using System;
using Comal.Classes;
using Comal.Stores;
using InABox.Core;
using InABox.Database;
using System.Collections.Generic;
using System.Linq;

namespace PRSStores;

public enum JobRequisitionItemAction
{
    Created,
    Updated,
    Deleted,
    None
}

public class JobRequisitionItemStore : BaseStore<JobRequisitionItem>
{
    protected override void BeforeSave(JobRequisitionItem item)
    {
        if (item.ID != Guid.Empty)
        {
            if (CalculateStatus(this, item))
                item.Notes += $"{(!String.IsNullOrWhiteSpace(item.Notes) ? "\n" : "")}Status updated to {item.Status.ToString().SplitCamelCase()} because the record was changed";      
        }
        base.BeforeSave(item);
    }

    protected override void AfterSave(JobRequisitionItem entity)
    {
        base.AfterSave(entity);

        if(entity.HasOriginalValue(x => x.Cancelled))
        {
            CancelMovements(entity);
        }
    }

    private static IEnumerable<StockMovement> GetMovements(IStore store, Guid jriID, Filter<StockMovement>? filter, Columns<StockMovement> columns)
    {
        return store.Provider
            .Query(
                Filter<StockMovement>.And(
                    new Filter<StockMovement>(x => x.JobRequisitionItem.ID).IsEqualTo(jriID),
                    filter),
                columns)
                .ToObjects<StockMovement>();
    }
    private static IEnumerable<StockMovement> GetNotIssued(IStore store, Guid jriID, Columns<StockMovement> columns)
    {
        return GetMovements(store, jriID, new Filter<StockMovement>(x => x.Type).IsNotEqualTo(StockMovementType.Issue), columns);
    }
    private static IEnumerable<StockMovement> GetIssued(IStore store, Guid jriID, Columns<StockMovement> columns)
    {
        return GetMovements(store, jriID, new Filter<StockMovement>(x => x.Type).IsEqualTo(StockMovementType.Issue), columns);
    }

    private void CancelMovements(JobRequisitionItem entity)
    {
        // Here, we care about *all* movements into or out of this requi. If stuff has been issued, it must be included,
        // since we cannot return issued stock back to general stock for the job.
        var movements = GetMovements(this, entity.ID, null,
            new Columns<StockMovement>(
                x => x.Product.ID,
                x => x.Style.ID,
                x => x.Job.ID,
                x => x.Location.ID,
                x => x.Units,
                x => x.Cost,
                x => x.OrderItem.ID)
            .AddDimensionsColumns(x => x.Dimensions, Dimensions.ColumnsType.Local));

        var newMovements = new List<StockMovement>();
        foreach(var movement in movements)
        {
            var from = movement.CreateMovement();
            from.Date = entity.Cancelled;
            from.Cost = movement.Cost;
            from.System = true;
            from.JobRequisitionItem.ID = entity.ID;
            from.OrderItem.ID = movement.OrderItem.ID;
            from.Notes = "Requisition item cancelled";

            var to = movement.CreateMovement();
            to.Date = entity.Cancelled;
            to.Cost = movement.Cost;
            to.System = true;
            to.Notes = "Requisition item cancelled";
            to.OrderItem.ID = movement.OrderItem.ID;
            to.Transaction = from.Transaction;

            if(movement.Units > 0)
            {
                // If this movement was an increase to reservation allocation, we create a transfer out of the reservation.
                from.Issued = movement.Units;
                to.Received = movement.Units;

                from.Type = StockMovementType.TransferOut;
                to.Type = StockMovementType.TransferIn;
            }
            else if(movement.Units < 0)
            {
                // If this movement was a decrease to reservation allocation, we create a transfer into the reservation.
                from.Received = -movement.Units;
                to.Issued = -movement.Units;

                from.Type = StockMovementType.TransferIn;
                to.Type = StockMovementType.TransferOut;
            }

            newMovements.Add(from);
            newMovements.Add(to);
        }

        if(newMovements.Count > 0)
        {
            var batch = new StockMovementBatch
            {
                Notes = "Requisition item cancelled."
            };
            FindSubStore<StockMovementBatch>().Save(batch, "");

            foreach(var mvt in newMovements)
            {
                mvt.Batch.ID = batch.ID;
            }

