nezha_dash/components/ServerFlag.tsx

import getEnv from "@/lib/env-entry"
import { cn } from "@/lib/utils"
import getUnicodeFlagIcon from "country-flag-icons/unicode"
import { useEffect, useState } from "react"

export default function ServerFlag({
  country_code,
  className,
}: {
  country_code: string
  className?: string
}) {
  const [supportsEmojiFlags, setSupportsEmojiFlags] = useState(false)

  const useSvgFlag = getEnv("NEXT_PUBLIC_ForceUseSvgFlag") === "true"

  useEffect(() => {
    if (useSvgFlag) {
      // 如果环境变量要求直接使用 SVG，则无需检查 Emoji 支持
      setSupportsEmojiFlags(false)
      return
    }

    const checkEmojiSupport = () => {
      const canvas = document.createElement("canvas")
      const ctx = canvas.getContext("2d")
      const emojiFlag = "🇺🇸" // 使用美国国旗作为测试
      if (!ctx) return
      ctx.fillStyle = "#000"
      ctx.textBaseline = "top"
      ctx.font = "32px Arial"
      ctx.fillText(emojiFlag, 0, 0)

      const support = ctx.getImageData(16, 16, 1, 1).data[3] !== 0
      setSupportsEmojiFlags(support)
    }

    checkEmojiSupport()
  }, [useSvgFlag]) // 将 `useSvgFlag` 作为依赖，当其变化时重新触发

  if (!country_code) return null

  if (supportsEmojiFlags && country_code.toLowerCase() === "tw") {
    country_code = "cn"
  }

  return (
    <span className={cn("text-[12px] text-muted-foreground", className)}>
      {useSvgFlag || !supportsEmojiFlags ? (
        <span className={`fi fi-${country_code}`} />
      ) : (
        getUnicodeFlagIcon(country_code)
      )}
    </span>
  )
}