com.brettonw.bedrock.bag.entry.HandlerArrayFromFixed Maven / Gradle / Ivy

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Bag provides two container classes for text-based storage of constrained types in an array (BagArray) or as a map (BagObject), with a means of serializing objects to and from these container types.
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package com.brettonw.bedrock.bag.entry;

import com.brettonw.bedrock.bag.BagArray;

import java.util.ArrayDeque;
import java.util.Queue;

public class HandlerArrayFromFixed extends HandlerComposite {
    private final int[][] fields;
    private final int fieldCount;
    private int totalWidth;

    public HandlerArrayFromFixed (int[][] fields) {
        this (fields, HandlerValue.HANDLER_VALUE);
    }

    /**
     *
     * @param fields an array of field descriptions, where each field description is a 2 element
     *               array (start and end - not inclusive)
     * @param handler
     */
    public HandlerArrayFromFixed (int[][] fields, Handler handler) {
        super (handler);
        this.fields = fields;
        fieldCount = fields.length;
        totalWidth = 0;
        for (var field : fields) {
            totalWidth += field[1];
        }
    }

    /**
     * this method returns a field description array given a set of positions (assuming there are no
     * pads in the intended string)
     * @param offset The relative offset of the beginning of the line compared to the
     *              offsets in 'positions'. I find it easier to use my text editor to
     *              identify positions, and it counts the first column as '1', so I can
     *              set 'first' = 1, and then use the column number of the rest of the
     *              fields as reported by my text editor.
     * @param positions An array of numbers indicating positions of fields in the data lines,
     *                  starting at the first field.
     * @return a two dimensional array of start and end positions for tokens
     */
    public static int[][] fieldsFromPositions (int offset, int... positions) {
        var fieldCount = positions.length - 1;
        var fields = new int[fieldCount][2];
        var last = positions[0] - offset;
        for (int i = 0; i < fieldCount; ++i) {
            fields[i][0] = last;
            last = positions[i + 1] - offset;
            fields[i][1] = last;
        }
        return fields;
    }

    /**
     * this method returns a field description array given a set of widths (assuming there are no
     * pads in the intended string)
     * @param widths an array of numbers indicating the width of each field
     * @return a two dimensional array of start and end positions for tokens
     */
    public static int[][] fieldsFromWidths (int... widths) {
        var fields = new int[widths.length][2];
        var start = 0;
        for (int i = 0; i < widths.length; ++i) {
            fields[i][0] = start;
            start = (fields[i][1] = start + widths[i]);
        }
        return fields;
    }

    /**
     *
     * @param exemplar a string representing an example record to extract the positions from,
     *                 where positions are identified every time the exemplar value changes
     * @param separator a character that represents an ignored region of the data line
     * @return a two dimensional array of start and end positions for tokens
     */
    public static int[][] fieldsFromExemplar (String exemplar, char separator) {
        // walk the line to figure the positions
        var queue = new ArrayDeque ();
        var lastChar = separator;
        for (int i = 0, end = exemplar.length (); i < end; ++i) {
            var nextChar = exemplar.charAt (i);
            if (nextChar != lastChar) {
                // emit this position
                if (lastChar == separator) {
                    // emit this position as a start
                    queue.add (i);
                } else {
                    // emit this position as an end
                    queue.add (i);

                    // emit a start if the next character is not a separator
                    if (nextChar != separator) {
                        // emit this position as a start
                        queue.add (i);
                    }
                }
                lastChar = nextChar;
            }
        }
        if (lastChar != separator) {
            // emit this position as an end
            queue.add (exemplar.length ());
        }

        // convert the positions list into a fields description, we take them two at a time
        if ((queue.size () & 0x01) == 0) {
            var fieldCount = queue.size () / 2;
            var fields = new int[fieldCount][2];
            for (int i = 0; i < fieldCount; ++i) {
                fields[i][0] = queue.remove (); // position
                fields[i][1] = queue.remove (); // end
            }
            return fields;
        }
        return null;
    }

    @Override
    public Object getEntry (String input) {
        // create the array
        var bagArray = new BagArray (fieldCount);

        // ignore empty lines
        if (input.length () > 0) {
            // pad the input with spaces to match the expected width
            input = String.format ("%1$-" + totalWidth + "s", input);

            // split the input up into all the little substrings...
            for (var field : fields) {
                var entryString = input.substring (field[0], field[1]).trim ();
                var entry = handler.getEntry (entryString);
                if (entry != null) {
                    bagArray.add (entry);
                }
            }
        }

        // return the populated array
        return (bagArray.getCount () > 0) ? bagArray : null;
    }
}