'use client'

import Image from 'next/image'
import { useEffect, useMemo, useRef, useState } from 'react'

const MAX_FILE_COUNT = 60
const MAX_FILE_BYTES = 200 * 1024 * 1024

function fileKey(file: File) {
  return `${file.name}-${file.size}-${file.lastModified}`
}

export function WorkReviewImageDropzone({
  files,
  onChange,
  disabled,
  label = '图片',
}: {
  files: File[]
  onChange: (files: File[]) => void
  disabled?: boolean
  label?: string
}) {
  const inputRef = useRef<HTMLInputElement | null>(null)
  const dragDepthRef = useRef(0)
  const [dragging, setDragging] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const previewUrls = useMemo(() => files.map((file) => URL.createObjectURL(file)), [files])

  useEffect(() => () => {
    previewUrls.forEach((url) => URL.revokeObjectURL(url))
  }, [previewUrls])

  const addFiles = (selected: FileList | File[]) => {
    if (disabled) return
    const candidates = [...files, ...Array.from(selected)]
    const deduplicated = candidates.filter((file, index, items) => (
      items.findIndex((candidate) => fileKey(candidate) === fileKey(file)) === index
    ))
    const invalid = deduplicated.find((file) => !file.type.startsWith('image/'))
    if (invalid) {
      setError(`文件「${invalid.name}」不是图片`)
      return
    }
    const oversized = deduplicated.find((file) => file.size > MAX_FILE_BYTES)
    if (oversized) {
      setError(`图片「${oversized.name}」超过 200MB`)
      return
    }
    if (deduplicated.length > MAX_FILE_COUNT) {
      setError(`一次最多选择 ${MAX_FILE_COUNT} 张图片`)
      return
    }
    setError(null)
    onChange(deduplicated)
  }

  return (
    <div>
      <input
        ref={inputRef}
        type="file"
        accept="image/png,image/jpeg,image/gif,image/webp"
        multiple
        disabled={disabled}
        aria-label={`选择${label}`}
        className="hidden"
        onChange={(event) => {
          addFiles(event.currentTarget.files || [])
          event.currentTarget.value = ''
        }}
      />
      <button
        type="button"
        disabled={disabled}
        aria-label={`上传${label}`}
        onClick={() => inputRef.current?.click()}
        onDragEnter={(event) => {
          event.preventDefault()
          if (disabled) return
          dragDepthRef.current += 1
          setDragging(true)
        }}
        onDragOver={(event) => {
          event.preventDefault()
          if (!disabled) event.dataTransfer.dropEffect = 'copy'
        }}
        onDragLeave={(event) => {
          event.preventDefault()
          if (disabled) return
          dragDepthRef.current = Math.max(0, dragDepthRef.current - 1)
          if (dragDepthRef.current === 0) setDragging(false)
        }}
        onDrop={(event) => {
          event.preventDefault()
          dragDepthRef.current = 0
          setDragging(false)
          addFiles(event.dataTransfer.files)
        }}
        className={`flex min-h-28 w-full flex-col items-center justify-center rounded-lg border border-dashed px-4 py-5 text-center transition-all disabled:cursor-not-allowed disabled:opacity-60 ${
          dragging
            ? 'scale-[1.01] border-[#0050cb] bg-[#eef5ff]'
            : 'border-[#aebbd0] bg-[#fbfcfe] hover:border-[#0050cb] hover:bg-[#f7faff]'
        }`}
      >
        <span className={`flex h-9 w-9 items-center justify-center rounded-full text-[21px] ${
          dragging ? 'bg-[#0050cb] text-white' : 'bg-[#eaf2ff] text-[#0050cb]'
        }`}>↑</span>
        <span className="mt-2 text-[13px] font-bold text-[#0050cb]">
          {dragging ? '松开即可添加' : '拖拽图片到这里，或点击选择'}
        </span>
        <span className="mt-1 text-[11px] leading-5 text-[#7b8494]">
          支持 PNG、JPG、GIF、WebP；长图会自动生成预览与切片
        </span>
      </button>

      {error && <div className="mt-2 text-[12px] font-semibold text-[#b42318]" role="alert">{error}</div>}

      {files.length > 0 && (
        <div className="mt-3 grid grid-cols-2 gap-2 sm:grid-cols-3">
          {files.map((file, index) => (
            <div key={fileKey(file)} className="group relative overflow-hidden rounded-lg border border-[#e1e7ef] bg-white">
              <div className="relative aspect-[4/3]">
                <Image
                  src={previewUrls[index]}
                  alt={file.name}
                  fill
                  unoptimized
                  className="object-cover"
                />
                <span className="absolute left-2 top-2 rounded-full bg-black/65 px-2 py-0.5 text-[10px] font-bold text-white">
                  {index + 1}
                </span>
                <button
                  type="button"
                  disabled={disabled}
                  onClick={() => onChange(files.filter((_, fileIndex) => fileIndex !== index))}
                  className="absolute right-2 top-2 flex h-7 w-7 items-center justify-center rounded-full bg-black/65 text-[18px] text-white opacity-90 transition-opacity hover:bg-[#b42318] disabled:cursor-not-allowed"
                  aria-label={`移除 ${file.name}`}
                >
                  ×
                </button>
              </div>
              <div className="min-w-0 px-2.5 py-2">
                <div className="truncate text-[11px] font-semibold text-[#344054]" title={file.name}>{file.name}</div>
                <div className="mt-0.5 text-[10px] text-[#98a2b3]">
                  {file.size < 1024 * 1024
                    ? `${Math.max(1, Math.round(file.size / 1024))} KB`
                    : `${(file.size / 1024 / 1024).toFixed(1)} MB`}
                </div>
              </div>
            </div>
          ))}
        </div>
      )}
    </div>
  )
}