package ingest

import (
	"fmt"

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

// addStatsBranch populates the pipeline with:
//
//	[vTee] ---> fakesink
//
// StreamStats are extracted from the fakesink's handovers (using the sink pad caps) and sent to the returned channel.
// If the channel has no received or is full, the stats are dropped to avoid blocking the pipeline. The channel is never closed.
func (p *CameraPipeline) addStatsBranch() (<-chan StreamStats, error) {
	if p.vTee == nil {
		return nil, fmt.Errorf("video tee not initialized")
	}
	vPad := p.vTee.GetRequestPad("src_%u")
	if vPad == nil {
		return nil, fmt.Errorf("failed to get request pad from video tee")
	}

	statsChan := make(chan StreamStats)
	fakeSink, err := gst.NewElement("fakesink")
	if err != nil {
		return nil, fmt.Errorf("failed to create fakesink element: %w", err)
	}
	if err := fakeSink.SetProperty("signal-handoffs", true); err != nil {
		return nil, fmt.Errorf("failed to set fakesink signal-handoffs property: %w", err)
	}

	if err := p.pipeline.Add(fakeSink); err != nil {
		return nil, fmt.Errorf("failed to add fakesink to pipeline: %w", err)
	}

	if res := vPad.Link(fakeSink.GetStaticPad("sink")); res != gst.PadLinkOK {
		return nil, fmt.Errorf("failed to link video tee to fakesink: %s", res)
	}

	fakeSink.Connect("handoff", func(element *gst.Element, _ *gst.Buffer, pad *gst.Pad) {
		caps := pad.GetCurrentCaps()
		if caps == nil || caps.GetSize() == 0 {
			p.log.Error("Stats pad has no or empty caps")
			return
		}
		if caps.GetSize() > 1 {
			// Note: should be impossible
			p.log.Warn("Stats pad has multiple structures, using the first one", "caps", caps.String())
		}
		structure := caps.GetStructureAt(0)
		if structure == nil {
			p.log.Error("Stats pad received nil structure")
			return
		}

		rawWidth, err := structure.GetValue("width")
		if err != nil {
			p.log.Error("Failed to get width from stats pad caps", "error", err)
			return
		}
		width, ok := rawWidth.(int)
		if !ok {
			p.log.Error("Width field in stats pad caps is not an int", "value", rawWidth)
			return
		}

		rawHeight, err := structure.GetValue("height")
		if err != nil {
			p.log.Error("Failed to get height from stats pad caps", "error", err)
			return
		}
		height, ok := rawHeight.(int)
		if !ok {
			p.log.Error("Height field in stats pad caps is not an int", "value", rawHeight)
			return
		}

		fps, err := structure.GetValue("framerate")
		if err != nil {
			p.log.Error("Failed to get framerate from stats pad caps", "error", err)
			return
		}

		var fpsFloat float64
		switch v := fps.(type) {
		case *gst.FractionValue:
			fpsFloat = float64(v.Num()) / float64(v.Denom())
		case gst.FractionValue:
			fpsFloat = float64(v.Num()) / float64(v.Denom())
		case float64:
			fpsFloat = v
		default:
			p.log.Error("Framerate field in stats pad caps is not a fraction or float", "type", fmt.Sprintf("%T", fps), "value", fps)
			return
		}

		select {

		case statsChan <- StreamStats{
			FPS:    fpsFloat,
			Width:  width,
			Height: height,
		}:
		default:
			p.log.Warn("Stats channel is full, dropping stats update")
		}
		return
	})
	return statsChan, nil
}