            FindSubStore<StockMovement>().Save(newMovements, "Requisition item cancelled.");
        }
    }

    public static Columns<JobRequisitionItem> StatusRequiredColumns()
    {
        return new Columns<JobRequisitionItem>(
            x => x.ID,
            x => x.Archived,
            x => x.Cancelled,
            x => x.OrderRequired,
            x => x.Status,
            x => x.Style.ID,
            x => x.Product.ID,
            x => x.Qty,
            x => x.Dimensions.Value,
            x => x.Notes);
    }

    /// <summary>
    /// Ensure that the columns of <paramref name="item"/> match <see cref="StatusRequiredColumns"/>.
    /// </summary>
    /// <param name="store"></param>
    /// <param name="item"></param>
    /// <returns></returns>
    public static bool CalculateStatus(IStore store, JobRequisitionItem item)
    {
        if (item.Archived != DateTime.MinValue)
            item.Status = JobRequisitionItemStatus.Archived;
        else if (item.Cancelled != DateTime.MinValue)
            item.Status = JobRequisitionItemStatus.Cancelled;
        else
        {
            // We don't care about that which has been issued, because we're just looking at how much was allocated.
            // If we cared about the issued movements as well, then after issuing a requi item, it would become unallocated.
            // However, we do include transfers out of this requi, since then the stuff ain't actually been allocated.
            var stockMovements = GetNotIssued(store, item.ID,
                new Columns<StockMovement>(x => x.Units)
                    .Add(x => x.Style.ID)
                    .Add(x=>x.Dimensions.Value));
            var styleTotal = 0.0;
            var total = 0.0;
            foreach (var mvt in stockMovements)
            {
                if (mvt.Style.ID == item.Style.ID)
                {
                    styleTotal += mvt.Units * mvt.Dimensions.Value;
                }
                total += mvt.Units;
            }

            var remStyle = (item.Qty * item.Dimensions.Value) - styleTotal;
            var remTotal = (item.Qty * item.Dimensions.Value) - total;

            if (remStyle <= 0)
            {
                // Now, we care about what's actually been issued.
                var issued = GetIssued(store, item.ID, new Columns<StockMovement>(x => x.Units).Add(x=>x.Dimensions.Value));

                // If everything has been issued, the issued total will be a negative value to balance the Qty.
                if(item.Qty + issued.Sum(x => x.Units * x.Dimensions.Value) <= 0)
                {
                    item.Status = JobRequisitionItemStatus.Issued;
                }
                else
                {
                    item.Status = JobRequisitionItemStatus.Allocated;
                }
            }
            else if (remTotal <= 0)
            {
                // Find all unreceived POItems for this guy that are treatments (i.e., wrong product ID).
                var jriPois = store.Provider.Query(
                    new Filter<JobRequisitionItemPurchaseOrderItem>(x => x.JobRequisitionItem.ID).IsEqualTo(item.ID)
                        .And(x => x.PurchaseOrderItem.ReceivedDate).IsEqualTo(DateTime.MinValue)
                        .And(x => x.PurchaseOrderItem.Product.ID).IsNotEqualTo(item.Product.ID),
                    new Columns<JobRequisitionItemPurchaseOrderItem>(x => x.ID));
                if (jriPois.Rows.Count > 0)
                    item.Status = JobRequisitionItemStatus.TreatmentOnOrder;
                else
                    item.Status = JobRequisitionItemStatus.TreatmentRequired;
            }
            else
            {
                // Find all unreceived POItems for this guy.
                var jriPois = store.Provider.Query(
                    new Filter<JobRequisitionItemPurchaseOrderItem>(x => x.JobRequisitionItem.ID).IsEqualTo(item.ID)
                        .And(x => x.PurchaseOrderItem.ReceivedDate).IsEqualTo(DateTime.MinValue),
                    new Columns<JobRequisitionItemPurchaseOrderItem>(x => x.PurchaseOrderItem.Product.ID)
                        .Add(x => x.PurchaseOrderItem.Qty)
                        .Add(x=>x.PurchaseOrderItem.Dimensions.Value))
                    .ToObjects<JobRequisitionItemPurchaseOrderItem>()
                    .ToList();
                var stockOrders = jriPois.Where(x => x.PurchaseOrderItem.Product.ID == item.Product.ID).ToList();
                var treatmentOrders = jriPois.Where(x => x.PurchaseOrderItem.Product.ID != item.Product.ID).ToList();

