/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.common.xcontent;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.exc.StreamConstraintsException;
import com.fasterxml.jackson.dataformat.yaml.JacksonYAMLParseException;

import org.opensearch.common.CheckedSupplier;
import org.opensearch.common.Strings;
import org.opensearch.core.common.bytes.BytesReference;
import org.opensearch.common.xcontent.cbor.CborXContent;
import org.opensearch.common.xcontent.json.JsonXContent;
import org.opensearch.common.xcontent.smile.SmileXContent;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.core.xcontent.XContentParseException;
import org.opensearch.core.xcontent.XContentParser;
import org.opensearch.core.xcontent.XContentSubParser;
import org.opensearch.test.OpenSearchTestCase;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;

import static java.util.Collections.emptyMap;
import static java.util.Collections.singletonMap;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.hasLength;
import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.in;
import static org.hamcrest.Matchers.instanceOf;
import static org.hamcrest.Matchers.nullValue;
import static org.junit.internal.matchers.ThrowableMessageMatcher.hasMessage;

public class XContentParserTests extends OpenSearchTestCase {
    private static final Map<XContentType, Supplier<String>> GENERATORS = Map.of(
        XContentType.JSON,
        () -> randomAlphaOfLengthBetween(1, JsonXContent.DEFAULT_MAX_STRING_LEN),
        XContentType.CBOR,
        () -> randomAlphaOfLengthBetween(1, CborXContent.DEFAULT_MAX_STRING_LEN),
        XContentType.SMILE,
        () -> randomAlphaOfLengthBetween(1, SmileXContent.DEFAULT_MAX_STRING_LEN),
        /* YAML parser limitation */
        XContentType.YAML,
        () -> randomAlphaOfLengthBetween(1, 3140000)
    );

    private static final Map<XContentType, Supplier<String>> OFF_LIMIT_GENERATORS = Map.of(
        XContentType.JSON,
        () -> randomAlphaOfLength(JsonXContent.DEFAULT_MAX_STRING_LEN + 1),
        XContentType.CBOR,
        () -> randomAlphaOfLength(CborXContent.DEFAULT_MAX_STRING_LEN + 1),
        XContentType.SMILE,
        () -> randomAlphaOfLength(SmileXContent.DEFAULT_MAX_STRING_LEN + 1),
        /* YAML parser limitation */
        XContentType.YAML,
        () -> randomRealisticUnicodeOfCodepointLength(3145730)
    );

    public void testStringOffLimit() throws IOException {
        final XContentType xContentType = randomFrom(XContentType.values());

        final String field = randomAlphaOfLengthBetween(1, 5);
        final String value = OFF_LIMIT_GENERATORS.get(xContentType).get();

        try (XContentBuilder builder = XContentBuilder.builder(xContentType.xContent())) {
            builder.startObject();
            if (randomBoolean()) {
                builder.field(field, value);
            } else {
                builder.field(field).value(value);
            }
            builder.endObject();

            try (XContentParser parser = createParser(xContentType.xContent(), BytesReference.bytes(builder))) {
                assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
                assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
                assertEquals(field, parser.currentName());
                assertEquals(XContentParser.Token.VALUE_STRING, parser.nextToken());
                if (xContentType != XContentType.YAML) {
                    assertThrows(StreamConstraintsException.class, () -> parser.text());
                } else {
                    assertThrows(JacksonYAMLParseException.class, () -> parser.nextToken());
                }
            }
        }
    }

    public void testString() throws IOException {
        final XContentType xContentType = randomFrom(XContentType.values());

        final String field = randomAlphaOfLengthBetween(1, 5);
        final String value = GENERATORS.get(xContentType).get();

        try (XContentBuilder builder = XContentBuilder.builder(xContentType.xContent())) {
            builder.startObject();
            if (randomBoolean()) {
                builder.field(field, value);
            } else {
                builder.field(field).value(value);
            }
            builder.endObject();

            final String text;
            try (XContentParser parser = createParser(xContentType.xContent(), BytesReference.bytes(builder))) {
                assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
                assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
                assertEquals(field, parser.currentName());
                assertEquals(XContentParser.Token.VALUE_STRING, parser.nextToken());

                text = parser.text();

                assertEquals(XContentParser.Token.END_OBJECT, parser.nextToken());
                assertNull(parser.nextToken());
            }

            assertThat(text, hasLength(value.length()));
        }
    }

    public void testFloat() throws IOException {
        final XContentType xContentType = randomFrom(XContentType.values());

        final String field = randomAlphaOfLengthBetween(1, 5);
        final Float value = randomFloat();

