// Copyright 2018 The containerd Authors.
// Copyright 2018 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
//
//     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/fifo"
	runc "github.com/containerd/go-runc"
	specs "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/pkg/errors"
	"golang.org/x/sys/unix"

	"gvisor.dev/gvisor/pkg/shim/runsc"
)

type execProcess struct {
	wg sync.WaitGroup

	execState execState

	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.mu.Lock()
	defer e.mu.Unlock()

	e.execState.SetExited(status)
}

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.mu.Lock()
	defer e.mu.Unlock()

	return e.execState.Delete(ctx)
}

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 {
	e.mu.Lock()
	defer e.mu.Unlock()

	return e.execState.Resize(ws)
}

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 {
	e.mu.Lock()
	defer e.mu.Unlock()

	return e.execState.Kill(ctx, sig, false)
}

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) error {
	e.mu.Lock()
	defer e.mu.Unlock()

	return e.execState.Start(ctx)
}

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 := e.parent.Monitor.Subscribe()
	defer func() {
		// Unsubscribe if an error is returned.
		if err != nil {
			e.parent.Monitor.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(context.Background(), 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
	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()
	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 e.parent.Monitor.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
}