using Data.SeaHavenIndustries;
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 VendorPortalService : IVendorPortalService
    {
        private static readonly HashSet<string> AllowedContentTypes = new(StringComparer.OrdinalIgnoreCase)
        {
            "application/pdf", "image/jpeg", "image/jpg", "image/png"
        };

        private readonly IVendorPortalTokenService _tokens;
        private readonly IDispatchDataService _dispatchData;
        private readonly IUpliftDataService _upliftData;
        private readonly ICommentDataService _commentData;
        private readonly IUserDataService _userData;
        private readonly IEmailSender _emailSender;
        private readonly IVendorDocumentDataService _documentData;
        private readonly IVendorDocumentStoragePort _documentStorage;
        private readonly FrontendOptions _frontendOptions;
        private readonly ApprovalsOptions _approvalsOptions;
        private readonly VendorDocumentsOptions _documentOptions;

        public VendorPortalService(
            IVendorPortalTokenService tokens,
            IDispatchDataService dispatchData,
            IUpliftDataService upliftData,
            ICommentDataService commentData,
            IUserDataService userData,
            IEmailSender emailSender,
            IVendorDocumentDataService documentData,
            IVendorDocumentStoragePort documentStorage,
            IOptions<FrontendOptions> frontendOptions,
            IOptions<ApprovalsOptions> approvalsOptions,
            IOptions<VendorDocumentsOptions> documentOptions)
        {
            _tokens = tokens;
            _dispatchData = dispatchData;
            _upliftData = upliftData;
            _commentData = commentData;
            _userData = userData;
            _emailSender = emailSender;
            _documentData = documentData;
            _documentStorage = documentStorage;
            _frontendOptions = frontendOptions.Value;
            _approvalsOptions = approvalsOptions.Value;
            _documentOptions = documentOptions.Value;
        }

        public async Task<VendorPortalSession?> ResolveSessionAsync(string? token, CancellationToken cancellationToken)
        {
            return await _tokens.ResolveSessionAsync(token, cancellationToken);
        }

        public async Task<IEnumerable<VendorDispatchSummaryDTO>> ListDispatchesAsync(VendorPortalSession session, string? status, CancellationToken cancellationToken)
        {
            var summaries = await _dispatchData.GetVendorDispatchSummariesAsync(session.Id, status, cancellationToken);

            return summaries.Select(d => new VendorDispatchSummaryDTO
            {
                Id = d.Id,
                DispatchNumber = d.DispatchNumber,
                PONumber = d.PONumber,
                Status = d.Status,
                NTEAmount = d.NTEAmount,
                ScheduledDate = d.ScheduledDate,
                CompletedDate = d.CompletedDate,
                DispatchedAt = d.DispatchedAt,
                AcknowledgedAt = d.AcknowledgedAt,
                WorkOrderTitle = d.WorkOrderTitle,
                InternalWONumber = d.InternalWONumber,
                LocationName = d.LocationName,
                LocationCity = d.LocationCity,
                LocationState = d.LocationState
            });
        }

        public async Task<VendorDispatchDetailDTO?> GetDispatchDetailAsync(VendorPortalSession session, int id, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchDetailAsync(id, session.Id, cancellationToken);
            if (dispatch == null) return null;

            var checklist = await _dispatchData.GetPortalChecklistAsync(id, cancellationToken);
            var signoffs = await _dispatchData.GetPortalSignoffsAsync(id, cancellationToken);
            var rawUplifts = await _upliftData.GetForVendorDispatchAsync(id, cancellationToken);
            var rawComments = await _commentData.GetVendorViewableForDispatchAsync(id, cancellationToken);

            var upliftRequests = rawUplifts.Select(u => new PortalUpliftDTO
            {
                Id = u.Id,
                CurrentNTE = u.CurrentNTE,
                RequestedNTE = u.RequestedNTE,
                VendorReason = u.VendorReason,
                Status = u.Status,
                RequiredTier = u.RequiredTier,
                RequestedByVendorName = u.RequestedByVendorName,
                RequestedAt = u.CreatedDate,
                DecidedAt = u.DecidedAt,
                DecisionNote = u.DecisionNote,
                DecidedByName = string.Join(" ", new[] { u.DecidedByFirstName, u.DecidedByLastName }
                    .Where(s => !string.IsNullOrWhiteSpace(s))).Trim()
            }).ToList();

