taskAnchorReminder.ts

import type { Task } from '../../utils/tasks.js'

// Short, generic "keep going" nudges that carry no task anchor. In a long
// session these dilute the task anchor and the model drifts off the task
// (see the long-session drift investigation, 2026-07-23). When one arrives and
// the task list still has unfinished items, we re-surface them once — only in
// this exact situation, so there is no per-turn token cost.
const ANCHORLESS_NUDGE_PATTERN =
  /(继续|接着|后续|往下|完成剩余|自动执行|自动跑|接着做|keep going|carry on|go on|continue|proceed|next step|move on)/i

// Guard against false positives on substantive messages that merely contain a
// nudge word (e.g. "继续用 X 方案重构 Y 模块…"). Real anchorless nudges are short
// — the ones seen in the investigation were all ≤12 CJK chars ("继续执行后续的工作").
const MAX_NUDGE_CHARS = 20

/**
 * True when `text` is a short "keep going" style nudge that carries no specific
 * task anchor. Long messages never match, even if they contain a nudge word.
 */
export function isAnchorlessNudge(text: string): boolean {
  const trimmed = text.trim()
  if (!trimmed || trimmed.length > MAX_NUDGE_CHARS) {
    return false
  }
  return ANCHORLESS_NUDGE_PATTERN.test(trimmed)
}

// Cap the injected list so a large backlog can't balloon the reminder.
const MAX_TASKS_IN_REMINDER = 20

const STATUS_ORDER: Record<string, number> = {
  in_progress: 0,
  pending: 1,
}

/**
 * Builds a `<system-reminder>` re-surfacing the unfinished tasks, or null when
 * there are none. in_progress tasks come first, then pending, ordered by id.
 */
export function buildTaskAnchorReminder(tasks: Task[]): string | null {
  const unfinished = tasks.filter(t => t.status !== 'completed')
  if (unfinished.length === 0) {
    return null
  }

  const sorted = [...unfinished].sort((a, b) => {
    const byStatus =
      (STATUS_ORDER[a.status] ?? 2) - (STATUS_ORDER[b.status] ?? 2)
    if (byStatus !== 0) {
      return byStatus
    }
    return Number(a.id) - Number(b.id)
  })

  const shown = sorted.slice(0, MAX_TASKS_IN_REMINDER)
  const lines = shown.map(t => `- #${t.id} [${t.status}] ${t.subject}`)
  const overflow = sorted.length - shown.length
  if (overflow > 0) {
    lines.push(`- …and ${overflow} more`)
  }

  return [
    '<system-reminder>',
    `You still have ${unfinished.length} unfinished task(s) in the current task list. The user's last message was a short "keep going" nudge without a specific anchor. Re-align to these tasks and continue the highest-priority unfinished one. Do not end your turn until the tasks are done or you genuinely need user input:`,
    ...lines,
    'Use TaskUpdate to mark progress as you go. This reminder is generated by the client, not sent by the user.',
    '</system-reminder>',
  ].join('\n')
}

// How many in_progress task names to spell out in the local notice.
const MAX_NOTICE_TASK_NAMES = 3

/**
 * Builds a display-only, user-facing notice for when a turn ends naturally while
 * tasks are still in_progress — a strong signal the model stopped mid-work. Only
 * in_progress tasks trigger it (a pending backlog the user is pacing does not).
 * Returns null when there is nothing worth surfacing. This text is shown in the
 * REPL and never sent to the model (zero token cost).
 */
export function buildUnfinishedTaskNotice(tasks: Task[]): string | null {
  const inProgress = tasks.filter(t => t.status === 'in_progress')
  if (inProgress.length === 0) {
    return null
  }
  const pendingCount = tasks.filter(t => t.status === 'pending').length
  const names = inProgress
    .slice(0, MAX_NOTICE_TASK_NAMES)
    .map(t => `#${t.id} ${t.subject}`)
    .join('、')
  const overflow = inProgress.length - MAX_NOTICE_TASK_NAMES
  const namesSuffix = overflow > 0 ? ` 等 ${inProgress.length} 个` : ''
  const pendingSuffix = pendingCount > 0 ? `，另有 ${pendingCount} 个待办` : ''
  return `还有进行中的任务未完成：${names}${namesSuffix}${pendingSuffix}。可直接回车继续，或用「按计划继续 Task #N」这类带锚点的话催促，避免长任务跑偏。`
}