frontend/src/components/LiveChordView.jsx

import React, { useMemo, useRef, useEffect, useState } from 'react'
import { transposeChord } from './ChordDisplay'

const VISIBLE_SIDES = 3 // number of chords to show on each side

function LiveChordView({ chordsData, currentTime, isPlaying, semitones = 0, onSeek }) {
  const containerRef = useRef(null)
  const [prevIndex, setPrevIndex] = useState(-1)

  const chords = chordsData?.chords || []
  const hasChords = chords.length > 0

  // Binary search for active chord
  const activeIndex = useMemo(() => {
    if (!hasChords) return -1
    let lo = 0, hi = chords.length - 1
    while (lo <= hi) {
      const mid = (lo + hi) >> 1
      if (currentTime < chords[mid].start_time) hi = mid - 1
      else if (currentTime >= chords[mid].end_time) lo = mid + 1
      else return mid
    }
    return -1
  }, [chords, currentTime, hasChords])

  // Track previous index for transition direction
  useEffect(() => {
    if (activeIndex !== -1 && activeIndex !== prevIndex) {
      setPrevIndex(activeIndex)
    }
  }, [activeIndex, prevIndex])

  if (!chordsData || !hasChords) return null

  // Progress within the current chord (0-1)
  const chordProgress = activeIndex >= 0
    ? (() => {
        const c = chords[activeIndex]
        const span = c.end_time - c.start_time
        return span > 0 ? Math.max(0, Math.min(1, (currentTime - c.start_time) / span)) : 0
      })()
    : 0

  // Build the visible window of chords
  const windowStart = Math.max(0, (activeIndex >= 0 ? activeIndex : 0) - VISIBLE_SIDES)
  const windowEnd = Math.min(chords.length - 1, (activeIndex >= 0 ? activeIndex : 0) + VISIBLE_SIDES)

  const visibleChords = []
  for (let i = windowStart; i <= windowEnd; i++) {
    visibleChords.push({ ...chords[i], index: i })
  }

  return (
    <div className="card rounded-xl p-6 animate-fade-in">
      {/* Teleprompter row */}
      <div
        ref={containerRef}
        className="flex items-center justify-center gap-2 overflow-hidden py-4"
        style={{ minHeight: '100px' }}
      >
        {visibleChords.map((entry) => {
          const i = entry.index
          const isActive = i === activeIndex
          const isPast = activeIndex >= 0 && i < activeIndex
          const isFuture = activeIndex >= 0 && i > activeIndex
          const displayChord = transposeChord(entry.chord, semitones)
          const isNC = displayChord === 'N.C.'

          // Distance from active chord (0 = active, 1 = adjacent, etc.)
          const distance = activeIndex >= 0 ? Math.abs(i - activeIndex) : 0

          // Opacity and scale based on distance
          let opacity, scale, textSize
          if (isActive) {
            opacity = 1
            scale = 1
            textSize = 'text-5xl'
          } else if (distance === 1) {
            opacity = isPast ? 0.35 : 0.5
            scale = 0.7
            textSize = 'text-2xl'
          } else if (distance === 2) {
            opacity = isPast ? 0.18 : 0.25
            scale = 0.55
            textSize = 'text-xl'
          } else {
            opacity = isPast ? 0.08 : 0.12
            scale = 0.45
            textSize = 'text-lg'
          }

          if (isNC && !isActive) {
            opacity *= 0.4
          }

          return (
            <button
              key={i}
              onClick={() => onSeek && onSeek(entry.start_time)}
              className={`
                flex-shrink-0 transition-all duration-300 ease-out cursor-pointer
                font-bold tracking-tight px-3
                ${textSize}
                ${isActive ? 'text-white' : 'text-gray-400'}
              `}
              style={{
                opacity,
                transform: `scale(${scale})`,
              }}
            >
              {displayChord}
            </button>
          )
        })}
      </div>

      {/* Subtle label */}
      {activeIndex >= 0 && (
        <p className="text-center text-[10px] text-gray-400 mt-1 uppercase tracking-wider">
          Now Playing
        </p>
      )}
    </div>
  )
}

export default React.memo(LiveChordView)