package gstreamer

import (
	"context"
	"errors"

	"github.com/tinyzimmer/go-glib/glib"
	"github.com/tinyzimmer/go-gst/gst"
)

var gstreamer *Gstreamer

func Init() *Gstreamer {
	gst.Init(nil)
	mainLoop := glib.NewMainLoop(glib.MainContextDefault(), false)
	go mainLoop.Run()
	decklink := &Decklink{
		Slots: map[string]string{"one": ""},
	}
	gstreamer = &Gstreamer{
		ctx:            context.Background(),
		Pipelines:      map[string]*Pipeline{},
		pipelineSlots:  make(map[string][]string),
		notifyOnUpdate: map[string][]NotifyOnPipelineUpdate{},
		Decklink:       decklink,
	}
	return gstreamer
}

func (g *Gstreamer) AddPipeline(pipeline *Pipeline) {
	g.Lock()
	defer g.Unlock()

	if _, ok := g.pipelineSlots[pipeline.Name]; ok {
		g.pipelineSlots[pipeline.Name] = append(g.pipelineSlots[pipeline.Name], pipeline.ID)
	} else {
		g.pipelineSlots[pipeline.Name] = []string{pipeline.ID}
	}
	g.Pipelines[pipeline.ID] = pipeline
	pipeline.SubscribeToUpdates(g.notifySlotSubscriber())
}

func (g *Gstreamer) DeletePipeline(id string) error {
	g.Lock()
	defer g.Unlock()
	if pipeline, err := g.getPipeline(id); err == nil {
		var i int
		for i := range g.pipelineSlots[pipeline.Name] {
			if g.pipelineSlots[pipeline.Name][i] == pipeline.ID {
				break
			}
		}
		g.pipelineSlots[pipeline.Name] = append(g.pipelineSlots[pipeline.Name][:i], g.pipelineSlots[pipeline.Name][i+1:]...)

		delete(g.Pipelines, id)
		pipeline.ctxCancel()
		return nil
	}
	return errors.New("pipeline not found")
}

func (g *Gstreamer) GetPipeline(id string) (*Pipeline, error) {
	g.RLock()
	defer g.RUnlock()
	return g.getPipeline(id)
}

// only use this if ressource is locked
func (g *Gstreamer) getPipeline(id string) (*Pipeline, error) {
	if pipeline, ok := g.Pipelines[id]; ok {
		return pipeline, nil
	}
	return nil, errors.New("Pipeline not found")
}

func (g *Gstreamer) SubscribeToSlotUpdates(slot string, callback NotifyOnPipelineUpdate) {
	g.Lock()
	defer g.Unlock()
	if _, ok := g.notifyOnUpdate[slot]; ok {
		g.notifyOnUpdate[slot] = append(g.notifyOnUpdate[slot], callback)
	} else {
		g.notifyOnUpdate[slot] = []NotifyOnPipelineUpdate{callback}
	}
}

func (g *Gstreamer) notifySlotSubscriber() NotifyOnPipelineUpdate {
	return func(pipeline *Pipeline) {
		for _, callback := range g.notifyOnUpdate[pipeline.Name] {
			callback(pipeline)
		}
	}
}