(Feat): Initial Commit

internal/api/middleware/no_cache.go

@@ -0,0 +1,91 @@
+package middleware
+
+// Based on https://github.com/LYY/echo-middleware (MIT License, https://github.com/LYY/echo-middleware/blob/master/LICENSE)
+// Ported from Goji's middleware, source:
+// https://github.com/zenazn/goji/tree/master/web/middleware (MIT License, https://github.com/zenazn/goji/blob/master/LICENSE)
+
+import (
+	"time"
+
+	"github.com/labstack/echo/v4"
+	middleware "github.com/labstack/echo/v4/middleware"
+)
+
+type (
+	// NoCacheConfig defines the config for nocache middleware.
+	NoCacheConfig struct {
+		// Skipper defines a function to skip middleware.
+		Skipper middleware.Skipper
+	}
+)
+
+var (
+	// Unix epoch time
+	epoch = time.Unix(0, 0).Format(time.RFC1123)
+
+	// Taken from https://github.com/mytrile/nocache
+	noCacheHeaders = map[string]string{
+		"Expires":         epoch,
+		"Cache-Control":   "no-cache, private, max-age=0",
+		"Pragma":          "no-cache",
+		"X-Accel-Expires": "0",
+	}
+	etagHeaders = []string{
+		"ETag",
+		"If-Modified-Since",
+		"If-Match",
+		"If-None-Match",
+		"If-Range",
+		"If-Unmodified-Since",
+	}
+	// DefaultNoCacheConfig is the default nocache middleware config.
+	DefaultNoCacheConfig = NoCacheConfig{
+		Skipper: middleware.DefaultSkipper,
+	}
+)
+
+// NoCache is a simple piece of middleware that sets a number of HTTP headers to prevent
+// a router (or subrouter) from being cached by an upstream proxy and/or client.
+//
+// As per http://wiki.nginx.org/HttpProxyModule - NoCache sets:
+//
+//	Expires: Thu, 01 Jan 1970 00:00:00 UTC
+//	Cache-Control: no-cache, private, max-age=0
+//	X-Accel-Expires: 0
+//	Pragma: no-cache (for HTTP/1.0 proxies/clients)
+func NoCache() echo.MiddlewareFunc {
+	return NoCacheWithConfig(DefaultNoCacheConfig)
+}
+
+// NoCacheWithConfig returns a nocache middleware with config.
+func NoCacheWithConfig(config NoCacheConfig) echo.MiddlewareFunc {
+	// Defaults
+	if config.Skipper == nil {
+		config.Skipper = DefaultNoCacheConfig.Skipper
+	}
+
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			if config.Skipper(c) {
+				return next(c)
+			}
+
+			req := c.Request()
+
+			// Delete any ETag headers that may have been set
+			for _, v := range etagHeaders {
+				if req.Header.Get(v) != "" {
+					req.Header.Del(v)
+				}
+			}
+
+			// Set our NoCache headers
+			res := c.Response()
+			for k, v := range noCacheHeaders {
+				res.Header().Set(k, v)
+			}
+
+			return next(c)
+		}
+	}
+}