/*
 * Copyright 2010 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.aztec.detector;

import com.google.zxing.NotFoundException;
import com.google.zxing.ResultPoint;
import com.google.zxing.aztec.AztecDetectorResult;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.GridSampler;
import com.google.zxing.common.detector.MathUtils;
import com.google.zxing.common.detector.WhiteRectangleDetector;
import com.google.zxing.common.reedsolomon.GenericGF;
import com.google.zxing.common.reedsolomon.ReedSolomonDecoder;
import com.google.zxing.common.reedsolomon.ReedSolomonException;

/**
 * Encapsulates logic that can detect an Aztec Code in an image, even if the Aztec Code
 * is rotated or skewed, or partially obscured.
 *
 * @author David Olivier
 * @author Frank Yellin
 */
public final class Detector {

    private static final int[] EXPECTED_CORNER_BITS = {
            0xee0,  // 07340  XXX .XX X.. ...
            0x1dc,  // 00734  ... XXX .XX X..
            0x83b,  // 04073  X.. ... XXX .XX
            0x707,  // 03407 .XX X.. ... XXX
    };
    private final BitMatrix image;
    private boolean compact;
    private int nbLayers;
    private int nbDataBlocks;
    private int nbCenterLayers;
    private int shift;

    public Detector(BitMatrix image) {
        this.image = image;
    }

    private static int getRotation(int[] sides, int length) throws NotFoundException {
        // In a normal pattern, we expect to See
        //   **    .*             D       A
        //   *      *
        //
        //   .      *
        //   ..    ..             C       B
        //
        // Grab the 3 bits from each of the sides the form the locator pattern and concatenate
        // into a 12-bit integer.  Start with the bit at A
        int cornerBits = 0;
        for (int side : sides) {
            // XX......X where X's are orientation marks
            int t = ((side >> (length - 2)) << 1) + (side & 1);
            cornerBits = (cornerBits << 3) + t;
        }
        // Mov the bottom bit to the top, so that the three bits of the locator pattern at A are
        // together.  cornerBits is now:
        //  3 orientation bits at A || 3 orientation bits at B || ... || 3 orientation bits at D
        cornerBits = ((cornerBits & 1) << 11) + (cornerBits >> 1);
        // The result shift indicates which element of BullsEyeCorners[] goes into the top-left
        // corner. Since the four rotation values have a Hamming distance of 8, we
        // can easily tolerate two errors.
        for (int shift = 0; shift < 4; shift++) {
            if (Integer.bitCount(cornerBits ^ EXPECTED_CORNER_BITS[shift]) <= 2) {
                return shift;
            }
        }
        throw NotFoundException.getNotFoundInstance();
    }

    /**
     * Corrects the parameter bits using Reed-Solomon algorithm.
     *
     * @param parameterData parameter bits
     * @param compact       true if this is a compact Aztec code
     * @throws NotFoundException if the array contains too many errors
     */
    private static int getCorrectedParameterData(long parameterData, boolean compact) throws NotFoundException {
        int numCodewords;
        int numDataCodewords;

        if (compact) {
            numCodewords = 7;
            numDataCodewords = 2;
        } else {
            numCodewords = 10;
            numDataCodewords = 4;
        }

        int numECCodewords = numCodewords - numDataCodewords;
        int[] parameterWords = new int[numCodewords];
        for (int i = numCodewords - 1; i >= 0; --i) {
            parameterWords[i] = (int) parameterData & 0xF;
            parameterData >>= 4;
        }
        try {
            ReedSolomonDecoder rsDecoder = new ReedSolomonDecoder(GenericGF.AZTEC_PARAM);
            rsDecoder.decode(parameterWords, numECCodewords);
        } catch (ReedSolomonException ignored) {
            throw NotFoundException.getNotFoundInstance();
        }
        // Toss the error correction.  Just return the data as an integer
        int result = 0;
        for (int i = 0; i < numDataCodewords; i++) {
            result = (result << 4) + parameterWords[i];
        }
        return result;
    }

