Add command to render a Go template with config and state as data context

Signed-off-by: Denis Luchkin-Zhou <wyvernzora@gmail.com>

main.go

@@ -5,14 +5,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/kairos-io/kairos-agent/v2/pkg/action"
+	"github.com/kairos-io/kairos-agent/v2/pkg/utils"
 	"os"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"strings"
 
-	"github.com/kairos-io/kairos-agent/v2/pkg/utils"
-
 	"github.com/kairos-io/kairos-agent/v2/internal/agent"
 	"github.com/kairos-io/kairos-agent/v2/internal/bus"
 	"github.com/kairos-io/kairos-agent/v2/internal/common"
@@ -367,6 +367,38 @@ enabled: true`,
 			},
 		},
 	},
+	{
+		Name:        "render-template",
+		Usage:       "Render a Go template",
+		Description: "Render a Go template with machine state and config as data context",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:     "file",
+				Aliases:  []string{"f"},
+				Required: true,
+			},
+		},
+		Action: func(c *cli.Context) error {
+
+			config, err := agentConfig.Scan(collector.Directories(configScanDir...), collector.NoLogs, collector.StrictValidation(c.Bool("strict-validation")))
+			if err != nil {
+				return err
+			}
+
+			runtime, err := state.NewRuntime()
+			if err != nil {
+				return err
+			}
+
+			result, err := action.RenderTemplate(c.String("file"), config, runtime)
+			if err != nil {
+				return err
+			}
+
+			_, err = os.Stdout.Write(result)
+			return err
+		},
+	},
 	{
 		Name: "interactive-install",
 		Description: `

pkg/action/render_template.go

@@ -0,0 +1,60 @@
+/*
+Copyright © 2022 SUSE 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 action
+
+import (
+	"bytes"
+	"github.com/Masterminds/sprig/v3"
+	"github.com/kairos-io/kairos-agent/v2/pkg/config"
+	"github.com/kairos-io/kairos-sdk/state"
+	"gopkg.in/yaml.v3"
+	"os"
+	"text/template"
+)
+
+func RenderTemplate(path string, config *config.Config, runtime state.Runtime) ([]byte, error) {
+	// Marshal runtime to YAML then to Map so that it is consistent with the output of 'kairos-agent state'
+	var runtimeMap map[string]interface{}
+	err := yaml.Unmarshal([]byte(runtime.String()), &runtimeMap)
+	if err != nil {
+		return nil, err
+	}
+
+	tpl, err := loadTemplateFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	result := new(bytes.Buffer)
+	err = tpl.Execute(result, map[string]interface{}{
+		"Config": config.Config,
+		"State":  runtimeMap,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return result.Bytes(), nil
+}
+
+func loadTemplateFile(path string) (*template.Template, error) {
+	tpl := template.New(path).Funcs(sprig.FuncMap())
+	content, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	return tpl.Parse(string(content))
+}

pkg/action/render_template_test.go

@@ -0,0 +1,38 @@
+package action
+
+import (
+	"fmt"
+	agentConfig "github.com/kairos-io/kairos-agent/v2/pkg/config"
+	"github.com/kairos-io/kairos-sdk/collector"
+	"github.com/kairos-io/kairos-sdk/state"
+	"gopkg.in/yaml.v3"
+	"os"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("RenderTemplate action test", func() {
+
+	It("renders the template with config and state", func() {
+		config := agentConfig.NewConfig()
+		config.Config = collector.Config{
+			"testKey": "testValue",
+		}
+		runtime, err := state.NewRuntime()
+
+		fmt.Println(os.Getwd())
+
+		result, err := RenderTemplate("../../tests/fixtures/template/test.yaml", config, runtime)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(result).ToNot(BeNil())
+		Expect(len(result)).ToNot(BeZero())
+
+		var data map[string]string
+		err = yaml.Unmarshal(result, &data)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(data).To(HaveKeyWithValue("configTest", "TESTVALUE"))
+		Expect(data["stateTest"]).To(MatchRegexp("^[0-9a-f]{8}$"))
+	})
+
+})

tests/fixtures/template/test.yaml

@@ -0,0 +1,2 @@
+configTest: "{{.Config.testKey | upper}}"
+stateTest: "{{.State.uuid | trunc 8}}"