using AutoMapper;
using MediatR;
using Microsoft.Extensions.DependencyInjection;
using DigitalData.Core.Abstraction.Application.Repository;
using DigitalData.Core.Exceptions;
using EnvelopeGenerator.Domain.Entities;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Application.Common.Interfaces.SQLExecutor;
using EnvelopeGenerator.Application.Histories.Commands;
using EnvelopeGenerator.Domain.Constants;
using EnvelopeGenerator.Domain;
using Microsoft.EntityFrameworkCore;

namespace EnvelopeGenerator.Application.Envelopes.Commands;

/// <summary>
/// 
/// </summary>
public class CreateEnvelopeCommandHandler : IRequestHandler<CreateEnvelopeCommand, EnvelopeDto?>
{
    private readonly IServiceProvider _provider;

    private IEnvelopeExecutor Executor => _provider.GetRequiredService<IEnvelopeExecutor>();

    private IRepository<Envelope> Repository => _provider.GetRequiredService<IRepository<Envelope>>();

    private IRepository<Document> DocumentRepository => _provider.GetRequiredService<IRepository<Document>>();

    private IRepository<EnvelopeReceiver> EnvelopeReceiverRepository => _provider.GetRequiredService<IRepository<EnvelopeReceiver>>();

    private IRepository<Receiver> ReceiverRepository => _provider.GetRequiredService<IRepository<Receiver>>();

    private IRepository<DocReceiverElement> DocReceiverElementRepository => _provider.GetRequiredService<IRepository<DocReceiverElement>>();

    private IMediator Mediator => _provider.GetRequiredService<IMediator>();

    private readonly IMapper _mapper;

    /// <summary>
    /// 
    /// </summary>
    /// <param name="provider"></param>
    /// <param name="mapper"></param>
    public CreateEnvelopeCommandHandler(IServiceProvider provider, IMapper mapper)
    {
        _provider = provider;
        _mapper = mapper;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancel"></param>
    /// <returns></returns>
    public async Task<EnvelopeDto?> Handle(CreateEnvelopeCommand request, CancellationToken cancel)
    {
        var now = DateTime.Now;
        var title = request.Title?.Trim() ?? string.Empty;
        var message = request.Message?.Trim() ?? string.Empty;

        Envelope envelope;
        if (request.EnvelopeId is int envelopeId)
        {
            envelope = await Repository.Query
                .Include(e => e.User)
                .FirstOrDefaultAsync(e => e.Id == envelopeId, cancel)
                ?? throw new BadRequestException($"Envelope {envelopeId} not found.");

            if (envelope.UserId != request.UserId)
                throw new ForbiddenException();

            await Repository.UpdateAsync(e =>
            {
                e.Title = title;
                e.Message = message;
                e.TfaEnabled = request.TFAEnabled;
                e.Status = EnvelopeStatus.EnvelopeSaved;
                e.ChangedWhen = now;
            }, e => e.Id == envelopeId, cancel);

            envelope.Title = title;
            envelope.Message = message;
            envelope.TfaEnabled = request.TFAEnabled;
            envelope.Status = EnvelopeStatus.EnvelopeSaved;
            envelope.ChangedWhen = now;
        }
        else
        {
            envelope = request.UseSQLExecutor
                ? await Executor.CreateEnvelopeAsync(request.UserId, title, message, request.TFAEnabled, cancel)
                : await Repository.CreateAsync(new Envelope
                {
                    UserId = request.UserId,
                    Status = EnvelopeStatus.EnvelopeCreated,
                    Uuid = Guid.NewGuid().ToString(),
                    Title = title,
                    Message = message,
                    AddedWhen = now,
                    ChangedWhen = now,
                    Comment = string.Empty,
                    Language = "de-DE",
                    TfaEnabled = request.TFAEnabled,
                    UseAccessCode = false,
                    SendReminderEmails = false
                }, cancel);

            await Mediator.Send(new CreateHistoryCommand
            {
                EnvelopeId = envelope.Id,
                UserReference = await ResolveSenderReferenceAsync(envelope, cancel),
                Status = EnvelopeStatus.EnvelopeCreated
            }, cancel);
        }

        await UpsertDocumentAsync(envelope.Id, request.Document, now, cancel);
        await UpsertReceiversAndFieldsAsync(envelope.Id, request.Receivers, now, cancel);

        if (request.Send)
            await SendEnvelopeAsync(envelope, cancel);

        envelope = await Repository.Query
            .Include(e => e.User)
            .Include(e => e.EnvelopeReceivers)
                .ThenInclude(er => er.Receiver)
            .FirstAsync(e => e.Id == envelope.Id, cancel);

