using System.Security.Claims;
using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Configuration;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Interfaces;

namespace SeaHaven.Services.Implementation
{
    public class WorkOrderUpliftEvidenceService : IWorkOrderUpliftEvidenceService
    {
        private static readonly HashSet<string> AllowedContentTypes = new(StringComparer.OrdinalIgnoreCase)
        {
            "application/pdf", "image/jpeg", "image/jpg", "image/png"
        };

        private readonly IWorkOrderDetailDataService _detailData;
        private readonly IDispatchDataService _dispatchData;
        private readonly IVendorDocumentDataService _documentData;
        private readonly IVendorDocumentStoragePort _documentStorage;
        private readonly IWorkOrderAccountResolver _accountResolver;
        private readonly VendorDocumentsOptions _documentOptions;

        public WorkOrderUpliftEvidenceService(
            IWorkOrderDetailDataService detailData,
            IDispatchDataService dispatchData,
            IVendorDocumentDataService documentData,
            IVendorDocumentStoragePort documentStorage,
            IWorkOrderAccountResolver accountResolver,
            IOptions<VendorDocumentsOptions> documentOptions)
        {
            _detailData = detailData;
            _dispatchData = dispatchData;
            _documentData = documentData;
            _documentStorage = documentStorage;
            _accountResolver = accountResolver;
            _documentOptions = documentOptions.Value;
        }

        public async Task<UploadCompletionDocumentResultDTO?> UploadAsync(
            int workOrderId,
            IFormFile file,
            ClaimsPrincipal user,
            CancellationToken cancellationToken)
        {
            var target = await ResolveOpenDispatchAsync(workOrderId, user, cancellationToken);
            if (target == null)
                return null;

            var (contentType, bytes) = await ReadAcceptedFileAsync(file, cancellationToken);
            var latest = await _documentData.GetLatestForDispatchAsync(target.Dispatch.Id, cancellationToken);
            var version = (latest?.Version ?? 0) + 1;
            var storedFileName = $"{target.Dispatch.Id}_{version}_{Guid.NewGuid():N}{SafeExtension(file.FileName)}";
            var now = DateTime.UtcNow;
            var passWithoutScanner = _documentOptions.PassWhenScannerUnavailable;
            var document = new VendorCompletionDocument
            {
                VendorId = target.Dispatch.VendorId,
                DispatchId = target.Dispatch.Id,
                WorkOrderId = workOrderId,
                OriginalFileName = Path.GetFileName(file.FileName),
                StoredFileName = storedFileName,
                ContentType = contentType,
                SizeBytes = bytes.Length,
                ScanStatus = passWithoutScanner ? "Passed" : "Pending",
                ReviewStatus = "Processing",
                ScannedAt = passWithoutScanner ? now : null,
                Version = version,
                Purpose = VendorDocumentPurpose.UpliftEvidence,
                CreatedDate = now
            };

            await _documentData.AddAsync(document, cancellationToken);
            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = workOrderId,
                DispatchId = target.Dispatch.Id,
                UserId = user.FindFirstValue(ClaimTypes.NameIdentifier),
                FieldName = $"Dispatch {target.Dispatch.DispatchNumber} Uplift Evidence",
                NewValue = document.OriginalFileName,
                Action = "uplift_evidence_uploaded",
                ActorType = "internal",
                CreatedAt = now
            }, cancellationToken);
            await _documentData.SaveChangesAsync(cancellationToken);

            using var stored = new MemoryStream(bytes);
            await _documentStorage.SaveAsync(
                target.Dispatch.VendorId,
                target.Dispatch.Id,
                storedFileName,
                stored,
                cancellationToken);

            return new UploadCompletionDocumentResultDTO
            {
                Id = document.Id,
                Version = document.Version,
                ScanStatus = document.ScanStatus,
                ReviewStatus = document.ReviewStatus,
                Purpose = document.Purpose
            };
        }

        public async Task<VendorDocumentStatusDTO?> GetStatusAsync(
            int workOrderId,
            int documentId,
            ClaimsPrincipal user,
            CancellationToken cancellationToken)
        {
            var target = await ResolveOpenDispatchAsync(workOrderId, user, cancellationToken);
            if (target == null)
                return null;

