using System;
using System.Collections.Generic;
using System.Configuration;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using HeuristicLab.Services.Optimization.Billing.Business;
using HeuristicLab.Services.Optimization.Billing.Interfaces;
using HeuristicLab.Services.Optimization.Billing.Model;
namespace HeuristicLab.Services.Optimization.Billing.BillingEngine {
  public class BillingEngine {
    private bool stop;
    private AutoResetEvent waitHandle;
    private TimeSpan interval;
    private DateTime currentDate;

    private IOptimizationBilling billingService;
    public IOptimizationBilling BillingService {
      get {
        if (billingService == null) {
          billingService = new BillingService();
        }
        return billingService;
      }
      set { billingService = value; }
    }

    private IInvoiceFormattingEngine invoiceFormattingEngine;
    public IInvoiceFormattingEngine InvoiceFormattingEngine {
      get {
        if (invoiceFormattingEngine == null) {
          invoiceFormattingEngine = new PlainTextInvoiceFormattingEngine();
        }
        return invoiceFormattingEngine;
      }
      set { invoiceFormattingEngine = value; }
    }

    public BillingEngine() {
      stop = false;
      interval = TimeSpan.Parse(ConfigurationManager.AppSettings["BillingEngineInterval"]);
      waitHandle = new AutoResetEvent(true);
    }

    public void StopBillingEngine() {
      stop = true;
      waitHandle.Set();
    }

    public void Run() {
      while (!stop) {
        try {
          Trace.WriteLine("[BillingEngine] Start billing cycle");
          currentDate = DateTime.Now.Date;
          Trace.WriteLine(string.Format("[BillingEngine] Current date: {0}", currentDate));
          IList<Order> activeOrders = BillingService.GetOrdersByState(OrderState.Active);
          Trace.WriteLine(string.Format("[BillingEngine] Processing {0} active orders.", activeOrders.Count));
          foreach (Order order in activeOrders) {
            if (!order.NextBillableDay.HasValue) {
              // An invoice has never been generated from this order 
              order.NextBillableDay = currentDate;
              order.EntityState = State.Modified;
            }

            if (order.NextBillableDay >= currentDate) {
              // TODO: Embed everything in a transaction

              // Collect Usage Data
              //IList<UsageRecord> usageRecrods = BillingService.GetUsageRecords(order.User.Name, order.LastBillableDay.Value, currentDate);

              // Collect Invoice Data
              Invoice invoice = new Invoice();
              invoice.Order = order;
              invoice.User = order.User;
              invoice.Due = currentDate.AddMonths(1);
              invoice.InvoiceDate = currentDate;
              invoice.Status = InvoiceStatus.Open;
              invoice.InvoiceLines = new List<InvoiceLine>();
              foreach (OrderLine orderLine in order.OrderLines) {
                InvoiceLine invoiceLine = new InvoiceLine();
                invoiceLine.Invoice = invoice;
                invoiceLine.Product = orderLine.Product;
                invoiceLine.ProductPrice = orderLine.ProductPrice;
                invoiceLine.Quantity = orderLine.Quantity;
                invoice.InvoiceLines.Add(invoiceLine);
              }

              InvoiceLine usageCharges = new InvoiceLine();
              usageCharges.Invoice = invoice;
              usageCharges.Product = billingService.GetProductByName("Oaas Usage Charges").First();
              usageCharges.ProductPrice = 999.99;
              usageCharges.Quantity = 1;
              invoice.InvoiceLines.Add(usageCharges);

              // Bill Post Processing: Apply Discounts or Promotions
              // add discounts, sum up items to sub-total, calc. tax -> total current charges
              // maybe use windows workflow foundation for this task 

              // Invoice Formatting Engine: Generate Invoice 
              invoice.InvoiceDocument = InvoiceFormattingEngine.Generate(invoice);

              UpdateBillingState(order);
              billingService.UpdateOrder(order);
              billingService.SaveInvoice(invoice);
            }
          }

          Trace.WriteLine("[BillingEngine] Finished billing cycle");
        }
        catch (Exception e) {
          Trace.WriteLine(string.Format("[BillingEngine] The following exception occured: {0}", e.ToString()));
        }
        waitHandle.WaitOne(interval);
      }
      waitHandle.Close();
    }

    private void UpdateBillingState(Order order) {
      if (order.BillingType == BillingType.Pre) {
        throw new Exception("This billing type is currently not supported: " + order.BillingType);
      }

      order.LastBillableDay = currentDate;
      DateTime nextBillingDay = CalculateNextBillingDate(order);

      if (order.ActiveUntil.HasValue && order.ActiveUntil == currentDate) {
        order.State = OrderState.Finished;
        order.NextBillableDay = null;
      } else if (order.ActiveUntil.HasValue && order.ActiveUntil < nextBillingDay) {
        order.NextBillableDay = order.ActiveUntil;
      } else {
        order.NextBillableDay = nextBillingDay;
      }

      order.EntityState = State.Modified;
    }

    private DateTime CalculateNextBillingDate(Order order) {
      DateTime nextBillingDay = currentDate;

      if (order.BillingPeriod == BillingPeriod.Weekly) {
        nextBillingDay = Next(currentDate, DayOfWeek.Sunday);
      } else if (order.BillingPeriod == BillingPeriod.Monthly) {
        DateTime endOfNextMonth = new DateTime(
          currentDate.AddMonths(1).Year,
          currentDate.AddMonths(1).Month,
          DateTime.DaysInMonth(currentDate.AddMonths(1).Year, currentDate.AddMonths(1).Month));
        nextBillingDay = endOfNextMonth;
      } else if (order.BillingPeriod == BillingPeriod.Yearly) {
        nextBillingDay = new DateTime(currentDate.AddYears(1).Year, 12, 31);
      }

      return nextBillingDay;
    }

    private DateTime Next(DateTime from, DayOfWeek dayOfWeek) {
      int start = (int)from.DayOfWeek;
      int target = (int)dayOfWeek;
      if (target <= start)
        target += 7;
      return from.AddDays(target - start);
    }
  }
}