import { useEffect, useRef, useState } from 'react'
import { FaRotateRight } from 'react-icons/fa6'
import { Button } from '../ui'
import { PORTAL_URL, chatUploadUrl, getChatMessages, markChatRead, sendChatMessage, teamAuthHeaders } from '../../lib/teamApi'
import { loadChatComposer } from '../../lib/loadChatComposer'
import { messageMeta, needsFullRefresh, noticeText } from '../../lib/chatFormat'
import '../../styles/chat.css'

const POLL_MS = 15 * 1000

/**
 * Gespraech mit einem Kunden (Messenger und Reiter "Chat"). Sprechblasen und Eingabezeile kommen aus dem
 * Chat-Baustein des Portals (window.ChatComposer); React verwaltet nur die leeren Container.
 * Antworten fuer einen inzwischen gewechselten Kunden werden verworfen (alive je Effekt).
 */
export default function ChatThread({ customerId, customerName }) {
  const zoneRef = useRef(null)
  const boxRef = useRef(null)
  const composerRef = useRef(null)
  const [error, setError] = useState(null)
  const [notice, setNotice] = useState('')
  const [reloadKey, setReloadKey] = useState(0)
  // Name nur ueber eine Referenz lesen: kommt er spaeter (Liste/Kunden laden noch), startet das Gespraech nicht neu
  const nameRef = useRef(customerName)
  nameRef.current = customerName

  useEffect(() => {
    let alive = true
    let composer = null
    let timer = null
    let chat = null
    const state = { shown: new Set(), last: '', fullAt: 0 }
    setError(null)
    setNotice('')

    const append = (messages) => {
      const box = boxRef.current
      if (!alive || !box || !chat) return
      let added = false
      for (const msg of messages) {
        if (state.shown.has(msg.id)) continue
        state.shown.add(msg.id)
        box.appendChild(chat.renderMessage(msg, {
          mine: msg.sender === 'admin',
          meta: messageMeta(msg, nameRef.current),
          fileUrl: (att) => att.url,
        }))
        if (msg.createdAt > state.last) state.last = msg.createdAt
        added = true
      }
      if (added) box.scrollTop = box.scrollHeight
    }

    // Ganzer Verlauf mit frischen signierten Links (beim Oeffnen und nach 10 Minuten)
    const loadAll = async () => {
      const { messages } = await getChatMessages(customerId)
      if (!alive) return
      boxRef.current?.replaceChildren()
      state.shown = new Set()
      state.last = ''
      state.fullAt = Date.now()
      append(messages || [])
      markChatRead(customerId).catch(() => {})
    }

    const poll = async () => {
      if (!alive || document.visibilityState === 'hidden' || !chat) return
      try {
        if (needsFullRefresh(state.fullAt, Date.now())) return await loadAll()
        const { messages } = await getChatMessages(customerId, state.last)
        if (!alive) return
        append(messages || [])
        if ((messages || []).some((m) => m.sender === 'customer')) markChatRead(customerId).catch(() => {})
      } catch {
        /* naechste Abfrage versucht es erneut */
      }
    }

    ;(async () => {
      try {
        chat = await loadChatComposer({ baseUrl: PORTAL_URL })
        if (!alive) return
        chat.trackScroll(boxRef.current)
        composer = chat.create({
          root: composerRef.current,
          dropZone: zoneRef.current,
          uploadUrl: chatUploadUrl(customerId),
          requestHeaders: teamAuthHeaders,
          placeholder: `Antwort an ${nameRef.current || 'Kunde'}…`,
          placeholderShort: 'Antwort…',
          send: async ({ text, attachmentIds }) => {
            const { message, notice: result } = await sendChatMessage(customerId, { text, attachmentIds })
            const time = new Date().toLocaleTimeString('de-DE', { hour: '2-digit', minute: '2-digit' })
            if (alive) setNotice(noticeText(result, time))
            return message
          },
          onSent: (message) => append([message]),
        })
        await loadAll()
        // waehrend des Ladens verlassen: keinen Timer mehr anlegen, den das Aufraeumen nicht mehr sieht
        if (!alive) return
        timer = setInterval(poll, POLL_MS)
      } catch (err) {
        if (alive) setError(err.message || 'Die Unterhaltung konnte nicht geladen werden.')
      }
    })()

    const onVisible = () => { if (document.visibilityState === 'visible') poll() }
    document.addEventListener('visibilitychange', onVisible)
    return () => {
      alive = false
      clearInterval(timer)
      document.removeEventListener('visibilitychange', onVisible)
      composer?.destroy()
    }
  }, [customerId, reloadKey])

  return (
    <div className="woms-chat" ref={zoneRef}>
      {error && (
        <div className="flex items-center gap-2 wrap">
          <span className="muted">{error}</span>
          <Button variant="ghost" onClick={() => setReloadKey((k) => k + 1)}><FaRotateRight /> Erneut versuchen</Button>
        </div>
      )}
      <div className="chat-messages" ref={boxRef} aria-live="polite" />
      {notice && <div className="chat-notice muted">{notice}</div>}
      <div ref={composerRef} />
    </div>
  )
}