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render.go
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render.go
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// Copyright 2020 Google LLC
//
// 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 render defines rendering functionality.
package render
import (
"bytes"
"context"
"fmt"
htmltemplate "html/template"
"os"
"path/filepath"
"strings"
"sync"
texttemplate "text/template"
"github.com/google/exposure-notifications-server/pkg/logging"
"github.com/google/exposure-notifications-verification-server/internal/project"
"github.com/leonelquinteros/gotext"
"go.uber.org/zap"
)
// allowedResponseCodes are the list of allowed response codes. This is
// primarily here to catch if someone, in the future, accidentally includes a
// bad status code.
var allowedResponseCodes = map[int]struct{}{
200: {},
400: {},
401: {},
404: {},
405: {},
409: {},
412: {},
413: {},
429: {},
500: {},
}
// Renderer is responsible for rendering various content and templates like HTML
// and JSON responses.
type Renderer struct {
// debug indicates templates should be reloaded on each invocation and real
// error responses should be rendered. Do not enable in production.
debug bool
// logger is the log writer.
logger *zap.SugaredLogger
// rendererPool is a pool of *bytes.Buffer, used as a rendering buffer to
// prevent partial responses being sent to clients.
rendererPool *sync.Pool
// templates is the actually collection of templates. templatesLoader is a
// function for (re)loading templates. templatesLock is a mutex to prevent
// concurrent modification of the templates field.
templates *htmltemplate.Template
textTemplates *texttemplate.Template
templatesRoot string
}
// New creates a new renderer with the given details.
func New(ctx context.Context, root string, debug bool) (*Renderer, error) {
logger := logging.FromContext(ctx)
r := &Renderer{
debug: debug,
logger: logger,
rendererPool: &sync.Pool{
New: func() interface{} {
return bytes.NewBuffer(make([]byte, 0, 1024))
},
},
templatesRoot: root,
}
// Load initial templates
if err := r.loadTemplates(); err != nil {
return nil, err
}
return r, nil
}
// loadTemplates loads or reloads all templates.
func (r *Renderer) loadTemplates() error {
if r.templatesRoot == "" {
return nil
}
tmpl := htmltemplate.New("").
Option("missingkey=zero").
Funcs(templateFuncs())
txttmpl := texttemplate.New("").
Funcs(textFuncs())
if err := loadTemplates(tmpl, txttmpl, r.templatesRoot); err != nil {
return fmt.Errorf("failed to load templates: %w", err)
}
r.templates = tmpl
r.textTemplates = txttmpl
return nil
}
func loadTemplates(tmpl *htmltemplate.Template, txttmpl *texttemplate.Template, root string) error {
return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if info.IsDir() {
return nil
}
if strings.HasSuffix(info.Name(), ".html") {
if _, err := tmpl.ParseFiles(path); err != nil {
return fmt.Errorf("failed to parse %s: %w", path, err)
}
}
if strings.HasSuffix(info.Name(), ".txt") {
if _, err := txttmpl.ParseFiles(path); err != nil {
return fmt.Errorf("failed to parse %s: %w", path, err)
}
}
return nil
})
}
// safeHTML un-escapes known safe html.
func safeHTML(s string) htmltemplate.HTML {
return htmltemplate.HTML(s)
}
func selectedIf(v bool) htmltemplate.HTML {
if v {
return htmltemplate.HTML("selected")
}
return ""
}
// translate accepts a message printer (populated by middleware) and prints the
// translated text for the given key. If the printer is nil, an error is
// returned.
func translate(l *gotext.Locale, key string, vars ...interface{}) (string, error) {
if l == nil {
return "", fmt.Errorf("missing locale")
}
v := l.Get(key, vars...)
if v == "" || v == key {
return "", fmt.Errorf("unknown i18n key %q", key)
}
return v, nil
}
func templateFuncs() htmltemplate.FuncMap {
return map[string]interface{}{
"joinStrings": strings.Join,
"trimSpace": project.TrimSpace,
"stringContains": strings.Contains,
"toLower": strings.ToLower,
"toUpper": strings.ToUpper,
"safeHTML": safeHTML,
"selectedIf": selectedIf,
"t": translate,
"passwordSentinel": pwdSentinel,
}
}
func pwdSentinel() string {
return project.PasswordSentinel
}
func textFuncs() texttemplate.FuncMap {
return map[string]interface{}{
"trimSpace": project.TrimSpace,
}
}
// AllowedResponseCode returns true if the code is a permitted response code,
// false otherwise.
func (r *Renderer) AllowedResponseCode(code int) bool {
_, ok := allowedResponseCodes[code]
return ok
}