    /**
     * Expand the square represented by the corner points by pushing out equally in all directions
     *
     * @param cornerPoints the corners of the square, which has the bull's eye at its center
     * @param oldSide      the original length of the side of the square in the target bit matrix
     * @param newSide      the new length of the size of the square in the target bit matrix
     * @return the corners of the expanded square
     */
    private static ResultPoint[] expandSquare(ResultPoint[] cornerPoints, float oldSide, float newSide) {
        float ratio = newSide / (2 * oldSide);
        float dx = cornerPoints[0].getX() - cornerPoints[2].getX();
        float dy = cornerPoints[0].getY() - cornerPoints[2].getY();
        float centerx = (cornerPoints[0].getX() + cornerPoints[2].getX()) / 2.0f;
        float centery = (cornerPoints[0].getY() + cornerPoints[2].getY()) / 2.0f;

        ResultPoint result0 = new ResultPoint(centerx + ratio * dx, centery + ratio * dy);
        ResultPoint result2 = new ResultPoint(centerx - ratio * dx, centery - ratio * dy);

        dx = cornerPoints[1].getX() - cornerPoints[3].getX();
        dy = cornerPoints[1].getY() - cornerPoints[3].getY();
        centerx = (cornerPoints[1].getX() + cornerPoints[3].getX()) / 2.0f;
        centery = (cornerPoints[1].getY() + cornerPoints[3].getY()) / 2.0f;
        ResultPoint result1 = new ResultPoint(centerx + ratio * dx, centery + ratio * dy);
        ResultPoint result3 = new ResultPoint(centerx - ratio * dx, centery - ratio * dy);

        return new ResultPoint[]{result0, result1, result2, result3};
    }

    private static float distance(Point a, Point b) {
        return MathUtils.distance(a.getX(), a.getY(), b.getX(), b.getY());
    }

    private static float distance(ResultPoint a, ResultPoint b) {
        return MathUtils.distance(a.getX(), a.getY(), b.getX(), b.getY());
    }

    public AztecDetectorResult detect() throws NotFoundException {
        return detect(false);
    }

    /**
     * Detects an Aztec Code in an image.
     *
     * @param isMirror if true, image is a mirror-image of original
     * @return {@link AztecDetectorResult} encapsulating results of detecting an Aztec Code
     * @throws NotFoundException if no Aztec Code can be found
     */
    public AztecDetectorResult detect(boolean isMirror) throws NotFoundException {

        // 1. Get the center of the aztec matrix
        Point pCenter = getMatrixCenter();

        // 2. Get the center points of the four diagonal points just outside the bull's eye
        //  [topRight, bottomRight, bottomLeft, topLeft]
        ResultPoint[] bullsEyeCorners = getBullsEyeCorners(pCenter);

        if (isMirror) {
            ResultPoint temp = bullsEyeCorners[0];
            bullsEyeCorners[0] = bullsEyeCorners[2];
            bullsEyeCorners[2] = temp;
        }

        // 3. Get the size of the matrix and other parameters from the bull's eye
        extractParameters(bullsEyeCorners);

        // 4. Sample the grid
        BitMatrix bits = sampleGrid(image,
                bullsEyeCorners[shift % 4],
                bullsEyeCorners[(shift + 1) % 4],
                bullsEyeCorners[(shift + 2) % 4],
                bullsEyeCorners[(shift + 3) % 4]);

        // 5. Get the corners of the matrix.
        ResultPoint[] corners = getMatrixCornerPoints(bullsEyeCorners);

        return new AztecDetectorResult(bits, corners, compact, nbDataBlocks, nbLayers);
    }

    /**
     * Extracts the number of data layers and data blocks from the layer around the bull's eye.
     *
     * @param bullsEyeCorners the array of bull's eye corners
     * @throws NotFoundException in case of too many errors or invalid parameters
     */
    private void extractParameters(ResultPoint[] bullsEyeCorners) throws NotFoundException {
        if (!isValid(bullsEyeCorners[0]) || !isValid(bullsEyeCorners[1]) ||
                !isValid(bullsEyeCorners[2]) || !isValid(bullsEyeCorners[3])) {
            throw NotFoundException.getNotFoundInstance();
        }
        int length = 2 * nbCenterLayers;
        // Get the bits around the bull's eye
        int[] sides = {
                sampleLine(bullsEyeCorners[0], bullsEyeCorners[1], length), // Right side
                sampleLine(bullsEyeCorners[1], bullsEyeCorners[2], length), // Bottom
                sampleLine(bullsEyeCorners[2], bullsEyeCorners[3], length), // Left side
                sampleLine(bullsEyeCorners[3], bullsEyeCorners[0], length)  // Top
        };