        try (XContentBuilder builder = XContentBuilder.builder(xContentType.xContent())) {
            builder.startObject();
            if (randomBoolean()) {
                builder.field(field, value);
            } else {
                builder.field(field).value(value);
            }
            builder.endObject();

            final Number number;
            try (XContentParser parser = createParser(xContentType.xContent(), BytesReference.bytes(builder))) {
                assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
                assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
                assertEquals(field, parser.currentName());
                assertEquals(XContentParser.Token.VALUE_NUMBER, parser.nextToken());

                number = parser.numberValue();

                assertEquals(XContentParser.Token.END_OBJECT, parser.nextToken());
                assertNull(parser.nextToken());
            }

            assertEquals(value, number.floatValue(), 0.0f);

            switch (xContentType) {
                case CBOR:
                case SMILE:
                    assertThat(number, instanceOf(Float.class));
                    break;
                case JSON:
                case YAML:
                    assertThat(number, instanceOf(Double.class));
                    break;
                default:
                    throw new AssertionError("unexpected x-content type [" + xContentType + "]");
            }
        }
    }

    public void testReadList() throws IOException {
        assertThat(readList("{\"foo\": [\"bar\"]}"), contains("bar"));
        assertThat(readList("{\"foo\": [\"bar\",\"baz\"]}"), contains("bar", "baz"));
        assertThat(readList("{\"foo\": [1, 2, 3], \"bar\": 4}"), contains(1, 2, 3));
        assertThat(readList("{\"foo\": [{\"bar\":1},{\"baz\":2},{\"qux\":3}]}"), hasSize(3));
        assertThat(readList("{\"foo\": [null]}"), contains(nullValue()));
        assertThat(readList("{\"foo\": []}"), hasSize(0));
        assertThat(readList("{\"foo\": [1]}"), contains(1));
        assertThat(readList("{\"foo\": [1,2]}"), contains(1, 2));
        assertThat(readList("{\"foo\": [{},{},{},{}]}"), hasSize(4));
    }

    public void testReadListThrowsException() throws IOException {
        // Calling XContentParser.list() or listOrderedMap() to read a simple
        // value or object should throw an exception
        assertReadListThrowsException("{\"foo\": \"bar\"}");
        assertReadListThrowsException("{\"foo\": 1, \"bar\": 2}");
        assertReadListThrowsException("{\"foo\": {\"bar\":\"baz\"}}");
    }

    @SuppressWarnings("unchecked")
    private <T> List<T> readList(String source) throws IOException {
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, source)) {
            XContentParser.Token token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));
            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("foo"));
            return (List<T>) (randomBoolean() ? parser.listOrderedMap() : parser.list());
        }
    }

    private void assertReadListThrowsException(String source) {
        try {
            readList(source);
            fail("should have thrown a parse exception");
        } catch (Exception e) {
            assertThat(e, instanceOf(XContentParseException.class));
            assertThat(e.getMessage(), containsString("Failed to parse list"));
        }
    }

    public void testReadMapStrings() throws IOException {
        Map<String, String> map = readMapStrings("{\"foo\": {\"kbar\":\"vbar\"}}");
        assertThat(map.get("kbar"), equalTo("vbar"));
        assertThat(map.size(), equalTo(1));
        map = readMapStrings("{\"foo\": {\"kbar\":\"vbar\", \"kbaz\":\"vbaz\"}}");
        assertThat(map.get("kbar"), equalTo("vbar"));
        assertThat(map.get("kbaz"), equalTo("vbaz"));
        assertThat(map.size(), equalTo(2));
        map = readMapStrings("{\"foo\": {}}");
        assertThat(map.size(), equalTo(0));
    }

    public void testMap() throws IOException {
        String source = "{\"i\": {\"_doc\": {\"f1\": {\"type\": \"text\", \"analyzer\": \"english\"}, "
            + "\"f2\": {\"type\": \"object\", \"properties\": {\"sub1\": {\"type\": \"keyword\", \"foo\": 17}}}}}}";
        Map<String, Object> f1 = new HashMap<>();
        f1.put("type", "text");
        f1.put("analyzer", "english");

        Map<String, Object> sub1 = new HashMap<>();
        sub1.put("type", "keyword");
        sub1.put("foo", 17);

        Map<String, Object> properties = new HashMap<>();
        properties.put("sub1", sub1);

        Map<String, Object> f2 = new HashMap<>();
        f2.put("type", "object");
        f2.put("properties", properties);

        Map<String, Object> doc = new HashMap<>();
        doc.put("f1", f1);
        doc.put("f2", f2);

        Map<String, Object> expected = new HashMap<>();
        expected.put("_doc", doc);

        Map<String, Object> i = new HashMap<>();
        i.put("i", expected);

