package lidarrrequests

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

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

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrconfig"
)

// Reconciler is a background worker that periodically scans approved
// lidarr_requests and transitions them to completed when their target
// track/album/artist has appeared in the local library (matched by MBID).
// Errors per-row are logged at WARN and do not abort the tick.
type Reconciler struct {
	pool      *pgxpool.Pool
	lidarrCfg *lidarrconfig.Service
	logger    *slog.Logger
	tick      time.Duration
	batch     int32
}

// NewReconciler constructs a Reconciler with production defaults:
// 5-minute tick, batch size 50.
func NewReconciler(pool *pgxpool.Pool, cfg *lidarrconfig.Service, logger *slog.Logger) *Reconciler {
	return &Reconciler{
		pool:      pool,
		lidarrCfg: cfg,
		logger:    logger,
		tick:      5 * time.Minute,
		batch:     50,
	}
}

// Run blocks until ctx is cancelled, ticking every r.tick. Errors from
// tickOnce are logged at WARN and never propagated.
func (r *Reconciler) Run(ctx context.Context) {
	t := time.NewTicker(r.tick)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			if err := r.tickOnce(ctx); err != nil {
				r.logger.Warn("lidarrrequests: reconciler tick failed", "err", err)
			}
		}
	}
}

// tickOnce loads approved requests (oldest first, up to r.batch) and
// transitions any whose target MBID is now present in the local library.
// It is exported-for-tests via the lowercase name (package-internal).
func (r *Reconciler) tickOnce(ctx context.Context) error {
	cfg, err := r.lidarrCfg.Get(ctx)
	if err != nil {
		return err
	}
	if !cfg.Enabled {
		r.logger.Debug("lidarrrequests: reconciler skipping tick — lidarr disabled")
		return nil
	}

	q := dbq.New(r.pool)
	rows, err := q.ListApprovedLidarrRequestsForReconcile(ctx, r.batch)
	if err != nil {
		return err
	}

	for _, row := range rows {
		if err := r.reconcileRow(ctx, q, row); err != nil {
			r.logger.Warn("lidarrrequests: reconciler row failed",
				"request_id", row.ID,
				"kind", row.Kind,
				"err", err,
			)
		}
	}
	return nil
}

// reconcileRow checks the library for a match and, if found, calls
// CompleteLidarrRequest. It returns an error only for unexpected DB
// failures; a no-match is not an error.
func (r *Reconciler) reconcileRow(ctx context.Context, q *dbq.Queries, row dbq.LidarrRequest) error {
	switch row.Kind {
	case dbq.LidarrRequestKindArtist:
		return r.reconcileArtist(ctx, q, row)
	case dbq.LidarrRequestKindAlbum:
		return r.reconcileAlbum(ctx, q, row)
	case dbq.LidarrRequestKindTrack:
		return r.reconcileTrack(ctx, q, row)
	default:
		r.logger.Warn("lidarrrequests: reconciler unknown kind", "kind", row.Kind)
		return nil
	}
}

func (r *Reconciler) reconcileArtist(ctx context.Context, q *dbq.Queries, row dbq.LidarrRequest) error {
	var artistID pgtype.UUID
	err := r.pool.QueryRow(ctx,
		"SELECT id FROM artists WHERE mbid = $1",
		row.LidarrArtistMbid,
	).Scan(&artistID)
	if err != nil {
		if isNoRows(err) {
			return nil // not in library yet
		}
		return err
	}
	_, err = q.CompleteLidarrRequest(ctx, dbq.CompleteLidarrRequestParams{
		ID:              row.ID,
		MatchedArtistID: artistID,
		MatchedAlbumID:  pgtype.UUID{},
		MatchedTrackID:  pgtype.UUID{},
	})
	return err
}

func (r *Reconciler) reconcileAlbum(ctx context.Context, q *dbq.Queries, row dbq.LidarrRequest) error {
	if row.LidarrAlbumMbid == nil {
		return nil
	}
	var albumID pgtype.UUID
	err := r.pool.QueryRow(ctx,
		"SELECT id FROM albums WHERE mbid = $1",
		*row.LidarrAlbumMbid,
	).Scan(&albumID)
	if err != nil {
		if isNoRows(err) {
			return nil
		}
		return err
	}
	_, err = q.CompleteLidarrRequest(ctx, dbq.CompleteLidarrRequestParams{
		ID:              row.ID,
		MatchedAlbumID:  albumID,
		MatchedArtistID: pgtype.UUID{},
		MatchedTrackID:  pgtype.UUID{},
	})
	return err
}

func (r *Reconciler) reconcileTrack(ctx context.Context, q *dbq.Queries, row dbq.LidarrRequest) error {
	if row.LidarrAlbumMbid == nil {
		return nil
	}
	// Track-kind requests match via their parent album's MBID, not track.mbid.
	var albumID pgtype.UUID
	err := r.pool.QueryRow(ctx,
		"SELECT id FROM albums WHERE mbid = $1",
		*row.LidarrAlbumMbid,
	).Scan(&albumID)
	if err != nil {
		if isNoRows(err) {
			return nil
		}
		return err
	}

	// Load any track from that album to set matched_track_id.
	var trackID pgtype.UUID
	err = r.pool.QueryRow(ctx,
		"SELECT id FROM tracks WHERE album_id = $1 ORDER BY id LIMIT 1",
		albumID,
	).Scan(&trackID)
	if err != nil {
		if isNoRows(err) {
			// Album is in the library but no tracks ingested yet — try again next tick.
			return nil
		}
		return err
	}

	_, err = q.CompleteLidarrRequest(ctx, dbq.CompleteLidarrRequestParams{
		ID:              row.ID,
		MatchedAlbumID:  albumID,
		MatchedTrackID:  trackID,
		MatchedArtistID: pgtype.UUID{},
	})
	return err
}

func isNoRows(err error) bool {
	return err == pgx.ErrNoRows
}