using System.Text.Json;
using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using FluentValidation;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Exceptions;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;
using SeaHaven.Services.Validation;

namespace SeaHaven.Services.Implementation
{
    public class WorkOrderBoardCreateService : IWorkOrderBoardCreateService
    {
        private readonly ApplicationDbContext _context;
        private readonly IWorkOrderBoardDataService _boardDataService;
        private readonly IWorkOrderBoardService _boardService;
        private readonly IWorkOrderAuditService _auditService;
        private readonly IWorkOrderBoardCreateValidation _validator;

        public WorkOrderBoardCreateService(
            ApplicationDbContext context,
            IWorkOrderBoardDataService boardDataService,
            IWorkOrderBoardService boardService,
            IWorkOrderAuditService auditService,
            IWorkOrderBoardCreateValidation validator)
        {
            _context = context;
            _boardDataService = boardDataService;
            _boardService = boardService;
            _auditService = auditService;
            _validator = validator;
        }

        public async Task<WorkOrderBoardRowDto> CreateAsync(WorkOrderBoardCreateRequestDto request, string? actorId)
        {
            var validationResult = await _validator.ValidateAsync(request);
            if (!validationResult.IsValid)
                throw new ValidationException(validationResult.Errors);

            var woNumber = await ResolveWoNumberAsync(request.WoNumber);
            var siteCode = request.SiteCode!.Trim();
            var primaryService = ResolvePrimaryService(request);
            var extraServicesJson = SerializeExtraServices(request.ExtraServices);
            var serviceNotes = TrimOrNull(request.ServiceNotes);
            var pocName = TrimOrNull(request.PocName);
            var pocPhone = TrimOrNull(request.PocPhone);
            var pocNotes = TrimOrNull(request.PocNotes);
            var techPhone = TrimOrNull(request.TechPhone);
            var vendorNotes = TrimOrNull(request.VendorNotes);
            var hasVendorDispatch = request.VendorId.HasValue
                || request.ApptDate.HasValue
                || !string.IsNullOrWhiteSpace(request.ApptTime);

            if (request.VendorId.HasValue && request.VendorId.Value > 0)
            {
                var vendorExists = await _context.Vendors.AnyAsync(v => v.Id == request.VendorId.Value && v.IsDeleted != true);
                if (!vendorExists)
                    throw new WorkOrderBoardValidationException("VendorNotFound", "vendorId does not exist.");
            }

            var workOrder = new WorkOrder
            {
                InternalWONumber = woNumber,
                WorkerOrderNumber = woNumber,
                WorkOrderType = request.WorkOrderType,
                SiteCode = siteCode,
                Description = string.IsNullOrWhiteSpace(request.Description) ? null : request.Description.Trim(),
                Trade = primaryService,
                ExtraServices = extraServicesJson,
                ServiceNotes = serviceNotes,
                PocName = pocName,
                PocPhone = pocPhone,
                PocNotes = pocNotes,
                LocationId = request.LocationId,
                DueDate = request.DueDate?.Date,
                AssignTo = string.IsNullOrWhiteSpace(request.AssignTo) ? null : request.AssignTo.Trim(),
                TargetWeek = request.TargetWeek,
                ScheduleWeekOnly = request.ScheduleWeekOnly,
                DocStatus = request.DocStatus,
                createdby = actorId,
                CreatedDate = DateTime.UtcNow,
                istemplate = false
            };

            if (!hasVendorDispatch)
            {
                workOrder.TechPhone = techPhone;
                workOrder.VendorNotes = vendorNotes;
            }

