import { watch } from 'vue'

import { backlinkEventBus } from '@/bus/backlinkEventBus'
import { data } from '@/data/data'
import { DataType } from '@/data/DataType.enum'
import { useFile } from '@/hooks/useFile.hook'
import { Backlink } from '@/modules/note/models/Backlink'
import { BacklinkNote } from '@/modules/note/models/BacklinkNote'
import { resolvePath } from '@/modules/repo/services/resolvePath'
import { useUserRepoStore } from '@/modules/repo/store/userRepo.store'
import { isExternalLink } from '@/utils/link'
import { filenameToNoteTitle } from '@/utils/noteTitle'
import { confirmMessage } from '@/utils/notif'

const isMarkdown = (filename?: string) => filename?.endsWith('.md') ?? false

export const useComputeBacklinks = () => {
  const store = useUserRepoStore()

  watch(store, async () => {
    if (!store.userSettings?.backlink) {
      return
    }

    let notifiedForComputation = false

    const backlinks: Map<string, Backlink[]> = new Map()

    for (const file of store.files) {
      if (!isMarkdown(file.path) || !file.sha) {
        continue
      }

      const fileBacklinkId = data.generateId(DataType.BacklinkNote, file.sha)
      const fileBacklink = await data.get<DataType.BacklinkNote, BacklinkNote>(
        fileBacklinkId
      )
      if (fileBacklink) {
        continue
      }

      if (!backlinks.has(file.sha)) {
        backlinks.set(file.sha, [])
      }

      const { getContent } = useFile(file.sha, false)
      const note = await getContent()

      if (!note) {
        return
      }

      const parser = new DOMParser()
      const htmlDoc = parser.parseFromString(note, 'text/html')

      const links = htmlDoc.querySelectorAll('a')

      for (const link of links) {
        const href = link.getAttribute('href') ?? ''

        if (isExternalLink(href) || !isMarkdown(href)) {
          continue
        }

        const path = resolvePath(file.path ?? '', href)
        const backlinkFile = store.files.find((file) => file.path === path)

        if (!backlinkFile?.sha || !backlinkFile?.path) {
          continue
        }

        const previousBacklinks = backlinks.get(backlinkFile.sha) ?? []

        if (previousBacklinks.find((bl) => bl.sha === file.sha)) {
          continue
        }

        if (!notifiedForComputation) {
          notifiedForComputation = true
          confirmMessage('Updating backlinks...')
        }

        backlinks.set(backlinkFile.sha, [
          ...previousBacklinks,
          {
            sha: file.sha,
            title: filenameToNoteTitle(file.path ?? '')
          }
        ])
      }
    }

    for (const [sha, fileBacklinks] of backlinks) {
      const fileBacklinkId = data.generateId(DataType.BacklinkNote, sha)
      const backlinkNote: BacklinkNote = {
        _id: fileBacklinkId,
        $type: DataType.BacklinkNote,
        sha: sha,
        links: fileBacklinks
      }

      await data.update(backlinkNote)
      backlinkEventBus.emit({ fileSha: sha })
    }
  })
}