package scanner

import (
	"context"
	"log"

	"naviwatcher/internal/database"
)

// ScanArtist loads the local albums and external releases for a single artist
// from the database and computes the list of missing releases.
//
// threshold is the fuzzy-similarity cutoff; pass 0 to use DefaultThreshold.
// The context is checked before querying the database; if it is already
// cancelled, no work is performed and the sentinel error ctx.Err() is returned.
func ScanArtist(ctx context.Context, db *database.DB, artistID string, threshold float64) ([]MissingRelease, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}

	local, err := database.GetLocalAlbumsByArtist(db, artistID)
	if err != nil {
		return nil, err
	}

	external, err := database.GetExternalReleasesByArtist(db, artistID)
	if err != nil {
		return nil, err
	}

	missing := FindMissingReleases(local, external, threshold)
	return missing, nil
}

// ScanAll iterates over all monitored artists (those with Monitored == true)
// and computes the missing releases for each. Results are concatenated into a
// single slice across all artists.
//
// ctx.Err() is checked between artists; if cancellation occurs mid-iteration,
// scanning stops early and the accumulated results so far are returned along
// with the cancellation error. threshold follows the same contract as
// ScanArtist (0 → DefaultThreshold).
func ScanAll(ctx context.Context, db *database.DB, threshold float64) ([]MissingRelease, error) {
	settings, err := database.GetAllArtistSettings(db)
	if err != nil {
		return nil, err
	}

	var all []MissingRelease
	for _, s := range settings {
		if err := ctx.Err(); err != nil {
			return all, err
		}
		if !s.Monitored {
			continue
		}
		// A transient error for one artist must not abort the whole scan and
		// take down the daemon; log it and continue with the remaining artists.
		missing, err := ScanArtist(ctx, db, s.ID, threshold)
		if err != nil {
			log.Printf("scan artist %s failed: %v", s.ID, err)
			continue
		}
		all = append(all, missing...)
	}

	return all, nil
}