import { prefixRegex } from '@rolldown/pluginutils'
import MiniSearch from 'minisearch'
import path from 'node:path'
import { createDebug } from 'obug'
import type { Plugin, ViteDevServer } from 'vite'
import type { SiteConfig } from '../config'
import type { DefaultTheme } from '../defaultTheme'
import { createMarkdownRenderer } from '../markdown/markdown'
import type { MarkdownCompileResult } from '../markdownToVue'
import type { PageArtifactStore } from '../pageArtifacts'
import { getLocaleForPath, slash, type MarkdownEnv } from '../shared'
import { readFile } from '../utils/fs'
import { processIncludes } from '../utils/processIncludes'

const debug = createDebug('vitepress:local-search')

const LOCAL_SEARCH_INDEX_ID = '@localSearchIndex'
const LOCAL_SEARCH_INDEX_REQUEST_PATH = '/' + LOCAL_SEARCH_INDEX_ID

const headingRegex = /<h(\d*).*?>(.*?<a.*? href="#.*?".*?>.*?<\/a>)<\/h\1>/gi
const headingContentRegex = /(.*)<a.*? href="#(.*?)".*?>.*?<\/a>/i

interface IndexObject {
  id: string
  text: string
  title: string
  titles: string[]
}

export async function localSearchPlugin(
  siteConfig: SiteConfig<DefaultTheme.Config>,
  stubIndex = false,
  pageArtifactStore?: PageArtifactStore
): Promise<Plugin> {
  if (stubIndex || siteConfig.site.themeConfig?.search?.provider !== 'local') {
    return {
      name: 'vitepress:local-search',
      resolveId: {
        filter: { id: prefixRegex(LOCAL_SEARCH_INDEX_ID) },
        handler() {
          return LOCAL_SEARCH_INDEX_REQUEST_PATH
        }
      },
      load: {
        filter: { id: prefixRegex(LOCAL_SEARCH_INDEX_REQUEST_PATH) },
        handler() {
          return `export default '{}'`
        }
      }
    }
  }

  // Lazily created only when an artifact cannot satisfy search indexing. This
  // lets a fully seeded production build avoid initializing Markdown/Shiki.
  let publicDir = siteConfig.publicDir
  let mdPromise: ReturnType<typeof createMarkdownRenderer> | undefined
  const getMarkdownRenderer = () =>
    (mdPromise ??= createMarkdownRenderer(
      siteConfig.srcDir,
      siteConfig.markdown,
      siteConfig.site.base,
      siteConfig.logger,
      publicDir,
      siteConfig.cacheDir
    ))

  const options = siteConfig.site.themeConfig.search.options || {}

  async function render(file: string, artifact?: MarkdownCompileResult) {
    const { srcDir, cleanUrls = false } = siteConfig
    const md = await getMarkdownRenderer()
    const relativePath = slash(path.relative(srcDir, file))
    const env: MarkdownEnv = { path: file, relativePath, cleanUrls }
    let src: string
    try {
      const raw = await readFile(file)
      src = await processIncludes(md, srcDir, raw, file, [], cleanUrls)
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error
      // Dynamic routes have no physical output file. Their seeded artifact is
      // the only source available; physical pages retain the historical raw
      // read/include semantics and avoid applying enforce-pre transforms twice.
      src = artifact?.markdownSource ?? ''
      if (!src) debug(`File not found: ${file}`)
    }
    if (options._transformHtml) {
      const html = await md.renderAsync(src, env)
      return options._transformHtml(html, env)
    } else if (options._render) {
      return options._render(src, env, md)
    } else {
      const html = await md.renderAsync(src, env)
      return env.frontmatter?.search === false ? '' : html
    }
  }

  const indexByLocales = new Map<string, MiniSearch<IndexObject>>()

  function getIndexByLocale(locale: string) {
    let index = indexByLocales.get(locale)
    if (!index) {
      index = new MiniSearch<IndexObject>({
        fields: ['title', 'titles', 'text'],
        storeFields: ['title', 'titles'],
        ...options.miniSearch?.options
      })
      indexByLocales.set(locale, index)
    }
    return index
  }

  let server: ViteDevServer | undefined
  let pending: Promise<void>

  let indexVersion = 0

  function onIndexUpdated() {
    if (!server) return
    // bust the per-locale import urls emitted below — the browser module
    // cache and the transform cache would otherwise serve the old index
    indexVersion++
    server.moduleGraph.onFileChange(LOCAL_SEARCH_INDEX_REQUEST_PATH)
    // HMR
    const mod = server.moduleGraph.getModuleById(
      LOCAL_SEARCH_INDEX_REQUEST_PATH
    )
    if (!mod) return
    server.ws.send({
      type: 'update',
      updates: [
        {
          acceptedPath: mod.url,
          path: mod.url,
          timestamp: Date.now(),
          type: 'js-update'
        }
      ]
    })
  }

  function getDocId(file: string) {
    let relFile = slash(path.relative(siteConfig.srcDir, file))
    relFile = siteConfig.rewrites.map[relFile] || relFile
    let id = slash(path.join(siteConfig.site.base, relFile))
    id = id.replace(/(^|\/)index\.md$/, '$1')
    id = id.replace(/\.md$/, siteConfig.cleanUrls ? '' : '.html')
    return id
  }

