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package io.mstream.trader.commons.config.supplier;


import io.mstream.trader.commons.config.Config;
import io.mstream.trader.commons.config.ConfigClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import ratpack.service.Service;
import ratpack.service.StartEvent;

import javax.inject.Inject;
import java.util.Optional;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import java.util.function.Supplier;


public class ConfigSupplier
        implements Supplier, Service {
    
    private static final Logger LOGGER = LoggerFactory.getLogger
            (ConfigSupplier.class);
    
    private final Class configType;
    
    private final ConfigClient configClient;
    
    private final ScheduledExecutorService executor;
    
    private volatile T config;
    
    @Inject
    public ConfigSupplier(
            @Config
                    Class configType,
            ConfigClient configClient,
            ScheduledExecutorService executor
    ) {
        
        this.configType = configType;
        this.configClient = configClient;
        this.executor = executor;
    }
    
    
    @Override
    public void onStart(StartEvent event)
            throws Exception {
    
        executor.scheduleAtFixedRate(this::loadConfig, 0, 1, TimeUnit.SECONDS);
    }
    
    public  R get(Function subConfigExtractor) {
        
        T config = get();
        return subConfigExtractor.apply(config);
    }
    
    @Override
    public T get() {
        
        loadConfig();
        if (config == null) {
            throw new IllegalStateException("config is not loaded");
        }
        return config;
    }
    
    private void loadConfig() {
    
        if (config != null) {
            return;
        }
        Optional configOpt = configClient.read(configType);
        if (!configOpt.isPresent()) {
            LOGGER.error("config can't be loaded");
        } else {
            config = configOpt.get();
        }
    }
}