package docker

import (
	"context"
	"fmt"
	"io"
	"sync"

	"emperror.dev/errors"
	"github.com/apex/log"
	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"github.com/pterodactyl/wings/api"
	"github.com/pterodactyl/wings/environment"
	"github.com/pterodactyl/wings/events"
	"github.com/pterodactyl/wings/system"
)

type Metadata struct {
	Image string
	Stop  api.ProcessStopConfiguration
}

// Ensure that the Docker environment is always implementing all of the methods
// from the base environment interface.
var _ environment.ProcessEnvironment = (*Environment)(nil)

type Environment struct {
	mu      sync.RWMutex
	eventMu sync.Once

	// The public identifier for this environment. In this case it is the Docker container
	// name that will be used for all instances created under it.
	Id string

	// The environment configuration.
	Configuration *environment.Configuration

	meta *Metadata

	// The Docker client being used for this instance.
	client *client.Client

	// Controls the hijacked response stream which exists only when we're attached to
	// the running container instance.
	stream *types.HijackedResponse

	// Holds the stats stream used by the polling commands so that we can easily close it out.
	stats io.ReadCloser

	emitter *events.EventBus

	// Tracks the environment state.
	st *system.AtomicString
}

// Creates a new base Docker environment. The ID passed through will be the ID that is used to
// reference the container from here on out. This should be unique per-server (we use the UUID
// by default). The container does not need to exist at this point.
func New(id string, m *Metadata, c *environment.Configuration) (*Environment, error) {
	cli, err := environment.Docker()
	if err != nil {
		return nil, err
	}

	e := &Environment{
		Id:            id,
		Configuration: c,
		meta:          m,
		client:        cli,
		st:            system.NewAtomicString(environment.ProcessOfflineState),
	}

	return e, nil
}

func (e *Environment) log() *log.Entry {
	return log.WithField("environment", e.Type()).WithField("container_id", e.Id)
}

func (e *Environment) Type() string {
	return "docker"
}

// Set if this process is currently attached to the process.
func (e *Environment) SetStream(s *types.HijackedResponse) {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.stream = s
}

// Determine if the this process is currently attached to the container.
func (e *Environment) IsAttached() bool {
	e.mu.RLock()
	defer e.mu.RUnlock()

	return e.stream != nil
}

func (e *Environment) Events() *events.EventBus {
	e.eventMu.Do(func() {
		e.emitter = events.New()
	})

	return e.emitter
}

// Determines if the container exists in this environment. The ID passed through should be the
// server UUID since containers are created utilizing the server UUID as the name and docker
// will work fine when using the container name as the lookup parameter in addition to the longer
// ID auto-assigned when the container is created.
func (e *Environment) Exists() (bool, error) {
	_, err := e.client.ContainerInspect(context.Background(), e.Id)

	if err != nil {
		// If this error is because the container instance wasn't found via Docker we
		// can safely ignore the error and just return false.
		if client.IsErrNotFound(err) {
			return false, nil
		}

		return false, err
	}

	return true, nil
}

// Determines if the server's docker container is currently running. If there is no container
// present, an error will be raised (since this shouldn't be a case that ever happens under
// correctly developed circumstances).
//
// You can confirm if the instance wasn't found by using client.IsErrNotFound from the Docker
// API.
//
// @see docker/client/errors.go
func (e *Environment) IsRunning() (bool, error) {
	c, err := e.client.ContainerInspect(context.Background(), e.Id)
	if err != nil {
		return false, err
	}

	return c.State.Running, nil
}

// Determine the container exit state and return the exit code and whether or not
// the container was killed by the OOM killer.
func (e *Environment) ExitState() (uint32, bool, error) {
	c, err := e.client.ContainerInspect(context.Background(), e.Id)
	if err != nil {
		// I'm not entirely sure how this can happen to be honest. I tried deleting a
		// container _while_ a server was running and wings gracefully saw the crash and
		// created a new container for it.
		//
		// However, someone reported an error in Discord about this scenario happening,
		// so I guess this should prevent it? They didn't tell me how they caused it though
		// so that's a mystery that will have to go unsolved.
		//
		// @see https://github.com/pterodactyl/panel/issues/2003
		if client.IsErrNotFound(err) {
			return 1, false, nil
		}

		return 0, false, err
	}

	return uint32(c.State.ExitCode), c.State.OOMKilled, nil
}

// Returns the environment configuration allowing a process to make modifications of the
// environment on the fly.
func (e *Environment) Config() *environment.Configuration {
	e.mu.RLock()
	defer e.mu.RUnlock()

	return e.Configuration
}

// Sets the stop configuration for the environment.
func (e *Environment) SetStopConfiguration(c api.ProcessStopConfiguration) {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.meta.Stop = c
}

func (e *Environment) SetImage(i string) {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.meta.Image = i
}

func (e *Environment) State() string {
	return e.st.Load()
}

// SetState sets the state of the environment. This emits an event that server's
// can hook into to take their own actions and track their own state based on
// the environment.
func (e *Environment) SetState(state string) {
	if state != environment.ProcessOfflineState &&
		state != environment.ProcessStartingState &&
		state != environment.ProcessRunningState &&
		state != environment.ProcessStoppingState {
		panic(errors.New(fmt.Sprintf("invalid server state received: %s", state)))
	}

	// Emit the event to any listeners that are currently registered.
	if e.State() != state {
		// If the state changed make sure we update the internal tracking to note that.
		e.st.Store(state)
		e.Events().Publish(environment.StateChangeEvent, state)
	}
}