using System.Security.Claims;
using System.Text.Json;
using DigitalData.Core.Exceptions;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Application.Common.Dto.EnvelopeReceiver;
using EnvelopeGenerator.Application.Documents.Queries;
using EnvelopeGenerator.Application.EnvelopeReceivers.Queries;
using EnvelopeGenerator.Application.Receivers.Queries;
using EnvelopeGenerator.Server.Client.Models;
using EnvelopeGenerator.Server.Client.Models.Constants;
using EnvelopeGenerator.Server.Extensions;
using EnvelopeGenerator.Server.Options;
using MediatR;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Options;
using ApplicationEnvelopeReceiverDto = EnvelopeGenerator.Application.Common.Dto.EnvelopeReceiver.EnvelopeReceiverDto;

namespace EnvelopeGenerator.Server.Services;

/// <summary>
/// Loads receiver page data directly from MediatR and distributed cache.
/// </summary>
public class EnvelopeReceiverPageDataService(
    IMediator mediator,
    IDistributedCache cache,
    IOptions<CacheOptions> cacheOptions,
    IMemoryCache memoryCache)
{
    private const string SignatureCacheKeyPrefix = "envelope-generator.receiver-ui.signature:";

    /// <summary>
    /// Loads the PDF document bytes for the authenticated receiver.
    /// </summary>
    public async Task<byte[]?> GetDocumentOfReceiverAsync(ClaimsPrincipal user, CancellationToken cancellationToken = default)
    {
        var document = await mediator.Send(new ReadDocumentQuery(EnvelopeId: user.EnvelopeId()), cancellationToken);
        return document.ByteData;
    }

    /// <summary>
    /// Loads the PDF document bytes for the authenticated receiver.
    /// </summary>
    public async Task<byte[]?> GetDocumentOfSenderAsync(ClaimsPrincipal user, int envelopeId, CancellationToken cancellationToken = default)
    {
        var document = await mediator.Send(new ReadDocumentQuery(EnvelopeId: envelopeId, UserId: user.SenderId()), cancellationToken);
        return (document.ByteData is byte[] data && data.Length > 0)
            ? data
            : throw new NotFoundException($"Document for envelope {envelopeId} not found.");
    }

    /// <summary>
    /// Loads the full document DTO (including receiver elements) for the authenticated sender.
    /// </summary>
    public async Task<DocumentDto?> GetDocumentDetailsOfSenderAsync(ClaimsPrincipal user, int envelopeId, CancellationToken cancellationToken = default)
    {
        return await mediator.Send(new ReadDocumentQuery(EnvelopeId: envelopeId, UserId: user.SenderId()), cancellationToken);
    }

    /// <summary>
    /// Loads the current receiver's signature placeholders.
    /// </summary>
    public async Task<IReadOnlyList<SignatureDto>> GetSignaturesAsync(ClaimsPrincipal user, CancellationToken cancellationToken = default)
    {
        var receiverId = user.ReceiverId();
        var document = await mediator.Send(new ReadDocumentQuery(EnvelopeId: user.EnvelopeId()), cancellationToken);

        if (document.Elements is not IEnumerable<DocReceiverElementDto> elements)
            return [];

        var signatures = elements
            .Where(element => element.ReceiverId == receiverId)
            .Select(MapSignature)
            .ToList();

        return signatures.Convert(UnitOfLength.Point);
    }

    /// <summary>
    /// Loads the envelope receiver data for the specified envelope key.
    /// </summary>
    public async Task<ApplicationEnvelopeReceiverDto?> GetEnvelopeReceiverAsync(string envelopeKey, CancellationToken cancellationToken = default)
    {
        var result = await mediator.Send(new ReadEnvelopeReceiverQuery { Key = envelopeKey }, cancellationToken);
        return result.SingleOrDefault();
    }

    /// <summary>
    /// Loads the cached signature for the authenticated receiver.
    /// </summary>
    public async Task<SignatureCaptureDto?> GetCachedSignatureAsync(ClaimsPrincipal user, CancellationToken cancellationToken = default)
    {
        var json = await cache.GetStringAsync(GetSignatureCacheKey(user), cancellationToken);
        return json is null ? null : JsonSerializer.Deserialize<SignatureCaptureDto>(json);
    }

    /// <summary>
    /// Saves the cached signature for the authenticated receiver.
    /// </summary>
    public async Task SaveCachedSignatureAsync(ClaimsPrincipal user, SignatureCaptureDto signature, CancellationToken cancellationToken = default)
    {
        var json = JsonSerializer.Serialize(signature);
        var options = cacheOptions.Value.SignatureCacheExpiration.HasValue
            ? new DistributedCacheEntryOptions { AbsoluteExpirationRelativeToNow = cacheOptions.Value.SignatureCacheExpiration.Value }
            : new DistributedCacheEntryOptions();

        await cache.SetStringAsync(GetSignatureCacheKey(user), json, options, cancellationToken);
    }

    /// <summary>
    /// Deletes the cached signature for the authenticated receiver.
    /// </summary>
    public Task DeleteCachedSignatureAsync(ClaimsPrincipal user, CancellationToken cancellationToken = default)
        => cache.RemoveAsync(GetSignatureCacheKey(user), cancellationToken);

    private static string GetSignatureCacheKey(ClaimsPrincipal user)
        => $"{SignatureCacheKeyPrefix}{user.ReceiverSignature()}";

    private static SignatureDto MapSignature(DocReceiverElementDto element) => new()
    {
        Id = element.Id,
        X = element.X,
        Y = element.Y,
        Page = element.Page,
        SenderAppType = (EnvelopeGenerator.Server.Client.Models.Constants.SenderAppType)element.SenderAppType
    };

    private static readonly string ReceiverEmailSearchCacheKey = Guid.NewGuid().ToString();

    public async Task<IEnumerable<string>> SearchReceiverEMailsAsync(string emailSearchTerm, CancellationToken cancellationToken = default)
    {

        return await memoryCache.GetOrCreateAsync(ReceiverEmailSearchCacheKey + emailSearchTerm, async entry =>
        {
            var query = new ReadReceiverQuery { EmailAddressSearch = emailSearchTerm };
            var receivers = await mediator.Send(query, cancellationToken);

            if(receivers.Any())
                entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromSeconds(30);
            else
                entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromSeconds(10);

            return receivers.Select(r => r.EmailAddress);
        }) ?? [];
    }
}