package com.fasterxml.jackson.dataformat.csv;

import java.io.*;
import java.math.BigDecimal;
import java.math.BigInteger;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.base.ParserMinimalBase;
import com.fasterxml.jackson.core.json.DupDetector;
import com.fasterxml.jackson.core.json.JsonReadContext;
import com.fasterxml.jackson.core.util.ByteArrayBuilder;
import com.fasterxml.jackson.core.util.JacksonFeatureSet;
import com.fasterxml.jackson.dataformat.csv.impl.CsvDecoder;
import com.fasterxml.jackson.dataformat.csv.impl.CsvIOContext;
import com.fasterxml.jackson.dataformat.csv.impl.TextBuffer;

JsonParser implementation used to expose CSV documents in form that allows other Jackson functionality to deal with it. 
 Implementation is based on a state-machine that pulls information using CsvDecoder. /**
 * {@link JsonParser} implementation used to expose CSV documents
 * in form that allows other Jackson functionality to deal
 * with it.
 *<p>
 * Implementation is based on a state-machine that pulls information
 * using {@link CsvDecoder}.
 */
public class CsvParser
    extends ParserMinimalBase
{
    // @since 2.9.9: just to protect against bugs, DoS, limit number of column defs we may read
    private final static int MAX_COLUMNS = 99999;

    
Enumeration that defines all togglable features for CSV parsers
/**
     * Enumeration that defines all togglable features for CSV parsers
     */
    public enum Feature
        implements FormatFeature // since 2.7
    {
        
Feature determines whether spaces around separator characters
(commas) are to be automatically trimmed before being reported
or not.
Note that this does NOT force trimming of possible white space from
within double-quoted values, but only those surrounding unquoted
values (white space outside of double-quotes is never included regardless
of trimming).

Default value is false, as per RFC-4180.
/**
         * Feature determines whether spaces around separator characters
         * (commas) are to be automatically trimmed before being reported
         * or not.
         * Note that this does NOT force trimming of possible white space from
         * within double-quoted values, but only those surrounding unquoted
         * values (white space outside of double-quotes is never included regardless
         * of trimming).
         *<p>
         * Default value is false, as per <a href="http://tools.ietf.org/html/rfc4180">RFC-4180</a>.
         */
        TRIM_SPACES(false),

        
Feature that determines how stream of records (usually CSV lines, but sometimes
multiple lines when linefeeds are included in quoted values) is exposed:
either as a sequence of Objects (false), or as an Array of Objects (true).
Using stream of Objects is convenient when using
ObjectMapper.readValues(...)
and array of Objects convenient when binding to Lists or
arrays of values.

Default value is false, meaning that by default a CSV document is exposed as
a sequence of root-level Object entries.
/**
         * Feature that determines how stream of records (usually CSV lines, but sometimes
         * multiple lines when linefeeds are included in quoted values) is exposed:
         * either as a sequence of Objects (false), or as an Array of Objects (true).
         * Using stream of Objects is convenient when using
         * <code>ObjectMapper.readValues(...)</code>
         * and array of Objects convenient when binding to <code>List</code>s or
         * arrays of values.
         *<p>
         * Default value is false, meaning that by default a CSV document is exposed as
         * a sequence of root-level Object entries.
         */
        WRAP_AS_ARRAY(false),

        
Feature that allows ignoring of unmappable "extra" columns; that is, values for
columns that appear after columns for which types are defined. When disabled,
an exception is thrown for such column values, but if enabled, they are
silently ignored.

Feature is disabled by default.
Since:
2.7/**
         * Feature that allows ignoring of unmappable "extra" columns; that is, values for
         * columns that appear after columns for which types are defined. When disabled,
         * an exception is thrown for such column values, but if enabled, they are
         * silently ignored.
         *<p>
         * Feature is disabled by default.
         *
         * @since 2.7
         */
        IGNORE_TRAILING_UNMAPPABLE(false),

        
Feature that allows skipping input lines that are completely empty or blank (composed only of whitespace),
instead of being decoded as lines of just a single column with an empty/blank String value (or,
of being decoded as lines of just a single column with empty String value (or,
depending on binding, `null`).

Feature is disabled by default.
Since:
2.10/**
         * Feature that allows skipping input lines that are completely empty or blank (composed only of whitespace),
         * instead of being decoded as lines of just a single column with an empty/blank String value (or,
         * of being decoded as lines of just a single column with empty String value (or,
         * depending on binding, `null`).
         *<p>
         * Feature is disabled by default.
         *
         * @since 2.10
         */
        SKIP_EMPTY_LINES(false),

        
Feature that allows there to be a trailing single extraneous data
column that is empty. When this feature is disabled, any extraneous
column, regardless of content will cause an exception to be thrown.
Disabling this feature is only useful when
IGNORE_TRAILING_UNMAPPABLE is also disabled.
/**
         * Feature that allows there to be a trailing single extraneous data
         * column that is empty. When this feature is disabled, any extraneous
         * column, regardless of content will cause an exception to be thrown.
         * Disabling this feature is only useful when
         * IGNORE_TRAILING_UNMAPPABLE is also disabled.
         */
        ALLOW_TRAILING_COMMA(true),

        
Feature that allows accepting "hash comments" by default, similar to CsvSchema.withAllowComments(boolean). If enabled, such comments are by default allowed on all columns of all documents. 
Since:
2.10/**
         * Feature that allows accepting "hash comments" by default, similar to
         * {@link CsvSchema#withAllowComments(boolean)}. If enabled, such comments
         * are by default allowed on all columns of all documents.
         *
         * @since 2.10
         */
        ALLOW_COMMENTS(false),
        
        
Feature that allows failing (with a CsvReadException) in cases where number of column values encountered is less than number of columns declared in active schema ("missing columns"). 
 Note that this feature has precedence over INSERT_NULLS_FOR_MISSING_COLUMNS 

