// 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;
 
namespace Microsoft.CodeAnalysis.Diagnostics;
 
internal static partial class ReportDiagnosticExtensions
{
    /// <summary>
    /// Returns the equivalent <see cref="DiagnosticSeverity"/> for a <see cref="ReportDiagnostic"/> value.
    /// </summary>
    /// <param name="reportDiagnostic">The <see cref="ReportDiagnostic"/> value.</param>
    /// <returns>
    /// The equivalent <see cref="DiagnosticSeverity"/> for a <see cref="ReportDiagnostic"/> value; otherwise,
    /// <see langword="null"/> if <see cref="DiagnosticSeverity"/> does not contain a direct equivalent for
    /// <paramref name="reportDiagnostic"/>.
    /// </returns>
    /// <exception cref="InvalidOperationException">
    /// If <paramref name="reportDiagnostic"/> is not one of the expected values.
    /// </exception>
    public static DiagnosticSeverity? ToDiagnosticSeverity(this ReportDiagnostic reportDiagnostic)
    {
        switch (reportDiagnostic)
        {
            case ReportDiagnostic.Error:
                return DiagnosticSeverity.Error;
 
            case ReportDiagnostic.Warn:
                return DiagnosticSeverity.Warning;
 
            case ReportDiagnostic.Info:
                return DiagnosticSeverity.Info;
 
            case ReportDiagnostic.Hidden:
                return DiagnosticSeverity.Hidden;
 
            case ReportDiagnostic.Suppress:
            case ReportDiagnostic.Default:
                return null;
 
            default:
                throw ExceptionUtilities.UnexpectedValue(reportDiagnostic);
        }
    }
 
    /// <summary>
    /// Applies a default severity to a <see cref="ReportDiagnostic"/> value.
    /// </summary>
    /// <param name="reportDiagnostic">The <see cref="ReportDiagnostic"/> value.</param>
    /// <param name="defaultSeverity">The default severity.</param>
    /// <returns>
    /// <para>If <paramref name="reportDiagnostic"/> is <see cref="ReportDiagnostic.Default"/>, returns
    /// <paramref name="defaultSeverity"/>.</para>
    /// <para>-or-</para>
    /// <para>Otherwise, returns <paramref name="reportDiagnostic"/> if it has a non-default value.</para>
    /// </returns>
    public static ReportDiagnostic WithDefaultSeverity(this ReportDiagnostic reportDiagnostic, DiagnosticSeverity defaultSeverity)
    {
        if (reportDiagnostic != ReportDiagnostic.Default)
        {
            return reportDiagnostic;
        }
 
        return defaultSeverity.ToReportDiagnostic();
    }
}