// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Diagnostics;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp
{
    /// <summary>
    /// Information to be deduced while binding a foreach loop so that the loop can be lowered
    /// to a while over an enumerator.  Not applicable to the array or string forms.
    /// </summary>
    internal sealed class ForEachEnumeratorInfo
    {
        // Types identified by the algorithm in the spec (8.8.4).
        public readonly TypeSymbol CollectionType;
 
        public readonly WellKnownType InlineArraySpanType;
        public readonly bool InlineArrayUsedAsValue;
 
        // public readonly TypeSymbol EnumeratorType; // redundant - return type of GetEnumeratorMethod
        public readonly TypeWithAnnotations ElementTypeWithAnnotations;
        public TypeSymbol ElementType => ElementTypeWithAnnotations.Type;
 
        // Members required by the "pattern" based approach.  Also populated for other approaches.
        public readonly MethodArgumentInfo GetEnumeratorInfo;
        public readonly MethodSymbol CurrentPropertyGetter;
        public readonly MethodArgumentInfo MoveNextInfo;
        public readonly BoundAwaitableInfo? MoveNextAwaitableInfo;
 
        // True if the enumerator needs disposal once used. 
        // Will be either IDisposable/IAsyncDisposable, or use DisposeMethod below if set
        // Computed during initial binding so that we can expose it in the semantic model.
        public readonly bool NeedsDisposal;
 
        /// <summary>
        /// True if this was written as an 'await foreach'. This does not guarantee that <see cref="MoveNextAwaitableInfo"/> is not null, as there
        /// may be other errors.
        /// </summary>
        public readonly bool IsAsync;
 
        // When async and needs disposal, this stores the information to await the DisposeAsync() invocation
        public readonly BoundAwaitableInfo? DisposeAwaitableInfo;
 
        // When using pattern-based Dispose, this stores the method to invoke to Dispose
        public readonly MethodArgumentInfo? PatternDisposeInfo;
 
        // Conversions that will be required when the foreach is lowered.
        public readonly BoundValuePlaceholder? CurrentPlaceholder;
        public readonly BoundExpression? CurrentConversion; // current to element type
 
        public readonly BinderFlags Location;
 
        private ForEachEnumeratorInfo(
            TypeSymbol collectionType,
            WellKnownType inlineArraySpanType,
            bool inlineArrayUsedAsValue,
            TypeWithAnnotations elementType,
            MethodArgumentInfo getEnumeratorInfo,
            MethodSymbol currentPropertyGetter,
            MethodArgumentInfo moveNextInfo,
            BoundAwaitableInfo? moveNextAwaitableInfo,
            bool isAsync,
            bool needsDisposal,
            BoundAwaitableInfo? disposeAwaitableInfo,
            MethodArgumentInfo? patternDisposeInfo,
            BoundValuePlaceholder? currentPlaceholder,
            BoundExpression? currentConversion,
            BinderFlags location)
        {
            RoslynDebug.Assert((object)collectionType != null, $"Field '{nameof(collectionType)}' cannot be null");
            RoslynDebug.Assert(elementType.HasType, $"Field '{nameof(elementType)}' cannot be null");
            RoslynDebug.Assert((object)getEnumeratorInfo != null, $"Field '{nameof(getEnumeratorInfo)}' cannot be null");
            RoslynDebug.Assert((object)currentPropertyGetter != null, $"Field '{nameof(currentPropertyGetter)}' cannot be null");
            RoslynDebug.Assert((object)moveNextInfo != null, $"Field '{nameof(moveNextInfo)}' cannot be null");
            Debug.Assert(patternDisposeInfo == null || needsDisposal);
            Debug.Assert(inlineArraySpanType is WellKnownType.Unknown or WellKnownType.System_Span_T or WellKnownType.System_ReadOnlySpan_T);
            Debug.Assert(inlineArraySpanType == WellKnownType.Unknown ||
                         (collectionType.HasInlineArrayAttribute(out _) && collectionType.TryGetInlineArrayElementField() is FieldSymbol elementField && elementType.Equals(elementField.TypeWithAnnotations, TypeCompareKind.ConsiderEverything)));
            Debug.Assert(!inlineArrayUsedAsValue || inlineArraySpanType != WellKnownType.Unknown);
            Debug.Assert(!isAsync || moveNextAwaitableInfo != null);
 
            this.CollectionType = collectionType;
            this.InlineArraySpanType = inlineArraySpanType;
            this.InlineArrayUsedAsValue = inlineArrayUsedAsValue;
            this.ElementTypeWithAnnotations = elementType;
            this.GetEnumeratorInfo = getEnumeratorInfo;
            this.CurrentPropertyGetter = currentPropertyGetter;
            this.MoveNextInfo = moveNextInfo;
            this.MoveNextAwaitableInfo = moveNextAwaitableInfo;
            this.IsAsync = isAsync;
            this.NeedsDisposal = needsDisposal;
            this.DisposeAwaitableInfo = disposeAwaitableInfo;
            this.PatternDisposeInfo = patternDisposeInfo;
            this.CurrentPlaceholder = currentPlaceholder;
            this.CurrentConversion = currentConversion;
            this.Location = location;
        }
 
        // Mutable version of ForEachEnumeratorInfo.  Convert to immutable using Build.
        internal struct Builder
        {
            public TypeSymbol CollectionType;
            public bool ViaExtensionMethod;
            public WellKnownType InlineArraySpanType;
            public bool InlineArrayUsedAsValue;
            public TypeWithAnnotations ElementTypeWithAnnotations;
            public TypeSymbol ElementType => ElementTypeWithAnnotations.Type;
 
            public MethodArgumentInfo? GetEnumeratorInfo;
            public MethodSymbol CurrentPropertyGetter;
            public MethodArgumentInfo? MoveNextInfo;
            public BoundAwaitableInfo? MoveNextAwaitableInfo;
 
            public bool IsAsync;
            public bool NeedsDisposal;
            public BoundAwaitableInfo? DisposeAwaitableInfo;
            public MethodArgumentInfo? PatternDisposeInfo;
 
            public BoundValuePlaceholder? CurrentPlaceholder;
            public BoundExpression? CurrentConversion;
 
            public ForEachEnumeratorInfo Build(BinderFlags location)
            {
                Debug.Assert((object)CollectionType != null, $"'{nameof(CollectionType)}' cannot be null");
                Debug.Assert((object)ElementType != null, $"'{nameof(ElementType)}' cannot be null");
                Debug.Assert(GetEnumeratorInfo != null, $"'{nameof(GetEnumeratorInfo)}' cannot be null");
 
                Debug.Assert(MoveNextInfo != null);
                Debug.Assert(CurrentPropertyGetter != null);
 
                return new ForEachEnumeratorInfo(
                    CollectionType,
                    InlineArraySpanType,
                    InlineArrayUsedAsValue,
                    ElementTypeWithAnnotations,
                    GetEnumeratorInfo,
                    CurrentPropertyGetter,
                    MoveNextInfo,
                    MoveNextAwaitableInfo,
                    IsAsync,
                    NeedsDisposal,
                    DisposeAwaitableInfo,
                    PatternDisposeInfo,
                    CurrentPlaceholder,
                    CurrentConversion,
                    location);
            }
 
            public bool IsIncomplete
                => GetEnumeratorInfo is null || MoveNextInfo is null || CurrentPropertyGetter is null;
        }
    }
}