Feature is disabled by default.
Since:
2.9/**
         * Feature that allows failing (with a {@link CsvReadException}) in cases
         * where number of column values encountered is less than number of columns
         * declared in active schema ("missing columns").
         *<p>
         * Note that this feature has precedence over {@link #INSERT_NULLS_FOR_MISSING_COLUMNS}
         *<p>
         * Feature is disabled by default.
         *
         * @since 2.9
         */
        FAIL_ON_MISSING_COLUMNS(false),
        
        
Feature that allows "inserting" virtual key / `null` value pairs in case
a row contains fewer columns than declared by configured schema.
This typically has the effect of forcing an explicit `null` assigment (or
corresponding "null value", if so configured) at databinding level.
If disabled, no extra work is done and values for "missing" columns are
not exposed as part of the token stream.
 Note that this feature is only considered if FAIL_ON_MISSING_COLUMNS is disabled. 

Feature is disabled by default.
Since:
2.9/**
         * Feature that allows "inserting" virtual key / `null` value pairs in case
         * a row contains fewer columns than declared by configured schema.
         * This typically has the effect of forcing an explicit `null` assigment (or
         * corresponding "null value", if so configured) at databinding level.
         * If disabled, no extra work is done and values for "missing" columns are
         * not exposed as part of the token stream.
         *<p>
         * Note that this feature is only considered if
         * {@link #FAIL_ON_MISSING_COLUMNS}
         * is disabled.
         *<p>
         * Feature is disabled by default.
         *
         * @since 2.9
         */
        INSERT_NULLS_FOR_MISSING_COLUMNS(false),

        
Feature that enables coercing an empty String to `null` Feature is disabled by default /**
         * Feature that enables coercing an empty {@link String} to `null`
         *
         * Feature is disabled by default
         */
        EMPTY_STRING_AS_NULL(false)
        ;

        final boolean _defaultState;
        final int _mask;
        
        
Method that calculates bit set (flags) of all features that
are enabled by default.
/**
         * Method that calculates bit set (flags) of all features that
         * are enabled by default.
         */
        public static int collectDefaults()
        {
            int flags = 0;
            for (Feature f : values()) {
                if (f.enabledByDefault()) {
                    flags |= f.getMask();
                }
            }
            return flags;
        }
        
        private Feature(boolean defaultState) {
            _defaultState = defaultState;
            _mask = (1 << ordinal());
        }

        @Override
        public boolean enabledByDefault() { return _defaultState; }
        @Override
        public boolean enabledIn(int flags) { return (flags & _mask) != 0; }
        @Override
        public int getMask() { return _mask; }
    }

    private final static CsvSchema EMPTY_SCHEMA;
    static {
        EMPTY_SCHEMA = CsvSchema.emptySchema();
    }

    
CSV is slightly different from defaults, having essentially untyped
scalars except if indicated by schema
Since:
2.12/**
     * CSV is slightly different from defaults, having essentially untyped
     * scalars except if indicated by schema
     *
     * @since 2.12
     */
    protected final static JacksonFeatureSet<StreamReadCapability> STREAM_READ_CAPABILITIES =
            DEFAULT_READ_CAPABILITIES
                .with(StreamReadCapability.UNTYPED_SCALARS)
            ;

    /*
    /**********************************************************************
    /* State constants
    /**********************************************************************
     */

    
Initial state before anything is read from document.
/**
     * Initial state before anything is read from document.
     */
    protected final static int STATE_DOC_START = 0;
    
    
State before logical start of a record, in which next token to return will be JsonToken.START_OBJECT (or if no Schema is provided, JsonToken.START_ARRAY). /**
     * State before logical start of a record, in which next
     * token to return will be {@link JsonToken#START_OBJECT}
     * (or if no Schema is provided, {@link JsonToken#START_ARRAY}).
     */
    protected final static int STATE_RECORD_START = 1;

    
State in which next entry will be available, returning either JsonToken.FIELD_NAME or value (depending on whether entries are expressed as Objects or just Arrays); or matching close marker. /**
     * State in which next entry will be available, returning
     * either {@link JsonToken#FIELD_NAME} or value
     * (depending on whether entries are expressed as
     * Objects or just Arrays); or
     * matching close marker.
     */
    protected final static int STATE_NEXT_ENTRY = 2;

    
State in which value matching field name will
be returned.
/**
     * State in which value matching field name will
     * be returned.
     */
    protected final static int STATE_NAMED_VALUE = 3;

    
State in which "unnamed" value (entry in an array)
will be returned, if one available; otherwise
end-array is returned.
/**
     * State in which "unnamed" value (entry in an array)
     * will be returned, if one available; otherwise
     * end-array is returned.
     */
    protected final static int STATE_UNNAMED_VALUE = 4;

    
State in which a column value has been determined to be of
an array type, and will need to be split into multiple
values. This can currently only occur for named values.
Since:
2.5/**
     * State in which a column value has been determined to be of
     * an array type, and will need to be split into multiple
     * values. This can currently only occur for named values.
     * 
     * @since 2.5
     */
    protected final static int STATE_IN_ARRAY = 5;

    
State in which we have encountered more column values than there should be,
and need to basically skip extra values if callers tries to advance parser
state.
Since:
2.6/**
     * State in which we have encountered more column values than there should be,
     * and need to basically skip extra values if callers tries to advance parser
     * state.
     *
     * @since 2.6
     */
    protected final static int STATE_SKIP_EXTRA_COLUMNS = 6;

