/*
Copyright 2019 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 model

import (
	"k8s.io/klog/v2"
	"k8s.io/kops/upup/pkg/fi"
	"k8s.io/kops/upup/pkg/fi/nodeup/nodetasks"
	"k8s.io/kops/util/pkg/distributions"
)

// NTPBuilder installs and starts NTP, to ensure accurate clock times.
// As well as general log confusion, clock-skew of more than 5 minutes
// causes AWS API calls to fail
type NTPBuilder struct {
	*NodeupModelContext
}

var _ fi.ModelBuilder = &NTPBuilder{}

// Build is responsible for configuring NTP
func (b *NTPBuilder) Build(c *fi.ModelBuilderContext) error {
	if !b.managed() {
		klog.Infof("Managed is set to false; won't install NTP")
		return nil
	}

	switch b.Distribution {
	case distributions.DistributionContainerOS:
		klog.Infof("Detected ContainerOS; won't install ntp")
		return nil
	case distributions.DistributionFlatcar:
		klog.Infof("Detected Flatcar; won't install ntp")
		return nil
	}

	var ntpHost string
	switch b.Cluster.Spec.CloudProvider {
	case "aws":
		ntpHost = "169.254.169.123"
	case "gce":
		ntpHost = "time.google.com"
	default:
		ntpHost = ""
	}

	if b.Distribution.IsDebianFamily() {
		// Ubuntu recommends systemd-timesyncd, but on ubuntu on GCE systemd-timesyncd is blocked (in favor of chrony)
		if b.Distribution.IsUbuntu() && !b.RunningOnGCE() {
			if ntpHost != "" {
				c.AddTask(b.buildTimesyncdConf("/etc/systemd/timesyncd.conf", ntpHost))
			}
			c.AddTask((&nodetasks.Service{Name: "systemd-timesyncd"}).InitDefaults())
		} else {
			c.AddTask(&nodetasks.Package{Name: "chrony"})
			if ntpHost != "" {
				c.AddTask(b.buildChronydConf("/etc/chrony/chrony.conf", ntpHost))
			}
			c.AddTask((&nodetasks.Service{Name: "chrony"}).InitDefaults())
		}
	} else if b.Distribution.IsRHELFamily() {
		c.AddTask(&nodetasks.Package{Name: "chrony"})
		if ntpHost != "" {
			c.AddTask(b.buildChronydConf("/etc/chrony.conf", ntpHost))
		}
		c.AddTask((&nodetasks.Service{Name: "chronyd"}).InitDefaults())
	} else {
		klog.Warningf("unknown distribution, skipping ntp install: %v", b.Distribution)
		return nil
	}

	return nil
}

func (b *NTPBuilder) buildChronydConf(path string, host string) *nodetasks.File {
	conf := `# Built by Kops - do NOT edit

pool ` + host + ` prefer iburst
driftfile /var/lib/chrony/drift
leapsectz right/UTC
logdir /var/log/chrony
makestep 1.0 3
maxupdateskew 100.0
rtcsync
`
	return &nodetasks.File{
		Path:     path,
		Contents: fi.NewStringResource(conf),
		Type:     nodetasks.FileType_File,
		Mode:     s("0644"),
	}
}

func (b *NTPBuilder) buildTimesyncdConf(path string, host string) *nodetasks.File {
	conf := `# Built by Kops - do NOT edit

[Time]
NTP=` + host + `
`
	return &nodetasks.File{
		Path:     path,
		Contents: fi.NewStringResource(conf),
		Type:     nodetasks.FileType_File,
		Mode:     s("0644"),
	}
}

// managed determines if kops should manage the installation and configuration of NTP.
func (b *NTPBuilder) managed() bool {
	n := b.Cluster.Spec.NTP
	// Consider the NTP is managed when the NTP configuration
	// is not specified (for backward compatibility).
	return n == nil || n.Managed == nil || *n.Managed
}