using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace GitTask
{
    public class Git
    {
        private List<int>[] commitsKeys;
        private List<int>[] commitsValues;
        private int timesCommited;

        public Git(int filesCount)
        {
            commitsKeys = new List<int>[filesCount];
            commitsValues = new List<int>[filesCount];

            for (var i = 0; i < filesCount; i++)
            {
                commitsKeys[i] = new List<int>();
                commitsValues[i] = new List<int>();
                commitsKeys[i].Add(-1);
                commitsValues[i].Add(0);
            }
        }

        public void Update(int fileNumber, int value)
        {
            var file = commitsValues[fileNumber];
            file[0] = value;
        }

        public int Commit()
        {
            for (var i = 0; i < commitsKeys.Length; i++)
            {
                var file = commitsValues[i];
                var currentValue = file[0];
                var latestCommitValue = file.Last();
                if (currentValue != latestCommitValue || file.Count == 1)
                {
                    commitsKeys[i].Add(timesCommited);
                    file.Add(currentValue);
                }
            }

//            var tasks = new List<Task>();
//            for (var i = 0; i < commitsKeys.Length; i++)
//            {
//                var tmp = i;
//                tasks.Add(Task.Factory.StartNew(() =>
//                {
//                    var file = commitsValues[tmp];
//                    var currentValue = file[0];
//                    var latestCommitValue = file.Last();
//                    if (currentValue != latestCommitValue || file.Count == 1)
//                    {
//                        commitsKeys[tmp].Add(timesCommited);
//                        file.Add(currentValue);
//                    }
//                }));
//            }
//            Task.WaitAll(tasks.ToArray());
//            Console.WriteLine("All threads complete");

            timesCommited++;
            return timesCommited - 1;
        }

        private static int BinarySearch<T>(IList<T> list, T value)
        {
            var comp = Comparer<T>.Default;
            var low = 0;
            var high = list.Count - 1;
            while (low < high) {
                var m = (high + low) / 2;
                if (comp.Compare(list[m], value) < 0)
                    low = m + 1;
                else
                    high = m;
            }
            return low;
        }

        public int Checkout(int commitNumber, int fileNumber)
        {
            if (timesCommited - 1 < commitNumber)
            {
                throw new System.ArgumentException();
            }

            var lessOrEqKey = BinarySearch(commitsKeys[fileNumber], commitNumber);
            return commitsValues[fileNumber][lessOrEqKey];
        }
    }
}