    
State in which we should expose name token for a "missing column" (for which placeholder `null` value is to be added as well); see Feature.INSERT_NULLS_FOR_MISSING_COLUMNS for details. 
Since:
2.9/**
     * State in which we should expose name token for a "missing column"
     * (for which placeholder `null` value is to be added as well);
     * see {@link Feature#INSERT_NULLS_FOR_MISSING_COLUMNS} for details.
     *
     * @since 2.9
     */
    protected final static int STATE_MISSING_NAME = 7;

    
State in which we should expose `null` value token as a value for "missing" column; see Feature.INSERT_NULLS_FOR_MISSING_COLUMNS for details. 
Since:
2.9/**
     * State in which we should expose `null` value token as a value for
     * "missing" column;
     * see {@link Feature#INSERT_NULLS_FOR_MISSING_COLUMNS} for details.
     *
     * @since 2.9
     */
    protected final static int STATE_MISSING_VALUE = 8;

    
State in which end marker is returned; either null (if no array wrapping), or JsonToken.END_ARRAY for wrapping. This step will loop, returning series of nulls if nextToken is called multiple times. /**
     * State in which end marker is returned; either
     * null (if no array wrapping), or
     * {@link JsonToken#END_ARRAY} for wrapping.
     * This step will loop, returning series of nulls
     * if {@link #nextToken} is called multiple times.
     */
    protected final static int STATE_DOC_END = 9;

    /*
    /**********************************************************************
    /* Configuration
    /**********************************************************************
     */
    
    
Codec used for data binding when (if) requested.
/**
     * Codec used for data binding when (if) requested.
     */
    protected ObjectCodec _objectCodec;

    protected int _formatFeatures;

    
Definition of columns being read. Initialized to "empty" instance, which
has default configuration settings.
/**
     * Definition of columns being read. Initialized to "empty" instance, which
     * has default configuration settings.
     */
    protected CsvSchema _schema = EMPTY_SCHEMA;

    
Number of columns defined by schema.
/**
     * Number of columns defined by schema.
     */
    protected int _columnCount = 0;

    
Since:
2.12/**
     * @since 2.12
     */
    protected boolean _cfgEmptyStringAsNull;

    /*
    /**********************************************************************
    /* State
    /**********************************************************************
     */

    
Information about parser context, context in which
the next token is to be parsed (root, array, object).
/**
     * Information about parser context, context in which
     * the next token is to be parsed (root, array, object).
     */
    protected JsonReadContext _parsingContext;

    
Name of column that we exposed most recently, accessible after JsonToken.FIELD_NAME as well as value tokens immediately following field name. /**
     * Name of column that we exposed most recently, accessible after
     * {@link JsonToken#FIELD_NAME} as well as value tokens immediately
     * following field name.
     */
    protected String _currentName;

    
String value for the current column, if accessed.
/**
     * String value for the current column, if accessed.
     */
    protected String _currentValue;

    
Index of the column we are exposing
/**
     * Index of the column we are exposing
     */
    protected int _columnIndex;

    
Current logical state of the parser; one of STATE_
constants.
/**
     * Current logical state of the parser; one of <code>STATE_</code>
     * constants.
     */
    protected int _state = STATE_DOC_START;

    
We will hold on to decoded binary data, for duration of current event, so that multiple calls to JsonParser.getBinaryValue will not need to decode data more than once. /**
     * We will hold on to decoded binary data, for duration of
     * current event, so that multiple calls to
     * {@link #getBinaryValue} will not need to decode data more
     * than once.
     */
    protected byte[] _binaryValue;

    
Pointer to the first character of the next array value to return.
/**
     * Pointer to the first character of the next array value to return.
     */
    protected int _arrayValueStart;

    
Contents of the cell, to be split into distinct array values.
/**
     * Contents of the cell, to be split into distinct array values.
     */
    protected String _arrayValue;

    protected String _arraySeparator;

    protected String _nullValue;
    
    /*
    /**********************************************************************
    /* Helper objects
    /**********************************************************************
     */

    
Thing that actually reads the CSV content
/**
     * Thing that actually reads the CSV content
     */
    protected final CsvDecoder _reader;

    
Buffer that contains contents of all values after processing
of doubled-quotes, escaped characters.
/**
     * Buffer that contains contents of all values after processing
     * of doubled-quotes, escaped characters.
     */
    protected final TextBuffer _textBuffer;

    protected ByteArrayBuilder _byteArrayBuilder;

    /*
    /**********************************************************************
    /* Life-cycle
    /**********************************************************************
     */

    public CsvParser(CsvIOContext ctxt, int stdFeatures, int csvFeatures,
            ObjectCodec codec, Reader reader)
    {
        super(stdFeatures);
        if (reader == null) {
            throw new IllegalArgumentException("Can not pass `null` as `java.io.Reader` to read from");
        }
        _objectCodec = codec;
        _textBuffer =  ctxt.csvTextBuffer();
        DupDetector dups = JsonParser.Feature.STRICT_DUPLICATE_DETECTION.enabledIn(stdFeatures)
                ? DupDetector.rootDetector(this) : null;
        _formatFeatures = csvFeatures;
        _parsingContext = JsonReadContext.createRootContext(dups);
        _reader = new CsvDecoder(this, ctxt, reader, _schema, _textBuffer,
                stdFeatures, csvFeatures);
        _cfgEmptyStringAsNull = CsvParser.Feature.EMPTY_STRING_AS_NULL.enabledIn(csvFeatures);
    }

    /*
    /**********************************************************
    /* Versioned                                                                             
    /**********************************************************                 
     */

    @Override
    public Version version() {
        return PackageVersion.VERSION;
    }

    /*
    /**********************************************************
    /* Overrides: capability introspection methods
    /**********************************************************
     */

    @Override
    public boolean canUseSchema(FormatSchema schema) {
        return (schema instanceof CsvSchema);
    }

