/**
 * public/launcher.ts — the home "session chooser" shown when no tab is open.
 *
 * Opening the app no longer auto-creates or auto-restores tabs. Instead this
 * start screen lists the host's running sessions as live preview thumbnails
 * (read-only xterm, same as the manage page) so the user picks which to open —
 * or starts a new one. Sessions persist server-side, so opening one replays its
 * full scrollback.
 */

import { Terminal } from '@xterm/xterm'

interface LiveSession {
  id: string
  createdAt: number
  clientCount: number
  status: 'working' | 'waiting' | 'idle' | 'unknown'
  exited: boolean
  cwd: string | null
  cols: number
  rows: number
}

interface Preview {
  id: string
  cols: number
  rows: number
  data: string
}

export interface LauncherHooks {
  onOpen: (id: string) => void
  onNew: () => void
}

const THUMB_W = 320
const THUMB_MAX_H = 200
const REFRESH_MS = 5000
const CLEAR = '\x1b[2J\x1b[3J\x1b[H\x1b[0m'
const THEME = { background: '#0e0f13', foreground: '#e7e8ec', cursor: '#0e0f13' }

function el<K extends keyof HTMLElementTagNameMap>(
  tag: K,
  cls?: string,
  text?: string,
): HTMLElementTagNameMap[K] {
  const node = document.createElement(tag)
  if (cls) node.className = cls
  if (text !== undefined) node.textContent = text
  return node
}

function relTime(ms: number): string {
  const s = Math.max(0, (Date.now() - ms) / 1000)
  if (s < 60) return `${Math.floor(s)}s`
  if (s < 3600) return `${Math.floor(s / 60)}m`
  if (s < 86400) return `${Math.floor(s / 3600)}h`
  return `${Math.floor(s / 86400)}d`
}

function statusText(s: LiveSession['status']): string {
  return s === 'working' ? '⚙ working' : s === 'waiting' ? '⏳ waiting' : s === 'idle' ? '✓ idle' : '·'
}

function sessionName(s: LiveSession): string {
  return s.cwd ? (s.cwd.split('/').filter(Boolean).pop() ?? s.cwd) : s.id.slice(0, 8)
}

interface Card {
  el: HTMLElement
  term: Terminal
  inner: HTMLElement
  thumb: HTMLElement
  watch: HTMLElement
  status: HTMLElement
  meta: HTMLElement
}

export interface Launcher {
  setVisible(v: boolean): void
  refresh(): void
}

export function mountLauncher(host: HTMLElement, hooks: LauncherHooks): Launcher {
  const root = el('div', 'launcher')
  root.style.display = 'none'
  host.appendChild(root)

  const head = el('div', 'launcher-head')
  head.append(el('div', 'launcher-title', 'Your sessions'))
  const sub = el('div', 'launcher-sub', '')
  const actions = el('div', 'launcher-actions')
  const newBtn = el('button', 'launcher-new', '＋ New session')
  newBtn.addEventListener('click', () => hooks.onNew())
  const manage = el('a', 'mg-btn', '🗂 Manage') as HTMLAnchorElement
  manage.href = '/manage.html'
  actions.append(newBtn, manage)
  head.append(sub, actions)
  root.append(head)

  const grid = el('div', 'mg-grid')
  root.append(grid)

  const cards = new Map<string, Card>()
  let timer: ReturnType<typeof setInterval> | null = null

  function fit(card: Card): void {
    const w = card.inner.offsetWidth
    const h = card.inner.offsetHeight
    if (w === 0 || h === 0) return
    const scale = Math.min(1, THUMB_W / w)
    card.inner.style.transform = `scale(${scale})`
    card.thumb.style.height = `${Math.min(h * scale, THUMB_MAX_H)}px`
  }

  function makeCard(s: LiveSession): Card {
    const cardEl = el('div', 'mg-card')
    const h = el('div', 'mg-card-head')
    const title = el('span', 'mg-name', sessionName(s))
    const status = el('span', `mg-status mg-${s.status}`, statusText(s.status))
    const watch = el('span', s.clientCount > 0 ? 'mg-watch live' : 'mg-watch', `👁 ${s.clientCount}`)
    h.append(title, status, watch)

    const thumb = el('div', 'mg-thumb')
    const inner = el('div', 'mg-thumb-inner')
    thumb.append(inner)
    thumb.addEventListener('click', () => hooks.onOpen(s.id))

    const meta = el('div', 'mg-meta')
    const actions2 = el('div', 'mg-actions')
    const open = el('button', 'mg-open', 'Open ↗')
    open.addEventListener('click', () => hooks.onOpen(s.id))
    actions2.append(open)

    const term = new Terminal({
      cols: Math.max(2, s.cols),
      rows: Math.max(2, s.rows),
      disableStdin: true,
      cursorBlink: false,
      fontFamily: 'Menlo, Consolas, monospace',
      fontSize: 12,
      scrollback: 0,
      theme: THEME,
    })
    term.open(inner)

    cardEl.append(h, thumb, meta, actions2)
    return { el: cardEl, term, inner, thumb, watch, status, meta }
  }

  async function loadPreview(id: string, card: Card): Promise<void> {
    try {
      const res = await fetch(`/live-sessions/${id}/preview`)
      if (!res.ok) return
      const p = (await res.json()) as Preview
      if (card.term.cols !== Math.max(2, p.cols) || card.term.rows !== Math.max(2, p.rows)) {
        card.term.resize(Math.max(2, p.cols), Math.max(2, p.rows))
      }
      card.term.reset()
      card.term.write(CLEAR + p.data, () => requestAnimationFrame(() => fit(card)))
    } catch {
      /* preview is best-effort */
    }
  }

  async function refresh(): Promise<void> {
    let sessions: LiveSession[] = []
    try {
      const res = await fetch('/live-sessions')
      const data: unknown = await res.json()
      if (Array.isArray(data)) sessions = data as LiveSession[]
    } catch {
      sessions = []
    }

    sub.textContent = sessions.length
      ? `${sessions.length} running on this host — pick one to open`
      : 'No sessions running yet'

    const seen = new Set<string>()
    for (const s of sessions) {
      seen.add(s.id)
      let card = cards.get(s.id)
      if (!card) {
        card = makeCard(s)
        cards.set(s.id, card)
        grid.append(card.el)
      }
      card.status.className = `mg-status mg-${s.status}`
      card.status.textContent = statusText(s.status)
      card.watch.className = s.clientCount > 0 ? 'mg-watch live' : 'mg-watch'
      card.watch.textContent = `👁 ${s.clientCount}`
      card.meta.textContent = `${s.cwd ?? 'unknown dir'} · ${s.cols}×${s.rows} · ${relTime(s.createdAt)} old`
      void loadPreview(s.id, card)
    }
    for (const [id, card] of cards) {
      if (!seen.has(id)) {
        card.term.dispose()
        card.el.remove()
        cards.delete(id)
      }
    }

    grid.querySelector('.mg-empty')?.remove()
    if (sessions.length === 0) {
      grid.append(el('div', 'mg-empty', 'No running sessions. Click “New session” to start one.'))
    }
  }

  return {
    setVisible(v: boolean): void {
      root.style.display = v ? 'block' : 'none'
      if (v) {
        void refresh()
        if (timer === null) {
          timer = setInterval(() => {
            if (root.style.display !== 'none') void refresh()
          }, REFRESH_MS)
        }
      } else {
        if (timer !== null) {
          clearInterval(timer)
          timer = null
        }
        for (const card of cards.values()) card.term.dispose()
        cards.clear()
        grid.replaceChildren()
      }
    },
    refresh(): void {
      void refresh()
    },
  }
}