StackWithResources: Update ComposeYML behaviour

Previously, there was a function to manually read bytes for a
docker-compose.yml. But this proved to be akward at runtime.

Instead, this code automatically reads an existing docker-compose.yml,
and takes care of marshalling and unmarshalling.

go.mod

@@ -16,7 +16,7 @@ require (
 	github.com/pquerna/otp v1.4.0
 	github.com/rs/zerolog v1.29.1
 	github.com/tkw1536/goprogram v0.3.5
-	github.com/tkw1536/pkglib v0.0.0-20230713130635-2bcbc40ecdd9
+	github.com/tkw1536/pkglib v0.0.0-20230714124712-ccf0c3658789
 	github.com/yuin/goldmark v1.5.4
 	github.com/yuin/goldmark-meta v1.1.0
 	golang.org/x/crypto v0.8.0

go.sum

@@ -114,8 +114,8 @@ github.com/tdewolff/parse v2.3.4+incompatible/go.mod h1:8oBwCsVmUkgHO8M5iCzSIDtp
 github.com/tdewolff/test v1.0.7 h1:8Vs0142DmPFW/bQeHRP3MV19m1gvndjUb1sn8yy74LM=
 github.com/tkw1536/goprogram v0.3.5 h1:S0axKo3R/vGa4zhYqYDKAZEPhAfwUSSeMtVwnAu4sNY=
 github.com/tkw1536/goprogram v0.3.5/go.mod h1:pYr4dMHOSVurbPQ4KTR0ett8XWNISbsRS6zlh9Nsxa8=
-github.com/tkw1536/pkglib v0.0.0-20230713130635-2bcbc40ecdd9 h1:l+xh6dn9PW+HNYrIXgwsOileuIhkdxZocOicQfBdB9M=
-github.com/tkw1536/pkglib v0.0.0-20230713130635-2bcbc40ecdd9/go.mod h1:0A1B9Cc5+yJXR3eeB14CqD4dFSbEjjWRo5Pr9M3XYuI=
+github.com/tkw1536/pkglib v0.0.0-20230714124712-ccf0c3658789 h1:S6pXBfW8SJsN/MZEyhSbziV3F59P4VoddviiE5oPFoU=
+github.com/tkw1536/pkglib v0.0.0-20230714124712-ccf0c3658789/go.mod h1:0A1B9Cc5+yJXR3eeB14CqD4dFSbEjjWRo5Pr9M3XYuI=
 github.com/xeipuuv/gojsonpointer v0.0.0-20180127040702-4e3ac2762d5f/go.mod h1:N2zxlSyiKSe5eX1tZViRH5QA0qijqEDrYZiPEAiq3wU=
 github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb h1:zGWFAtiMcyryUHoUjUJX0/lt1H2+i2Ka2n+D3DImSNo=
 github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb/go.mod h1:N2zxlSyiKSe5eX1tZViRH5QA0qijqEDrYZiPEAiq3wU=

internal/dis/component/binder/binder.go

@@ -1,15 +1,12 @@
 package binder
 
 import (
-	"bytes"
-	"io"
+	"embed"
 	"path/filepath"
 
 	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
 	"github.com/tkw1536/pkglib/yamlx"
 	"gopkg.in/yaml.v3"
-
-	_ "embed"
 )
 
 type Binder struct {
@@ -29,52 +26,25 @@ func (binder *Binder) Context(parent component.InstallationContext) component.In
 }
 