    @Override
    public boolean requiresCustomCodec() { return false;}

    @Override
    public boolean canReadObjectId() { return false; }

    @Override
    public boolean canReadTypeId() { return false; }

    @Override
    public JacksonFeatureSet<StreamReadCapability> getReadCapabilities() {
        return STREAM_READ_CAPABILITIES;
    }

    /*
    /**********************************************************                              
    /* Overridden methods
    /**********************************************************                              
     */

    @Override
    public ObjectCodec getCodec() {
        return _objectCodec;
    }

    @Override
    public void setCodec(ObjectCodec c) {
        _objectCodec = c;
    }

    @Override
    public void setSchema(FormatSchema schema)
    {
        if (schema instanceof CsvSchema) {
            _schema = (CsvSchema) schema;
            String str = _schema.getNullValueString();
            _nullValue = str;
        } else if (schema == null) {
            schema = EMPTY_SCHEMA;
        } else {
            super.setSchema(schema);
        }
        _columnCount = _schema.size();            
        _reader.setSchema(_schema);
    }

    @Override
    public int releaseBuffered(Writer out) throws IOException {
        return _reader.releaseBuffered(out);
    }

    @Override
    public boolean isClosed() { return _reader.isClosed(); }

    @Override
    public void close() throws IOException { _reader.close(); }

    /*                                                                                       
    /**********************************************************                              
    /* FormatFeature support                                                                             
    /**********************************************************                              
     */

    @Override
    public int getFormatFeatures() {
        return _formatFeatures;
    }

    @Override
    public JsonParser overrideFormatFeatures(int values, int mask) {
        int oldF = _formatFeatures;
        int newF = (_formatFeatures & ~mask) | (values & mask);

        if (oldF != newF) {
            _formatFeatures = newF;
            _reader.overrideFormatFeatures(newF);
            _cfgEmptyStringAsNull = CsvParser.Feature.EMPTY_STRING_AS_NULL.enabledIn(_formatFeatures);
        }
        return this;
    }

    /*
    /***************************************************
    /* Public API, configuration
    /***************************************************
     */

    
Method for enabling specified CSV feature (check Feature for list of features) /**
     * Method for enabling specified CSV feature
     * (check {@link Feature} for list of features)
     */
    public JsonParser enable(Feature f)
    {
        _formatFeatures |= f.getMask();
        _cfgEmptyStringAsNull = CsvParser.Feature.EMPTY_STRING_AS_NULL.enabledIn(_formatFeatures);
        return this;
    }

    
Method for disabling specified CSV feature (check Feature for list of features) /**
     * Method for disabling specified  CSV feature
     * (check {@link Feature} for list of features)
     */
    public JsonParser disable(Feature f)
    {
        _formatFeatures &= ~f.getMask();
        _cfgEmptyStringAsNull = CsvParser.Feature.EMPTY_STRING_AS_NULL.enabledIn(_formatFeatures);
        return this;
    }

    
Method for enabling or disabling specified CSV feature (check Feature for list of features) /**
     * Method for enabling or disabling specified CSV feature
     * (check {@link Feature} for list of features)
     */
    public JsonParser configure(Feature f, boolean state)
    {
        if (state) {
            enable(f);
        } else {
            disable(f);
        }
        return this;
    }

    
Method for checking whether specified CSV Feature is enabled. /**
     * Method for checking whether specified CSV {@link Feature}
     * is enabled.
     */
    public boolean isEnabled(Feature f) {
        return (_formatFeatures & f.getMask()) != 0;
    }

    
Accessor for getting active schema definition: it may be
"empty" (no column definitions), but will never be null
since it defaults to an empty schema (and default configuration)
/**
     * Accessor for getting active schema definition: it may be
     * "empty" (no column definitions), but will never be null
     * since it defaults to an empty schema (and default configuration)
     */
    @Override
    public CsvSchema getSchema() {
        return _schema;
    }
    
    /*
    /**********************************************************
    /* Location info
    /**********************************************************
     */
    
    @Override
    public JsonStreamContext getParsingContext() {
        return _parsingContext;
    }

    @Override
    public JsonLocation getTokenLocation() {
        return _reader.getTokenLocation();
    }

    @Override
    public JsonLocation getCurrentLocation() {
        return _reader.getCurrentLocation();
    }

    @Override
    public Object getInputSource() {
        return _reader.getInputSource();
    }
    
    /*
    /**********************************************************
    /* Parsing, basic
    /**********************************************************
     */

    
We need to override this method to support coercion from basic
String value into array, in cases where schema does not
specify actual type.
/**
     * We need to override this method to support coercion from basic
     * String value into array, in cases where schema does not
     * specify actual type.
     */
    @Override
    public boolean isExpectedStartArrayToken() {
        if (_currToken == null) {
            return false;
        }
        switch (_currToken.id()) {
        case JsonTokenId.ID_FIELD_NAME:
        case JsonTokenId.ID_START_OBJECT:
        case JsonTokenId.ID_END_OBJECT:
        case JsonTokenId.ID_END_ARRAY:
            return false;
        case JsonTokenId.ID_START_ARRAY:
            return true;
        }
        // Otherwise: may coerce into array, iff we have essentially "untyped" column
        if (_columnIndex < _columnCount) {
            CsvSchema.Column column = _schema.column(_columnIndex);
            if (column.getType() == CsvSchema.ColumnType.STRING) {
                _startArray(column);
                return true;
            }
        }
        // 30-Dec-2014, tatu: Seems like it should be possible to allow this
        //   in non-array-wrapped case too (for 2.5), so let's try that:
        else if (_currToken == JsonToken.VALUE_STRING) {
            _startArray(CsvSchema.Column.PLACEHOLDER);
            return true;
        }
        return false;
    }

