package org.djutils.data.csv;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

import org.djutils.data.DataColumn;
import org.djutils.data.DataRecord;
import org.djutils.data.DataTable;
import org.djutils.data.ListDataTable;
import org.djutils.data.SimpleDataColumn;
import org.djutils.data.serialization.TextSerializationException;
import org.djutils.data.serialization.TextSerializer;
import org.djutils.exceptions.Throw;
import org.djutils.primitives.Primitive;

import com.opencsv.CSVParserBuilder;
import com.opencsv.CSVReader;
import com.opencsv.CSVReaderBuilder;
import com.opencsv.CSVWriter;
import com.opencsv.ICSVWriter;
import com.opencsv.exceptions.CsvValidationException;

/**
 * CSVData takes care of reading and writing of table data in CSV format. The class can be used, e.g., as follows:
 * 
 * <pre>
 * DataTable dataTable = new ListDataTable("data", "dataTable", columns);
 * Writer writer = new FileWriter("c:/data/data.csv");
 * Writer metaWriter = new FileWriter("c:/data/data.meta.csv");
 * CSVData.writeData(writer, metaWriter, dataTable);
 * </pre>
 * 
 * Copyright (c) 2020-2020 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
 * for project information <a href="https://djutils.org" target="_blank"> https://djutils.org</a>. The DJUTILS project is
 * distributed under a three-clause BSD-style license, which can be found at
 * <a href="https://djutils.org/docs/license.html" target="_blank"> https://djutils.org/docs/license.html</a>. <br>
 * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
 * @author <a href="https://www.tudelft.nl/pknoppers">Peter Knoppers</a>
 * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
 */
public final class CSVData
{
    /**
     * Utility class, no public constructor.
     */
    private CSVData()
    {
        // utility class
    }

    /**
     * Write the data from the data table in CSV format. The writer writes the data, whereas the metaWriter writes the metadata.
     * The metadata consists of a CSV file with three columns: the id, the description, and the class. The first row after the
     * header contains the id, description, and class of the data table itself. The second and further rows contain information
     * about the columns of the data table.
     * @param writer Writer; the writer that writes the data, e.g. to a file
     * @param metaWriter Writer; the writer for the metadata
     * @param dataTable the data table to write
     * @param separator char; the delimiter to use for separating entries
     * @param quotechar char; the character to use for quoted elements
     * @param escapechar char; the character to use for escaping quotechars or escapechars
     * @param lineEnd String; the line feed terminator to use
     * @throws IOException on I/O error when writing the data
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static void writeData(final Writer writer, final Writer metaWriter, final DataTable dataTable, final char separator,
            final char quotechar, final char escapechar, final String lineEnd) throws IOException, TextSerializationException
    {
        // Write the metadata file
        CSVWriter csvMetaWriter = null;
        CSVWriter csvWriter = null;
        try
        {
            csvMetaWriter = new CSVWriter(metaWriter, separator, quotechar, escapechar, lineEnd);
            csvMetaWriter.writeNext(new String[] { "id", "description", "className" });
            csvMetaWriter
                    .writeNext(new String[] { dataTable.getId(), dataTable.getDescription(), dataTable.getClass().getName() });
            for (DataColumn<?> column : dataTable.getColumns())
            {
                csvMetaWriter
                        .writeNext(new String[] { column.getId(), column.getDescription(), column.getValueType().getName() });
            }

            // Assemble the serializer array
            TextSerializer<?>[] serializers = new TextSerializer[dataTable.getNumberOfColumns()];
            for (int i = 0; i < dataTable.getNumberOfColumns(); i++)
            {
                DataColumn<?> column = dataTable.getColumns().get(i);
                serializers[i] = TextSerializer.resolve(column.getValueType());
            }

