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

namespace ConsoleApplication1
{
    static class LINQ
    {
        static void Main(String[] args)
        {
            Console.WriteLine("単一要素の取得");
            単一要素の取得();

            Console.WriteLine("複数要素の取得");
            複数要素の取得();

            Console.WriteLine("集計");
            集計();

            Console.WriteLine("判定");
            判定();

            Console.WriteLine("集合");
            集合();

            Console.WriteLine("ソート");
            ソート();

            Console.WriteLine("射影");
            射影();

            Console.WriteLine("結合");
            結合();

            Console.WriteLine("変換");
            変換();
        }

        private static void 単一要素の取得()
        {
            var source = new[] { 11, 16, 52, 21, 8, 8 };

            Console.WriteLine(source.ElementAt(2));
            // -> 52
            Console.WriteLine(source.ElementAtOrDefault(8));
            // -> 0
            Console.WriteLine(source.First());
            // -> 11
            Console.WriteLine(source.First(e => e > 15));
            // -> 16
            Console.WriteLine(source.Last());
            // -> 8
            Console.WriteLine(source.Last(e => e > 15));
            // -> 21
            //Console.WriteLine(source.Single());
            // -> System.InvalidOperationException: シーケンスに複数の要素が含まれています
            Console.WriteLine(source.Single(e => e > 50));
            // -> 52
        }

        private static void 複数要素の取得()
        {
            var source = new[] { 11, 16, 52, 21, 8, 8 };

            Console.WriteLine(source.Where(e => e > 20).ToResult());
            // -> {52, 21}
            Console.WriteLine(source.Distinct().ToResult());
            // -> {11, 16, 52, 21, 8}
            Console.WriteLine(source.Skip(3).ToResult());
            // -> {21, 8, 8}
            Console.WriteLine(source.SkipWhile(e => e < 20).ToResult());
            // -> {52, 21, 8, 8}
            Console.WriteLine(source.Take(3).ToResult());
            // -> {11, 16, 52}
            Console.WriteLine(source.TakeWhile(e => e < 20).ToResult());
            // -> {11, 16}
        }

        private static void 集計()
        {
            var source = new[] { 11, 16, 52, 21, 8, 8 };

            Console.WriteLine("集計");
            Console.WriteLine(source.Max());
            // -> 52
            Console.WriteLine(source.Min());
            // -> 8
            Console.WriteLine(source.Average());
            // -> 19.3333333333333
            Console.WriteLine(source.Sum());
            // -> 116
            Console.WriteLine(source.Count());
            // -> 6
            Console.WriteLine(source.Aggregate((now, next) => Math.Max(now, next)));
            // -> 52

            // 参考：標本分散
            double ave = source.Average();
            Console.WriteLine(source.Sum(e => Math.Pow(e - ave, 2)) / source.Count());
            // -> 234.555555555556
        }

        private static void 判定()
        {
            var source = new[] { 11, 16, 52, 21, 8, 8 };

            Console.WriteLine(source.All(e => e > 10));
            // -> False
            Console.WriteLine(source.Any(e => e > 10));
            // -> True
            Console.WriteLine(source.Contains(20));
            // -> False
            Console.WriteLine(source.SequenceEqual(new[] { 11, 16, 21, 52, 8, 8 }));
            // -> False
        }

        private static void 集合()
        {
            var first = new[] { 11, 16, 52, 21, 8, 8 };
            var second = new[] { 16, 21, 20, 3 };

            Console.WriteLine(first.Union(second).ToResult());
            // -> {11, 16, 52, 21, 8, 20, 3}
            Console.WriteLine(first.Except(second).ToResult());
            // -> {11, 52, 8}
            Console.WriteLine(first.Intersect(second).ToResult());
            // -> {16, 21}
        }

        private static void ソート()
        {
            var source = new[] {
                new{Name = "C#", Age = 11},
                new{Name = "Java", Age = 16},
                new{Name = "Groovy", Age = 8},
                new{Name = "Scala", Age = 8},
            };

            Console.WriteLine(source.OrderBy(e => e.Age).ToResult());
            // -> {{ Name = Groovy, Age = 8 },
            //     { Name = Scala, Age = 8 }, 
            //     { Name = C#, Age = 11 },
            //     { Name = Java, Age = 16 }}
            Console.WriteLine(source.OrderByDescending(e => e.Age).ToResult());
            // -> {{ Name = Java, Age = 16 },
            //     { Name = C#, Age = 11 },
            //     { Name = Groovy, Age = 8 },
            //     { Name = Scala, Age = 8 }}
            Console.WriteLine(source.OrderBy(e => e.Age)
                                    .ThenBy(e => e.Name.Length).ToResult());
            // -> {{ Name = Scala, Age = 8 },
            //     { Name = Groovy, Age = 8 },
            //     { Name = C#, Age = 11 },
            //     { Name = Java, Age = 16 }}
            Console.WriteLine(source.OrderBy(e => e.Age)
                                    .ThenByDescending(e => e.Name.Length).ToResult());
            // -> {{ Name = Groovy, Age = 8 },
            //     { Name = Scala, Age = 8 },
            //     { Name = C#, Age = 11 },
            //     { Name = Java, Age = 16 }}
            Console.WriteLine(source.Reverse().ToResult());
            // -> {{ Name = Scala, Age = 8 },
            //     { Name = Groovy, Age = 8 },
            //     { Name = Java, Age = 16},
            //     { Name = C#, Age = 11 }}
        }

