// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace Aspire.Hosting.ApplicationModel;
 
/// <summary>
/// A resource that represents a NATS server container.
/// </summary>
/// <param name="name">The name of the resource.</param>
[AspireExport(ExposeProperties = true)]
public class NatsServerResource(string name) : ContainerResource(name), IResourceWithConnectionString
{
    internal const string PrimaryEndpointName = "tcp";
    internal const string PrimaryNatsSchemeName = "nats";
    private const string DefaultUserName = "nats";
 
    private EndpointReference? _primaryEndpoint;
 
    /// <summary>
    /// Initializes a new instance of the <see cref="NatsServerResource"/> class.
    /// </summary>
    /// <param name="name">The name of the resource.</param>
    /// <param name="userName">A parameter that contains the NATS server user name, or <see langword="null"/> to use a default value.</param>
    /// <param name="password">A parameter that contains the NATS server password.</param>
    public NatsServerResource(string name, ParameterResource? userName, ParameterResource? password) : this(name)
    {
        UserNameParameter = userName;
        PasswordParameter = password;
    }
 
    /// <summary>
    /// Gets the primary endpoint for the NATS server.
    /// </summary>
    public EndpointReference PrimaryEndpoint => _primaryEndpoint ??= new(this, PrimaryEndpointName);
 
    /// <summary>
    /// Gets the host endpoint reference for this resource.
    /// </summary>
    public EndpointReferenceExpression Host => PrimaryEndpoint.Property(EndpointProperty.Host);
 
    /// <summary>
    /// Gets the port endpoint reference for this resource.
    /// </summary>
    public EndpointReferenceExpression Port => PrimaryEndpoint.Property(EndpointProperty.Port);
 
    /// <summary>
    /// Gets or sets the user name for the NATS server.
    /// </summary>
    public ParameterResource? UserNameParameter { get; set; }
 
    /// <summary>
    /// Gets a reference to the user name for the NATS server.
    /// </summary>
    /// <remarks>
    /// Returns the user name parameter if specified, otherwise returns the default user name "nats".
    /// </remarks>
    public ReferenceExpression UserNameReference =>
        UserNameParameter is not null ?
            ReferenceExpression.Create($"{UserNameParameter}") :
            ReferenceExpression.Create($"{DefaultUserName}");
 
    /// <summary>
    /// Gets or sets the password for the NATS server.
    /// </summary>
    public ParameterResource? PasswordParameter { get; set; }
 
    /// <summary>
    /// Gets the connection string expression for the NATS server.
    /// </summary>
    public ReferenceExpression ConnectionStringExpression => BuildConnectionString();
 
    /// <summary>
    /// Gets the connection URI expression for the NATS server.
    /// </summary>
    /// <remarks>
    /// Format: <c>nats://[user:password@]{host}:{port}</c>. The credential segment is omitted when no credentials are configured.
    /// </remarks>
    public ReferenceExpression UriExpression => BuildConnectionString();
 
    internal ReferenceExpression BuildConnectionString()
    {
        var builder = new ReferenceExpressionBuilder();
        builder.AppendLiteral($"{PrimaryNatsSchemeName}://");
 
        if (PasswordParameter is not null)
        {
            if (UserNameParameter is not null)
            {
                builder.Append($"{UserNameParameter:uri}:{PasswordParameter:uri}@");
            }
            else
            {
                builder.Append($"{DefaultUserName:uri}:{PasswordParameter:uri}@");
            }
        }
 
        builder.Append($"{PrimaryEndpoint.Property(EndpointProperty.HostAndPort)}");
 
        return builder.Build();
    }
 
    IEnumerable<KeyValuePair<string, ReferenceExpression>> IResourceWithConnectionString.GetConnectionProperties()
    {
        yield return new("Host", ReferenceExpression.Create($"{Host}"));
        yield return new("Port", ReferenceExpression.Create($"{Port}"));
        yield return new("Username", UserNameReference);
 
        if (PasswordParameter is not null)
        {
            yield return new("Password", ReferenceExpression.Create($"{PasswordParameter}"));
        }
 
        yield return new("Uri", UriExpression);
    }
}