imgproxy/fetcher/transport/notmodified/notmodified.go

package notmodified

import (
	"net/http"
	"time"

	"github.com/imgproxy/imgproxy/v3/httpheaders"
)

func Response(req *http.Request, header http.Header) *http.Response {
	etag := header.Get(httpheaders.Etag)
	ifNoneMatch := req.Header.Get(httpheaders.IfNoneMatch)

	if len(ifNoneMatch) > 0 && ifNoneMatch == etag {
		return response(req, header)
	}

	lastModifiedRaw := header.Get(httpheaders.LastModified)
	if len(lastModifiedRaw) == 0 {
		return nil
	}
	ifModifiedSinceRaw := req.Header.Get(httpheaders.IfModifiedSince)
	if len(ifModifiedSinceRaw) == 0 {
		return nil
	}
	lastModified, err := time.Parse(http.TimeFormat, lastModifiedRaw)
	if err != nil {
		return nil
	}
	ifModifiedSince, err := time.Parse(http.TimeFormat, ifModifiedSinceRaw)
	if err != nil {
		return nil
	}
	if !ifModifiedSince.Before(lastModified) {
		return response(req, header)
	}

	return nil
}

func response(req *http.Request, header http.Header) *http.Response {
	return &http.Response{
		StatusCode:    http.StatusNotModified,
		Proto:         "HTTP/1.0",
		ProtoMajor:    1,
		ProtoMinor:    0,
		Header:        header,
		ContentLength: 0,
		Body:          nil,
		Close:         false,
		Request:       req,
	}
}