        private static void 射影()
        {
            var source = new[] {
                new{Name = "C#", Age = 11},
                new{Name = "Java", Age = 16},
                new{Name = "Groovy", Age = 8},
                new{Name = "Scala", Age = 8},
            };
            Console.WriteLine(source.Select(e => e.Name).ToResult());
            // -> {C#, Java, Groovy, Scala}
            Console.WriteLine(source.SelectMany(e => e.Name.ToCharArray()).ToResult());
            // -> {C, #, J, a, v, a, G, r, o, o, v, y, S, c, a, l, a}
            Console.WriteLine(source.GroupBy(e => e.Age).ToResult());
            // -> {Key=11, Source={{ Name = C#, Age = 11 }},
            //     Key=16, Source={{ Name = Java, Age = 16 }},
            //     Key=8, Source={{ Name = Groovy, Age = 8 }, { Name = Scala, Age = 8 }}}
        }
            
        private static void 結合()
        {
            var outer = new[] {
                new{Name = "C#", Age = 11},
                new{Name = "Java", Age = 16},
                new{Name = "Groovy", Age = 8},
                new{Name = "Scala", Age = 8},
            };
            var outer2 = new[] {
                 new{Name = "Python", Age = 21},
                 new{Name = "COBOL", Age = 52},
            };
            var inner = new[] {
                new{Name = "C#", DesignedBy = "Microsoft"},
                new{Name = "Java", DesignedBy = "Sun Microsystems"},
                new{Name = "Java", DesignedBy = "Oracle"},
            };
            Console.WriteLine(outer.Join(inner, o => o.Name, i => i.Name, (o, i) => new { o.Name, o.Age, i.DesignedBy}).ToResult());
            // -> {{ Name = C#, Age = 11, DesignedBy = Microsoft },
            //     { Name = Java, Age = 16, DesignedBy = Sun Microsystems },
            //     { Name = Java, Age = 16, DesignedBy = Oracle }}
            Console.WriteLine(outer.GroupJoin(inner, o => o.Name, i => i.Name, (o, i) => new { o.Name, o.Age, DesigndBy = i.Select(e => e.DesignedBy).ToResult() }).ToResult());
            // -> {{ Name = C#, Age = 11, DesigndBy = {Microsoft} },
            //     { Name = Java, Age = 16, DesigndBy = {Sun Microsystems, Oracle} },
            //     { Name = Groovy, Age = 8, DesigndBy = {} },
            //     { Name = Scala, Age = 8, DesigndBy = {} }}
            Console.WriteLine(outer.Concat(outer2).ToResult());
            // -> {{ Name = C#, Age = 11 },
            //     { Name = Java, Age = 16 },
            //     { Name = Groovy, Age = 8 },
            //     { Name = Scala, Age = 8 },
            //     { Name = Python, Age = 21 },
            //     { Name = COBOL, Age = 52 }}
            Console.WriteLine(outer.DefaultIfEmpty().ToResult());
            // -> {{ Name = C#, Age = 11 },
            //     { Name = Java, Age = 16 },
            //     { Name = Groovy, Age = 8 },
            //     { Name = Scala, Age = 8 }}
            Console.WriteLine(outer.Zip(outer2, (o1, o2) => o1.Name + "&" + o2.Name).ToResult());
            // -> {C#&Python, Java&COBOL}
        }

        private static void 変換()
        {
            ArrayList mixed = new ArrayList { "C#", "Java", 3.141592653, "Groovy", "Scala" };

            Console.WriteLine(mixed.OfType<string>().ToResult());
            // -> {C#, Java, Groovy, Scala}
            //Console.WriteLine(mixed.Cast<string>().ToResult());
            // -> System.InvalidCastException: 
            //    型 'System.Double' のオブジェクトを型 'System.String' にキャストできません。
        }

        /// <summary>
        /// IEnumerable&lt;T&gt; を文字列に変換します。
        /// </summary>
        /// <typeparam name="TSource">要素の型</typeparam>
        /// <param name="source">変換元の IEnumerable&lt;T&gt;</param>
        /// <returns>変換した文字列</returns>
        static String ToResult<TSource>(this IEnumerable<TSource> source)
        {
            return "{" + string.Join(", ", source) + "}";
        }

        /// <summary>
        /// IEnumerable&lt;IGrouping&lt;TKey, TSource&gt;&gt; を文字列に変換します。
        /// </summary>
        /// <typeparam name="TKey">キーの型</typeparam>
        /// <typeparam name="TSource">要素の型</typeparam>
        /// <param name="source">変換元の IEnumerable&lt;IGrouping&lt;TKey, TSource&gt;&gt;</param>
        /// <returns>変換した文字列</returns>
        static String ToResult<TKey, TSource>(this IEnumerable<IGrouping<TKey, TSource>> source)
        {
            return source.Select(group => string.Format("Key={0}, Source={1}", group.Key, group.ToResult())).ToResult();
        }
    }
}