/*
 * Copyright 2008 ZXing authors
 *
 * 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 com.google.zxing.oned;

import com.google.zxing.BinaryBitmap;
import com.google.zxing.ChecksumException;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Reader;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
import com.google.zxing.ResultMetadataType;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitArray;

import java.util.Arrays;
import java.util.EnumMap;
import java.util.Map;

/**
 * Encapsulates functionality and implementation that is common to all families
 * of one-dimensional barcodes.
 *
 * @author dswitkin@google.com (Daniel Switkin)
 * @author Sean Owen
 */
public abstract class OneDReader implements Reader {

    protected static final int INTEGER_MATH_SHIFT = 8;
    protected static final int PATTERN_MATCH_RESULT_SCALE_FACTOR = 1 << INTEGER_MATH_SHIFT;

    @Override
    public Result decode(BinaryBitmap image) throws NotFoundException, FormatException {
        return decode(image, null);
    }

    // Note that we don't try rotation without the try harder flag, even if rotation was supported.
    @Override
    public Result decode(BinaryBitmap image,
                         Map<DecodeHintType, ?> hints) throws NotFoundException, FormatException {
        try {
            return doDecode(image, hints);
        } catch (NotFoundException nfe) {
            boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
            if (tryHarder && image.isRotateSupported()) {
                BinaryBitmap rotatedImage = image.rotateCounterClockwise();
                Result result = doDecode(rotatedImage, hints);
                // Record that we found it rotated 90 degrees CCW / 270 degrees CW
                Map<ResultMetadataType, ?> metadata = result.getResultMetadata();
                int orientation = 270;
                if (metadata != null && metadata.containsKey(ResultMetadataType.ORIENTATION)) {
                    // But if we found it reversed in doDecode(), add in that result here:
                    orientation = (orientation +
                            (Integer) metadata.get(ResultMetadataType.ORIENTATION)) % 360;
                }
                result.putMetadata(ResultMetadataType.ORIENTATION, orientation);
                // Update result points
                ResultPoint[] points = result.getResultPoints();
                if (points != null) {
                    int height = rotatedImage.getHeight();
                    for (int i = 0; i < points.length; i++) {
                        points[i] = new ResultPoint(height - points[i].getY() - 1, points[i].getX());
                    }
                }
                return result;
            } else {
                throw nfe;
            }
        }
    }

    @Override
    public void reset() {
        // do nothing
    }

    /**
     * We're going to examine rows from the middle outward, searching alternately above and below the
     * middle, and farther out each time. rowStep is the number of rows between each successive
     * attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
     * middle + rowStep, then middle - (2 * rowStep), etc.
     * rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
     * decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
     * image if "trying harder".
     *
     * @param image The image to decode
     * @param hints Any hints that were requested
     * @return The contents of the decoded barcode
     * @throws NotFoundException Any spontaneous errors which occur
     */
    private Result doDecode(BinaryBitmap image,
                            Map<DecodeHintType, ?> hints) throws NotFoundException {
        int width = image.getWidth();
        int height = image.getHeight();
        BitArray row = new BitArray(width);

        int middle = height >> 1;
        boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
        int rowStep = Math.max(1, height >> (tryHarder ? 8 : 5));
        int maxLines;
        if (tryHarder) {
            maxLines = height; // Look at the whole image, not just the center
        } else {
            maxLines = 15; // 15 rows spaced 1/32 apart is roughly the middle half of the image
        }

        for (int x = 0; x < maxLines; x++) {

            // Scanning from the middle out. Determine which row we're looking at next:
            int rowStepsAboveOrBelow = (x + 1) >> 1;
            boolean isAbove = (x & 0x01) == 0; // i.e. is x even?
            int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
            if (rowNumber < 0 || rowNumber >= height) {
                // Oops, if we run off the top or bottom, stop
                break;
            }

            // Estimate black point for this row and load it:
            try {
                row = image.getBlackRow(rowNumber, row);
            } catch (NotFoundException ignored) {
                continue;
            }

            // While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
            // handle decoding upside down barcodes.
            for (int attempt = 0; attempt < 2; attempt++) {
                if (attempt == 1) { // trying again?
                    row.reverse(); // reverse the row and continue
                    // This means we will only ever draw result points *once* in the life of this method
                    // since we want to avoid drawing the wrong points after flipping the row, and,
                    // don't want to clutter with noise from every single row scan -- just the scans
                    // that start on the center line.
                    if (hints != null && hints.containsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK)) {
                        Map<DecodeHintType, Object> newHints = new EnumMap<DecodeHintType, Object>(DecodeHintType.class);
                        newHints.putAll(hints);
                        newHints.remove(DecodeHintType.NEED_RESULT_POINT_CALLBACK);
                        hints = newHints;
                    }
                }
                try {
                    // Look for a barcode
                    Result result = decodeRow(rowNumber, row, hints);
                    // We found our barcode
                    if (attempt == 1) {
                        // But it was upside down, so note that
                        result.putMetadata(ResultMetadataType.ORIENTATION, 180);
                        // And remember to flip the result points horizontally.
                        ResultPoint[] points = result.getResultPoints();
                        if (points != null) {
                            points[0] = new ResultPoint(width - points[0].getX() - 1, points[0].getY());
                            points[1] = new ResultPoint(width - points[1].getX() - 1, points[1].getY());
                        }
                    }
                    return result;
                } catch (ReaderException re) {
                    // continue -- just couldn't decode this row
                }
            }
        }

