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.MarketingAggregate.Consts;
using Oms.Domain.MarketingAggregate.Entities;
using Oms.Domain.MarketingAggregate.Enums;
using Oms.Domain.MarketingAggregate.Repositories;

namespace Oms.Application.Services.Marketing;

/// <summary>
/// 优惠券模板 API（管理端）。
/// </summary>
[ApiExplorerSettings(GroupName = "OMS-Marketing")]
public class MarketingCouponTemplateService : ApplicationService
{
    private ICouponTemplateRepository TemplateRepository =>
        LazyServiceProvider.GetRequiredService<ICouponTemplateRepository>();

    /// <summary>
    /// 分页查询优惠券模板。
    /// </summary>
    [HttpPost("/marketing/coupon-template/list")]
    public async Task<OmsPageResult<CouponTemplateOutput>> GetListAsync(CouponTemplateListInput input)
    {
        var predicate = BuildListPredicate(input);
        var pageIndex = OmsDocHelper.NormalizePage(input.Page);
        var pageSize = OmsDocHelper.NormalizePageSize(input.PageSize);
        var entities = await TemplateRepository.GetPagedListAsync(
            predicate,
            pageIndex,
            pageSize,
            new Dictionary<string, bool>
            {
                [nameof(CouponTemplate.UpdateTime)] = false,
                [nameof(CouponTemplate.Id)] = false
            });
        var total = await TemplateRepository.CountAsync(predicate);
        return new OmsPageResult<CouponTemplateOutput>
        {
            Items = entities.Select(MapOutput).ToList(),
            Total = total
        };
    }

    /// <summary>
    /// 新增优惠券模板（草稿）。
    /// </summary>
    [HttpPost("/marketing/coupon-template/create")]
    public async Task CreateAsync(CouponTemplateSaveInput input)
    {
        await ValidateSaveAsync(input, null);
        var entity = MapToEntity(input, new CouponTemplate
        {
            Status = CouponTemplateStatus.Draft,
            IssuedQuantity = 0
        });
        await TemplateRepository.InsertAsync(entity);
    }

    /// <summary>
    /// 更新优惠券模板。
    /// </summary>
    [HttpPost("/marketing/coupon-template/update")]
    public async Task UpdateAsync(CouponTemplateSaveInput input)
    {
        if (!input.Id.HasValue || input.Id.Value <= 0)
        {
            throw new BusinessException("Template id is invalid");
        }

        var entity = await GetTemplateOrThrowAsync(input.Id.Value);
        if (entity.Status == CouponTemplateStatus.Ended)
        {
            throw new BusinessException("Ended template cannot be edited");
        }

        await ValidateSaveAsync(input, entity.Id);
        MapToEntity(input, entity);
        await TemplateRepository.UpdateAsync(entity);
    }

    /// <summary>
    /// 发布优惠券模板（草稿 → 生效）。
    /// </summary>
    [HttpPost("/marketing/coupon-template/publish")]
    public async Task PublishAsync(IdInput input)
    {
        var entity = await GetTemplateOrThrowAsync(input.Id);
        if (entity.Status != CouponTemplateStatus.Draft)
        {
            throw new BusinessException("Only draft templates can be published");
        }

        entity.Status = CouponTemplateStatus.Active;
        await TemplateRepository.UpdateAsync(entity);
    }

    /// <summary>
    /// 结束优惠券模板（生效 → 已结束）。
    /// </summary>
    [HttpPost("/marketing/coupon-template/end")]
    public async Task EndAsync(IdInput input)
    {
        var entity = await GetTemplateOrThrowAsync(input.Id);
        if (entity.Status != CouponTemplateStatus.Active)
        {
            throw new BusinessException("Only active templates can be ended");
        }

        entity.Status = CouponTemplateStatus.Ended;
        await TemplateRepository.UpdateAsync(entity);
    }

    private static Expression<Func<CouponTemplate, bool>> BuildListPredicate(
        CouponTemplateListInput input)
    {
        var keyword = input.Keyword?.Trim();
        var hasKeyword = !string.IsNullOrWhiteSpace(keyword);
        var status = input.Status;
        var hasStatus = status.HasValue;

        return x =>
            (!hasStatus || x.Status == status!.Value) &&
            (!hasKeyword ||
             x.TemplateCode.Contains(keyword!) ||
             x.TemplateName.Contains(keyword!));
    }

