package ingest

import (
	"bytes"
	"context"
	"fmt"
	"log/slog"
	"net/url"
	"sync"
	"time"

	"git.koval.net/cyclane/cctv/server/models"
	"github.com/pocketbase/pocketbase/core"
	"github.com/pocketbase/pocketbase/tools/store"
	"golang.org/x/sync/errgroup"
)

type Ingest struct {
	sync.WaitGroup
	app       core.App
	log       *slog.Logger
	pipelines *store.Store[string, *activePipeline]
}

type activePipeline struct {
	stream     *models.Stream
	pipeline   *CameraPipeline
	cancel     context.CancelFunc
	terminated <-chan struct{}
}

func BeginIngest(ctx context.Context, app core.App) *Ingest {
	log := app.Logger().With("svc", "ingest")
	ingest := &Ingest{
		WaitGroup: sync.WaitGroup{},
		app:       app,
		log:       log,
		pipelines: store.New[string, *activePipeline](nil),
	}

	// initialise thumbnail pipelines
	thumbnailStreams := map[string]*models.Stream{}
	streams := []*models.Stream{}
	err := app.RunInTransaction(func(txApp core.App) error {
		if err := txApp.RecordQuery("streams").All(&streams); err != nil {
			return fmt.Errorf("failed to fetch stream records: %w", err)
		}
		for _, stream := range streams {
			other, ok := thumbnailStreams[stream.CameraID()]
			if !ok || thumbnailStreamScore(stream) < thumbnailStreamScore(other) {
				thumbnailStreams[stream.CameraID()] = stream
			}
		}

		streamRecords := make([]*core.Record, len(streams))
		for i, stream := range streams {
			streamRecords[i] = stream.Record
		}
		if errs := txApp.ExpandRecords(streamRecords, []string{"camera"}, nil); len(errs) > 0 {
			return fmt.Errorf("failed to expand camera relation for stream records: %v", errs)
		}

		return nil
	})
	if err != nil {
		log.Error("Failed to initialize stream pipelines", "error", err)
		return ingest
	}

	group := errgroup.Group{}
	for _, stream := range streams {
		group.Go(func() error {
			log := log.With("stream", stream.Id)
			rtspUrl, err := url.Parse(stream.URL())
			if err != nil {
				return fmt.Errorf("failed to parse stream URL for stream %s: %w", stream.Id, err)
			}
			password, err := stream.Camera().Password(app.EncryptionEnv())
			if err != nil {
				return fmt.Errorf("failed to decrypt camera password for stream %s: %w", stream.Id, err)
			}
			rtspUrl.User = url.UserPassword(stream.Camera().Username(), password)
			pipeline, err := CreatePipeline(log)
			if err != nil {
				return fmt.Errorf("failed to create pipeline for stream %s: %w", stream.Id, err)
			}
			if err := pipeline.addRtspSource(rtspUrl); err != nil {
				return fmt.Errorf("failed to add RTSP source to pipeline for stream %s: %w", stream.Id, err)
			}
			consumers := false
			if thumbnailStream, ok := thumbnailStreams[stream.CameraID()]; ok && thumbnailStream.Id == stream.Id {
				consumers = true
				if err := pipeline.addThumbnailBranch(480, 270, 1000*time.Millisecond, 20*time.Second); err != nil {
					return fmt.Errorf("failed to add thumbnail branch to pipeline for stream %s: %w", stream.Id, err)
				}
			}
			if err := pipeline.addLiveBranch(20 * time.Second); err != nil {
				return fmt.Errorf("failed to add live branch to pipeline for stream %s: %w", stream.Id, err)
			}

			if consumers {
				log.Info("Starting pipeline for stream with consumers.")
			} else {
				log.Info("Stream has no consumers, ignoring pipeline.")
				pipeline.Close()
				return nil
			}
			pipelineCtx, cancel := context.WithCancel(ctx)
			terminated := make(chan struct{})
			ingest.pipelines.Set(stream.Id, &activePipeline{
				stream:     stream,
				pipeline:   pipeline,
				cancel:     cancel,
				terminated: terminated,
			})
			ingest.WaitGroup.Go(func() {
				if err := pipeline.Run(pipelineCtx); err != nil {
					log.Error("Stream pipeline exited with error", "error", err)
				}
				close(terminated)
			})
			return nil
		})
	}
	if err := group.Wait(); err != nil {
		log.Error("Failed to start ingest pipelines", "error", err)
	}

	return ingest
}

func (ingest *Ingest) GetThumbnail(ctx context.Context, streamId string) (*bytes.Reader, error) {
	active, ok := ingest.pipelines.GetOk(streamId)
	if !ok {
		return nil, fmt.Errorf("no active pipeline for stream %s", streamId)
	}
	thumb, err := active.pipeline.GetThumbnail(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to get thumbnail from pipeline for stream %s: %w", streamId, err)
	}
	return thumb, nil
}

func thumbnailStreamScore(stream *models.Stream) float64 {
	return stream.FPS() * float64(stream.Height()*stream.Width())
}

func (ingest *Ingest) SubscribeLive(ctx context.Context, streamId string) (<-chan *bytes.Reader, error) {
	active, ok := ingest.pipelines.GetOk(streamId)
	if !ok {
		return nil, fmt.Errorf("no active pipeline for stream %s", streamId)
	}
	id, stream, err := active.pipeline.LiveSubscribe(1*time.Second, 16)
	if err != nil {
		return nil, fmt.Errorf("failed to subscribe to live stream %s: %w", streamId, err)
	}
	out := make(chan *bytes.Reader, 16)
	go func() {
		defer close(out)
		defer active.pipeline.LiveUnsubscribe(id)
		for {
			select {
			case <-ctx.Done():
				return
			case buf, ok := <-stream:
				if !ok {
					return
				}
				select {
				case <-ctx.Done():
					return
				case out <- buf:
				}
			}
		}
	}()

	return out, nil
}