feat: 🎸 add frontend gray plugin (#1120)

Co-authored-by: Kent Dong <ch3cho@qq.com>

plugins/wasm-go/extensions/frontend-gray/util/utils.go

@@ -0,0 +1,70 @@
+package util
+
+import (
+	"net/url"
+	"strings"
+
+	"github.com/alibaba/higress/plugins/wasm-go/extensions/frontend-gray/config"
+
+	"github.com/tidwall/gjson"
+)
+
+// GetValueByCookie 根据 cookieStr 和 cookieName 获取 cookie 值
+func GetValueByCookie(cookieStr string, cookieName string) string {
+	if cookieStr == "" {
+		return ""
+	}
+	cookies := strings.Split(cookieStr, ";")
+	curCookieName := cookieName + "="
+	var foundCookieValue string
+	var found bool
+	// 遍历找到 cookie 对并处理
+	for _, cookie := range cookies {
+		cookie = strings.TrimSpace(cookie) // 清理空白符
+		if strings.HasPrefix(cookie, curCookieName) {
+			foundCookieValue = cookie[len(curCookieName):]
+			found = true
+			break
+		}
+	}
+	if !found {
+		return ""
+	}
+	return foundCookieValue
+}
+
+// contains 检查切片 slice 中是否含有元素 value。
+func Contains(slice []interface{}, value string) bool {
+	for _, item := range slice {
+		if item == value {
+			return true
+		}
+	}
+	return false
+}
+
+func GetRule(rules []*config.GrayRule, name string) *config.GrayRule {
+	for _, rule := range rules {
+		if rule.Name == name {
+			return rule
+		}
+	}
+	return nil
+}
+
+func GetBySubKey(grayInfoStr string, graySubKey string) string {
+	// 首先对 URL 编码的字符串进行解码
+	jsonStr, err := url.QueryUnescape(grayInfoStr)
+	if err != nil {
+		return ""
+	}
+	// 使用 gjson 从 JSON 字符串中提取 graySubKey 对应的值
+	value := gjson.Get(jsonStr, graySubKey)
+
+	// 检查所提取的值是否存在
+	if !value.Exists() {
+		return ""
+	}
+	// 返回字符串形式的值
+	return value.String()
+}