            var comments = rawComments.Select(c =>
            {
                var hasShocUser = !string.IsNullOrWhiteSpace(c.UserId);
                var userName = string.Join(" ", new[] { c.UserFirstName, c.UserLastName }
                    .Where(s => !string.IsNullOrWhiteSpace(s))).Trim();

                string resolvedType;
                string resolvedCommenter;
                if (hasShocUser)
                {
                    resolvedType = "dispatcher";
                    resolvedCommenter = !string.IsNullOrWhiteSpace(userName) ? userName
                        : !string.IsNullOrWhiteSpace(c.Commenter) ? c.Commenter!
                        : "Dispatcher";
                }
                else if (c.CommentType == "customer")
                {
                    resolvedType = "customer";
                    resolvedCommenter = !string.IsNullOrWhiteSpace(c.Commenter) ? c.Commenter! : "Customer";
                }
                else
                {
                    resolvedType = "vendor";
                    resolvedCommenter = !string.IsNullOrWhiteSpace(c.Commenter) ? c.Commenter! : session.CompanyName ?? "Vendor";
                }

                return new PortalCommentDTO
                {
                    Id = c.Id,
                    Commenttext = c.Commenttext,
                    Commenter = resolvedCommenter,
                    CommentType = resolvedType,
                    CreatedDate = c.CreatedDate
                };
            }).ToList();

            return new VendorDispatchDetailDTO
            {
                Id = dispatch.Id,
                DispatchNumber = dispatch.DispatchNumber,
                PONumber = dispatch.PONumber,
                Status = dispatch.Status,
                NTEAmount = dispatch.NTEAmount,
                Description = dispatch.Description,
                ScheduledDate = dispatch.ScheduledDate,
                CompletedDate = dispatch.CompletedDate,
                DispatchedAt = dispatch.DispatchedAt,
                AcknowledgedAt = dispatch.AcknowledgedAt,
                WorkOrder = dispatch.WorkOrder == null ? null : new PortalWorkOrderDTO
                {
                    Id = dispatch.WorkOrder.Id,
                    InternalWONumber = dispatch.WorkOrder.InternalWONumber,
                    WorkerOrderTitle = dispatch.WorkOrder.WorkerOrderTitle,
                    Description = dispatch.WorkOrder.Description,
                    Priority = dispatch.WorkOrder.Priority,
                    DueDate = dispatch.WorkOrder.DueDate,
                    Trade = dispatch.WorkOrder.Trade,
                    SubTrade = dispatch.WorkOrder.SubTrade,
                    Problem = dispatch.WorkOrder.Problem
                },
                Location = dispatch.WorkOrder?.Locations == null ? null : new PortalLocationDTO
                {
                    Name = dispatch.WorkOrder.Locations.Name,
                    Address1 = dispatch.WorkOrder.Locations.Address1,
                    City = dispatch.WorkOrder.Locations.City,
                    State = dispatch.WorkOrder.Locations.State,
                    Zip = dispatch.WorkOrder.Locations.Zip
                },
                Checklist = checklist.Select(c => new PortalChecklistItemDTO
                {
                    Id = c.Id,
                    ItemText = c.ItemText,
                    IsCompleted = c.IsCompleted,
                    CompletedBy = c.CompletedBy,
                    CompletedAt = c.CompletedAt
                }),
                Signoffs = signoffs.Select(s => new PortalSignoffDTO
                {
                    Id = s.Id,
                    SignoffType = s.SignoffType,
                    Name = s.Name,
                    SignatureMethod = s.SignatureMethod,
                    SignedAt = s.SignedAt
                }),
                Comments = comments,
                UpliftRequests = upliftRequests
            };
        }

