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// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package templates
import (
"bytes"
"fmt"
"io"
"net/http"
"strconv"
"strings"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
)
func init() {
caddy.RegisterModule(caddy.Module{
Name: "http.middleware.templates",
New: func() interface{} { return new(Templates) },
})
}
// Templates is a middleware which execute response bodies as templates.
type Templates struct {
FileRoot string `json:"file_root,omitempty"`
MIMETypes []string `json:"mime_types,omitempty"`
Delimiters []string `json:"delimiters,omitempty"`
}
// Provision provisions t.
func (t *Templates) Provision(ctx caddy.Context) error {
if t.MIMETypes == nil {
t.MIMETypes = defaultMIMETypes
}
return nil
}
// Validate ensures t has a valid configuration.
func (t *Templates) Validate() error {
if len(t.Delimiters) != 0 && len(t.Delimiters) != 2 {
return fmt.Errorf("delimiters must consist of exactly two elements: opening and closing")
}
return nil
}
func (t *Templates) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
buf := bufPool.Get().(*bytes.Buffer)
buf.Reset()
defer bufPool.Put(buf)
// shouldBuf determines whether to execute templates on this response,
// since generally we will not want to execute for images or CSS, etc.
shouldBuf := func(status int) bool {
ct := w.Header().Get("Content-Type")
for _, mt := range t.MIMETypes {
if strings.Contains(ct, mt) {
return true
}
}
return false
}
rec := caddyhttp.NewResponseRecorder(w, buf, shouldBuf)
err := next.ServeHTTP(rec, r)
if err != nil {
return err
}
if !rec.Buffered() {
return nil
}
err = t.executeTemplate(rec, r)
if err != nil {
return err
}
w.Header().Set("Content-Length", strconv.Itoa(buf.Len()))
w.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-created content
w.Header().Del("Last-Modified") // useless for dynamic content since it's always changing
// we don't know a way to guickly generate etag for dynamic content,
// but we can convert this to a weak etag to kind of indicate that
if etag := w.Header().Get("ETag"); etag != "" {
w.Header().Set("ETag", "W/"+etag)
}
w.WriteHeader(rec.Status())
io.Copy(w, buf)
return nil
}
// executeTemplate executes the template contained in wb.buf and replaces it with the results.
func (t *Templates) executeTemplate(rr caddyhttp.ResponseRecorder, r *http.Request) error {
var fs http.FileSystem
if t.FileRoot != "" {
fs = http.Dir(t.FileRoot)
}
ctx := &templateContext{
Root: fs,
Req: r,
RespHeader: tplWrappedHeader{rr.Header()},
config: t,
}
err := ctx.executeTemplateInBuffer(r.URL.Path, rr.Buffer())
if err != nil {
return caddyhttp.Error(http.StatusInternalServerError, err)
}
return nil
}
// virtualResponseWriter is used in virtualized HTTP requests
// that templates may execute.
type virtualResponseWriter struct {
status int
header http.Header
body *bytes.Buffer
}
func (vrw *virtualResponseWriter) Header() http.Header {
return vrw.header
}
func (vrw *virtualResponseWriter) WriteHeader(statusCode int) {
vrw.status = statusCode
}
func (vrw *virtualResponseWriter) Write(data []byte) (int, error) {
return vrw.body.Write(data)
}
var defaultMIMETypes = []string{
"text/html",
"text/plain",
"text/markdown",
}
// Interface guards
var (
_ caddy.Provisioner = (*Templates)(nil)
_ caddy.Validator = (*Templates)(nil)
_ caddyhttp.MiddlewareHandler = (*Templates)(nil)
)
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