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, source)) {
            XContentParser.Token token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));
            Map<String, Object> map = parser.map();
            assertThat(map, equalTo(i));
        }
    }

    private Map<String, String> readMapStrings(String source) throws IOException {
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, source)) {
            XContentParser.Token token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));
            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("foo"));
            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));
            return parser.mapStrings();
        }
    }

    public void testReadBooleansFailsForLenientBooleans() throws IOException {
        String falsy = randomFrom("\"off\"", "\"no\"", "\"0\"", "0");
        String truthy = randomFrom("\"on\"", "\"yes\"", "\"1\"", "1");

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, "{\"foo\": " + falsy + ", \"bar\": " + truthy + "}")) {
            XContentParser.Token token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));

            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("foo"));
            token = parser.nextToken();
            assertThat(token, in(Arrays.asList(XContentParser.Token.VALUE_STRING, XContentParser.Token.VALUE_NUMBER)));
            assertFalse(parser.isBooleanValue());
            if (token.equals(XContentParser.Token.VALUE_STRING)) {
                expectThrows(IllegalArgumentException.class, parser::booleanValue);
            } else {
                expectThrows(JsonParseException.class, parser::booleanValue);
            }

            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("bar"));
            token = parser.nextToken();
            assertThat(token, in(Arrays.asList(XContentParser.Token.VALUE_STRING, XContentParser.Token.VALUE_NUMBER)));
            assertFalse(parser.isBooleanValue());
            if (token.equals(XContentParser.Token.VALUE_STRING)) {
                expectThrows(IllegalArgumentException.class, parser::booleanValue);
            } else {
                expectThrows(JsonParseException.class, parser::booleanValue);
            }
        }
    }

    public void testReadBooleans() throws IOException {
        String falsy = randomFrom("\"false\"", "false");
        String truthy = randomFrom("\"true\"", "true");

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, "{\"foo\": " + falsy + ", \"bar\": " + truthy + "}")) {
            XContentParser.Token token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.START_OBJECT));
            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("foo"));
            token = parser.nextToken();
            assertThat(token, in(Arrays.asList(XContentParser.Token.VALUE_STRING, XContentParser.Token.VALUE_BOOLEAN)));
            assertTrue(parser.isBooleanValue());
            assertFalse(parser.booleanValue());

            token = parser.nextToken();
            assertThat(token, equalTo(XContentParser.Token.FIELD_NAME));
            assertThat(parser.currentName(), equalTo("bar"));
            token = parser.nextToken();
            assertThat(token, in(Arrays.asList(XContentParser.Token.VALUE_STRING, XContentParser.Token.VALUE_BOOLEAN)));
            assertTrue(parser.isBooleanValue());
            assertTrue(parser.booleanValue());
        }
    }

    public void testEmptyList() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder().startObject().startArray("some_array").endArray().endObject();

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, Strings.toString(builder))) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
            assertEquals("some_array", parser.currentName());
            if (random().nextBoolean()) {
                // sometimes read the start array token, sometimes not
                assertEquals(XContentParser.Token.START_ARRAY, parser.nextToken());
            }
            assertEquals(Collections.emptyList(), parser.list());
        }
    }

    public void testSimpleList() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder()
            .startObject()
            .startArray("some_array")
            .value(1)
            .value(3)
            .value(0)
            .endArray()
            .endObject();

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, Strings.toString(builder))) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
            assertEquals("some_array", parser.currentName());
            if (random().nextBoolean()) {
                // sometimes read the start array token, sometimes not
                assertEquals(XContentParser.Token.START_ARRAY, parser.nextToken());
            }
            assertEquals(Arrays.asList(1, 3, 0), parser.list());
        }
    }

    public void testNestedList() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder()
            .startObject()
            .startArray("some_array")
            .startArray()
            .endArray()
            .startArray()
            .value(1)
            .value(3)
            .endArray()
            .startArray()
            .value(2)
            .endArray()
            .endArray()
            .endObject();

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, Strings.toString(builder))) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
            assertEquals("some_array", parser.currentName());
            if (random().nextBoolean()) {
                // sometimes read the start array token, sometimes not
                assertEquals(XContentParser.Token.START_ARRAY, parser.nextToken());
            }
            assertEquals(Arrays.asList(Collections.<Integer>emptyList(), Arrays.asList(1, 3), Arrays.asList(2)), parser.list());
        }
    }

    public void testNestedMapInList() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder()
            .startObject()
            .startArray("some_array")
            .startObject()
            .field("foo", "bar")
            .endObject()
            .startObject()
            .endObject()
            .endArray()
            .endObject();

