import { fileExists } from '../../lib/file-exists'
import { getPagePaths } from '../../shared/lib/page-path/get-page-paths'
import { nonNullable } from '../../lib/non-nullable'
import { join, sep, normalize } from 'path'
import { promises } from 'fs'
import { warn } from '../../build/output/log'
import chalk from '../../lib/chalk'

async function isTrueCasePagePath(pagePath: string, pagesDir: string) {
  const pageSegments = normalize(pagePath).split(sep).filter(Boolean)
  const segmentExistsPromises = pageSegments.map(async (segment, i) => {
    const segmentParentDir = join(pagesDir, ...pageSegments.slice(0, i))
    const parentDirEntries = await promises.readdir(segmentParentDir)
    return parentDirEntries.includes(segment)
  })

  return (await Promise.all(segmentExistsPromises)).every(Boolean)
}

/**
 * Finds a page file with the given parameters. If the page is duplicated with
 * multiple extensions it will throw, otherwise it will return the *relative*
 * path to the page file or null if it is not found.
 *
 * @param pagesDir Absolute path to the pages folder with trailing `/pages`.
 * @param normalizedPagePath The page normalized (it will be denormalized).
 * @param pageExtensions Array of page extensions.
 */
export async function findPageFile(
  pagesDir: string,
  normalizedPagePath: string,
  pageExtensions: string[],
  isAppDir: boolean
): Promise<string | null> {
  const pagePaths = getPagePaths(normalizedPagePath, pageExtensions, isAppDir)
  const [existingPath, ...others] = (
    await Promise.all(
      pagePaths.map(async (path) => {
        const filePath = join(pagesDir, path)
        return (await fileExists(filePath)) ? path : null
      })
    )
  ).filter(nonNullable)

  if (!existingPath) {
    return null
  }

  if (!(await isTrueCasePagePath(existingPath, pagesDir))) {
    return null
  }

  if (others.length > 0) {
    warn(
      `Duplicate page detected. ${chalk.cyan(
        join('pages', existingPath)
      )} and ${chalk.cyan(
        join('pages', others[0])
      )} both resolve to ${chalk.cyan(normalizedPagePath)}.`
    )
  }

  return existingPath
}

// Determine if the file is leaf node page file under layouts,
// The filename should start with 'page' and end with one of the allowed extensions
export function isLayoutsLeafPage(filePath: string, pageExtensions: string[]) {
  return new RegExp(
    `(^page|[\\\\/]page)\\.(?:${pageExtensions.join('|')})$`
  ).test(filePath)
}