// Package similarity owns the inbound ListenBrainz similarity ingest
// pipeline. A periodic worker queries LB's /explore/similar-recordings
// and /explore/similar-artists endpoints for tracks the user has played,
// filters returned MBIDs to the local library, and stores the top-K
// edges in track_similarity / artist_similarity for M4c's radio
// candidate-pool builder.
package similarity

import (
	"context"
	"log/slog"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/scrobble/listenbrainz"
)

// Worker drains played-tracks-and-artists needing similarity and POSTs
// the results into track_similarity / artist_similarity. Failures are
// passively retried via the timer (no durable queue table — losing one
// tick's worth of refresh attempts is "1 hour of staleness," fine).
type Worker struct {
	pool   *pgxpool.Pool
	client *listenbrainz.Client
	logger *slog.Logger
	tick   time.Duration
	batch  int32
	topK   int
}

// NewWorker constructs a worker with production defaults: 1h tick,
// batch=5, topK=20.
func NewWorker(pool *pgxpool.Pool, client *listenbrainz.Client, logger *slog.Logger) *Worker {
	return &Worker{
		pool:   pool,
		client: client,
		logger: logger,
		tick:   1 * time.Hour,
		batch:  5,
		topK:   20,
	}
}

// Run blocks until ctx is cancelled, ticking every w.tick.
func (w *Worker) Run(ctx context.Context) {
	t := time.NewTicker(w.tick)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			if err := w.tickOnce(ctx); err != nil {
				w.logger.Error("similarity: tick failed", "err", err)
			}
		}
	}
}

// tickOnce drains one batch of tracks and one batch of artists. Stub —
// implementation lands in Task 6 along with the integration tests that
// drive it.
func (w *Worker) tickOnce(_ context.Context) error {
	return nil
}