        public async Task<AcceptDispatchResultDTO> AcceptDispatchAsync(VendorPortalSession session, int id, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status != "Sent")
            {
                throw new InvalidOperationException($"Cannot accept a dispatch with status '{dispatch.Status}'");
            }

            var now = DateTime.UtcNow;
            dispatch.Status = "Acknowledged";
            dispatch.AcknowledgedAt = now;
            dispatch.LastModificationTime = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Status",
                OldValue = "Sent",
                NewValue = "Acknowledged",
                Action = "vendor_accept",
                CreatedAt = now
            }, cancellationToken);

            await _dispatchData.SaveChangesAsync(cancellationToken);
            return new AcceptDispatchResultDTO { Id = dispatch.Id, Status = dispatch.Status, AcknowledgedAt = dispatch.AcknowledgedAt };
        }

        public async Task<ChangeStatusResultDTO> ChangeStatusAsync(VendorPortalSession session, int id, string? to, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            var from = dispatch.Status;
            if (!IsAllowedVendorTransition(from, to))
            {
                throw new InvalidOperationException($"Transition from '{from}' to '{to}' is not allowed");
            }

            var now = DateTime.UtcNow;
            dispatch.Status = to;
            dispatch.LastModificationTime = now;
            if (to == "Completed") dispatch.CompletedDate = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Status",
                OldValue = from,
                NewValue = to,
                Action = "vendor_status_change",
                CreatedAt = now
            }, cancellationToken);

            await _dispatchData.SaveChangesAsync(cancellationToken);
            return new ChangeStatusResultDTO { Id = dispatch.Id, Status = dispatch.Status, CompletedDate = dispatch.CompletedDate };
        }

        public async Task RequestCancelAsync(VendorPortalSession session, int id, string? reason, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status == "Verified" || dispatch.Status == "Cancelled")
            {
                throw new InvalidOperationException($"Cannot request cancel on a '{dispatch.Status}' dispatch");
            }

            var now = DateTime.UtcNow;
            var reasonText = string.IsNullOrWhiteSpace(reason) ? "(no reason provided)" : reason!.Trim();

            await _commentData.StageAsync(new Comments
            {
                DispatchId = id,
                WorkerOrderId = dispatch.WorkOrderId,
                Commenter = session.CompanyName,
                CommentType = "vendor",
                RecordType = "cancel_request",
                Commenttext = $"Vendor requested cancellation: {reasonText}",
                CreatedDate = now
            }, cancellationToken);

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber}",
                OldValue = dispatch.Status,
                NewValue = "Cancel Requested",
                Action = "vendor_request_cancel",
                CreatedAt = now
            }, cancellationToken);

            await _dispatchData.SaveChangesAsync(cancellationToken);
        }

        public async Task<ChecklistItemResultDTO> UpdateChecklistItemAsync(VendorPortalSession session, int id, int itemId, bool isCompleted, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status == "Verified" || dispatch.Status == "Cancelled")
            {
                throw new InvalidOperationException("Dispatch is locked");
            }

            var item = await _dispatchData.GetChecklistItemForDispatchAsync(itemId, id, cancellationToken);
            if (item == null) throw new KeyNotFoundException("Checklist item not found");

            var now = DateTime.UtcNow;
            item.IsCompleted = isCompleted;
            item.CompletedBy = isCompleted ? session.CompanyName : null;
            item.CompletedAt = isCompleted ? now : null;
            item.LastModificationTime = now;

            await _dispatchData.SaveChangesAsync(cancellationToken);
            return new ChecklistItemResultDTO
            {
                Id = item.Id,
                IsCompleted = item.IsCompleted,
                CompletedBy = item.CompletedBy,
                CompletedAt = item.CompletedAt
            };
        }

        public async Task<SignoffResultDTO> AddSignoffAsync(VendorPortalSession session, int id, string? signoffType, string? name, string? signature, string? signatureMethod, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status != "In Progress" && dispatch.Status != "Completed")
            {
                throw new InvalidOperationException("Signoffs only allowed on In Progress or Completed dispatches");
            }