        return _mapper.Map<EnvelopeDto>(envelope);
    }

    private async Task<string> ResolveSenderReferenceAsync(Envelope envelope, CancellationToken cancel)
    {
        if (!string.IsNullOrWhiteSpace(envelope.User?.Email))
            return envelope.User.Email;

        var senderEmail = await Repository.Query
            .Where(e => e.Id == envelope.Id)
            .Select(e => e.User.Email)
            .FirstOrDefaultAsync(cancel);

        if (string.IsNullOrWhiteSpace(senderEmail))
            throw new BadRequestException("Envelope sender email is missing.");

        return senderEmail;
    }

    private async Task UpsertDocumentAsync(int envelopeId, CreateEnvelopeDocumentDto? document, DateTime now, CancellationToken cancel)
    {
        if (document is null || string.IsNullOrWhiteSpace(document.DataAsBase64))
            return;

        byte[] bytes;
        try
        {
            bytes = Convert.FromBase64String(document.DataAsBase64);
        }
        catch (FormatException)
        {
            throw new BadRequestException("Document payload is not valid base64.");
        }

        var existingDocumentId = await DocumentRepository.Query
            .Where(d => d.EnvelopeId == envelopeId)
            .Select(d => (int?)d.Id)
            .FirstOrDefaultAsync(cancel);

        if (existingDocumentId is null)
        {
            await DocumentRepository.CreateAsync(new Document
            {
                EnvelopeId = envelopeId,
                AddedWhen = now,
                ByteData = bytes,
                Filename = string.Empty,
                Filepath = string.Empty,
                FileNameOriginal = string.Empty
            }, cancel);

            return;
        }

        await DocumentRepository.UpdateAsync(d =>
        {
            d.ByteData = bytes;
        }, d => d.Id == existingDocumentId.Value, cancel);
    }

    private async Task UpsertReceiversAndFieldsAsync(int envelopeId, IReadOnlyCollection<CreateEnvelopeReceiverDto> receivers, DateTime now, CancellationToken cancel)
    {
        var filteredReceivers = receivers
            .Where(r => !string.IsNullOrWhiteSpace(r.EmailAddress))
            .Select(r => r with
            {
                EmailAddress = r.EmailAddress.Trim().ToLowerInvariant(),
                Name = r.Name?.Trim(),
                PhoneNumber = string.IsNullOrWhiteSpace(r.PhoneNumber) ? null : r.PhoneNumber.Trim(),
                Fields = r.Fields ?? new List<CreateEnvelopeFieldDto>()
            })
            .GroupBy(r => r.EmailAddress, StringComparer.OrdinalIgnoreCase)
            .Select(g => g.First())
            .ToList();

        if (filteredReceivers.Count == 0)
            return;

        var document = await DocumentRepository.Query
            .FirstOrDefaultAsync(d => d.EnvelopeId == envelopeId, cancel);

        if (document is null)
            return;

        var currentLinks = await EnvelopeReceiverRepository.Query
            .Include(er => er.Receiver)
            .Where(er => er.EnvelopeId == envelopeId)
            .ToListAsync(cancel);

        var linksByEmail = currentLinks
            .Where(er => !string.IsNullOrWhiteSpace(er.Receiver?.EmailAddress))
            .GroupBy(er => er.Receiver!.EmailAddress, StringComparer.OrdinalIgnoreCase)
            .ToDictionary(g => g.Key.ToLowerInvariant(), g => g.First(), StringComparer.OrdinalIgnoreCase);

        var sequence = currentLinks.Count > 0 ? currentLinks.Max(er => er.Sequence) : 0;

        foreach (var receiverDraft in filteredReceivers)
        {
            var linkResult = await GetOrCreateEnvelopeReceiverAsync(envelopeId, receiverDraft, linksByEmail, now, sequence, cancel);
            var link = linkResult.Link;
            sequence = linkResult.NextSequence;

            await DocReceiverElementRepository.DeleteAsync(query => query
                .Where(e => e.DocumentId == document.Id)
                .Where(e => e.ReceiverId == link.ReceiverId), cancel);

            foreach (var field in receiverDraft.Fields.Where(f => f.Page > 0))
            {
                await DocReceiverElementRepository.CreateAsync(new DocReceiverElement
                {
                    DocumentId = document.Id,
                    ReceiverId = link.ReceiverId,
                    ElementType = 1,
                    X = field.X,
                    Y = field.Y,
                    Width = 1.77,
                    Height = 1.96,
                    Page = field.Page,
                    Required = true,
                    ReadOnly = false,
                    AnnotationIndex = 0,
                    AddedWhen = now,
                    FullName = link.Name,
                    Position = string.Empty,
                    Place = string.Empty,
                    Tooltip = string.Empty
                }, cancel);
            }
        }
    }

