using Fake.Application;
using Oms.Domain.ChannelsAggregate.Entities;

namespace Oms.Application.Shared;

/// <summary>
/// 计重进位区间校验：同一进位制下左开右闭 (start, end]，端点相接不算重叠，排序后不允许空洞。
/// </summary>
public static class WeightRoundingRangeGuard
{
    public static void EnsureValidRange(decimal startValue, decimal endValue)
    {
        if (startValue >= endValue)
        {
            throw new BusinessException("起始值须小于截止值");
        }
    }

    /// <summary>
    /// (a, b] 与 (c, d] 是否重叠。
    /// </summary>
    public static bool Overlaps(decimal startA, decimal endA, decimal startB, decimal endB) =>
        startA < endB && startB < endA;

    public static void EnsureNoOverlap(
        decimal startValue,
        decimal endValue,
        IEnumerable<WeightRoundingInfo> existing,
        int? excludeId = null)
    {
        EnsureValidRange(startValue, endValue);
        foreach (var item in existing)
        {
            if (excludeId is > 0 && item.Id == excludeId.Value)
            {
                continue;
            }

            if (Overlaps(startValue, endValue, item.StartValue, item.EndValue))
            {
                throw new BusinessException(
                    $"起始区间 ({startValue}, {endValue}] 与已有区间 ({item.StartValue}, {item.EndValue}] 重叠");
            }
        }
    }

    public static void EnsureContiguous(
        decimal startValue,
        decimal endValue,
        IEnumerable<WeightRoundingInfo> existing,
        int? excludeId = null)
    {
        EnsureNoOverlap(startValue, endValue, existing, excludeId);
        var merged = existing
            .Where(item => excludeId is not > 0 || item.Id != excludeId.Value)
            .Select(item => (Start: item.StartValue, End: item.EndValue))
            .Append((Start: startValue, End: endValue))
            .OrderBy(x => x.Start)
            .ThenBy(x => x.End)
            .ToList();

        for (var i = 0; i < merged.Count - 1; i++)
        {
            var currentEnd = merged[i].End;
            var nextStart = merged[i + 1].Start;
            if (currentEnd == nextStart)
            {
                continue;
            }

            throw new BusinessException(
                $"起始区间必须首尾相接（左开右闭）：({merged[i].Start}, {currentEnd}] 与 ({nextStart}, {merged[i + 1].End}] 之间存在缺口");
        }
    }
}