// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Dynamic;
using System.Numerics.Hashing;
using Microsoft.CSharp.RuntimeBinder.Errors;
using Microsoft.CSharp.RuntimeBinder.Semantics;
 
namespace Microsoft.CSharp.RuntimeBinder
{
    /// <summary>
    /// Represents a dynamic conversion in C#, providing the binding semantics and the details about the operation.
    /// Instances of this class are generated by the C# compiler.
    /// </summary>
    internal sealed class CSharpConvertBinder : ConvertBinder, ICSharpBinder
    {
        [ExcludeFromCodeCoverage(Justification = "Name should not be called for this binder")]
        public string Name
        {
            get
            {
                Debug.Fail("Name should not be called for this binder");
                return null;
            }
        }
 
        public BindingFlag BindingFlags => 0;
 
        [RequiresUnreferencedCode(Binder.TrimmerWarning)]
        public Expr DispatchPayload(RuntimeBinder runtimeBinder, ArgumentObject[] arguments, LocalVariableSymbol[] locals)
        {
            Debug.Assert(arguments.Length == 1);
            return Explicit
                ? runtimeBinder.BindExplicitConversion(arguments, Type, locals)
                : runtimeBinder.BindImplicitConversion(arguments, Type, locals, ConversionKind == CSharpConversionKind.ArrayCreationConversion);
        }
 
        [RequiresUnreferencedCode(Binder.TrimmerWarning)]
        public void PopulateSymbolTableWithName(Type callingType, ArgumentObject[] arguments)
        {
            // Conversions don't need to do anything, since they're just conversions!
            // After we add payload information, we add conversions for all argument
            // types anyway, so that will get handled there.
        }
 
        public bool IsBinderThatCanHaveRefReceiver => false;
 
        CSharpArgumentInfo ICSharpBinder.GetArgumentInfo(int index) => CSharpArgumentInfo.None;
 
        private CSharpConversionKind ConversionKind { get; }
 
        private readonly RuntimeBinder _binder;
 
        private readonly Type _callingContext;
 
        private bool IsChecked => _binder.IsChecked;
 
        /// <summary>
        /// Initializes a new instance of the <see cref="CSharpConvertBinder" />.
        /// </summary>
        /// <param name="type">The type to convert to.</param>
        /// <param name="conversionKind">The kind of conversion for this operation.</param>
        /// <param name="isChecked">True if the operation is defined in a checked context; otherwise, false.</param>
        /// <param name="callingContext">The <see cref="Type"/> that indicates where this operation is defined.</param>
        [RequiresUnreferencedCode(Binder.TrimmerWarning)]
        public CSharpConvertBinder(
            Type type,
            CSharpConversionKind conversionKind,
            bool isChecked,
            Type callingContext) :
            base(type, conversionKind == CSharpConversionKind.ExplicitConversion)
        {
            ConversionKind = conversionKind;
            _callingContext = callingContext;
            _binder = new RuntimeBinder(callingContext, isChecked);
        }
 
        public int GetGetBinderEquivalenceHash()
        {
            int hash = _callingContext?.GetHashCode() ?? 0;
            hash = HashHelpers.Combine(hash, (int)ConversionKind);
            if (IsChecked)
            {
                hash = HashHelpers.Combine(hash, 1);
            }
 
            hash = HashHelpers.Combine(hash, Type.GetHashCode());
            return hash;
        }
 
        public bool IsEquivalentTo(ICSharpBinder other)
        {
            var otherBinder = other as CSharpConvertBinder;
            if (otherBinder == null)
            {
                return false;
            }
 
            if (ConversionKind != otherBinder.ConversionKind ||
                IsChecked != otherBinder.IsChecked ||
                _callingContext != otherBinder._callingContext ||
                Type != otherBinder.Type)
            {
                return false;
            }
 
            return true;
        }
 
        /// <summary>
        /// Performs the binding of the dynamic convert operation if the target dynamic object cannot bind.
        /// </summary>
        /// <param name="target">The target of the dynamic convert operation.</param>
        /// <param name="errorSuggestion">The binding result to use if binding fails, or null.</param>
        /// <returns>The <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode",
            Justification = "This whole class is unsafe. Constructors are marked as such.")]
        public override DynamicMetaObject FallbackConvert(DynamicMetaObject target, DynamicMetaObject errorSuggestion)
        {
#if ENABLECOMBINDER
            DynamicMetaObject com;
            if (ComInterop.ComBinder.TryConvert(this, target, out com))
            {
                return com;
            }
#else
            BinderHelper.ThrowIfUsingDynamicCom(target);
#endif
 
            BinderHelper.ValidateBindArgument(target, nameof(target));
            return BinderHelper.Bind(this, _binder, new[] { target }, null, errorSuggestion);
        }
    }
}