    @Override // since 2.12
    public boolean isExpectedNumberIntToken()
    {
        JsonToken t = _currToken;
        if (t == JsonToken.VALUE_STRING) {
            if (_reader.isExpectedNumberIntToken()) {
                _currToken = JsonToken.VALUE_NUMBER_INT;
                return true;
            }
            return false;
        }
        return (t == JsonToken.VALUE_NUMBER_INT);
    }

    @Override
    public String getCurrentName() throws IOException {
        return _currentName;
    }

    @Override
    public void overrideCurrentName(String name) {
        _currentName = name;
    }

    @Override
    public JsonToken nextToken() throws IOException
    {
        _binaryValue = null;
        switch (_state) {
        case STATE_DOC_START:
            return (_currToken = _handleStartDoc());
        case STATE_RECORD_START:
            return (_currToken = _handleRecordStart());
        case STATE_NEXT_ENTRY:
            return (_currToken = _handleNextEntry());
        case STATE_NAMED_VALUE:
            return (_currToken = _handleNamedValue());
        case STATE_UNNAMED_VALUE:
            return (_currToken = _handleUnnamedValue());
        case STATE_IN_ARRAY:
            return (_currToken = _handleArrayValue());
        case STATE_SKIP_EXTRA_COLUMNS:
            // Need to just skip whatever remains
            return _skipUntilEndOfLine();
        case STATE_MISSING_NAME:
            return (_currToken = _handleMissingName());
        case STATE_MISSING_VALUE:
            return (_currToken = _handleMissingValue());
        case STATE_DOC_END:
            _reader.close();
            if (_parsingContext.inRoot()) {
                return null;
            }
            // should always be in array, actually... but:
            boolean inArray = _parsingContext.inArray();
            _parsingContext = _parsingContext.getParent();
            return inArray ? JsonToken.END_ARRAY : JsonToken.END_OBJECT;
        default:
            throw new IllegalStateException();
        }
    }

    /*
    /**********************************************************
    /* Parsing, optimized methods
    /**********************************************************
     */

    @Override
    public boolean nextFieldName(SerializableString str) throws IOException {
        // Optimize for expected case of getting FIELD_NAME:
        if (_state == STATE_NEXT_ENTRY) {
            _binaryValue = null;
            JsonToken t = _handleNextEntry();
            _currToken = t;
            if (t == JsonToken.FIELD_NAME) {
                return str.getValue().equals(_currentName);
            }
            return false;
        }
        // unlikely, but verify just in case
        return (nextToken() == JsonToken.FIELD_NAME) && str.getValue().equals(getCurrentName());
    }

    @Override
    public String nextFieldName() throws IOException
    {
        // Optimize for expected case of getting FIELD_NAME:
        if (_state == STATE_NEXT_ENTRY) {
            _binaryValue = null;
            JsonToken t = _handleNextEntry();
            _currToken = t;
            if (t == JsonToken.FIELD_NAME) {
                return _currentName;
            }
            return null;
        }
        // unlikely, but verify just in case
        return (nextToken() == JsonToken.FIELD_NAME) ? getCurrentName() : null;
    }

    @Override
    public String nextTextValue() throws IOException
    {
        _binaryValue = null;
        JsonToken t;
        if (_state == STATE_NAMED_VALUE) {
            _currToken = t = _handleNamedValue();
            if (t == JsonToken.VALUE_STRING) {
                return _currentValue;
            }
        } else if (_state == STATE_UNNAMED_VALUE) {
            _currToken = t = _handleUnnamedValue();
            if (t == JsonToken.VALUE_STRING) {
                return _currentValue;
            }
        } else {
            t = nextToken();
            if (t == JsonToken.VALUE_STRING) {
                return getText();
            }
        }
        return null;
    }

    /*
    /**********************************************************
    /* Parsing, helper methods, regular
    /**********************************************************
     */

    
Method called to process the expected header line
/**
     * Method called to process the expected header line
     */
    protected void _readHeaderLine() throws IOException {
        /*
            When the header line is present and the settings ask for it
            to be processed, two different options are possible:

            a) The schema has been populated.  In this case, build a new
               schema where the order matches the *actual* order in which
               the given CSV file offers its columns, if _schema.reordersColumns()
               is set to true; there cases the consumer of the CSV file
               knows about the columns but not necessarily the order in
               which they are defined.

            b) The schema has not been populated.  In this case, build a
               default schema based on the columns found in the header.
         */

        if (_schema.size() > 0 && !_schema.reordersColumns()) {
            if (_schema.strictHeaders()) {
                String name;
                int ix = 0;
                for (CsvSchema.Column column : _schema._columns) {
                    name = _reader.nextString();
                    ++ix;
                    if (name == null) {
                        _reportError(String.format("Missing header column #%d, expecting \"%s\"", ix, column.getName()));
                    } else if (!column.getName().equals(name)) {
                        _reportError(String.format(
"Mismatched header column #%d: expected \"%s\", actual \"%s\"", ix, column.getName(), name));
                }
                }
                if ((name = _reader.nextString()) != null) {
                    _reportError(String.format("Extra header %s", name));
                }
            } else {
                int allowed = MAX_COLUMNS;
                while (_reader.nextString() != null) {
                    // If we don't care about validation, just skip. But protect against infinite loop
                    if (--allowed < 0) {
                        _reportError("Internal error: skipped "+MAX_COLUMNS+" header columns");
                    }
                }
            }
            return;
        }

        // either the schema is empty or reorder columns flag is set
        String name;
        CsvSchema.Builder builder = _schema.rebuild().clearColumns();
        int count = 0;

        while ((name = _reader.nextString()) != null) {
            // one more thing: always trim names, regardless of config settings
            name = name.trim();
            // See if "old" schema defined type; if so, use that type...
            CsvSchema.Column prev = _schema.column(name);
            if (prev != null) {
                builder.addColumn(name, prev.getType());
            } else {
                builder.addColumn(name);
            }
            if (++count > MAX_COLUMNS) {
                _reportError("Internal error: reached maximum of "+MAX_COLUMNS+" header columns");
            }
        }

