/*
   Copyright The containerd 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 server

import (
	"context"
	"sort"

	"github.com/containerd/containerd/pkg/systemd"
	runcoptions "github.com/containerd/containerd/runtime/v2/runc/options"
	"github.com/containerd/log"
	runtime "k8s.io/cri-api/pkg/apis/runtime/v1"
)

func (c *criService) getLinuxRuntimeConfig(ctx context.Context) *runtime.LinuxRuntimeConfiguration {
	return &runtime.LinuxRuntimeConfiguration{CgroupDriver: c.getCgroupDriver(ctx)}
}

func (c *criService) getCgroupDriver(ctx context.Context) runtime.CgroupDriver {
	// Go through the runtime handlers in a predictable order, starting from the
	// default handler, others sorted in alphabetical order
	handlerNames := make([]string, 0, len(c.config.ContainerdConfig.Runtimes))
	for n := range c.config.ContainerdConfig.Runtimes {
		handlerNames = append(handlerNames, n)
	}
	sort.Slice(handlerNames, func(i, j int) bool {
		if handlerNames[i] == c.config.ContainerdConfig.DefaultRuntimeName {
			return true
		}
		if handlerNames[j] == c.config.ContainerdConfig.DefaultRuntimeName {
			return false
		}
		return handlerNames[i] < handlerNames[j]
	})

	for _, handler := range handlerNames {
		opts, err := generateRuntimeOptions(c.config.ContainerdConfig.Runtimes[handler])
		if err != nil {
			log.G(ctx).Debugf("failed to parse runtime handler options for %q", handler)
			continue
		}
		if d, ok := getCgroupDriverFromRuntimeHandlerOpts(opts); ok {
			return d
		}
		log.G(ctx).Debugf("runtime handler %q does not provide cgroup driver information", handler)
	}

	// If no runtime handlers have a setting, detect if systemd is running
	d := runtime.CgroupDriver_CGROUPFS
	if systemd.IsRunningSystemd() {
		d = runtime.CgroupDriver_SYSTEMD
	}
	log.G(ctx).Debugf("no runtime handler provided cgroup driver setting, using auto-detected %s", runtime.CgroupDriver_name[int32(d)])
	return d
}

func getCgroupDriverFromRuntimeHandlerOpts(opts interface{}) (runtime.CgroupDriver, bool) {
	switch v := opts.(type) {
	case *runcoptions.Options:
		systemdCgroup := v.SystemdCgroup
		if systemdCgroup {
			return runtime.CgroupDriver_SYSTEMD, true
		}
		return runtime.CgroupDriver_CGROUPFS, true
	}
	return runtime.CgroupDriver_SYSTEMD, false
}