feat: render compose file as a Go template

docs/stacks.yaml

@@ -13,5 +13,13 @@ stack-name:
   branch: main
   # The path to the docker compose file where stack
   # is defined
-  compose_file: compose.yaml
+  compose_file: /path/to/compose.yaml
+  # Path to values file to use when rendering
+  # compose file as a Go template. If empty, compose
+  # file will be treated as a regular compose file 
+  values_file: /path/to/values.yaml
+  # Paths to files encrypted using sops to decrypt
+  # before updating stack
+  sops_files:
+    - path/to/sops/encrypted/file
 

swarmcd/swarmcd.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path"
 	"sync"
+	"text/template"
 	"time"
 
 	"github.com/docker/cli/cli/command/stack"
@@ -61,6 +62,11 @@ func updateStack(stackName string) (revision string, err error) {
 		return "", fmt.Errorf("failed to decrypt one or more sops files for %s stack: %w", stackName, err)
 	}
 
+	err = renderComposeTemplate(stackName) 
+	if err != nil {
+		return
+	}
+
 	err = rotateConfigsAndSecrets(stackName) 
 	if err != nil {
 		return
@@ -206,6 +212,37 @@ func rotateObjects(objects map[string]any, objectsDir string, stackName string)
 	return nil
 }
 
+
+func renderComposeTemplate(stackName string) error {
+	stackConfig := config.StackConfigs[stackName]
+	if stackConfig.ValuesFile == "" {
+		return nil
+	}
+	composeFile := path.Join(config.ReposPath, stackConfig.Repo, stackConfig.ComposeFile)
+	valuesFile := path.Join(config.ReposPath, stackConfig.Repo, stackConfig.ValuesFile)
+	valuesBytes, err := os.ReadFile(valuesFile)
+	if err != nil {
+		return fmt.Errorf("could not read %s stack values file: %w", stackName, err)
+	}
+	var valuesMap map[string]any 
+	yaml.Unmarshal(valuesBytes, &valuesMap) 
+	templ, err := template.New(path.Base(composeFile)).ParseFiles(composeFile)
+	if err != nil {
+		return fmt.Errorf("could not parse %s stack compose file as a Go template: %w", stackName, err)
+	}
+	composeFileWriter, err := os.Create(composeFile)
+	if err != nil {
+		return fmt.Errorf("could not open %s stack compose file: %w",stackName, err)
+	}
+	err = templ.Execute(composeFileWriter, map[string]map[string]any{"Values": valuesMap})
+	if err != nil {
+		return fmt.Errorf("error rending %s stack compose template: %w", stackName, err)
+	}
+	return nil
+}
+
+
+
 func GetStackStatus() map[string]*StackStatus {
 	return stackStatus
 }

util/config.go

@@ -11,6 +11,7 @@ type StackConfig struct {
 	Repo        string
 	Branch      string
 	ComposeFile string   `mapstructure:"compose_file"`
+	ValuesFile  string   `mapstructure:"values_file"`
 	SopsFiles   []string `mapstructure:"sops_files"`
 }