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package templates
import (
"bytes"
"fmt"
"io"
"net/http"
"strconv"
"text/template"
"github.com/caddyserver/caddy"
"github.com/caddyserver/caddy/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"`
Delimiters []string `json:"delimiters,omitempty"`
}
// 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)
wb := &responseBuffer{
ResponseWriterWrapper: &caddyhttp.ResponseWriterWrapper{ResponseWriter: w},
buf: buf,
}
err := next.ServeHTTP(wb, r)
if err != nil {
return err
}
err = t.executeTemplate(wb, r)
if err != nil {
return err
}
w.Header().Set("Content-Length", strconv.Itoa(wb.buf.Len()))
w.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-created content
w.Header().Del("Etag") // don't know a way to quickly generate etag for dynamic content
w.Header().Del("Last-Modified") // useless for dynamic content since it's always changing
w.WriteHeader(wb.statusCode)
io.Copy(w, wb.buf)
return nil
}
// executeTemplate executes the template contianed
// in wb.buf and replaces it with the results.
func (t *Templates) executeTemplate(wb *responseBuffer, r *http.Request) error {
tpl := template.New(r.URL.Path)
if len(t.Delimiters) == 2 {
tpl.Delims(t.Delimiters[0], t.Delimiters[1])
}
parsedTpl, err := tpl.Parse(wb.buf.String())
if err != nil {
return caddyhttp.Error(http.StatusInternalServerError, err)
}
var fs http.FileSystem
if t.FileRoot != "" {
fs = http.Dir(t.FileRoot)
}
ctx := &templateContext{
Root: fs,
Req: r,
RespHeader: tplWrappedHeader{wb.Header()},
}
wb.buf.Reset() // reuse buffer for output
err = parsedTpl.Execute(wb.buf, ctx)
if err != nil {
return caddyhttp.Error(http.StatusInternalServerError, err)
}
return nil
}
// responseBuffer buffers the response so that it can be
// executed as a template.
type responseBuffer struct {
*caddyhttp.ResponseWriterWrapper
wroteHeader bool
statusCode int
buf *bytes.Buffer
}
func (rb *responseBuffer) WriteHeader(statusCode int) {
if rb.wroteHeader {
return
}
rb.statusCode = statusCode
rb.wroteHeader = true
}
func (rb *responseBuffer) Write(data []byte) (int, error) {
rb.WriteHeader(http.StatusOK)
return rb.buf.Write(data)
}
// virtualResponseWriter is used in virtualized HTTP requests.
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)
}
// Interface guards
var (
_ caddy.Validator = (*Templates)(nil)
_ caddyhttp.MiddlewareHandler = (*Templates)(nil)
_ caddyhttp.HTTPInterfaces = (*responseBuffer)(nil)
)
|
