src/ink/hooks/use-tab-status.ts

import { useContext, useEffect, useRef } from 'react'
import {
  CLEAR_TAB_STATUS,
  supportsTabStatus,
  tabStatus,
  wrapForMultiplexer,
} from '../termio/osc.js'
import type { Color } from '../termio/types.js'
import { TerminalWriteContext } from '../useTerminalNotification.js'

export type TabStatusKind = 'idle' | 'busy' | 'waiting'

const rgb = (r: number, g: number, b: number): Color => ({
  type: 'rgb',
  r,
  g,
  b,
})

// Per the OSC 21337 usage guide's suggested mapping.
const TAB_STATUS_PRESETS: Record<
  TabStatusKind,
  { indicator: Color; status: string; statusColor: Color }
> = {
  idle: {
    indicator: rgb(0, 215, 95),
    status: 'Idle',
    statusColor: rgb(136, 136, 136),
  },
  busy: {
    indicator: rgb(255, 149, 0),
    status: 'Working…',
    statusColor: rgb(255, 149, 0),
  },
  waiting: {
    indicator: rgb(95, 135, 255),
    status: 'Waiting',
    statusColor: rgb(95, 135, 255),
  },
}

/**
 * Declaratively set the tab-status indicator (OSC 21337).
 *
 * Emits a colored dot + short status text to the tab sidebar. Terminals
 * that don't support OSC 21337 discard the sequence silently, so this is
 * safe to call unconditionally. Wrapped for tmux/screen passthrough.
 *
 * Pass `null` to opt out. If a status was previously set, transitioning to
 * `null` emits CLEAR_TAB_STATUS so toggling off mid-session doesn't leave
 * a stale dot. Process-exit cleanup is handled by ink.tsx's unmount path.
 */
export function useTabStatus(kind: TabStatusKind | null): void {
  const writeRaw = useContext(TerminalWriteContext)
  const prevKindRef = useRef<TabStatusKind | null>(null)

  useEffect(() => {
    // When kind transitions from non-null to null (e.g. user toggles off
    // showStatusInTerminalTab mid-session), clear the stale dot.
    if (kind === null) {
      if (prevKindRef.current !== null && writeRaw && supportsTabStatus()) {
        writeRaw(wrapForMultiplexer(CLEAR_TAB_STATUS))
      }
      prevKindRef.current = null
      return
    }

    prevKindRef.current = kind
    if (!writeRaw || !supportsTabStatus()) return
    writeRaw(wrapForMultiplexer(tabStatus(TAB_STATUS_PRESETS[kind])))
  }, [kind, writeRaw])
}