namespace Oms.Application.Shared;

public class InviteRewardRuleSnapshot
{
    public decimal MinPaidBaseFreight { get; set; } = 50M;

    public decimal FirstOrderRate { get; set; } = 0.05M;

    public decimal FirstOrderCap { get; set; } = 50M;

    public decimal FollowOrderRate { get; set; } = 0.03M;

    public decimal FollowOrderCap { get; set; } = 30M;

    public int FollowWindowDays { get; set; } = 90;

    public int MaxRewardOrders { get; set; } = 6;

    public int SettleBusinessDays { get; set; } = 3;

    public string MinInviteLevelCode { get; set; } = "V1";
}

public class InviteRewardDecision
{
    public bool Eligible { get; set; }

    public int OrderIndex { get; set; }

    public decimal Rate { get; set; }

    public decimal Cap { get; set; }

    public decimal Amount { get; set; }
}

public static class MarketingInviteRewardCalculator
{
    public static InviteRewardDecision Resolve(
        decimal paidBaseFreight,
        int completedOrderIndex,
        DateTime refereeRegisterTime,
        DateTime completeTime,
        InviteRewardRuleSnapshot rule)
    {
        var decision = new InviteRewardDecision { OrderIndex = completedOrderIndex };
        if (completedOrderIndex <= 0 || paidBaseFreight < rule.MinPaidBaseFreight)
        {
            return decision;
        }

        if (completedOrderIndex == 1)
        {
            decision.Eligible = true;
            decision.Rate = rule.FirstOrderRate;
            decision.Cap = rule.FirstOrderCap;
            decision.Amount = Cap(paidBaseFreight * rule.FirstOrderRate, rule.FirstOrderCap);
            return decision;
        }

        if (completedOrderIndex > rule.MaxRewardOrders)
        {
            return decision;
        }

        var windowEnd = refereeRegisterTime.Date.AddDays(rule.FollowWindowDays);
        if (completeTime.Date > windowEnd)
        {
            return decision;
        }

        decision.Eligible = true;
        decision.Rate = rule.FollowOrderRate;
        decision.Cap = rule.FollowOrderCap;
        decision.Amount = Cap(paidBaseFreight * rule.FollowOrderRate, rule.FollowOrderCap);
        return decision;
    }

    public static DateTime AddBusinessDays(DateTime start, int days)
    {
        if (days <= 0)
        {
            return start;
        }

        var cursor = start;
        var added = 0;
        while (added < days)
        {
            cursor = cursor.AddDays(1);
            if (cursor.DayOfWeek is DayOfWeek.Saturday or DayOfWeek.Sunday)
            {
                continue;
            }

            added++;
        }

        return cursor;
    }

    public static int ParseLevelRank(string? levelCode)
    {
        if (string.IsNullOrWhiteSpace(levelCode))
        {
            return 0;
        }

        var code = levelCode.Trim();
        if (code.Length >= 2 && (code[0] == 'V' || code[0] == 'v') && int.TryParse(code[1..], out var n))
        {
            return n;
        }

        return code.ToLowerInvariant() switch
        {
            "normal" => 0,
            "silver" => 2,
            "gold" => 3,
            "diamond" => 4,
            _ => 0
        };
    }

    public static bool CanInvite(string? memberLevelCode, string? minInviteLevelCode)
    {
        return ParseLevelRank(memberLevelCode) >= ParseLevelRank(
            string.IsNullOrWhiteSpace(minInviteLevelCode) ? "V1" : minInviteLevelCode);
    }

    private static decimal Cap(decimal amount, decimal cap)
    {
        var value = Math.Round(Math.Max(0M, amount), 2, MidpointRounding.AwayFromZero);
        if (cap > 0)
        {
            value = Math.Min(value, cap);
        }

        return value;
    }
}