using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Exceptions;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;

namespace SeaHaven.Services.Implementation
{
    public class WorkOrderBoardUpdateService : IWorkOrderBoardUpdateService
    {
        private readonly ApplicationDbContext _context;
        private readonly IWorkOrderBoardDataService _boardDataService;
        private readonly IWorkOrderAuditService _auditService;

        public WorkOrderBoardUpdateService(
            ApplicationDbContext context,
            IWorkOrderBoardDataService boardDataService,
            IWorkOrderAuditService auditService)
        {
            _context = context;
            _boardDataService = boardDataService;
            _auditService = auditService;
        }

        public async Task<WorkOrderBoardRowDto> PatchFieldAsync(
            int workOrderId,
            WorkOrderBoardPatchRequestDto request,
            string? actorId)
        {
            if (string.IsNullOrWhiteSpace(request.Field))
                throw new WorkOrderBoardValidationException("InvalidField", "Field is required.");

            var field = request.Field.Trim();
            var canonicalField = WorkOrderBoardFieldNames.Canonicalize(field);
            if (canonicalField == null)
                throw new WorkOrderBoardValidationException("InvalidField", $"Field '{field}' is not editable.");

            var workOrderVersion = ParseRowVersion(request.WorkOrderVersion, "workOrderVersion");
            if (workOrderVersion == null)
                throw new WorkOrderBoardValidationException("WorkOrderVersionRequired", "workOrderVersion is required.");

            var dispatchVersion = ParseRowVersion(request.DispatchVersion, "dispatchVersion");

            var workOrder = await _context.workOrders
                .FirstOrDefaultAsync(w => w.Id == workOrderId && w.istemplate != true && (w.IsDeleted != true || w.IsDeleted == null));

            if (workOrder == null)
                throw new WorkOrderBoardValidationException("NotFound", "Work order not found.");

            if (!RowVersionsMatch(workOrder.RowVersion, workOrderVersion))
            {
                var staleState = await LoadBoardRowAsync(workOrderId);
                throw new WorkOrderBoardConcurrencyException(staleState);
            }

            if (WorkOrderBoardMutationRules.IsReadOnly(workOrder.LifecycleStatus))
                throw new WorkOrderBoardValidationException("CanceledReadOnly", "Work order is read-only in its current status.");

            var isPastDue = WorkOrderDerivedFields.IsPastDue(workOrder.ScheduledDate, workOrder.LifecycleStatus);
            if (WorkOrderBoardMutationRules.ShouldBlockStatusChangeWhenPastDue(canonicalField, isPastDue))
                throw new WorkOrderBoardValidationException("PastDueStatusBlocked", "Status cannot be changed while work order is past due. Reschedule first.");

            _context.Entry(workOrder).Property(w => w.RowVersion).OriginalValue = workOrderVersion;

            Dispatch? dispatch = null;
            if (WorkOrderBoardFieldNames.IsDispatchField(canonicalField))
            {
                var vendorIdHint = canonicalField.Equals(WorkOrderBoardFieldNames.VendorId, StringComparison.OrdinalIgnoreCase)
                    ? ParseVendorIdHint(request.Value)
                    : null;

                var hadPrimaryDispatch = workOrder.PrimaryDispatchId.HasValue;
                dispatch = await ResolveDispatchAsync(workOrder, request.PrimaryDispatchId, vendorIdHint);

                if (dispatchVersion != null && !RowVersionsMatch(dispatch.RowVersion, dispatchVersion))
                {
                    var staleState = await LoadBoardRowAsync(workOrderId);
                    throw new WorkOrderBoardConcurrencyException(staleState);
                }

                if (dispatchVersion != null)
                    _context.Entry(dispatch).Property(d => d.RowVersion).OriginalValue = dispatchVersion;
                else if (hadPrimaryDispatch && dispatch.RowVersion != null)
                    throw new WorkOrderBoardValidationException("DispatchVersionRequired", "dispatchVersion is required for dispatch fields.");
            }

            var auditField = WorkOrderBoardFieldNames.ToAuditFieldName(canonicalField);
            var changes = await ApplyFieldMutationAsync(canonicalField, workOrder, dispatch, request.Value, auditField);
            changes = changes.Where(c => c.HasChanged).ToList();

            if (changes.Count == 0 && !_context.ChangeTracker.HasChanges())
            {
                var unchanged = await LoadBoardRowAsync(workOrderId);
                return unchanged ?? throw new WorkOrderBoardValidationException("NotFound", "Work order not found.");
            }

