package it.tdlight.reactiveapi;

import static java.util.Collections.unmodifiableSet;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
import it.tdlight.reactiveapi.AtomixReactiveApi.AtomixReactiveApiMode;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.HashSet;
import java.util.Set;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.jetbrains.annotations.Nullable;

public class Entrypoint {

	private static final Logger LOG = LogManager.getLogger(Entrypoint.class);

	public record ValidEntrypointArgs(String clusterPath, String instancePath, String diskSessionsPath) {}

	public static ValidEntrypointArgs parseArguments(String[] args) {
		// Check arguments validity
		if (args.length != 3
				|| args[0].isBlank()
				|| args[1].isBlank()
				|| args[2].isBlank()
				|| !Files.isRegularFile(Paths.get(args[0]))
				|| !Files.isRegularFile(Paths.get(args[1]))
				|| !Files.isRegularFile(Paths.get(args[2]))) {
			System.err.println("Syntax: executable <path/to/cluster.yaml> <path/to/instance.yaml> <path/to/disk-sessions.yaml>");
			System.exit(1);
		}
		return new ValidEntrypointArgs(args[0], args[1], args[2]);
	}

	public static ReactiveApi start(ValidEntrypointArgs args) throws IOException {
		// Read settings
		ClusterSettings clusterSettings;
		InstanceSettings instanceSettings;
		DiskSessionsManager diskSessions;
		{
			var mapper = new ObjectMapper(new YAMLFactory());
			mapper.findAndRegisterModules();
			String clusterConfigPath = args.clusterPath;
			String instanceConfigPath = args.instancePath;
			String diskSessionsConfigPath = args.diskSessionsPath;
			clusterSettings = mapper.readValue(Paths.get(clusterConfigPath).toFile(), ClusterSettings.class);
			instanceSettings = mapper.readValue(Paths.get(instanceConfigPath).toFile(), InstanceSettings.class);
			diskSessions = switch (instanceSettings.instanceType) {
				case TDLIB -> new DiskSessionsManager(mapper, diskSessionsConfigPath);
				case UPDATES_CONSUMER -> null;
			};
		}

		return start(clusterSettings, instanceSettings, diskSessions);
	}

	public static ReactiveApi start(ClusterSettings clusterSettings,
			InstanceSettings instanceSettings,
			@Nullable DiskSessionsManager diskSessions) {

		Set<ResultingEventTransformer> resultingEventTransformerSet;
		AtomixReactiveApiMode mode = AtomixReactiveApiMode.SERVER;
		switch (instanceSettings.instanceType) {
			case UPDATES_CONSUMER -> {
				if (diskSessions != null) {
					throw new IllegalArgumentException("An updates-consumer instance can't have a session manager!");
				}
				if (instanceSettings.listenAddress == null) {
					throw new IllegalArgumentException("An updates-consumer instance must have an address (host:port)");
				}
				mode = AtomixReactiveApiMode.CLIENT;
				resultingEventTransformerSet = Set.of();
			}
			case TDLIB -> {
				if (diskSessions == null) {
					throw new IllegalArgumentException("A tdlib instance must have a session manager!");
				}

				resultingEventTransformerSet = new HashSet<>();
				if (instanceSettings.resultingEventTransformers != null) {
					for (var resultingEventTransformer: instanceSettings.resultingEventTransformers) {
						try {
							var instance = resultingEventTransformer.getConstructor().newInstance();
							resultingEventTransformerSet.add(instance);
							LOG.info("Loaded and applied resulting event transformer: " + resultingEventTransformer.getName());
						} catch (InstantiationException | IllegalAccessException | InvocationTargetException e) {
							throw new IllegalArgumentException("Failed to load resulting event transformer: "
									+ resultingEventTransformer.getName());
						} catch (NoSuchMethodException e) {
							throw new IllegalArgumentException("The client transformer must declare an empty constructor: "
									+ resultingEventTransformer.getName());
						}
					}
				}

				resultingEventTransformerSet = unmodifiableSet(resultingEventTransformerSet);
			}
			default -> throw new UnsupportedOperationException("Unsupported instance type: " + instanceSettings.instanceType);
		}

		ChannelsParameters channelsParameters = clusterSettings.toParameters(instanceSettings.id, instanceSettings.instanceType);

		var api = new AtomixReactiveApi(mode, channelsParameters, diskSessions, resultingEventTransformerSet);

		LOG.info("Starting ReactiveApi...");

		api.start().block();

		LOG.info("Started ReactiveApi");

		return api;
	}

	public static void main(String[] args) throws IOException {
		var validArgs = parseArguments(args);
		var api = start(validArgs);
		api.waitForExit();
	}
}