using TakeoutSaaS.Application.Dictionary.Contracts;
using TakeoutSaaS.Application.Dictionary.Models;
using TakeoutSaaS.Domain.Dictionary.Enums;
using TakeoutSaaS.Domain.Dictionary.Repositories;
using TakeoutSaaS.Domain.Dictionary.ValueObjects;
using TakeoutSaaS.Shared.Abstractions.Constants;
using TakeoutSaaS.Shared.Abstractions.Exceptions;
using TakeoutSaaS.Shared.Abstractions.Results;

namespace TakeoutSaaS.Application.Dictionary.Services;

/// <summary>
/// 字典查询服务。
/// </summary>
public sealed class DictionaryQueryService(
    IDictionaryGroupRepository groupRepository,
    IDictionaryItemRepository itemRepository)
{
    /// <summary>
    /// 获取字典分组分页数据。
    /// </summary>
    public async Task<PagedResult<DictionaryGroupDto>> GetGroupsAsync(
        DictionaryGroupQuery query,
        CancellationToken cancellationToken = default)
    {
        // 1. 解析查询租户与作用域
        var tenantId = query.TenantId ?? 0;
        if (query.Scope == DictionaryScope.Business && tenantId <= 0)
        {
            throw new BusinessException(ErrorCodes.ValidationFailed, "Scope=Business 时必须指定 TenantId");
        }

        // 2. 确定作用域与目标租户
        var scope = query.Scope ?? (tenantId == 0 ? DictionaryScope.System : DictionaryScope.Business);
        if (scope == DictionaryScope.System)
        {
            tenantId = 0;
        }

        // 3. 查询分页数据
        var sortDescending = string.Equals(query.SortOrder, "desc", StringComparison.OrdinalIgnoreCase);
        var targetTenant = scope == DictionaryScope.System ? 0 : tenantId;

        var groups = await groupRepository.GetPagedAsync(
            targetTenant,
            scope,
            query.Keyword,
            query.IsEnabled,
            query.Page,
            query.PageSize,
            query.SortBy,
            sortDescending,
            cancellationToken);

        var total = await groupRepository.CountAsync(
            targetTenant,
            scope,
            query.Keyword,
            query.IsEnabled,
            cancellationToken);

        // 4. 转换为 DTO
        var items = new List<DictionaryGroupDto>(groups.Count);
        foreach (var group in groups)
        {
            IReadOnlyList<DictionaryItemDto>? groupItems = null;
            if (query.IncludeItems)
            {
                var groupItemEntities = await itemRepository.GetByGroupIdAsync(group.TenantId, group.Id, cancellationToken);
                groupItems = groupItemEntities
                    .Where(item => item.IsEnabled)
                    .OrderBy(item => item.SortOrder)
                    .Select(DictionaryMapper.ToItemDto)
                    .ToList();
            }

            items.Add(DictionaryMapper.ToGroupDto(group, groupItems));
        }

        return new PagedResult<DictionaryGroupDto>(items, query.Page, query.PageSize, total);
    }

    /// <summary>
    /// 获取字典分组详情。
    /// </summary>
    public async Task<DictionaryGroupDto?> GetGroupByIdAsync(long groupId, CancellationToken cancellationToken = default)
    {
        var group = await groupRepository.GetByIdAsync(groupId, cancellationToken);
        if (group == null)
        {
            return null;
        }

        return DictionaryMapper.ToGroupDto(group);
    }

    /// <summary>
    /// 获取分组下字典项列表。
    /// </summary>
    public async Task<IReadOnlyList<DictionaryItemDto>> GetItemsByGroupIdAsync(long groupId, CancellationToken cancellationToken = default)
    {
        var group = await groupRepository.GetByIdAsync(groupId, cancellationToken);
        if (group == null)
        {
            throw new BusinessException(ErrorCodes.NotFound, "字典分组不存在");
        }

        var items = await itemRepository.GetByGroupIdAsync(group.TenantId, groupId, cancellationToken);
        return items
            .Where(item => item.IsEnabled)
            .OrderBy(item => item.SortOrder)
            .Select(DictionaryMapper.ToItemDto)
            .ToList();
    }

    /// <summary>
    /// 获取合并后的字典项列表。
    /// </summary>
    public async Task<IReadOnlyList<DictionaryItemDto>> GetMergedDictionaryAsync(string code, CancellationToken cancellationToken = default)
    {
        if (!DictionaryCode.IsValid(code))
        {
            throw new BusinessException(ErrorCodes.ValidationFailed, "字典编码格式不正确");
        }

        // 1. 管理端默认读取系统字典（TenantId=0）
        var normalized = new DictionaryCode(code);

        var systemGroup = await groupRepository.GetByCodeAsync(0, normalized, cancellationToken);
        if (systemGroup == null || !systemGroup.IsEnabled)
        {
            return Array.Empty<DictionaryItemDto>();
        }

        var systemItems = await itemRepository.GetByGroupIdAsync(0, systemGroup.Id, cancellationToken);
        return systemItems
            .Where(item => item.IsEnabled)
            .OrderBy(item => item.SortOrder)
            .Select(DictionaryMapper.ToItemDto)
            .ToList();
    }

    /// <summary>
    /// 批量获取字典项。
    /// </summary>
    public async Task<IReadOnlyDictionary<string, IReadOnlyList<DictionaryItemDto>>> BatchGetDictionariesAsync(
        IEnumerable<string> codes,
        CancellationToken cancellationToken = default)
    {
        var normalizedCodes = codes
            .Where(DictionaryCode.IsValid)
            .Select(code => new DictionaryCode(code).Value)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToArray();

        var result = new Dictionary<string, IReadOnlyList<DictionaryItemDto>>(StringComparer.OrdinalIgnoreCase);
        if (normalizedCodes.Length == 0)
        {
            return result;
        }

        var tasks = normalizedCodes.Select(async code =>
        {
            var items = await GetMergedDictionaryAsync(code, cancellationToken);
            return (code, items);
        });

        foreach (var pair in await Task.WhenAll(tasks))
        {
            result[pair.code] = pair.items;
        }

        return result;
    }
}