Refactor manifests generation

- introduce manifestgen pkg, to be consumed by the CLI and Terraform provider
- consolidate defaults in manifestgen/install pkg
- introduce Manifest as the returning type of manifest generation
- add helper function to Manifest for writing multi-doc YAMLs on disk

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

pkg/manifestgen/install/manifests.go

@@ -0,0 +1,125 @@
+/*
+Copyright 2020 The Flux authors
+
+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 install
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"sigs.k8s.io/kustomize/api/filesys"
+	"sigs.k8s.io/kustomize/api/krusty"
+
+	"github.com/fluxcd/pkg/untar"
+)
+
+func fetch(ctx context.Context, url, version, dir string) error {
+	ghURL := fmt.Sprintf("%s/latest/download/manifests.tar.gz", url)
+	if strings.HasPrefix(version, "v") {
+		ghURL = fmt.Sprintf("%s/download/%s/manifests.tar.gz", url, version)
+	}
+
+	req, err := http.NewRequest("GET", ghURL, nil)
+	if err != nil {
+		return fmt.Errorf("failed to create HTTP request for %s, error: %w", ghURL, err)
+	}
+
+	// download
+	resp, err := http.DefaultClient.Do(req.WithContext(ctx))
+	if err != nil {
+		return fmt.Errorf("failed to download manifests.tar.gz from %s, error: %w", ghURL, err)
+	}
+	defer resp.Body.Close()
+
+	// check response
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("faild to download manifests.tar.gz from %s, status: %s", ghURL, resp.Status)
+	}
+
+	// extract
+	if _, err = untar.Untar(resp.Body, dir); err != nil {
+		return fmt.Errorf("faild to untar manifests.tar.gz from %s, error: %w", ghURL, err)
+	}
+
+	return nil
+}
+
+func generate(base string, options Options) error {
+	if containsItemString(options.Components, options.NotificationController) {
+		options.EventsAddr = fmt.Sprintf("http://%s/", options.NotificationController)
+	}
+
+	if err := execTemplate(options, namespaceTmpl, path.Join(base, "namespace.yaml")); err != nil {
+		return fmt.Errorf("generate namespace failed: %w", err)
+	}
+
+	if err := execTemplate(options, labelsTmpl, path.Join(base, "labels.yaml")); err != nil {
+		return fmt.Errorf("generate labels failed: %w", err)
+	}
+
+	if err := execTemplate(options, nodeSelectorTmpl, path.Join(base, "node-selector.yaml")); err != nil {
+		return fmt.Errorf("generate node selector failed: %w", err)
+	}
+
+	if err := execTemplate(options, kustomizationTmpl, path.Join(base, "kustomization.yaml")); err != nil {
+		return fmt.Errorf("generate kustomization failed: %w", err)
+	}
+
+	if err := os.MkdirAll(path.Join(base, "roles"), os.ModePerm); err != nil {
+		return fmt.Errorf("generate roles failed: %w", err)
+	}
+
+	if err := execTemplate(options, kustomizationRolesTmpl, path.Join(base, "roles/kustomization.yaml")); err != nil {
+		return fmt.Errorf("generate roles kustomization failed: %w", err)
+	}
+
+	if err := copyFile(filepath.Join(base, "rbac.yaml"), filepath.Join(base, "roles/rbac.yaml")); err != nil {
+		return fmt.Errorf("generate rbac failed: %w", err)
+	}
+	return nil
+}
+
+func build(base, output string) error {
+	kfile := filepath.Join(base, "kustomization.yaml")
+
+	fs := filesys.MakeFsOnDisk()
+	if !fs.Exists(kfile) {
+		return fmt.Errorf("%s not found", kfile)
+	}
+
+	opt := krusty.MakeDefaultOptions()
+	k := krusty.MakeKustomizer(fs, opt)
+	m, err := k.Run(base)
+	if err != nil {
+		return err
+	}
+
+	resources, err := m.AsYaml()
+	if err != nil {
+		return err
+	}
+
+	if err := fs.WriteFile(output, resources); err != nil {
+		return err
+	}
+
+	return nil
+}