            WorkOrderBoardFieldMutations.SetInitialLifecycleStatus(workOrder);

            var changes = new List<WorkOrderBoardFieldMutations.BoardFieldChange>
            {
                WorkOrderBoardFieldMutations.BoardFieldChange.Changed("InternalWONumber", "", woNumber),
                WorkOrderBoardFieldMutations.BoardFieldChange.Changed("WorkOrderType", "", request.WorkOrderType.ToString()),
                WorkOrderBoardFieldMutations.BoardFieldChange.Changed("SiteCode", "", siteCode),
                WorkOrderBoardFieldMutations.BoardFieldChange.Changed("LifecycleStatus", "", LifecycleStatus.Incomplete.ToString())
            };

            if (workOrder.Description != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("Description", "", workOrder.Description));
            if (workOrder.Trade != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("Trade", "", workOrder.Trade));
            if (workOrder.ExtraServices != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("ExtraServices", "", workOrder.ExtraServices));
            if (workOrder.ServiceNotes != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("ServiceNotes", "", workOrder.ServiceNotes));
            if (workOrder.PocName != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("PocName", "", workOrder.PocName));
            if (workOrder.PocPhone != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("PocPhone", "", workOrder.PocPhone));
            if (workOrder.PocNotes != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("PocNotes", "", workOrder.PocNotes));
            if (workOrder.TechPhone != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("TechPhone", "", workOrder.TechPhone));
            if (workOrder.VendorNotes != null)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("VendorNotes", "", workOrder.VendorNotes));
            if (workOrder.LocationId.HasValue)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("LocationId", "", workOrder.LocationId.Value.ToString()));
            if (workOrder.DueDate.HasValue)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("DueDate", "", workOrder.DueDate.Value.ToString("yyyy-MM-dd")));
            if (workOrder.TargetWeek.HasValue)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("TargetWeek", "", workOrder.TargetWeek.Value.ToString("yyyy-MM-dd")));
            if (workOrder.ScheduleWeekOnly.HasValue)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("ScheduleWeekOnly", "", workOrder.ScheduleWeekOnly.Value.ToString()));
            if (workOrder.DocStatus.HasValue)
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("DocStatus", "", workOrder.DocStatus.Value.ToString()));

            if (!string.IsNullOrWhiteSpace(request.AssignTo))
                changes.AddRange(WorkOrderBoardFieldMutations.ApplyAssignTo(workOrder, request.AssignTo));
            else if (!string.IsNullOrWhiteSpace(workOrder.AssignTo))
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.AssignmentChanged("AssignTo", "", workOrder.AssignTo));

            if (request.ScheduledDate.HasValue)
                changes.AddRange(WorkOrderBoardFieldMutations.ApplyScheduledDate(workOrder, request.ScheduledDate.Value.Date));

            Dispatch? dispatch = null;
            if (hasVendorDispatch)
            {
                if (!request.VendorId.HasValue || request.VendorId.Value <= 0)
                    throw new WorkOrderBoardValidationException("DispatchRequired", "vendorId is required when setting appointment fields.");

                dispatch = new Dispatch
                {
                    VendorId = request.VendorId.Value,
                    Status = "Pending",
                    CreatedDate = DateTime.UtcNow,
                    ScheduledDate = request.ApptDate?.Date,
                    TechPhone = techPhone,
                    VendorNotes = vendorNotes
                };
                _context.Dispatches.Add(dispatch);
                workOrder.PrimaryDispatch = dispatch;
                changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("VendorId", "", request.VendorId.Value.ToString()));

                if (request.ApptDate.HasValue)
                    changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("ApptDate", "", request.ApptDate.Value.ToString("yyyy-MM-dd")));

                if (!string.IsNullOrWhiteSpace(request.ApptTime))
                {
                    var apptChange = WorkOrderBoardFieldMutations.ApplyApptTime(workOrder, dispatch, request.ApptTime);
                    if (apptChange.HasChanged)
                        changes.Add(apptChange);
                }

                if (techPhone != null)
                    changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("TechPhone", "", techPhone));
                if (vendorNotes != null)
                    changes.Add(WorkOrderBoardFieldMutations.BoardFieldChange.Changed("VendorNotes", "", vendorNotes));
            }

            _context.workOrders.Add(workOrder);
            await _context.SaveChangesAsync();

            if (dispatch != null && workOrder.PrimaryDispatchId == null)
            {
                workOrder.PrimaryDispatchId = dispatch.Id;
                dispatch.WorkOrderId = workOrder.Id;
            }

