"use client"

import { useRef } from "react"
import {
  motion,
  useReducedMotion,
  useScroll,
  useTransform,
  type MotionValue,
} from "motion/react"

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

function Word({
  children,
  progress,
  range,
}: {
  children: string
  progress: MotionValue<number>
  range: [number, number]
}) {
  const opacity = useTransform(progress, range, [0.14, 1])
  return (
    <motion.span style={{ opacity }} className="inline">
      {children}{" "}
    </motion.span>
  )
}

/** A statement whose words light up one after another while scrolling. */
export function ScrollStatement({
  text,
  className,
}: {
  text: string
  className?: string
}) {
  const ref = useRef<HTMLParagraphElement>(null)
  const reduced = useReducedMotion()
  const { scrollYProgress } = useScroll({
    target: ref,
    offset: ["start 0.85", "end 0.5"],
  })
  const words = text.split(" ")

  if (reduced) {
    return (
      <p ref={ref} className={className}>
        {text}
      </p>
    )
  }

  return (
    <p ref={ref} className={cn(className)}>
      {words.map((word, index) => (
        <Word
          key={index}
          progress={scrollYProgress}
          range={[index / words.length, (index + 1) / words.length]}
        >
          {word}
        </Word>
      ))}
    </p>
  )
}