/* 
 * QR Code generator library (Java)
 * 
 * Copyright (c) Project Nayuki
 * https://www.nayuki.io/page/qr-code-generator-library
 * 
 * (MIT License)
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

package io.nayuki.qrcodegen;

import android.graphics.Bitmap;
import android.support.annotation.NonNull;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;


/**
 * Represents an immutable square grid of black and white cells for a QR Code symbol, and
 * provides static functions to create a QR Code from user-supplied textual or binary data.
 * <p>This class covers the QR Code model 2 specification, supporting all versions (sizes)
 * from 1 to 40, all 4 error correction levels, and only 3 character encoding modes.</p>
 */
public final class QrCode {

	/*---- Public static factory functions ----*/

    /**
     * Returns a QR Code symbol representing the specified Unicode text string at the specified error correction level.
     * As a conservative upper bound, this function is guaranteed to succeed for strings that have 738 or fewer Unicode
     * code points (not UTF-16 code units). The smallest possible QR Code version is automatically chosen for the output.
     * The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
     *
     * @param text the text to be encoded, which can be any Unicode string
     * @param ecl  the error correction level to use (will be boosted)
     * @return a QR Code representing the text
     * @throws NullPointerException     if the text or error correction level is {@code null}
     * @throws IllegalArgumentException if the text fails to fit in the largest version QR Code, which means it is too long
     */
    public static QrCode encodeText(@NonNull String text, @NonNull Ecc ecl) {
        List<QrSegment> segs = QrSegment.makeSegments(text);
        return encodeSegments(segs, ecl);
    }


    /**
     * Returns a QR Code symbol representing the specified binary data string at the specified error correction level.
     * This function always encodes using the binary segment mode, not any text mode. The maximum number of
     * bytes allowed is 2953. The smallest possible QR Code version is automatically chosen for the output.
     * The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
     *
     * @param data the binary data to encode
     * @param ecl  the error correction level to use (will be boosted)
     * @return a QR Code representing the binary data
     * @throws NullPointerException     if the data or error correction level is {@code null}
     * @throws IllegalArgumentException if the data fails to fit in the largest version QR Code, which means it is too long
     */
    public static QrCode encodeBinary(@NonNull byte[] data, @NonNull Ecc ecl) {
        QrSegment seg = QrSegment.makeBytes(data);
        return encodeSegments(Collections.singletonList(seg), ecl);
    }


    /**
     * Returns a QR Code symbol representing the specified data segments at the specified error correction
     * level or higher. The smallest possible QR Code version is automatically chosen for the output.
     * <p>This function allows the user to create a custom sequence of segments that switches
     * between modes (such as alphanumeric and binary) to encode text more efficiently. This
     * function is considered to be lower level than simply encoding text or binary data.</p>
     *
     * @param segs the segments to encode
     * @param ecl  the error correction level to use (will be boosted)
     * @return a QR Code representing the segments
     * @throws NullPointerException     if the list of segments, a segment, or the error correction level is {@code null}
     * @throws IllegalArgumentException if the data is too long to fit in the largest version QR Code at the ECL
     */
    public static QrCode encodeSegments(List<QrSegment> segs, Ecc ecl) {
        return encodeSegments(segs, ecl, 1, 40, -1, true);
    }


    /**
     * Returns a QR Code symbol representing the specified data segments with the specified encoding parameters.
     * The smallest possible QR Code version within the specified range is automatically chosen for the output.
     * <p>This function allows the user to create a custom sequence of segments that switches
     * between modes (such as alphanumeric and binary) to encode text more efficiently.
     * This function is considered to be lower level than simply encoding text or binary data.</p>
     *
     * @param segs       the segments to encode
     * @param ecl        the error correction level to use (may be boosted)
     * @param minVersion the minimum allowed version of the QR symbol (at least 1)
     * @param maxVersion the maximum allowed version of the QR symbol (at most 40)
     * @param mask       the mask pattern to use, which is either -1 for automatic choice or from 0 to 7 for fixed choice
     * @param boostEcl   increases the error correction level if it can be done without increasing the version number
     * @return a QR Code representing the segments
     * @throws NullPointerException     if the list of segments, a segment, or the error correction level is {@code null}
     * @throws IllegalArgumentException if 1 &le; minVersion &le; maxVersion &le; 40 is violated, or if mask
     *                                  &lt; &minus;1 or mask > 7, or if the data is too long to fit in a QR Code at maxVersion at the ECL
     */
    public static QrCode encodeSegments(@NonNull List<QrSegment> segs, @NonNull Ecc ecl,
            int minVersion, int maxVersion, int mask, boolean boostEcl) {
        if (!(1 <= minVersion && minVersion <= maxVersion && maxVersion <= 40) || mask < -1 || mask > 7)
            throw new IllegalArgumentException("Invalid value");

