using System;
using System.Configuration;
using System.Data.SqlClient;
using System.Diagnostics;
using System.Transactions;
using HeuristicLab.Services.Optimization.Billing.Interfaces;

namespace HeuristicLab.Services.Optimization.Billing.Business {
  public class TransactionManager : ITransactionManager {
    private const int retries = 10;
    private readonly TimeSpan timeoutInterval;

    public TransactionManager() {
      timeoutInterval = TimeSpan.Parse(ConfigurationManager.AppSettings["LongRunningDbCommandTimeout"]);
    }

    public void UseTransaction(System.Action call, bool repeatableRead = false, bool longRunning = false) {
      int n = retries;
      while (n > 0) {
        TransactionScope transaction = CreateTransaction(repeatableRead, longRunning);
        try {
          call();
          transaction.Complete();
          n = 0;
        }
        catch (SqlException ex) {
          n--;
          // TODO: log exception
          Trace.WriteLine(string.Format("Exception occured, repeating transaction {0} more times: {1}", n, ex.ToString()));
          if (n <= 0) throw;
        }
        finally {
          transaction.Dispose();
        }
      }
    }

    public T UseTransaction<T>(System.Func<T> call, bool repeatableRead = false, bool longRunning = false) {
      int n = retries;
      while (n > 0) {
        TransactionScope transaction = CreateTransaction(repeatableRead, longRunning);
        try {
          T result = call();
          transaction.Complete();
          n = 0;
          return result;
        }
        catch (SqlException ex) {
          n--;
          // TODO: log exception
          Trace.WriteLine(string.Format("Exception occured, repeating transaction {0} more times: {1}", n, ex.ToString()));
          if (n <= 0) throw;
        }
        finally {
          transaction.Dispose();
        }
      }
      throw new Exception("This code should not be reached");
    }

    private TransactionScope CreateTransaction(bool repeatableRead, bool longRunning) {
      var options = new TransactionOptions();
      if (repeatableRead) {
        options.IsolationLevel = IsolationLevel.RepeatableRead;
      } else {
        options.IsolationLevel = IsolationLevel.ReadUncommitted;
      }

      if (longRunning) {
        options.Timeout = timeoutInterval;
      }

      return new TransactionScope(TransactionScopeOption.Required, options);
    }
  }
}