    private async Task ValidateSaveAsync(CouponTemplateSaveInput input, int? excludeId)
    {
        var templateCode = input.TemplateCode.Trim();
        var templateName = input.TemplateName.Trim();
        if (string.IsNullOrWhiteSpace(templateCode))
        {
            throw new BusinessException("Template code is required");
        }

        if (string.IsNullOrWhiteSpace(templateName))
        {
            throw new BusinessException("Template name is required");
        }

        if (string.IsNullOrWhiteSpace(input.CouponType))
        {
            throw new BusinessException("Coupon type is required");
        }

        if (input.PerCustomerLimit <= 0)
        {
            throw new BusinessException("Per customer limit must be positive");
        }

        if (input.TotalQuantity < 0)
        {
            throw new BusinessException("Total quantity cannot be negative");
        }

        if (await TemplateRepository.ExistsTemplateCodeAsync(templateCode, excludeId))
        {
            throw new BusinessException("Template code already exists");
        }

        ValidateCouponTypeFields(input);
    }

    private static void ValidateCouponTypeFields(CouponTemplateSaveInput input)
    {
        switch (input.CouponType)
        {
            case MarketingCouponTypes.FixedOff:
            case MarketingCouponTypes.DirectOff:
            case MarketingCouponTypes.ShippingOff:
                if (!input.FaceValue.HasValue || input.FaceValue.Value <= 0)
                {
                    throw new BusinessException("Face value must be positive");
                }

                break;
            case MarketingCouponTypes.PercentOff:
                if (!input.DiscountRate.HasValue || input.DiscountRate.Value <= 0 || input.DiscountRate.Value >= 1)
                {
                    throw new BusinessException("Discount rate must be between 0 and 1");
                }

                break;
            default:
                throw new BusinessException("Unsupported coupon type");
        }
    }

    private static CouponTemplate MapToEntity(CouponTemplateSaveInput input, CouponTemplate entity)
    {
        entity.TemplateCode = input.TemplateCode.Trim();
        entity.TemplateName = input.TemplateName.Trim();
        entity.CouponType = input.CouponType.Trim();
        entity.FaceValue = input.FaceValue;
        entity.DiscountRate = input.DiscountRate;
        entity.MaxDiscountAmount = input.MaxDiscountAmount;
        entity.MinOrderAmount = input.MinOrderAmount;
        entity.TotalQuantity = input.TotalQuantity;
        entity.PerCustomerLimit = input.PerCustomerLimit;
        entity.ValidType = input.ValidType;
        entity.ValidStartTime = input.ValidStartTime;
        entity.ValidEndTime = input.ValidEndTime;
        entity.ValidDaysAfterReceive = input.ValidDaysAfterReceive;
        entity.ApplyScopeJson = string.IsNullOrWhiteSpace(input.ApplyScopeJson) ? null : input.ApplyScopeJson.Trim();
        entity.GrantChannel = string.IsNullOrWhiteSpace(input.GrantChannel) ? "manual" : input.GrantChannel.Trim();
        entity.Remark = string.IsNullOrWhiteSpace(input.Remark) ? null : input.Remark.Trim();
        return entity;
    }

    private static CouponTemplateOutput MapOutput(CouponTemplate entity) => new()
    {
        Id = entity.Id,
        TemplateCode = entity.TemplateCode,
        TemplateName = entity.TemplateName,
        CouponType = entity.CouponType,
        CouponTypeName = MarketingEnumNames.OfCouponType(entity.CouponType),
        FaceValue = entity.FaceValue,
        DiscountRate = entity.DiscountRate,
        MaxDiscountAmount = entity.MaxDiscountAmount,
        MinOrderAmount = entity.MinOrderAmount,
        TotalQuantity = entity.TotalQuantity,
        IssuedQuantity = entity.IssuedQuantity,
        PerCustomerLimit = entity.PerCustomerLimit,
        ValidType = entity.ValidType,
        ValidStartTime = entity.ValidStartTime,
        ValidEndTime = entity.ValidEndTime,
        ValidDaysAfterReceive = entity.ValidDaysAfterReceive,
        ApplyScopeJson = entity.ApplyScopeJson,
        GrantChannel = entity.GrantChannel,
        Status = entity.Status,
        StatusName = MarketingEnumNames.Of(entity.Status),
        Remark = entity.Remark,
        CreateTime = entity.CreateTime,
        UpdateTime = entity.UpdateTime
    };

    private async Task<CouponTemplate> GetTemplateOrThrowAsync(int id)
    {
        return await TemplateRepository.FirstOrDefaultAsync(x => x.Id == id)
               ?? throw new BusinessException("Coupon template not found");
    }
}