            if (changes.Count == 0)
            {
                await _context.SaveChangesAsync();
                var persisted = await LoadBoardRowAsync(workOrderId);
                return persisted ?? throw new WorkOrderBoardValidationException("NotFound", "Work order not found.");
            }

            foreach (var change in changes)
            {
                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, change.DispatchId);
                        break;
                }
            }

            try
            {
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                _context.ChangeTracker.Clear();
                var currentState = await LoadBoardRowAsync(workOrderId);
                throw new WorkOrderBoardConcurrencyException(currentState);
            }

            var row = await LoadBoardRowAsync(workOrderId);
            return row ?? throw new WorkOrderBoardValidationException("NotFound", "Work order not found.");
        }

        private async Task<List<FieldChange>> ApplyFieldMutationAsync(
            string field,
            WorkOrder workOrder,
            Dispatch? dispatch,
            string? value,
            string auditField)
        {
            return field switch
            {
                WorkOrderBoardFieldNames.WoNumber => new List<FieldChange> { await ApplyWoNumber(workOrder, value, auditField) },
                WorkOrderBoardFieldNames.WorkOrderType => new List<FieldChange> { ApplyWorkOrderType(workOrder, value, auditField) },
                WorkOrderBoardFieldNames.SiteCode => new List<FieldChange> { ApplyStringField(value, auditField, v => workOrder.SiteCode = v, () => workOrder.SiteCode) },
                WorkOrderBoardFieldNames.LifecycleStatus => new List<FieldChange> { ApplyLifecycleStatus(workOrder, value, auditField) },
                WorkOrderBoardFieldNames.AssignTo => ApplyAssignTo(workOrder, value, auditField),
                WorkOrderBoardFieldNames.DueDate => new List<FieldChange> { ApplyDateField(value, auditField, v => workOrder.DueDate = v, () => workOrder.DueDate) },
                WorkOrderBoardFieldNames.ScheduledDate => ApplyScheduledDate(workOrder, value, auditField),
                WorkOrderBoardFieldNames.TargetWeek => new List<FieldChange> { ApplyTargetWeek(workOrder, value, auditField) },
                WorkOrderBoardFieldNames.ScheduleWeekOnly => new List<FieldChange> { ApplyBoolField(value, auditField, v => workOrder.ScheduleWeekOnly = v, () => workOrder.ScheduleWeekOnly) },
                WorkOrderBoardFieldNames.VendorId => new List<FieldChange> { ApplyVendorId(dispatch!, value, auditField) },
                WorkOrderBoardFieldNames.ApptDate => new List<FieldChange> { ApplyApptDate(dispatch!, value, auditField) },
                WorkOrderBoardFieldNames.ApptTime => new List<FieldChange> { ApplyApptTime(workOrder, dispatch!, value, auditField) },
                WorkOrderBoardFieldNames.DocStatus => new List<FieldChange> { ApplyDocStatus(workOrder, value, auditField) },
                _ => throw new WorkOrderBoardValidationException("InvalidField", $"Field '{field}' is not editable.")
            };
        }

        private async Task<Dispatch> ResolveDispatchAsync(WorkOrder workOrder, int? primaryDispatchId, int? vendorIdForCreate)
        {
            if (primaryDispatchId.HasValue)
            {
                var dispatch = await _context.Dispatches
                    .FirstOrDefaultAsync(d => d.Id == primaryDispatchId.Value && d.WorkOrderId == workOrder.Id);

                if (dispatch == null)
                    throw new WorkOrderBoardValidationException("InvalidDispatch", "Primary dispatch does not belong to this work order.");

                workOrder.PrimaryDispatchId = dispatch.Id;
                return dispatch;
            }

            if (workOrder.PrimaryDispatchId.HasValue)
            {
                var existing = await _context.Dispatches
                    .FirstOrDefaultAsync(d => d.Id == workOrder.PrimaryDispatchId.Value);

                if (existing != null)
                    return existing;
            }

            if (!vendorIdForCreate.HasValue || vendorIdForCreate.Value <= 0)
                throw new WorkOrderBoardValidationException("DispatchRequired", "A primary dispatch is required. Set vendorId first or provide primaryDispatchId.");

            var created = new Dispatch
            {
                WorkOrderId = workOrder.Id,
                VendorId = vendorIdForCreate.Value,
                Status = "Pending",
                CreatedDate = DateTime.UtcNow
            };
            _context.Dispatches.Add(created);
            await _context.SaveChangesAsync();
            workOrder.PrimaryDispatchId = created.Id;
            return created;
        }

        private async Task<FieldChange> ApplyWoNumber(WorkOrder workOrder, string? value, string auditField)
        {
            if (!WorkOrderNumberNormalizer.TryNormalize(value, out var normalized, out var error))
                throw new WorkOrderBoardValidationException("InvalidWoNumber", error ?? "Invalid WO number.");

