namespace OpenNest.Server;

/// <summary>Startup settings read from the command line and environment.</summary>
public static class ServerOptions
{
    public const string DatabaseVariable = "OPENNEST_DB";

    /// <summary>
    /// The database path: <c>--database=&lt;path&gt;</c> or <c>--database &lt;path&gt;</c>, then
    /// <c>OPENNEST_DB</c>, then <c>./data/nests.db</c>. A <c>--database</c> without a path,
    /// or given twice, fails startup instead of silently storing nests elsewhere.
    /// </summary>
    public static string DatabasePath(IReadOnlyList<string> args, string? environmentPath)
    {
        string? path = null;
        for (var i = 0; i < args.Count; i++)
        {
            string value;
            if (args[i] == "--database")
            {
                if (i + 1 >= args.Count || args[i + 1].StartsWith("--", StringComparison.Ordinal))
                    throw new ArgumentException("--database requires a path.", nameof(args));
                value = args[++i];
            }
            else if (args[i].StartsWith("--database=", StringComparison.Ordinal))
            {
                value = args[i]["--database=".Length..];
            }
            else
            {
                continue;
            }

            if (string.IsNullOrWhiteSpace(value))
                throw new ArgumentException("--database requires a path.", nameof(args));
            if (path is not null)
                throw new ArgumentException("--database was given more than once.", nameof(args));
            path = value;
        }

        return path ?? environmentPath ?? Path.Combine("data", "nests.db");
    }
}