        throw NotFoundException.getNotFoundInstance();
    }

    /**
     * Records the size of successive runs of white and black pixels in a row, starting at a given point.
     * The values are recorded in the given array, and the number of runs recorded is equal to the size
     * of the array. If the row starts on a white pixel at the given start point, then the first count
     * recorded is the run of white pixels starting from that point; likewise it is the count of a run
     * of black pixels if the row begin on a black pixels at that point.
     *
     * @param row      row to count from
     * @param start    offset into row to start at
     * @param counters array into which to record counts
     * @throws NotFoundException if counters cannot be filled entirely from row before running out
     *                           of pixels
     */
    protected static void recordPattern(BitArray row,
                                        int start,
                                        int[] counters) throws NotFoundException {
        int numCounters = counters.length;
        Arrays.fill(counters, 0, numCounters, 0);
        int end = row.getSize();
        if (start >= end) {
            throw NotFoundException.getNotFoundInstance();
        }
        boolean isWhite = !row.get(start);
        int counterPosition = 0;
        int i = start;
        while (i < end) {
            if (row.get(i) ^ isWhite) { // that is, exactly one is true
                counters[counterPosition]++;
            } else {
                counterPosition++;
                if (counterPosition == numCounters) {
                    break;
                } else {
                    counters[counterPosition] = 1;
                    isWhite = !isWhite;
                }
            }
            i++;
        }
        // If we read fully the last section of pixels and filled up our counters -- or filled
        // the last counter but ran off the side of the image, OK. Otherwise, a problem.
        if (!(counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end))) {
            throw NotFoundException.getNotFoundInstance();
        }
    }

    protected static void recordPatternInReverse(BitArray row, int start, int[] counters)
            throws NotFoundException {
        // This could be more efficient I guess
        int numTransitionsLeft = counters.length;
        boolean last = row.get(start);
        while (start > 0 && numTransitionsLeft >= 0) {
            if (row.get(--start) != last) {
                numTransitionsLeft--;
                last = !last;
            }
        }
        if (numTransitionsLeft >= 0) {
            throw NotFoundException.getNotFoundInstance();
        }
        recordPattern(row, start + 1, counters);
    }

    /**
     * Determines how closely a set of observed counts of runs of black/white values matches a given
     * target pattern. This is reported as the ratio of the total variance from the expected pattern
     * proportions across all pattern elements, to the length of the pattern.
     *
     * @param counters              observed counters
     * @param pattern               expected pattern
     * @param maxIndividualVariance The most any counter can differ before we give up
     * @return ratio of total variance between counters and pattern compared to total pattern size,
     * where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means
     * the total variance between counters and patterns equals the pattern length, higher values mean
     * even more variance
     */
    protected static int patternMatchVariance(int[] counters,
                                              int[] pattern,
                                              int maxIndividualVariance) {
        int numCounters = counters.length;
        int total = 0;
        int patternLength = 0;
        for (int i = 0; i < numCounters; i++) {
            total += counters[i];
            patternLength += pattern[i];
        }
        if (total < patternLength) {
            // If we don't even have one pixel per unit of bar width, assume this is too small
            // to reliably match, so fail:
            return Integer.MAX_VALUE;
        }
        // We're going to fake floating-point math in integers. We just need to use more bits.
        // Scale up patternLength so that intermediate values below like scaledCounter will have
        // more "significant digits"
        int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
        maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;

        int totalVariance = 0;
        for (int x = 0; x < numCounters; x++) {
            int counter = counters[x] << INTEGER_MATH_SHIFT;
            int scaledPattern = pattern[x] * unitBarWidth;
            int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
            if (variance > maxIndividualVariance) {
                return Integer.MAX_VALUE;
            }
            totalVariance += variance;
        }
        return totalVariance / total;
    }

    /**
     * <p>Attempts to decode a one-dimensional barcode format given a single row of
     * an image.</p>
     *
     * @param rowNumber row number from top of the row
     * @param row       the black/white pixel data of the row
     * @param hints     decode hints
     * @return {@link Result} containing encoded string and start/end of barcode
     * @throws NotFoundException if an error occurs or barcode cannot be found
     */
    public abstract Result decodeRow(int rowNumber, BitArray row, Map<DecodeHintType, ?> hints)
            throws NotFoundException, ChecksumException, FormatException;

}
