import type { Response } from 'express'
import cheerio from 'cheerio'

import warmServer from '@/frame/lib/warm-server'
import { liquid } from '@/content-render/index'
import shortVersions from '@/versions/middleware/short-versions'
import contextualize from '@/frame/middleware/context/context'
import features from '@/versions/middleware/features'
import findPage from '@/frame/middleware/find-page'
import { createMinimalProcessor } from '@/content-render/unified/processor'
import getRedirect from '@/redirects/lib/get-redirect'
import type { ExtendedRequest, Page } from '@/types'

export type DocsUrls = {
  [identifier: string]: string
}

type Permalink = {
  href: string
  languageCode: string
}
type Redirects = {
  [from: string]: string
}

export type Check = {
  identifier: string
  url: string
  pageURL: string
  found: boolean
  fragment: string | undefined
  fragmentFound?: boolean
  fragmentCandidates?: string[]
  // If the URL lead to a redirect, this is its URL (starting with /en/...)
  redirectPageURL?: string
  // If the URL lead to a redirect, this is what the new URL should be
  // (for example /the/new/pathname#my-fragment)
  redirect?: string
}

export async function validateDocsUrl(docsUrls: DocsUrls, { checkFragments = false } = {}) {
  const site = await warmServer(['en'])
  const pages = site.pages
  const redirects: Redirects = site.redirects

  const checks: Check[] = []
  for (const [identifier, url] of Object.entries(docsUrls)) {
    if (!url.startsWith('/')) {
      throw new Error(`URL doesn't start with '/': ${url} (identifier: ${identifier})`)
    }
    const pathname = url.split('?')[0]
    // If the url is just '/' we want to check the homepage,
    // which is `/en`, not `/en/`.
    const [pageURL, fragment] = `/en${pathname === '/' ? '' : pathname}`.split('#')

    const page = pages[pageURL]
    const check: Check = {
      identifier,
      url,
      pageURL,
      fragment,
      found: !!page,
    }
    let redirectedPage: Page | null = null
    if (!page) {
      const redirect = getRedirect(pageURL, {
        userLanguage: 'en',
        redirects,
        pages,
      })
      if (redirect && isEnterpriseCloudRedirectOnly(pageURL, redirect)) {
        // Ignore this one. It just added enterprise-cloud@latest to the URL.
        continue
      }
      if (redirect) {
        redirectedPage = pages[redirect]
        if (!redirectedPage) {
          throw new Error(`The redirected page doesn't exist: ${redirect}`)
        }
        check.found = true
        check.redirectPageURL = redirect
        check.redirect = stripLanguagePrefix(redirect)
        if (fragment) {
          check.redirect += `#${fragment}`
        }
      }
    }

    if (checkFragments && fragment) {
      const permalink = (redirectedPage || page).permalinks[0]
      const html = await renderInnerHTML(redirectedPage || page, permalink)
      const $ = cheerio.load(html)
      check.fragmentFound = $(`#${fragment}`).length > 0 || $(`a[name="${fragment}"]`).length > 0
      if (!check.fragmentFound) {
        const fragmentCandidates: string[] = []
        $('h2[id], h3[id]').each((_, el) => {
          const id = $(el).attr('id')
          if (id) {
            fragmentCandidates.push(id)
          }
        })
        check.fragmentCandidates = fragmentCandidates
      }
    }
    checks.push(check)
  }
  return checks
}

function isEnterpriseCloudRedirectOnly(originalUrl: string, redirectUrl: string) {
  // A lot of URLs don't work in free-pro-team so all they do is redirect
  // from {OLD-URL} to "/enterprise-count@latest/{OLD-URL}"
  return redirectUrl.replace('/enterprise-cloud@latest', '') === originalUrl
}

async function renderInnerHTML(page: Page, permalink: Permalink) {
  const next = () => {}
  const res = {}

  const pagePath = permalink.href
  const req = {
    path: pagePath,
    language: permalink.languageCode,
    pagePath,
    cookies: {},
    // The contextualize() middleware will create a new one.
    // Here it just exists for the sake of TypeScript.
    context: {},
  }
  await contextualize(req as ExtendedRequest, res as Response, next)
  await shortVersions(req as ExtendedRequest, res as Response, next)
  await findPage(req as ExtendedRequest, res as Response, next)
  features(req as ExtendedRequest, res as Response, next)

  const markdown = await liquid.parseAndRender(page.markdown, req.context)
  const processor = createMinimalProcessor(req.context)
  const vFile = await processor.process(markdown)
  return vFile.toString()
}

function stripLanguagePrefix(url: string) {
  return url.replace(/^\/en\//, '/')
}