using System.Linq.Expressions;
using Fake.Application;
using Fake.Domain.Exceptions;
using Microsoft.AspNetCore.Mvc;
using Oms.Application.Dtos.Marketing;
using Oms.Application.Dtos.Shared;
using Oms.Application.Shared;
using Oms.Domain.CustomersAggregate.Repositories;
using Oms.Domain.MarketingAggregate.Consts;
using Oms.Domain.MarketingAggregate.Entities;
using Oms.Domain.MarketingAggregate.Enums;
using Oms.Domain.MarketingAggregate.Repositories;

namespace Oms.Application.Services.Marketing;

/// <summary>
/// 优惠券发放与实例查询 API。
/// </summary>
[ApiExplorerSettings(GroupName = "OMS-Marketing")]
public class MarketingCouponGrantService : ApplicationService
{
    private ICouponTemplateRepository TemplateRepository =>
        LazyServiceProvider.GetRequiredService<ICouponTemplateRepository>();

    private ICouponInstanceRepository InstanceRepository =>
        LazyServiceProvider.GetRequiredService<ICouponInstanceRepository>();

    private ICustomerRepository CustomerRepository =>
        LazyServiceProvider.GetRequiredService<ICustomerRepository>();

    private MarketingCouponManager CouponManager =>
        LazyServiceProvider.GetRequiredService<MarketingCouponManager>();

    /// <summary>
    /// 批量发券（子账号编号自动归主客户）。
    /// </summary>
    [HttpPost("/marketing/coupon/grant")]
    public async Task GrantAsync(CouponGrantInput input)
    {
        if (input.CustomerCodes.Count == 0)
        {
            throw new BusinessException("客户编号不能为空");
        }

        var template = await TemplateRepository.FirstOrDefaultAsync(x => x.Id == input.TemplateId)
                       ?? throw new BusinessException("券模板不存在");
        var quantity = Math.Clamp(input.QuantityPerCustomer, 1, 10);
        var grantedMainIds = await ResolveGrantMainCustomerIdsAsync(input.CustomerCodes);
        foreach (var mainCustomerId in grantedMainIds)
        {
            for (var i = 0; i < quantity; i++)
            {
                await CouponManager.GrantAsync(template.Id, mainCustomerId, input.Remark);
            }
        }
    }

    /// <summary>
    /// 批量发券预览（不落库）。
    /// </summary>
    [HttpPost("/marketing/coupon/grant/preview")]
    public async Task<CouponGrantPreviewOutput> PreviewGrantAsync(CouponGrantInput input)
    {
        if (input.CustomerCodes.Count == 0)
        {
            throw new BusinessException("客户编号不能为空");
        }

        var template = await TemplateRepository.FirstOrDefaultAsync(x => x.Id == input.TemplateId)
                       ?? throw new BusinessException("券模板不存在");
        var quantity = Math.Clamp(input.QuantityPerCustomer, 1, 10);
        var grantedMainIds = await ResolveGrantMainCustomerIdsAsync(input.CustomerCodes);
        var customerCount = grantedMainIds.Count;
        var totalCoupons = customerCount * quantity;
        var maxPerCoupon = EstimateTemplateMaxDiscount(template);

        return new CouponGrantPreviewOutput
        {
            CustomerCount = customerCount,
            TotalCoupons = totalCoupons,
            EstimatedMaxDiscount = maxPerCoupon * totalCoupons,
            TemplateName = template.TemplateName
        };
    }

    /// <summary>
    /// 分页查询券实例。
    /// </summary>
    [HttpPost("/marketing/coupon-instance/list")]
    public async Task<OmsPageResult<CouponInstanceOutput>> GetInstanceListAsync(CouponInstanceListInput input)
    {
        var predicate = BuildInstancePredicate(input);
        var pageIndex = OmsDocHelper.NormalizePage(input.Page);
        var pageSize = OmsDocHelper.NormalizePageSize(input.PageSize);
        var entities = await InstanceRepository.GetPagedListAsync(
            predicate,
            pageIndex,
            pageSize,
            new Dictionary<string, bool>
            {
                [nameof(CouponInstance.ReceiveTime)] = false,
                [nameof(CouponInstance.Id)] = false
            });
        var total = await InstanceRepository.CountAsync(predicate);
        return new OmsPageResult<CouponInstanceOutput>
        {
            Items = await MapInstanceOutputsAsync(entities),
            Total = total
        };
    }

