Add Separate tree for build dependency

Reuse the Recipe and extend it to read a separate tree for build
dependencies.

Also add accessors to compilespec to produce dockerfile image format.

pkg/compiler/spec.go

@@ -16,23 +16,86 @@
 package compiler
 
 import (
+	pkg "github.com/mudler/luet/pkg/package"
 	yaml "gopkg.in/yaml.v2"
+	"io/ioutil"
 )
 
 type LuetCompilationSpec struct {
-	Steps []string `json:"steps"`
-	Image string   `json:"image"`
+	Steps   []string    `json:"steps"` // Are run inside a container and the result layer diff is saved
+	Image   string      `json:"image"`
+	Seed    string      `json:"seed"`
+	Package pkg.Package `json:"-"`
 }
 
-func NewLuetCompilationSpec(b []byte) (CompilationSpec, error) {
+func NewLuetCompilationSpec(b []byte, p pkg.Package) (CompilationSpec, error) {
 	var spec LuetCompilationSpec
 	err := yaml.Unmarshal(b, &spec)
 	if err != nil {
 		return &spec, err
 	}
+	spec.Package = p
 	return &spec, nil
 }
 
-func (cs *LuetCompilationSpec) ToDocker() (string, error) {
-	return "", nil
+func (cs *LuetCompilationSpec) GetPackage() pkg.Package {
+	return cs.Package
+}
+
+func (cs *LuetCompilationSpec) BuildSteps() []string {
+	return cs.Steps
+}
+
+func (cs *LuetCompilationSpec) GetSeedImage() string {
+	return cs.Seed
+}
+
+func (cs *LuetCompilationSpec) GetImage() string {
+	return cs.Image
+}
+
+func (cs *LuetCompilationSpec) SetImage(s string) {
+	cs.Image = s
+}
+
+func (cs *LuetCompilationSpec) SetSeedImage(s string) {
+	cs.Seed = s
+}
+
+// TODO: docker build image first. Then a backend can be used to actually spin up a container with it and run the steps within
+func (cs *LuetCompilationSpec) RenderBuildImage() (string, error) {
+	spec := `
+FROM ` + cs.GetSeedImage() + `
+COPY . /luetbuild
+WORKDIR /luetbuild
+`
+	return spec, nil
+}
+
+// TODO: docker build image first. Then a backend can be used to actually spin up a container with it and run the steps within
+func (cs *LuetCompilationSpec) RenderStepImage(image string) (string, error) {
+	spec := `
+FROM ` + image
+	for _, s := range cs.BuildSteps() {
+		spec = spec + `
+RUN ` + s
+	}
+
+	return spec, nil
+}
+
+func (cs *LuetCompilationSpec) WriteBuildImageDefinition(path string) error {
+	data, err := cs.RenderBuildImage()
+	if err != nil {
+		return err
+	}
+	return ioutil.WriteFile(path, []byte(data), 0644)
+}
+
+func (cs *LuetCompilationSpec) WriteStepImageDefinition(fromimage, path string) error {
+	data, err := cs.RenderStepImage(fromimage)
+	if err != nil {
+		return err
+	}
+	return ioutil.WriteFile(path, []byte(data), 0644)
 }