            var document = await _documentData.GetMetadataForVendorDispatchAsync(
                documentId,
                target.Dispatch.Id,
                target.Dispatch.VendorId,
                cancellationToken);
            if (document == null || document.Purpose != VendorDocumentPurpose.UpliftEvidence)
                return null;

            return new VendorDocumentStatusDTO
            {
                Id = document.Id,
                OriginalFileName = document.OriginalFileName,
                ScanStatus = document.ScanStatus,
                ReviewStatus = document.ReviewStatus,
                Purpose = document.Purpose
            };
        }

        private async Task<OpenDispatch?> ResolveOpenDispatchAsync(
            int workOrderId,
            ClaimsPrincipal user,
            CancellationToken cancellationToken)
        {
            var accountFilter = _accountResolver.ResolveAccountFilter(user);
            if (!await _detailData.ExistsAsync(workOrderId, cancellationToken, accountFilter))
                return null;

            var workOrder = await _detailData.GetWorkOrderForMediaAsync(
                workOrderId,
                cancellationToken,
                accountFilter);
            if (workOrder?.PrimaryDispatchId is not int dispatchId)
                throw new InvalidOperationException("Work order has no primary dispatch for uplift requests");

            if (workOrder.LifecycleStatus is LifecycleStatus.Completed or LifecycleStatus.Canceled)
            {
                throw new InvalidOperationException(
                    $"Cannot attach uplift evidence on a '{workOrder.LifecycleStatus}' work order");
            }

            var dispatch = await _dispatchData.GetByIdAsync(dispatchId);
            if (dispatch == null)
                throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status is "Verified" or "Cancelled" or "Canceled" or "Refused")
                throw new InvalidOperationException($"Cannot attach uplift evidence on a '{dispatch.Status}' dispatch");

            return new OpenDispatch(dispatch);
        }

        private async Task<(string ContentType, byte[] Bytes)> ReadAcceptedFileAsync(
            IFormFile file,
            CancellationToken cancellationToken)
        {
            if (file is null || file.Length == 0)
                throw new InvalidOperationException("An evidence file is required.");

            if (file.Length > _documentOptions.MaxSizeBytes)
                throw new InvalidOperationException("The uploaded file exceeds the maximum allowed size.");

            var contentType = (file.ContentType ?? string.Empty).Trim();
            if (!AllowedContentTypes.Contains(contentType))
                throw new InvalidOperationException("Only PDF, JPG, and PNG documents are accepted.");

            using var buffer = new MemoryStream();
            await file.CopyToAsync(buffer, cancellationToken);
            var bytes = buffer.ToArray();
            if (!MatchesSignature(contentType, bytes))
                throw new InvalidOperationException("The uploaded file signature does not match its declared content type.");

            return (contentType, bytes);
        }

        private static bool MatchesSignature(string contentType, byte[] bytes)
        {
            if (bytes.Length == 0)
                return false;

            if (contentType.Equals("application/pdf", StringComparison.OrdinalIgnoreCase))
            {
                return bytes.Length >= 4
                    && bytes[0] == 0x25 && bytes[1] == 0x50 && bytes[2] == 0x44 && bytes[3] == 0x46;
            }

            if (contentType.Equals("image/png", StringComparison.OrdinalIgnoreCase))
            {
                return bytes.Length >= 8
                    && bytes[0] == 0x89 && bytes[1] == 0x50 && bytes[2] == 0x4E && bytes[3] == 0x47
                    && bytes[4] == 0x0D && bytes[5] == 0x0A && bytes[6] == 0x1A && bytes[7] == 0x0A;
            }

            if (contentType.Equals("image/jpeg", StringComparison.OrdinalIgnoreCase)
                || contentType.Equals("image/jpg", StringComparison.OrdinalIgnoreCase))
            {
                return bytes.Length >= 3 && bytes[0] == 0xFF && bytes[1] == 0xD8 && bytes[2] == 0xFF;
            }

            return false;
        }

        private static string SafeExtension(string fileName)
        {
            var extension = Path.GetExtension(fileName);
            return string.IsNullOrWhiteSpace(extension) ? string.Empty : extension;
        }

        private sealed record OpenDispatch(Dispatch Dispatch);
    }
}