import { useEffect, useRef, useState } from 'react'
import { Terminal } from '@xterm/xterm'
import { FitAddon } from '@xterm/addon-fit'
import { WebLinksAddon } from '@xterm/addon-web-links'
import { wsURL } from './api'
import { Spinner } from './ui'

export interface TermHandle { input: (s: string) => void; armCtrl: (v: boolean) => void }

interface Props {
  id: string; active: boolean
  register: (h: TermHandle | null) => void
  onStatus: (ok: boolean) => void
  onExit: () => void
}

import { currentThemeId, themeById } from './themes'

export default function TerminalPane({ id, active, register, onStatus, onExit }: Props) {
  const box = useRef<HTMLDivElement>(null)
  const activeRef = useRef(active)
  activeRef.current = active
  const cbs = useRef({ onStatus, onExit })
  cbs.current = { onStatus, onExit }
  const fitRef = useRef<() => void>(() => {})
  const [conn, setConn] = useState<'connecting' | 'open' | 'reconnecting' | 'exited'>('connecting')

  useEffect(() => {
    const el = box.current!
    const term = new Terminal({
      theme: themeById(currentThemeId()).xterm, fontFamily: 'ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace',
      fontSize: window.matchMedia('(pointer: coarse)').matches ? 13 : 14,
      cursorBlink: true, scrollback: 5000, allowProposedApi: true,
    })
    const fit = new FitAddon()
    term.loadAddon(fit)
    term.loadAddon(new WebLinksAddon())
    term.open(el)

    let ws: WebSocket | null = null
    let closed = false
    let ctrlArmed = false
    let retry = 0
    let retryTimer: number | undefined
    let lastSize = ''
    const enc = new TextEncoder()

    const queued: string[] = []
    const send = (s: string) => { if (ws && ws.readyState === WebSocket.OPEN) ws.send(enc.encode(s)); else queued.push(s) }
    const sendResize = () => {
      const key = `${term.cols}x${term.rows}`
      if (key === lastSize) return
      lastSize = key
      if (ws && ws.readyState === WebSocket.OPEN) ws.send(JSON.stringify({ type: 'resize', cols: term.cols, rows: term.rows }))
    }
    const doFit = () => {
      if (!activeRef.current || el.clientWidth === 0 || el.clientHeight === 0) return
      fit.fit()
      sendResize()
    }

    const connect = () => {
      if (closed) return
      const sock = new WebSocket(wsURL(id))
      sock.binaryType = 'arraybuffer'
      ws = sock
      sock.onopen = () => { retry = 0; setConn('open'); cbs.current.onStatus(true); lastSize = ''; doFit(); while (queued.length) sock.send(enc.encode(queued.shift()!)) }
      sock.onmessage = (ev) => {
        if (ev.data instanceof ArrayBuffer) { term.write(new Uint8Array(ev.data)); return }
        try {
          const m = JSON.parse(ev.data)
          if (m.type === 'exit') { term.write('\r\n\x1b[90m[process exited' + (m.code !== undefined ? ` (${m.code})` : '') + ']\x1b[0m\r\n'); closed = true; setConn('exited'); cbs.current.onExit() }
          if (m.type === 'closed') closed = true
        } catch { /* ignore */ }
      }
      sock.onclose = () => {
        if (ws !== sock || closed) return
        cbs.current.onStatus(false)
        setConn('reconnecting')
        retryTimer = window.setTimeout(connect, Math.min(1000 * 2 ** retry++, 15000))
      }
      sock.onerror = () => sock.close()
    }
    connect()

    term.onData((d) => {
      if (ctrlArmed && d.length === 1) {
        ctrlArmed = false
        const c = d.toUpperCase().charCodeAt(0)
        if (c >= 64 && c <= 95) { send(String.fromCharCode(c & 0x1f)); return }
      }
      send(d)
    })
    term.onBinary((d) => send(d))
    term.onResize(sendResize)

    fitRef.current = () => { doFit(); term.focus() }
    const ro = new ResizeObserver(() => doFit())
    ro.observe(el)
    const onVis = () => { if (document.visibilityState === 'visible' && ws && ws.readyState !== WebSocket.OPEN && !closed) { clearTimeout(retryTimer); connect() } }
    document.addEventListener('visibilitychange', onVis)

    const onTheme = (e: Event) => { term.options.theme = (e as CustomEvent).detail.xterm }
    window.addEventListener('hamlab:theme', onTheme)

    register({ input: send, armCtrl: (v) => { ctrlArmed = v; term.focus() } })

    return () => {
      register(null)
      closed = true
      clearTimeout(retryTimer)
      document.removeEventListener('visibilitychange', onVis)
      window.removeEventListener('hamlab:theme', onTheme)
      ro.disconnect()
      ws?.close()
      term.dispose()
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [id])

  // Refit + focus whenever this pane becomes the visible one (after the display change applies).
  useEffect(() => {
    if (!active) return
    const t = window.setTimeout(() => fitRef.current(), 0)
    return () => clearTimeout(t)
  }, [active])

  return (
    <div className="term" style={{ display: active ? 'block' : 'none' }}>
      <div ref={box} className="term-inner" />
      {(conn === 'connecting' || conn === 'reconnecting') && (
        <div className="term-overlay"><Spinner /> {conn === 'connecting' ? 'connecting…' : 'reconnecting…'}</div>
      )}
    </div>
  )
}