/*
Copyright 2022 The Karmada 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 apiclient

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

	"k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/homedir"
	aggregator "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset"
	"k8s.io/utils/env"
)

var (
	defaultKubeConfig = filepath.Join(homedir.HomeDir(), ".kube", "config")

	// ErrEmptyConfig is the error message to be displayed if the configuration info is missing or incomplete
	ErrEmptyConfig = clientcmd.NewEmptyConfigError(
		`Missing or incomplete configuration info.  Please point to an existing, complete config file:
  1. Via the command-line flag --kubeconfig
  2. Via the KUBECONFIG environment variable
  3. In your home directory as ~/.kube/config
`)
)

// RestConfig is to create a rest config from the context and kubeconfig passed as arguments.
func RestConfig(context, kubeconfigPath string) (*rest.Config, error) {
	kubeconfigPath = KubeConfigPath(kubeconfigPath)
	if !Exists(kubeconfigPath) {
		// Given no kubeconfig is provided, give it a try to load the config by
		// in-cluster mode if the client running inside a pod running on kubernetes.
		host, port := os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")
		if len(host) > 0 || len(port) > 0 { // in-cluster mode
			inClusterRestConfig, err := rest.InClusterConfig()
			if err != nil {
				return nil, fmt.Errorf("failed to load rest config by in-cluster mode: %v", err)
			}
			return inClusterRestConfig, nil
		}

		return nil, ErrEmptyConfig
	}

	pathOptions := clientcmd.NewDefaultPathOptions()

	loadingRules := *pathOptions.LoadingRules
	loadingRules.ExplicitPath = kubeconfigPath
	loadingRules.Precedence = pathOptions.GetLoadingPrecedence()
	overrides := &clientcmd.ConfigOverrides{
		CurrentContext: context,
	}
	clientConfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(&loadingRules, overrides)

	restConfig, err := clientConfig.ClientConfig()
	if err != nil {
		return nil, err
	}

	return restConfig, err
}

// KubeConfigPath is to return kubeconfig file path in the following order:
// 1. Via the command-line flag --kubeconfig
// 2. Via the KUBECONFIG environment variable
// 3. In your home directory as ~/.kube/config
func KubeConfigPath(kubeconfigPath string) string {
	if kubeconfigPath == "" {
		kubeconfigPath = env.GetString("KUBECONFIG", defaultKubeConfig)
	}

	return kubeconfigPath
}

// NewClientSet is to create a kubernetes ClientSet
func NewClientSet(c *rest.Config) (*kubernetes.Clientset, error) {
	return kubernetes.NewForConfig(c)
}

// NewCRDsClient is to create a clientset ClientSet
func NewCRDsClient(c *rest.Config) (clientset.Interface, error) {
	return clientset.NewForConfig(c)
}

// NewAPIRegistrationClient is to create an apiregistration ClientSet
func NewAPIRegistrationClient(c *rest.Config) (aggregator.Interface, error) {
	return aggregator.NewForConfig(c)
}

// Exists determine if path exists
func Exists(path string) bool {
	if _, err := os.Stat(path); err != nil {
		return os.IsExist(err)
	}
	return true
}