Configuration System

/**
 * Main configuration interface providing access to configuration sections and options
 */
interface Config {
    /** Get all available configuration section names */
    Set<String> getSectionNames();
    
    /** Get all options available in a specific section */
    Set<String> getOptions(String section);
    
    /** Get all values for a section/option pair (supports multi-value options) */
    Optional<List<String>> getAll(String section, String option);
    
    /** Get single string value for a section/option pair */
    Optional<String> get(String section, String option);
    
    /** Get integer value with automatic type conversion */
    Optional<Integer> getInt(String section, String option);
    
    /** Get boolean value with automatic type conversion */
    Optional<Boolean> getBool(String section, String option);
    
    /** Get array values (nested lists) */
    Optional<List<List<String>>> getArray(String section, String option);
    
    /** Get class instance with automatic instantiation */
    <X> X getClass(String section, String option, Class<X> typeOfClass, String defaultClazz);
}

Config config = new TomlConfig(Paths.get("grid.toml"));

// Get string values
Optional<String> hubHost = config.get("server", "host");
String host = hubHost.orElse("localhost");

// Get typed values
int port = config.getInt("server", "port").orElse(4444);
boolean enableTracing = config.getBool("tracing", "enable").orElse(false);

// Instantiate classes
EventBus eventBus = config.getClass("events", "implementation", 
                                   EventBus.class, "org.openqa.selenium.events.local.GuavaEventBus");

/**
 * Represents a grid component role (e.g., hub, node, distributor)
 */
class Role implements Comparable<Role> {
    /** Create a new role with the specified name */
    Role(String roleName);
    
    /** Factory method to create or retrieve a role */
    static Role of(String name);
    
    /** Get the role name */
    String getRoleName();
    
    /** Compare roles for ordering */
    int compareTo(Role o);
    
    // Standard equals/hashCode implementations
    boolean equals(Object o);
    int hashCode();
}

/**
 * Standard grid roles used by default components
 */
class StandardGridRoles {
    static final Role DISTRIBUTOR_ROLE = Role.of("distributor");
    static final Role EVENT_BUS_ROLE = Role.of("events");
    static final Role HTTPD_ROLE = Role.of("server");
    static final Role NODE_ROLE = Role.of("node");
    static final Role ROUTER_ROLE = Role.of("router");
    static final Role SESSION_MAP_ROLE = Role.of("sessions");
    static final Role SESSION_QUEUE_ROLE = Role.of("sessionqueue");
    
    /** Complete set of all standard roles */
    static final Set<Role> ALL_ROLES = Set.of(
        DISTRIBUTOR_ROLE, EVENT_BUS_ROLE, HTTPD_ROLE, NODE_ROLE,
        ROUTER_ROLE, SESSION_MAP_ROLE, SESSION_QUEUE_ROLE
    );
}

/**
 * Interface for components that have associated roles
 */
interface HasRoles {
    /** Get the roles this component is associated with */
    Set<Role> getRoles();
}

/**
 * Environment variable-based configuration
 */
class EnvConfig implements Config {
    EnvConfig();
    // Reads from system environment variables with SE_ prefix
}

/**
 * Map-based configuration for programmatic setup
 */
class MapConfig implements Config {
    MapConfig(Map<String, Object> raw);
}

/**
 * JSON file-based configuration  
 */
class JsonConfig implements Config {
    JsonConfig(Path path) throws IOException;
    JsonConfig(Reader reader) throws IOException;
}

/**
 * TOML file-based configuration
 */
class TomlConfig implements Config {
    TomlConfig(Path path) throws IOException;
    TomlConfig(Reader reader) throws IOException;
}

/**
 * Annotation-based configuration using reflection
 */
class AnnotatedConfig implements Config {
    AnnotatedConfig(Object annotatedObject);
}

/**
 * Combines multiple configuration sources with precedence
 */
class CompoundConfig implements Config {
    CompoundConfig(Config... configs);
    // First config in array has highest precedence
}

/**
 * Caching wrapper that memoizes configuration values
 */
class MemoizedConfig implements Config {
    MemoizedConfig(Config delegate);
}

// Combine multiple configuration sources
Config config = new MemoizedConfig(
    new CompoundConfig(
        new EnvConfig(),                    // Highest precedence
        new TomlConfig(Paths.get("grid.toml")), 
        new MapConfig(defaultValues)        // Lowest precedence
    )
);

/**
 * Exception thrown for configuration-related problems
 */
class ConfigException extends RuntimeException {
    ConfigException(String message);
    ConfigException(String message, Throwable cause);
}

/**
 * Command-line flags for configuration options
 */
class ConfigFlags {
    @Parameter(names = {"--config"}, description = "Path to configuration file")
    List<String> configPaths = new ArrayList<>();
    
    Config getConfig();
}

[server]
host = "0.0.0.0"
port = 4444
max-threads = 24

[distributor]
implementation = "org.openqa.selenium.grid.distributor.local.LocalDistributor"
healthcheck-interval = "120s"

[sessionmap]
implementation = "org.openqa.selenium.grid.sessionmap.redis.RedisSessionMap"

[sessionmap.redis]
host = "redis.example.com"
port = 6379

{
  "server": {
    "host": "0.0.0.0",
    "port": 4444,
    "max-threads": 24
  },
  "distributor": {
    "implementation": "org.openqa.selenium.grid.distributor.local.LocalDistributor",
    "healthcheck-interval": "120s"
  }
}

SE_SERVER_HOST=0.0.0.0
SE_SERVER_PORT=4444
SE_DISTRIBUTOR_IMPLEMENTATION=org.openqa.selenium.grid.distributor.local.LocalDistributor