/*
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.
*/

package kustomization

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"

	"sigs.k8s.io/kustomize/api/konfig"
	"sigs.k8s.io/kustomize/api/krusty"
	"sigs.k8s.io/kustomize/api/provider"
	"sigs.k8s.io/kustomize/api/resmap"
	kustypes "sigs.k8s.io/kustomize/api/types"
	"sigs.k8s.io/kustomize/kyaml/filesys"
	"sigs.k8s.io/yaml"

	"github.com/fluxcd/pkg/apis/kustomize"
)

type KustomizeGenerator struct {
	kustomization Kustomize
}

func NewGenerator(kustomization Kustomize) *KustomizeGenerator {
	return &KustomizeGenerator{
		kustomization: kustomization,
	}
}

// WriteFile generates a kustomization.yaml in the given directory if it does not exist.
// It apply the flux kustomize resources to the kustomization.yaml and then write the
// updated kustomization.yaml to the directory.
// It returns the original kustomization.yaml.
func (kg *KustomizeGenerator) WriteFile(dirPath string) ([]byte, error) {
	if err := kg.generateKustomization(dirPath); err != nil {
		return nil, err
	}

	kfile := filepath.Join(dirPath, konfig.DefaultKustomizationFileName())

	data, err := os.ReadFile(kfile)
	if err != nil {
		return nil, err
	}

	kus := kustypes.Kustomization{
		TypeMeta: kustypes.TypeMeta{
			APIVersion: kustypes.KustomizationVersion,
			Kind:       kustypes.KustomizationKind,
		},
	}

	if err := yaml.Unmarshal(data, &kus); err != nil {
		return nil, err
	}

	if kg.kustomization.GetTargetNamespace() != "" {
		kus.Namespace = kg.kustomization.GetTargetNamespace()
	}

	for _, m := range kg.kustomization.GetPatches() {
		kus.Patches = append(kus.Patches, kustypes.Patch{
			Patch:  m.Patch,
			Target: adaptSelector(&m.Target),
		})
	}

	for _, m := range kg.kustomization.GetPatchesStrategicMerge() {
		kus.PatchesStrategicMerge = append(kus.PatchesStrategicMerge, kustypes.PatchStrategicMerge(m.Raw))
	}

	for _, m := range kg.kustomization.GetPatchesJSON6902() {
		patch, err := json.Marshal(m.Patch)
		if err != nil {
			return nil, err
		}
		kus.PatchesJson6902 = append(kus.PatchesJson6902, kustypes.Patch{
			Patch:  string(patch),
			Target: adaptSelector(&m.Target),
		})
	}

	for _, image := range kg.kustomization.GetImages() {
		newImage := kustypes.Image{
			Name:    image.Name,
			NewName: image.NewName,
			NewTag:  image.NewTag,
		}
		if exists, index := checkKustomizeImageExists(kus.Images, image.Name); exists {
			kus.Images[index] = newImage
		} else {
			kus.Images = append(kus.Images, newImage)
		}
	}

	manifest, err := yaml.Marshal(kus)
	if err != nil {
		return nil, err
	}

	os.WriteFile(kfile, manifest, 0644)

	return data, nil
}

func checkKustomizeImageExists(images []kustypes.Image, imageName string) (bool, int) {
	for i, image := range images {
		if imageName == image.Name {
			return true, i
		}
	}

	return false, -1
}

func (kg *KustomizeGenerator) generateKustomization(dirPath string) error {
	fs := filesys.MakeFsOnDisk()

	// Determine if there already is a Kustomization file at the root,
	// as this means we do not have to generate one.
	for _, kfilename := range konfig.RecognizedKustomizationFileNames() {
		if kpath := filepath.Join(dirPath, kfilename); fs.Exists(kpath) && !fs.IsDir(kpath) {
			return nil
		}
	}

	scan := func(base string) ([]string, error) {
		var paths []string
		pvd := provider.NewDefaultDepProvider()
		rf := pvd.GetResourceFactory()
		err := fs.Walk(base, func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}
			if path == base {
				return nil
			}
			if info.IsDir() {
				// If a sub-directory contains an existing kustomization file add the
				// directory as a resource and do not decend into it.
				for _, kfilename := range konfig.RecognizedKustomizationFileNames() {
					if kpath := filepath.Join(path, kfilename); fs.Exists(kpath) && !fs.IsDir(kpath) {
						paths = append(paths, path)
						return filepath.SkipDir
					}
				}
				return nil
			}

			extension := filepath.Ext(path)
			if extension != ".yaml" && extension != ".yml" {
				return nil
			}

			fContents, err := fs.ReadFile(path)
			if err != nil {
				return err
			}

			if _, err := rf.SliceFromBytes(fContents); err != nil {
				return fmt.Errorf("failed to decode Kubernetes YAML from %s: %w", path, err)
			}
			paths = append(paths, path)
			return nil
		})
		return paths, err
	}

	abs, err := filepath.Abs(dirPath)
	if err != nil {
		return err
	}

	files, err := scan(abs)
	if err != nil {
		return err
	}

	kfile := filepath.Join(dirPath, konfig.DefaultKustomizationFileName())
	f, err := fs.Create(kfile)
	if err != nil {
		return err
	}
	f.Close()

	kus := kustypes.Kustomization{
		TypeMeta: kustypes.TypeMeta{
			APIVersion: kustypes.KustomizationVersion,
			Kind:       kustypes.KustomizationKind,
		},
	}

	var resources []string
	for _, file := range files {
		resources = append(resources, strings.Replace(file, abs, ".", 1))
	}

	kus.Resources = resources
	kd, err := yaml.Marshal(kus)
	if err != nil {
		return err
	}

	return os.WriteFile(kfile, kd, os.ModePerm)
}

func adaptSelector(selector *kustomize.Selector) (output *kustypes.Selector) {
	if selector != nil {
		output = &kustypes.Selector{}
		output.Gvk.Group = selector.Group
		output.Gvk.Kind = selector.Kind
		output.Gvk.Version = selector.Version
		output.Name = selector.Name
		output.Namespace = selector.Namespace
		output.LabelSelector = selector.LabelSelector
		output.AnnotationSelector = selector.AnnotationSelector
	}
	return
}

// TODO: remove mutex when kustomize fixes the concurrent map read/write panic
var kustomizeBuildMutex sync.Mutex

// buildKustomization wraps krusty.MakeKustomizer with the following settings:
// - load files from outside the kustomization.yaml root
// - disable plugins except for the builtin ones
func buildKustomization(fs filesys.FileSystem, dirPath string) (resmap.ResMap, error) {
	// temporary workaround for concurrent map read and map write bug
	// https://github.com/kubernetes-sigs/kustomize/issues/3659
	kustomizeBuildMutex.Lock()
	defer kustomizeBuildMutex.Unlock()

	buildOptions := &krusty.Options{
		LoadRestrictions: kustypes.LoadRestrictionsNone,
		PluginConfig:     kustypes.DisabledPluginConfig(),
	}

	k := krusty.MakeKustomizer(buildOptions)
	return k.Run(fs, dirPath)
}