namespace Azaion.Flights.Infrastructure;

public static class ConfigurationResolver
{
    // Fail-fast contract: missing or whitespace-only values throw at startup so a
    // production deploy without the operator-confirmed values cannot silently
    // accept an insecure default (e.g. a development JWT secret, a localhost DB).
    public static string ResolveRequiredOrThrow(
        IConfiguration configuration,
        string envVar,
        string configKey,
        string humanLabel)
    {
        ArgumentNullException.ThrowIfNull(configuration);

        var value = Environment.GetEnvironmentVariable(envVar);
        if (string.IsNullOrWhiteSpace(value))
            value = configuration[configKey];

        if (string.IsNullOrWhiteSpace(value))
            throw new InvalidOperationException(
                $"{humanLabel} is not configured. Set the {envVar} environment variable " +
                $"or the {configKey} configuration key.");

        return value;
    }
}