DCGO/Assets/Scripts/CardEffectCommons/MinMax_DP_Cost_Level/Cost/IsMinCost.cs

using System.Collections;
using System.Collections.Generic;
using System;
using System.Linq;
using UnityEngine;
using System.Security;

public partial class CardEffectCommons
{
    public static bool IsMinCost(Permanent permanent, Player owner, bool IsDigimonOnly)
    {
        if (permanent == null) return false;
        if (permanent.TopCard == null) return false;
        if (permanent.TopCard.Owner != owner) return false;
        if (!IsPermanentExistsOnOwnerBattleArea(permanent, permanent.TopCard)) return false;
        if (!permanent.IsDigimon && !permanent.IsTamer) return false;
        if (!permanent.TopCard.HasPlayCost) return false;

        List<int> costs = permanent.TopCard.Owner.GetBattleAreaPermanents().Filter(permanent1 =>
            (permanent1.IsDigimon || permanent1.IsTamer)
            && (IsDigimonOnly && permanent1.IsDigimon)
            && permanent1.TopCard.HasPlayCost)
            .Map(permanent1 => permanent1.TopCard.GetCostItself);

        return costs.Count >= 1 && permanent.TopCard.GetCostItself == costs.Min();
    }
}