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

package org.httprpc.io;

import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * CSV decoder.
 */
@SuppressWarnings("unchecked")
public class CSVDecoder extends Decoder>> {
    private char delimiter;

    /**
     * Constructs a new CSV decoder.
     */
    public CSVDecoder() {
        this(',');
    }

    /**
     * Constructs a new CSV decoder.
     *
     * @param delimiter
     * The character to use as a field delimiter.
     */
    public CSVDecoder(char delimiter) {
        super(StandardCharsets.ISO_8859_1);

        this.delimiter = delimiter;
    }

    @Override
    public List> read(Reader reader) throws IOException {
        if (reader == null) {
            throw new IllegalArgumentException();
        }

        reader = new BufferedReader(reader);

        List keys = readValues(reader);

        if (keys.isEmpty()) {
            throw new IOException("Missing header row.");
        }

        List> rows = new ArrayList<>();

        List values = readValues(reader);

        while (!values.isEmpty()) {
            Map row = new LinkedHashMap<>();

            for (int i = 0, n = Math.min(keys.size(), values.size()); i < n; i++) {
                String key = keys.get(i);

                if (key.isEmpty()) {
                    continue;
                }

                String value = values.get(i);

                if (value.isEmpty()) {
                    continue;
                }

                row.put(key, value);
            }

            rows.add(row);

            values = readValues(reader);
        }

        return rows;
    }

    private List readValues(Reader reader) throws IOException {
        List values = new LinkedList<>();

        StringBuilder valueBuilder = new StringBuilder();

        int c = reader.read();

        while (c != '\r' && c != '\n' && c != EOF) {
            valueBuilder.setLength(0);

            boolean quoted = false;

            if (c == '"') {
                quoted = true;

                c = reader.read();
            }

            while ((quoted || (c != delimiter && c != '\r' && c != '\n')) && c != EOF) {
                valueBuilder.append((char)c);

                c = reader.read();

                if (c == '"') {
                    c = reader.read();

                    if (c != '"') {
                        quoted = false;
                    }
                }
            }

            if (quoted) {
                throw new IOException("Unterminated quoted value.");
            }

            values.add(valueBuilder.toString());

            if (c == delimiter) {
                c = reader.read();
            }
        }

        if (c == '\r') {
            c = reader.read();

            if (c != '\n') {
                throw new IOException("Improperly terminated record.");
            }
        }

        return values;
    }
}