using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using MongoDB.Bson;
using StellaOps.Feedser.Source.CertFr.Configuration;
using StellaOps.Feedser.Source.CertFr.Internal;
using StellaOps.Feedser.Source.Common;
using StellaOps.Feedser.Source.Common.Fetch;
using StellaOps.Feedser.Storage.Mongo;
using StellaOps.Feedser.Storage.Mongo.Advisories;
using StellaOps.Feedser.Storage.Mongo.Documents;
using StellaOps.Feedser.Storage.Mongo.Dtos;
using StellaOps.Plugin;

namespace StellaOps.Feedser.Source.CertFr;

public sealed class CertFrConnector : IFeedConnector
{
    private static readonly JsonSerializerOptions SerializerOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull,
    };

    private readonly CertFrFeedClient _feedClient;
    private readonly SourceFetchService _fetchService;
    private readonly RawDocumentStorage _rawDocumentStorage;
    private readonly IDocumentStore _documentStore;
    private readonly IDtoStore _dtoStore;
    private readonly IAdvisoryStore _advisoryStore;
    private readonly ISourceStateRepository _stateRepository;
    private readonly CertFrOptions _options;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<CertFrConnector> _logger;

    public CertFrConnector(
        CertFrFeedClient feedClient,
        SourceFetchService fetchService,
        RawDocumentStorage rawDocumentStorage,
        IDocumentStore documentStore,
        IDtoStore dtoStore,
        IAdvisoryStore advisoryStore,
        ISourceStateRepository stateRepository,
        IOptions<CertFrOptions> options,
        TimeProvider? timeProvider,
        ILogger<CertFrConnector> logger)
    {
        _feedClient = feedClient ?? throw new ArgumentNullException(nameof(feedClient));
        _fetchService = fetchService ?? throw new ArgumentNullException(nameof(fetchService));
        _rawDocumentStorage = rawDocumentStorage ?? throw new ArgumentNullException(nameof(rawDocumentStorage));
        _documentStore = documentStore ?? throw new ArgumentNullException(nameof(documentStore));
        _dtoStore = dtoStore ?? throw new ArgumentNullException(nameof(dtoStore));
        _advisoryStore = advisoryStore ?? throw new ArgumentNullException(nameof(advisoryStore));
        _stateRepository = stateRepository ?? throw new ArgumentNullException(nameof(stateRepository));
        _options = (options ?? throw new ArgumentNullException(nameof(options))).Value ?? throw new ArgumentNullException(nameof(options));
        _options.Validate();
        _timeProvider = timeProvider ?? TimeProvider.System;
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public string SourceName => CertFrConnectorPlugin.SourceName;

    public async Task FetchAsync(IServiceProvider services, CancellationToken cancellationToken)
    {
        var cursor = await GetCursorAsync(cancellationToken).ConfigureAwait(false);
        var now = _timeProvider.GetUtcNow();
        var windowEnd = now;
        var lastPublished = cursor.LastPublished ?? now - _options.InitialBackfill;
        var windowStart = lastPublished - _options.WindowOverlap;
        var minStart = now - _options.InitialBackfill;
        if (windowStart < minStart)
        {
            windowStart = minStart;
        }

        IReadOnlyList<CertFrFeedItem> items;
        try
        {
            items = await _feedClient.LoadAsync(windowStart, windowEnd, cancellationToken).ConfigureAwait(false);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Cert-FR feed load failed {Start:o}-{End:o}", windowStart, windowEnd);
            await _stateRepository.MarkFailureAsync(SourceName, now, TimeSpan.FromMinutes(10), ex.Message, cancellationToken).ConfigureAwait(false);
            throw;
        }

        if (items.Count == 0)
        {
            await UpdateCursorAsync(cursor.WithLastPublished(windowEnd), cancellationToken).ConfigureAwait(false);
            return;
        }

        var pendingDocuments = cursor.PendingDocuments.ToList();
        var pendingMappings = cursor.PendingMappings.ToList();
        var maxPublished = cursor.LastPublished ?? DateTimeOffset.MinValue;

        foreach (var item in items)
        {
            cancellationToken.ThrowIfCancellationRequested();

