package main

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"frame"

	"maunium.net/go/mautrix"
	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/id"
)

// matrixStore posts clips into Matrix rooms as m.video events. The clips and
// detections rooms carry full JSON metadata in an m.text reply posted directly
// beneath each video event; the view room carries only a one-line human caption
// so clips can be browsed without scrolling through JSON.
type matrixStore struct {
	client         *mautrix.Client
	clipsRoom      id.RoomID
	detectionsRoom id.RoomID
	viewRoom       id.RoomID
}

// newMatrixStore builds an authenticated Matrix client and verifies the
// access token against the homeserver so that misconfiguration fails fast
// at startup instead of on the first clip.
func newMatrixStore(homeserver, userID, token, clipsRoom, detectionsRoom, viewRoom string) (*matrixStore, error) {
	cli, err := mautrix.NewClient(homeserver, id.UserID(userID), token)
	if err != nil {
		return nil, fmt.Errorf("matrix client: %w", err)
	}
	cli.StateStore = mautrix.NewMemoryStateStore()

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	if _, err := cli.Whoami(ctx); err != nil {
		return nil, fmt.Errorf("matrix auth check: %w", err)
	}

	for _, room := range []string{clipsRoom, detectionsRoom, viewRoom} {
		if !strings.HasPrefix(room, "!") {
			return nil, fmt.Errorf("invalid room ID %q (must start with '!')", room)
		}
	}

	return &matrixStore{
		client:         cli,
		clipsRoom:      id.RoomID(clipsRoom),
		detectionsRoom: id.RoomID(detectionsRoom),
		viewRoom:       id.RoomID(viewRoom),
	}, nil
}

// uploadClip uploads a clip's MP4 to the homeserver media repository once and
// returns the mxc:// URI so every target room can reference the same media.
func (ms *matrixStore) uploadClip(ctx context.Context, filename string, mp4 []byte) (id.ContentURI, error) {
	resp, err := ms.client.UploadBytesWithName(ctx, mp4, "video/mp4", filename)
	if err != nil {
		return id.ContentURI{}, fmt.Errorf("upload clip media: %w", err)
	}
	return resp.ContentURI, nil
}

// sendClipToRoom posts a clip's already-uploaded media as an m.video event to
// roomID, then sends the clip's metadata as an m.text reply beneath it. It
// returns the video event ID.
func (ms *matrixStore) sendClipToRoom(ctx context.Context, roomID id.RoomID, clp frame.Clip, filename string, mxc id.ContentURI, mp4Len int, fps float64) (id.EventID, error) {
	videoResp, err := ms.client.SendMessageEvent(ctx, roomID, event.EventMessage, videoContent(filename, mxc, mp4Len))
	if err != nil {
		return "", fmt.Errorf("send clip video event: %w", err)
	}

	meta, err := buildClipMetadata(&clp, fps)
	if err != nil {
		return "", fmt.Errorf("build metadata: %w", err)
	}
	if _, err := ms.client.SendMessageEvent(ctx, roomID, event.EventMessage, metadataContent(videoResp.EventID, meta)); err != nil {
		return "", fmt.Errorf("send metadata reply: %w", err)
	}
	return videoResp.EventID, nil
}

// videoContent renders the m.video event content for an uploaded clip, using
// label as the human-visible body text (the file name, or a short caption).
func videoContent(label string, mxc id.ContentURI, mp4Len int) *event.MessageEventContent {
	return &event.MessageEventContent{
		MsgType: event.MsgVideo,
		Body:    label,
		URL:     mxc.CUString(),
		Info: &event.FileInfo{
			MimeType: "video/mp4",
			Size:     mp4Len,
		},
	}
}

// sendClipView posts a clip's already-uploaded media to roomID as an m.video
// event with a one-line human caption instead of the JSON metadata reply, so
// the room reads as a clean clip feed.
func (ms *matrixStore) sendClipView(ctx context.Context, roomID id.RoomID, clp frame.Clip, mxc id.ContentURI, mp4Len int, fps float64) (id.EventID, error) {
	resp, err := ms.client.SendMessageEvent(ctx, roomID, event.EventMessage, videoContent(viewCaption(&clp, fps), mxc, mp4Len))
	if err != nil {
		return "", fmt.Errorf("send clip view event: %w", err)
	}
	return resp.EventID, nil
}

// viewCaption renders the minimal, human-readable caption used for the view
// room. It carries just enough to identify a clip without any JSON.
func viewCaption(clp *frame.Clip, fps float64) string {
	return fmt.Sprintf("%s · %d frames · %.1f fps · motion %d%%",
		clp.SourceData, len(clp.PixelMats), fps, clp.GetHighestMotion())
}

// metadataContent renders the m.text reply that carries a clip's metadata
// beneath its video event.
func metadataContent(eventID id.EventID, meta string) *event.MessageEventContent {
	return &event.MessageEventContent{
		MsgType: event.MsgText,
		Body:    meta,
		RelatesTo: &event.RelatesTo{
			InReplyTo: &event.InReplyTo{
				EventID: eventID,
			},
		},
	}
}

// routeTargets decides where a clip should be stored. Clips with no motion
// are dropped (empty result). Motion clips land in the clips room and, when
// they also carry classifier detections, additionally in the detections room.
func routeTargets(clp *frame.Clip, clipsRoom, detectionsRoom id.RoomID) []id.RoomID {
	if clp.GetHighestMotion() == 0 {
		return nil
	}
	targets := []id.RoomID{clipsRoom}
	if hasDetections(clp) {
		targets = append(targets, detectionsRoom)
	}
	return targets
}

// hasDetections reports whether any frame in the clip carries at least one
// classifier detection.
func hasDetections(clp *frame.Clip) bool {
	for _, frameDets := range clp.Detections {
		for _, dets := range frameDets {
			if len(dets) > 0 {
				return true
			}
		}
	}
	return false
}

type clipJSON struct {
	SourceData    string                         `json:"source_data"`
	Width         uint                           `json:"width"`
	Height        uint                           `json:"height"`
	Channels      int                            `json:"channels"`
	Type          int                            `json:"gocv_image_type"`
	FrameCount    int                            `json:"frame_count"`
	FPS           float64                        `json:"fps"`
	Timestamps    []uint64                       `json:"timestamps"`
	Guids         []string                       `json:"guids"`
	Detections    []map[string][]frame.Detection `json:"detections"`
	MotionPercent int                            `json:"motion_percent"`
}

// buildClipMetadata renders the clip's stored metadata as the text body of
// the reply post that sits beneath the clip's video event.
func buildClipMetadata(clp *frame.Clip, fps float64) (string, error) {
	guids := make([]string, len(clp.Guids))
	for i, g := range clp.Guids {
		guids[i] = fmt.Sprintf("%x", g)
	}

	meta := clipJSON{
		SourceData:    clp.SourceData,
		Width:         clp.Width,
		Height:        clp.Height,
		Channels:      clp.Channels,
		Type:          int(clp.Types),
		FrameCount:    len(clp.PixelMats),
		FPS:           fps,
		Timestamps:    clp.Timestamps,
		Guids:         guids,
		Detections:    clp.Detections,
		MotionPercent: clp.GetHighestMotion(),
	}

	data, err := json.MarshalIndent(meta, "", "  ")
	if err != nil {
		return "", fmt.Errorf("marshal: %w", err)
	}
	return string(data), nil
}