            _auditService.StageCreated(workOrder.Id, actorId, woNumber);
            StageChanges(workOrder.Id, changes, actorId, dispatch);

            if (request.PocContactId.HasValue)
            {
                _context.WorkOrderContacts.Add(new WorkOrderContacts
                {
                    WorkorderId = workOrder.Id,
                    ContactId = request.PocContactId,
                    Notes = pocNotes
                });
            }

            await _context.SaveChangesAsync();

            var row = await _boardService.GetBoardRowAsync(workOrder.Id);
            return row ?? throw new WorkOrderBoardValidationException("NotFound", "Work order was created but could not be loaded.");
        }

        private static string? ResolvePrimaryService(WorkOrderBoardCreateRequestDto request)
        {
            if (!string.IsNullOrWhiteSpace(request.PrimaryService))
                return request.PrimaryService.Trim();
            if (!string.IsNullOrWhiteSpace(request.Trade))
                return request.Trade.Trim();
            return null;
        }

        private static string? SerializeExtraServices(List<string>? extras)
        {
            if (extras == null || extras.Count == 0)
                return null;

            var normalized = new List<string>();
            var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (var item in extras)
            {
                if (string.IsNullOrWhiteSpace(item))
                    continue;
                var trimmed = item.Trim();
                if (trimmed.Length > 128)
                    throw new WorkOrderBoardValidationException(
                        "InvalidValue",
                        "Each extra service must be at most 128 characters.");
                if (!seen.Add(trimmed))
                    continue;
                normalized.Add(trimmed);
            }

            if (normalized.Count == 0)
                return null;

            var json = JsonSerializer.Serialize(normalized);
            if (json.Length > 2000)
                throw new WorkOrderBoardValidationException(
                    "InvalidValue",
                    "extraServices must serialize to at most 2000 characters.");

            return json;
        }

        private static string? TrimOrNull(string? value)
            => string.IsNullOrWhiteSpace(value) ? null : value.Trim();

        private async Task<string> ResolveWoNumberAsync(string? requested)
        {
            if (!string.IsNullOrWhiteSpace(requested))
            {
                if (!WorkOrderNumberNormalizer.TryNormalize(requested, out var normalized, out var error))
                    throw new WorkOrderBoardValidationException("InvalidWoNumber", error ?? "Invalid WO number.");

                if (await _boardDataService.InternalWoNumberExistsAsync(normalized, 0))
                    throw new WorkOrderBoardValidationException("DuplicateWoNumber", "WO number already exists.");

                return normalized;
            }

            for (var attempt = 0; attempt < 20; attempt++)
            {
                var candidate = await GenerateNextSequentialWoNumberAsync();
                if (!await _boardDataService.InternalWoNumberExistsAsync(candidate, 0))
                    return candidate;
            }

            throw new WorkOrderBoardValidationException("WoNumberGenerationFailed", "Could not generate a unique WO number.");
        }

        private async Task<string> GenerateNextSequentialWoNumberAsync()
        {
            var maxId = await _context.workOrders.MaxAsync(w => (int?)w.Id) ?? 0;
            var seed = Math.Max(maxId + 1, 1);
            if (!WorkOrderNumberNormalizer.TryNormalize(seed.ToString(), out var normalized, out _))
                normalized = seed.ToString().PadLeft(11, '0');
            return normalized;
        }

        private void StageChanges(
            int workOrderId,
            IEnumerable<WorkOrderBoardFieldMutations.BoardFieldChange> changes,
            string? actorId,
            Dispatch? dispatch)
        {
            foreach (var change in changes.Where(c => c.HasChanged))
            {
                var dispatchId = change.DispatchId ?? (dispatch?.Id > 0 ? dispatch.Id : null);
                switch (change.Action)
                {
                    case AuditActionType.StatusChanged:
                        _auditService.StageStatusChanged(workOrderId, change.OldValue, change.NewValue, actorId);
                        break;
                    case AuditActionType.AssignmentChanged:
                        _auditService.StageAssignmentChanged(workOrderId, change.OldValue, change.NewValue, actorId);
                        break;
                    default:
                        _auditService.StageFieldChanged(workOrderId, change.FieldName, change.OldValue ?? "", change.NewValue, actorId, dispatchId);
                        break;
                }
            }
        }
    }
}