#if NET20 || NET30 || !NET_4_6

// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System.Diagnostics;
using System.Dynamic.Utils;

namespace System.Linq.Expressions.Reimplement
{
    /// <summary>
    /// Emits or clears a sequence point for debug information.
    ///
    /// This allows the debugger to highlight the correct source code when
    /// debugging.
    /// </summary>
    [DebuggerTypeProxy(typeof(DebugInfoExpressionProxy))]
    public class DebugInfoExpression : Expression
    {
        private readonly SymbolDocumentInfo _document;

        internal DebugInfoExpression(SymbolDocumentInfo document)
        {
            _document = document;
        }

        /// <summary>
        /// Gets the static type of the expression that this <see cref="Expression" /> represents. (Inherited from <see cref="Expression"/>.)
        /// </summary>
        /// <returns>The <see cref="Type"/> that represents the static type of the expression.</returns>
        public sealed override Type Type
        {
            get { return typeof(void); }
        }

        /// <summary>
        /// Returns the node type of this <see cref="Expression" />. (Inherited from <see cref="Expression" />.)
        /// </summary>
        /// <returns>The <see cref="ExpressionType"/> that represents this expression.</returns>
        public sealed override ExpressionType NodeType
        {
            get { return ExpressionType.DebugInfo; }
        }

        /// <summary>
        /// Gets the start line of this <see cref="DebugInfoExpression" />.
        /// </summary>
        public virtual int StartLine
        {
            get { throw ContractUtils.Unreachable; }
        }

        /// <summary>
        /// Gets the start column of this <see cref="DebugInfoExpression" />.
        /// </summary>
        public virtual int StartColumn
        {
            get { throw ContractUtils.Unreachable; }
        }

        /// <summary>
        /// Gets the end line of this <see cref="DebugInfoExpression" />.
        /// </summary>
        public virtual int EndLine
        {
            get { throw ContractUtils.Unreachable; }
        }

        /// <summary>
        /// Gets the end column of this <see cref="DebugInfoExpression" />.
        /// </summary>
        public virtual int EndColumn
        {
            get { throw ContractUtils.Unreachable; }
        }

        /// <summary>
        /// Gets the <see cref="SymbolDocumentInfo"/> that represents the source file.
        /// </summary>
        public SymbolDocumentInfo Document
        {
            get { return _document; }
        }

        /// <summary>
        /// Gets the value to indicate if the <see cref="DebugInfoExpression"/> is for clearing a sequence point.
        /// </summary>
        public virtual bool IsClear
        {
            get { throw ContractUtils.Unreachable; }
        }

        protected internal override Expression Accept(ExpressionVisitor visitor)
        {
            return visitor.VisitDebugInfo(this);
        }
    }

    #region Specialized subclasses

    internal sealed class SpanDebugInfoExpression : DebugInfoExpression
    {
        private readonly int _startLine, _startColumn, _endLine, _endColumn;

        internal SpanDebugInfoExpression(SymbolDocumentInfo document, int startLine, int startColumn, int endLine, int endColumn)
            : base(document)
        {
            _startLine = startLine;
            _startColumn = startColumn;
            _endLine = endLine;
            _endColumn = endColumn;
        }

        public override int StartLine
        {
            get { return _startLine; }
        }

        public override int StartColumn
        {
            get { return _startColumn; }
        }

        public override int EndLine
        {
            get { return _endLine; }
        }

        public override int EndColumn
        {
            get { return _endColumn; }
        }

        public override bool IsClear
        {
            get { return false; }
        }

        protected internal override Expression Accept(ExpressionVisitor visitor)
        {
            return visitor.VisitDebugInfo(this);
        }
    }

    internal sealed class ClearDebugInfoExpression : DebugInfoExpression
    {
        internal ClearDebugInfoExpression(SymbolDocumentInfo document)
            : base(document)
        {
        }

        public override bool IsClear
        {
            get { return true; }
        }

        public override int StartLine
        {
            get { return 0xfeefee; }
        }

        public override int StartColumn
        {
            get { return 0; }
        }

        public override int EndLine
        {
            get { return 0xfeefee; }
        }

        public override int EndColumn
        {
            get { return 0; }
        }
    }

    #endregion Specialized subclasses

    public partial class Expression
    {
        /// <summary>
        /// Creates a <see cref="DebugInfoExpression"/> with the specified span.
        /// </summary>
        /// <param name="document">The <see cref="SymbolDocumentInfo"/> that represents the source file.</param>
        /// <param name="startLine">The start line of this <see cref="DebugInfoExpression" />. Must be greater than 0.</param>
        /// <param name="startColumn">The start column of this <see cref="DebugInfoExpression" />. Must be greater than 0.</param>
        /// <param name="endLine">The end line of this <see cref="DebugInfoExpression" />. Must be greater or equal than the start line.</param>
        /// <param name="endColumn">The end column of this <see cref="DebugInfoExpression" />. If the end line is the same as the start line, it must be greater or equal than the start column. In any case, must be greater than 0.</param>
        /// <returns>An instance of <see cref="DebugInfoExpression"/>.</returns>
        public static DebugInfoExpression DebugInfo(SymbolDocumentInfo document, int startLine, int startColumn, int endLine, int endColumn)
        {
            ContractUtils.RequiresNotNull(document, "document");
            if (startLine == 0xfeefee && startColumn == 0 && endLine == 0xfeefee && endColumn == 0)
            {
                return new ClearDebugInfoExpression(document);
            }

            ValidateSpan(startLine, startColumn, endLine, endColumn);
            return new SpanDebugInfoExpression(document, startLine, startColumn, endLine, endColumn);
        }

        /// <summary>
        /// Creates a <see cref="DebugInfoExpression"/> for clearing a sequence point.
        /// </summary>
        /// <param name="document">The <see cref="SymbolDocumentInfo"/> that represents the source file.</param>
        /// <returns>An instance of <see cref="DebugInfoExpression"/> for clearning a sequence point.</returns>
        public static DebugInfoExpression ClearDebugInfo(SymbolDocumentInfo document)
        {
            ContractUtils.RequiresNotNull(document, "document");

            return new ClearDebugInfoExpression(document);
        }

        private static void ValidateSpan(int startLine, int startColumn, int endLine, int endColumn)
        {
            if (startLine < 1)
            {
                throw Error.OutOfRange("startLine", 1);
            }
            if (startColumn < 1)
            {
                throw Error.OutOfRange("startColumn", 1);
            }
            if (endLine < 1)
            {
                throw Error.OutOfRange("endLine", 1);
            }
            if (endColumn < 1)
            {
                throw Error.OutOfRange("endColumn", 1);
            }
            if (startLine > endLine)
            {
                throw Error.StartEndMustBeOrdered();
            }
            if (startLine == endLine && startColumn > endColumn)
            {
                throw Error.StartEndMustBeOrdered();
            }
        }
    }
}

#endif