package playback

import (
	"context"
	"time"

	"github.com/google/uuid"

	"pipu/api/internal/api/gen"
	"pipu/api/internal/auth"
)

// EventService owns event acceptance and its transaction; HTTP only authenticates and maps DTOs.
type EventService struct {
	store *Store
	now   func() time.Time
}

func (s EventService) Accept(ctx context.Context, p auth.Principal, events []gen.PlayEvent) (gen.PostEvents200JSONResponse, error) {
	now := s.now()
	ids := make([]uuid.UUID, 0, len(events))
	for _, e := range events {
		ids = append(ids, e.TrackId)
	}
	durations, err := s.store.TrackDurations(ctx, ids)
	if err != nil {
		return gen.PostEvents200JSONResponse{}, err
	}
	clientType := s.store.SessionClientType(ctx, p.SessionID)

	out := gen.PostEvents200JSONResponse{}
	tx, err := s.store.Begin(ctx)
	if err != nil {
		return gen.PostEvents200JSONResponse{}, err
	}
	defer func() { _ = tx.Rollback(ctx) }()
	for _, e := range events {
		dur, known := durations[e.TrackId]
		at := e.OccurredAt.UTC()
		if !known || at.Before(now.Add(-maxEventAge)) {
			out.Rejected++
			continue
		}
		if at.After(now.Add(maxEventClockSkew)) {
			at = now // часы клиента спешат
		}
		ev := Event{
			ID: e.Id, Type: string(e.Type), TrackID: e.TrackId, OccurredAt: at, PositionMs: e.PositionMs,
			PlayedMs: e.PlayedMs, ContextID: e.ContextId, WaveSessionID: e.WaveSessionId,
			Offline: e.Offline != nil && *e.Offline,
		}
		if e.ContextType != nil {
			ct := string(*e.ContextType)
			ev.ContextType = &ct
		}
		inserted, err := s.store.InsertEvent(ctx, tx, p.UserID, clientType, ev)
		if err != nil {
			return gen.PostEvents200JSONResponse{}, err
		}
		if !inserted {
			out.Duplicates++
			continue
		}
		out.Accepted++
		played := 0
		if e.PlayedMs != nil {
			played = *e.PlayedMs
		}
		o := Judge(ev.Type, played, dur)
		if o != (Outcome{}) {
			if err := s.store.ApplyOutcome(ctx, tx, p.UserID, ev, o); err != nil {
				return gen.PostEvents200JSONResponse{}, err
			}
		}
		if outcome := impressionOutcome(ev.Type, o); outcome != "" && ev.ContextType != nil && *ev.ContextType == "wave" &&
			ev.ContextID != nil {
			if sid, err := uuid.Parse(*ev.ContextID); err == nil {
				if err := s.store.MarkImpression(ctx, tx, sid, ev.TrackID, outcome); err != nil {
					return gen.PostEvents200JSONResponse{}, err
				}
			}
		}
	}
	if err := tx.Commit(ctx); err != nil {
		return gen.PostEvents200JSONResponse{}, err
	}
	return out, nil
}