import { and, asc, desc, eq, gt, inArray, lt, or } from 'drizzle-orm'
import { commentAttachments, commentReactions, comments, favorites, tags, threadSubscriptions, uploads, uploadReactions, uploadTags, users } from '../../db/schema'
import type { CommentAttachment } from '~~/shared/utils/attachments'

export default defineEventHandler(async (event) => {
  const id = getRouterParam(event, 'id') ?? ''
  if (!/^[A-Za-z0-9]{1,16}$/.test(id)) {
    throw createError({ statusCode: 400, statusMessage: 'Ungültige ID' })
  }
  const db = useDb()

  const uploadRows = await db
    .select({
      id: uploads.id,
      type: uploads.type,
      fileName: uploads.fileName,
      externalUrl: uploads.externalUrl,
      originalName: uploads.originalName,
      mimeType: uploads.mimeType,
      previewImage: uploads.previewImage,
      previewTitle: uploads.previewTitle,
      audioMeta: uploads.audioMeta,
      createdAt: uploads.createdAt,
      userName: users.name,
      userId: users.id,
      userColor: users.color,
      userAvatar: users.avatar,
      userCardEffect: users.cardEffect,
      userCardEffectColor: users.cardEffectColor,
      userCardVignette: users.cardVignette,
      userCardBorderEffect: users.cardBorderEffect,
      userCardBorderEffectColor: users.cardBorderEffectColor,
    })
    .from(uploads)
    .innerJoin(users, eq(uploads.userId, users.id))
    .where(eq(uploads.id, id))
    .limit(1)
  const upload = uploadRows[0]
  if (!upload) {
    throw createError({ statusCode: 404, statusMessage: 'Upload nicht gefunden' })
  }

  const commentRows = await db
    .select({
      id: comments.id,
      content: comments.content,
      createdAt: comments.createdAt,
      userName: users.name,
      userId: users.id,
      userColor: users.color,
      userAvatar: users.avatar,
    })
    .from(comments)
    .innerJoin(users, eq(comments.userId, users.id))
    .where(eq(comments.uploadId, id))
    .orderBy(asc(comments.createdAt))

  // Nachbarn in Grid-Reihenfolge (createdAt desc, id desc als Tiebreak)
  const sessionUser = await getSessionUser(event)
  const commentIds = commentRows.map(c => c.id)
  const [reactionRows, uploadReactionRows, favRows, newerRows, olderRows, tagRows, attachmentRows, subscriptionRows] = await Promise.all([
    commentIds.length
      ? db
          .select({
            commentId: commentReactions.commentId,
            emoji: commentReactions.emoji,
            userId: commentReactions.userId,
            userName: users.name,
          })
          .from(commentReactions)
          .innerJoin(users, eq(commentReactions.userId, users.id))
          .where(inArray(commentReactions.commentId, commentIds))
          .orderBy(asc(commentReactions.createdAt))
      : Promise.resolve([]),
    db
      .select({
        emoji: uploadReactions.emoji,
        userId: uploadReactions.userId,
        userName: users.name,
      })
      .from(uploadReactions)
      .innerJoin(users, eq(uploadReactions.userId, users.id))
      .where(eq(uploadReactions.uploadId, id))
      .orderBy(asc(uploadReactions.createdAt)),
    db
      .select({ id: users.id, name: users.name, color: users.color, avatar: users.avatar })
      .from(favorites)
      .innerJoin(users, eq(favorites.userId, users.id))
      .where(eq(favorites.uploadId, id))
      .orderBy(desc(favorites.createdAt)),
    db
      .select({ id: uploads.id })
      .from(uploads)
      .where(or(
        gt(uploads.createdAt, upload.createdAt),
        and(eq(uploads.createdAt, upload.createdAt), gt(uploads.id, upload.id)),
      ))
      .orderBy(asc(uploads.createdAt), asc(uploads.id))
      .limit(1),
    db
      .select({ id: uploads.id })
      .from(uploads)
      .where(or(
        lt(uploads.createdAt, upload.createdAt),
        and(eq(uploads.createdAt, upload.createdAt), lt(uploads.id, upload.id)),
      ))
      .orderBy(desc(uploads.createdAt), desc(uploads.id))
      .limit(1),
    db
      .select({ name: tags.name })
      .from(uploadTags)
      .innerJoin(tags, eq(uploadTags.tagId, tags.id))
      .where(eq(uploadTags.uploadId, id))
      .orderBy(asc(tags.name)),
    commentIds.length
      ? db
          .select()
          .from(commentAttachments)
          .where(inArray(commentAttachments.commentId, commentIds))
          .orderBy(asc(commentAttachments.id))
      : Promise.resolve([]),
    sessionUser
      ? db.select({ enabled: threadSubscriptions.enabled }).from(threadSubscriptions)
          .where(and(eq(threadSubscriptions.uploadId, id), eq(threadSubscriptions.userId, sessionUser.id))).limit(1)
      : Promise.resolve([]),
  ])

