CsvParser.apxc

public class CsvParser {
    String csv;
    Integer rowCount;
    Integer cellCount;
    final static String END_LINE = '\r';
    final static String END_CELL = ',';
    final static String ESCAPE_CHAR = '"';
    final static String SPACE = ' ';
    
    public CsvParser(String csvString) {
        csv = csvString.replace('\r\n','\r').replace('\n','\r');
    }
    public List<List<String>> parseWithoutHeaders() {
        List<List<String>> results = new List<List<String>>();
        cellCount = 1;
        rowCount = 0;
        Integer rowSize;
        do {
            String[] line = readLine();
            Integer lineSize = line.size();
            if(lineSize == 0) {
                continue;
            }
            if(rowSize == null) {
                rowSize = lineSize;
            }
            if(rowSize != lineSize) {
                throwInvalidStateError('CSV row has '+lineSize+' cell(s), expected '+rowSize+' cell(s)');
            }
            results.add(line);
            rowCount++;
        } while(csv != '');
        return results;
    }
    public List<List<String>> parseWithHeaders() {
        List<List<String>> results = new List<List<String>>();
        List<String> headers = readLine();
        Set<String> uniqueHeaders = new Set<String>();
        cellCount = 1;
        rowCount = 0;
        for(String header: headers) {
            if(!uniqueHeaders.add(header)) {
                throwInvalidStateError('Duplicate header detected');
            }
        }
        rowCount++;
        Integer headerCellCount = headers.size();
        do {
            String[] line = readLine();
            Integer currentRowCellCount = line.size();
            if(currentRowCellCount == 0) {
                continue;
            }
            if(headerCellCount != currentRowCellCount) {
                cellCount = 0;
                throwInvalidStateError('CSV row has '+currentRowCellCount+' cell(s), expected '+headerCellCount+' cell(s)');
            }
            results.add(line);
            rowCount++;
        } while(csv != '');
        return results;
    }
    List<String> readLine() {
        List<String> results = new List<String>();
        cellCount = 1;
        while(csv != '' && csv.left(1) != END_LINE) {
            results.add(readCell());
            if(csv != '') {
                if(csv.indexOfAny(END_LINE+END_CELL) != 0) {
                    throwInvalidStateError('Unexpected CSV state while reading line');
                }
                if(csv.left(1) == END_CELL) {
                    csv = csv.substring(1);
                }
            }
        }
        csv = csv.substring(1);
        return results;
    }
    String readCell() {
        csv = csv.replaceFirst('^ *','');
        return csv.left(1) == ESCAPE_CHAR? readQuotedCell(): readUnquotedCell();
    }
    String readQuotedCell() {
        String result = '';
        do {
            Integer nextEscape = csv.indexOf(ESCAPE_CHAR,1);
            if(nextEscape == -1) {
                throwInvalidStateError('Quoted cell does not end in a quote');
            }
            result += csv.substringBefore(ESCAPE_CHAR)+ESCAPE_CHAR;
            csv = csv.substringAfter(ESCAPE_CHAR);
        } while(csv != '' && !csv.left(1).containsAny(END_LINE+END_CELL));
        return result.removeStart(ESCAPE_CHAR).removeEnd(ESCAPE_CHAR).replace(ESCAPE_CHAR+ESCAPE_CHAR,ESCAPE_CHAR);
    }
    String readUnquotedCell() {
        Integer nextCellBreak = csv.indexOfAny(END_CELL+END_LINE);
        Integer nextEscape = csv.indexOf(ESCAPE_CHAR);
        String result = csv;
        if(nextCellBreak != -1 && nextEscape != -1 && nextCellBreak > nextEscape) {
            throwInvalidStateError('You cannot include a quoted character in an unquoted cell');
        }
        if(nextCellBreak != -1) {
            result = csv.substring(0, nextCellBreak);
            csv = csv.removeStart(result);
        }
        return result;
    }
    void throwInvalidStateError(String message) {
        throw new InvalidStateException(String.format('{0} @ row {1} cell {2}', new String[] { message, ''+rowCount, ''+cellCount}));
    }
    public class InvalidStateException extends Exception { }
}