using Microsoft.EntityFrameworkCore;
using MilliSim.Common.Dtos;
using MilliSim.Common.Entities;
using MilliSim.Common.Models;
using MilliSim.Data;
using MilliSim.Services.Infrastructure;

namespace MilliSim.Services;

public class NotificationService : INotificationService
{
    private readonly MilliSimDbContext _db;
    private readonly ICurrentUserService _currentUser;

    public NotificationService(MilliSimDbContext db, ICurrentUserService currentUser)
    {
        _db = db;
        _currentUser = currentUser;
    }

    /// <summary>
    /// 将通知类型枚举转为中文名称
    /// </summary>
    private static string GetTypeName(NotificationType type) => type switch
    {
        NotificationType.System => "系统",
        NotificationType.Project => "项目",
        NotificationType.Account => "账号",
        NotificationType.Authorization => "授权",
        _ => "通知"
    };

    public async Task<ApiResponse<PagedResult<NotificationDto>>> GetNotificationsAsync(NotificationType? type, PageRequest request)
    {
        var userId = _currentUser.UserId;
        var query = _db.Notifications
            .Where(n => n.UserId == null || n.UserId == userId);

        if (type.HasValue)
            query = query.Where(n => n.Type == type.Value);

        if (!string.IsNullOrEmpty(request.Keyword))
            query = query.Where(n => n.Title.Contains(request.Keyword) || n.Content.Contains(request.Keyword));

        var total = await query.CountAsync();
        var items = await query
            .OrderByDescending(n => n.CreatedAt)
            .Skip((request.PageIndex - 1) * request.PageSize)
            .Take(request.PageSize)
            .Select(n => new NotificationDto
            {
                Id = n.Id,
                Type = n.Type,
                Title = n.Title,
                Content = n.Content,
                IsRead = _db.NotificationReads.Any(r => r.NotificationId == n.Id && r.UserId == userId),
                CreatedAt = n.CreatedAt
            })
            .ToListAsync();

        // 在内存中设置中文类型名（避免 EF 翻译 switch 表达式）
        foreach (var item in items)
            item.TypeName = GetTypeName(item.Type);

        return ApiResponse<PagedResult<NotificationDto>>.Success(
            PagedResult<NotificationDto>.Create(items, total, request.PageIndex, request.PageSize));
    }

    public async Task<ApiResponse<int>> GetUnreadCountAsync()
    {
        var userId = _currentUser.UserId;
        var count = await _db.Notifications
            .Where(n => n.UserId == null || n.UserId == userId)
            .Where(n => !_db.NotificationReads.Any(r => r.NotificationId == n.Id && r.UserId == userId))
            .CountAsync();

        return ApiResponse<int>.Success(count);
    }

    public async Task<ApiResponse> MarkAsReadAsync(long id)
    {
        var userId = _currentUser.UserId;
        var notification = await _db.Notifications
            .FirstOrDefaultAsync(n => n.Id == id && (n.UserId == null || n.UserId == userId));
        if (notification == null)
            return ApiResponse.Fail("通知不存在", 404);

        var exists = await _db.NotificationReads
            .AnyAsync(r => r.NotificationId == id && r.UserId == userId);
        if (!exists)
        {
            _db.NotificationReads.Add(new NotificationRead
            {
                UserId = userId,
                NotificationId = id
            });
            await _db.SaveChangesAsync();
        }

        return ApiResponse.Success("已标记为已读");
    }

    public async Task<ApiResponse> MarkAllAsReadAsync()
    {
        var userId = _currentUser.UserId;
        var unreadIds = await _db.Notifications
            .Where(n => n.UserId == null || n.UserId == userId)
            .Where(n => !_db.NotificationReads.Any(r => r.NotificationId == n.Id && r.UserId == userId))
            .Select(n => n.Id)
            .ToListAsync();

        foreach (var nid in unreadIds)
        {
            _db.NotificationReads.Add(new NotificationRead
            {
                UserId = userId,
                NotificationId = nid
            });
        }

        await _db.SaveChangesAsync();
        return ApiResponse.Success($"已将 {unreadIds.Count} 条通知标记为已读");
    }

    public async Task<ApiResponse> DeleteNotificationAsync(long id)
    {
        var userId = _currentUser.UserId;
        var notification = await _db.Notifications
            .FirstOrDefaultAsync(n => n.Id == id && (n.UserId == null || n.UserId == userId));
        if (notification == null)
            return ApiResponse.Fail("通知不存在", 404);

        notification.IsDeleted = true;
        notification.UpdatedAt = DateTime.Now;
        await _db.SaveChangesAsync();

        return ApiResponse.Success("通知已删除");
    }

    public async Task<ApiResponse<NotificationDto>> CreateNotificationAsync(NotificationType type, string title, string content, long? userId = null, string? eventId = null)
    {
        // 根据 eventId 防重复
        if (!string.IsNullOrEmpty(eventId))
        {
            var exists = await _db.Notifications.AnyAsync(n => n.EventId == eventId);
            if (exists)
                return ApiResponse<NotificationDto>.Fail("通知已存在", 409);
        }

        var notification = new Notification
        {
            Type = type,
            Title = title,
            Content = content,
            UserId = userId,
            EventId = eventId
        };
        _db.Notifications.Add(notification);
        await _db.SaveChangesAsync();

        return ApiResponse<NotificationDto>.Success(new NotificationDto
        {
            Id = notification.Id,
            Type = notification.Type,
            TypeName = GetTypeName(notification.Type),
            Title = notification.Title,
            Content = notification.Content,
            IsRead = false,
            CreatedAt = notification.CreatedAt
        });
    }
}