using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;

namespace SeaHaven.DataServices.Implementation
{
    public class WorkOrderDomainJobDataService : IWorkOrderDomainJobDataService
    {
        private static readonly LifecycleStatus?[] TerminalStatuses =
        {
            LifecycleStatus.Completed,
            LifecycleStatus.Canceled
        };

        private readonly ApplicationDbContext _context;

        public WorkOrderDomainJobDataService(ApplicationDbContext context)
        {
            _context = context;
        }

        public async Task<IReadOnlyList<int>> GetWeekRolledCandidatesAsync(
            DateOnly sourceWeekStart,
            DateOnly sourceWeekEnd,
            int batchSize = 500,
            CancellationToken cancellationToken = default)
        {
            var weekStartDate = sourceWeekStart.ToDateTime(TimeOnly.MinValue);
            var weekEndDate = sourceWeekEnd.ToDateTime(TimeOnly.MinValue);

            // Always return the first page of remaining unprocessed candidates.
            // Callers must not offset-page: ledger writes shrink this set after each batch.
            return await _context.workOrders
                .AsNoTracking()
                .Where(w => w.IsDeleted != true)
                .Where(w => w.istemplate != true)
                .Where(w => w.ScheduledDate != null)
                .Where(w =>
                    w.ScheduledDate!.Value.Date >= weekStartDate.Date
                    && w.ScheduledDate.Value.Date <= weekEndDate.Date)
                .Where(w => !TerminalStatuses.Contains(w.LifecycleStatus))
                .Where(w => !_context.WorkOrderWeekRolledLedgers.Any(l =>
                    l.WorkOrderId == w.Id && l.SourceWeekStart == sourceWeekStart))
                .OrderBy(w => w.Id)
                .Take(batchSize)
                .Select(w => w.Id)
                .ToListAsync(cancellationToken);
        }

        public async Task<WeekRolledProcessOutcome> TryProcessWeekRolledAsync(
            int workOrderId,
            DateOnly sourceWeekStart,
            string correlationId,
            CancellationToken cancellationToken = default)
        {
            await using var transaction = await _context.Database.BeginTransactionAsync(cancellationToken);

            var alreadyProcessed = await _context.WorkOrderWeekRolledLedgers
                .AnyAsync(l => l.WorkOrderId == workOrderId && l.SourceWeekStart == sourceWeekStart, cancellationToken);

            if (alreadyProcessed)
            {
                await transaction.RollbackAsync(cancellationToken);
                return new WeekRolledProcessOutcome { Skipped = true };
            }

            var workOrder = await _context.workOrders
                .FirstOrDefaultAsync(w => w.Id == workOrderId, cancellationToken);

            if (workOrder == null)
            {
                await transaction.RollbackAsync(cancellationToken);
                return new WeekRolledProcessOutcome { Skipped = true };
            }

            _context.WorkOrderWeekRolledLedgers.Add(new WorkOrderWeekRolledLedger
            {
                WorkOrderId = workOrderId,
                SourceWeekStart = sourceWeekStart,
                ProcessedAt = DateTime.UtcNow,
                CorrelationId = correlationId
            });

            var oldCarriedOver = workOrder.CarriedOver;
            workOrder.CarriedOver = oldCarriedOver + 1;

            try
            {
                await _context.SaveChangesAsync(cancellationToken);
                await transaction.CommitAsync(cancellationToken);
            }
            catch (DbUpdateException)
            {
                await transaction.RollbackAsync(cancellationToken);
                return new WeekRolledProcessOutcome { Skipped = true };
            }

            return new WeekRolledProcessOutcome
            {
                Processed = true,
                OldCarriedOver = oldCarriedOver,
                NewCarriedOver = workOrder.CarriedOver
            };
        }

        public async Task<PastDueRefreshResult> RefreshPastDueFlagsAsync(
            DateTime utcNow,
            int batchSize = 500,
            CancellationToken cancellationToken = default)
        {
            var today = utcNow.Date;
            var setCount = 0;
            var clearedCount = 0;
            var examinedCount = 0;
            var skip = 0;

            while (true)
            {
                var batch = await _context.workOrders
                    .Where(w => w.IsDeleted != true)
                    .Where(w => w.istemplate != true)
                    .Where(w => w.ScheduledDate != null)
                    .OrderBy(w => w.Id)
                    .Skip(skip)
                    .Take(batchSize)
                    .ToListAsync(cancellationToken);

                if (batch.Count == 0)
                    break;

                foreach (var workOrder in batch)
                {
                    examinedCount++;
                    var shouldBePastDue = workOrder.ScheduledDate!.Value.Date < today
                        && !TerminalStatuses.Contains(workOrder.LifecycleStatus);
                    var hasFlag = workOrder.OperationalFlags.HasFlag(OperationalFlags.PastDue);

                    if (shouldBePastDue && !hasFlag)
                    {
                        workOrder.OperationalFlags |= OperationalFlags.PastDue;
                        setCount++;
                    }
                    else if (!shouldBePastDue && hasFlag)
                    {
                        workOrder.OperationalFlags &= ~OperationalFlags.PastDue;
                        clearedCount++;
                    }
                }

                await _context.SaveChangesAsync(cancellationToken);
                skip += batchSize;

                if (batch.Count < batchSize)
                    break;
            }

            return new PastDueRefreshResult
            {
                SetCount = setCount,
                ClearedCount = clearedCount,
                ExaminedCount = examinedCount
            };
        }
    }
}