import React, { useEffect, useState } from 'react'
import {
  Table,
  TableBody,
  TableCell,
  TableHead,
  TableHeader,
  TableRow,
} from '@/components/ui/table'
import { ScrollArea, ScrollBar } from '@/components/ui/scroll-area'

export interface CsvPreviewProps {
  /** CSV 文件的远程 URL */
  url?: string
  /** 直接传入的 CSV 内容 */
  content?: string
}

function parseCsv(text: string): string[][] {
  const lines = text.split(/\r?\n/)
  return lines
    .filter(line => line.trim() !== '')
    .map(line => {
      const row: string[] = []
      let inQuotes = false
      let cell = ''
      for (let i = 0; i < line.length; i++) {
        const ch = line[i]
        if (ch === '"') {
          if (inQuotes && line[i + 1] === '"') {
            cell += '"'
            i++
          } else {
            inQuotes = !inQuotes
          }
        } else if (ch === ',' && !inQuotes) {
          row.push(cell)
          cell = ''
        } else {
          cell += ch
        }
      }
      row.push(cell)
      return row
    })
}

export function CsvPreview({ url, content }: CsvPreviewProps) {
  const [rows, setRows] = useState<string[][]>([])
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)

  useEffect(() => {
    let cancelled = false

    // 在异步回调里更新本地 state，避免在 effect 体内同步 setState
    queueMicrotask(() => {
      if (cancelled) return
      setLoading(true)
      setError(null)
    })

    if (content != null) {
      queueMicrotask(() => {
        if (cancelled) return
        setRows(parseCsv(content))
        setLoading(false)
      })

      return () => {
        cancelled = true
      }
    }

    if (!url) {
      queueMicrotask(() => {
        if (cancelled) return
        setRows([])
        setLoading(false)
      })

      return () => {
        cancelled = true
      }
    }

    fetch(url)
      .then(res => {
        if (!res.ok) throw new Error(`HTTP ${res.status}`)
        return res.text()
      })
      .then(text => {
        if (cancelled) return
        setRows(parseCsv(text))
      })
      .catch(err => {
        if (cancelled) return
        setError(err.message || '加载失败')
      })
      .finally(() => {
        if (cancelled) return
        setLoading(false)
      })

    return () => {
      cancelled = true
    }
  }, [content, url])

  if (loading) {
    return (
      <div className="flex items-center justify-center h-full text-muted-foreground">
        <div className="w-6 h-6 border-2 border-muted border-t-primary rounded-full animate-spin mr-2" />
        <span className="text-sm">加载中...</span>
      </div>
    )
  }

  if (error) {
    return (
      <div className="flex items-center justify-center h-full text-destructive text-sm">
        加载失败：{error}
      </div>
    )
  }

  if (rows.length === 0) {
    return (
      <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
        文件为空
      </div>
    )
  }

  const [header, ...body] = rows
  const colCount = Math.max(...rows.map(r => r.length))
  const paddedHeader = header.concat(Array(colCount - header.length).fill(''))

  return (
    <ScrollArea className="w-full h-full">
      <div className="p-4">
        <Table>
          <TableHeader>
            <TableRow>
              {paddedHeader.map((col, i) => (
                <TableHead key={i} className="whitespace-nowrap font-medium text-foreground">
                  {col || `列 ${i + 1}`}
                </TableHead>
              ))}
            </TableRow>
          </TableHeader>
          <TableBody>
            {body.map((row, ri) => {
              const paddedRow = row.concat(Array(colCount - row.length).fill(''))
              return (
                <TableRow key={ri}>
                  {paddedRow.map((cell, ci) => (
                    <TableCell key={ci} className="whitespace-nowrap text-sm">
                      {cell}
                    </TableCell>
                  ))}
                </TableRow>
              )
            })}
          </TableBody>
        </Table>
      </div>
      <ScrollBar orientation="horizontal" />
    </ScrollArea>
  )
}