import React, { useEffect, useRef, useState } from 'react'

/**
 * TypewriterRotator
 *
 * Cycles through a list of phrases with a typing-and-deleting effect.
 * Designed for the soryu landing hero — sits inside a centred container,
 * so the caller controls position and the component just renders text.
 *
 * Honours `prefers-reduced-motion` by rendering the first phrase only,
 * statically.
 */

interface TypewriterRotatorProps {
  phrases: string[]
  /** ms per character while typing */
  typeMs?: number
  /** ms per character while deleting */
  deleteMs?: number
  /** ms to hold a fully-typed phrase before deleting */
  holdMs?: number
  /** ms to wait after deletion before the next phrase types in */
  gapMs?: number
  className?: string
}

export function TypewriterRotator({
  phrases,
  typeMs = 55,
  deleteMs = 28,
  holdMs = 2200,
  gapMs = 320,
  className,
}: TypewriterRotatorProps) {
  const [text, setText] = useState('')
  const [index, setIndex] = useState(0)
  const [phase, setPhase] = useState<'typing' | 'holding' | 'deleting' | 'gap'>('typing')
  const reduceMotion = useRef(
    typeof window !== 'undefined' &&
      window.matchMedia &&
      window.matchMedia('(prefers-reduced-motion: reduce)').matches,
  )

  useEffect(() => {
    if (reduceMotion.current) {
      setText(phrases[0] ?? '')
      return
    }
    const current = phrases[index % phrases.length] ?? ''
    let timer: number

    if (phase === 'typing') {
      if (text.length < current.length) {
        timer = window.setTimeout(() => setText(current.slice(0, text.length + 1)), typeMs)
      } else {
        timer = window.setTimeout(() => setPhase('holding'), 0)
      }
    } else if (phase === 'holding') {
      // Skip the hold-then-delete cycle entirely if there's only one phrase
      if (phrases.length <= 1) return
      timer = window.setTimeout(() => setPhase('deleting'), holdMs)
    } else if (phase === 'deleting') {
      if (text.length > 0) {
        timer = window.setTimeout(() => setText(current.slice(0, text.length - 1)), deleteMs)
      } else {
        timer = window.setTimeout(() => setPhase('gap'), 0)
      }
    } else if (phase === 'gap') {
      timer = window.setTimeout(() => {
        setIndex((i) => (i + 1) % phrases.length)
        setPhase('typing')
      }, gapMs)
    }

    return () => window.clearTimeout(timer)
  }, [text, phase, index, phrases, typeMs, deleteMs, holdMs, gapMs])

  return (
    <span className={className} role="status" aria-live="polite">
      <span className="tw-text">{text}</span>
      <span className="tw-caret" aria-hidden="true" />
    </span>
  )
}
