using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Api.V1.Members.List;

internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var page = Math.Max(1, request.Page);
        var size = Math.Clamp(request.Size, 1, 200);

        var baseQuery = db.Member
            .AsNoTracking()
            .Where(c => !c.IsWithdraw && c.DeletedAt == null);

        // hasChannel 필터: true → 채널 보유, false → 채널 미보유, null → 전체
        if (request.HasChannel == true)
        {
            baseQuery = baseQuery.Where(c => c.Channel != null);
        }
        else if (request.HasChannel == false)
        {
            baseQuery = baseQuery.Where(c => c.Channel == null);
        }

        var total = await baseQuery.CountAsync(ct);

        var rows = await baseQuery
            .OrderByDescending(c => c.ID)
            .Skip((page - 1) * size)
            .Take(size)
            .Select(c => new
            {
                c.ID,
                c.SID,
                c.Name,
                c.Email,
                c.CreatedAt,
                ChannelSID = c.Channel != null ? c.Channel.SID : null,
                ChannelName = c.Channel != null ? c.Channel.Name : null
            })
            .ToListAsync(ct);

        var items = rows.Select(r => new Response.Row(
            r.ID,
            r.SID,
            r.Name,
            MaskEmail(r.Email),
            r.ChannelSID != null,
            r.ChannelSID,
            r.ChannelName,
            r.CreatedAt
        )).ToList();

        return new Response(total, page, size, items);
    }

    private static string MaskEmail(string email)
    {
        if (string.IsNullOrWhiteSpace(email))
        {
            return string.Empty;
        }

        var atIndex = email.IndexOf('@');
        if (atIndex <= 0)
        {
            return "***";
        }

        var local = email[..atIndex];
        var domain = email[(atIndex + 1)..];
        var prefix = local.Length <= 2 ? local[..1] : local[..2];

        return $"{prefix}***@{domain}";
    }
}