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

            var old = workOrder.InternalWONumber;
            if (old == normalized)
                return FieldChange.Unchanged(auditField);

            workOrder.InternalWONumber = normalized;
            workOrder.WorkerOrderNumber = normalized;
            return FieldChange.ForField(auditField, old, normalized);
        }

        private static FieldChange ApplyWorkOrderType(WorkOrder workOrder, string? value, string auditField)
        {
            if (string.IsNullOrWhiteSpace(value))
                throw new WorkOrderBoardValidationException("InvalidValue", "workOrderType value is required.");

            if (!Enum.TryParse<WorkOrderType>(value, true, out var parsed))
                throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid workOrderType: {value}");

            var old = workOrder.WorkOrderType?.ToString();
            if (workOrder.WorkOrderType == parsed)
                return FieldChange.Unchanged(auditField);

            workOrder.WorkOrderType = parsed;
            return FieldChange.ForField(auditField, old, parsed.ToString());
        }

        private static FieldChange ApplyStringField(
            string? value,
            string auditField,
            Action<string?> setter,
            Func<string?> getter)
        {
            var normalized = string.IsNullOrWhiteSpace(value) ? null : value.Trim();
            var old = getter();
            if (old == normalized)
                return FieldChange.Unchanged(auditField);

            setter(normalized);
            return FieldChange.ForField(auditField, old, normalized);
        }

        private static FieldChange ApplyLifecycleStatus(WorkOrder workOrder, string? value, string auditField)
        {
            var parsed = LifecycleStatusMapper.ParseLifecycleStatus(value);
            if (parsed == null)
                throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid lifecycleStatus: {value}");

            var old = workOrder.LifecycleStatus?.ToString() ?? workOrder.Status;
            if (workOrder.LifecycleStatus == parsed)
                return FieldChange.Unchanged(auditField);

            workOrder.LifecycleStatus = parsed;
            workOrder.Status = WorkOrderDerivedFields.GetLifecycleStatusLabel(parsed);
            if (workOrder.LegacyStatus == null && workOrder.Status != null)
                workOrder.LegacyStatus = workOrder.Status;

            return FieldChange.StatusChanged(auditField, old, parsed.ToString());
        }

        private static List<FieldChange> ApplyAssignTo(WorkOrder workOrder, string? value, string auditField)
        {
            var normalized = string.IsNullOrWhiteSpace(value) ? null : value.Trim();
            var old = workOrder.AssignTo;
            var changes = new List<FieldChange>();

            if (old != normalized)
            {
                workOrder.AssignTo = normalized;
                changes.Add(FieldChange.AssignmentChanged(auditField, old, normalized));
            }

            changes.AddRange(ApplyAutoScheduleSideEffects(workOrder));
            return changes;
        }

        private static FieldChange ApplyDateField(
            string? value,
            string auditField,
            Action<DateTime?> setter,
            Func<DateTime?> getter)
        {
            DateTime? parsed = null;
            if (!string.IsNullOrWhiteSpace(value))
            {
                if (!DateTime.TryParse(value, out var dt))
                    throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid date for {auditField}: {value}");
                parsed = dt.Date;
            }

            var old = FormatDate(getter());
            var newVal = FormatDate(parsed);
            if (old == newVal)
                return FieldChange.Unchanged(auditField);

            setter(parsed);
            return FieldChange.ForField(auditField, old, newVal);
        }

        private static List<FieldChange> ApplyScheduledDate(WorkOrder workOrder, string? value, string auditField)
        {
            var previousDate = workOrder.ScheduledDate;
            DateTime? parsed = null;
            if (!string.IsNullOrWhiteSpace(value))
            {
                if (!DateTime.TryParse(value, out var dt))
                    throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid scheduledDate: {value}");
                parsed = dt.Date;
            }

