// 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;
using System.Diagnostics;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.EditAndContinue;

[DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
internal readonly struct NonRemappableRegion(SourceFileSpan oldSpan, SourceFileSpan newSpan, bool isExceptionRegion) : IEquatable<NonRemappableRegion>
{
    /// <summary>
    /// PDB span in pre-remap method version.
    /// </summary>
    /// <remarks>
    /// When a thread is executing in an old version of a method before it is remapped to the new version
    /// its active statement needs to be mapped from <see cref="OldSpan"/> in the old version 
    /// to <see cref="NewSpan"/> in the new version of the method.
    /// </remarks>
    public readonly SourceFileSpan OldSpan = oldSpan;

    /// <summary>
    /// PDB span in the new method version.
    /// </summary>
    public readonly SourceFileSpan NewSpan = newSpan;

    /// <summary>
    /// True if the region represents an exception region, false if it represents an active statement.
    /// </summary>
    public readonly bool IsExceptionRegion = isExceptionRegion;

    public override bool Equals(object? obj)
        => obj is NonRemappableRegion region && Equals(region);

    public bool Equals(NonRemappableRegion other)
        => OldSpan.Equals(other.OldSpan) &&
           NewSpan.Equals(other.NewSpan) &&
           IsExceptionRegion == other.IsExceptionRegion;

    public override int GetHashCode()
        => Hash.Combine(OldSpan.GetHashCode(), Hash.Combine(IsExceptionRegion, NewSpan.GetHashCode()));

    public static bool operator ==(NonRemappableRegion left, NonRemappableRegion right)
        => left.Equals(right);

    public static bool operator !=(NonRemappableRegion left, NonRemappableRegion right)
        => !(left == right);

    public NonRemappableRegion WithNewSpan(SourceFileSpan newSpan)
        => new(OldSpan, newSpan, IsExceptionRegion);

    internal string GetDebuggerDisplay()
        => $"{(IsExceptionRegion ? "ER" : "AS")} {OldSpan} => {NewSpan.Span}";
}