import path from 'path'
import patterns from '../patterns.js'
import { allVersions } from '../all-versions.js'
import getOldPathsFromPermalink from './get-old-paths-from-permalink.js'
import { getVersionStringFromPath } from '../path-utils.js'
import { getNewVersionedPath } from '../old-versions-utils.js'
import removeFPTFromPath from '../remove-fpt-from-path.js'
const supportedVersions = new Set(Object.keys(allVersions))

export default function generateRedirectsForPermalinks(permalinks, redirectFrontmatter) {
  // account for Array or String frontmatter entries
  const redirectFrontmatterOldPaths = redirectFrontmatter
    ? Array.from([redirectFrontmatter]).flat()
    : []

  const redirects = {}

  // for every permalink...
  permalinks.forEach((permalink) => {
    // get an array of possible old paths, e.g., /desktop/guides/ from current permalink /desktop/
    const possibleOldPaths = getOldPathsFromPermalink(
      permalink.href,
      permalink.languageCode,
      permalink.pageVersion
    )

    // for each old path, add a redirect to the current permalink
    possibleOldPaths.forEach((oldPath) => {
      redirects[oldPath] = permalink.href
    })

    // for every redirect frontmatter old path...
    redirectFrontmatterOldPaths.forEach((frontmatterOldPath) => {
      // remove trailing slashes (sometimes present in frontmatter)
      frontmatterOldPath = frontmatterOldPath.replace(patterns.trailingSlash, '$1')

      // support hardcoded versions in redirect frontmatter
      if (supportedVersions.has(frontmatterOldPath.split('/')[1])) {
        redirects[frontmatterOldPath] = permalink.href
        redirects[`/en${frontmatterOldPath}`] = permalink.href
      }

      // get the old path for the current permalink version
      let versionedFrontmatterOldPath = path.posix.join(
        '/',
        permalink.languageCode,
        getNewVersionedPath(frontmatterOldPath)
      )
      const versionFromPath = getVersionStringFromPath(versionedFrontmatterOldPath)
      versionedFrontmatterOldPath = removeFPTFromPath(
        versionedFrontmatterOldPath.replace(versionFromPath, permalink.pageVersion)
      )

      // add it to the redirects object
      redirects[versionedFrontmatterOldPath] = permalink.href

      // then get an array of possible alternative old paths from the current versioned old path
      const possibleOldPathsForVersionedOldPaths = getOldPathsFromPermalink(
        versionedFrontmatterOldPath,
        permalink.languageCode,
        permalink.pageVersion
      )

      // and add each one to the redirects object
      possibleOldPathsForVersionedOldPaths.forEach((oldPath) => {
        redirects[oldPath] = permalink.href
      })
    })
  })

  // filter for unique entries only
  Object.entries(redirects).forEach(([oldPath, newPath]) => {
    if (oldPath === newPath) delete redirects[oldPath]
  })

  return redirects
}