backend/internal/middleware/cors.go

package middleware

import (
	"net/http"
	"strings"

	"github.com/gin-gonic/gin"
)

var allowedOrigins = []string{
	"https://bbs.littlelan.cn",
	"http://localhost:3000",
	"http://localhost:5173",
	"http://127.0.0.1:3000",
	"http://127.0.0.1:5173",
}

func CORS() gin.HandlerFunc {
	return func(c *gin.Context) {
		origin := c.GetHeader("Origin")
		allowedOrigin := ""

		for _, o := range allowedOrigins {
			if o == origin {
				allowedOrigin = o
				break
			}
		}

		if allowedOrigin == "" {
			if strings.HasPrefix(origin, "http://localhost") || strings.HasPrefix(origin, "http://127.0.0.1") {
				allowedOrigin = origin
			}
		}

		if allowedOrigin != "" {
			c.Header("Access-Control-Allow-Origin", allowedOrigin)
			c.Header("Access-Control-Allow-Credentials", "true")
		}

		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS")
		c.Header("Access-Control-Allow-Headers", "Origin, Content-Type, Accept, Authorization, Connection, Upgrade, Sec-WebSocket-Key, Sec-WebSocket-Version, Sec-WebSocket-Protocol, Sec-WebSocket-Extensions")
		c.Header("Access-Control-Expose-Headers", "Content-Length, Connection, Upgrade")

		if c.Request.Method == "OPTIONS" {
			c.AbortWithStatus(http.StatusNoContent)
			return
		}

		c.Next()
	}
}