            try
            {
                var existing = await _documentStore.FindBySourceAndUriAsync(SourceName, item.DetailUri.ToString(), cancellationToken).ConfigureAwait(false);
                var request = new SourceFetchRequest(CertFrOptions.HttpClientName, SourceName, item.DetailUri)
                {
                    Metadata = CertFrDocumentMetadata.CreateMetadata(item),
                    ETag = existing?.Etag,
                    LastModified = existing?.LastModified,
                    AcceptHeaders = new[] { "text/html", "application/xhtml+xml", "text/plain;q=0.5" },
                };

                var result = await _fetchService.FetchAsync(request, cancellationToken).ConfigureAwait(false);
                if (result.IsNotModified || !result.IsSuccess || result.Document is null)
                {
                    if (item.Published > maxPublished)
                    {
                        maxPublished = item.Published;
                    }

                    continue;
                }

                if (existing is not null
                    && string.Equals(existing.Sha256, result.Document.Sha256, StringComparison.OrdinalIgnoreCase)
                    && string.Equals(existing.Status, DocumentStatuses.Mapped, StringComparison.Ordinal))
                {
                    await _documentStore.UpdateStatusAsync(result.Document.Id, existing.Status, cancellationToken).ConfigureAwait(false);
                    if (item.Published > maxPublished)
                    {
                        maxPublished = item.Published;
                    }

                    continue;
                }

                if (!pendingDocuments.Contains(result.Document.Id))
                {
                    pendingDocuments.Add(result.Document.Id);
                }

                if (item.Published > maxPublished)
                {
                    maxPublished = item.Published;
                }

                if (_options.RequestDelay > TimeSpan.Zero)
                {
                    await Task.Delay(_options.RequestDelay, cancellationToken).ConfigureAwait(false);
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Cert-FR fetch failed for {Uri}", item.DetailUri);
                await _stateRepository.MarkFailureAsync(SourceName, _timeProvider.GetUtcNow(), TimeSpan.FromMinutes(5), ex.Message, cancellationToken).ConfigureAwait(false);
                throw;
            }
        }

        if (maxPublished == DateTimeOffset.MinValue)
        {
            maxPublished = cursor.LastPublished ?? windowEnd;
        }

        var updatedCursor = cursor
            .WithPendingDocuments(pendingDocuments)
            .WithPendingMappings(pendingMappings)
            .WithLastPublished(maxPublished);

        await UpdateCursorAsync(updatedCursor, cancellationToken).ConfigureAwait(false);
    }

    public async Task ParseAsync(IServiceProvider services, CancellationToken cancellationToken)
    {
        var cursor = await GetCursorAsync(cancellationToken).ConfigureAwait(false);
        if (cursor.PendingDocuments.Count == 0)
        {
            return;
        }

        var pendingDocuments = cursor.PendingDocuments.ToList();
        var pendingMappings = cursor.PendingMappings.ToList();

        foreach (var documentId in cursor.PendingDocuments)
        {
            cancellationToken.ThrowIfCancellationRequested();

            var document = await _documentStore.FindAsync(documentId, cancellationToken).ConfigureAwait(false);
            if (document is null)
            {
                pendingDocuments.Remove(documentId);
                pendingMappings.Remove(documentId);
                continue;
            }

            if (!document.GridFsId.HasValue)
            {
                _logger.LogWarning("Cert-FR document {DocumentId} missing GridFS payload", document.Id);
                await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Failed, cancellationToken).ConfigureAwait(false);
                pendingDocuments.Remove(documentId);
                pendingMappings.Remove(documentId);
                continue;
            }

            CertFrDocumentMetadata metadata;
            try
            {
                metadata = CertFrDocumentMetadata.FromDocument(document);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Cert-FR metadata parse failed for document {DocumentId}", document.Id);
                await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Failed, cancellationToken).ConfigureAwait(false);
                pendingDocuments.Remove(documentId);
                pendingMappings.Remove(documentId);
                continue;
            }