  const attachmentsByComment = new Map<number, CommentAttachment[]>()
  for (const a of attachmentRows) {
    let list = attachmentsByComment.get(a.commentId)
    if (!list) {
      list = []
      attachmentsByComment.set(a.commentId, list)
    }
    list.push({ id: a.id, name: a.originalName, url: `/uploads/attachments/${a.fileName}`, mimeType: a.mimeType, size: a.size, cover: a.cover, meta: a.meta as CommentAttachment['meta'] })
  }

  const reactionsByComment = new Map<number, { emoji: string, count: number, me: boolean, names: string[] }[]>()
  for (const r of reactionRows) {
    let list = reactionsByComment.get(r.commentId)
    if (!list) {
      list = []
      reactionsByComment.set(r.commentId, list)
    }
    let entry = list.find(e => e.emoji === r.emoji)
    if (!entry) {
      entry = { emoji: r.emoji, count: 0, me: false, names: [] }
      list.push(entry)
    }
    entry.count += 1
    entry.names.push(r.userName)
    if (r.userId === sessionUser?.id) entry.me = true
  }

  const uploadReactionList: { emoji: string, count: number, me: boolean, names: string[] }[] = []
  for (const r of uploadReactionRows) {
    let entry = uploadReactionList.find(e => e.emoji === r.emoji)
    if (!entry) {
      entry = { emoji: r.emoji, count: 0, me: false, names: [] }
      uploadReactionList.push(entry)
    }
    entry.count += 1
    entry.names.push(r.userName)
    if (r.userId === sessionUser?.id) entry.me = true
  }

  const url = upload.externalUrl ?? `/uploads/${upload.fileName}`
  const embedId = upload.type === 'youtube' && upload.externalUrl
    ? getYoutubeId(upload.externalUrl)
    : upload.type === 'twitch' && upload.externalUrl
      ? serializeTwitchTarget(getTwitchTarget(upload.externalUrl))
      : null
  return {
    upload: { ...upload, url, embedId, userAvatarUrl: avatarUrl(upload.userAvatar), tags: tagRows.map(t => t.name) },
    comments: commentRows.map(c => ({ ...c, userAvatarUrl: avatarUrl(c.userAvatar), reactions: reactionsByComment.get(c.id) ?? [], attachments: attachmentsByComment.get(c.id) ?? [] })),
    uploadReactions: uploadReactionList,
    favoritedBy: favRows.map(f => ({ id: f.id, name: f.name, color: f.color, avatarUrl: avatarUrl(f.avatar) })),
    isFavorited: sessionUser ? favRows.some(f => f.id === sessionUser.id) : false,
    isSubscribed: subscriptionRows[0]?.enabled ?? false,
    newerId: newerRows[0]?.id ?? null,
    olderId: olderRows[0]?.id ?? null,
  }
})