protected virtual void OnDebtDealReceived(
object o_debtDealsRegister, DebtDealReceivedEventData evData
)
{
/*
* *** Notes on parallel execution ***
*
* Similar to DebtDealsRegister Add method,
* consider only these cases:
*
* two unique involved id-s:
* * same giver, same taker
* * D1.giver = D2.taker, D1.taker = D2.giver
*
* Need to consider parallel changes of the same debt
* in CurrentDebts table.
*
* Result - serialize always when
* two deals have only two unique involved id-s.
*/
DebtDealRow deal = evData.Deal;
DebtRow initialGiverDebtToTaker
= this.dbc.CurrentDebts.Where(cd =>
cd.CreditorId == deal.TakerId &&
cd.DebtorId == deal.GiverId).FirstOrDefault();
if (initialGiverDebtToTaker == null)
{
initialGiverDebtToTaker = new DebtRow {
CreditorId = deal.TakerId, DebtorId = deal.GiverId
}
}
;
DebtRow initialTakerDebtToGiver
= this.dbc.CurrentDebts.Where(cd =>
cd.CreditorId == deal.GiverId &&
cd.DebtorId == deal.TakerId).FirstOrDefault();
if (initialTakerDebtToGiver == null)
{
initialTakerDebtToGiver = new DebtRow {
CreditorId = deal.GiverId, DebtorId = deal.TakerId
}
}
;
DebtRow debtToChange;
if (evData.Analysis.IsPayback)
{
debtToChange = initialGiverDebtToTaker;
}
else
{
debtToChange = initialTakerDebtToGiver;
}
decimal initialDebtAmount = debtToChange?.DebtTotal ?? 0m;
decimal resultingDebtAmount;
if (evData.Analysis.IsPayback)
{
resultingDebtAmount = Math.Max(0m,
initialDebtAmount - deal.Amount);
}
else
{
resultingDebtAmount = initialDebtAmount + deal.Amount;
}
debtToChange.DebtTotal = resultingDebtAmount;
if (resultingDebtAmount > DebtConstants.MaxZeroEquivalent)
{
if (this.dbc.CurrentDebts.Count(cd =>
cd.CreditorId == debtToChange.CreditorId &&
cd.DebtorId == debtToChange.DebtorId
)
== 0
)
{
this.dbc.CurrentDebts.Add(debtToChange);
}
}
else
{
this.dbc.CurrentDebts.Remove(debtToChange);
}
this.dbc.SaveChanges();
}
/// <summary>
///
/// </summary>
/// <param name="evData"></param>
/// <returns>new taker totals</returns>
private void UpdateTotalsPerPerson(DebtDealReceivedEventData evData)
{
/*
* *** Notes on parallel execution ***
*
* Need to consider:
* * parallel changes of the same
* giverTotals and takerTotals red from
* CurrentTotalsPerPerson table.
*
* * parallel attempts to add new totals
* for the same giver or taker.
*
* Result - serialize for operations in CurrentTotalsPerPerson
* table with the same giverId or takerId.
*/
DebtDealRow deal = evData.Deal;
PersonTotalsRow giverTotals
= this.dbc.CurrentTotalsPerPerson
.Where(ct => ct.PersonId == deal.GiverId)
.FirstOrDefault()
?? new PersonTotalsRow();
giverTotals.PersonId = deal.GiverId;
PersonTotalsRow takerTotals
= this.dbc.CurrentTotalsPerPerson
.Where(ct => ct.PersonId == deal.TakerId)
.FirstOrDefault()
?? new PersonTotalsRow();
takerTotals.PersonId = deal.TakerId;
if (evData.Analysis.IsPayback)
{
giverTotals.DueDebtsTotal = Math.Max(
0, giverTotals.DueDebtsTotal - deal.Amount);
}
else
{
giverTotals.HistoricallyCreditedInTotal += deal.Amount;
takerTotals.DueDebtsTotal += deal.Amount;
takerTotals.HistoricallyOwedInTotal += deal.Amount;
takerTotals.HistoricalCountOfCreditsTaken++;
}
if (this.dbc.CurrentTotalsPerPerson
.Count(ct => ct.PersonId == deal.GiverId) == 0
)
{
this.dbc.CurrentTotalsPerPerson.Add(giverTotals);
}
if (this.dbc.CurrentTotalsPerPerson
.Count(ct => ct.PersonId == deal.TakerId) == 0
)
{
this.dbc.CurrentTotalsPerPerson.Add(takerTotals);
}
this.dbc.SaveChanges();
}
public long Add(DebtDealRow deal)
{
/*
* *** Notes on parallel execution ***
*
* If two debt deals have 4 unique involved people id-s,
* these same deals may be processed in parallel in this register
* (but may need serialization while other registers handle
* DebtDealAdded event).
*
* Need to consider validity of initialGiverDebtToTaker.
*
* Other cases:
* three unique involved id-s:
* same giver, different takers: => parallel-ok
*
* different givers, same taker: => parallel-ok
*
* two unique involved id-s:
* same giver, same taker => serialize (case a)
*
* D1.giver = D2.taker, D1.taker = D2.giver
* => serialize (case b)
*
*
* Here, parallel execution has to be serialized when register
* has not finished processing two deals which match one of these:
* a) if giver and taker are the same for two deals,
* later deal must wait till earlier one is fully processed.
* (consider small and complete pay-back immediately
* followed by a big credit - if D1 is processed after D2
* was fully processed, big credit could be considered
* as mostly a GIFT, confusing it with a payback)
*
* b) if D1.giver = D2.taker, D1.taker = D2.giver
* (consider pay and repay of the same amount -
* in case of parallel execution of both deals,
* payback could be missed and DB would get corrupt)
*/
long addedDebtDealId;
using (var transaction = this.dbc.Database.BeginTransaction()) {
this.dbc.DebtDeals.Add(deal);
this.dbc.SaveChanges(); // need deal.Id
addedDebtDealId = deal.Id;
decimal initialGiverDebtToTaker = GiverDebtToTaker();
decimal?repayGiftAmount = null;
if (initialGiverDebtToTaker > 0m)
{
repayGiftAmount
= Math.Max(0m,
deal.Amount - initialGiverDebtToTaker);
}
var analysisRow = new DebtDealAnalysisRow()
{
DebtDealId = deal.Id,
IsPayback = initialGiverDebtToTaker > 0m
};
this.dbc.DebtDealsAnalysis.Add(analysisRow);
this.dbc.SaveChanges();
DebtDealReceived?.Invoke(this,
new DebtDealReceivedEventData()
{
Deal = deal,
Analysis = analysisRow,
RepayGiftAmount = repayGiftAmount
});
transaction.Commit();
}
DebtDealAdded?.Invoke(this,
new DebtDealAddedEventData()
{
AddedDebtDealId = addedDebtDealId
});
return(addedDebtDealId);
decimal GiverDebtToTaker()
{
return(this.dbc.CurrentDebts.Where(cd =>
cd.CreditorId == deal.TakerId &&
cd.DebtorId == deal.GiverId
).Select(cd => cd.DebtTotal).FirstOrDefault());
}
}