package net.minecraft.util.eventlog;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.mojang.serialization.Codec;
import com.mojang.serialization.JsonOps;
import java.io.Closeable;
import java.io.IOException;
import java.io.Writer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.atomic.AtomicInteger;
import org.jetbrains.annotations.Nullable;

public class JsonEventLog<T> implements Closeable {
	private static final Gson GSON = new Gson();
	private final Codec<T> codec;
	final FileChannel channel;
	private final AtomicInteger referenceCount = new AtomicInteger(1);

	public JsonEventLog(Codec<T> codec, FileChannel channel) {
		this.codec = codec;
		this.channel = channel;
	}

	public static <T> JsonEventLog<T> open(Codec<T> codec, Path path) throws IOException {
		FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);
		return new JsonEventLog<>(codec, fileChannel);
	}

	public void write(T data) throws IOException {
		JsonElement jsonElement = this.codec.encodeStart(JsonOps.INSTANCE, data).getOrThrow(IOException::new);
		this.channel.position(this.channel.size());
		Writer writer = Channels.newWriter(this.channel, StandardCharsets.UTF_8);
		GSON.toJson(jsonElement, GSON.newJsonWriter(writer));
		writer.write(10);
		writer.flush();
	}

	public JsonEventLogReader<T> openReader() throws IOException {
		if (this.referenceCount.get() <= 0) {
			throw new IOException("Event log has already been closed");
		} else {
			this.referenceCount.incrementAndGet();
			final JsonEventLogReader<T> jsonEventLogReader = JsonEventLogReader.create(this.codec, Channels.newReader(this.channel, StandardCharsets.UTF_8));
			return new JsonEventLogReader<T>() {
				private volatile long position;

				@Nullable
				@Override
				public T next() throws IOException {
					Object var1;
					try {
						JsonEventLog.this.channel.position(this.position);
						var1 = jsonEventLogReader.next();
					} finally {
						this.position = JsonEventLog.this.channel.position();
					}

					return (T)var1;
				}

				public void close() throws IOException {
					JsonEventLog.this.releaseReference();
				}
			};
		}
	}

	public void close() throws IOException {
		this.releaseReference();
	}

	void releaseReference() throws IOException {
		if (this.referenceCount.decrementAndGet() <= 0) {
			this.channel.close();
		}
	}
}