        // bullsEyeCorners[shift] is the corner of the bulls'eye that has three
        // orientation marks.
        // sides[shift] is the row/column that goes from the corner with three
        // orientation marks to the corner with two.
        shift = getRotation(sides, length);

        // Flatten the parameter bits into a single 28- or 40-bit long
        long parameterData = 0;
        for (int i = 0; i < 4; i++) {
            int side = sides[(shift + i) % 4];
            if (compact) {
                // Each side of the form ..XXXXXXX. where Xs are parameter data
                parameterData <<= 7;
                parameterData += (side >> 1) & 0x7F;
            } else {
                // Each side of the form ..XXXXX.XXXXX. where Xs are parameter data
                parameterData <<= 10;
                parameterData += ((side >> 2) & (0x1f << 5)) + ((side >> 1) & 0x1F);
            }
        }

        // Corrects parameter data using RS.  Returns just the data portion
        // without the error correction.
        int correctedData = getCorrectedParameterData(parameterData, compact);

        if (compact) {
            // 8 bits:  2 bits layers and 6 bits data blocks
            nbLayers = (correctedData >> 6) + 1;
            nbDataBlocks = (correctedData & 0x3F) + 1;
        } else {
            // 16 bits:  5 bits layers and 11 bits data blocks
            nbLayers = (correctedData >> 11) + 1;
            nbDataBlocks = (correctedData & 0x7FF) + 1;
        }
    }

    /**
     * Finds the corners of a bull-eye centered on the passed point.
     * This returns the centers of the diagonal points just outside the bull's eye
     * Returns [topRight, bottomRight, bottomLeft, topLeft]
     *
     * @param pCenter Center point
     * @return The corners of the bull-eye
     * @throws NotFoundException If no valid bull-eye can be found
     */
    private ResultPoint[] getBullsEyeCorners(Point pCenter) throws NotFoundException {

        Point pina = pCenter;
        Point pinb = pCenter;
        Point pinc = pCenter;
        Point pind = pCenter;

        boolean color = true;

        for (nbCenterLayers = 1; nbCenterLayers < 9; nbCenterLayers++) {
            Point pouta = getFirstDifferent(pina, color, 1, -1);
            Point poutb = getFirstDifferent(pinb, color, 1, 1);
            Point poutc = getFirstDifferent(pinc, color, -1, 1);
            Point poutd = getFirstDifferent(pind, color, -1, -1);

            //d      a
            //
            //c      b

            if (nbCenterLayers > 2) {
                float q = distance(poutd, pouta) * nbCenterLayers / (distance(pind, pina) * (nbCenterLayers + 2));
                if (q < 0.75 || q > 1.25 || !isWhiteOrBlackRectangle(pouta, poutb, poutc, poutd)) {
                    break;
                }
            }

            pina = pouta;
            pinb = poutb;
            pinc = poutc;
            pind = poutd;

            color = !color;
        }

        if (nbCenterLayers != 5 && nbCenterLayers != 7) {
            throw NotFoundException.getNotFoundInstance();
        }

        compact = nbCenterLayers == 5;

        // Expand the square by .5 pixel in each direction so that we're on the border
        // between the white square and the black square
        ResultPoint pinax = new ResultPoint(pina.getX() + 0.5f, pina.getY() - 0.5f);
        ResultPoint pinbx = new ResultPoint(pinb.getX() + 0.5f, pinb.getY() + 0.5f);
        ResultPoint pincx = new ResultPoint(pinc.getX() - 0.5f, pinc.getY() + 0.5f);
        ResultPoint pindx = new ResultPoint(pind.getX() - 0.5f, pind.getY() - 0.5f);

        // Expand the square so that its corners are the centers of the points
        // just outside the bull's eye.
        return expandSquare(new ResultPoint[]{pinax, pinbx, pincx, pindx},
                2 * nbCenterLayers - 3,
                2 * nbCenterLayers);
    }

    /**
     * Finds a candidate center point of an Aztec code from an image
     *
     * @return the center point
     */
    private Point getMatrixCenter() {

