/*
Copyright 2019 The Kubernetes 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 kustomize

import (
	"bytes"
	"encoding/json"
	"io"
	"strings"

	"github.com/pkg/errors"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/yaml"
	"sigs.k8s.io/kustomize/pkg/ifc"
)

// strategicMergeSlice is a slice of strategic merge patches.
// Unstructured objects are used to represent strategic merge patches of any group/version/kind.
type strategicMergeSlice []*unstructured.Unstructured

// newStrategicMergeSliceFromFile returns a slice of strategic merge patches from a file
func newStrategicMergeSliceFromFile(loader ifc.Loader, path string) (strategicMergeSlice, error) {
	content, err := loader.Load(path)
	if err != nil {
		return nil, errors.Wrapf(err, "load from path %q failed", path)
	}
	res, err := newStrategicMergeSliceFromBytes(content)
	if err != nil {
		return nil, errors.Wrapf(err, "convert %q to Unstructured failed", path)
	}
	return res, nil
}

// newStrategicMergeSliceFromBytes returns a strategic merge patches contained in a []byte.
// This functions handles all the nuances of Kubernetes yaml (e.g. many yaml
// documents in one file, List of objects)
func newStrategicMergeSliceFromBytes(in []byte) (strategicMergeSlice, error) {
	decoder := yaml.NewYAMLOrJSONDecoder(bytes.NewReader(in), 1024)
	var result strategicMergeSlice
	var err error
	// Parse all the yaml documents in the file
	for err == nil || isEmptyYamlError(err) {
		var u unstructured.Unstructured
		err = decoder.Decode(&u)
		// if the yaml document is a valid unstructured object
		if err == nil {
			// it the unstructured object is empty, move to the next
			if len(u.Object) == 0 {
				continue
			}

			// validate the object has kind, metadata.name as required by Kustomize
			if err := validate(u); err != nil {
				return nil, err
			}

			// if the document is a list of objects
			if strings.HasSuffix(u.GetKind(), "List") {
				// for each item in the list of objects
				if err := u.EachListItem(func(item runtime.Object) error {
					// Marshal the object
					itemJSON, err := json.Marshal(item)
					if err != nil {
						return err
					}

					// Get the strategicMergeSlice for the item
					itemU, err := newStrategicMergeSliceFromBytes(itemJSON)
					if err != nil {
						return err
					}

					// append the strategicMergeSlice for the item to the strategicMergeSlice
					result = append(result, itemU...)

					return nil
				}); err != nil {
					return nil, err
				}

				continue
			}

			// append the object to the stategicMergeSlice
			result = append(result, &u)
		}
	}
	if err != io.EOF {
		return nil, err
	}
	return result, nil
}

// filterByResource returns all the strategic merge patches in the strategicMergeSlice corresponding to a given resource
func (s *strategicMergeSlice) filterByResource(r *unstructured.Unstructured) strategicMergeSlice {
	var result strategicMergeSlice
	for _, p := range *s {
		if p.GroupVersionKind() == r.GroupVersionKind() &&
			p.GetNamespace() == r.GetNamespace() &&
			p.GetName() == r.GetName() {
			result = append(result, p)
		}
	}
	return result
}

// validate validates that u has kind and name
// except for kind `List`, which doesn't require a name
func validate(u unstructured.Unstructured) error {
	kind := u.GetKind()
	if kind == "" {
		return errors.New("missing kind in object")
	} else if strings.HasSuffix(kind, "List") {
		return nil
	}
	if u.GetName() == "" {
		return errors.New("missing metadata.name in object")
	}
	return nil
}

func isEmptyYamlError(err error) bool {
	return strings.Contains(err.Error(), "is missing in 'null'")
}