using Oms.Application.Dtos.Channels;
using Oms.Application.Dtos.Orders;
using Oms.Application.Services.Orders.Issues;
using Oms.Domain.ChannelsAggregate.Consts;
using Oms.Domain.ChannelsAggregate.Entities;
using Oms.Domain.OrdersAggregate.Entities;

namespace Oms.Application.Shared;

/// <summary>
/// 排货规则运行时选渠。
/// </summary>
public static class AllocationResolver
{
    public const string SkipStageCondition = "condition";
    public const string SkipStageCustomer = "customer";
    public const string SkipStageChannel = "channel";
    public const string SkipStageBuyPrice = "buyPrice";

    private const int MatchConditionTraceMaxLen = 200;

    public sealed class ChannelCandidate
    {
        public SalesProductAllocationProviderSnapshotDto Provider { get; init; } = null!;

        public ServiceChannel Channel { get; init; } = null!;

        public decimal TotalPayableCost { get; init; }

        /// <summary>候选渠道已算出的应付费用（选渠后可直接落库，避免重复算价）。</summary>
        public IReadOnlyList<OrderFee> PayableFees { get; init; } = [];
    }

    public sealed class FilterProvidersResult
    {
        public List<SalesProductAllocationProviderSnapshotDto> Passed { get; init; } = [];

        public List<OrderAllocationSkippedOutput> Skipped { get; init; } = [];

        public int PoolCount { get; init; }

        public int ConditionPassCount { get; init; }
    }

    /// <summary>
    /// 兼容旧调用：仅按客户名单过滤（无判断条件上下文时）。
    /// </summary>
    public static List<SalesProductAllocationProviderSnapshotDto> FilterProviders(
        IEnumerable<SalesProductAllocationProviderSnapshotDto> providers,
        int? customerId) =>
        FilterProvidersDetailed(providers, customerId, context: null).Passed;

    /// <summary>
    /// 先按判断条件（或兼容客户名单）筛出可用渠道；空条件恒真。
    /// </summary>
    public static FilterProvidersResult FilterProvidersDetailed(
        IEnumerable<SalesProductAllocationProviderSnapshotDto> providers,
        int? customerId,
        OrderRuleEvaluationContext? context)
    {
        var pool = providers
            .Where(x => x.ServiceChannelId.HasValue && x.ServiceChannelId > 0)
            .OrderBy(x => x.SerialNumber)
            .ToList();

        var passed = new List<SalesProductAllocationProviderSnapshotDto>();
        var skipped = new List<OrderAllocationSkippedOutput>();

        foreach (var provider in pool)
        {
            var match = EvaluateProviderMatch(provider, customerId, context);
            if (match.Pass)
            {
                passed.Add(provider);
                continue;
            }

            skipped.Add(new OrderAllocationSkippedOutput
            {
                ServiceChannelId = provider.ServiceChannelId,
                ChannelCode = provider.ChannelCode,
                ChannelName = provider.ServiceChannelName ?? provider.ProviderName,
                Stage = match.Stage,
                MatchCondition = TruncateMatchCondition(provider.MatchCondition),
                Reason = match.Reason
            });
        }

        // 同一渠道多行命中时保留权重更高、序号更小的一行
        var deduped = DeduplicateByChannel(passed);

        return new FilterProvidersResult
        {
            Passed = deduped,
            Skipped = skipped,
            PoolCount = pool.Count,
            ConditionPassCount = passed.Count
        };
    }

    private static List<SalesProductAllocationProviderSnapshotDto> DeduplicateByChannel(
        List<SalesProductAllocationProviderSnapshotDto> passed)
    {
        return passed
            .GroupBy(x => x.ServiceChannelId!.Value)
            .Select(g => g
                .OrderByDescending(x => x.Weight)
                .ThenBy(x => x.SerialNumber)
                .First())
            .OrderBy(x => x.SerialNumber)
            .ToList();
    }

    private readonly record struct MatchOutcome(bool Pass, string Stage, string Reason);

    private static MatchOutcome EvaluateProviderMatch(
        SalesProductAllocationProviderSnapshotDto provider,
        int? customerId,
        OrderRuleEvaluationContext? context)
    {
        var formula = provider.MatchCondition?.Trim();
        if (!string.IsNullOrWhiteSpace(formula)
            && !string.Equals(formula, "无", StringComparison.OrdinalIgnoreCase))
        {
            if (context == null)
            {
                return new MatchOutcome(false, SkipStageCondition, "判断条件缺少订单上下文");
            }

            if (!ChineseFormulaEvaluator.TryEvaluate(formula, context, out var hit))
            {
                return new MatchOutcome(false, SkipStageCondition, "判断条件公式无效");
            }

            if (!hit)
            {
                return new MatchOutcome(false, SkipStageCondition, "判断条件未命中");
            }

            return new MatchOutcome(true, SkipStageCondition, string.Empty);
        }

        // 无公式：兼容旧 CustomerIds 名单
        if (provider.CustomerIds.Count > 0)
        {
            if (customerId.HasValue && provider.CustomerIds.Contains(customerId.Value))
            {
                return new MatchOutcome(true, SkipStageCustomer, string.Empty);
            }

            return new MatchOutcome(false, SkipStageCustomer, "客户不在名单内");
        }

        return new MatchOutcome(true, SkipStageCondition, string.Empty);
    }

    public static string TruncateMatchCondition(string? condition)
    {
        var text = condition?.Trim() ?? string.Empty;
        if (text.Length <= MatchConditionTraceMaxLen)
        {
            return text;
        }

        return text[..MatchConditionTraceMaxLen] + "…";
    }

    public static ServiceChannel SelectChannel(string? scheme, IReadOnlyList<ChannelCandidate> candidates) =>
        SelectCandidate(scheme, candidates).Channel;

    public static ChannelCandidate SelectCandidate(string? scheme, IReadOnlyList<ChannelCandidate> candidates)
    {
        if (candidates.Count == 0)
        {
            throw new InvalidOperationException("无可用排货候选渠道");
        }

        var normalizedScheme = string.IsNullOrWhiteSpace(scheme)
            ? AllocationSchemeCodes.CostLowest
            : scheme.Trim();

        return normalizedScheme switch
        {
            AllocationSchemeCodes.TimeFastest => candidates
                .OrderBy(x => x.Channel.MinTime ?? int.MaxValue)
                .ThenBy(x => x.Provider.SerialNumber)
                .First(),
            AllocationSchemeCodes.OverallBest => candidates
                .OrderByDescending(x => x.Provider.Weight)
                .ThenBy(x => x.Provider.SerialNumber)
                .First(),
            _ => candidates
                .OrderBy(x => x.TotalPayableCost)
                .ThenBy(x => x.Provider.SerialNumber)
                .First()
        };
    }
}