NaviWatcher/internal/musicbrainz/sync.go

package musicbrainz

import (
	"context"
	"fmt"
	"time"

	"naviwatcher/internal/database"
)

// SyncArtistDiscography synchronizes an artist's discography from MusicBrainz
// into the local external_releases table. It follows this flow:
//  1. Check if cached data exists and is within TTL.
//  2. If cache hit, return the cached releases immediately.
//  3. If cache miss or expired, fetch release groups from MusicBrainz API.
//  4. Apply status and type filtering.
//  5. Within a transaction: delete old entries, then upsert each filtered release group.
//  6. Return the list of external releases.
//
// Context cancellation is checked before the API call and between each upsert
// to allow graceful interruption.
func SyncArtistDiscography(
	ctx context.Context,
	client *MusicBrainzClient,
	db *database.DB,
	artistMBID string,
	ttl time.Duration,
) ([]database.ExternalRelease, error) {
	// Check context before starting.
	if err := ctx.Err(); err != nil {
		return nil, fmt.Errorf("sync artist discography: %w", err)
	}

	// Step 1: Check cache.
	cachedReleases, err := GetCachedReleases(db, artistMBID, ttl)
	if err != nil {
		return nil, fmt.Errorf("sync artist discography: cache check failed: %w", err)
	}

	// Step 2: If we have cached data, return it.
	if len(cachedReleases) > 0 {
		if err := ctx.Err(); err != nil {
			return nil, fmt.Errorf("sync artist discography: %w", err)
		}
		return cachedReleases, nil
	}

	// Step 3: Cache miss — fetch from MusicBrainz API.
	groups, err := client.GetArtistReleaseGroups(ctx, artistMBID)
	if err != nil {
		return nil, fmt.Errorf("sync artist discography: fetch release groups for artist %s: %w", artistMBID, err)
	}

	// Step 4: Apply filtering.
	filtered := FilterReleaseGroups(groups)

	// Step 5: Upsert within a transaction — delete old entries first, then insert new ones.
	now := time.Now().UTC()
	tx, err := db.Begin()
	if err != nil {
		return nil, fmt.Errorf("sync artist discography: begin transaction: %w", err)
	}
	defer tx.Rollback()

	// Read existing ignore states before deleting to preserve user-set flags.
	ignoredMap := map[string]bool{}
	rows, err := tx.Query("SELECT rgid, is_ignored FROM external_releases WHERE artist_id = ?", artistMBID)
	if err != nil {
		return nil, fmt.Errorf("sync artist discography: query existing releases: %w", err)
	}
	for rows.Next() {
		var rgid string
		var ignored bool
		if err := rows.Scan(&rgid, &ignored); err != nil {
			rows.Close()
			return nil, fmt.Errorf("sync artist discography: scan existing release: %w", err)
		}
		ignoredMap[rgid] = ignored
	}
	rows.Close()

	// Delete old entries for this artist to avoid stale records.
	if _, err := tx.Exec("DELETE FROM external_releases WHERE artist_id = ?", artistMBID); err != nil {
		return nil, fmt.Errorf("sync artist discography: delete old releases: %w", err)
	}

	var releases []database.ExternalRelease
	for _, rg := range filtered {
		// Check context cancellation between each upsert.
		if err := ctx.Err(); err != nil {
			return nil, fmt.Errorf("sync artist discography: %w", err)
		}

		ext := rg.ToExternalRelease()
		ext.CachedAt = now
		// Preserve user-set ignore flag from previous sync.
		if ignored, ok := ignoredMap[ext.RGID]; ok {
			ext.IsIgnored = ignored
		}

		cachedAtStr := ext.CachedAt.Format("2006-01-02 15:04:05")
		if _, err := tx.Exec(
			"INSERT INTO external_releases (rgid, artist_id, title, type, release_date, is_ignored, cached_at) VALUES (?, ?, ?, ?, ?, ?, ?)",
			ext.RGID, ext.ArtistID, ext.Title, ext.Type, ext.ReleaseDate, ext.IsIgnored, cachedAtStr,
		); err != nil {
			return nil, fmt.Errorf("sync artist discography: insert release %s: %w", rg.ID, err)
		}

		releases = append(releases, *ext)
	}

	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("sync artist discography: commit transaction: %w", err)
	}

	return releases, nil
}