            if (string.IsNullOrWhiteSpace(name) || string.IsNullOrWhiteSpace(signature))
            {
                throw new InvalidOperationException("Name and signature are required");
            }

            var normalizedSignoffType = (signoffType ?? "vendor").Trim().ToLowerInvariant();
            if (normalizedSignoffType != "vendor" && normalizedSignoffType != "customer")
            {
                throw new InvalidOperationException("signoffType must be 'vendor' or 'customer'");
            }

            var existing = await _dispatchData.HasSignoffTypeAsync(id, normalizedSignoffType);
            if (existing)
            {
                throw new InvalidOperationException($"A {normalizedSignoffType} signoff already exists for this dispatch");
            }

            var now = DateTime.UtcNow;
            var signoff = new DispatchSignoff
            {
                DispatchId = id,
                SignoffType = normalizedSignoffType,
                Name = name,
                Signature = signature,
                SignatureMethod = signatureMethod ?? "drawn",
                SignedAt = now,
                CreatedDate = now
            };
            await _dispatchData.StageSignoffAsync(signoff, cancellationToken);

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Signoff",
                OldValue = null,
                NewValue = $"{(normalizedSignoffType == "customer" ? "Customer" : "Vendor")}: {name}",
                Action = normalizedSignoffType == "customer" ? "customer_signoff" : "vendor_signoff",
                CreatedAt = now
            }, cancellationToken);

            await _dispatchData.SaveChangesAsync(cancellationToken);
            return new SignoffResultDTO { Id = signoff.Id, SignedAt = signoff.SignedAt };
        }

        public async Task<CommentResultDTO> AddCommentAsync(VendorPortalSession session, int id, string? commentText, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (string.IsNullOrWhiteSpace(commentText))
            {
                throw new InvalidOperationException("Comment cannot be empty");
            }

            var now = DateTime.UtcNow;
            var comment = new Comments
            {
                DispatchId = id,
                WorkerOrderId = dispatch.WorkOrderId,
                Commenter = session.CompanyName,
                CommentType = "vendor",
                RecordType = "comment",
                Commenttext = commentText,
                CreatedDate = now
            };
            await _commentData.StageAsync(comment, cancellationToken);
            await _dispatchData.SaveChangesAsync(cancellationToken);

            return new CommentResultDTO
            {
                Id = comment.Id,
                Commenttext = comment.Commenttext,
                Commenter = comment.Commenter,
                CreatedDate = comment.CreatedDate
            };
        }

        public async Task<UpliftRequestResultDTO> RequestUpliftAsync(VendorPortalSession session, int id, decimal requestedNTE, string? reason, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            if (dispatch.Status == "Verified" || dispatch.Status == "Cancelled")
            {
                throw new InvalidOperationException($"Cannot request uplift on a '{dispatch.Status}' dispatch");
            }

            if (requestedNTE <= 0)
            {
                throw new InvalidOperationException("Requested NTE must be greater than zero");
            }

            var current = dispatch.NTEAmount ?? 0m;
            if (requestedNTE <= current)
            {
                throw new InvalidOperationException("Requested NTE must be greater than the current NTE");
            }

            var pendingExists = await _upliftData.HasPendingAsync(id, cancellationToken);
            if (pendingExists)
            {
                throw new InvalidOperationException("A pending uplift request already exists for this dispatch");
            }

            var tier1Max = _approvalsOptions.UpliftTier1MaxUsd ?? 2500m;
            var delta = requestedNTE - current;
            var requiredTier = delta > tier1Max ? 2 : 1;

            var now = DateTime.UtcNow;
            var req = new DispatchUpliftRequest
            {
                DispatchId = id,
                CurrentNTE = current,
                RequestedNTE = requestedNTE,
                VendorReason = string.IsNullOrWhiteSpace(reason) ? null : reason!.Trim(),
                Status = "Pending",
                RequiredTier = requiredTier,
                RequestedByVendorName = session.CompanyName,
                CreatedDate = now
            };
            await _upliftData.StageAsync(req, cancellationToken);