  async function indexFile(page: string) {
    const file = path.join(siteConfig.srcDir, page)
    const artifactPage = siteConfig.rewrites.map[page] || page
    // get file metadata
    const fileId = getDocId(file)
    const locale = getLocaleForPath(
      siteConfig.site,
      siteConfig.rewrites.map[page] || page
    )
    const index = getIndexByLocale(locale)
    // retrieve file and split into "sections"
    const artifact = await pageArtifactStore?.getCurrent(artifactPage)
    let html: string | undefined

    if (artifact) {
      if (options._transformHtml) {
        html = await options._transformHtml(artifact.html, {
          ...(artifact.markdownEnv ?? {
            path: file,
            relativePath: artifact.pageData.relativePath,
            cleanUrls: siteConfig.cleanUrls ?? false,
            frontmatter: artifact.pageData.frontmatter
          })
        })
      } else if (!options._render) {
        html =
          artifact.pageData.frontmatter.search === false ? '' : artifact.html
      }
    }

    if (html == null) {
      html = await render(file, artifact)
    }
    if (!html) return
    const sections =
      // user provided generator
      (await options.miniSearch?._splitIntoSections?.(file, html)) ??
      // default implementation
      splitPageIntoSections(html)
    // add sections to the locale index
    for await (const section of sections) {
      if (!section || !(section.text || section.titles)) break
      const { anchor, text, titles } = section
      const id = anchor ? [fileId, anchor].join('#') : fileId
      index.has(id) && index.discard(id)
      index.add({
        id,
        text,
        title: titles.at(-1)!,
        titles: titles.slice(0, -1)
      })
    }
  }

  async function scanForBuild() {
    debug('🔍️ Indexing files for search...')
    for (const page of siteConfig.pages) {
      await indexFile(page)
    }
    debug('✅ Indexing finished...')
  }

  return {
    name: 'vitepress:local-search',

    configResolved(config) {
      publicDir = config.publicDir
    },

    config() {
      return {
        optimizeDeps: {
          include: [
            'vitepress > @vueuse/integrations/useFocusTrap',
            'vitepress > mark.js/src/vanilla.js',
            'vitepress > minisearch'
          ]
        }
      }
    },

    configureServer(_server) {
      server = _server
      pending = scanForBuild().then(onIndexUpdated)
    },

    resolveId: {
      filter: { id: prefixRegex(LOCAL_SEARCH_INDEX_ID) },
      handler(id) {
        return `/${id}`
      }
    },

    load: {
      filter: { id: prefixRegex(LOCAL_SEARCH_INDEX_REQUEST_PATH) },
      async handler(id) {
        if (id === LOCAL_SEARCH_INDEX_REQUEST_PATH) {
          await pending
          if (process.env.NODE_ENV === 'production') {
            await scanForBuild()
          }
          let records: string[] = []
          for (const [locale] of indexByLocales) {
            records.push(
              `${JSON.stringify(
                locale
              )}: () => import('${LOCAL_SEARCH_INDEX_ID}${locale}${
                server ? `?v=${indexVersion}` : ''
              }')`
            )
          }
          return `export default {${records.join(',')}}`
        } else {
          await pending
          return `export default ${JSON.stringify(
            JSON.stringify(
              indexByLocales.get(
                id
                  .replace(LOCAL_SEARCH_INDEX_REQUEST_PATH, '')
                  .replace(/\?.*$/, '')
              ) ?? {}
            )
          )}`
        }
      }
    },

    async hotUpdate({ file }) {
      if (this.environment.name !== 'client') return

      if (file.endsWith('.md')) {
        const page = slash(path.relative(siteConfig.srcDir, file))
        // only index actual pages, not includes or route templates
        if (siteConfig.pages.includes(page)) {
          await indexFile(page)
          debug('🔍️ Updated', file)
          onIndexUpdated()
        }
      }
    }
  }
}

/**
 * Splits HTML into sections based on headings
 */
function* splitPageIntoSections(html: string) {
  const result = html.split(headingRegex)
  result.shift()
  let parentTitles: string[] = []
  for (let i = 0; i < result.length; i += 3) {
    const level = parseInt(result[i]) - 1
    const heading = result[i + 1]
    const headingResult = headingContentRegex.exec(heading)
    const title = clearHtmlTags(headingResult?.[1] ?? '').trim()
    const anchor = headingResult?.[2] ?? ''
    const content = result[i + 2]
    if (!title || !content) continue
    let titles = parentTitles.slice(0, level)
    titles[level] = title
    titles = titles.filter(Boolean)
    yield { anchor, titles, text: getSearchableText(content) }
    if (level === 0) {
      parentTitles = [title]
    } else {
      parentTitles[level] = title
    }
  }
}

function getSearchableText(content: string) {
  content = clearHtmlTags(content)
  return content
}

function clearHtmlTags(str: string) {
  return str.replace(/<[^>]*>/g, '')
}