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, Strings.toString(builder))) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken());
            assertEquals("some_array", parser.currentName());
            if (random().nextBoolean()) {
                // sometimes read the start array token, sometimes not
                assertEquals(XContentParser.Token.START_ARRAY, parser.nextToken());
            }
            assertEquals(Arrays.asList(singletonMap("foo", "bar"), emptyMap()), parser.list());
        }
    }

    public void testGenericMap() throws IOException {
        String content = "{"
            + "\"c\": { \"i\": 3, \"d\": 0.3, \"s\": \"ccc\" }, "
            + "\"a\": { \"i\": 1, \"d\": 0.1, \"s\": \"aaa\" }, "
            + "\"b\": { \"i\": 2, \"d\": 0.2, \"s\": \"bbb\" }"
            + "}";
        SimpleStruct structA = new SimpleStruct(1, 0.1, "aaa");
        SimpleStruct structB = new SimpleStruct(2, 0.2, "bbb");
        SimpleStruct structC = new SimpleStruct(3, 0.3, "ccc");
        Map<String, SimpleStruct> expectedMap = new HashMap<>();
        expectedMap.put("a", structA);
        expectedMap.put("b", structB);
        expectedMap.put("c", structC);
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            Map<String, SimpleStruct> actualMap = parser.map(HashMap::new, SimpleStruct::fromXContent);
            // Verify map contents, ignore the iteration order.
            assertThat(actualMap, equalTo(expectedMap));
            assertThat(actualMap.values(), containsInAnyOrder(structA, structB, structC));
            assertNull(parser.nextToken());
        }
    }

    public void testGenericMapOrdered() throws IOException {
        String content = "{"
            + "\"c\": { \"i\": 3, \"d\": 0.3, \"s\": \"ccc\" }, "
            + "\"a\": { \"i\": 1, \"d\": 0.1, \"s\": \"aaa\" }, "
            + "\"b\": { \"i\": 2, \"d\": 0.2, \"s\": \"bbb\" }"
            + "}";
        SimpleStruct structA = new SimpleStruct(1, 0.1, "aaa");
        SimpleStruct structB = new SimpleStruct(2, 0.2, "bbb");
        SimpleStruct structC = new SimpleStruct(3, 0.3, "ccc");
        Map<String, SimpleStruct> expectedMap = new HashMap<>();
        expectedMap.put("a", structA);
        expectedMap.put("b", structB);
        expectedMap.put("c", structC);
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            Map<String, SimpleStruct> actualMap = parser.map(LinkedHashMap::new, SimpleStruct::fromXContent);
            // Verify map contents, ignore the iteration order.
            assertThat(actualMap, equalTo(expectedMap));
            // Verify that map's iteration order is the same as the order in which fields appear in JSON.
            assertThat(actualMap.values(), contains(structC, structA, structB));
            assertNull(parser.nextToken());
        }
    }

    public void testGenericMap_Failure_MapContainingUnparsableValue() throws IOException {
        String content = "{"
            + "\"a\": { \"i\": 1, \"d\": 0.1, \"s\": \"aaa\" }, "
            + "\"b\": { \"i\": 2, \"d\": 0.2, \"s\": 666 }, "
            + "\"c\": { \"i\": 3, \"d\": 0.3, \"s\": \"ccc\" }"
            + "}";
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            XContentParseException exception = expectThrows(
                XContentParseException.class,
                () -> parser.map(HashMap::new, SimpleStruct::fromXContent)
            );
            assertThat(exception, hasMessage(containsString("s doesn't support values of type: VALUE_NUMBER")));
        }
    }

    public void testSubParserObject() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder();
        int numberOfTokens;
        numberOfTokens = generateRandomObjectForMarking(builder);
        String content = Strings.toString(builder);

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken()); // first field
            assertEquals("first_field", parser.currentName());
            assertEquals(XContentParser.Token.VALUE_STRING, parser.nextToken()); // foo
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken()); // marked field
            assertEquals("marked_field", parser.currentName());
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken()); // {
            XContentParser subParser = new XContentSubParser(parser);
            try {
                int tokensToSkip = randomInt(numberOfTokens - 1);
                for (int i = 0; i < tokensToSkip; i++) {
                    // Simulate incomplete parsing
                    assertNotNull(subParser.nextToken());
                }
                if (randomBoolean()) {
                    // And sometimes skipping children
                    subParser.skipChildren();
                }

