// 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.Collections.Immutable;
using System.Diagnostics;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.CSharp
{
    /// <summary>
    /// The dynamic operation factories below return this struct so that the caller
    /// have the option of separating the call-site initialization from its invocation.
    /// 
    /// Most callers just call <see cref="ToExpression"/> to get the combo but some (object and array initializers) 
    /// hoist all call-site initialization code and emit multiple invocations of the same site.
    /// </summary>
    internal readonly struct LoweredDynamicOperation
    {
        private readonly SyntheticBoundNodeFactory? _factory;
        private readonly TypeSymbol _resultType;
        private readonly ImmutableArray<LocalSymbol> _temps;
        public readonly BoundExpression? SiteInitialization;
        public readonly BoundExpression SiteInvocation;

        public LoweredDynamicOperation(SyntheticBoundNodeFactory? factory, BoundExpression? siteInitialization, BoundExpression siteInvocation, TypeSymbol resultType, ImmutableArray<LocalSymbol> temps)
        {
            _factory = factory;
            _resultType = resultType;
            _temps = temps;
            this.SiteInitialization = siteInitialization;
            this.SiteInvocation = siteInvocation;
        }

        public static LoweredDynamicOperation Bad(
            BoundExpression? loweredReceiver,
            ImmutableArray<BoundExpression> loweredArguments,
            BoundExpression? loweredRight,
            TypeSymbol resultType)
        {
            var children = ArrayBuilder<BoundExpression>.GetInstance();
            children.AddIfNotNull(loweredReceiver);
            children.AddRange(loweredArguments);
            children.AddIfNotNull(loweredRight);

            return LoweredDynamicOperation.Bad(resultType, children.ToImmutableAndFree());
        }

        public static LoweredDynamicOperation Bad(TypeSymbol resultType, ImmutableArray<BoundExpression> children)
        {
            Debug.Assert(children.Length > 0);
            var bad = new BoundBadExpression(children[0].Syntax, LookupResultKind.Empty, ImmutableArray<Symbol?>.Empty, children, resultType);
            return new LoweredDynamicOperation(null, null, bad, resultType, default(ImmutableArray<LocalSymbol>));
        }

        public BoundExpression ToExpression()
        {
            if (_factory == null)
            {
                Debug.Assert(SiteInitialization == null && SiteInvocation is BoundBadExpression && _temps.IsDefaultOrEmpty);
                return SiteInvocation;
            }

            // TODO (tomat): we might be able to use SiteInvocation.Type instead of resultType once we stop using GetLoweredType
            Debug.Assert(SiteInitialization is { });
            if (_temps.IsDefaultOrEmpty)
            {
                return _factory.Sequence(new[] { SiteInitialization }, SiteInvocation, _resultType);
            }
            else
            {
                return new BoundSequence(_factory.Syntax, _temps, ImmutableArray.Create(SiteInitialization), SiteInvocation, _resultType) { WasCompilerGenerated = true };
            }
        }
    }
}