/*
Copyright 2017 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 source

import (
	"errors"
	"net/http"
	"os"
	"strings"
	"time"

	"sync"

	"github.com/linki/instrumented_http"
	log "github.com/sirupsen/logrus"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
)

// ErrSourceNotFound is returned when a requested source doesn't exist.
var ErrSourceNotFound = errors.New("source not found")

// Config holds shared configuration options for all Sources.
type Config struct {
	Namespace                string
	AnnotationFilter         string
	FQDNTemplate             string
	CombineFQDNAndAnnotation bool
	Compatibility            string
	PublishInternal          bool
	PublishHostIP            bool
	ConnectorServer          string
	ServiceTypeFilter        []string
}

// ClientGenerator provides clients
type ClientGenerator interface {
	KubeClient() (kubernetes.Interface, error)
}

// SingletonClientGenerator stores provider clients and guarantees that only one instance of client
// will be generated
type SingletonClientGenerator struct {
	KubeConfig     string
	KubeMaster     string
	RequestTimeout time.Duration
	client         kubernetes.Interface
	sync.Once
}

// KubeClient generates a kube client if it was not created before
func (p *SingletonClientGenerator) KubeClient() (kubernetes.Interface, error) {
	var err error
	p.Once.Do(func() {
		p.client, err = NewKubeClient(p.KubeConfig, p.KubeMaster, p.RequestTimeout)
	})
	return p.client, err
}

// ByNames returns multiple Sources given multiple names.
func ByNames(p ClientGenerator, names []string, cfg *Config) ([]Source, error) {
	sources := []Source{}
	for _, name := range names {
		source, err := BuildWithConfig(name, p, cfg)
		if err != nil {
			return nil, err
		}
		sources = append(sources, source)
	}

	return sources, nil
}

// BuildWithConfig allows to generate a Source implementation from the shared config
func BuildWithConfig(source string, p ClientGenerator, cfg *Config) (Source, error) {
	switch source {
	case "service":
		client, err := p.KubeClient()
		if err != nil {
			return nil, err
		}
		return NewServiceSource(client, cfg.Namespace, cfg.AnnotationFilter, cfg.FQDNTemplate, cfg.CombineFQDNAndAnnotation, cfg.Compatibility, cfg.PublishInternal, cfg.PublishHostIP, cfg.ServiceTypeFilter)
	case "ingress":
		client, err := p.KubeClient()
		if err != nil {
			return nil, err
		}
		return NewIngressSource(client, cfg.Namespace, cfg.AnnotationFilter, cfg.FQDNTemplate, cfg.CombineFQDNAndAnnotation)
	case "fake":
		return NewFakeSource(cfg.FQDNTemplate)
	case "connector":
		return NewConnectorSource(cfg.ConnectorServer)
	}
	return nil, ErrSourceNotFound
}

// NewKubeClient returns a new Kubernetes client object. It takes a Config and
// uses KubeMaster and KubeConfig attributes to connect to the cluster. If
// KubeConfig isn't provided it defaults to using the recommended default.
func NewKubeClient(kubeConfig, kubeMaster string, requestTimeout time.Duration) (*kubernetes.Clientset, error) {
	if kubeConfig == "" {
		if _, err := os.Stat(clientcmd.RecommendedHomeFile); err == nil {
			kubeConfig = clientcmd.RecommendedHomeFile
		}
	}

	config, err := clientcmd.BuildConfigFromFlags(kubeMaster, kubeConfig)
	if err != nil {
		return nil, err
	}

	config.WrapTransport = func(rt http.RoundTripper) http.RoundTripper {
		return instrumented_http.NewTransport(rt, &instrumented_http.Callbacks{
			PathProcessor: func(path string) string {
				parts := strings.Split(path, "/")
				return parts[len(parts)-1]
			},
		})
	}

	config.Timeout = requestTimeout

	client, err := kubernetes.NewForConfig(config)
	if err != nil {
		return nil, err
	}

	log.Infof("Connected to cluster at %s", config.Host)

	return client, nil
}