveDateWindow(reportFilter)
  if (!dateWindow) {
    errorMessage.value = ''
    loading.value = false
    return
  }

  loading.value = true
  errorMessage.value = ''
  try {
    const query = buildReportAnalyticsQuery(reportFilter, dateWindow)
    const result = await getReportAnalytics(query)
    if (sequence === requestSequence) dataset.value = result
  } catch (error) {
    if (sequence === requestSequence) errorMessage.value = toUserMessage(error, '报表数据加载失败')
  } finally {
    if (sequence === requestSequence) loading.value = false
  }
}

function installFilterWatcher() {
  if (filterWatcherInstalled) return
  filterWatcherInstalled = true
  watch(
    () => [
      reportFilter.dateRange,
      reportFilter.customFrom,
      reportFilter.customTo,
      reportFilter.campus,
      reportFilter.department,
      reportFilter.category,
      reportFilter.method,
    ],
    () => {
      if (debounceTimer) clearTimeout(debounceTimer)
      debounceTimer = setTimeout(() => void loadReportDataset(), 250)
    },
  )
}

export function resetReportDataset(): void {
  dataset.value = null
  requestSequence++
  if (debounceTimer) clearTimeout(debounceTimer)
}

export function useReportDataset() {
  installFilterWatcher()
  const window = computed(() => resolveDateWindow(reportFilter))
  const available = computed(() => dataset.value !== null)
  const generatedAt = computed(() => dataset.value?.generatedAt ?? '')
  const customRangeIncomplete = computed(
    () =>
      reportFilter.dateRange === 'custom' && (!reportFilter.customFrom || !reportFilter.customTo),
  )

  return {
    dataset,
    options,
    window,
    available,
    generatedAt,
    loading,
    errorMessage,
    optionsError,
    customRangeIncomplete,
  }
}