/*
Copyright The containerd Authors.
Copyright 2018 Google LLC

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

    https://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 proc

import (
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sync"
	"syscall"
	"time"

	"github.com/containerd/console"
	"github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/runtime/proc"
	"github.com/containerd/containerd/runtime/v1/shim"
	"github.com/containerd/fifo"
	runc "github.com/containerd/go-runc"
	specs "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/pkg/errors"
	"golang.org/x/sys/unix"

	runsc "github.com/google/gvisor-containerd-shim/pkg/go-runsc"
)

type execProcess struct {
	wg sync.WaitGroup

	proc.State

	mu          sync.Mutex
	id          string
	console     console.Console
	io          runc.IO
	status      int
	exited      time.Time
	pid         int
	internalPid int
	closers     []io.Closer
	stdin       io.Closer
	stdio       proc.Stdio
	path        string
	spec        specs.Process

	parent    *Init
	waitBlock chan struct{}
}

func (e *execProcess) Wait() {
	<-e.waitBlock
}

func (e *execProcess) ID() string {
	return e.id
}

func (e *execProcess) Pid() int {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.pid
}

func (e *execProcess) ExitStatus() int {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.status
}

func (e *execProcess) ExitedAt() time.Time {
	e.mu.Lock()
	defer e.mu.Unlock()
	return e.exited
}

func (e *execProcess) setExited(status int) {
	e.status = status
	e.exited = time.Now()
	e.parent.Platform.ShutdownConsole(context.Background(), e.console)
	close(e.waitBlock)
}

func (e *execProcess) delete(ctx context.Context) error {
	e.wg.Wait()
	if e.io != nil {
		for _, c := range e.closers {
			c.Close()
		}
		e.io.Close()
	}
	pidfile := filepath.Join(e.path, fmt.Sprintf("%s.pid", e.id))
	// silently ignore error
	os.Remove(pidfile)
	internalPidfile := filepath.Join(e.path, fmt.Sprintf("%s-internal.pid", e.id))
	// silently ignore error
	os.Remove(internalPidfile)
	return nil
}

func (e *execProcess) resize(ws console.WinSize) error {
	if e.console == nil {
		return nil
	}
	return e.console.Resize(ws)
}

func (e *execProcess) kill(ctx context.Context, sig uint32, _ bool) error {
	internalPid := e.internalPid
	if internalPid != 0 {
		if err := e.parent.runtime.Kill(ctx, e.parent.id, int(sig), &runsc.KillOpts{
			Pid: internalPid,
		}); err != nil {
			// If this returns error, consider the process has already stopped.
			// TODO: Fix after signal handling is fixed.
			return errors.Wrapf(errdefs.ErrNotFound, err.Error())
		}
	}
	return nil
}

func (e *execProcess) Stdin() io.Closer {
	return e.stdin
}

func (e *execProcess) Stdio() proc.Stdio {
	return e.stdio
}

func (e *execProcess) start(ctx context.Context) (err error) {
	var (
		socket          *runc.Socket
		pidfile         = filepath.Join(e.path, fmt.Sprintf("%s.pid", e.id))
		internalPidfile = filepath.Join(e.path, fmt.Sprintf("%s-internal.pid", e.id))
	)
	if e.stdio.Terminal {
		if socket, err = runc.NewTempConsoleSocket(); err != nil {
			return errors.Wrap(err, "failed to create runc console socket")
		}
		defer socket.Close()
	} else if e.stdio.IsNull() {
		if e.io, err = runc.NewNullIO(); err != nil {
			return errors.Wrap(err, "creating new NULL IO")
		}
	} else {
		if e.io, err = runc.NewPipeIO(e.parent.IoUID, e.parent.IoGID, withConditionalIO(e.stdio)); err != nil {
			return errors.Wrap(err, "failed to create runc io pipes")
		}
	}
	opts := &runsc.ExecOpts{
		PidFile:         pidfile,
		InternalPidFile: internalPidfile,
		IO:              e.io,
		Detach:          true,
	}
	if socket != nil {
		opts.ConsoleSocket = socket
	}
	eventCh := shim.Default.Subscribe()
	defer func() {
		// Unsubscribe if an error is returned.
		if err != nil {
			shim.Default.Unsubscribe(eventCh)
		}
	}()
	if err := e.parent.runtime.Exec(ctx, e.parent.id, e.spec, opts); err != nil {
		close(e.waitBlock)
		return e.parent.runtimeError(err, "OCI runtime exec failed")
	}
	if e.stdio.Stdin != "" {
		sc, err := fifo.OpenFifo(ctx, e.stdio.Stdin, syscall.O_WRONLY|syscall.O_NONBLOCK, 0)
		if err != nil {
			return errors.Wrapf(err, "failed to open stdin fifo %s", e.stdio.Stdin)
		}
		e.closers = append(e.closers, sc)
		e.stdin = sc
	}
	var copyWaitGroup sync.WaitGroup
	if socket != nil {
		console, err := socket.ReceiveMaster()
		if err != nil {
			return errors.Wrap(err, "failed to retrieve console master")
		}
		if e.console, err = e.parent.Platform.CopyConsole(ctx, console, e.stdio.Stdin, e.stdio.Stdout, e.stdio.Stderr, &e.wg, &copyWaitGroup); err != nil {
			return errors.Wrap(err, "failed to start console copy")
		}
	} else if !e.stdio.IsNull() {
		if err := copyPipes(ctx, e.io, e.stdio.Stdin, e.stdio.Stdout, e.stdio.Stderr, &e.wg, &copyWaitGroup); err != nil {
			return errors.Wrap(err, "failed to start io pipe copy")
		}
	}
	copyWaitGroup.Wait()
	pid, err := runc.ReadPidFile(opts.PidFile)
	if err != nil {
		return errors.Wrap(err, "failed to retrieve OCI runtime exec pid")
	}
	e.pid = pid
	internalPid, err := runc.ReadPidFile(opts.InternalPidFile)
	if err != nil {
		return errors.Wrap(err, "failed to retrieve OCI runtime exec internal pid")
	}
	e.internalPid = internalPid
	go func() {
		defer shim.Default.Unsubscribe(eventCh)
		for event := range eventCh {
			if event.Pid == e.pid {
				ExitCh <- Exit{
					Timestamp: event.Timestamp,
					ID:        e.id,
					Status:    event.Status,
				}
				break
			}
		}
	}()
	return nil
}

func (e *execProcess) Status(ctx context.Context) (string, error) {
	e.mu.Lock()
	defer e.mu.Unlock()
	// if we don't have a pid then the exec process has just been created
	if e.pid == 0 {
		return "created", nil
	}
	// if we have a pid and it can be signaled, the process is running
	// TODO(random-liu): Use `runsc kill --pid`.
	if err := unix.Kill(e.pid, 0); err == nil {
		return "running", nil
	}
	// else if we have a pid but it can nolonger be signaled, it has stopped
	return "stopped", nil
}