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/*
 * Copyright (c) 2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.cometd.common;

import java.io.IOException;
import java.io.Reader;
import java.nio.ByteBuffer;
import java.text.ParseException;
import java.util.List;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.core.async.ByteArrayFeeder;
import com.fasterxml.jackson.core.async.ByteBufferFeeder;
import com.fasterxml.jackson.core.async.NonBlockingInputFeeder;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.CollectionType;
import com.fasterxml.jackson.databind.util.TokenBuffer;
import org.cometd.bayeux.Message;

public abstract class JacksonJSONContext {
    private final ObjectMapper objectMapper = new ObjectMapper();
    private final CollectionType collectionType;

    protected JacksonJSONContext() {
        collectionType = objectMapper.getTypeFactory().constructCollectionType(List.class, messageClass());
    }

    public ObjectMapper getObjectMapper() {
        return objectMapper;
    }

    protected abstract Class messageClass();

    public List parse(String json) throws ParseException {
        try {
            return getObjectMapper().readValue(json, collectionType);
        } catch (IOException x) {
            throw (ParseException)new ParseException(json, -1).initCause(x);
        }
    }

    public JSONContext.AsyncParser newAsyncParser() {
        try {
            JsonParser jsonParser = objectMapper.getFactory().createNonBlockingByteArrayParser();
            return new AsyncJsonParser(jsonParser);
        } catch (Throwable x) {
            return null;
        }
    }

    public String generate(M message) {
        try {
            return getObjectMapper().writeValueAsString(message);
        } catch (IOException x) {
            throw new RuntimeException(x);
        }
    }

    public JSONContext.Parser getParser() {
        return new ObjectMapperParser();
    }

    public JSONContext.Generator getGenerator() {
        return new ObjectMapperGenerator();
    }

    private class ObjectMapperParser implements JSONContext.Parser {
        @Override
        public  R parse(Reader reader, Class type) throws ParseException {
            try {
                return getObjectMapper().readValue(reader, type);
            } catch (IOException x) {
                throw (ParseException)new ParseException("", -1).initCause(x);
            }
        }
    }

    protected class ObjectMapperGenerator implements JSONContext.Generator {
        @Override
        public String generate(Object object) {
            try {
                return getObjectMapper().writeValueAsString(object);
            } catch (IOException x) {
                throw new RuntimeException(x);
            }
        }
    }

    private class AsyncJsonParser implements JSONContext.AsyncParser {
        private final JsonParser jsonParser;
        private final TokenBuffer tokenBuffer;

        public AsyncJsonParser(JsonParser jsonParser) {
            this.jsonParser = jsonParser;
            this.tokenBuffer = new TokenBuffer(jsonParser);
        }

        @Override
        public void parse(ByteBuffer buffer) {
            try {
                NonBlockingInputFeeder input = jsonParser.getNonBlockingInputFeeder();
                if (input instanceof ByteBufferFeeder feeder) {
                    feeder.feedInput(buffer);
                    parseInput();
                } else if (input instanceof ByteArrayFeeder feeder) {
                    if (buffer.hasArray()) {
                        int startIndex = buffer.arrayOffset() + buffer.position();
                        int endIndex = startIndex + buffer.remaining();
                        feeder.feedInput(buffer.array(), startIndex, endIndex);
                    } else {
                        byte[] bytes = new byte[buffer.remaining()];
                        buffer.get(bytes);
                        feeder.feedInput(bytes, 0, bytes.length);
                    }
                    parseInput();
                } else {
                    throw new UnsupportedOperationException();
                }
            } catch (IOException x) {
                throw new IllegalStateException(x);
            }
        }

        private void parseInput() throws IOException {
            while (true) {
                JsonToken jsonToken = jsonParser.nextToken();
                if (jsonToken == JsonToken.NOT_AVAILABLE) {
                    break;
                }
                tokenBuffer.copyCurrentEvent(jsonParser);
            }
        }

        @Override
        public  R complete() {
            try {
                NonBlockingInputFeeder feeder = jsonParser.getNonBlockingInputFeeder();
                feeder.endOfInput();
                jsonParser.nextToken();
                return objectMapper.readValue(tokenBuffer.asParser(), collectionType);
            } catch (IOException x) {
                throw new IllegalArgumentException(x);
            }
        }
    }
}