'use client'

import { useState, useRef } from 'react'
import { Card, CardContent } from '@/components/ui/card'
import { Button } from '@/components/ui/button'
import { Badge } from '@/components/ui/badge'
import { Upload, X, FileText, AlertCircle } from 'lucide-react'

interface FileRequirement {
  id: string
  label: string
  description?: string
  mimeTypes: string[]
  maxSizeMb?: number
  required: boolean
}

interface FileUploadSlotProps {
  requirement: FileRequirement
  isLocked: boolean
  onUpload: (file: File) => void
}

function formatFileSize(bytes: number): string {
  if (bytes === 0) return '0 B'
  const k = 1024
  const sizes = ['B', 'KB', 'MB', 'GB']
  const i = Math.floor(Math.log(bytes) / Math.log(k))
  return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i]
}

function formatMimeTypes(mimeTypes: string[]): string {
  const extensions = mimeTypes.map(mime => {
    const parts = mime.split('/')
    return parts[1] || mime
  })
  return extensions.join(', ').toUpperCase()
}

export function FileUploadSlot({ requirement, isLocked, onUpload }: FileUploadSlotProps) {
  const [selectedFile, setSelectedFile] = useState<File | null>(null)
  const [error, setError] = useState<string | null>(null)
  const fileInputRef = useRef<HTMLInputElement>(null)

  const handleFileSelect = (event: React.ChangeEvent<HTMLInputElement>) => {
    const file = event.target.files?.[0]
    if (!file) return

    setError(null)

    // Validate file type
    if (requirement.mimeTypes.length > 0 && !requirement.mimeTypes.includes(file.type)) {
      setError(`File type not allowed. Accepted types: ${formatMimeTypes(requirement.mimeTypes)}`)
      return
    }

    // Validate file size
    if (requirement.maxSizeMb) {
      const maxBytes = requirement.maxSizeMb * 1024 * 1024
      if (file.size > maxBytes) {
        setError(`File size exceeds ${requirement.maxSizeMb} MB limit`)
        return
      }
    }

    setSelectedFile(file)
    onUpload(file)
  }

  const handleRemove = () => {
    setSelectedFile(null)
    setError(null)
    if (fileInputRef.current) {
      fileInputRef.current.value = ''
    }
  }

  const handleClick = () => {
    if (!isLocked) {
      fileInputRef.current?.click()
    }
  }

  return (
    <Card className={isLocked ? 'opacity-60' : ''}>
      <CardContent className="p-4">
        <div className="flex items-start justify-between mb-3">
          <div className="flex-1">
            <div className="flex items-center gap-2 flex-wrap">
              <h3 className="font-medium">{requirement.label}</h3>
              {requirement.required && (
                <Badge variant="destructive" className="text-xs">
                  Required
                </Badge>
              )}
              {isLocked && (
                <Badge variant="secondary" className="text-xs">
                  Locked
                </Badge>
              )}
            </div>
            {requirement.description && (
              <p className="text-sm text-muted-foreground mt-1">
                {requirement.description}
              </p>
            )}
            <div className="flex flex-wrap gap-2 mt-2 text-xs text-muted-foreground">
              {requirement.mimeTypes.length > 0 && (
                <span>Accepted: {formatMimeTypes(requirement.mimeTypes)}</span>
              )}
              {requirement.maxSizeMb && (
                <span>• Max size: {requirement.maxSizeMb} MB</span>
              )}
            </div>
          </div>
        </div>

        {/* File preview or upload button */}
        {selectedFile ? (
          <div className="flex items-center gap-3 p-3 rounded-lg border bg-muted/50">
            <FileText className="h-8 w-8 text-brand-blue shrink-0" />
            <div className="flex-1 min-w-0">
              <p className="font-medium text-sm truncate" title={selectedFile.name}>
                {selectedFile.name}
              </p>
              <p className="text-xs text-muted-foreground">
                {formatFileSize(selectedFile.size)}
              </p>
            </div>
            <div className="flex gap-2 shrink-0">
              <Button
                size="sm"
                variant="outline"
                onClick={handleClick}
                disabled={isLocked}
              >
                Replace
              </Button>
              <Button
                size="sm"
                variant="ghost"
                onClick={handleRemove}
                disabled={isLocked}
              >
                <X className="h-4 w-4" />
              </Button>
            </div>
          </div>
        ) : (
          <div>
            <Button
              variant="outline"
              className="w-full border-dashed"
              onClick={handleClick}
              disabled={isLocked}
            >
              <Upload className="mr-2 h-4 w-4" />
              {isLocked ? 'Upload Disabled' : 'Choose File'}
            </Button>
            <input
              ref={fileInputRef}
              type="file"
              className="hidden"
              accept={requirement.mimeTypes.join(',')}
              onChange={handleFileSelect}
              disabled={isLocked}
            />
          </div>
        )}

        {/* Error message */}
        {error && (
          <div className="flex items-start gap-2 mt-3 p-2 rounded-md bg-red-50 border border-red-200">
            <AlertCircle className="h-4 w-4 text-red-600 shrink-0 mt-0.5" />
            <p className="text-sm text-red-700">{error}</p>
          </div>
        )}
      </CardContent>
    </Card>
  )
}