 //go:embed docker-compose.yml
-var composeTemplate []byte
-
-func (binder *Binder) buildYML() ([]byte, error) {
-	var dockerCompose yaml.Node
-	if err := yaml.Unmarshal(composeTemplate, &dockerCompose); err != nil {
-		return nil, err
-	}
-
-	for dockerCompose.Kind == yaml.DocumentNode {
-		dockerCompose = *dockerCompose.Content[0]
-	}
-
-	{
-		ports := binder.Config.Listen.ComposePorts("8000")
-		portsNode, err := yamlx.Marshal(ports)
-		if err != nil {
-			return nil, err
-		}
-		if err := yamlx.Replace(&dockerCompose, *portsNode, "services", "binder", "ports"); err != nil {
-			return nil, err
-		}
-	}
-
-	{
-		command := binder.Config.HTTP.TCPMuxCommand("0.0.0.0:8000", "http:80", "http:443", "ssh:2222")
-		commandNode, err := yamlx.Marshal(command)
-		if err != nil {
-			return nil, err
-		}
-		if err := yamlx.Replace(&dockerCompose, *commandNode, "services", "binder", "command"); err != nil {
-			return nil, err
-		}
-	}
-
-	// do the final marshal
-	return yaml.Marshal(dockerCompose)
-}
+var composeTemplate embed.FS
 
 func (binder *Binder) Stack() component.StackWithResources {
 	return component.MakeStack(binder, component.StackWithResources{
-		ReadComposeFile: func() (io.Reader, error) {
-			data, err := binder.buildYML()
-			if err != nil {
+		ContextPath: ".",
+		Resources:   composeTemplate,
+
+		ComposerYML: func(root *yaml.Node) (*yaml.Node, error) {
+			ports := binder.Config.Listen.ComposePorts("8000")
+			if err := yamlx.ReplaceWith(root, ports, "services", "binder", "ports"); err != nil {
 				return nil, err
 			}
-			return bytes.NewReader(data), nil
+
+			command := binder.Config.HTTP.TCPMuxCommand("0.0.0.0:8000", "http:80", "http:443", "ssh:2222")
+			if err := yamlx.ReplaceWith(root, command, "services", "binder", "command"); err != nil {
+				return nil, err
+			}
+
+			return root, nil
 		},
 
 		EnvContext: map[string]string{

internal/dis/component/stack.go

@@ -15,6 +15,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/tkw1536/pkglib/fsx/umaskfree"
 	"github.com/tkw1536/pkglib/stream"
+	"gopkg.in/yaml.v3"
 )
 
 // Stack represents a 'docker compose' stack living in a specific directory
@@ -176,12 +177,10 @@ type StackWithResources struct {
 	// These all refer to paths within the Resource filesystem.
 	Resources fs.FS
 
-	ContextPath string // the 'docker compose' stack context. Can, but does not have to, contain 'docker-compose.yml'
+	ContextPath string // the 'docker compose' stack context. May or may not contain 'docker-compose.yml'
 
-	// TODO: Make this nicer to replace variables
-	ReadComposeFile func() (io.Reader, error) // read the 'docker-compose.yml' (if not contained in context)
+	ComposerYML func(*yaml.Node) (*yaml.Node, error) // update 'docker-compose.yml', if no 'docker-compose.yml' exists, the passed node is nil.
 
-	// EnvPath    string            // the '.env' template, will be installed using [unpack.InstallTemplate]. If empty, use new syntax
 	EnvContext map[string]string // context when instantiating the '.env' template
 
 	CopyContextFiles []string // Files to copy from the installation context
@@ -219,36 +218,12 @@ func (is StackWithResources) Install(ctx context.Context, progress io.Writer, co
 		}
 	}
 
-	// write the docker-compose.yml file
-	if is.ReadComposeFile != nil {
-		err := (func() error {
-			// find the file to install!
-			dst := filepath.Join(is.Dir, "docker-compose.yml")
-			defer fmt.Fprintf(progress, "[install] %s\n", dst)
+	// update the docker compose file
+	if is.ComposerYML != nil {
+		dst := filepath.Join(is.Dir, "docker-compose.yml")
+		fmt.Fprintf(progress, "[install] %s\n", dst)
 