            var changes = new List<FieldChange>();
            var oldFormatted = FormatDate(previousDate);
            var newFormatted = FormatDate(parsed);

            if (oldFormatted != newFormatted)
            {
                workOrder.ScheduledDate = parsed;
                changes.Add(FieldChange.ForField(auditField, oldFormatted, newFormatted));

                if (!workOrder.OriginalDate.HasValue && parsed.HasValue)
                {
                    workOrder.OriginalDate = DateOnly.FromDateTime(parsed.Value);
                    var originalWeek = WorkOrderBoardMutationRules.ComputeOriginalWeek(parsed);
                    if (originalWeek.HasValue)
                        workOrder.OriginalWeek = originalWeek;
                }

                if (WorkOrderBoardMutationRules.IsReschedule(previousDate, parsed))
                {
                    var oldCount = workOrder.RescheduleCount.ToString();
                    workOrder.RescheduleCount++;
                    changes.Add(FieldChange.ForField(WorkOrderBoardFieldNames.RescheduleCount, oldCount, workOrder.RescheduleCount.ToString()));
                }
            }

            changes.AddRange(ApplyAutoScheduleSideEffects(workOrder));
            return changes;
        }

        private static FieldChange ApplyTargetWeek(WorkOrder workOrder, string? value, string auditField)
        {
            DateOnly? parsed = null;
            if (!string.IsNullOrWhiteSpace(value))
            {
                if (!DateOnly.TryParse(value, out var d))
                    throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid targetWeek: {value}");
                parsed = d;
            }

            var old = workOrder.TargetWeek?.ToString("yyyy-MM-dd");
            var newVal = parsed?.ToString("yyyy-MM-dd");
            if (old == newVal)
                return FieldChange.Unchanged(auditField);

            workOrder.TargetWeek = parsed;
            return FieldChange.ForField(auditField, old, newVal);
        }

        private static FieldChange ApplyBoolField(
            string? value,
            string auditField,
            Action<bool?> setter,
            Func<bool?> getter)
        {
            if (string.IsNullOrWhiteSpace(value))
                throw new WorkOrderBoardValidationException("InvalidValue", $"{auditField} value is required.");

            if (!bool.TryParse(value, out var parsed))
                throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid boolean for {auditField}: {value}");

            var old = getter()?.ToString();
            if (getter() == parsed)
                return FieldChange.Unchanged(auditField);

            setter(parsed);
            return FieldChange.ForField(auditField, old, parsed.ToString());
        }

        private static FieldChange ApplyVendorId(Dispatch dispatch, string? value, string auditField)
        {
            var vendorId = ParseVendorIdHint(value);
            if (!vendorId.HasValue)
                throw new WorkOrderBoardValidationException("InvalidValue", "vendorId must be a positive integer.");

            var old = dispatch.VendorId.ToString();
            if (dispatch.VendorId == vendorId.Value)
                return FieldChange.Unchanged(auditField, dispatch.Id);

            dispatch.VendorId = vendorId.Value;
            return FieldChange.ForField(auditField, old, vendorId.Value.ToString(), dispatch.Id);
        }

        private static FieldChange ApplyApptDate(Dispatch dispatch, string? value, string auditField)
        {
            DateTime? parsed = null;
            if (!string.IsNullOrWhiteSpace(value))
            {
                if (!DateTime.TryParse(value, out var dt))
                    throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid apptDate: {value}");
                parsed = dt.Date;
            }

            var old = FormatDate(dispatch.ScheduledDate);
            var newVal = FormatDate(parsed);
            if (old == newVal)
                return FieldChange.Unchanged(auditField, dispatch.Id);

            dispatch.ScheduledDate = parsed;
            return FieldChange.ForField(auditField, old, newVal, dispatch.Id);
        }

        private static FieldChange ApplyApptTime(WorkOrder workOrder, Dispatch dispatch, string? value, string auditField)
        {
            if (!WorkOrderBoardApptTimeParser.TryParse(value, out var start, out var end, out var error))
                throw new WorkOrderBoardValidationException("InvalidValue", error ?? "Invalid apptTime.");

            var apptDate = dispatch.ScheduledDate ?? workOrder.ScheduledDate;
            var oldStart = FormatDateTime(workOrder.ScheduledStart);
            var oldEnd = FormatDateTime(workOrder.ScheduledEnd);

