TheriapolisV3/Theriapolis.Godot/UI/BackgroundAvailability.cs

using System.Collections.Generic;

namespace Theriapolis.GodotHost.UI;

/// <summary>
/// Per-background availability rules — which backgrounds are visible /
/// pickable for a given <see cref="CharacterDraft"/>. The
/// backgrounds.json schema doesn't carry restriction fields (gating
/// lives in flavor text), so they're hardcoded here.
///
/// Used by StepBackground to filter the visible card list and by
/// StepClade to clear the currently-selected background when a clade
/// change makes it no longer valid (e.g. picking a non-canid lineage
/// while Pack-Raised is selected).
/// </summary>
public static class BackgroundAvailability
{
    private static readonly Dictionary<string, System.Func<CharacterDraft, bool>> Rules = new()
    {
        // Hybrid-only backgrounds — flavor text explicitly hybrid.
        { "passer",             d => d.IsHybrid },
        { "hybrid_underground", d => d.IsHybrid },
        { "former_chattel",     d => d.IsHybrid },

        // Clade-restricted backgrounds.
        { "warren_runner",      d => d.HasClade("leporidae") },
        { "pack_raised",        d => d.HasClade("canidae") },
        { "herd_city_born",     d => d.HasAnyCladeOfKind("prey") },
    };

    /// <summary>True if the background id can be picked under the given
    /// draft state. Backgrounds not in the rules table are universally
    /// available; the empty id is also "available" (means no
    /// background selected).</summary>
    public static bool IsAvailable(string backgroundId, CharacterDraft draft)
    {
        if (string.IsNullOrEmpty(backgroundId)) return true;
        if (!Rules.TryGetValue(backgroundId, out var rule)) return true;
        return rule(draft);
    }
}