Add flux tree command

The `flux tree kustomization` command prints the resources reconciled by the given Kustomization.

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

internal/tree/tree.go

@@ -0,0 +1,141 @@
+/*
+Copyright 2021 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.
+
+Derived work from https://github.com/d6o/GoTree
+Copyright (c) 2017 Diego Siqueira
+*/
+
+package tree
+
+import (
+	"strings"
+
+	"github.com/fluxcd/pkg/ssa"
+	"sigs.k8s.io/cli-utils/pkg/object"
+)
+
+const (
+	newLine      = "\n"
+	emptySpace   = "    "
+	middleItem   = "├── "
+	continueItem = "│   "
+	lastItem     = "└── "
+)
+
+type (
+	objMetadataTree struct {
+		objMetadata object.ObjMetadata
+		items       []ObjMetadataTree
+	}
+
+	ObjMetadataTree interface {
+		Add(objMetadata object.ObjMetadata) ObjMetadataTree
+		AddTree(tree ObjMetadataTree)
+		Items() []ObjMetadataTree
+		Text() string
+		Print() string
+	}
+
+	printer struct {
+	}
+
+	Printer interface {
+		Print(ObjMetadataTree) string
+	}
+)
+
+func New(objMetadata object.ObjMetadata) ObjMetadataTree {
+	return &objMetadataTree{
+		objMetadata: objMetadata,
+		items:       []ObjMetadataTree{},
+	}
+}
+
+func (t *objMetadataTree) Add(objMetadata object.ObjMetadata) ObjMetadataTree {
+	n := New(objMetadata)
+	t.items = append(t.items, n)
+	return n
+}
+
+func (t *objMetadataTree) AddTree(tree ObjMetadataTree) {
+	t.items = append(t.items, tree)
+}
+
+func (t *objMetadataTree) Text() string {
+	return ssa.FmtObjMetadata(t.objMetadata)
+}
+
+func (t *objMetadataTree) Items() []ObjMetadataTree {
+	return t.items
+}
+
+func (t *objMetadataTree) Print() string {
+	return newPrinter().Print(t)
+}
+
+func newPrinter() Printer {
+	return &printer{}
+}
+
+func (p *printer) Print(t ObjMetadataTree) string {
+	return t.Text() + newLine + p.printItems(t.Items(), []bool{})
+}
+
+func (p *printer) printText(text string, spaces []bool, last bool) string {
+	var result string
+	for _, space := range spaces {
+		if space {
+			result += emptySpace
+		} else {
+			result += continueItem
+		}
+	}
+
+	indicator := middleItem
+	if last {
+		indicator = lastItem
+	}
+
+	var out string
+	lines := strings.Split(text, "\n")
+	for i := range lines {
+		text := lines[i]
+		if i == 0 {
+			out += result + indicator + text + newLine
+			continue
+		}
+		if last {
+			indicator = emptySpace
+		} else {
+			indicator = continueItem
+		}
+		out += result + indicator + text + newLine
+	}
+
+	return out
+}
+
+func (p *printer) printItems(t []ObjMetadataTree, spaces []bool) string {
+	var result string
+	for i, f := range t {
+		last := i == len(t)-1
+		result += p.printText(f.Text(), spaces, last)
+		if len(f.Items()) > 0 {
+			spacesChild := append(spaces, last)
+			result += p.printItems(f.Items(), spacesChild)
+		}
+	}
+	return result
+}