            // Write the data file
            csvWriter = new CSVWriter(writer, separator, quotechar, escapechar, lineEnd);
            csvWriter.writeNext(dataTable.getColumnIds());
            String[] textFields = new String[dataTable.getNumberOfColumns()];
            for (DataRecord record : dataTable)
            {
                Object[] values = record.getValues();
                for (int i = 0; i < dataTable.getNumberOfColumns(); i++)
                {
                    textFields[i] = serializers[i].serialize(values[i]);
                }
                csvWriter.writeNext(textFields);
            }
        }
        finally
        {
            if (null != csvMetaWriter)
            {
                csvMetaWriter.close();
            }
            if (null != csvWriter)
            {
                csvWriter.close();
            }
        }
    }

    /**
     * Write the data from the data table in CSV format. The writer writes the data, whereas the metaWriter writes the metadata.
     * The metadata consists of a CSV file with three columns: the id, the description, and the class. The first row after the
     * header contains the id, description, and class of the data table itself. The second and further rows contain information
     * about the columns of the data table.
     * @param writer Writer; the writer that writes the data, e.g. to a file
     * @param metaWriter Writer; the writer for the metadata
     * @param dataTable the data table to write
     * @throws IOException on I/O error when writing the data
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static void writeData(final Writer writer, final Writer metaWriter, final DataTable dataTable)
            throws IOException, TextSerializationException
    {
        writeData(writer, metaWriter, dataTable, ICSVWriter.DEFAULT_SEPARATOR, ICSVWriter.DEFAULT_QUOTE_CHARACTER, '\\',
                ICSVWriter.DEFAULT_LINE_END);
    }

    /**
     * Write the data from the data table in CSV format.
     * @param filename String; the file name to write the data to
     * @param metaFilename String; the file name to write the metadata to
     * @param dataTable the data table to write
     * @throws IOException on I/O error when writing the data
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static void writeData(final String filename, final String metaFilename, final DataTable dataTable)
            throws IOException, TextSerializationException
    {
        FileWriter fw = null;
        FileWriter mfw = null;
        try
        {
            fw = new FileWriter(filename);
            mfw = new FileWriter(metaFilename);
            writeData(fw, mfw, dataTable);
        }
        finally
        {
            if (null != fw)
            {
                fw.close(); // May have already been closed when the CSV writer was closed, but multiple close is harmless
            }
            if (null != mfw)
            {
                mfw.close();
            }
        }
    }

    /**
     * Read the data from the CSV-file into the data table. Use the metadata to reconstruct the data table.
     * @param reader Reader; the reader that can read the data, e.g. from a file
     * @param metaReader Reader; the writer for the metadata
     * @return dataTable the data table reconstructed from the meta data and filled with the data
     * @param separator char; the delimiter to use for separating entries
     * @param quotechar char; the character to use for quoted elements
     * @param escapechar char; the character to use for escaping quotechars or escapechars
     * @param lineEnd String; the line feed terminator to use
     * @throws IOException on I/O error when reading the data
     * @throws CsvValidationException when the CSV data was not formatted right
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static DataTable readData(final Reader reader, final Reader metaReader, final char separator, final char quotechar,
            final char escapechar, final String lineEnd) throws IOException, CsvValidationException, TextSerializationException
    {
        CSVReader csvMetaReader = null;
        CSVReader csvReader = null;
        try
        {
            // Read the metadata file and reconstruct the data table
            csvMetaReader = new CSVReaderBuilder(metaReader).withCSVParser(
                    new CSVParserBuilder().withSeparator(separator).withQuoteChar(quotechar).withEscapeChar(escapechar).build())
                    .build();
            List<DataColumn<?>> columns = new ArrayList<>();
            String[] header = csvMetaReader.readNext();
            Throw.when(
                    header.length != 3 || !"id".equals(header[0]) || !"description".equals(header[1])
                            || !"className".equals(header[2]),
                    IOException.class, "header of the metafile does not contain 'id, description, className' as fields");

            // table metadata
            String[] tableLine = csvMetaReader.readNext();
            Throw.when(tableLine == null, IOException.class, "no table information in the metafile");
            Throw.when(tableLine.length != 3, IOException.class, "table data in the metafile does not contain 3 fields");
            Throw.when(!tableLine[2].endsWith("ListDataTable"), IOException.class,
                    "Currently, this method can only recreate a ListDataTable");