            workOrder.ScheduledStart = WorkOrderBoardApptTimeParser.CombineDateAndTime(apptDate, start);
            workOrder.ScheduledEnd = WorkOrderBoardApptTimeParser.CombineDateAndTime(apptDate, end);

            var newStart = FormatDateTime(workOrder.ScheduledStart);
            var newEnd = FormatDateTime(workOrder.ScheduledEnd);
            var oldCombined = FormatApptRange(oldStart, oldEnd);
            var newCombined = FormatApptRange(newStart, newEnd);

            if (oldCombined == newCombined)
                return FieldChange.Unchanged(auditField, dispatch.Id);

            return FieldChange.ForField(auditField, oldCombined, newCombined, dispatch.Id);
        }

        private static FieldChange ApplyDocStatus(WorkOrder workOrder, string? value, string auditField)
        {
            if (string.IsNullOrWhiteSpace(value))
                throw new WorkOrderBoardValidationException("InvalidValue", "docStatus value is required.");

            if (!Enum.TryParse<DocStatus>(value, true, out var parsed))
                throw new WorkOrderBoardValidationException("InvalidValue", $"Invalid docStatus: {value}");

            var old = workOrder.DocStatus?.ToString();
            if (workOrder.DocStatus == parsed)
                return FieldChange.Unchanged(auditField);

            workOrder.DocStatus = parsed;
            return FieldChange.ForField(auditField, old, parsed.ToString());
        }

        private static List<FieldChange> ApplyAutoScheduleSideEffects(WorkOrder workOrder)
        {
            var changes = new List<FieldChange>();
            if (!WorkOrderBoardMutationRules.ShouldAutoSchedule(workOrder.LifecycleStatus, workOrder.ScheduledDate, workOrder.AssignTo))
                return changes;

            var old = workOrder.LifecycleStatus?.ToString();
            workOrder.LifecycleStatus = LifecycleStatus.Scheduled;
            workOrder.Status = WorkOrderDerivedFields.GetLifecycleStatusLabel(LifecycleStatus.Scheduled);
            changes.Add(FieldChange.StatusChanged("LifecycleStatus", old, LifecycleStatus.Scheduled.ToString()));
            return changes;
        }

        private static bool RowVersionsMatch(byte[]? current, byte[] expected)
            => current != null && current.AsSpan().SequenceEqual(expected);

        private async Task<WorkOrderBoardRowDto?> LoadBoardRowAsync(int workOrderId)
        {
            var raw = await _boardDataService.GetBoardRowByIdAsync(workOrderId);
            return raw == null ? null : WorkOrderBoardService.MapRawRow(raw, DateTime.UtcNow);
        }

        private static byte[]? ParseRowVersion(string? base64, string fieldName)
        {
            if (string.IsNullOrWhiteSpace(base64))
                return null;

            try
            {
                return Convert.FromBase64String(base64);
            }
            catch (FormatException)
            {
                throw new WorkOrderBoardValidationException("InvalidRowVersion", $"Invalid {fieldName} format.");
            }
        }

        private static int? ParseVendorIdHint(string? value)
        {
            if (string.IsNullOrWhiteSpace(value) || !int.TryParse(value, out var vendorId) || vendorId <= 0)
                return null;
            return vendorId;
        }

        private static string? FormatDate(DateTime? value) => value?.ToString("yyyy-MM-dd");
        private static string? FormatDateTime(DateTime? value) => value?.ToString("O");
        private static string? FormatApptRange(string? start, string? end)
            => start == null && end == null ? null : $"{start}|{end}";

        private sealed record FieldChange(
            string FieldName,
            string? OldValue,
            string? NewValue,
            AuditActionType Action,
            int? DispatchId,
            bool HasChanged)
        {
            public static FieldChange Unchanged(string fieldName, int? dispatchId = null)
                => new(fieldName, null, null, AuditActionType.FieldChanged, dispatchId, false);

            public static FieldChange ForField(string fieldName, string? oldValue, string? newValue, int? dispatchId = null)
                => new(fieldName, oldValue, newValue, AuditActionType.FieldChanged, dispatchId, true);

            public static FieldChange StatusChanged(string fieldName, string? oldValue, string? newValue)
                => new(fieldName, oldValue, newValue, AuditActionType.StatusChanged, null, true);

            public static FieldChange AssignmentChanged(string fieldName, string? oldValue, string? newValue)
                => new(fieldName, oldValue, newValue, AuditActionType.AssignmentChanged, null, true);
        }
    }
}