        ResultPoint pointA;
        ResultPoint pointB;
        ResultPoint pointC;
        ResultPoint pointD;

        //Get a white rectangle that can be the border of the matrix in center bull's eye or
        try {

            ResultPoint[] cornerPoints = new WhiteRectangleDetector(image).detect();
            pointA = cornerPoints[0];
            pointB = cornerPoints[1];
            pointC = cornerPoints[2];
            pointD = cornerPoints[3];

        } catch (NotFoundException e) {

            // This exception can be in case the initial rectangle is white
            // In that case, surely in the bull's eye, we try to expand the rectangle.
            int cx = image.getWidth() / 2;
            int cy = image.getHeight() / 2;
            pointA = getFirstDifferent(new Point(cx + 7, cy - 7), false, 1, -1).toResultPoint();
            pointB = getFirstDifferent(new Point(cx + 7, cy + 7), false, 1, 1).toResultPoint();
            pointC = getFirstDifferent(new Point(cx - 7, cy + 7), false, -1, 1).toResultPoint();
            pointD = getFirstDifferent(new Point(cx - 7, cy - 7), false, -1, -1).toResultPoint();

        }

        //Compute the center of the rectangle
        int cx = MathUtils.round((pointA.getX() + pointD.getX() + pointB.getX() + pointC.getX()) / 4.0f);
        int cy = MathUtils.round((pointA.getY() + pointD.getY() + pointB.getY() + pointC.getY()) / 4.0f);

        // Redetermine the white rectangle starting from previously computed center.
        // This will ensure that we end up with a white rectangle in center bull's eye
        // in order to compute a more accurate center.
        try {
            ResultPoint[] cornerPoints = new WhiteRectangleDetector(image, 15, cx, cy).detect();
            pointA = cornerPoints[0];
            pointB = cornerPoints[1];
            pointC = cornerPoints[2];
            pointD = cornerPoints[3];
        } catch (NotFoundException e) {
            // This exception can be in case the initial rectangle is white
            // In that case we try to expand the rectangle.
            pointA = getFirstDifferent(new Point(cx + 7, cy - 7), false, 1, -1).toResultPoint();
            pointB = getFirstDifferent(new Point(cx + 7, cy + 7), false, 1, 1).toResultPoint();
            pointC = getFirstDifferent(new Point(cx - 7, cy + 7), false, -1, 1).toResultPoint();
            pointD = getFirstDifferent(new Point(cx - 7, cy - 7), false, -1, -1).toResultPoint();
        }

        // Recompute the center of the rectangle
        cx = MathUtils.round((pointA.getX() + pointD.getX() + pointB.getX() + pointC.getX()) / 4.0f);
        cy = MathUtils.round((pointA.getY() + pointD.getY() + pointB.getY() + pointC.getY()) / 4.0f);

        return new Point(cx, cy);
    }

    /**
     * Gets the Aztec code corners from the bull's eye corners and the parameters.
     *
     * @param bullsEyeCorners the array of bull's eye corners
     * @return the array of aztec code corners
     */
    private ResultPoint[] getMatrixCornerPoints(ResultPoint[] bullsEyeCorners) {
        return expandSquare(bullsEyeCorners, 2 * nbCenterLayers, getDimension());
    }

    /**
     * Creates a BitMatrix by sampling the provided image.
     * topLeft, topRight, bottomRight, and bottomLeft are the centers of the squares on the
     * diagonal just outside the bull's eye.
     */
    private BitMatrix sampleGrid(BitMatrix image,
                                 ResultPoint topLeft,
                                 ResultPoint topRight,
                                 ResultPoint bottomRight,
                                 ResultPoint bottomLeft) throws NotFoundException {

        GridSampler sampler = GridSampler.getInstance();
        int dimension = getDimension();

        float low = dimension / 2.0f - nbCenterLayers;
        float high = dimension / 2.0f + nbCenterLayers;

        return sampler.sampleGrid(image,
                dimension,
                dimension,
                low, low,   // topleft
                high, low,  // topright
                high, high, // bottomright
                low, high,  // bottomleft
                topLeft.getX(), topLeft.getY(),
                topRight.getX(), topRight.getY(),
                bottomRight.getX(), bottomRight.getY(),
                bottomLeft.getX(), bottomLeft.getY());
    }

