51 lines
No EOL
1.7 KiB
C#
51 lines
No EOL
1.7 KiB
C#
using System.Linq.Expressions;
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namespace Iceshrimp.Backend.Core.Extensions;
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public static class ExpressionExtensions
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{
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public static Expression<Func<T, bool>> True<T>() => f => true;
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public static Expression<Func<T, bool>> False<T>() => f => false;
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public static Expression<Func<T, bool>> Or<T>(
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this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2
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)
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{
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var invokedExpr = Expression.Invoke(expr2, expr1.Parameters);
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return Expression.Lambda<Func<T, bool>>(Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
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}
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public static Expression<Func<T, bool>> And<T>(
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this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2
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)
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{
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var invokedExpr = Expression.Invoke(expr2, expr1.Parameters);
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return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
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}
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public static Expression<Func<TFirstParam, TResult>> Compose<TFirstParam, TIntermediate, TResult>(
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this Expression<Func<TFirstParam, TIntermediate>> first,
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Expression<Func<TIntermediate, TResult>> second
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)
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{
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var param = Expression.Parameter(typeof(TFirstParam), "param");
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var newFirst = first.Body.Replace(first.Parameters[0], param);
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var newSecond = second.Body.Replace(second.Parameters[0], newFirst);
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return Expression.Lambda<Func<TFirstParam, TResult>>(newSecond, param);
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}
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private static Expression Replace(this Expression expression, Expression searchEx, Expression replaceEx)
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{
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return new ReplaceVisitor(searchEx, replaceEx).Visit(expression) ?? throw new NullReferenceException();
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}
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private class ReplaceVisitor(Expression from, Expression to) : ExpressionVisitor
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{
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public override Expression? Visit(Expression? node)
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{
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return node == from ? to : base.Visit(node);
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}
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}
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} |