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// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package scopedtmpl
import (
"fmt"
"html/template"
"io"
"reflect"
"sync"
texttemplate "text/template"
"text/template/parse"
"unsafe"
)
type TemplateExecutor interface {
Execute(wr io.Writer, data any) error
}
type ScopedTemplate struct {
all *template.Template
parseFuncs template.FuncMap // this func map is only used for parsing templates
frozen bool
scopedMu sync.RWMutex
scopedTemplateSets map[string]*scopedTemplateSet
}
func NewScopedTemplate() *ScopedTemplate {
return &ScopedTemplate{
all: template.New(""),
parseFuncs: template.FuncMap{},
scopedTemplateSets: map[string]*scopedTemplateSet{},
}
}
func (t *ScopedTemplate) Funcs(funcMap template.FuncMap) {
if t.frozen {
panic("cannot add new functions to frozen template set")
}
t.all.Funcs(funcMap)
for k, v := range funcMap {
t.parseFuncs[k] = v
}
}
func (t *ScopedTemplate) New(name string) *template.Template {
if t.frozen {
panic("cannot add new template to frozen template set")
}
return t.all.New(name)
}
func (t *ScopedTemplate) Freeze() {
t.frozen = true
// reset the exec func map, then `escapeTemplate` is safe to call `Execute` to do escaping
m := template.FuncMap{}
for k := range t.parseFuncs {
m[k] = func(v ...any) any { return nil }
}
t.all.Funcs(m)
}
func (t *ScopedTemplate) Executor(name string, funcMap template.FuncMap) (TemplateExecutor, error) {
t.scopedMu.RLock()
scopedTmplSet, ok := t.scopedTemplateSets[name]
t.scopedMu.RUnlock()
if !ok {
var err error
t.scopedMu.Lock()
if scopedTmplSet, ok = t.scopedTemplateSets[name]; !ok {
if scopedTmplSet, err = newScopedTemplateSet(t.all, name); err == nil {
t.scopedTemplateSets[name] = scopedTmplSet
}
}
t.scopedMu.Unlock()
if err != nil {
return nil, err
}
}
if scopedTmplSet == nil {
return nil, fmt.Errorf("template %s not found", name)
}
return scopedTmplSet.newExecutor(funcMap), nil
}
type scopedTemplateSet struct {
name string
htmlTemplates map[string]*template.Template
textTemplates map[string]*texttemplate.Template
execFuncs map[string]reflect.Value
}
func escapeTemplate(t *template.Template) error {
// force the Golang HTML template to complete the escaping work
err := t.Execute(io.Discard, nil)
if _, ok := err.(*template.Error); ok {
return err
}
return nil
}
//nolint:unused
type htmlTemplate struct {
escapeErr error
text *texttemplate.Template
}
//nolint:unused
type textTemplateCommon struct {
tmpl map[string]*template.Template // Map from name to defined templates.
muTmpl sync.RWMutex // protects tmpl
option struct {
missingKey int
}
muFuncs sync.RWMutex // protects parseFuncs and execFuncs
parseFuncs texttemplate.FuncMap
execFuncs map[string]reflect.Value
}
//nolint:unused
type textTemplate struct {
name string
*parse.Tree
*textTemplateCommon
leftDelim string
rightDelim string
}
func ptr[T, P any](ptr *P) *T {
// https://pkg.go.dev/unsafe#Pointer
// (1) Conversion of a *T1 to Pointer to *T2.
// Provided that T2 is no larger than T1 and that the two share an equivalent memory layout,
// this conversion allows reinterpreting data of one type as data of another type.
return (*T)(unsafe.Pointer(ptr))
}
func newScopedTemplateSet(all *template.Template, name string) (*scopedTemplateSet, error) {
targetTmpl := all.Lookup(name)
if targetTmpl == nil {
return nil, fmt.Errorf("template %q not found", name)
}
if err := escapeTemplate(targetTmpl); err != nil {
return nil, fmt.Errorf("template %q has an error when escaping: %w", name, err)
}
ts := &scopedTemplateSet{
name: name,
htmlTemplates: map[string]*template.Template{},
textTemplates: map[string]*texttemplate.Template{},
}
htmlTmpl := ptr[htmlTemplate](all)
textTmpl := htmlTmpl.text
textTmplPtr := ptr[textTemplate](textTmpl)
textTmplPtr.muFuncs.Lock()
ts.execFuncs = map[string]reflect.Value{}
for k, v := range textTmplPtr.execFuncs {
ts.execFuncs[k] = v
}
textTmplPtr.muFuncs.Unlock()
var collectTemplates func(nodes []parse.Node)
var collectErr error // only need to collect the one error
collectTemplates = func(nodes []parse.Node) {
for _, node := range nodes {
if node.Type() == parse.NodeTemplate {
nodeTemplate := node.(*parse.TemplateNode)
subName := nodeTemplate.Name
if ts.htmlTemplates[subName] == nil {
subTmpl := all.Lookup(subName)
if subTmpl == nil {
// HTML template will add some internal templates like "$delimDoubleQuote" into the text template
ts.textTemplates[subName] = textTmpl.Lookup(subName)
} else if subTmpl.Tree == nil || subTmpl.Tree.Root == nil {
collectErr = fmt.Errorf("template %q has no tree, it's usually caused by broken templates", subName)
} else {
ts.htmlTemplates[subName] = subTmpl
if err := escapeTemplate(subTmpl); err != nil {
collectErr = fmt.Errorf("template %q has an error when escaping: %w", subName, err)
return
}
collectTemplates(subTmpl.Tree.Root.Nodes)
}
}
} else if node.Type() == parse.NodeList {
nodeList := node.(*parse.ListNode)
collectTemplates(nodeList.Nodes)
} else if node.Type() == parse.NodeIf {
nodeIf := node.(*parse.IfNode)
collectTemplates(nodeIf.BranchNode.List.Nodes)
if nodeIf.BranchNode.ElseList != nil {
collectTemplates(nodeIf.BranchNode.ElseList.Nodes)
}
} else if node.Type() == parse.NodeRange {
nodeRange := node.(*parse.RangeNode)
collectTemplates(nodeRange.BranchNode.List.Nodes)
if nodeRange.BranchNode.ElseList != nil {
collectTemplates(nodeRange.BranchNode.ElseList.Nodes)
}
} else if node.Type() == parse.NodeWith {
nodeWith := node.(*parse.WithNode)
collectTemplates(nodeWith.BranchNode.List.Nodes)
if nodeWith.BranchNode.ElseList != nil {
collectTemplates(nodeWith.BranchNode.ElseList.Nodes)
}
}
}
}
ts.htmlTemplates[name] = targetTmpl
collectTemplates(targetTmpl.Tree.Root.Nodes)
return ts, collectErr
}
func (ts *scopedTemplateSet) newExecutor(funcMap map[string]any) TemplateExecutor {
tmpl := texttemplate.New("")
tmplPtr := ptr[textTemplate](tmpl)
tmplPtr.execFuncs = map[string]reflect.Value{}
for k, v := range ts.execFuncs {
tmplPtr.execFuncs[k] = v
}
if funcMap != nil {
tmpl.Funcs(funcMap)
}
// after escapeTemplate, the html templates are also escaped text templates, so it could be added to the text template directly
for _, t := range ts.htmlTemplates {
_, _ = tmpl.AddParseTree(t.Name(), t.Tree)
}
for _, t := range ts.textTemplates {
_, _ = tmpl.AddParseTree(t.Name(), t.Tree)
}
// now the text template has all necessary escaped templates, so we can safely execute, just like what the html template does
return tmpl.Lookup(ts.name)
}
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