PluralKit/PluralKit.Core/Utils/Partial.cs
2020-06-29 14:15:30 +02:00

82 lines
2.8 KiB
C#

#nullable enable
using System;
using System.Collections;
using System.Collections.Generic;
using Dapper;
using Newtonsoft.Json;
namespace PluralKit.Core
{
[JsonConverter(typeof(PartialConverter))]
public struct Partial<T>: IEnumerable<T>
{
public bool IsPresent { get; }
public T Value { get; }
private Partial(bool isPresent, T value)
{
IsPresent = isPresent;
Value = value;
}
public static Partial<T> Null() => new Partial<T>(true, default!);
public static Partial<T> Present(T obj) => new Partial<T>(true, obj);
public static Partial<T> Absent = new Partial<T>(false, default!);
public IEnumerable<T> ToArray() => IsPresent ? new[] {Value} : new T[0];
public IEnumerator<T> GetEnumerator() => ToArray().GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => ToArray().GetEnumerator();
public static implicit operator Partial<T>(T val) => Present(val);
}
public class PartialConverter: JsonConverter
{
public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue,
JsonSerializer serializer)
{
var innerType = objectType.GenericTypeArguments[0];
var innerValue = serializer.Deserialize(reader, innerType);
return typeof(Partial<>)
.MakeGenericType(innerType)
.GetMethod(nameof(Partial<object>.Present))!
.Invoke(null, new[] {innerValue});
}
public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer) =>
throw new NotImplementedException();
public override bool CanConvert(Type objectType) => true;
public override bool CanRead => true;
public override bool CanWrite => false;
}
public static class PartialExt
{
public static bool TryGet<T>(this Partial<T> pt, out T value)
{
value = pt.IsPresent ? pt.Value : default!;
return pt.IsPresent;
}
public static T Or<T>(this Partial<T> pt, T fallback) => pt.IsPresent ? pt.Value : fallback;
public static T Or<T>(this Partial<T> pt, Func<T> fallback) => pt.IsPresent ? pt.Value : fallback.Invoke();
public static Partial<TOut> Map<TIn, TOut>(this Partial<TIn> pt, Func<TIn, TOut> fn) =>
pt.IsPresent ? Partial<TOut>.Present(fn.Invoke(pt.Value)) : Partial<TOut>.Absent;
public static void Apply<T>(this Partial<T> pt, DynamicParameters bag, QueryBuilder qb, string fieldName)
{
if (!pt.IsPresent) return;
bag.Add(fieldName, pt.Value);
qb.Variable(fieldName, $"@{fieldName}");
}
}
}