namespace Theriapolis.Core.Persistence.SaveMigrations;

/// <summary>
/// Phase 6.5 M0 — additive migration from save schema v6 (Phase 6 ship) to
/// v7 (Phase 6.5 levelling). Non-destructive: every v6 field carries over
/// unchanged. The new <see cref="PlayerCharacterState.SubclassId"/>,
/// <see cref="PlayerCharacterState.LearnedFeatureIds"/>, and
/// <see cref="PlayerCharacterState.LevelUpHistory"/> default-initialise
/// to empty values by the constructor, so this migration just bumps the
/// header version.
///
/// Phase-6 saves had no level-up history (every character stayed at level
/// 1, Xp = 0). On load they continue to be valid level-1 characters; the
/// player can immediately start earning XP and levelling up under the new
/// rules.
/// </summary>
public sealed class V6ToV7Migration : ISaveMigration
{
    public int FromVersion => 6;
    public int ToVersion   => 7;

    public void Apply(SaveHeader header, SaveBody body)
    {
        // No data translation needed. PlayerCharacterState's new fields
        // (SubclassId, LearnedFeatureIds, LevelUpHistory) default-initialise
        // to empty in their record, and SaveCodec.ReadCharacter handles
        // missing-section bytes via the EOS-check pattern Phase 5 already
        // established. Pure version bump.
    }
}