import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue'

import { useSystemState } from '../../composables/useSystemState.js'
import { useToast } from '../../composables/useToast.js'
import {
  deleteKnowledgeDocument,
  fetchKnowledgeDocument,
  fetchKnowledgeDocumentBlob,
  fetchKnowledgeLibrary,
  fetchKnowledgeOnlyOfficeConfig,
  uploadKnowledgeDocument
} from '../../services/knowledge.js'
import { loadOnlyOfficeApi } from '../../services/onlyoffice.js'
import { isManagerUser } from '../../utils/accessControl.js'
import {
  buildExcelPreviewTable,
  buildPreviewMetaLine,
  buildPreviewSecondaryMetaLine
} from './policiesPreviewFormatters.js'

function triggerFileDownload(blob, filename) {
  const url = URL.createObjectURL(blob)
const anchor = document.createElement('a')
  anchor.href = url
  anchor.download = filename
  anchor.click()
  URL.revokeObjectURL(url)
}

const ONLYOFFICE_EXTENSIONS = new Set(['docx', 'xlsx', 'pptx'])

function supportsOnlyOfficePreview(document) {
  return ONLYOFFICE_EXTENSIONS.has(String(document?.extension || '').toLowerCase())
}

export default {
  name: 'PoliciesView',
  emits: ['summary-change'],
  setup(_, { emit }) {
    const { currentUser } = useSystemState()
    const { toast } = useToast()

    const documentSearch = ref('')
    const activeFolder = ref('差旅规范')
    const folders = ref([])
    const documents = ref([])
    const selectedDocument = ref(null)
    const pageSizeOpen = ref(false)
    const currentPage = ref(1)
    const pageSize = ref(10)
    const pageSizes = [10, 20, 50]
    const loading = ref(false)
    const uploadInput = ref(null)
    const uploading = ref(false)
    const deletingId = ref('')
    const previewLoading = ref(false)
    const previewBlobUrl = ref('')
    const previewError = ref('')
    const onlyOfficeLoading = ref(false)
    const onlyOfficeError = ref('')
    const onlyOfficeEditor = ref(null)
    const onlyOfficeHostId = ref('knowledge-onlyoffice-preview')
    const currentPreviewPageIndex = ref(0)

    const isAdmin = computed(() => isManagerUser(currentUser.value))
    const uploadHint = computed(() =>
      isAdmin.value
        ? '支持 PDF / Word / Excel / PPT / 图片 / 文本文件，重复同名文件将自动覆盖并升级版本'
        : '当前账号只有查阅权限，上传、删除和修改仅管理员可用'
    )

    const filteredFolders = computed(() => folders.value)

    const filteredDocuments = computed(() => {
      const key = documentSearch.value.trim()

      return documents.value.filter((doc) => {
        const inFolder = activeFolder.value ? doc.folder === activeFolder.value : true
        const matchesSearch = key ? doc.name.includes(key) : true
        return inFolder && matchesSearch
      })
    })

    const totalCount = computed(() => filteredDocuments.value.length)
    const totalPages = computed(() => Math.max(1, Math.ceil(totalCount.value / pageSize.value)))
    const visibleDocuments = computed(() => {
      const start = (currentPage.value - 1) * pageSize.value
      return filteredDocuments.value.slice(start, start + pageSize.value)
    })
    const activePreviewPage = computed(() => {
      const pages = selectedDocument.value?.previewPages || []
      return pages[currentPreviewPageIndex.value] || pages[0] || null
    })
    const previewMetaLine = computed(() => buildPreviewMetaLine(selectedDocument.value))
    const previewSecondaryMetaLine = computed(() =>
      buildPreviewSecondaryMetaLine(selectedDocument.value, activePreviewPage.value)
    )
    const shouldUseOnlyOffice = computed(() => supportsOnlyOfficePreview(selectedDocument.value))
    const excelPreviewTable = computed(() =>
      selectedDocument.value?.previewKind === 'table'
        ? buildExcelPreviewTable(activePreviewPage.value)
        : { headers: [], rows: [] }
    )

    function revokePreviewBlob() {
      if (previewBlobUrl.value) {
        URL.revokeObjectURL(previewBlobUrl.value)
        previewBlobUrl.value = ''
      }
    }

    function destroyOnlyOfficeEditor() {
      if (onlyOfficeEditor.value?.destroyEditor) {
        onlyOfficeEditor.value.destroyEditor()
      }
      onlyOfficeEditor.value = null
    }

    async function mountOnlyOfficeEditor(documentId) {
      onlyOfficeLoading.value = true
      onlyOfficeError.value = ''
      destroyOnlyOfficeEditor()

      try {
        const payload = await fetchKnowledgeOnlyOfficeConfig(documentId)
        await loadOnlyOfficeApi(payload.documentServerUrl)
        await nextTick()

        if (!window.DocsAPI?.DocEditor) {
          throw new Error('ONLYOFFICE 编辑器未正确加载。')
        }

        onlyOfficeHostId.value = `knowledge-onlyoffice-preview-${documentId}`
        await nextTick()
        onlyOfficeEditor.value = new window.DocsAPI.DocEditor(onlyOfficeHostId.value, payload.config)
      } catch (error) {
        onlyOfficeError.value = error.message || 'ONLYOFFICE 预览加载失败。'
      } finally {
        onlyOfficeLoading.value = false
      }
    }