    private async Task<HashSet<int>> ResolveGrantMainCustomerIdsAsync(IEnumerable<string> customerCodes)
    {
        var grantedMainIds = new HashSet<int>();
        foreach (var rawCode in customerCodes)
        {
            var code = rawCode?.Trim();
            if (string.IsNullOrWhiteSpace(code))
            {
                continue;
            }

            var customer = await CustomerRepository.GetByCustomerCodeAsync(code)
                           ?? throw new BusinessException($"客户编号 {code} 不存在");
            var mainCustomerId = await CouponManager.ResolveMainCustomerIdAsync(customer.Id);
            grantedMainIds.Add(mainCustomerId);
        }

        return grantedMainIds;
    }

    private static decimal EstimateTemplateMaxDiscount(CouponTemplate template)
    {
        if (string.Equals(template.CouponType, MarketingCouponTypes.FixedOff, StringComparison.OrdinalIgnoreCase)
            || string.Equals(template.CouponType, MarketingCouponTypes.DirectOff, StringComparison.OrdinalIgnoreCase))
        {
            return template.FaceValue ?? 0M;
        }

        return template.MaxDiscountAmount ?? template.FaceValue ?? 0M;
    }

    private static Expression<Func<CouponInstance, bool>> BuildInstancePredicate(CouponInstanceListInput input)
    {
        var keyword = input.Keyword?.Trim();
        var hasKeyword = !string.IsNullOrWhiteSpace(keyword);
        var hasTemplate = input.TemplateId is > 0;
        var templateId = input.TemplateId.GetValueOrDefault();
        var hasCustomer = input.CustomerId is > 0;
        var customerId = input.CustomerId.GetValueOrDefault();
        var status = input.Status;
        var hasStatus = status.HasValue;

        return x =>
            (!hasTemplate || x.TemplateId == templateId) &&
            (!hasCustomer || x.CustomerId == customerId) &&
            (!hasStatus || x.Status == status!.Value) &&
            (!hasKeyword || x.CouponCode.Contains(keyword!));
    }

    private async Task<List<CouponInstanceOutput>> MapInstanceOutputsAsync(List<CouponInstance> entities)
    {
        var templateIds = entities.Select(x => x.TemplateId).Distinct().ToArray();
        var customerIds = entities.Select(x => x.CustomerId).Distinct().ToArray();
        var templates = templateIds.Length == 0
            ? []
            : await TemplateRepository.GetListAsync(x => templateIds.Contains(x.Id));
        var customers = customerIds.Length == 0
            ? []
            : await CustomerRepository.GetListAsync(x => customerIds.Contains(x.Id));
        var templateMap = templates.ToDictionary(x => x.Id);
        var customerMap = customers.ToDictionary(x => x.Id);

        return entities.Select(entity =>
        {
            templateMap.TryGetValue(entity.TemplateId, out var template);
            customerMap.TryGetValue(entity.CustomerId, out var customer);
            return MapInstanceOutput(entity, template, customer?.CustomerCode);
        }).ToList();
    }

    internal static CouponInstanceOutput MapInstanceOutput(
        CouponInstance entity,
        CouponTemplate? template,
        string? customerCode) => new()
    {
        Id = entity.Id,
        TemplateId = entity.TemplateId,
        TemplateName = template?.TemplateName,
        CouponType = template?.CouponType,
        CustomerId = entity.CustomerId,
        CustomerCode = customerCode,
        CouponCode = entity.CouponCode,
        Status = entity.Status,
        StatusName = MarketingEnumNames.Of(entity.Status),
        ReceiveTime = entity.ReceiveTime,
        ValidStartTime = entity.ValidStartTime,
        ValidEndTime = entity.ValidEndTime,
        UseTime = entity.UseTime,
        OrderId = entity.OrderId,
        LockExpireTime = entity.LockExpireTime
    };
}