Use standard HTTP library to serve files (#24693)

`http.ServeFile/ServeContent` handles `If-xxx`, `Content-Length`,
`Range` and `Etag` correctly

After this PR, storage files (eg: avatar) could be responded with
correct Content-Length.

6 files changed, 14 insertions, 140 deletions

diff --git a/modules/context/context_test.go b/modules/context/context_test.go
index a6facc9788..033ce2ef0a 100644
--- a/modules/context/context_test.go
+++ b/modules/context/context_test.go
@@ -5,16 +5,16 @@ package context
 
 import (
 	"net/http"
+	"net/http/httptest"
 	"testing"
 
-	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/stretchr/testify/assert"
 )
 
 func TestRemoveSessionCookieHeader(t *testing.T) {
-	w := httplib.NewMockResponseWriter()
+	w := httptest.NewRecorder()
 	w.Header().Add("Set-Cookie", (&http.Cookie{Name: setting.SessionConfig.CookieName, Value: "foo"}).String())
 	w.Header().Add("Set-Cookie", (&http.Cookie{Name: "other", Value: "bar"}).String())
 	assert.Len(t, w.Header().Values("Set-Cookie"), 2)
diff --git a/modules/httpcache/httpcache.go b/modules/httpcache/httpcache.go
index 46e0152ef4..001ac06415 100644
--- a/modules/httpcache/httpcache.go
+++ b/modules/httpcache/httpcache.go
@@ -4,10 +4,8 @@
 package httpcache
 
 import (
-	"encoding/base64"
-	"fmt"
+	"io"
 	"net/http"
-	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -37,38 +35,9 @@ func SetCacheControlInHeader(h http.Header, maxAge time.Duration, additionalDire
 	h.Set("Cache-Control", strings.Join(append(directives, additionalDirectives...), ", "))
 }
 
-// generateETag generates an ETag based on size, filename and file modification time
-func generateETag(fi os.FileInfo) string {
-	etag := fmt.Sprint(fi.Size()) + fi.Name() + fi.ModTime().UTC().Format(http.TimeFormat)
-	return `"` + base64.StdEncoding.EncodeToString([]byte(etag)) + `"`
-}
-
-// HandleTimeCache handles time-based caching for a HTTP request
-func HandleTimeCache(req *http.Request, w http.ResponseWriter, fi os.FileInfo) (handled bool) {
-	return HandleGenericTimeCache(req, w, fi.ModTime())
-}
-
-// HandleGenericTimeCache handles time-based caching for a HTTP request
-func HandleGenericTimeCache(req *http.Request, w http.ResponseWriter, lastModified time.Time) (handled bool) {
+func ServeContentWithCacheControl(w http.ResponseWriter, req *http.Request, name string, modTime time.Time, content io.ReadSeeker) {
 	SetCacheControlInHeader(w.Header(), setting.StaticCacheTime)
-
-	ifModifiedSince := req.Header.Get("If-Modified-Since")
-	if ifModifiedSince != "" {
-		t, err := time.Parse(http.TimeFormat, ifModifiedSince)
-		if err == nil && lastModified.Unix() <= t.Unix() {
-			w.WriteHeader(http.StatusNotModified)
-			return true
-		}
-	}
-
-	w.Header().Set("Last-Modified", lastModified.Format(http.TimeFormat))
-	return false
-}
-
-// HandleFileETagCache handles ETag-based caching for a HTTP request
-func HandleFileETagCache(req *http.Request, w http.ResponseWriter, fi os.FileInfo) (handled bool) {
-	etag := generateETag(fi)
-	return HandleGenericETagCache(req, w, etag)
+	http.ServeContent(w, req, name, modTime, content)
 }
 
 // HandleGenericETagCache handles ETag-based caching for a HTTP request.
diff --git a/modules/httpcache/httpcache_test.go b/modules/httpcache/httpcache_test.go
index 624d2f4d4b..d81f06097c 100644
--- a/modules/httpcache/httpcache_test.go
+++ b/modules/httpcache/httpcache_test.go
@@ -6,23 +6,12 @@ package httpcache
 import (
 	"net/http"
 	"net/http/httptest"
-	"os"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/assert"
 )
 
-type mockFileInfo struct{}
-
-func (m mockFileInfo) Name() string       { return "gitea.test" }
-func (m mockFileInfo) Size() int64        { return int64(10) }
-func (m mockFileInfo) Mode() os.FileMode  { return os.ModePerm }
-func (m mockFileInfo) ModTime() time.Time { return time.Time{} }
-func (m mockFileInfo) IsDir() bool        { return false }
-func (m mockFileInfo) Sys() interface{}   { return nil }
-
 func countFormalHeaders(h http.Header) (c int) {
 	for k := range h {
 		// ignore our headers for internal usage
@@ -34,52 +23,6 @@ func countFormalHeaders(h http.Header) (c int) {
 	return c
 }
 
