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

namespace Application.Features.Api.Feed.GetReplies;

public sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var postExists = await db.FeedPost.AsNoTracking().AnyAsync(p => p.ID == request.PostID && !p.IsDeleted, ct);
        if (!postExists)
        {
            return new Response { Total = 0, List = [] };
        }

        var query = db.FeedComment.AsNoTracking().Where(c => c.FeedPostID == request.PostID);

        var total = await query.LongCountAsync(ct);
        var skip = (request.Page - 1) * request.PerPage;

        var rows = await query
            .OrderBy(c => c.CreatedAt)
            .Skip(skip)
            .Take(request.PerPage)
            .Select(c => new
            {
                c.ID,
                c.ParentID,
                ParentAuthorSID = c.Parent != null ? c.Parent.Member.SID : null,
                ParentAuthorName = c.Parent != null ? c.Parent.Member.Name : null,
                c.Content,
                c.IsDeleted,
                c.MemberID,
                AuthorSID = c.Member.SID,
                AuthorName = c.Member.Name,
                AuthorThumb = c.Member.Thumb,
                IsCreator = c.Member.IsCreator,
                c.Likes,
                c.CreatedAt
            })
            .ToListAsync(ct);

        var viewerID = request.ViewerMemberID;
        var commentIDs = rows.Select(r => r.ID).ToList();

        var likedSet = new HashSet<int>();
        if (viewerID is int vid && vid > 0 && commentIDs.Count > 0)
        {
            likedSet = [..await db.FeedCommentLike.AsNoTracking()
                .Where(r => r.MemberID == vid && commentIDs.Contains(r.FeedCommentID))
                .Select(r => r.FeedCommentID)
                .ToListAsync(ct)];
        }

        return new Response
        {
            Total = total,
            List = [..rows.Select(r => new Response.Row
            {
                ID = r.ID,
                ParentID = r.ParentID,
                ParentAuthorSID = r.ParentAuthorSID,
                ParentAuthorName = r.ParentAuthorName,
                Content = r.IsDeleted ? string.Empty : r.Content,
                IsDeleted = r.IsDeleted,
                AuthorSID = r.AuthorSID,
                AuthorName = r.AuthorName,
                AuthorThumb = r.AuthorThumb,
                IsCreator = r.IsCreator,
                Likes = r.Likes,
                HasLike = likedSet.Contains(r.ID),
                IsOwner = viewerID is int v && v > 0 && r.MemberID == v,
                CreatedAt = r.CreatedAt
            })]
        };
    }
}