import fs from 'fs'
import path from 'path'
import type { DirectoryListing, FileEntry, MediaType } from '@/types'
import { resolveAndJail } from '@/lib/libraries'

const HIDDEN_FILES = /^\./

const VIDEO_EXTENSIONS = new Set(['.mp4', '.mov', '.mkv', '.avi', '.webm', '.m4v'])
const IMAGE_EXTENSIONS = new Set(['.jpg', '.jpeg', '.png', '.gif', '.webp', '.bmp', '.tiff', '.tif'])

function getMediaType(filename: string): MediaType {
  const ext = path.extname(filename).toLowerCase()
  if (VIDEO_EXTENSIONS.has(ext)) return 'video'
  if (IMAGE_EXTENSIONS.has(ext)) return 'image'
  return 'other'
}

function fileApiUrl(libraryId: string, relativePath: string): string {
  return `/api/file?libraryId=${encodeURIComponent(libraryId)}&path=${encodeURIComponent(relativePath)}`
}

function thumbnailApiUrl(libraryId: string, relativePath: string): string {
  return `/api/thumbnail?libraryId=${encodeURIComponent(libraryId)}&path=${encodeURIComponent(relativePath)}`
}

export function scanDirectory(
  libraryRoot: string,
  libraryId: string,
  subpath: string
): DirectoryListing {
  let absPath: string
  try {
    absPath = subpath ? resolveAndJail(libraryRoot, subpath) : libraryRoot
  } catch {
    return { path: subpath, entries: [] }
  }

  let dirents: fs.Dirent[]
  try {
    dirents = fs.readdirSync(absPath, { withFileTypes: true })
  } catch {
    return { path: subpath, entries: [] }
  }

  const entries: FileEntry[] = dirents
    .filter((d) => !HIDDEN_FILES.test(d.name))
    .map((d): FileEntry => {
      if (d.isDirectory()) {
        return {
          name: d.name,
          type: 'directory',
          mediaType: null,
          url: null,
          thumbnailUrl: null,
        }
      }

      const relPath = subpath ? path.join(subpath, d.name) : d.name
      const mediaType = getMediaType(d.name)
      const hasThumbnail = mediaType === 'image' || mediaType === 'video'

      return {
        name: d.name,
        type: 'file',
        mediaType,
        url: fileApiUrl(libraryId, relPath),
        thumbnailUrl: hasThumbnail ? thumbnailApiUrl(libraryId, relPath) : null,
      }
    })

  // Sort: directories first, then files; each group sorted alphabetically
  entries.sort((a, b) => {
    if (a.type !== b.type) return a.type === 'directory' ? -1 : 1
    return a.name.localeCompare(b.name)
  })

  return { path: subpath, entries }
}