Fn framework template and process options

- Refactor framework code to be simpler
- Add TemplatesFn feature
- Add PreProcessFilters feature
- Add PostProcessFilters features
- Add TemplatesFromDir
- Add PatchTemplatesFromDir
- Add PatchContainerTemplatesFromDir

kyaml/fn/framework/pkger.go

@@ -0,0 +1,154 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package framework
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+	"strings"
+	"text/template"
+
+	"github.com/markbates/pkger"
+)
+
+type TemplatesFn func(*ResourceList) ([]*template.Template, error)
+
+// TemplatesFromDir applies a directory of templates as generated resources.
+func TemplatesFromDir(dirs ...pkger.Dir) TemplatesFn {
+	return func(_ *ResourceList) ([]*template.Template, error) {
+		var pt []*template.Template
+		for i := range dirs {
+			d := dirs[i]
+			err := pkger.Walk(string(d), func(p string, info os.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				if !strings.HasSuffix(info.Name(), ".template.yaml") {
+					return nil
+				}
+				name := path.Join(string(d), info.Name())
+				f, err := pkger.Open(name)
+				if err != nil {
+					return err
+				}
+				b, err := ioutil.ReadAll(f)
+				if err != nil {
+					return err
+				}
+				t, err := template.New(info.Name()).Parse(string(b))
+				if err != nil {
+					return err
+				}
+
+				pt = append(pt, t)
+				return nil
+			})
+			if err != nil {
+				return nil, err
+			}
+		}
+		return pt, nil
+	}
+}
+
+// PatchTemplatesFn returns a slice of PatchTemplate
+type PatchTemplatesFn func(*ResourceList) ([]PatchTemplate, error)
+
+// PT applies a directory of patches using the Selector
+type PT struct {
+	Selector func() *Selector
+	Dir      pkger.Dir
+}
+
+// PatchTemplatesFromDir applies a directory of templates as patches.
+func PatchTemplatesFromDir(templates ...PT) PatchTemplatesFn {
+	return func(*ResourceList) ([]PatchTemplate, error) {
+		var pt []PatchTemplate
+		for i := range templates {
+			v := templates[i]
+			err := pkger.Walk(string(v.Dir), func(p string, info os.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				name := path.Join(string(v.Dir), info.Name())
+
+				if !strings.HasSuffix(info.Name(), ".template.yaml") {
+					return nil
+				}
+				f, err := pkger.Open(name)
+				if err != nil {
+					return err
+				}
+				b, err := ioutil.ReadAll(f)
+				if err != nil {
+					return err
+				}
+				t, err := template.New(info.Name()).Parse(string(b))
+				if err != nil {
+					return err
+				}
+
+				pt = append(pt, PatchTemplate{Template: t, Selector: v.Selector()})
+				return nil
+			})
+			if err != nil {
+				return nil, err
+			}
+		}
+		return pt, nil
+	}
+}
+
+// ContainerPatchTemplateFn returns a slice of ContainerPatchTemplate
+type ContainerPatchTemplateFn func(*ResourceList) ([]ContainerPatchTemplate, error)
+
+// CPT applies a directory of container patches using the Selector
+type CPT struct {
+	Selector func() *Selector
+	Dir      pkger.Dir
+	Names    []string
+}
+
+// ContainerPatchTemplatesFromDir applies a directory of templates as container patches.
+func ContainerPatchTemplatesFromDir(templates ...CPT) ContainerPatchTemplateFn {
+	return func(*ResourceList) ([]ContainerPatchTemplate, error) {
+		var cpt []ContainerPatchTemplate
+		for i := range templates {
+			v := templates[i]
+			err := pkger.Walk(string(v.Dir), func(p string, info os.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				if !strings.HasSuffix(info.Name(), ".template.yaml") {
+					return nil
+				}
+
+				name := path.Join(string(v.Dir), info.Name())
+				f, err := pkger.Open(name)
+				if err != nil {
+					return err
+				}
+				b, err := ioutil.ReadAll(f)
+				if err != nil {
+					return err
+				}
+				t, err := template.New(info.Name()).Parse(string(b))
+				if err != nil {
+					return err
+				}
+
+				cpt = append(cpt, ContainerPatchTemplate{
+					PatchTemplate:  PatchTemplate{Template: t, Selector: v.Selector()},
+					ContainerNames: v.Names,
+				})
+				return nil
+			})
+			if err != nil {
+				return nil, err
+			}
+		}
+		return cpt, nil
+	}
+}