/*
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"

	"github.com/containerd/console"
	"github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/runtime/proc"
	"github.com/pkg/errors"
)

type initState interface {
	Resize(console.WinSize) error
	Start(context.Context) error
	Delete(context.Context) error
	Exec(context.Context, string, *ExecConfig) (proc.Process, error)
	Kill(context.Context, uint32, bool) error
	SetExited(int)
}

type createdState struct {
	p *Init
}

func (s *createdState) transition(name string) error {
	switch name {
	case "running":
		s.p.initState = &runningState{p: s.p}
	case "stopped":
		s.p.initState = &stoppedState{p: s.p}
	case "deleted":
		s.p.initState = &deletedState{}
	default:
		return errors.Errorf("invalid state transition %q to %q", stateName(s), name)
	}
	return nil
}

func (s *createdState) Resize(ws console.WinSize) error {
	return s.p.resize(ws)
}

func (s *createdState) Start(ctx context.Context) error {
	if err := s.p.start(ctx); err != nil {
		// Containerd doesn't allow deleting container in created state.
		// However, for gvisor, a non-root container in created state can
		// only go to running state. If the container can't be started,
		// it can only stay in created state, and never be deleted.
		// To work around that, we treat non-root container in start failure
		// state as stopped.
		if !s.p.Sandbox {
			s.p.io.Close()
			s.p.setExited(internalErrorCode)
			if err := s.transition("stopped"); err != nil {
				panic(err)
			}
		}
		return err
	}
	return s.transition("running")
}

func (s *createdState) Delete(ctx context.Context) error {
	if err := s.p.delete(ctx); err != nil {
		return err
	}
	return s.transition("deleted")
}

func (s *createdState) Kill(ctx context.Context, sig uint32, all bool) error {
	return s.p.kill(ctx, sig, all)
}

func (s *createdState) SetExited(status int) {
	s.p.setExited(status)

	if err := s.transition("stopped"); err != nil {
		panic(err)
	}
}

func (s *createdState) Exec(ctx context.Context, path string, r *ExecConfig) (proc.Process, error) {
	return s.p.exec(ctx, path, r)
}

type runningState struct {
	p *Init
}

func (s *runningState) transition(name string) error {
	switch name {
	case "stopped":
		s.p.initState = &stoppedState{p: s.p}
	default:
		return errors.Errorf("invalid state transition %q to %q", stateName(s), name)
	}
	return nil
}

func (s *runningState) Resize(ws console.WinSize) error {
	return s.p.resize(ws)
}

func (s *runningState) Start(ctx context.Context) error {
	return errors.Errorf("cannot start a running process")
}

func (s *runningState) Delete(ctx context.Context) error {
	return errors.Errorf("cannot delete a running process")
}

func (s *runningState) Kill(ctx context.Context, sig uint32, all bool) error {
	return s.p.kill(ctx, sig, all)
}

func (s *runningState) SetExited(status int) {
	s.p.setExited(status)

	if err := s.transition("stopped"); err != nil {
		panic(err)
	}
}

func (s *runningState) Exec(ctx context.Context, path string, r *ExecConfig) (proc.Process, error) {
	return s.p.exec(ctx, path, r)
}

type stoppedState struct {
	p *Init
}

func (s *stoppedState) transition(name string) error {
	switch name {
	case "deleted":
		s.p.initState = &deletedState{}
	default:
		return errors.Errorf("invalid state transition %q to %q", stateName(s), name)
	}
	return nil
}

func (s *stoppedState) Resize(ws console.WinSize) error {
	return errors.Errorf("cannot resize a stopped container")
}

func (s *stoppedState) Start(ctx context.Context) error {
	return errors.Errorf("cannot start a stopped process")
}

func (s *stoppedState) Delete(ctx context.Context) error {
	if err := s.p.delete(ctx); err != nil {
		return err
	}
	return s.transition("deleted")
}

func (s *stoppedState) Kill(ctx context.Context, sig uint32, all bool) error {
	return errdefs.ToGRPCf(errdefs.ErrNotFound, "process %s not found", s.p.id)
}

func (s *stoppedState) SetExited(status int) {
	// no op
}

func (s *stoppedState) Exec(ctx context.Context, path string, r *ExecConfig) (proc.Process, error) {
	return nil, errors.Errorf("cannot exec in a stopped state")
}