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Uplift",
                OldValue = $"${current:F2}",
                NewValue = $"${requestedNTE:F2}",
                Action = "uplift_requested",
                CreatedAt = now
            }, cancellationToken);

            await _upliftData.SaveChangesAsync(cancellationToken);

            await NotifyDispatcherOfUpliftAsync(dispatch, req, session, cancellationToken);

            return new UpliftRequestResultDTO
            {
                Id = req.Id,
                Status = req.Status,
                RequiredTier = req.RequiredTier,
                CurrentNTE = req.CurrentNTE,
                RequestedNTE = req.RequestedNTE
            };
        }

        public async Task<CancelUpliftResultDTO> CancelUpliftRequestAsync(VendorPortalSession session, int id, int requestId, CancellationToken cancellationToken)
        {
            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(id, session.Id, cancellationToken);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");

            var req = await _upliftData.GetByIdAndDispatchAsync(requestId, id, cancellationToken);
            if (req == null) throw new KeyNotFoundException("Uplift request not found");

            if (req.Status != "Pending")
            {
                throw new InvalidOperationException($"Cannot cancel a '{req.Status}' uplift request");
            }

            var now = DateTime.UtcNow;
            req.Status = "Cancelled";
            req.DecidedAt = now;
            req.LastModificationTime = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Uplift",
                OldValue = "Pending",
                NewValue = "Cancelled",
                Action = "uplift_cancelled",
                CreatedAt = now
            }, cancellationToken);

            await _upliftData.SaveChangesAsync(cancellationToken);
            return new CancelUpliftResultDTO { Id = req.Id, Status = req.Status };
        }

        public async Task<UploadCompletionDocumentResultDTO> UploadCompletionDocumentAsync(
            VendorPortalSession session, int dispatchId, IFormFile file, CancellationToken cancellationToken)
        {
            if (file is null || file.Length == 0)
            {
                throw new InvalidOperationException("A completion document 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 completion 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.");
            }

            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(dispatchId, session.Id, cancellationToken);
            if (dispatch == null)
            {
                throw new KeyNotFoundException("Dispatch not found");
            }

            var latest = await _documentData.GetLatestForDispatchAsync(dispatchId, cancellationToken);
            var version = (latest?.Version ?? 0) + 1;
            var storedFileName = $"{dispatchId}_{version}_{Guid.NewGuid():N}{GetSafeExtension(file.FileName)}";

            var now = DateTime.UtcNow;
            var document = new VendorCompletionDocument
            {
                VendorId = session.Id,
                DispatchId = dispatchId,
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                OriginalFileName = Path.GetFileName(file.FileName),
                StoredFileName = storedFileName,
                ContentType = contentType,
                SizeBytes = bytes.Length,
                ScanStatus = "Pending",
                ReviewStatus = "Processing",
                Version = version,
                ReplacesDocumentId = latest?.Id,
                CreatedDate = now
            };

            await _documentData.AddAsync(document, cancellationToken);
            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                DispatchId = dispatchId,
                FieldName = $"Dispatch {dispatch.DispatchNumber} Completion Document",
                OldValue = latest == null ? null : $"v{latest.Version}",
                NewValue = $"v{version}",
                Action = "vendor_completion_document_uploaded",
                ActorType = "vendor",
                CreatedAt = now
            }, cancellationToken);
            await _documentData.SaveChangesAsync(cancellationToken);

            using var stored = new MemoryStream(bytes);
            await _documentStorage.SaveAsync(session.Id, dispatchId, storedFileName, stored, cancellationToken);

