/*
Copyright 2015 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 cmd

import (
	"fmt"
	"io"

	"k8s.io/kubernetes/pkg/kubectl"
	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
	"k8s.io/kubernetes/pkg/kubectl/resource"
	"k8s.io/kubernetes/pkg/util/errors"

	"github.com/spf13/cobra"
)

const (
	autoscaleLong = `Creates an autoscaler that automatically chooses and sets the number of pods that run in a kubernetes cluster.

Looks up a replication controller by name and creates an autoscaler that uses this replication controller as a reference.
An autoscaler can automatically increase or decrease number of pods deployed within the system as needed.`

	autoscaleExample = `# Auto scale a replication controller "foo", with the number of pods between 2 to 10, target CPU utilization at a default value that server applies:
$ kubectl autoscale rc foo --min=2 --max=10

# Auto scale a replication controller "foo", with the number of pods between 1 to 5, target CPU utilization at 80%:
$ kubectl autoscale rc foo --max=5 --cpu-percent=80`
)

// TODO: support autoscale for deployments
func NewCmdAutoscale(f *cmdutil.Factory, out io.Writer) *cobra.Command {
	filenames := []string{}
	cmd := &cobra.Command{
		Use:     "autoscale (-f FILENAME | TYPE NAME | TYPE/NAME) [--min=MINPODS] --max=MAXPODS [--cpu-percent=CPU] [flags]",
		Short:   "Auto-scale a replication controller",
		Long:    autoscaleLong,
		Example: autoscaleExample,
		Run: func(cmd *cobra.Command, args []string) {
			err := RunAutoscale(f, out, cmd, args, filenames)
			cmdutil.CheckErr(err)
		},
	}
	cmdutil.AddPrinterFlags(cmd)
	cmd.Flags().String("generator", "horizontalpodautoscaler/v1beta1", "The name of the API generator to use. Currently there is only 1 generator.")
	cmd.Flags().Int("min", -1, "The lower limit for the number of pods that can be set by the autoscaler. If it's not specified or negative, the server will apply a default value.")
	cmd.Flags().Int("max", -1, "The upper limit for the number of pods that can be set by the autoscaler. Required.")
	cmd.MarkFlagRequired("max")
	cmd.Flags().Int("cpu-percent", -1, fmt.Sprintf("The target average CPU utilization (represented as a percent of requested CPU) over all the pods. If it's not specified or negative, the server will apply a default value."))
	cmd.Flags().String("name", "", "The name for the newly created object. If not specified, the name of the input resource will be used.")
	cmd.Flags().Bool("dry-run", false, "If true, only print the object that would be sent, without creating it.")
	usage := "Filename, directory, or URL to a file identifying the resource to get from a server."
	kubectl.AddJsonFilenameFlag(cmd, &filenames, usage)
	return cmd
}

func RunAutoscale(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []string, filenames []string) error {
	namespace, enforceNamespace, err := f.DefaultNamespace()
	if err != nil {
		return err
	}

	// validate flags
	if err := validateFlags(cmd); err != nil {
		return err
	}

	mapper, typer := f.Object()
	r := resource.NewBuilder(mapper, typer, f.ClientMapperForCommand()).
		ContinueOnError().
		NamespaceParam(namespace).DefaultNamespace().
		FilenameParam(enforceNamespace, filenames...).
		ResourceTypeOrNameArgs(false, args...).
		Flatten().
		Do()
	infos, err := r.Infos()
	if err != nil {
		return err
	}
	if len(infos) > 1 {
		return fmt.Errorf("multiple resources provided: %v", args)
	}
	info := infos[0]
	mapping := info.ResourceMapping()
	if err := f.CanBeAutoscaled(mapping.Kind); err != nil {
		return err
	}

	// Get the generator, setup and validate all required parameters
	generatorName := cmdutil.GetFlagString(cmd, "generator")
	generator, found := f.Generator(generatorName)
	if !found {
		return cmdutil.UsageError(cmd, fmt.Sprintf("generator %q not found.", generatorName))
	}
	names := generator.ParamNames()
	params := kubectl.MakeParams(cmd, names)
	name := info.Name
	params["default-name"] = name

	params["scaleRef-kind"] = mapping.Kind
	params["scaleRef-namespace"] = namespace
	params["scaleRef-name"] = name
	params["scaleRef-apiVersion"] = mapping.APIVersion

	if err = kubectl.ValidateParams(names, params); err != nil {
		return err
	}

	// Generate new object
	object, err := generator.Generate(params)
	if err != nil {
		return err
	}

	resourceMapper := &resource.Mapper{ObjectTyper: typer, RESTMapper: mapper, ClientMapper: f.ClientMapperForCommand()}
	hpa, err := resourceMapper.InfoForObject(object)
	if err != nil {
		return err
	}
	// TODO: extract this flag to a central location, when such a location exists.
	if cmdutil.GetFlagBool(cmd, "dry-run") {
		return f.PrintObject(cmd, object, out)
	}

	// Serialize the configuration into an annotation.
	if err := kubectl.UpdateApplyAnnotation(hpa); err != nil {
		return err
	}

	object, err = resource.NewHelper(hpa.Client, hpa.Mapping).Create(namespace, false, object)
	if err != nil {
		return err
	}

	if len(cmdutil.GetFlagString(cmd, "output")) > 0 {
		return f.PrintObject(cmd, object, out)
	}
	cmdutil.PrintSuccess(mapper, false, out, info.Mapping.Resource, info.Name, "autoscaled")
	return nil
}

func validateFlags(cmd *cobra.Command) error {
	errs := []error{}
	max, min, cpu := cmdutil.GetFlagInt(cmd, "max"), cmdutil.GetFlagInt(cmd, "min"), cmdutil.GetFlagInt(cmd, "cpu-percent")
	if max < 1 || max < min {
		errs = append(errs, fmt.Errorf("--max=MAXPODS is required, and must be at least 1 and --min=MINPODS"))
	}
	if cpu > 100 {
		errs = append(errs, fmt.Errorf("CPU utilization (%%) cannot exceed 100"))
	}
	return errors.NewAggregate(errs)
}