// Copyright 2021 The gVisor 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 cgroupfs

import (
	"bytes"
	"fmt"

	"gvisor.dev/gvisor/pkg/context"
	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
	"gvisor.dev/gvisor/pkg/sentry/kernel"
	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
	"gvisor.dev/gvisor/pkg/sentry/usage"
)

// +stateify savable
type memoryController struct {
	controllerCommon
}

var _ controller = (*memoryController)(nil)

func newMemoryController(fs *filesystem) *memoryController {
	c := &memoryController{}
	c.controllerCommon.init(controllerMemory, fs)
	return c
}

// AddControlFiles implements controller.AddControlFiles.
func (c *memoryController) AddControlFiles(ctx context.Context, creds *auth.Credentials, _ *cgroupInode, contents map[string]kernfs.Inode) {
	contents["memory.usage_in_bytes"] = c.fs.newControllerFile(ctx, creds, &memoryUsageInBytesData{})
}

// +stateify savable
type memoryUsageInBytesData struct{}

// Generate implements vfs.DynamicBytesSource.Generate.
func (d *memoryUsageInBytesData) Generate(ctx context.Context, buf *bytes.Buffer) error {
	// TODO(b/183151557): This is a giant hack, we're using system-wide
	// accounting since we know there is only one cgroup.
	k := kernel.KernelFromContext(ctx)
	mf := k.MemoryFile()
	mf.UpdateUsage()
	_, totalBytes := usage.MemoryAccounting.Copy()

	fmt.Fprintf(buf, "%d\n", totalBytes)
	return nil
}