// 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.

#nullable disable

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

namespace Microsoft.CodeAnalysis.CSharp
{
    internal sealed class ForLoopBinder : LoopBinder
    {
        private readonly ForStatementSyntax _syntax;

        public ForLoopBinder(Binder enclosing, ForStatementSyntax syntax)
            : base(enclosing, syntax)
        {
            Debug.Assert(syntax != null);
            _syntax = syntax;
        }

        protected override ImmutableArray<LocalSymbol> BuildLocals()
        {
            var locals = ArrayBuilder<LocalSymbol>.GetInstance();

            // Declaration and Initializers are mutually exclusive.
            if (_syntax.Declaration != null)
            {
                _syntax.Declaration.Type.VisitRankSpecifiers((rankSpecifier, args) =>
                {
                    foreach (var size in rankSpecifier.Sizes)
                    {
                        if (size.Kind() != SyntaxKind.OmittedArraySizeExpression)
                        {
                            ExpressionVariableFinder.FindExpressionVariables(args.binder, args.locals, size);
                        }
                    }
                }, (binder: this, locals: locals));

                foreach (var vdecl in _syntax.Declaration.Variables)
                {
                    var localSymbol = MakeLocal(_syntax.Declaration, vdecl, LocalDeclarationKind.RegularVariable, allowScoped: true);
                    locals.Add(localSymbol);

                    // also gather expression-declared variables from the bracketed argument lists and the initializers
                    ExpressionVariableFinder.FindExpressionVariables(this, locals, vdecl);
                }
            }
            else
            {
                ExpressionVariableFinder.FindExpressionVariables(this, locals, _syntax.Initializers);
            }

            return locals.ToImmutableAndFree();
        }

        internal override BoundForStatement BindForParts(BindingDiagnosticBag diagnostics, Binder originalBinder)
        {
            BoundForStatement result = BindForParts(_syntax, originalBinder, diagnostics);
            return result;
        }

        private BoundForStatement BindForParts(ForStatementSyntax node, Binder originalBinder, BindingDiagnosticBag diagnostics)
        {
            BoundStatement initializer;
            // Declaration and Initializers are mutually exclusive.
            if (_syntax.Declaration != null)
            {
                var type = _syntax.Declaration.Type.SkipScoped(out _);

                if (type is RefTypeSyntax)
                {
                    // Checking for 'ref for' (7.3) automatically checks for 'ref' (7.0), so no need for an explicit
                    // check feature as well here.
                    MessageID.IDS_FeatureRefFor.CheckFeatureAvailability(diagnostics, type);
                }

                initializer = originalBinder.BindForOrUsingOrFixedDeclarations(node.Declaration, LocalDeclarationKind.RegularVariable, diagnostics, out _);
            }
            else
            {
                initializer = originalBinder.BindStatementExpressionList(node.Initializers, diagnostics);
            }

            BoundExpression condition = null;
            var innerLocals = ImmutableArray<LocalSymbol>.Empty;
            ExpressionSyntax conditionSyntax = node.Condition;
            if (conditionSyntax != null)
            {
                originalBinder = originalBinder.GetBinder(conditionSyntax);
                condition = originalBinder.BindBooleanExpression(conditionSyntax, diagnostics);
                innerLocals = originalBinder.GetDeclaredLocalsForScope(conditionSyntax);
            }

            BoundStatement increment = null;
            SeparatedSyntaxList<ExpressionSyntax> incrementors = node.Incrementors;
            if (incrementors.Count > 0)
            {
                var scopeDesignator = incrementors.First();
                var incrementBinder = originalBinder.GetBinder(scopeDesignator);
                increment = incrementBinder.BindStatementExpressionList(incrementors, diagnostics);
                Debug.Assert(increment.Kind != BoundKind.StatementList || ((BoundStatementList)increment).Statements.Length > 1);

                var locals = incrementBinder.GetDeclaredLocalsForScope(scopeDesignator);
                if (!locals.IsEmpty)
                {
                    if (increment.Kind == BoundKind.StatementList)
                    {
                        increment = new BoundBlock(scopeDesignator, locals, ((BoundStatementList)increment).Statements)
                        { WasCompilerGenerated = true };
                    }
                    else
                    {
                        increment = new BoundBlock(increment.Syntax, locals, ImmutableArray.Create(increment))
                        { WasCompilerGenerated = true };
                    }
                }
            }

            var body = originalBinder.BindPossibleEmbeddedStatement(node.Statement, diagnostics);

            Debug.Assert(this.Locals == this.GetDeclaredLocalsForScope(node));
            return new BoundForStatement(node,
                                         this.Locals,
                                         initializer,
                                         innerLocals,
                                         condition,
                                         increment,
                                         body,
                                         this.BreakLabel,
                                         this.ContinueLabel);
        }

        internal override ImmutableArray<LocalSymbol> GetDeclaredLocalsForScope(SyntaxNode scopeDesignator)
        {
            if (_syntax == scopeDesignator)
            {
                return this.Locals;
            }

            throw ExceptionUtilities.Unreachable();
        }

        internal override ImmutableArray<LocalFunctionSymbol> GetDeclaredLocalFunctionsForScope(CSharpSyntaxNode scopeDesignator)
        {
            throw ExceptionUtilities.Unreachable();
        }

        internal override SyntaxNode ScopeDesignator
        {
            get
            {
                return _syntax;
            }
        }
    }
}