Typing Animation

"use client"

import {
  useEffect,
  useMemo,
  useRef,
  useState,
  type ComponentType,
  type RefAttributes,
  type RefObject,
} from "react"
import {
  motion,
  useInView,
  type DOMMotionComponents,
  type HTMLMotionProps,
  type MotionProps,
} from "motion/react"

import { cn } from "@/lib/utils"

const motionElements = {
  article: motion.article,
  div: motion.div,
  h1: motion.h1,
  h2: motion.h2,
  h3: motion.h3,
  h4: motion.h4,
  h5: motion.h5,
  h6: motion.h6,
  li: motion.li,
  p: motion.p,
  section: motion.section,
  span: motion.span,
} as const

type MotionElementType = Extract<
  keyof DOMMotionComponents,
  keyof typeof motionElements
>
type TypingAnimationMotionComponent = ComponentType<
  Omit<HTMLMotionProps<"span">, "ref"> & RefAttributes<HTMLElement>
>

interface TypingAnimationProps extends Omit<MotionProps, "children"> {
  children?: string
  words?: string[]
  className?: string
  duration?: number
  typeSpeed?: number
  deleteSpeed?: number
  delay?: number
  pauseDelay?: number
  loop?: boolean
  as?: MotionElementType
  startOnView?: boolean
  showCursor?: boolean
  blinkCursor?: boolean
  cursorStyle?: "line" | "block" | "underscore"
}

export function TypingAnimation({
  children,
  words,
  className,
  duration = 100,
  typeSpeed,
  deleteSpeed,
  delay = 0,
  pauseDelay = 1000,
  loop = false,
  as: Component = "span",
  startOnView = true,
  showCursor = true,
  blinkCursor = true,
  cursorStyle = "line",
  ...props
}: TypingAnimationProps) {
  const MotionComponent = motionElements[
    Component
  ] as TypingAnimationMotionComponent

  const [displayedText, setDisplayedText] = useState<string>("")
  const [currentWordIndex, setCurrentWordIndex] = useState(0)
  const [currentCharIndex, setCurrentCharIndex] = useState(0)
  const [phase, setPhase] = useState<"typing" | "pause" | "deleting">("typing")
  const elementRef = useRef<HTMLElement | null>(null)
  const isInView = useInView(elementRef as RefObject<Element>, {
    amount: 0.3,
    once: true,
  })

  const wordsToAnimate = useMemo(
    () => words ?? (children ? [children] : []),
    [words, children]
  )
  const hasMultipleWords = wordsToAnimate.length > 1

  const typingSpeed = typeSpeed ?? duration
  const deletingSpeed = deleteSpeed ?? typingSpeed / 2

  const shouldStart = startOnView ? isInView : true
  const animationSourceKey = useMemo(
    () => (words ? words.join("\u0000") : (children ?? "")),
    [words, children]
  )

  useEffect(() => {
    setDisplayedText("")
    setCurrentWordIndex(0)
    setCurrentCharIndex(0)
    setPhase("typing")
  }, [animationSourceKey])

  useEffect(() => {
    let timeout: ReturnType<typeof setTimeout> | null = null

    if (shouldStart && wordsToAnimate.length > 0) {
      const timeoutDelay =
        delay > 0 && displayedText === ""
          ? delay
          : phase === "typing"
            ? typingSpeed
            : phase === "deleting"
              ? deletingSpeed
              : pauseDelay

      timeout = setTimeout(() => {
        const currentWord = wordsToAnimate[currentWordIndex] || ""
        const graphemes = Array.from(currentWord)

        switch (phase) {
          case "typing":
            if (currentCharIndex < graphemes.length) {
              setDisplayedText(
                graphemes.slice(0, currentCharIndex + 1).join("")
              )
              setCurrentCharIndex(currentCharIndex + 1)
            } else {
              if (hasMultipleWords || loop) {
                const isLastWord =
                  currentWordIndex === wordsToAnimate.length - 1
                if (!isLastWord || loop) {
                  setPhase("pause")
                }
              }
            }
            break

          case "pause":
            setPhase("deleting")
            break

          case "deleting":
            if (currentCharIndex > 0) {
              setDisplayedText(
                graphemes.slice(0, currentCharIndex - 1).join("")
              )
              setCurrentCharIndex(currentCharIndex - 1)
            } else {
              const nextIndex = (currentWordIndex + 1) % wordsToAnimate.length
              setCurrentWordIndex(nextIndex)
              setPhase("typing")
            }
            break
        }
      }, timeoutDelay)
    }

    return () => {
      if (timeout !== null) {
        clearTimeout(timeout)
      }
    }
  }, [
    shouldStart,
    phase,
    currentCharIndex,
    currentWordIndex,
    displayedText,
    wordsToAnimate,
    hasMultipleWords,
    loop,
    typingSpeed,
    deletingSpeed,
    pauseDelay,
    delay,
  ])

  const currentWordGraphemes = Array.from(
    wordsToAnimate[currentWordIndex] || ""
  )
  const isComplete =
    !loop &&
    currentWordIndex === wordsToAnimate.length - 1 &&
    currentCharIndex >= currentWordGraphemes.length &&
    phase !== "deleting"

  const shouldShowCursor =
    showCursor &&
    !isComplete &&
    (hasMultipleWords || loop || currentCharIndex < currentWordGraphemes.length)

  const getCursorChar = () => {
    switch (cursorStyle) {
      case "block":
        return "▌"
      case "underscore":
        return "_"
      case "line":
      default:
        return "|"
    }
  }

  return (
    <MotionComponent
      ref={elementRef}
      className={cn(
        "leading-20 tracking-[-0.02em]",
        Component === "span" && "inline-block",
        className
      )}
      {...props}
    >
      {displayedText}
      {shouldShowCursor && (
        <span
          className={cn("inline-block", blinkCursor && "animate-blink-cursor")}
        >
          {getCursorChar()}
        </span>
      )}
    </MotionComponent>
  )
}