"""Compress Spotify taste signals for prompts and known-track filtering."""

from app.domain.models import CompressedTasteProfile, TasteProfile, Track


def compress_taste_profile(profile: TasteProfile) -> CompressedTasteProfile:
    """Build compact prompt text and the complete known track identifier set."""
    # No genre section on purpose: Spotify deprecated the artist genres
    # field for new apps, so there is no reliable genre source left in the
    # API. Artist and track names are the genre evidence the model reads.
    sections = (
        _line("Short-term top artists", profile.short_term_artists),
        _line("Long-term top artists", profile.long_term_artists),
        _line("Short-term top tracks", _track_labels(profile.short_term_tracks)),
        _line("Long-term top tracks", _track_labels(profile.long_term_tracks)),
        _line("Saved-track sample", _track_labels(profile.saved_tracks)),
    )
    known_tracks = (*profile.short_term_tracks, *profile.long_term_tracks, *profile.saved_tracks)
    return CompressedTasteProfile(
        text="\n".join(sections),
        known_track_ids=frozenset(track.id for track in known_tracks),
    )


def _track_labels(tracks: tuple[Track, ...]) -> tuple[str, ...]:
    return tuple(f"{track.title} by {', '.join(track.artists)}" for track in tracks)


def _line(label: str, values: tuple[str, ...]) -> str:
    rendered_values = "; ".join(values) if values else "none"
    return f"{label}: {rendered_values}"
