namespace SQLInsight.Connectivity;

/// <summary>
/// How to reach one monitored instance.
/// </summary>
public sealed record ConnectionTarget
{
    /// <summary>Server name, <c>host\instance</c> or <c>host,port</c>.</summary>
    public required string Server { get; init; }

    public AuthenticationMode Authentication { get; init; } = AuthenticationMode.Windows;

    /// <summary>SQL login name. Only used with <see cref="AuthenticationMode.SqlLogin"/>.</summary>
    public string? UserName { get; init; }

    /// <summary>SQL login password. Only used with <see cref="AuthenticationMode.SqlLogin"/>.</summary>
    public string? Password { get; init; }

    public ConnectionProvider Provider { get; init; } = ConnectionProvider.Auto;

    /// <summary>
    /// Whether the connection must be encrypted. Mandatory is the default; old unpatched instances that only speak
    /// TLS 1.0 need <see cref="EncryptionMode.Optional"/>, which the agent reports as a warning.
    /// </summary>
    public EncryptionMode Encryption { get; init; } = EncryptionMode.Mandatory;

    /// <summary>Skip certificate validation. Off by default; must be a deliberate choice.</summary>
    public bool TrustServerCertificate { get; init; }

    /// <summary>ODBC driver used for legacy instances.</summary>
    public string OdbcDriver { get; init; } = "ODBC Driver 18 for SQL Server";

    public TimeSpan ConnectTimeout { get; init; } = TimeSpan.FromSeconds(15);

    /// <summary>Entra tenant id, for <see cref="AuthenticationMode.EntraServicePrincipal"/>.</summary>
    public string? TenantId { get; init; }

    public bool UsesEntra => Authentication is AuthenticationMode.EntraManagedIdentity or AuthenticationMode.EntraServicePrincipal or AuthenticationMode.EntraDefault;
}

public enum AuthenticationMode
{
    /// <summary>Integrated security. Preferred on-prem; run the agent as a gMSA.</summary>
    Windows,
    SqlLogin,

    /// <summary>Microsoft Entra ID with the agent's managed identity (Azure VM). <see cref="ConnectionTarget.UserName"/> may hold a user-assigned identity's client id.</summary>
    EntraManagedIdentity,

    /// <summary>Microsoft Entra ID service principal: <see cref="ConnectionTarget.UserName"/> = client id, <see cref="ConnectionTarget.Password"/> = secret.</summary>
    EntraServicePrincipal,

    /// <summary>Microsoft Entra ID via the default credential chain (environment, managed identity, Azure CLI …).</summary>
    EntraDefault,
}

public enum ConnectionProvider
{
    /// <summary>Try Microsoft.Data.SqlClient, fall back to ODBC when the instance is too old for it.</summary>
    Auto,
    SqlClient,
    Odbc,
}

public enum EncryptionMode
{
    Mandatory,
    Optional,
}