            CertFrDto dto;
            try
            {
                var content = await _rawDocumentStorage.DownloadAsync(document.GridFsId.Value, cancellationToken).ConfigureAwait(false);
                var html = System.Text.Encoding.UTF8.GetString(content);
                dto = CertFrParser.Parse(html, metadata);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Cert-FR parse failed for advisory {AdvisoryId} ({Uri})", metadata.AdvisoryId, document.Uri);
                await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Failed, cancellationToken).ConfigureAwait(false);
                pendingDocuments.Remove(documentId);
                pendingMappings.Remove(documentId);
                continue;
            }

            var json = JsonSerializer.Serialize(dto, SerializerOptions);
            var payload = BsonDocument.Parse(json);
            var validatedAt = _timeProvider.GetUtcNow();

            var existingDto = await _dtoStore.FindByDocumentIdAsync(document.Id, cancellationToken).ConfigureAwait(false);
            var dtoRecord = existingDto is null
                ? new DtoRecord(Guid.NewGuid(), document.Id, SourceName, "certfr.detail.v1", payload, validatedAt)
                : existingDto with
                {
                    Payload = payload,
                    SchemaVersion = "certfr.detail.v1",
                    ValidatedAt = validatedAt,
                };

            await _dtoStore.UpsertAsync(dtoRecord, cancellationToken).ConfigureAwait(false);
            await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.PendingMap, cancellationToken).ConfigureAwait(false);

            pendingDocuments.Remove(documentId);
            if (!pendingMappings.Contains(documentId))
            {
                pendingMappings.Add(documentId);
            }
        }

        var updatedCursor = cursor
            .WithPendingDocuments(pendingDocuments)
            .WithPendingMappings(pendingMappings);

        await UpdateCursorAsync(updatedCursor, cancellationToken).ConfigureAwait(false);
    }

    public async Task MapAsync(IServiceProvider services, CancellationToken cancellationToken)
    {
        var cursor = await GetCursorAsync(cancellationToken).ConfigureAwait(false);
        if (cursor.PendingMappings.Count == 0)
        {
            return;
        }

        var pendingMappings = cursor.PendingMappings.ToList();

        foreach (var documentId in cursor.PendingMappings)
        {
            cancellationToken.ThrowIfCancellationRequested();

            var dtoRecord = await _dtoStore.FindByDocumentIdAsync(documentId, cancellationToken).ConfigureAwait(false);
            var document = await _documentStore.FindAsync(documentId, cancellationToken).ConfigureAwait(false);

            if (dtoRecord is null || document is null)
            {
                pendingMappings.Remove(documentId);
                continue;
            }

            CertFrDto? dto;
            try
            {
                var json = dtoRecord.Payload.ToJson();
                dto = JsonSerializer.Deserialize<CertFrDto>(json, SerializerOptions);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Cert-FR DTO deserialization failed for document {DocumentId}", documentId);
                await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Failed, cancellationToken).ConfigureAwait(false);
                pendingMappings.Remove(documentId);
                continue;
            }

            if (dto is null)
            {
                _logger.LogWarning("Cert-FR DTO payload deserialized as null for document {DocumentId}", documentId);
                await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Failed, cancellationToken).ConfigureAwait(false);
                pendingMappings.Remove(documentId);
                continue;
            }

            var mappedAt = _timeProvider.GetUtcNow();
            var advisory = CertFrMapper.Map(dto, SourceName, mappedAt);
            await _advisoryStore.UpsertAsync(advisory, cancellationToken).ConfigureAwait(false);
            await _documentStore.UpdateStatusAsync(document.Id, DocumentStatuses.Mapped, cancellationToken).ConfigureAwait(false);

            pendingMappings.Remove(documentId);
        }

        var updatedCursor = cursor.WithPendingMappings(pendingMappings);
        await UpdateCursorAsync(updatedCursor, cancellationToken).ConfigureAwait(false);
    }

    private async Task<CertFrCursor> GetCursorAsync(CancellationToken cancellationToken)
    {
        var record = await _stateRepository.TryGetAsync(SourceName, cancellationToken).ConfigureAwait(false);
        return CertFrCursor.FromBson(record?.Cursor);
    }

    private async Task UpdateCursorAsync(CertFrCursor cursor, CancellationToken cancellationToken)
    {
        var completedAt = _timeProvider.GetUtcNow();
        await _stateRepository.UpdateCursorAsync(SourceName, cursor.ToBsonDocument(), completedAt, cancellationToken).ConfigureAwait(false);
    }
}