using System.Data.Common;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using StopShopping.EF;
using StopShopping.Services.Models;
using StopShopping.Services.Models.Req;
using StopShopping.Services.Models.Resp;

namespace StopShopping.Services.Implementions;

public class CategoryService : ICategoryService
{
    public CategoryService(
        IFileService fileService,
        StopShoppingContext dbContext,
        ILogger<CategoryService> logger
    )
    {
        _fileService = fileService;
        _dbContext = dbContext;
        _logger = logger;
    }

    private readonly IFileService _fileService;
    private readonly StopShoppingContext _dbContext;
    private readonly ILogger<CategoryService> _logger;

    public async Task<ApiResponse> DeleteCategoryAsync(CategoryIdParams model)
    {
        var category = await _dbContext.Categories
            .AsNoTracking()
            .FirstOrDefaultAsync(c => c.Id == model.CategoryId && !c.Deleted);
        if (null == category)
            return ApiResponse.Failed("此分类已不存在，请刷新重试");

        var anyProduct = await _dbContext.Products
            .AsNoTracking()
            .AnyAsync(p =>
                _dbContext.Categories
                    .AsNoTracking()
                    .Where(c => c.Path.StartsWith(category.Path) && !c.Deleted)
                    .Select(c => c.Id)
                    .Contains(p.CategoryId));
        if (anyProduct)
            return ApiResponse.Failed("分类下已有商品，不允许删除");

        await _dbContext.Categories
            .Where(c => c.Path.StartsWith(category.Path) && !c.Deleted)
            .ExecuteDeleteAsync();

        return ApiResponse.Succed();
    }

    public async Task<ApiResponse<Category>> EditCategoryAsync(EditCategoryParams model)
    {
        EF.Models.Category category;

        using var trans = await _dbContext.Database.BeginTransactionAsync();
        try
        {
            short level = 1, order = 1;
            string path = string.Empty;

            var parent = await _dbContext.Categories
                .FirstOrDefaultAsync(c => c.Id == model.ParentId);
            if (null != parent)
                level = (short)(parent.Level + 1);

            if (model.Id > 0)
            {
                category = await _dbContext.Categories
                    .FirstAsync(c => c.Id == model.Id && !c.Deleted);
                if (null == category)
                    return new ApiResponse<Category>().Failed("此分类已不存在");

                path = category.Path;
                order = category.Order;
            }
            else
            {
                category = new EF.Models.Category();
                await _dbContext.Categories.AddAsync(category);

                order = await _dbContext.Categories
                    .Where(c => c.ParentId == model.ParentId)
                    .Select(c => c.Order)
                    .DefaultIfEmpty()
                    .MaxAsync();
            }

            category.Level = level;
            if (!string.IsNullOrWhiteSpace(model.Logo))
                category.Logo = model.Logo;
            category.Name = model.Name;
            category.Order = order;
            category.ParentId = model.ParentId;
            category.Path = path;

            await _dbContext.SaveChangesAsync();

            if (!(model.Id > 0))
            {
                category.Path = BuildPath(parent?.Path ?? "", category.Id);
                await _dbContext.SaveChangesAsync();
            }

            await trans.CommitAsync();

            var categoryResult = Cast(category);

            return new ApiResponse<Category>(categoryResult);
        }
        catch (DbException e)
        {
            await trans.RollbackAsync();
            _logger.LogError(e, "新增/修改分类失败");
            return new ApiResponse<Category>().Failed("数据库操作失败，请刷新重试");
        }
    }

    public ApiResponse<List<Category>> GetCategoriesTree()
    {
        var qry = _dbContext.Categories
            .AsNoTracking()
            .Where(c => !c.Deleted)
            .OrderBy(c => c.ParentId)
            .ThenBy(c => c.Order)
            .AsEnumerable();

        var result = new ApiResponse<List<Category>>(ToTree(qry));

        return result;
    }

    public async Task<ApiResponse> ResortCategoryAsync(ResortCategoryParams model)
    {
        var curr = await _dbContext.Categories
            .FirstOrDefaultAsync(c => c.Id == model.Id && !c.Deleted);
        if (null == curr)
            return ApiResponse.Failed("此分类已不存在，请刷新重试");

        var target = await _dbContext.Categories
            .FirstOrDefaultAsync(c => c.Order == model.TargetOrder && !c.Deleted);
        if (null == target)
            return ApiResponse.Failed("目标位置分类已不存在，请刷新重试");

        target.Order = curr.Order;
        curr.Order = model.TargetOrder;

        await _dbContext.SaveChangesAsync();

        return ApiResponse.Succed();
    }

    #region private methods

    private List<Category> ToTree(IEnumerable<EF.Models.Category> models)
    {
        Dictionary<int, Category> idDicts = [];
        List<Category> categories = [];

        foreach (var model in models)
        {
            Category node = Cast(model);
            node.Children = [];
            idDicts.Add(node.Id, node);
        }

        foreach (var d in idDicts)
        {
            if (d.Value.ParentId > 0)
                idDicts[d.Value.ParentId].Children.Add(d.Value);
            else
                categories.Add(d.Value);
        }

        return categories;
    }

    private Category Cast(EF.Models.Category model)
    {
        return new()
        {
            Id = model.Id,
            LogoUrl = string.IsNullOrWhiteSpace(model.Logo)
                ? ""
                : _fileService.GetFileUrl(UploadScences.Category, model.Logo),
            Name = model.Name,
            Order = model.Order,
            ParentId = model.ParentId,
            Children = []
        };
    }

    private string BuildPath(string prefix, params int[] ids)
    {
        return string.Format("{0}/{1}/",
            prefix.TrimEnd('/')
            , string.Join('/', ids));
    }

    #endregion
}