            // column metadata
            String[] line = csvMetaReader.readNext();
            while (line != null)
            {
                Throw.when(line.length != 3, IOException.class, "column data in the metafile does not contain 3 fields");
                String type = line[2];
                Class<?> valueClass = Primitive.forName(type);
                if (valueClass == null)
                {
                    try
                    {
                        valueClass = Class.forName(type);
                    }
                    catch (ClassNotFoundException exception)
                    {
                        throw new IOException("Could not find class " + type, exception);
                    }
                }
                @SuppressWarnings({ "rawtypes", "unchecked" })
                DataColumn<?> column = new SimpleDataColumn(line[0], line[1], valueClass);
                columns.add(column);
                line = csvMetaReader.readNext();
            }

            // create DataTable
            ListDataTable dataTable = new ListDataTable(tableLine[0], tableLine[1], columns);

            // Assemble the serializer array
            TextSerializer<?>[] serializers = new TextSerializer[dataTable.getNumberOfColumns()];
            for (int i = 0; i < dataTable.getNumberOfColumns(); i++)
            {
                DataColumn<?> column = dataTable.getColumns().get(i);
                serializers[i] = TextSerializer.resolve(column.getValueType());
            }

            // Read the data file header
            csvReader = new CSVReaderBuilder(reader).withCSVParser(
                    new CSVParserBuilder().withSeparator(separator).withQuoteChar(quotechar).withEscapeChar(escapechar).build())
                    .build();
            header = csvReader.readNext();
            Throw.when(header.length != columns.size(), IOException.class,
                    "Number of columns in the data file does not match column metadata size");
            for (int i = 0; i < header.length; i++)
            {
                Throw.when(!header[i].equals(columns.get(i).getId()), IOException.class,
                        "Header for column %d in the data file does not match column metadata info", i);
            }

            // Read the data file records
            String[] data = csvReader.readNext();
            while (data != null)
            {
                Object[] values = new Object[columns.size()];
                for (int i = 0; i < values.length; i++)
                {
                    values[i] = serializers[i].deserialize(data[i]);
                }
                dataTable.addRecord(values);
                data = csvReader.readNext();
            }
            return dataTable;
        }
        finally
        {
            if (null != csvMetaReader)
            {
                csvMetaReader.close();
            }
            if (null != csvReader)
            {
                csvReader.close();
            }
        }
    }

    /**
     * Read the data from the CSV-file into the data table. Use the metadata to reconstruct the data table.
     * @param reader Reader; the reader that can read the data, e.g. from a file
     * @param metaReader Reader; the writer for the metadata
     * @return dataTable the data table reconstructed from the meta data and filled with the data
     * @throws IOException on I/O error when reading the data
     * @throws CsvValidationException when the CSV data was not formatted right
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static DataTable readData(final Reader reader, final Reader metaReader)
            throws IOException, CsvValidationException, TextSerializationException
    {
        return readData(reader, metaReader, ICSVWriter.DEFAULT_SEPARATOR, ICSVWriter.DEFAULT_QUOTE_CHARACTER, '\\',
                ICSVWriter.DEFAULT_LINE_END);
    }

    /**
     * Read the data from the CSV-file into the data table. Use the metadata to reconstruct the data table.
     * @param filename String; the file name to read the data from
     * @param metaFilename String; the file name to read the metadata from
     * @return dataTable the data table reconstructed from the meta data and filled with the data
     * @throws IOException on I/O error when reading the data
     * @throws CsvValidationException when the CSV data was not formatted right
     * @throws TextSerializationException on unknown data type for serialization
     */
    public static DataTable readData(final String filename, final String metaFilename)
            throws IOException, CsvValidationException, TextSerializationException
    {
        FileReader fr = null;
        FileReader mfr = null;
        try
        {
            fr = new FileReader(filename);
            mfr = new FileReader(metaFilename);
            return readData(fr, mfr);
        }
        finally
        {
            if (null != fr)
            {
                fr.close(); // May have already been closed when the CSV reader was closed, but multiple close is harmless
            }
            if (null != mfr)
            {
                mfr.close();
            }
        }
    }

}