petal/web/src/components/Companion/useCompanion.ts

import { useCallback, useEffect, useRef, useState } from 'react'
import type { SaveStatus } from '../../hooks/useAutoSave'
import {
  BREAKS,
  ENCOURAGEMENTS,
  GREETING,
  MILESTONES,
  TIPS,
  WELCOME_BACK,
  milestoneLine,
  pick,
  type Line,
} from './tips'

// The kitten's expression. Maps to a Lottie animation when assets are present,
// otherwise to an emoji placeholder (see PetalCompanion).
export type Mood = 'idle' | 'happy' | 'talking' | 'sleeping' | 'celebrate'

export type BubbleTone = 'cheer' | 'tip' | 'break'
export interface Bubble extends Line {
  tone: BubbleTone
}

interface Signals {
  wordCount: number
  saveStatus: SaveStatus
  // Monotonic counters bumped by the app on each editor change / accepted
  // suggestion — lets the companion react without a full event bus.
  editTick: number
  acceptTick: number
}

// Timing knobs (ms). Tuned to feel present but never naggy.
const IDLE_MS = 75_000 // no edits → kitten naps
const BREAK_MS = 25 * 60_000 // continuous writing → suggest a break
const TIP_MIN_GAP = 4 * 60_000 // at most one spontaneous tip per this window
const PROACTIVE_GAP = 40_000 // floor between any two unsolicited bubbles
const BUBBLE_MS = 6_500 // how long a bubble lingers
const CHEER_MS = 4_500 // shorter for quick cheers
const now = () => Date.now()

// useCompanion is the behavior engine: it watches writing signals and decides
// when the kitten speaks, what mood it shows, and how to pace itself so the
// companion feels alive without interrupting. UI-agnostic — returns state only.
export function useCompanion({ wordCount, saveStatus, editTick, acceptTick }: Signals) {
  const [mood, setMood] = useState<Mood>('idle')
  const [bubble, setBubble] = useState<Bubble | null>(null)

  const lastActivity = useRef(now())
  const sessionStart = useRef(now())
  const lastProactive = useRef(0)
  const lastTip = useRef(0)
  const lastBreak = useRef(0)
  const nextMilestone = useRef(0) // index into MILESTONES
  const sleeping = useRef(false)

  const bubbleTimer = useRef<ReturnType<typeof setTimeout>>(undefined)
  const moodTimer = useRef<ReturnType<typeof setTimeout>>(undefined)

  // Show a bubble + talking mood, then settle back. `proactive` messages respect
  // the spacing floor; user-triggered ones (cheers) always go through.
  const say = useCallback((b: Bubble, opts?: { proactive?: boolean; celebrate?: boolean }) => {
    const t = now()
    if (opts?.proactive) {
      if (bubble) return
      if (t - lastProactive.current < PROACTIVE_GAP) return
      lastProactive.current = t
    }
    sleeping.current = false
    setBubble(b)
    setMood(opts?.celebrate ? 'celebrate' : 'talking')
    clearTimeout(bubbleTimer.current)
    clearTimeout(moodTimer.current)
    const dur = b.tone === 'cheer' ? CHEER_MS : BUBBLE_MS
    bubbleTimer.current = setTimeout(() => setBubble(null), dur)
    moodTimer.current = setTimeout(() => setMood('idle'), dur)
  }, [bubble])

  const dismiss = useCallback(() => {
    clearTimeout(bubbleTimer.current)
    clearTimeout(moodTimer.current)
    setBubble(null)
    setMood('idle')
  }, [])

  // Opening hello (once), after a short beat so it doesn't race the first paint.
  useEffect(() => {
    const id = setTimeout(() => say({ ...GREETING, tone: 'tip' }), 1200)
    return () => clearTimeout(id)
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [])

  // Edits: record activity and wake from a nap with a warm welcome-back.
  const firstEdit = useRef(true)
  useEffect(() => {
    if (firstEdit.current) {
      firstEdit.current = false
      return
    }
    lastActivity.current = now()
    if (sleeping.current) {
      sleeping.current = false
      sessionStart.current = now() // a fresh stretch starts on return
      say({ ...WELCOME_BACK, tone: 'cheer' })
    } else if (mood === 'sleeping') {
      setMood('idle')
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [editTick])

  // Accepts: always cheer (it's a direct response to her action).
  const firstAccept = useRef(true)
  useEffect(() => {
    if (firstAccept.current) {
      firstAccept.current = false
      return
    }
    say({ ...pick(ENCOURAGEMENTS), tone: 'cheer' }, { celebrate: true })
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [acceptTick])

  // Word-count milestones: cheer the first time each threshold is crossed.
  useEffect(() => {
    while (
      nextMilestone.current < MILESTONES.length &&
      wordCount >= MILESTONES[nextMilestone.current]
    ) {
      const n = MILESTONES[nextMilestone.current]
      nextMilestone.current += 1
      // Skip silently if we're just loading a long doc (no edits yet).
      if (!firstEdit.current) say({ ...milestoneLine(n), tone: 'cheer' }, { celebrate: true })
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [wordCount])

  // Occasional gentle cheer on a successful save (kept rare so it isn't noise).
  useEffect(() => {
    if (saveStatus === 'saved' && Math.random() < 0.18) {
      say({ ...pick(ENCOURAGEMENTS), tone: 'cheer' }, { proactive: true })
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [saveStatus])

  // Heartbeat: nap when idle, suggest breaks, and drop the odd writing tip.
  useEffect(() => {
    const id = setInterval(() => {
      const t = now()
      const idleFor = t - lastActivity.current

      if (idleFor > IDLE_MS) {
        sleeping.current = true
        if (!bubble) setMood('sleeping')
        return // resting — no nudges while she's away
      }

      // Active: time for a break?
      if (t - sessionStart.current > BREAK_MS && t - lastBreak.current > BREAK_MS) {
        lastBreak.current = t
        sessionStart.current = t
        say({ ...pick(BREAKS), tone: 'break' }, { proactive: true })
        return
      }

      // Otherwise an occasional tip.
      if (t - lastTip.current > TIP_MIN_GAP) {
        lastTip.current = t
        say({ ...pick(TIPS), tone: 'tip' }, { proactive: true })
      }
    }, 10_000)
    return () => clearInterval(id)
  }, [bubble, say])

  useEffect(
    () => () => {
      clearTimeout(bubbleTimer.current)
      clearTimeout(moodTimer.current)
    },
    [],
  )

  return { mood, bubble, dismiss }
}