from collections import Counter

from serato_doctor.matching import MatchingEngine
from serato_doctor.models.health import HealthReport
from serato_doctor.models.library import Library


def analyze_health(library: Library) -> HealthReport:
    """Calculate defensible health metrics without changing the library."""

    results = library.reconcile_by_filename()
    missing = [result for result in results if not result.exists_by_filename]
    healthy_count = len(results) - len(missing)
    score = (
        round(healthy_count / len(results) * 100, 1) if results else None
    )

    disk_name_counts = Counter(track.filename for track in library.tracks)
    duplicate_counts = [count for count in disk_name_counts.values() if count > 1]
    referenced_names = {reference.filename for reference in library.references}
    unused_count = sum(
        1 for track in library.tracks if track.filename not in referenced_names
    )

    matcher = MatchingEngine(library.tracks)
    suggested_count = sum(
        bool(matcher.candidates_for(result.reference)) for result in missing
    )

    return HealthReport(
        score=score,
        total_references=len(results),
        healthy_references=healthy_count,
        missing_references=len(missing),
        unique_missing_filenames=len(
            {result.reference.filename for result in missing}
        ),
        disk_tracks=len(library.tracks),
        duplicate_filename_groups=len(duplicate_counts),
        duplicate_files=sum(count - 1 for count in duplicate_counts),
        unused_tracks=unused_count,
        suggested_matches=suggested_count,
    )