            } finally {
                assertFalse(subParser.isClosed());
                subParser.close();
                assertTrue(subParser.isClosed());
            }
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken()); // last field
            assertEquals("last_field", parser.currentName());
            assertEquals(XContentParser.Token.VALUE_STRING, parser.nextToken());
            assertEquals(XContentParser.Token.END_OBJECT, parser.nextToken());
            assertNull(parser.nextToken());
        }
    }

    public void testSubParserArray() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder();
        int numberOfArrayElements = randomInt(10);
        builder.startObject();
        builder.field("array");
        builder.startArray();
        int numberOfTokens = 0;
        for (int i = 0; i < numberOfArrayElements; ++i) {
            numberOfTokens += generateRandomObject(builder, 0);
        }
        builder.endArray();
        builder.endObject();

        String content = Strings.toString(builder);

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken()); // array field
            assertEquals("array", parser.currentName());
            assertEquals(XContentParser.Token.START_ARRAY, parser.nextToken()); // [
            XContentParser subParser = new XContentSubParser(parser);
            try {
                int tokensToSkip = randomInt(numberOfTokens);
                for (int i = 0; i < tokensToSkip; i++) {
                    // Simulate incomplete parsing
                    assertNotNull(subParser.nextToken());
                }
                if (randomBoolean()) {
                    // And sometimes skipping children
                    subParser.skipChildren();
                }

            } finally {
                assertFalse(subParser.isClosed());
                subParser.close();
                assertTrue(subParser.isClosed());
            }
            assertEquals(XContentParser.Token.END_ARRAY, parser.currentToken());
            assertEquals(XContentParser.Token.END_OBJECT, parser.nextToken());
            assertNull(parser.nextToken());
        }
    }

    public void testCreateSubParserAtAWrongPlace() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder();
        generateRandomObjectForMarking(builder);
        String content = Strings.toString(builder);

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            assertEquals(XContentParser.Token.FIELD_NAME, parser.nextToken()); // first field
            assertEquals("first_field", parser.currentName());
            IllegalStateException exception = expectThrows(IllegalStateException.class, () -> new XContentSubParser(parser));
            assertEquals("The sub parser has to be created on the start of an object or array", exception.getMessage());
        }
    }

    public void testCreateRootSubParser() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder();
        int numberOfTokens = generateRandomObjectForMarking(builder);
        String content = Strings.toString(builder);

        try (XContentParser parser = createParser(JsonXContent.jsonXContent, content)) {
            assertEquals(XContentParser.Token.START_OBJECT, parser.nextToken());
            try (XContentParser subParser = new XContentSubParser(parser)) {
                int tokensToSkip = randomInt(numberOfTokens + 3);
                for (int i = 0; i < tokensToSkip; i++) {
                    // Simulate incomplete parsing
                    assertNotNull(subParser.nextToken());
                }
            }
            assertNull(parser.nextToken());
        }

    }

    /**
     * Generates a random object {"first_field": "foo", "marked_field": {...random...}, "last_field": "bar}
     *
     * Returns the number of tokens in the marked field
     */
    private static int generateRandomObjectForMarking(XContentBuilder builder) throws IOException {
        builder.startObject().field("first_field", "foo").field("marked_field");
        int numberOfTokens = generateRandomObject(builder, 0);
        builder.field("last_field", "bar").endObject();
        return numberOfTokens;
    }

    public static int generateRandomObject(XContentBuilder builder, int level) throws IOException {
        int tokens = 2;
        builder.startObject();
        int numberOfElements = randomInt(5);
        for (int i = 0; i < numberOfElements; i++) {
            builder.field(randomAlphaOfLength(10) + "_" + i);
            tokens += generateRandomValue(builder, level + 1);
        }
        builder.endObject();
        return tokens;
    }

    private static int generateRandomValue(XContentBuilder builder, int level) throws IOException {
        @SuppressWarnings("unchecked")
        CheckedSupplier<Integer, IOException> fieldGenerator = randomFrom(() -> {
            builder.value(randomInt());
            return 1;
        }, () -> {
            builder.value(randomAlphaOfLength(10));
            return 1;
        }, () -> {
            builder.value(randomDouble());
            return 1;
        }, () -> {
            if (level < 3) {
                // don't need to go too deep
                return generateRandomObject(builder, level + 1);
            } else {
                builder.value(0);
                return 1;
            }
        }, () -> {
            if (level < 5) { // don't need to go too deep
                return generateRandomArray(builder, level);
            } else {
                builder.value(0);
                return 1;
            }
        });
        return fieldGenerator.get();
    }

    private static int generateRandomArray(XContentBuilder builder, int level) throws IOException {
        int tokens = 2;
        int arraySize = randomInt(3);
        builder.startArray();
        for (int i = 0; i < arraySize; i++) {
            tokens += generateRandomValue(builder, level + 1);
        }
        builder.endArray();
        return tokens;
    }

}