-func TestHandleFileETagCache(t *testing.T) {
-	fi := mockFileInfo{}
-	etag := `"MTBnaXRlYS50ZXN0TW9uLCAwMSBKYW4gMDAwMSAwMDowMDowMCBHTVQ="`
-
-	t.Run("No_If-None-Match", func(t *testing.T) {
-		req := &http.Request{Header: make(http.Header)}
-		w := httptest.NewRecorder()
-
-		handled := HandleFileETagCache(req, w, fi)
-
-		assert.False(t, handled)
-		assert.Equal(t, 2, countFormalHeaders(w.Header()))
-		assert.Contains(t, w.Header(), "Cache-Control")
-		assert.Contains(t, w.Header(), "Etag")
-		assert.Equal(t, etag, w.Header().Get("Etag"))
-	})
-	t.Run("Wrong_If-None-Match", func(t *testing.T) {
-		req := &http.Request{Header: make(http.Header)}
-		w := httptest.NewRecorder()
-
-		req.Header.Set("If-None-Match", `"wrong etag"`)
-
-		handled := HandleFileETagCache(req, w, fi)
-
-		assert.False(t, handled)
-		assert.Equal(t, 2, countFormalHeaders(w.Header()))
-		assert.Contains(t, w.Header(), "Cache-Control")
-		assert.Contains(t, w.Header(), "Etag")
-		assert.Equal(t, etag, w.Header().Get("Etag"))
-	})
-	t.Run("Correct_If-None-Match", func(t *testing.T) {
-		req := &http.Request{Header: make(http.Header)}
-		w := httptest.NewRecorder()
-
-		req.Header.Set("If-None-Match", etag)
-
-		handled := HandleFileETagCache(req, w, fi)
-
-		assert.True(t, handled)
-		assert.Equal(t, 1, countFormalHeaders(w.Header()))
-		assert.Contains(t, w.Header(), "Etag")
-		assert.Equal(t, etag, w.Header().Get("Etag"))
-		assert.Equal(t, http.StatusNotModified, w.Code)
-	})
-}
-
 func TestHandleGenericETagCache(t *testing.T) {
 	etag := `"test"`
 
diff --git a/modules/httplib/mock.go b/modules/httplib/mock.go
deleted file mode 100644
index 7d284e86fb..0000000000
--- a/modules/httplib/mock.go
+++ /dev/null
@@ -1,35 +0,0 @@
-// Copyright 2023 The Gitea Authors. All rights reserved.
-// SPDX-License-Identifier: MIT
-
-package httplib
-
-import (
-	"bytes"
-	"net/http"
-)
-
-type MockResponseWriter struct {
-	header http.Header
-
-	StatusCode int
-	BodyBuffer bytes.Buffer
-}
-
-func (m *MockResponseWriter) Header() http.Header {
-	return m.header
-}
-
-func (m *MockResponseWriter) Write(bytes []byte) (int, error) {
-	if m.StatusCode == 0 {
-		m.StatusCode = http.StatusOK
-	}
-	return m.BodyBuffer.Write(bytes)
-}
-
-func (m *MockResponseWriter) WriteHeader(statusCode int) {
-	m.StatusCode = statusCode
-}
-
-func NewMockResponseWriter() *MockResponseWriter {
-	return &MockResponseWriter{header: http.Header{}}
-}
diff --git a/modules/httplib/serve_test.go b/modules/httplib/serve_test.go
index 0768f1c713..fed4611d21 100644
--- a/modules/httplib/serve_test.go
+++ b/modules/httplib/serve_test.go
@@ -6,6 +6,7 @@ package httplib
 import (
 	"fmt"
 	"net/http"
+	"net/http/httptest"
 	"net/url"
 	"os"
 	"strings"
@@ -25,12 +26,12 @@ func TestServeContentByReader(t *testing.T) {
 			r.Header.Set("Range", fmt.Sprintf("bytes=%s", rangeStr))
 		}
 		reader := strings.NewReader(data)
-		w := NewMockResponseWriter()
+		w := httptest.NewRecorder()
 		ServeContentByReader(r, w, "test", int64(len(data)), reader)
-		assert.Equal(t, expectedStatusCode, w.StatusCode)
+		assert.Equal(t, expectedStatusCode, w.Code)
 		if expectedStatusCode == http.StatusPartialContent || expectedStatusCode == http.StatusOK {
 			assert.Equal(t, fmt.Sprint(len(expectedContent)), w.Header().Get("Content-Length"))
-			assert.Equal(t, expectedContent, w.BodyBuffer.String())
+			assert.Equal(t, expectedContent, w.Body.String())
 		}
 	}
 
@@ -76,12 +77,12 @@ func TestServeContentByReadSeeker(t *testing.T) {
 		}
 		defer seekReader.Close()
 
-		w := NewMockResponseWriter()
+		w := httptest.NewRecorder()
 		ServeContentByReadSeeker(r, w, "test", time.Time{}, seekReader)
-		assert.Equal(t, expectedStatusCode, w.StatusCode)
+		assert.Equal(t, expectedStatusCode, w.Code)
 		if expectedStatusCode == http.StatusPartialContent || expectedStatusCode == http.StatusOK {
 			assert.Equal(t, fmt.Sprint(len(expectedContent)), w.Header().Get("Content-Length"))
-			assert.Equal(t, expectedContent, w.BodyBuffer.String())
+			assert.Equal(t, expectedContent, w.Body.String())
 		}
 	}
 
diff --git a/modules/public/public.go b/modules/public/public.go
index 0c0e6dc1cc..ed38d85cfa 100644
--- a/modules/public/public.go
+++ b/modules/public/public.go
@@ -97,10 +97,6 @@ func handleRequest(w http.ResponseWriter, req *http.Request, fs http.FileSystem,
 		return true
 	}
 
-	if httpcache.HandleFileETagCache(req, w, fi) {
-		return true
-	}
-
 	serveContent(w, req, fi, fi.ModTime(), f)
 	return true
 }
@@ -124,11 +120,11 @@ func serveContent(w http.ResponseWriter, req *http.Request, fi os.FileInfo, modt
 				w.Header().Set("Content-Type", "application/octet-stream")
 			}
 			w.Header().Set("Content-Encoding", "gzip")
-			http.ServeContent(w, req, fi.Name(), modtime, rdGzip)
+			httpcache.ServeContentWithCacheControl(w, req, fi.Name(), modtime, rdGzip)
 			return
 		}
 	}
 
-	http.ServeContent(w, req, fi.Name(), modtime, content)
+	httpcache.ServeContentWithCacheControl(w, req, fi.Name(), modtime, content)
 	return
 }