package oci

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"syscall"

	"github.com/crosbymichael/go-runc"
	"github.com/docker/containerd/execution"
	"github.com/docker/containerd/sys"
)

const (
	initProcessID = "init"
)

const (
	PidFilename       = "pid"
	StartTimeFilename = "starttime"
)

var (
	ErrRootEmpty = errors.New("oci: runtime root cannot be an empty string")
)

func New(root string) (*OCIRuntime, error) {
	err := sys.SetSubreaper(1)
	if err != nil {
		return nil, err
	}
	go func() {
		syscall.Wait4(-1, nil, 0, nil)
	}()
	return &OCIRuntime{
		root: root,
		runc: &runc.Runc{
			Root: filepath.Join(root, "runc"),
		},
		ios: make(map[string]OIO),
	}, nil
}

type OCIRuntime struct {
	root string
	runc *runc.Runc
	ios  map[string]OIO // ios tracks created process io for cleanup purpose on delete
}

func (r *OCIRuntime) Create(ctx context.Context, id string, o execution.CreateOpts) (container *execution.Container, err error) {
	if o.Bundle == "" {
		return nil, errors.New("bundle path cannot be an empty string")
	}
	oio, err := newOIO(o.Stdin, o.Stdout, o.Stderr, o.Console)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			oio.cleanup()
		}
	}()

	if container, err = execution.NewContainer(r.root, id, o.Bundle); err != nil {
		return nil, err
	}
	defer func(c *execution.Container) {
		if err != nil {
			c.StateDir().Delete()
		}
	}(container)

	initStateDir, err := container.StateDir().NewProcess(initProcessID)
	if err != nil {
		return nil, err
	}
	pidFile := filepath.Join(initStateDir, PidFilename)
	err = r.runc.Create(ctx, id, o.Bundle, &runc.CreateOpts{
		PidFile: pidFile,
		Console: oio.console,
		IO:      oio.rio,
	})
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			r.runc.Kill(ctx, id, int(syscall.SIGKILL))
			r.runc.Delete(ctx, id)
		}
	}()

	process, err := newProcess(initProcessID, initStateDir, execution.Created)
	if err != nil {
		return nil, err
	}

	container.AddProcess(process, true)

	r.ios[id] = oio

	return container, nil
}

func (r *OCIRuntime) Start(ctx context.Context, c *execution.Container) error {
	return r.runc.Start(ctx, c.ID())
}

func (r *OCIRuntime) Status(ctx context.Context, c *execution.Container) (execution.Status, error) {
	state, err := r.runc.State(ctx, c.ID())
	if err != nil {
		return "", err
	}
	return execution.Status(state.Status), nil
}

func (r *OCIRuntime) load(runcC *runc.Container) (*execution.Container, error) {
	container := execution.LoadContainer(
		execution.StateDir(filepath.Join(r.root, runcC.ID)),
		runcC.ID,
		runcC.Bundle,
		execution.Status(runcC.Status),
	)

	dirs, err := container.StateDir().Processes()
	if err != nil {
		return nil, err
	}
	for _, d := range dirs {
		process, err := newProcess(filepath.Base(d), d, execution.Running)
		if err != nil {
			return nil, err
		}
		container.AddProcess(process, process.Pid() == int64(runcC.Pid))
	}

	return container, nil
}

func (r *OCIRuntime) List(ctx context.Context) ([]*execution.Container, error) {
	runcCs, err := r.runc.List(ctx)
	if err != nil {
		return nil, err
	}

	var containers []*execution.Container
	for _, c := range runcCs {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
			container, err := r.load(c)
			if err != nil {
				return nil, err
			}
			containers = append(containers, container)
		}
	}

	return containers, nil
}

func (r *OCIRuntime) Load(ctx context.Context, id string) (*execution.Container, error) {
	runcC, err := r.runc.State(ctx, id)
	if err != nil {
		return nil, err
	}

	return r.load(runcC)
}

func (r *OCIRuntime) Delete(ctx context.Context, c *execution.Container) error {
	id := c.ID()
	if err := r.runc.Delete(ctx, id); err != nil {
		return err
	}
	c.StateDir().Delete()
	r.ios[id].cleanup()
	delete(r.ios, id)
	return nil
}

func (r *OCIRuntime) Pause(ctx context.Context, c *execution.Container) error {
	return r.runc.Pause(ctx, c.ID())
}

func (r *OCIRuntime) Resume(ctx context.Context, c *execution.Container) error {
	return r.runc.Resume(ctx, c.ID())
}

func (r *OCIRuntime) StartProcess(ctx context.Context, c *execution.Container, o execution.StartProcessOpts) (p execution.Process, err error) {
	oio, err := newOIO(o.Stdin, o.Stdout, o.Stderr, o.Console)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			oio.cleanup()
		}
	}()

	procStateDir, err := c.StateDir().NewProcess(o.ID)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			c.StateDir().DeleteProcess(o.ID)
		}
	}()

	pidFile := filepath.Join(procStateDir, PidFilename)
	if err := r.runc.Exec(ctx, c.ID(), o.Spec, &runc.ExecOpts{
		PidFile: pidFile,
		Detach:  false,
		Console: oio.console,
		Cwd:     o.Spec.Cwd,
		IO:      oio.rio,
	}); err != nil {
		return nil, err
	}

	process, err := newProcess(o.ID, procStateDir, execution.Running)
	if err != nil {
		return nil, err
	}

	c.AddProcess(process, false)

	r.ios[fmt.Sprintf("%s-%s", c.ID(), process.ID())] = oio

	return process, nil
}

func (r *OCIRuntime) SignalProcess(ctx context.Context, c *execution.Container, id string, sig os.Signal) error {
	process := c.GetProcess(id)
	if process == nil {
		return fmt.Errorf("Make a Process Not Found error")
	}
	return syscall.Kill(int(process.Pid()), sig.(syscall.Signal))
}

func (r *OCIRuntime) DeleteProcess(ctx context.Context, c *execution.Container, id string) error {
	ioID := fmt.Sprintf("%s-%s", c.ID(), id)
	r.ios[ioID].cleanup()
	delete(r.ios, ioID)
	c.RemoveProcess(id)
	return c.StateDir().DeleteProcess(id)
}