        // [dataformats-text#204]: Drop trailing empty name if so instructed
        if (CsvParser.Feature.ALLOW_TRAILING_COMMA.enabledIn(_formatFeatures)) {
            builder.dropLastColumnIfEmpty();
        }

        // Ok: did we get any  columns?
        CsvSchema newSchema = builder.build();
        int size = newSchema.size();
        if (size < 2) { // 1 just because we may get 'empty' header name
            String first = (size == 0) ? "" : newSchema.columnName(0).trim();
            if (first.length() == 0) {
                _reportCsvMappingError("Empty header line: can not bind data");
            }
        }
        // otherwise we will use what we got
        setSchema(builder.build());
    }

    
Method called to handle details of initializing things to return
the very first token.
/**
     * Method called to handle details of initializing things to return
     * the very first token.
     */
    protected JsonToken _handleStartDoc() throws IOException
    {
        // also, if comments enabled, or skip empty lines, may need to skip leading ones
        _reader.skipLinesWhenNeeded();
        // First things first: are we expecting header line? If so, read, process
        if (_schema.usesHeader()) {
            _readHeaderLine();
            _reader.skipLinesWhenNeeded();
        }
        // and if we are to skip the first data line, skip it
        if (_schema.skipsFirstDataRow()) {
            _reader.skipLine();
            _reader.skipLinesWhenNeeded();
        }

        // Only one real complication, actually; empty documents (zero bytes).
        // Those have no entries. Should be easy enough to detect like so:
        final boolean wrapAsArray = Feature.WRAP_AS_ARRAY.enabledIn(_formatFeatures);
        if (!_reader.hasMoreInput()) {
            _state = STATE_DOC_END;
            // but even empty sequence must still be wrapped in logical array
            if (wrapAsArray) {
                _parsingContext = _reader.childArrayContext(_parsingContext);
                return JsonToken.START_ARRAY;
            }
            return null;
        }
        
        if (wrapAsArray) {
            _parsingContext = _reader.childArrayContext(_parsingContext);
            _state = STATE_RECORD_START;
            return JsonToken.START_ARRAY;
        }
        // otherwise, same as regular new entry...
        return _handleRecordStart();
    }

    protected JsonToken _handleRecordStart() throws IOException
    {
        _columnIndex = 0;
        if (_columnCount == 0) { // no schema; exposed as an array
            _state = STATE_UNNAMED_VALUE;
            _parsingContext = _reader.childArrayContext(_parsingContext);
            return JsonToken.START_ARRAY;
        }
        // otherwise, exposed as an Object
        _parsingContext = _reader.childObjectContext(_parsingContext);
        _state = STATE_NEXT_ENTRY;
        return JsonToken.START_OBJECT;
    }

    protected JsonToken _handleNextEntry() throws IOException
    {
        // NOTE: only called when we do have real Schema
        String next;

        try {
            next = _reader.nextString();
        } catch (IOException e) {
            // 12-Oct-2015, tatu: Need to resync here as well...
            _state = STATE_SKIP_EXTRA_COLUMNS;
            throw e;
        }

        if (next == null) { // end of record or input...
            // 16-Mar-2017, tatu: [dataformat-csv#137] Missing column(s)?
            if (_columnIndex < _columnCount) {
                return _handleMissingColumns();
            }
            return _handleObjectRowEnd();
        }
        _currentValue = next;
        if (_columnIndex >= _columnCount) {
            return _handleExtraColumn(next);
        }
        _state = STATE_NAMED_VALUE;
        _currentName = _schema.columnName(_columnIndex);
        return JsonToken.FIELD_NAME;
    }

    protected JsonToken _handleNamedValue() throws IOException
    {
        // 06-Oct-2015, tatu: During recovery, may get past all regular columns,
        //    but we also need to allow access past... sort of.
        if (_columnIndex < _columnCount) {
            CsvSchema.Column column = _schema.column(_columnIndex);
            ++_columnIndex;
            if (column.isArray()) {
                _startArray(column);
                return JsonToken.START_ARRAY;
            }
        }
        _state = STATE_NEXT_ENTRY;
        if (_nullValue != null) {
            if (_nullValue.equals(_currentValue)) {
                return JsonToken.VALUE_NULL;
            }
        }
        if (_cfgEmptyStringAsNull && "".equals(_currentValue)) {
            return JsonToken.VALUE_NULL;
        }
        return JsonToken.VALUE_STRING;
    }

    protected JsonToken _handleUnnamedValue() throws IOException
    {
        String next = _reader.nextString();
        if (next == null) { // end of record or input...
            _parsingContext = _parsingContext.getParent();
            if (!_reader.startNewLine()) { // end of whole thing...
                _state = STATE_DOC_END;
            } else {
                // no, just end of record
                _state = STATE_RECORD_START;
            }
            return JsonToken.END_ARRAY;
        }
        // state remains the same
        _currentValue = next;
        ++_columnIndex;
        if (_nullValue != null) {
            if (_nullValue.equals(next)) {
                return JsonToken.VALUE_NULL;
            }
        }
        if (_cfgEmptyStringAsNull && "".equals(_currentValue)) {
            return JsonToken.VALUE_NULL;
        }
        return JsonToken.VALUE_STRING;
    }

    protected JsonToken _handleArrayValue() throws IOException
    {
        int offset = _arrayValueStart;
        if (offset < 0) { // just returned last value
            _parsingContext = _parsingContext.getParent();
            // no arrays in arrays (at least for now), so must be back to named value
            _state = STATE_NEXT_ENTRY;
             return JsonToken.END_ARRAY;
        }
        int end = _arrayValue.indexOf(_arraySeparator, offset);

        if (end < 0) { // last value
            _arrayValueStart = end; // end marker, regardless

