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using System;
using System.Reflection;
using StardewModdingAPI.Framework.Utilities;
namespace StardewModdingAPI.Framework.Reflection
{
/// <summary>Provides helper methods for accessing inaccessible code.</summary>
/// <remarks>This implementation searches up the type hierarchy, and caches the reflected fields and methods with a sliding expiry (to optimize performance without unnecessary memory usage).</remarks>
internal class Reflector
{
/*********
** Fields
*********/
/// <summary>The cached fields and methods found via reflection.</summary>
private readonly IntervalMemoryCache<string, MemberInfo?> Cache = new();
/*********
** Public methods
*********/
/****
** Fields
****/
/// <summary>Get a instance field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="obj">The object which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the field isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the field wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the field doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target field doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedField<TValue> GetField<TValue>(object obj, string name, bool required = true)
{
// validate
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a instance field from a null object.");
// get field from hierarchy
IReflectedField<TValue>? field = this.GetFieldFromHierarchy<TValue>(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
if (required && field == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a '{name}' instance field.");
return field!;
}
/// <summary>Get a static field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="type">The type which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the field isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the field wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the field doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target field doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedField<TValue> GetField<TValue>(Type type, string name, bool required = true)
{
// get field from hierarchy
IReflectedField<TValue>? field = this.GetFieldFromHierarchy<TValue>(type, null, name, BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Public);
if (required && field == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a '{name}' static field.");
return field!;
}
/****
** Properties
****/
/// <summary>Get a instance property.</summary>
/// <typeparam name="TValue">The property type.</typeparam>
/// <param name="obj">The object which has the property.</param>
/// <param name="name">The property name.</param>
/// <param name="required">Whether to throw an exception if the property isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the property wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the property doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target property doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedProperty<TValue> GetProperty<TValue>(object obj, string name, bool required = true)
{
// validate
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a instance property from a null object.");
// get property from hierarchy
IReflectedProperty<TValue>? property = this.GetPropertyFromHierarchy<TValue>(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
if (required && property == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a '{name}' instance property.");
return property!;
}
/// <summary>Get a static property.</summary>
/// <typeparam name="TValue">The property type.</typeparam>
/// <param name="type">The type which has the property.</param>
/// <param name="name">The property name.</param>
/// <param name="required">Whether to throw an exception if the property isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the property wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the property doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target property doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedProperty<TValue> GetProperty<TValue>(Type type, string name, bool required = true)
{
// get field from hierarchy
IReflectedProperty<TValue>? property = this.GetPropertyFromHierarchy<TValue>(type, null, name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static);
if (required && property == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a '{name}' static property.");
return property!;
}
/****
** Methods
****/
/// <summary>Get a instance method.</summary>
/// <param name="obj">The object which has the method.</param>
/// <param name="name">The method name.</param>
/// <param name="required">Whether to throw an exception if the method isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the method wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the method doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target method doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedMethod GetMethod(object obj, string name, bool required = true)
{
// validate
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a instance method from a null object.");
// get method from hierarchy
IReflectedMethod? method = this.GetMethodFromHierarchy(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
if (required && method == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a '{name}' instance method.");
return method!;
}
/// <summary>Get a static method.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="name">The method name.</param>
/// <param name="required">Whether to throw an exception if the method isn't found. <strong>Due to limitations with nullable reference types, setting this to <c>false</c> will still mark the value non-nullable.</strong></param>
/// <returns>Returns the method wrapper, or <c>null</c> if <paramref name="required"/> is <c>false</c> and the method doesn't exist.</returns>
/// <exception cref="InvalidOperationException">The target method doesn't exist, and <paramref name="required"/> is true.</exception>
public IReflectedMethod GetMethod(Type type, string name, bool required = true)
{
// get method from hierarchy
IReflectedMethod? method = this.GetMethodFromHierarchy(type, null, name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static);
if (required && method == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a '{name}' static method.");
return method!;
}
/****
** Management
****/
/// <summary>Start a new cache interval, clearing stale reflection lookups.</summary>
public void NewCacheInterval()
{
this.Cache.StartNewInterval();
}
/*********
** Private methods
*********/
/// <summary>Get a field from the type hierarchy.</summary>
/// <typeparam name="TValue">The expected field type.</typeparam>
/// <param name="type">The type which has the field.</param>
/// <param name="obj">The object which has the field, or <c>null</c> for a static field.</param>
/// <param name="name">The field name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of field to find.</param>
private IReflectedField<TValue>? GetFieldFromHierarchy<TValue>(Type type, object? obj, string name, BindingFlags bindingFlags)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
FieldInfo? field = this.GetCached(
'f', type, name, isStatic,
fetch: () =>
{
for (Type? curType = type; curType != null; curType = curType.BaseType)
{
FieldInfo? fieldInfo = curType.GetField(name, bindingFlags);
if (fieldInfo != null)
{
type = curType;
return fieldInfo;
}
}
return null;
}
);
return field != null
? new ReflectedField<TValue>(type, obj, field, isStatic)
: null;
}
/// <summary>Get a property from the type hierarchy.</summary>
/// <typeparam name="TValue">The expected property type.</typeparam>
/// <param name="type">The type which has the property.</param>
/// <param name="obj">The object which has the property, or <c>null</c> for a static property.</param>
/// <param name="name">The property name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of property to find.</param>
private IReflectedProperty<TValue>? GetPropertyFromHierarchy<TValue>(Type type, object? obj, string name, BindingFlags bindingFlags)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
PropertyInfo? property = this.GetCached(
'p', type, name, isStatic,
fetch: () =>
{
for (Type? curType = type; curType != null; curType = curType.BaseType)
{
PropertyInfo? propertyInfo = curType.GetProperty(name, bindingFlags);
if (propertyInfo != null)
{
type = curType;
return propertyInfo;
}
}
return null;
}
);
return property != null
? new ReflectedProperty<TValue>(type, obj, property, isStatic)
: null;
}
/// <summary>Get a method from the type hierarchy.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="obj">The object which has the method, or <c>null</c> for a static method.</param>
/// <param name="name">The method name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of method to find.</param>
private IReflectedMethod? GetMethodFromHierarchy(Type type, object? obj, string name, BindingFlags bindingFlags)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
MethodInfo? method = this.GetCached(
'm', type, name, isStatic,
fetch: () =>
{
for (Type? curType = type; curType != null; curType = curType.BaseType)
{
MethodInfo? methodInfo = curType.GetMethod(name, bindingFlags);
if (methodInfo != null)
{
type = curType;
return methodInfo;
}
}
return null;
}
);
return method != null
? new ReflectedMethod(type, obj, method, isStatic: isStatic)
: null;
}
/// <summary>Get a method or field through the cache.</summary>
/// <typeparam name="TMemberInfo">The expected <see cref="MemberInfo"/> type.</typeparam>
/// <param name="memberType">A letter representing the member type (like 'm' for method).</param>
/// <param name="type">The type whose members are being reflected.</param>
/// <param name="memberName">The member name.</param>
/// <param name="isStatic">Whether the member is static.</param>
/// <param name="fetch">Fetches a new value to cache.</param>
private TMemberInfo? GetCached<TMemberInfo>(char memberType, Type type, string memberName, bool isStatic, Func<TMemberInfo?> fetch)
where TMemberInfo : MemberInfo
{
string key = $"{memberType}{(isStatic ? 's' : 'i')}{type.FullName}:{memberName}";
return (TMemberInfo?)this.Cache.GetOrSet(key, fetch);
}
}
}
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