import { useEffect, useRef, useState } from 'react'
import { getPosts, fileDownloadUrl, type ChannelKindKey, type FileRef, type Org, type PostView } from '../api/client'

const POLL_INTERVAL_MS = 3000

const timeFormatter = new Intl.DateTimeFormat('ko-KR', { hour: '2-digit', minute: '2-digit' })

function humanizeSize(bytes: number): string {
  if (bytes < 1024) {
    return `${bytes} B`
  }
  const kb = bytes / 1024
  if (kb < 1024) {
    return `${kb.toFixed(1)} KB`
  }
  return `${(kb / 1024).toFixed(1)} MB`
}

function AttachmentChip({ file }: { file: FileRef }) {
  return (
    <a
      href={fileDownloadUrl(file.id)}
      className="inline-flex items-center gap-1 rounded-md border border-gray-200 bg-gray-50 px-2 py-1 text-xs text-gray-600 hover:bg-gray-100"
    >
      <span className="font-medium text-gray-700">{file.name}</span>
      <span className="text-gray-400">({humanizeSize(file.size)})</span>
    </a>
  )
}

function PostRow({ post }: { post: PostView }) {
  if (post.system) {
    return <p className="py-1 text-center text-xs text-gray-400">{post.message}</p>
  }

  return (
    <div className="py-2">
      <div className="flex items-baseline gap-2">
        <span className="text-sm font-semibold text-gray-800">{post.user}</span>
        <span className="text-xs text-gray-400">{timeFormatter.format(new Date(post.createAt))}</span>
      </div>
      <p className="mt-0.5 whitespace-pre-wrap text-sm text-gray-700">{post.message}</p>
      {post.files.length > 0 && (
        <div className="mt-1.5 flex flex-wrap gap-1.5">
          {post.files.map((f) => (
            <AttachmentChip key={f.id} file={f} />
          ))}
        </div>
      )}
    </div>
  )
}

/** 기관관리 상세의 게시물 탭. 선택한 채널의 최근 게시글을 3초 간격으로 폴링해서 보여준다. */
export default function ChannelPosts({ org }: { org: Org }) {
  const bothMissing = !org.channelIdMj && !org.channelIdLaw
  const [channel, setChannel] = useState<ChannelKindKey>(org.channelIdMj ? 'mj' : 'law')
  const [posts, setPosts] = useState<PostView[]>([])
  const [error, setError] = useState<string | null>(null)

  const containerRef = useRef<HTMLDivElement>(null)
  const prevCountRef = useRef(0)

  useEffect(() => {
    if (bothMissing) {
      return
    }

    let cancelled = false

    async function load() {
      try {
        const data = await getPosts(org.id, channel)
        if (!cancelled) {
          setPosts(data)
          setError(null)
        }
      } catch {
        if (!cancelled) {
          setError('연결이 원활하지 않습니다. 재시도 중…')
        }
      }
    }

    void load()
    const timer = setInterval(() => void load(), POLL_INTERVAL_MS)
    return () => {
      cancelled = true
      clearInterval(timer)
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [channel, org.id])

  useEffect(() => {
    if (posts.length > prevCountRef.current && containerRef.current) {
      containerRef.current.scrollTop = containerRef.current.scrollHeight
    }
    prevCountRef.current = posts.length
  }, [posts.length])

  return (
    <div className="p-4">
      <div className="flex gap-2">
        <button
          type="button"
          disabled={!org.channelIdMj}
          title={org.channelIdMj ? undefined : '채널 미생성'}
          onClick={() => setChannel('mj')}
          className={`rounded-full border px-3 py-1 text-xs ${
            channel === 'mj'
              ? 'border-blue-600 bg-blue-50 font-semibold text-blue-700'
              : 'border-gray-200 text-gray-500'
          } disabled:cursor-not-allowed disabled:opacity-40`}
        >
          문정원
        </button>
        <button
          type="button"
          disabled={!org.channelIdLaw}
          title={org.channelIdLaw ? undefined : '채널 미생성'}
          onClick={() => setChannel('law')}
          className={`rounded-full border px-3 py-1 text-xs ${
            channel === 'law'
              ? 'border-blue-600 bg-blue-50 font-semibold text-blue-700'
              : 'border-gray-200 text-gray-500'
          } disabled:cursor-not-allowed disabled:opacity-40`}
        >
          법률검토
        </button>
      </div>

      {bothMissing ? (
        <p className="mt-6 text-center text-sm text-gray-400">채널이 아직 생성되지 않았습니다.</p>
      ) : (
        <>
          {error && (
            <p className="mt-3 rounded-md bg-amber-50 px-3 py-1.5 text-xs text-amber-700">{error}</p>
          )}
          <div
            ref={containerRef}
            className="mt-3 h-96 overflow-y-auto rounded-lg border border-gray-200 px-3"
          >
            {posts.length === 0 ? (
              <p className="py-6 text-center text-sm text-gray-300">게시글이 없습니다.</p>
            ) : (
              posts.map((post) => <PostRow key={post.id} post={post} />)
            )}
          </div>
        </>
      )}
    </div>
  )
}