'use client'

import { useState, useEffect, useRef, useCallback } from 'react'
import { useLanguage } from '@/lib/i18n'
import { FileText, Loader2, MessageSquare, Trash2, AlertCircle, Plus } from 'lucide-react'
import { toast } from 'sonner'

interface Attachment {
  id: string
  fileName: string
  fileSize: number
  mimeType: string
  status: 'pending' | 'processing' | 'ready' | 'failed'
  pageCount: number | null
  error: string | null
  createdAt: string
}

interface NoteAttachmentsProps {
  noteId: string
  onOpenDocQA: (attachment: Attachment) => void
  onCountChange?: (count: number) => void
  triggerUpload?: number
}

function formatFileSize(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`
  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`
  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`
}

export function NoteAttachments({ noteId, onOpenDocQA, onCountChange, triggerUpload }: NoteAttachmentsProps) {
  const { t } = useLanguage()
  const [attachments, setAttachments] = useState<Attachment[]>([])
  const [uploading, setUploading] = useState(false)
  const [loading, setLoading] = useState(true)
  const fileInputRef = useRef<HTMLInputElement>(null)
  const sectionRef = useRef<HTMLDivElement>(null)
  const pollingRef = useRef<ReturnType<typeof setInterval> | null>(null)

  const fetchAttachments = useCallback(async () => {
    try {
      const res = await fetch(`/api/notes/${noteId}/attachments`)
      if (res.ok) {
        const data = await res.json()
        const list = data.data || []
        setAttachments(list)
        onCountChange?.(list.length)
        return list
      }
    } catch {}
    return []
  }, [noteId])

  useEffect(() => {
    fetchAttachments().finally(() => setLoading(false))
  }, [fetchAttachments])

  useEffect(() => {
    onCountChange?.(attachments.length)
  }, [attachments.length, onCountChange])

  useEffect(() => {
    const hasPending = attachments.some(a => a.status === 'pending' || a.status === 'processing')
    if (hasPending) {
      pollingRef.current = setInterval(fetchAttachments, 3000)
    } else if (pollingRef.current) {
      clearInterval(pollingRef.current)
      pollingRef.current = null
    }
    return () => {
      if (pollingRef.current) clearInterval(pollingRef.current)
    }
  }, [attachments, fetchAttachments])

  const lastTriggerRef = useRef(0)

  useEffect(() => {
    if (triggerUpload && triggerUpload > lastTriggerRef.current) {
      lastTriggerRef.current = triggerUpload
      if (attachments.length > 0) {
        sectionRef.current?.scrollIntoView({ behavior: 'smooth', block: 'center' })
      }
      fileInputRef.current?.click()
    }
  }, [triggerUpload, attachments.length])

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

    if (file.type !== 'application/pdf') {
      toast.error(t('attachments.onlyPdf') || 'Only PDF files are supported')
      return
    }

    if (file.size > 20 * 1024 * 1024) {
      toast.error(t('attachments.maxSize') || 'File too large (max 20MB)')
      return
    }

    setUploading(true)
    try {
      const formData = new FormData()
      formData.append('file', file)
      const res = await fetch(`/api/notes/${noteId}/attachments`, {
        method: 'POST',
        body: formData,
      })
      if (res.ok) {
        const data = await res.json()
        setAttachments(prev => [data.data, ...prev])
        toast.success(t('attachments.uploaded') || 'File uploaded — analyzing...')
        await fetchAttachments()
        setTimeout(() => {
          sectionRef.current?.scrollIntoView({ behavior: 'smooth', block: 'center' })
        }, 200)
      } else {
        const err = await res.json()
        toast.error(err.error || t('attachments.uploadFailed') || 'Upload failed')
      }
    } catch {
      toast.error(t('attachments.uploadError') || 'Upload error')
    } finally {
      setUploading(false)
      if (fileInputRef.current) fileInputRef.current.value = ''
    }
  }

  const handleDelete = async (attachmentId: string) => {
    try {
      const res = await fetch(`/api/notes/${noteId}/attachments/${attachmentId}`, { method: 'DELETE' })
      if (res.ok) {
        setAttachments(prev => prev.filter(a => a.id !== attachmentId))
        toast.success(t('attachments.deleted') || 'Attachment removed')
      }
    } catch {}
  }

  if (loading) return null

  return (
    <>
      <input ref={fileInputRef} type="file" accept=".pdf" className="hidden" onChange={handleUpload} />