    async function loadLibrary(options = {}) {
      loading.value = true
      try {
        const payload = await fetchKnowledgeLibrary()
        folders.value = payload.folders || []
        documents.value = payload.documents || []
        emit('summary-change', { totalDocuments: documents.value.length })

        const activeExists = folders.value.some((folder) => folder.name === activeFolder.value)
        if (!activeExists) {
          activeFolder.value = folders.value[0]?.name || ''
        }

        if (options.preserveSelection && selectedDocument.value?.id) {
          const exists = documents.value.some((doc) => doc.id === selectedDocument.value.id)
          if (!exists) {
            selectedDocument.value = null
            revokePreviewBlob()
          }
        }
      } catch (error) {
        emit('summary-change', { totalDocuments: 0 })
        toast(error.message || '知识库加载失败。')
      } finally {
        loading.value = false
      }
    }

    async function selectDocument(documentId) {
      previewLoading.value = true
      previewError.value = ''
      onlyOfficeError.value = ''
      revokePreviewBlob()
      destroyOnlyOfficeEditor()

      try {
        const payload = await fetchKnowledgeDocument(documentId)
        selectedDocument.value = payload
        currentPreviewPageIndex.value = 0

        if (supportsOnlyOfficePreview(payload)) {
          await mountOnlyOfficeEditor(documentId)
        } else if (payload.previewKind === 'pdf' || payload.previewKind === 'image') {
          const blob = await fetchKnowledgeDocumentBlob(documentId, 'inline')
          previewBlobUrl.value = URL.createObjectURL(blob)
        }
      } catch (error) {
        previewError.value = error.message || '预览加载失败。'
        toast(previewError.value)
      } finally {
        previewLoading.value = false
      }
    }

    async function handleDownload(document) {
      try {
        const blob = await fetchKnowledgeDocumentBlob(document.id, 'attachment')
        triggerFileDownload(blob, document.name)
      } catch (error) {
        toast(error.message || '下载失败。')
      }
    }

    function triggerUpload() {
      if (!isAdmin.value || uploading.value) {
        return
      }
      uploadInput.value?.click()
    }

    async function uploadFiles(fileList) {
      const files = Array.from(fileList || []).filter(Boolean)
      if (!files.length || !activeFolder.value || !isAdmin.value) {
        return
      }

      uploading.value = true
      try {
        let latestDocumentId = ''
        for (const file of files) {
          const payload = await uploadKnowledgeDocument({ folder: activeFolder.value, file })
          latestDocumentId = payload.id
        }

        await loadLibrary({ preserveSelection: true })
        toast(files.length > 1 ? `已上传 ${files.length} 个知识库文件。` : '知识库文件已上传。')

        if (latestDocumentId) {
          await selectDocument(latestDocumentId)
        }
      } catch (error) {
        toast(error.message || '上传失败。')
      } finally {
        uploading.value = false
        if (uploadInput.value) {
          uploadInput.value.value = ''
        }
      }
    }

    async function handleFileInput(event) {
      await uploadFiles(event.target.files)
    }

    async function handleDrop(event) {
      if (!isAdmin.value) {
        return
      }
      await uploadFiles(event.dataTransfer?.files)
    }

    async function handleDelete(document) {
      if (!isAdmin.value || deletingId.value) {
        return
      }

      const confirmed = window.confirm(`确认删除文件“${document.name}”吗？`)
      if (!confirmed) {
        return
      }

      deletingId.value = document.id
      try {
        await deleteKnowledgeDocument(document.id)
        if (selectedDocument.value?.id === document.id) {
          selectedDocument.value = null
          revokePreviewBlob()
        }
        await loadLibrary()
        toast('知识库文件已删除。')
      } catch (error) {
        toast(error.message || '删除失败。')
      } finally {
        deletingId.value = ''
      }
    }

    function changePageSize(size) {
      pageSize.value = size
      pageSizeOpen.value = false
      currentPage.value = 1
    }

    function closePreview() {
      selectedDocument.value = null
      previewError.value = ''
      currentPreviewPageIndex.value = 0
      revokePreviewBlob()
      destroyOnlyOfficeEditor()
      onlyOfficeError.value = ''
    }

    function selectPreviewPage(index) {
      currentPreviewPageIndex.value = index
    }

    watch(filteredDocuments, () => {
      currentPage.value = 1
      pageSizeOpen.value = false

      if (selectedDocument.value && !filteredDocuments.value.some((doc) => doc.id === selectedDocument.value.id)) {
        closePreview()
      }
    })

    watch(activeFolder, () => {
      closePreview()
    })

    onMounted(() => {
      loadLibrary()
    })

    onBeforeUnmount(() => {
      revokePreviewBlob()
    })

    return {
      activeFolder,
      activePreviewPage,
      changePageSize,
      closePreview,
      excelPreviewTable,
      currentPage,
      currentPreviewPageIndex,
      deletingId,
      documentSearch,
      filteredFolders,
      handleDelete,
      handleDownload,
      handleDrop,
      handleFileInput,
      isAdmin,
      loading,
      pageSize,
      pageSizeOpen,
      pageSizes,
      onlyOfficeError,
      onlyOfficeHostId,
      onlyOfficeLoading,
      previewMetaLine,
      previewSecondaryMetaLine,
      previewBlobUrl,
      previewError,
      previewLoading,
      shouldUseOnlyOffice,
      selectDocument,
      selectPreviewPage,
      selectedDocument,
      totalCount,
      totalPages,
      triggerUpload,
      uploadHint,
      uploadInput,
      uploading,
      visibleDocuments
    }
  }
}