namespace System.Linq;

public static class Enumerable
{
    public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
        this IEnumerable<TOuter> outer,
        IEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
        this IEnumerable<TOuter> outer,
        IEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
        this IEnumerable<TOuter> outer,
        IEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);
}

public static class Queryable
{
    public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
        this IQueryable<TOuter> outer,
        IEnumerable<TInner> inner,
        Expression<Func<TOuter, TKey>> outerKeySelector,
        Expression<Func<TInner, TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
        this IQueryable<TOuter> outer,
        IEnumerable<TInner> inner,
        Expression<Func<TOuter, TKey>> outerKeySelector,
        Expression<Func<TInner, TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
        this IQueryable<TOuter> outer,
        IEnumerable<TInner> inner,
        Expression<Func<TOuter, TKey>> outerKeySelector,
        Expression<Func<TInner, TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);
}

public static class AsyncEnumerable
{
    public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer, 
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
        Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer,
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer, 
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
        Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer,
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer, 
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
        Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);

    public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
        this IAsyncEnumerable<TOuter> outer,
        IAsyncEnumerable<TInner> inner,
        Func<TOuter, TKey> outerKeySelector,
        Func<TInner, TKey> innerKeySelector,
        IEqualityComparer<TKey>? comparer = null);
}

var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();

foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
    Console.WriteLine(s + " : " pair.Key);

foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
    Console.WriteLine(s + " : " pair.Key);

public static partial class Enumerable
{
    public static IEnumerable<(TKey,TOuter,TInner)> Join<TOuter, TInner, TKey>(this IEnumerable<TOuter> outer, IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector, Func<TInner, TKey> innerKeySelector);
}