    private async Task<(EnvelopeReceiver Link, int NextSequence)> GetOrCreateEnvelopeReceiverAsync(
        int envelopeId,
        CreateEnvelopeReceiverDto receiverDraft,
        IDictionary<string, EnvelopeReceiver> linksByEmail,
        DateTime now,
        int sequence,
        CancellationToken cancel)
    {
        if (linksByEmail.TryGetValue(receiverDraft.EmailAddress, out var existingLink))
        {
            var nextName = string.IsNullOrWhiteSpace(receiverDraft.Name) ? existingLink.Name : receiverDraft.Name!;
            var nextPhoneNumber = receiverDraft.PhoneNumber ?? existingLink.PhoneNumber;

            await EnvelopeReceiverRepository.UpdateAsync(er =>
            {
                er.Name = nextName;
                er.PhoneNumber = nextPhoneNumber;
                er.ChangedWhen = now;
            }, er => er.EnvelopeId == existingLink.EnvelopeId && er.ReceiverId == existingLink.ReceiverId, cancel);

            existingLink.Name = nextName;
            existingLink.PhoneNumber = nextPhoneNumber;
            return (existingLink, sequence);
        }

        var receiver = await ReceiverRepository.Query
            .FirstOrDefaultAsync(r => r.EmailAddress != null && r.EmailAddress.ToLower() == receiverDraft.EmailAddress, cancel);

        if (receiver is null)
        {
            receiver = await ReceiverRepository.CreateAsync(new Receiver
            {
                EmailAddress = receiverDraft.EmailAddress,
                Signature = receiverDraft.EmailAddress.ToUpperInvariant().GetChecksum(),
                AddedWhen = now,
                TotpSecretkey = string.Empty,
                TfaRegDeadline = null
            }, cancel);
        }

        sequence++;
        var link = await EnvelopeReceiverRepository.CreateAsync(new EnvelopeReceiver
        {
            EnvelopeId = envelopeId,
            ReceiverId = receiver.Id,
            Sequence = sequence,
            Name = receiverDraft.Name ?? receiverDraft.EmailAddress,
            JobTitle = string.Empty,
            CompanyName = string.Empty,
            PrivateMessage = string.Empty,
            AccessCode = string.Empty,
            AddedWhen = now,
            ChangedWhen = now,
            PhoneNumber = receiverDraft.PhoneNumber ?? string.Empty
        }, cancel);

        link.Receiver = receiver;
        linksByEmail[receiverDraft.EmailAddress] = link;
        return (link, sequence);
    }

    private async Task SendEnvelopeAsync(Envelope envelope, CancellationToken cancel)
    {
        var hasDocument = await DocumentRepository.Query
            .AnyAsync(d => d.EnvelopeId == envelope.Id && d.ByteData != null && d.ByteData.Length > 0, cancel);

        if (!hasDocument)
            throw new BadRequestException("Cannot send envelope without a document.");

        var links = await EnvelopeReceiverRepository.Query
            .Include(er => er.Receiver)
            .Where(er => er.EnvelopeId == envelope.Id)
            .ToListAsync(cancel);

        if (links.Count == 0)
            throw new BadRequestException("Cannot send envelope without receivers.");

        var receiverIds = links.Select(l => l.ReceiverId).Distinct().ToList();
        var documentIds = await DocumentRepository.Query
            .Where(d => d.EnvelopeId == envelope.Id)
            .Select(d => d.Id)
            .ToListAsync(cancel);

        var receiverFieldCounts = await DocReceiverElementRepository.Query
            .Where(e => documentIds.Contains(e.DocumentId))
            .Where(e => receiverIds.Contains(e.ReceiverId))
            .GroupBy(e => e.ReceiverId)
            .Select(g => new { ReceiverId = g.Key, Count = g.Count() })
            .ToDictionaryAsync(x => x.ReceiverId, x => x.Count, cancel);

        var receiversWithoutFields = links
            .Where(link => !receiverFieldCounts.TryGetValue(link.ReceiverId, out var count) || count <= 0)
            .Select(link => link.Name)
            .ToList();

        if (receiversWithoutFields.Count > 0)
            throw new BadRequestException("Cannot send envelope because some receivers have no signature fields.");

        var changedWhen = DateTime.Now;
        await Repository.UpdateAsync(e =>
        {
            e.Status = EnvelopeStatus.EnvelopeQueued;
            e.ChangedWhen = changedWhen;
        }, e => e.Id == envelope.Id, cancel);

        var userReference = await ResolveSenderReferenceAsync(envelope, cancel);

        await Mediator.Send(new CreateHistoryCommand
        {
            EnvelopeId = envelope.Id,
            UserReference = userReference,
            Status = EnvelopeStatus.EnvelopeQueued
        }, cancel);

        envelope.Status = EnvelopeStatus.EnvelopeQueued;
    }
}