-			// create the file
-			yml, err := umaskfree.Create(dst, umaskfree.DefaultFilePerm)
-			if err != nil {
-				return err
-			}
-			defer yml.Close()
-
-			// open the source file from the context
-			src, err := is.ReadComposeFile()
-			if err != nil {
-				return err
-			}
-			if srcc, ok := src.(io.Closer); ok {
-				defer srcc.Close()
-			}
-
-			// copy it over!
-			{
-				_, err := io.Copy(yml, src)
-				return err
-			}
-		})()
-		if err != nil {
+		if err := doComposeFile(dst, is.ComposerYML); err != nil {
 			return err
 		}
 	}
@@ -301,7 +276,7 @@ func (is StackWithResources) Install(ctx context.Context, progress io.Writer, co
 		dst := filepath.Join(is.Dir, name)
 
 		fmt.Fprintf(progress, "[touch]   %s\n", dst)
-		if err := umaskfree.Touch(dst, is.TouchFilesPerm); err != nil {
+		if err := umaskfree.Touch(dst, umaskfree.DefaultFilePerm); err != nil {
 			return err
 		}
 	}
@@ -318,6 +293,59 @@ func (is StackWithResources) Install(ctx context.Context, progress io.Writer, co
 	return nil
 }
 
+// doComposeFile updates the compose file using the update function.
+//
+// If the file at path already exists, calls update with the existing data.
+// if the file at path does not exist, calls update(nil).
+func doComposeFile(path string, update func(node *yaml.Node) (*yaml.Node, error)) error {
+	var mode fs.FileMode
+	var node *yaml.Node
+
+	{
+		stat, err := os.Stat(path)
+		switch {
+		case err == nil:
+			// file exists => use the previous file mode
+			mode = stat.Mode()
+
+			// read the yaml bytes
+			bytes, err := os.ReadFile(path)
+			if err != nil {
+				return errors.Wrap(err, "unable to read existing file")
+			}
+
+			// unmarshal it into a node, or bail out!
+			node = new(yaml.Node)
+			if err := yaml.Unmarshal(bytes, node); err != nil {
+				return errors.Wrap(err, "unable to unmarshal existing file")
+			}
+		case errors.Is(err, fs.ErrNotExist):
+			// file does not exist => use default mode
+			mode = umaskfree.DefaultFilePerm
+
+			// use a nil existing node
+			node = nil
+		default:
+			return err
+		}
+	}
+
+	// update the node
+	node, err := update(node)
+	if err != nil {
+		return errors.Wrap(err, "update function failed")
+	}
+
+	// re-encode the bytes
+	result, err := yaml.Marshal(node)
+	if err != nil {
+		return errors.Wrap(err, "failed to re-marshal")
+	}
+
+	// write the bytes back!
+	return umaskfree.WriteFile(path, result, mode)
+}
+
 // writeEnvFile writes an environment file
 func writeEnvFile(path string, perm fs.FileMode, variables map[string]string) error {
 	// create the environment file

internal/dis/component/web/web.go

@@ -1,11 +1,10 @@
 package web
 
 import (
-	"bytes"
-	"io"
 	"path/filepath"
 
 	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
+	"gopkg.in/yaml.v3"
 
 	_ "embed"
 )
@@ -44,16 +43,23 @@ func (web *Web) Stack() component.StackWithResources {
 	}
 
 	if web.Config.HTTP.HTTPSEnabled() {
-		stack.ReadComposeFile = func() (io.Reader, error) {
-			return bytes.NewReader(dockerComposeHTTPS), nil
-		}
+		stack.ComposerYML = readYaml(dockerComposeHTTPS)
 		stack.TouchFilesPerm = 0600
 		stack.TouchFiles = []string{"acme.json"}
 	} else {
-		stack.ReadComposeFile = func() (io.Reader, error) {
-			return bytes.NewReader(dockerComposeHTTP), nil
-		}
+		stack.ComposerYML = readYaml(dockerComposeHTTP)
 	}
 
 	return component.MakeStack(web, stack)
 }
+
+func readYaml(bytes []byte) func(*yaml.Node) (*yaml.Node, error) {
+	return func(n *yaml.Node) (*yaml.Node, error) {
+		var node yaml.Node
+		err := yaml.Unmarshal(bytes, &node)
+		if err != nil {
+			return nil, err
+		}
+		return &node, nil
+	}
+}