// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You 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 kube

import (
	"os"

	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)

// BuildRestConfig builds the rest.Config object from kubeconfig filepath and
// context, if kubeconfig is missing, building from in-cluster configuration.
func BuildRestConfig(kubeconfig, context string) (*rest.Config, error) {
	if kubeconfig != "" {
		info, err := os.Stat(kubeconfig)
		if err != nil || info.Size() == 0 {
			// If the specified kubeconfig doesn't exists / empty file / any other error
			// from file stat, fall back to default
			kubeconfig = ""
		}
	}

	//Config loading rules:
	// 1. kubeconfig if it not empty string
	// 2. Config(s) in KUBECONFIG environment variable
	// 3. In cluster config if running in-cluster
	// 4. Use $HOME/.kube/config
	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
	loadingRules.DefaultClientConfig = &clientcmd.DefaultClientConfig
	loadingRules.ExplicitPath = kubeconfig
	configOverrides := &clientcmd.ConfigOverrides{
		ClusterDefaults: clientcmd.ClusterDefaults,
		CurrentContext:  context,
	}

	clientConfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, configOverrides)
	return clientConfig.ClientConfig()
}