    /**
     * Samples a line.
     *
     * @param p1   start point (inclusive)
     * @param p2   end point (exclusive)
     * @param size number of bits
     * @return the array of bits as an int (first bit is high-order bit of result)
     */
    private int sampleLine(ResultPoint p1, ResultPoint p2, int size) {
        int result = 0;

        float d = distance(p1, p2);
        float moduleSize = d / size;
        float px = p1.getX();
        float py = p1.getY();
        float dx = moduleSize * (p2.getX() - p1.getX()) / d;
        float dy = moduleSize * (p2.getY() - p1.getY()) / d;
        for (int i = 0; i < size; i++) {
            if (image.get(MathUtils.round(px + i * dx), MathUtils.round(py + i * dy))) {
                result |= 1 << (size - i - 1);
            }
        }
        return result;
    }

    /**
     * @return true if the border of the rectangle passed in parameter is compound of white points only
     * or black points only
     */
    private boolean isWhiteOrBlackRectangle(Point p1,
                                            Point p2,
                                            Point p3,
                                            Point p4) {

        int corr = 3;

        p1 = new Point(p1.getX() - corr, p1.getY() + corr);
        p2 = new Point(p2.getX() - corr, p2.getY() - corr);
        p3 = new Point(p3.getX() + corr, p3.getY() - corr);
        p4 = new Point(p4.getX() + corr, p4.getY() + corr);

        int cInit = getColor(p4, p1);

        if (cInit == 0) {
            return false;
        }

        int c = getColor(p1, p2);

        if (c != cInit) {
            return false;
        }

        c = getColor(p2, p3);

        if (c != cInit) {
            return false;
        }

        c = getColor(p3, p4);

        return c == cInit;

    }

    /**
     * Gets the color of a segment
     *
     * @return 1 if segment more than 90% black, -1 if segment is more than 90% white, 0 else
     */
    private int getColor(Point p1, Point p2) {
        float d = distance(p1, p2);
        float dx = (p2.getX() - p1.getX()) / d;
        float dy = (p2.getY() - p1.getY()) / d;
        int error = 0;

        float px = p1.getX();
        float py = p1.getY();

        boolean colorModel = image.get(p1.getX(), p1.getY());

        for (int i = 0; i < d; i++) {
            px += dx;
            py += dy;
            if (image.get(MathUtils.round(px), MathUtils.round(py)) != colorModel) {
                error++;
            }
        }

        float errRatio = error / d;

        if (errRatio > 0.1f && errRatio < 0.9f) {
            return 0;
        }

        return (errRatio <= 0.1f) == colorModel ? 1 : -1;
    }

    /**
     * Gets the coordinate of the first point with a different color in the given direction
     */
    private Point getFirstDifferent(Point init, boolean color, int dx, int dy) {
        int x = init.getX() + dx;
        int y = init.getY() + dy;

        while (isValid(x, y) && image.get(x, y) == color) {
            x += dx;
            y += dy;
        }

        x -= dx;
        y -= dy;

        while (isValid(x, y) && image.get(x, y) == color) {
            x += dx;
        }
        x -= dx;

        while (isValid(x, y) && image.get(x, y) == color) {
            y += dy;
        }
        y -= dy;

        return new Point(x, y);
    }

    private boolean isValid(int x, int y) {
        return x >= 0 && x < image.getWidth() && y > 0 && y < image.getHeight();
    }

    private boolean isValid(ResultPoint point) {
        int x = MathUtils.round(point.getX());
        int y = MathUtils.round(point.getY());
        return isValid(x, y);
    }

    private int getDimension() {
        if (compact) {
            return 4 * nbLayers + 11;
        }
        if (nbLayers <= 4) {
            return 4 * nbLayers + 15;
        }
        return 4 * nbLayers + 2 * ((nbLayers - 4) / 8 + 1) + 15;
    }

    static final class Point {
        private final int x;
        private final int y;

        Point(int x, int y) {
            this.x = x;
            this.y = y;
        }

        ResultPoint toResultPoint() {
            return new ResultPoint(getX(), getY());
        }

        int getX() {
            return x;
        }

        int getY() {
            return y;
        }

        @Override
        public String toString() {
            return "<" + x + ' ' + y + '>';
        }
    }
}
