/*
Copyright 2016 The Kubernetes Authors All rights reserved.

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 kubeconfig

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"

	"github.com/golang/glog"
	"k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
	"k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api/latest"
	"k8s.io/kubernetes/pkg/runtime"
)

// ReadConfigOrNew retrieves Kubernetes client configuration from a file.
// If no files exists, an empty configuration is returned.
func ReadConfigOrNew(filename string) (*api.Config, error) {
	data, err := ioutil.ReadFile(filename)
	if os.IsNotExist(err) {
		return api.NewConfig(), nil
	} else if err != nil {
		return nil, err
	}

	// decode config, empty if no bytes
	config, err := decode(data)
	if err != nil {
		return nil, fmt.Errorf("could not read config: %v", err)
	}

	// initialize nil maps
	if config.AuthInfos == nil {
		config.AuthInfos = map[string]*api.AuthInfo{}
	}
	if config.Clusters == nil {
		config.Clusters = map[string]*api.Cluster{}
	}
	if config.Contexts == nil {
		config.Contexts = map[string]*api.Context{}
	}

	return config, nil
}

// WriteConfig encodes the configuration and writes it to the given file.
// If the file exists, it's contents will be overwritten.
func WriteConfig(config *api.Config, filename string) error {
	if config == nil {
		glog.Errorf("could not write to '%s': config can't be nil", filename)
	}

	// encode config to YAML
	data, err := runtime.Encode(latest.Codec, config)
	if err != nil {
		return fmt.Errorf("could not write to '%s': failed to encode config: %v", filename, err)
	}

	// create parent dir if doesn't exist
	dir := filepath.Dir(filename)
	if _, err := os.Stat(dir); os.IsNotExist(err) {
		if err = os.MkdirAll(dir, 0755); err != nil {
			return err
		}
	}

	// write with restricted permissions
	if err := ioutil.WriteFile(filename, data, 0600); err != nil {
		return err
	}
	return nil
}

// decode reads a Config object from bytes.
// Returns empty config if no bytes.
func decode(data []byte) (*api.Config, error) {
	// if no data, return empty config
	if len(data) == 0 {
		return api.NewConfig(), nil
	}

	config, _, err := latest.Codec.Decode(data, nil, nil)
	if err != nil {
		return nil, err
	}

	return config.(*api.Config), nil
}
