TransactionCollection.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
// 
//        http://www.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace Deveel.Data.Transactions {
    public sealed class TransactionCollection : IEnumerable<ITransaction> {
        private readonly List<ITransaction> transactions;
        private long minCommitId;
        private long maxCommitId;
 
        public TransactionCollection() {
            transactions = new List<ITransaction>();
            minCommitId = Int64.MaxValue;
            maxCommitId = 0;
        }

        public int Count {
            get {
                lock (this) {
                    return transactions.Count;
                }
            }
        }

        public void AddTransaction(ITransaction transaction) {
            lock (this) {
                long currentCommitId = transaction.CommitId;
                if (currentCommitId < maxCommitId)
                    throw new InvalidOperationException("Added a transaction with a lower than maximum commit id");
                
                transactions.Add(transaction);
                //TODO: SystemContext.Stats.Increment(StatsDefaultKeys.OpenTransactionsCount);
                maxCommitId = currentCommitId;
            }
        }

        public void RemoveTransaction(ITransaction transaction) {
            lock (this) {
                int size = transactions.Count;
                int i = transactions.IndexOf(transaction);
                if (i == 0) {
                    // First in list.
                    if (i == size - 1) {
                        // And last.
                        minCommitId = Int32.MaxValue;
                        maxCommitId = 0;
                    } else {
                        minCommitId = transactions[i + 1].CommitId;
                    }
                } else if (i == transactions.Count - 1) {
                    // Last in list.
                    maxCommitId = transactions[i - 1].CommitId;
                } else if (i == -1) {
                    throw new InvalidOperationException("Unable to find transaction in the list.");
                }

                transactions.RemoveAt(i);
                //TODO: SystemContext.Stats.Decrement(StatsDefaultKeys.OpenTransactionsCount);
            }
        }

        public long MinimumCommitId(ITransaction transaction) {
            lock (this) {
                long commitId = Int64.MaxValue;
                if (transactions.Count > 0) {
                    // If the bottom transaction is this transaction, then go to the
                    // next up from the bottom (we don't count this transaction as the
                    // minimum commit_id).
                    var testTransaction = transactions[0];
                    if (testTransaction != transaction) {
                        commitId = testTransaction.CommitId;
                    } else if (transactions.Count > 1) {
                        commitId = transactions[1].CommitId;
                    }
                }

                return commitId;
            }
        }

        public IEnumerator<ITransaction> GetEnumerator() {
            lock (this) {
                return transactions.GetEnumerator();
            }
        }

        IEnumerator IEnumerable.GetEnumerator() {
            return GetEnumerator();
        }

        public ITransaction FindById(int commitId) {
            lock (this) {
                return transactions.FirstOrDefault(x => x.CommitId == commitId);
            }
        }
    }
}