using System;
using System.Linq;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using MediatR;
using Knot.Shared.Kernel;
using Knot.Shared.Kernel.Storage;
using Knot.Modules.Identity.Infrastructure.Persistence;
using Knot.Modules.Chats.Infrastructure.Persistence;
using Knot.Modules.Chats.Domain;
using MongoDB.Driver;
using Microsoft.EntityFrameworkCore;
using Host.Models;

namespace Host.Application.Admin.Queries;

public record CleanDryRunQuery(IFileStorageService FileStorage, IdentityDbContext IdentityDb) : IQuery<CleanupDryRunResultDto>;

internal sealed class CleanDryRunQueryHandler : IQueryHandler<CleanDryRunQuery, CleanupDryRunResultDto>
{
    private readonly ChatsDbContext _chatsDbContext;
    private readonly IMongoCollection<Message> _messages;

    public CleanDryRunQueryHandler(ChatsDbContext chatsDbContext, IMongoDatabase mongoDb)
    {
        _chatsDbContext = chatsDbContext;
        _messages = mongoDb.GetCollection<Message>("Messages");
    }

    public async Task<Result<CleanupDryRunResultDto>> Handle(CleanDryRunQuery request, CancellationToken cancellationToken)
    {
        var allChats = await _chatsDbContext.Chats.AsNoTracking().ToListAsync(cancellationToken);
        var activeChatIds = allChats.Select(c => c.Id).ToHashSet();

        var allMessages = await _messages.Find(_ => true).ToListAsync(cancellationToken);

        var orphanedMessages = allMessages
            .Where(m => !activeChatIds.Contains(m.ChatId))
            .ToList();

        var keptMessages = allMessages
            .Where(m => activeChatIds.Contains(m.ChatId))
            .ToList();

        var orphanedMessagesCount = orphanedMessages.Count;

        var allMinioFiles = (await request.FileStorage.ListFilesAsync()).ToList();

        var allUsers = await request.IdentityDb.Users.AsNoTracking().ToListAsync(cancellationToken);

        var validUrls = new HashSet<string>();

        var activeMessageUrls = keptMessages.OfType<MediaMessage>()
            .Where(m => m.Media != null)
            .SelectMany(m => m.Media)
            .Select(me => me.Url)
            .Where(u => !string.IsNullOrEmpty(u));

        var activeChatUrls = allChats
            .Where(c => !string.IsNullOrEmpty(c.Avatar))
            .Select(c => c.Avatar!);

        var activeUserUrls = allUsers
            .Where(u => !string.IsNullOrEmpty(u.Avatar))
            .Select(u => u.Avatar!);

        foreach (var u in activeMessageUrls)
        {
            validUrls.Add(u!);
        }
        foreach (var u in activeChatUrls)
        {
            validUrls.Add(u);
        }
        foreach (var u in activeUserUrls)
        {
            validUrls.Add(u);
        }

        var validFileIds = validUrls
            .Where(u => u.Contains("/api/files/"))
            .Select(u => u.Split('/').Last())
            .ToHashSet();

        long safeBytes = 0;
        foreach (var file in allMinioFiles)
        {
            if (!validFileIds.Contains(file.FileId))
            {
                safeBytes += file.Size;
            }
        }

        return Result.Success(new CleanupDryRunResultDto
        {
            OrphanedMessagesCount = orphanedMessagesCount,
            OrphanedMediaBytes = safeBytes
        });
    }
}