// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Aspire.Hosting.ApplicationModel;
 
namespace Aspire.Hosting.Utils;
 
internal static class VolumeNameGenerator
{
    /// <summary>
    /// Creates a volume name with the form <c>$"{applicationName}-{resourceName}-{suffix}</c>, e.g. <c>"myapplication-postgres-data"</c>.
    /// </summary>
    /// <remarks>
    /// If the application name contains chars that are invalid for a volume name, the prefix <c>"volume-"</c> will be used instead.
    /// </remarks>
    public static string CreateVolumeName<T>(IResourceBuilder<T> builder, string suffix) where T : IResource
    {
        if (!HasOnlyValidChars(suffix))
        {
            throw new ArgumentException($"The suffix '{suffix}' contains invalid characters. Only [a-zA-Z0-9_.-] are allowed.", nameof(suffix));
        }
 
        // Create volume name like "myapplication-postgres-data"
        var applicationName = builder.ApplicationBuilder.Environment.ApplicationName;
        var resourceName = builder.Resource.Name;
        return $"{(HasOnlyValidChars(applicationName) ? applicationName : "volume")}-{resourceName}-{suffix}";
    }
 
    private static bool HasOnlyValidChars(string name)
    {
        // According to the error message from docker CLI, volume names must be of form "[a-zA-Z0-9][a-zA-Z0-9_.-]"
        var nameSpan = name.AsSpan();
 
        for (var i = 0; i < nameSpan.Length; i++)
        {
            var c = nameSpan[i];
 
            if (i == 0 && !(Char.IsAsciiLetter(c) || Char.IsNumber(c)))
            {
                // First char must be a letter or number
                return false;
            }
            else if (!(Char.IsAsciiLetter(c) || Char.IsNumber(c) || c == '_' || c == '.' || c == '-'))
            {
                // Subsequent chars must be a letter, number, underscore, period, or hyphen
                return false;
            }
        }
 
        return true;
    }
}