private async Task OrderByDependencyTest(
Func <
Func <char, CancellationToken, ValueTask <char> >,
IAsyncKeyResolver <char, char> > cacheFactory)
{
IEnumerable <char> DepSelector1(char c) =>
Enumerable
.Range(0, c - '0')
.Select(i => (char)('0' + i));
IEnumerable <char> BadDepSelector1(char c) => new [] { c };
IEnumerable <char> BadDepSelector2(char c) =>
Enumerable
.Range(1, 5)
.Select(i => (char)('0' + (c - '0' + i) % 10));
async Task <string> OrderByDependency(string s, Func <char, IEnumerable <char> > depSelector)
{
var result = new List <char>();
IAsyncKeyResolver <char, char>?cache = null;
async ValueTask <char> Compute(char c, CancellationToken ct)
{
if (cache == null)
{
throw new NullReferenceException();
}
foreach (var d in depSelector(c))
{
// ReSharper disable once AccessToModifiedClosure
await cache.Get(d).ConfigureAwait(false);
}
result.Add(c);
return(c);
}
cache = cacheFactory(Compute);
await cache.GetManyAsync(s.ToAsyncEnumerable()).CountAsync();
return(result.ToDelimitedString(""));
}
Assert.Equal("", await OrderByDependency("", DepSelector1));
Assert.Equal("01", await OrderByDependency("1", DepSelector1));
Assert.Equal("012", await OrderByDependency("12", DepSelector1));
Assert.Equal("012", await OrderByDependency("21", DepSelector1));
Assert.Equal("0123", await OrderByDependency("231", DepSelector1));
await Assert.ThrowsAsync <InvalidOperationException>(async() => {
var _ = await OrderByDependency("0", BadDepSelector1);
});
await Assert.ThrowsAsync <InvalidOperationException>(async() => {
var _ = await OrderByDependency("0", BadDepSelector2);
});
}