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

        public async Task<DownloadCompletionDocumentResultDTO> DownloadCompletionDocumentAsync(
            VendorPortalSession session, int dispatchId, int documentId, CancellationToken cancellationToken)
        {
            var document = await _documentData.GetForVendorDispatchAsync(documentId, dispatchId, session.Id, cancellationToken);
            if (document == null)
            {
                return DownloadCompletionDocumentResultDTO.NotFound();
            }

            if (!string.Equals(document.ScanStatus, "Passed", StringComparison.OrdinalIgnoreCase))
            {
                return DownloadCompletionDocumentResultDTO.Locked();
            }

            var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(dispatchId, session.Id, cancellationToken);
            if (dispatch != null && (dispatch.Status == "Verified" || dispatch.Status == "Cancelled"))
            {
                return DownloadCompletionDocumentResultDTO.Locked();
            }

            var content = _documentStorage.OpenRead(session.Id, dispatchId, document.StoredFileName);
            return DownloadCompletionDocumentResultDTO.Ok(content, document.ContentType, document.OriginalFileName);
        }

        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; // %PDF
            }

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

        private async Task NotifyDispatcherOfUpliftAsync(Dispatch dispatch, DispatchUpliftRequest req, VendorPortalSession session, CancellationToken cancellationToken)
        {
            try
            {
                var dispatcherUserId = await _dispatchData.GetDispatchDispatcherUserIdAsync(dispatch.WorkOrderId ?? 0, cancellationToken);
                if (string.IsNullOrWhiteSpace(dispatcherUserId)) return;

                var dispatcherEmail = await _userData.GetEmailByIdAsync(dispatcherUserId, cancellationToken);
                if (string.IsNullOrWhiteSpace(dispatcherEmail)) return;

                var frontendBase = _frontendOptions.FrontendBaseUrl?.TrimEnd('/') ?? "";
                var workOrderLink = dispatch.WorkOrderId.HasValue
                    ? $"{frontendBase}/workorders/{dispatch.WorkOrderId.Value}"
                    : frontendBase;

                var vendorName = System.Net.WebUtility.HtmlEncode(session.CompanyName ?? "Vendor");
                var reason = System.Net.WebUtility.HtmlEncode(req.VendorReason ?? "(no reason provided)");
                var dispatchNum = System.Net.WebUtility.HtmlEncode(dispatch.DispatchNumber ?? "");
                var tierText = req.RequiredTier == 2 ? "Tier 2 (Manager approval required)" : "Tier 1";

                var subject = $"[Uplift Request] {dispatch.DispatchNumber} — {session.CompanyName} requests ${req.RequestedNTE:F2} (was ${req.CurrentNTE ?? 0m:F2})";
                var body = $@"
                    <h2>Vendor Uplift Request</h2>
                    <p><strong>Dispatch:</strong> {dispatchNum}</p>
                    <p><strong>Vendor:</strong> {vendorName}</p>
                    <table style='border-collapse:collapse;font-family:Arial,sans-serif;'>
                        <tr><td style='padding:4px 10px;'><strong>Current NTE</strong></td><td style='padding:4px 10px;'>${req.CurrentNTE ?? 0m:F2}</td></tr>
                        <tr><td style='padding:4px 10px;'><strong>Requested NTE</strong></td><td style='padding:4px 10px;'>${req.RequestedNTE:F2}</td></tr>
                        <tr><td style='padding:4px 10px;'><strong>Delta</strong></td><td style='padding:4px 10px;'>${(req.RequestedNTE - (req.CurrentNTE ?? 0m)):F2}</td></tr>
                        <tr><td style='padding:4px 10px;'><strong>Required Approval</strong></td><td style='padding:4px 10px;'>{tierText}</td></tr>
                    </table>
                    <h3>Vendor Reason</h3>
                    <p>{reason}</p>
                    <div style='margin:20px 0;'>
                        <a href='{workOrderLink}' style='display:inline-block;padding:10px 22px;background:#2563eb;color:white;text-decoration:none;border-radius:6px;font-weight:bold;'>Review in SHOC</a>
                    </div>";

                await _emailSender.SendEmailAsync(dispatcherEmail, subject, body);
            }
            catch
            {
            }
        }

        private static bool IsAllowedVendorTransition(string? from, string? to)
        {
            if (from == "Acknowledged" && to == "In Progress") return true;
            if (from == "In Progress" && to == "Completed") return true;
            return false;
        }
    }
}