// Copyright 2020 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 dockerutil

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"syscall"
	"time"
)

// profile represents profile-like operations on a container.
//
// It is meant to be added to containers such that the container type calls
// the profile during its lifecycle. Standard implementations are below.

// profile is for running profiles with 'runsc debug'.
type profile struct {
	BasePath string
	Types    []string
	Duration time.Duration
	cmd      *exec.Cmd
}

// profileInit initializes a profile object, if required.
func (c *Container) profileInit() {
	if !*pprofBlock && !*pprofCPU && !*pprofMutex && !*pprofHeap {
		return // Nothing to do.
	}
	c.profile = &profile{
		BasePath: filepath.Join(*pprofBaseDir, c.runtime, c.Name),
		Duration: *pprofDuration,
	}
	if *pprofCPU {
		c.profile.Types = append(c.profile.Types, "cpu")
	}
	if *pprofHeap {
		c.profile.Types = append(c.profile.Types, "heap")
	}
	if *pprofMutex {
		c.profile.Types = append(c.profile.Types, "mutex")
	}
	if *pprofBlock {
		c.profile.Types = append(c.profile.Types, "block")
	}
}

// createProcess creates the collection process.
func (p *profile) createProcess(c *Container) error {
	// Ensure our directory exists.
	if err := os.MkdirAll(p.BasePath, 0755); err != nil {
		return err
	}

	// Find the runtime to invoke.
	path, err := RuntimePath()
	if err != nil {
		return fmt.Errorf("failed to get runtime path: %v", err)
	}

	// The root directory of this container's runtime.
	root := fmt.Sprintf("--root=/var/run/docker/runtime-%s/moby", c.runtime)

	// Format is `runsc --root=rootdir debug --profile-*=file --duration=24h containerID`.
	args := []string{root, "debug"}
	for _, profileArg := range p.Types {
		outputPath := filepath.Join(p.BasePath, fmt.Sprintf("%s.pprof", profileArg))
		args = append(args, fmt.Sprintf("--profile-%s=%s", profileArg, outputPath))
	}
	args = append(args, fmt.Sprintf("--duration=%s", p.Duration)) // Or until container exits.
	args = append(args, c.ID())

	// Best effort wait until container is running.
	for now := time.Now(); time.Since(now) < 5*time.Second; {
		if status, err := c.Status(context.Background()); err != nil {
			return fmt.Errorf("failed to get status with: %v", err)
		} else if status.Running {
			break
		}
		time.Sleep(100 * time.Millisecond)
	}
	p.cmd = exec.Command(path, args...)
	p.cmd.Stderr = os.Stderr // Pass through errors.
	if err := p.cmd.Start(); err != nil {
		return fmt.Errorf("start process failed: %v", err)
	}

	return nil
}

// killProcess kills the process, if running.
//
// Precondition: mu must be held.
func (p *profile) killProcess() error {
	if p.cmd != nil && p.cmd.Process != nil {
		return p.cmd.Process.Signal(syscall.SIGTERM)
	}
	return nil
}

// waitProcess waits for the process, if running.
//
// Precondition: mu must be held.
func (p *profile) waitProcess() error {
	defer func() { p.cmd = nil }()
	if p.cmd != nil {
		return p.cmd.Wait()
	}
	return nil
}

// Start is called when profiling is started.
func (p *profile) Start(c *Container) error {
	return p.createProcess(c)
}

// Stop is called when profiling is started.
func (p *profile) Stop(c *Container) error {
	killErr := p.killProcess()
	waitErr := p.waitProcess()
	if waitErr != nil && killErr != nil {
		return killErr
	}
	return waitErr // Ignore okay wait, err kill.
}