package features

import (
	"context"

	"github.com/centrifugal/centrifuge"
	"github.com/grafana/grafana-plugin-sdk-go/backend"
	"github.com/grafana/grafana/pkg/models"
)

//go:generate mockgen -destination=mock.go -package=features github.com/grafana/grafana/pkg/services/live/features StreamPacketSender,PresenceGetter,PluginContextGetter,StreamRunner

type StreamPacketSender interface {
	Send(channel string, packet *backend.StreamPacket) error
}

type PresenceGetter interface {
	GetNumSubscribers(channel string) (int, error)
}

type PluginContextGetter interface {
	GetPluginContext(user *models.SignedInUser, pluginID string, datasourceUID string) (backend.PluginContext, bool, error)
}

type StreamRunner interface {
	RunStream(ctx context.Context, request *backend.RunStreamRequest, sender backend.StreamPacketSender) error
}

type streamSender struct {
	channel      string
	packetSender StreamPacketSender
}

func newStreamSender(channel string, packetSender StreamPacketSender) *streamSender {
	return &streamSender{
		channel:      channel,
		packetSender: packetSender,
	}
}

func (p *streamSender) Send(packet *backend.StreamPacket) error {
	return p.packetSender.Send(p.channel, packet)
}

// PluginRunner can handle streaming operations for channels belonging to plugins.
type PluginRunner struct {
	pluginID            string
	datasourceUID       string
	pluginContextGetter PluginContextGetter
	handler             backend.StreamHandler
	streamManager       *StreamManager
}

// NewPluginRunner creates new PluginRunner.
func NewPluginRunner(pluginID string, datasourceUID string, streamManager *StreamManager, pluginContextGetter PluginContextGetter, handler backend.StreamHandler) *PluginRunner {
	return &PluginRunner{
		pluginID:            pluginID,
		datasourceUID:       datasourceUID,
		pluginContextGetter: pluginContextGetter,
		handler:             handler,
		streamManager:       streamManager,
	}
}

// GetHandlerForPath gets the handler for a path.
func (m *PluginRunner) GetHandlerForPath(path string) (models.ChannelHandler, error) {
	return &PluginPathRunner{
		path:                path,
		pluginID:            m.pluginID,
		datasourceUID:       m.datasourceUID,
		streamManager:       m.streamManager,
		handler:             m.handler,
		pluginContextGetter: m.pluginContextGetter,
	}, nil
}

// PluginPathRunner can handle streaming operations for channels belonging to plugin specific path.
type PluginPathRunner struct {
	path                string
	pluginID            string
	datasourceUID       string
	streamManager       *StreamManager
	handler             backend.StreamHandler
	pluginContextGetter PluginContextGetter
}

// OnSubscribe passes control to a plugin.
func (r *PluginPathRunner) OnSubscribe(ctx context.Context, user *models.SignedInUser, e models.SubscribeEvent) (models.SubscribeReply, backend.SubscribeStreamStatus, error) {
	pCtx, found, err := r.pluginContextGetter.GetPluginContext(user, r.pluginID, r.datasourceUID)
	if err != nil {
		logger.Error("Get plugin context error", "error", err, "path", r.path)
		return models.SubscribeReply{}, 0, err
	}
	if !found {
		logger.Error("Plugin context not found", "path", r.path)
		return models.SubscribeReply{}, 0, centrifuge.ErrorInternal
	}
	resp, err := r.handler.SubscribeStream(ctx, &backend.SubscribeStreamRequest{
		PluginContext: pCtx,
		Path:          r.path,
	})
	if err != nil {
		logger.Error("Plugin OnSubscribe call error", "error", err, "path", r.path)
		return models.SubscribeReply{}, 0, err
	}
	if resp.Status != backend.SubscribeStreamStatusOK {
		return models.SubscribeReply{}, resp.Status, nil
	}

	if resp.UseRunStream {
		submitResult, err := r.streamManager.SubmitStream(ctx, e.Channel, r.path, pCtx, r.handler)
		if err != nil {
			logger.Error("Error submitting stream to manager", "error", err, "path", r.path)
			return models.SubscribeReply{}, 0, centrifuge.ErrorInternal
		}
		if submitResult.StreamExists {
			logger.Debug("Skip running new stream (already exists)", "path", r.path)
		} else {
			logger.Debug("Running a new keepalive stream", "path", r.path)
		}
	}

	reply := models.SubscribeReply{
		Presence: resp.UseRunStream, // only enable presence for streams with UseRunStream on at the moment.
		Data:     resp.Data,
	}
	return reply, backend.SubscribeStreamStatusOK, nil
}

// OnPublish passes control to a plugin.
func (r *PluginPathRunner) OnPublish(ctx context.Context, user *models.SignedInUser, e models.PublishEvent) (models.PublishReply, backend.PublishStreamStatus, error) {
	pCtx, found, err := r.pluginContextGetter.GetPluginContext(user, r.pluginID, r.datasourceUID)
	if err != nil {
		logger.Error("Get plugin context error", "error", err, "path", r.path)
		return models.PublishReply{}, 0, err
	}
	if !found {
		logger.Error("Plugin context not found", "path", r.path)
		return models.PublishReply{}, 0, centrifuge.ErrorInternal
	}
	resp, err := r.handler.PublishStream(ctx, &backend.PublishStreamRequest{
		PluginContext: pCtx,
		Path:          r.path,
		Data:          e.Data,
	})
	if err != nil {
		logger.Error("Plugin OnPublish call error", "error", err, "path", r.path)
		return models.PublishReply{}, 0, err
	}
	if resp.Status != backend.PublishStreamStatusOK {
		return models.PublishReply{}, resp.Status, nil
	}
	return models.PublishReply{Data: resp.Data}, backend.PublishStreamStatusOK, nil
}