using System.Linq.Expressions;
using Fake.Application;
using Fake.Domain.Exceptions;
using Microsoft.AspNetCore.Mvc;
using Oms.Application.Dtos.Kb;
using Oms.Application.Dtos.Shared;
using Oms.Application.Shared;
using Oms.Domain.KbAggregate.Entities;
using Oms.Domain.KbAggregate.Repositories;

namespace Oms.Application.Services.Kb;

/// <summary>
/// 知识库分类管理。
/// </summary>
[ApiExplorerSettings(GroupName = "OMS-Kb")]
public class KbCategoryService : ApplicationService
{
    private IKbCategoryRepository CategoryRepository =>
        LazyServiceProvider.GetRequiredService<IKbCategoryRepository>();

    private IKbArticleRepository ArticleRepository =>
        LazyServiceProvider.GetRequiredService<IKbArticleRepository>();

    [HttpGet("/kb/admin/category/list")]
    public async Task<OmsItemsResult<KbCategoryOutput>> AdminListAsync([FromQuery] bool? enabledOnly = null)
    {
        Expression<Func<KbCategory, bool>> predicate = ExpressionPredicate.True<KbCategory>();
        if (enabledOnly is bool enabled)
        {
            predicate = ExpressionPredicate.AndAlso(predicate, x => x.Enabled == enabled);
        }

        var items = await CategoryRepository.GetListAsync(predicate);
        var ordered = items.OrderBy(x => x.SortOrder).ThenBy(x => x.Id).ToList();
        return new OmsItemsResult<KbCategoryOutput>
        {
            Items = ordered.Select(Map).ToList()
        };
    }

    [HttpPost("/kb/admin/category/save")]
    public async Task<KbCategoryOutput> SaveAsync(KbCategorySaveInput input)
    {
        var code = input.Code.Trim();
        var name = input.Name.Trim();
        if (string.IsNullOrWhiteSpace(code) || string.IsNullOrWhiteSpace(name))
        {
            throw new BusinessException("分类编码 / 名称不能为空");
        }

        KbCategory? entity = null;
        if (input.Id is > 0)
        {
            entity = await CategoryRepository.FirstOrDefaultAsync(x => x.Id == input.Id.Value);
            if (entity == null)
            {
                throw new BusinessException("分类不存在");
            }
        }

        if (await CategoryRepository.ExistsCodeAsync(code, entity?.Id))
        {
            throw new BusinessException($"分类编码已存在：{code}");
        }

        entity ??= new KbCategory();
        entity.Code = code;
        entity.Name = name;
        entity.SortOrder = input.SortOrder;
        entity.Enabled = input.Enabled;

        if (entity.Id > 0)
        {
            await CategoryRepository.UpdateAsync(entity);
        }
        else
        {
            await CategoryRepository.InsertAsync(entity);
        }

        return Map(entity);
    }

    [HttpPost("/kb/admin/category/delete")]
    public async Task DeleteAsync(KbCategoryDeleteInput input)
    {
        var entity = await CategoryRepository.FirstOrDefaultAsync(x => x.Id == input.Id);
        if (entity == null)
        {
            throw new BusinessException("分类不存在");
        }

        var articleCount = await ArticleRepository.CountByCategoryIdAsync(entity.Id);
        if (articleCount > 0)
        {
            throw new BusinessException($"该分类下仍有 {articleCount} 篇文章，无法删除");
        }

        await CategoryRepository.DeleteAsync(entity);
    }

    private static KbCategoryOutput Map(KbCategory x) => new()
    {
        Id = x.Id,
        Code = x.Code,
        Name = x.Name,
        SortOrder = x.SortOrder,
        Enabled = x.Enabled
    };
}