// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Globalization;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
 
namespace SourceGenerators;
 
internal static class CSharpSyntaxUtilities
{
    // Standard format for double and single on non-inbox frameworks to ensure value is round-trippable.
    public const string DoubleFormatString = "G17";
    public const string SingleFormatString = "G9";
 
    // Format a literal in C# format -- works around https://github.com/dotnet/roslyn/issues/58705
    public static string FormatLiteral(object? value, TypeRef type)
    {
        if (value == null)
        {
            return $"default({type.FullyQualifiedName})";
        }
 
        switch (value)
        {
            case string @string:
                return SymbolDisplay.FormatLiteral(@string, quote: true);
            case char @char:
                return SymbolDisplay.FormatLiteral(@char, quote: true);
            case double.NegativeInfinity:
                return "double.NegativeInfinity";
            case double.PositiveInfinity:
                return "double.PositiveInfinity";
            case double.NaN:
                return "double.NaN";
            case double @double:
                return $"{@double.ToString(DoubleFormatString, CultureInfo.InvariantCulture)}D";
            case float.NegativeInfinity:
                return "float.NegativeInfinity";
            case float.PositiveInfinity:
                return "float.PositiveInfinity";
            case float.NaN:
                return "float.NaN";
            case float @float:
                return $"{@float.ToString(SingleFormatString, CultureInfo.InvariantCulture)}F";
            case decimal @decimal:
                // we do not need to specify a format string for decimal as it's default is round-trippable on all frameworks.
                return $"{@decimal.ToString(CultureInfo.InvariantCulture)}M";
            case bool @bool:
                return @bool ? "true" : "false";
            default:
                // Assume this is a number.
                return FormatNumber();
        }
 
        string FormatNumber() => $"({type.FullyQualifiedName})({Convert.ToString(value, CultureInfo.InvariantCulture)})";
    }
}