/
engine.go
92 lines (75 loc) · 2.15 KB
/
engine.go
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// Copyright 2021 The kbrew 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 engine
import (
"bytes"
"fmt"
"strings"
"text/template"
"github.com/pkg/errors"
"helm.sh/helm/v3/pkg/engine"
"k8s.io/client-go/rest"
)
const renderErr = "Error rendering value"
// Engine provides functionalities to evaluate and render templates.
type Engine struct {
config *rest.Config
fmap template.FuncMap
template *template.Template
}
// NewEngine returns an initialized Engine
func NewEngine(config *rest.Config) *Engine {
return &Engine{
template: template.New("gotpl"),
config: config,
}
}
// Render resolves values of a string template.
func (e *Engine) Render(arg string) (string, error) {
if len(e.fmap) == 0 {
e.initFuncMap()
}
_, err := e.template.Parse(arg)
if err != nil {
return "", errors.Wrapf(err, renderErr)
}
var tpl bytes.Buffer
err = e.template.Execute(&tpl, "")
if err != nil {
return "", errors.Wrapf(err, renderErr)
}
return tpl.String(), nil
}
func (e *Engine) initFuncMap() {
includedNames := make(map[string]int)
e.fmap = funcMap()
e.fmap["include"] = func(name string, data interface{}) (string, error) {
var buf strings.Builder
if v, ok := includedNames[name]; ok {
if v > 1000 {
return "", errors.Wrapf(fmt.Errorf("unable to execute template"), "rendering template has a nested reference name: %s", name)
}
includedNames[name]++
} else {
includedNames[name] = 1
}
err := e.template.ExecuteTemplate(&buf, name, data)
includedNames[name]--
return buf.String(), err
}
if e.config != nil {
e.fmap["lookup"] = engine.NewLookupFunction(e.config)
}
e.template.Funcs(e.fmap)
}