            // 11-Feb-2015, tatu: Tricky, As per [dataformat-csv#66]; empty Strings really
            //     should not emit any values. Not sure if trim
            if (offset == 0) { // no separator
                // for now, let's use trimming for checking
                if (_arrayValue.isEmpty() || _arrayValue.trim().isEmpty()) {
                    _parsingContext = _parsingContext.getParent();
                    _state = STATE_NEXT_ENTRY;
                    return JsonToken.END_ARRAY;
                }
                _currentValue = _arrayValue;
            } else {
                _currentValue = _arrayValue.substring(offset);
            }
        } else {
            _currentValue = _arrayValue.substring(offset, end);
            _arrayValueStart = end+_arraySeparator.length();
        }
        if (isEnabled(Feature.TRIM_SPACES)) {
            _currentValue = _currentValue.trim();
        }
        if (_nullValue != null) {
            if (_nullValue.equals(_currentValue)) {
                return JsonToken.VALUE_NULL;
            }
        }
        if (_cfgEmptyStringAsNull && "".equals(_currentValue)) {
            return JsonToken.VALUE_NULL;
        }
        return JsonToken.VALUE_STRING;
    }

    /*
    /**********************************************************
    /* Parsing, helper methods, extra column(s)
    /**********************************************************
     */

    
Helper method called when an extraneous column value is found.
What happens then depends on configuration, but there are three
main choices: ignore value (and rest of line); expose extra value
as "any property" using configured name, or throw an exception.
Since:
2.7/**
     * Helper method called when an extraneous column value is found.
     * What happens then depends on configuration, but there are three
     * main choices: ignore value (and rest of line); expose extra value
     * as "any property" using configured name, or throw an exception.
     *
     * @since 2.7
     */
    protected JsonToken _handleExtraColumn(String value) throws IOException
    {
        // If "any properties" enabled, expose as such
        String anyProp = _schema.getAnyPropertyName();
        if (anyProp != null) {
            _currentName = anyProp;
            _state = STATE_NAMED_VALUE;
            return JsonToken.FIELD_NAME;
        }
        _currentName = null;
        // With [dataformat-csv#95] we'll simply ignore extra
        if (Feature.IGNORE_TRAILING_UNMAPPABLE.enabledIn(_formatFeatures)) {
            _state = STATE_SKIP_EXTRA_COLUMNS;
            return _skipUntilEndOfLine();
        }

        // 14-Mar-2012, tatu: As per [dataformat-csv#1], let's allow one specific case
        // of extra: if we get just one all-whitespace entry, that can be just skipped
        _state = STATE_SKIP_EXTRA_COLUMNS;
        if (_columnIndex == _columnCount && Feature.ALLOW_TRAILING_COMMA.enabledIn(_formatFeatures)) {
            value = value.trim();
            if (value.isEmpty()) {
                // if so, need to verify we then get the end-of-record;
                // easiest to do by just calling ourselves again...
                String next = _reader.nextString();
                if (next == null) { // should end of record or input
                    return _handleObjectRowEnd();
                }
            }
        }
        // 21-May-2015, tatu: Need to enter recovery mode, to skip remainder of the line
        return _reportCsvMappingError("Too many entries: expected at most %d (value #%d (%d chars) \"%s\")",
                _columnCount, _columnIndex, value.length(), value);
    }

    /*
    /**********************************************************
    /* Parsing, helper methods, missing column(s)
    /**********************************************************
     */

    
Helper method called when end of row occurs before finding values for
all schema-specified columns.
Since:
2.9/**
     * Helper method called when end of row occurs before finding values for
     * all schema-specified columns.
     *
     * @since 2.9
     */
    protected JsonToken _handleMissingColumns() throws IOException
    {
        if (Feature.FAIL_ON_MISSING_COLUMNS.enabledIn(_formatFeatures)) {
            // First: to allow recovery, set states to expose next line, if any
            _handleObjectRowEnd();
            // and then report actual problem
            return _reportCsvMappingError("Not enough column values: expected %d, found %d",
                    _columnCount, _columnIndex);
        }
        if (Feature.INSERT_NULLS_FOR_MISSING_COLUMNS.enabledIn(_formatFeatures)) {
            _state = STATE_MISSING_VALUE;
            _currentName = _schema.columnName(_columnIndex);
            _currentValue = null;
            return JsonToken.FIELD_NAME;
        }
        return _handleObjectRowEnd();
    }

    protected JsonToken _handleMissingName() throws IOException
    {
        if (++_columnIndex < _columnCount) {
            _state = STATE_MISSING_VALUE;
            _currentName = _schema.columnName(_columnIndex);
            // _currentValue already set to null earlier
            return JsonToken.FIELD_NAME;
        }
        return _handleObjectRowEnd();
    }

    protected JsonToken _handleMissingValue() throws IOException
    {
        _state = STATE_MISSING_NAME;
        return JsonToken.VALUE_NULL;
    }

    /*
    /**********************************************************
    /* Parsing, helper methods: row end handling, recover
    /**********************************************************
     */

    
Helper method called to handle details of state update when end of logical
record occurs.
Since:
2.9/**
     * Helper method called to handle details of state update when end of logical
     * record occurs.
     *
     * @since 2.9
     */
    protected final JsonToken _handleObjectRowEnd() throws IOException
    {
        _parsingContext = _parsingContext.getParent();
        if (!_reader.startNewLine()) {
            _state = STATE_DOC_END;
        } else {
            _state = STATE_RECORD_START;
        }
        return JsonToken.END_OBJECT;
    }

    protected final JsonToken _skipUntilEndOfLine() throws IOException
    {
        while (_reader.nextString() != null) { }

