package middleware

import (
	"net/http"

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

// GinCORSWhitelist Gin CORS白名单配置
type GinCORSWhitelist struct {
	AllowOrigin      string
	AllowHeaders     string
	AllowMethods     string
	ExposeHeaders    string
	AllowCredentials bool
}

// GinCORSConfig Gin CORS配置
type GinCORSConfig struct {
	// Mode 模式: allow-all, whitelist, strict-whitelist
	Mode      string
	Whitelist []GinCORSWhitelist
}

// 全局CORS配置
var ginCorsConfig *GinCORSConfig

// SetGinCORSConfig 设置Gin CORS配置
func SetGinCORSConfig(cfg *GinCORSConfig) {
	ginCorsConfig = cfg
}

// CorsByRules 按照配置处理跨域请求（与 kra 保持一致）
func CorsByRules() gin.HandlerFunc {
	// 放行全部
	if ginCorsConfig == nil || ginCorsConfig.Mode == "allow-all" {
		return Cors()
	}

	return func(c *gin.Context) {
		origin := c.GetHeader("origin")
		whitelist := checkGinCors(origin)

		// 通过检查, 添加请求头
		if whitelist != nil {
			c.Header("Access-Control-Allow-Origin", whitelist.AllowOrigin)
			c.Header("Access-Control-Allow-Headers", whitelist.AllowHeaders)
			c.Header("Access-Control-Allow-Methods", whitelist.AllowMethods)
			c.Header("Access-Control-Expose-Headers", whitelist.ExposeHeaders)
			if whitelist.AllowCredentials {
				c.Header("Access-Control-Allow-Credentials", "true")
			}
		}

		// 严格白名单模式且未通过检查，直接拒绝处理请求
		if whitelist == nil && ginCorsConfig.Mode == "strict-whitelist" {
			// 健康检查放行
			if !(c.Request.Method == "GET" && c.Request.URL.Path == "/health") {
				c.AbortWithStatus(http.StatusForbidden)
				return
			}
		} else {
			// 非严格白名单模式，无论是否通过检查均放行所有 OPTIONS 方法
			if c.Request.Method == http.MethodOptions {
				c.AbortWithStatus(http.StatusNoContent)
				return
			}
		}

		// 处理请求
		c.Next()
	}
}

func checkGinCors(currentOrigin string) *GinCORSWhitelist {
	if ginCorsConfig == nil {
		return nil
	}
	for _, whitelist := range ginCorsConfig.Whitelist {
		// 遍历配置中的跨域头，寻找匹配项
		if currentOrigin == whitelist.AllowOrigin {
			return &whitelist
		}
	}
	return nil
}