using System;

using System.Dynamic;

using System.Runtime.CompilerServices;

using Microsoft.CSharp.RuntimeBinder;

namespace Python.Runtime;

class DynamicObjectMemberAccessor

{

const int MaxCacheEntries = 1000;

readonly ConcurrentLruCache<MemberKey, Func<object, object>> getters = new(MaxCacheEntries);

readonly ConcurrentLruCache<MemberKey, Action<object, object?>> setters = new(MaxCacheEntries);

static readonly CSharpArgumentInfo[] getArgumentInfo =

{

CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),

};

static readonly CSharpArgumentInfo[] setArgumentInfo =

{

CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),

CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),

};

public bool TryGetMember(IDynamicMetaObjectProvider obj, string memberName, out object? value)

{

if (obj is null)

throw new ArgumentNullException(nameof(obj));

if (memberName is null)

throw new ArgumentNullException(nameof(memberName));

var getter = getters.GetOrAdd(new MemberKey(obj.GetType(), memberName), static key =>

{

var binder = Binder.GetMember(CSharpBinderFlags.None, key.MemberName, key.Type, getArgumentInfo);

var callSite = CallSite<Func<CallSite, object, object>>.Create(binder);

return obj => callSite.Target(callSite, obj);

});

try

{

value = getter(obj);

return true;

}

catch (RuntimeBinderException)

{

value = null;

return false;

}

}

public bool TrySetMember(IDynamicMetaObjectProvider obj, string memberName, object? value)

{

if (obj is null)

throw new ArgumentNullException(nameof(obj));

if (memberName is null)

throw new ArgumentNullException(nameof(memberName));

var setter = setters.GetOrAdd(new MemberKey(obj.GetType(), memberName), static key =>

{

var binder = Binder.SetMember(CSharpBinderFlags.None, key.MemberName, key.Type, setArgumentInfo);

var callSite = CallSite<Action<CallSite, object, object?>>.Create(binder);

return (obj, value) => callSite.Target(callSite, obj, value);

});

try

{

setter(obj, value);

return true;

}

catch (RuntimeBinderException)

{

return false;

}

}

readonly record struct MemberKey(Type Type, string MemberName);

public void Clear()

{

getters.Clear();

setters.Clear();

}

}