                remTotal -= stockOrders.Sum(x => x.PurchaseOrderItem.Qty * x.PurchaseOrderItem.Dimensions.Value);
                if (remTotal <= 0)
                {
                    if (stockOrders.Count > 0)
                        item.Status = JobRequisitionItemStatus.OnOrder;
                    else
                    {
                        // This should be impossible to reach. We are at this point because remTotal <= 0, but stockOrders was an empty list. Therefore
                        // remTotal is was <= 0 before checking PurchaseOrderItems, but then we should be TreatmentRequired, as above.
                        Logger.Send(LogType.Error, store.UserID, $"Internal assertion failed: there is enough stock, but we didn't reach the correct clause.");

                        if (treatmentOrders.Count > 0)
                            item.Status = JobRequisitionItemStatus.TreatmentOnOrder;
                        else
                            item.Status = JobRequisitionItemStatus.TreatmentRequired;
                    }
                }
                else if (item.OrderRequired != DateTime.MinValue)
                    item.Status = JobRequisitionItemStatus.OrderRequired; 
                else
                {
                    // Even after all the orders have come through, we still don't have enough. We must order more.
                    item.Status = JobRequisitionItemStatus.NotChecked;
                }
            }
        }
        return item.HasOriginalValue(x => x.Status);
    }

    public static bool CalculateStatus(IStore store, Guid jobRequiItemID)
    {
        var item = store.Provider.Query(
            new Filter<JobRequisitionItem>(x => x.ID).IsEqualTo(jobRequiItemID),
            StatusRequiredColumns())
            .ToObjects<JobRequisitionItem>()
            .FirstOrDefault();
        if(item is null)
        {
            Logger.Send(LogType.Error, store.UserID, $"No {nameof(JobRequisitionItem)} with ID {jobRequiItemID}");
            return false;
        }
        return CalculateStatus(store, item);
    }
    
    public static void UpdateStatus(IStore store, Guid jobRequiItemID, JobRequisitionItemAction action)
    {
        Logger.Send(LogType.Information, "", " ** Updating Requisition Item Status ({0}) -> {1}",
            store.GetType().EntityName(), jobRequiItemID);
        var item = store.Provider.Query(
                new Filter<JobRequisitionItem>(x => x.ID).IsEqualTo(jobRequiItemID),
                StatusRequiredColumns())
            .ToObjects<JobRequisitionItem>()
            .FirstOrDefault();
        if (item is null)
        {
            Logger.Send(LogType.Error, store.UserID, $"No {nameof(JobRequisitionItem)} with ID {jobRequiItemID}");
        }
        else
        {
            if (CalculateStatus(store, item))
            {
                if (action != JobRequisitionItemAction.None)
                    item.Notes += $"{(!String.IsNullOrWhiteSpace(item.Notes) ? "\n" : "")}Status updated to {item.Status.ToString().SplitCamelCase()} because a {store.Type.EntityName().Split('.').Last().SplitCamelCase()} was {action.ToString().ToLower()}";
                store.Provider.Save(item);
            }
        }
    }
}