missions/Infrastructure/ConfigurationResolver.cs

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;
    }

    // Optional positive-integer override (e.g. JWKS refresh interval tuning for tests).
    // Returns null when unset/whitespace so callers keep library defaults.
    // Throws when set-but-unparseable or non-positive, so a typo can never silently
    // weaken behavior.
    public static int? ResolveOptionalPositiveIntOrThrow(
        IConfiguration configuration,
        string envVar,
        string configKey,
        string humanLabel)
    {
        ArgumentNullException.ThrowIfNull(configuration);

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

        if (string.IsNullOrWhiteSpace(raw))
            return null;

        if (!int.TryParse(raw, System.Globalization.NumberStyles.Integer, System.Globalization.CultureInfo.InvariantCulture, out var parsed) || parsed <= 0)
        {
            throw new InvalidOperationException(
                $"{humanLabel} is set to '{raw}' which is not a positive integer. " +
                $"Set {envVar} (or {configKey}) to a positive integer count of seconds, or unset it to use the library default.");
        }

        return parsed;
    }
}