      {attachments.length > 0 && (
        <div ref={sectionRef} className="pt-8">
          <div className="flex items-center justify-between mb-4">
            <h4 className="text-[11px] uppercase font-bold tracking-[.2em] text-muted-foreground">
              {t('attachments.title') || 'Documents'}
            </h4>
            <button
              onClick={() => fileInputRef.current?.click()}
              disabled={uploading}
              className="flex items-center gap-1 text-[11px] text-muted-foreground hover:text-foreground transition-colors disabled:opacity-50"
            >
              <Plus size={12} />
            </button>
          </div>

          <div className="grid grid-cols-1 sm:grid-cols-2 gap-3">
            {attachments.map(att => (
              <div
                key={att.id}
                className="relative group border border-border rounded-2xl bg-white dark:bg-white/[0.03] overflow-hidden transition-all hover:border-foreground/15"
              >
                <button
                  onClick={() => handleDelete(att.id)}
                  className="absolute top-2 right-2 p-1 rounded-lg text-muted-foreground/40 hover:text-destructive hover:bg-destructive/10 transition-all z-10"
                  title={t('attachments.remove') || 'Remove'}
                >
                  <Trash2 size={12} />
                </button>

                {(att.status === 'pending' || att.status === 'processing') && (
                  <div className="p-5">
                    <div className="flex items-center gap-3 mb-3">
                      <div className="p-2.5 bg-primary/10 text-primary rounded-xl">
                        <FileText size={20} />
                      </div>
                      <div className="min-w-0 flex-1">
                        <p className="text-xs font-medium truncate">{att.fileName}</p>
                        <p className="text-[10px] text-muted-foreground">{formatFileSize(att.fileSize)}</p>
                      </div>
                    </div>
                    <div className="flex items-center gap-2 px-1">
                      <Loader2 size={12} className="animate-spin text-primary" />
                      <span className="text-[11px] text-primary font-medium">
                        {t('attachments.analyzing') || 'Analyzing document...'}
                      </span>
                    </div>
                  </div>
                )}

                {att.status === 'ready' && (
                  <button
                    onClick={() => onOpenDocQA(att)}
                    className="w-full text-left p-5"
                  >
                    <div className="flex items-center gap-3 mb-4">
                      <div className="p-2.5 bg-primary/10 text-primary rounded-xl">
                        <FileText size={20} />
                      </div>
                      <div className="min-w-0 flex-1 pr-4">
                        <p className="text-xs font-medium truncate">{att.fileName}</p>
                        <p className="text-[10px] text-muted-foreground">
                          {formatFileSize(att.fileSize)}
                          {att.pageCount ? ` · ${att.pageCount} pages` : ''}
                        </p>
                      </div>
                    </div>
                    <div className="flex items-center gap-2 px-1">
                      <MessageSquare size={12} className="text-primary" />
                      <span className="text-[11px] text-primary font-medium">
                        {t('attachments.askQuestions') || 'Ask questions about this document'}
                      </span>
                    </div>
                  </button>
                )}

                {att.status === 'failed' && (
                  <div className="p-5">
                    <div className="flex items-center gap-3 mb-3">
                      <div className="p-2.5 bg-destructive/10 text-destructive rounded-xl">
                        <FileText size={20} />
                      </div>
                      <div className="min-w-0 flex-1">
                        <p className="text-xs font-medium truncate">{att.fileName}</p>
                        <p className="text-[10px] text-destructive">
                          {att.error || (t('attachments.processingFailed') || 'Processing failed')}
                        </p>
                      </div>
                    </div>
                  </div>
                )}
              </div>
            ))}
          </div>
        </div>
      )}

      {uploading && (
        <div className="flex items-center gap-2 text-xs text-muted-foreground pt-4">
          <Loader2 size={14} className="animate-spin" />
          <span>{t('attachments.uploading') || 'Uploading...'}</span>
        </div>
      )}
    </>
  )
}