// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;

namespace System.Xml.Xsl
{
    [DebuggerDisplay("({Line},{Pos})")]
    internal readonly struct Location
    {
        private readonly ulong _value;

        public int Line { get { return (int)(_value >> 32); } }
        public int Pos { get { return unchecked((int)(_value)); } }

        public Location(int line, int pos)
        {
            _value = (((ulong)line) << 32) | (uint)pos;
        }

        public bool LessOrEqual(Location that)
        {
            return _value <= that._value;
        }
    }

    [DebuggerDisplay("{Uri} [{StartLine},{StartPos} -- {EndLine},{EndPos}]")]
    internal sealed class SourceLineInfo : ISourceLineInfo
    {
        private readonly string? uriString;
        private readonly Location start;
        private readonly Location end;

        public SourceLineInfo(string? uriString, int startLine, int startPos, int endLine, int endPos)
            : this(uriString, new Location(startLine, startPos), new Location(endLine, endPos))
        { }

        public SourceLineInfo(string? uriString, Location start, Location end)
        {
            this.uriString = uriString;
            this.start = start;
            this.end = end;
            Validate(this);
        }

        public string? Uri { get { return this.uriString; } }
        public int StartLine { get { return this.start.Line; } }
        public Location End { get { return this.end; } }
        public Location Start { get { return this.start; } }

        /// <summary>
        /// Magic number 0xfeefee is used in PDB to denote a section of IL that does not map to any user code.
        /// When VS debugger steps into IL marked with 0xfeefee, it will continue the step until it reaches
        /// some user code.
        /// </summary>
        private const int NoSourceMagicNumber = 0xfeefee;

        public static readonly SourceLineInfo NoSource = new SourceLineInfo(string.Empty, NoSourceMagicNumber, 0, NoSourceMagicNumber, 0);

        public bool IsNoSource
        {
            get { return this.StartLine == NoSourceMagicNumber; }
        }

        [Conditional("DEBUG")]
        public static void Validate(ISourceLineInfo lineInfo)
        {
            if (lineInfo.Start.Line == 0 || lineInfo.Start.Line == NoSourceMagicNumber)
            {
                Debug.Assert(lineInfo.Start.Line == lineInfo.End.Line);
                Debug.Assert(lineInfo.Start.Pos == 0 && lineInfo.End.Pos == 0);
            }
            else
            {
                Debug.Assert(0 < lineInfo.Start.Line && 0 < lineInfo.Start.Pos, "0 < start");
                Debug.Assert(0 < lineInfo.End.Line && 0 < lineInfo.End.Pos, "0 < end");
                Debug.Assert(lineInfo.Start.LessOrEqual(lineInfo.End), "start <= end");
            }
        }

        // Returns file path for local and network URIs. Used for PDB generating and error reporting.
        public static string GetFileName(string uriString)
        {
            Debug.Assert(uriString != null);
            Uri? uri;

            if (uriString.Length != 0 &&
                System.Uri.TryCreate(uriString, UriKind.Absolute, out uri) &&
                uri.IsFile
            )
            {
                return uri.LocalPath;
            }
            return uriString;
        }
    }
}