From 073f0f3b3d03333a04ab572d09b099388fad2e19 Mon Sep 17 00:00:00 2001
From: Kirill Sysoev <k.sysoev@me.com>
Date: Mon, 15 Jan 2024 21:41:30 +0800
Subject: [PATCH] Adds middleware for detecting client ip

---
 middleware/http/clientip.go | 78 +++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 middleware/http/clientip.go

diff --git a/middleware/http/clientip.go b/middleware/http/clientip.go
new file mode 100644
index 0000000..c2062d4
--- /dev/null
+++ b/middleware/http/clientip.go
@@ -0,0 +1,78 @@
+package http
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"strings"
+)
+
+type ContextKey uint
+
+const (
+	ClientIP ContextKey = iota
+)
+
+type Provider uint8
+
+const (
+	NotProvided Provider = iota
+	Cloudflare
+	CloudFront
+)
+
+func NewClientIPMiddleware(provider Provider) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ip := getIPFromRequest(provider, r)
+
+			ctx := r.Context()
+			ctx = context.WithValue(ctx, ClientIP, ip)
+			r = r.WithContext(ctx)
+
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
+func getIPFromRequest(provider Provider, r *http.Request) string {
+	var ip string
+
+	switch provider {
+	case Cloudflare:
+		ip = r.Header.Get("True-Client-IP")
+		if ip == "" {
+			ip = r.Header.Get("CF-Connecting-IP")
+		}
+	case CloudFront:
+		ip = r.Header.Get("CloudFront-Viewer-Address")
+		if ip != "" {
+			parts := strings.Split(ip, ":")
+			if len(parts) > 0 {
+				ip = parts[0]
+			}
+		}
+	default:
+	}
+
+	if ip != "" {
+		return ip
+	}
+
+	if ip := r.Header.Get("X-Real-Ip"); ip != "" {
+		return ip
+	}
+
+	if ip := r.Header.Get("X-Forwarded-For"); ip != "" {
+		parts := strings.Split(ip, ",")
+		if len(parts) > 0 {
+			return parts[0]
+		}
+	}
+
+	if ip, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
+		return ip
+	}
+
+	return ""
+}