        // But once we hit the end of the logical line, get out
        // NOTE: seems like we should always be within Object, but let's be conservative
        // and check just in case
        _parsingContext = _parsingContext.getParent();
        _state = _reader.startNewLine() ? STATE_RECORD_START : STATE_DOC_END;
        return (_currToken = _parsingContext.inArray()
                ? JsonToken.END_ARRAY : JsonToken.END_OBJECT);
    }

    /*
    /**********************************************************
    /* String value handling
    /**********************************************************
     */
    
    
    // For now we do not store char[] representation...
    @Override
    public boolean hasTextCharacters() {
        if (_currToken == JsonToken.FIELD_NAME) {
            return false;
        }
        return _textBuffer.hasTextAsCharacters();
    }

    @Override
    public String getText() throws IOException {
        if (_currToken == JsonToken.FIELD_NAME) {
            return _currentName;
        }
        // 08-Sep-2020, tatu: Used to check for empty String wrt EMPTY_STRING_AS_NULL
        //    here, but now demoted to actual "nextToken()" handling
        return _currentValue;
    }

    @Override
    public char[] getTextCharacters() throws IOException {
        if (_currToken == JsonToken.FIELD_NAME) {
            return _currentName.toCharArray();
        }
        return _textBuffer.contentsAsArray();
    }

    @Override
    public int getTextLength() throws IOException {
        if (_currToken == JsonToken.FIELD_NAME) {
            return _currentName.length();
        }
        return _textBuffer.size();
    }

    @Override
    public int getTextOffset() throws IOException {
        return 0;
    }

    @Override // since 2.8
    public int getText(Writer w) throws IOException {
        String value = (_currToken == JsonToken.FIELD_NAME) ?
                _currentName : _currentValue;
        if (value == null) {
            return 0;
        }
        w.write(value);
        return value.length();
    }
    
    /*
    /**********************************************************************
    /* Binary (base64)
    /**********************************************************************
     */

    @Override
    public Object getEmbeddedObject() throws IOException {
        // in theory may access binary data using this method so...
        return _binaryValue;
    }

    @SuppressWarnings("resource")
    @Override
    public byte[] getBinaryValue(Base64Variant variant) throws IOException
    {
        if (_binaryValue == null) {
            if (_currToken != JsonToken.VALUE_STRING) {
                _reportCsvMappingError("Current token (%s) not VALUE_STRING, can not access as binary", _currToken);
            }
            ByteArrayBuilder builder = _getByteArrayBuilder();
            _decodeBase64(_currentValue, builder, variant);
            _binaryValue = builder.toByteArray();
        }
        return _binaryValue;
    }

    /*
    /**********************************************************************
    /* Number accessors
    /**********************************************************************
     */

    @Override
    public NumberType getNumberType() throws IOException {
        return _reader.getNumberType();
    }

    @Override
    public Number getNumberValue() throws IOException {
        return _reader.getNumberValue(false);
    }

    @Override
    public Number getNumberValueExact() throws IOException {
        return _reader.getNumberValue(true);
    }

    @Override
    public int getIntValue() throws IOException {
        return _reader.getIntValue();
    }

    @Override
    public long getLongValue() throws IOException {
        return _reader.getLongValue();
    }

    @Override
    public BigInteger getBigIntegerValue() throws IOException {
        return _reader.getBigIntegerValue();
    }

    @Override
    public float getFloatValue() throws IOException {
        return _reader.getFloatValue();
    }

    @Override
    public double getDoubleValue() throws IOException {
        return _reader.getDoubleValue();
    }

    @Override
    public BigDecimal getDecimalValue() throws IOException {
        return _reader.getDecimalValue();
    }

    /*
    /**********************************************************************
    /* Helper methods from base class
    /**********************************************************************
     */

    @Override
    protected void _handleEOF() throws JsonParseException {
        // I don't think there's problem with EOFs usually; except maybe in quoted stuff?
        _reportInvalidEOF(": expected closing quote character", null);
    }

    /*
    /**********************************************************
    /* Internal methods, error reporting
    /**********************************************************
     */

    
Method called when there is a problem related to mapping data
(compared to a low-level generation); if so, should be surfaced
as 
Since:
2.9/**
     * Method called when there is a problem related to mapping data
     * (compared to a low-level generation); if so, should be surfaced
     * as 
     *
     * @since 2.9
     */
    public <T> T _reportCsvMappingError(String msg, Object... args) throws IOException {
        if (args.length > 0) {
            msg = String.format(msg, args);
        }
        throw CsvReadException.from(this, msg, _schema);
    }

    public void _reportParsingError(String msg)  throws JsonProcessingException {
        super._reportError(msg);
    }

    public void _reportUnexpectedCsvChar(int ch, String msg)  throws JsonProcessingException {
        super._reportUnexpectedChar(ch, msg);
    }

    /*
    /**********************************************************************
    /* Internal methods
    /**********************************************************************
     */
    
    public ByteArrayBuilder _getByteArrayBuilder()
    {
        if (_byteArrayBuilder == null) {
            _byteArrayBuilder = new ByteArrayBuilder();
        } else {
            _byteArrayBuilder.reset();
        }
        return _byteArrayBuilder;
    }

    protected void _startArray(CsvSchema.Column column)
    {
        _currToken = JsonToken.START_ARRAY;
        _parsingContext = _parsingContext.createChildArrayContext(_reader.getCurrentRow(),
                _reader.getCurrentColumn());
        _state = STATE_IN_ARRAY;
        _arrayValueStart = 0;
        _arrayValue = _currentValue;
        String sep = column.getArrayElementSeparator();
        if (sep.isEmpty()) {
            sep = _schema.getArrayElementSeparator();
        }
        _arraySeparator = sep;
    }
}