package playback

import (
	"context"
	"time"

	"github.com/google/uuid"

	"pipu/api/internal/api/gen"
	"pipu/api/internal/auth"
	"pipu/api/internal/library"
	"pipu/api/internal/platform/sign"
)

type ReactionReader interface {
	Reactions(context.Context, uuid.UUID, []uuid.UUID) (map[uuid.UUID]string, error)
}

// Personalizer decorates catalog DTOs independently of HTTP handlers.
type Personalizer struct {
	store  ReactionReader
	signer *sign.Signer
	now    func() time.Time
}

var _ library.Personalizer = (*Personalizer)(nil)

func NewPersonalizer(store ReactionReader, signer *sign.Signer) *Personalizer {
	return &Personalizer{store: store, signer: signer, now: func() time.Time { return time.Now().UTC() }}
}

// Personalize реализует library.Personalizer.
func (h *Personalizer) Personalize(ctx context.Context, rows []library.TrackRow, out []gen.Track) error {
	p, ok := auth.PrincipalFrom(ctx)
	if !ok {
		return nil
	}
	ids := make([]uuid.UUID, len(rows))
	for i, r := range rows {
		ids[i] = r.ID
	}
	reactions, err := h.store.Reactions(ctx, p.UserID, ids)
	if err != nil {
		return err
	}
	now := h.now()
	for i := range out {
		if out[i].Available {
			u := StreamURL(h.signer, p.UserID, rows[i].ID, now)
			out[i].StreamUrl = &u
		}
		if r, ok := reactions[rows[i].ID]; ok {
			rr := gen.Reaction(r)
			out[i].Reaction = &rr
		}
	}
	return nil
}