        // Find the minimal version number to use
        int version, dataUsedBits;
        for (version = minVersion; ; version++) {
            int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;  // Number of data bits available
            dataUsedBits = QrSegment.getTotalBits(segs, version);
            if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits)
                break;  // This version number is found to be suitable
            if (version >= maxVersion)  // All versions in the range could not fit the given data
                throw new IllegalArgumentException("Data too long");
        }
        if (dataUsedBits == -1)
            throw new AssertionError();

        // Increase the error correction level while the data still fits in the current version number
        for (Ecc newEcl : Ecc.values()) {
            if (boostEcl && dataUsedBits <= getNumDataCodewords(version, newEcl) * 8)
                ecl = newEcl;
        }

        // Create the data bit string by concatenating all segments
        int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
        BitBuffer bb = new BitBuffer();
        for (QrSegment seg : segs) {
            bb.appendBits(seg.mode.modeBits, 4);
            bb.appendBits(seg.numChars, seg.mode.numCharCountBits(version));
            bb.appendData(seg);
        }

        // Add terminator and pad up to a byte if applicable
        bb.appendBits(0, Math.min(4, dataCapacityBits - bb.bitLength()));
        bb.appendBits(0, (8 - bb.bitLength() % 8) % 8);

        // Pad with alternate bytes until data capacity is reached
        for (int padByte = 0xEC; bb.bitLength() < dataCapacityBits; padByte ^= 0xEC ^ 0x11)
            bb.appendBits(padByte, 8);
        if (bb.bitLength() % 8 != 0)
            throw new AssertionError();

        // Create the QR Code symbol
        return new QrCode(version, ecl, bb.getBytes(), mask);
    }

	
	
	/*---- Instance fields ----*/

    // Public immutable scalar parameters

    /**
     * This QR Code symbol's version number, which is always between 1 and 40 (inclusive).
     */
    public final int version;

    /**
     * The width and height of this QR Code symbol, measured in modules.
     * Always equal to version &times; 4 + 17, in the range 21 to 177.
     */
    public final int size;

    /**
     * The error correction level used in this QR Code symbol. Never {@code null}.
     */
    public final Ecc errorCorrectionLevel;

    /**
     * The mask pattern used in this QR Code symbol, in the range 0 to 7 (i.e. unsigned 3-bit integer).
     * Note that even if a constructor was called with automatic masking requested
     * (mask = -1), the resulting object will still have a mask value between 0 and 7.
     */
    public final int mask;

    // Private grids of modules/pixels (conceptually immutable)
    private boolean[][] modules;     // The modules of this QR Code symbol (false = white, true = black)
    private boolean[][] isFunction;  // Indicates function modules that are not subjected to masking

	
	
	/*---- Constructors ----*/

    /**
     * Creates a new QR Code symbol with the specified version number, error correction level, binary data array, and mask number.
     * <p>This is a cumbersome low-level constructor that should not be invoked directly by the user.
     * To go one level up, see the {@link #encodeSegments(List, Ecc)} function.</p>
     *
     * @param ver           the version number to use, which must be in the range 1 to 40, inclusive
     * @param ecl           the error correction level to use
     * @param dataCodewords the raw binary user data to encode
     * @param mask          the mask pattern to use, which is either -1 for automatic choice or from 0 to 7 for fixed choice
     * @throws NullPointerException     if the byte array or error correction level is {@code null}
     * @throws IllegalArgumentException if the version or mask value is out of range
     */
    public QrCode(int ver, @NonNull Ecc ecl, @NonNull byte[] dataCodewords, int mask) {
        // Check arguments
        if (ver < 1 || ver > 40 || mask < -1 || mask > 7)
            throw new IllegalArgumentException("Value out of range");

        // Initialize fields
        version = ver;
        size = ver * 4 + 17;
        errorCorrectionLevel = ecl;
        modules = new boolean[size][size];  // Entirely white grid
        isFunction = new boolean[size][size];

        // Draw function patterns, draw all codewords, do masking
        drawFunctionPatterns();
        byte[] allCodewords = appendErrorCorrection(dataCodewords);
        drawCodewords(allCodewords);
        this.mask = handleConstructorMasking(mask);
    }


    /**
     * Creates a new QR Code symbol based on the specified existing object, but with a potentially
     * different mask pattern. The version, error correction level, codewords, etc. of the newly
     * created object are all identical to the argument object; only the mask may differ.
     *
     * @param qr   the existing QR Code to copy and modify
     * @param mask the new mask pattern, 0 to 7 to force a fixed choice or -1 for an automatic choice
     * @throws NullPointerException     if the QR Code is {@code null}
     * @throws IllegalArgumentException if the mask value is out of range
     */
    public QrCode(@NonNull QrCode qr, int mask) {
        // Check arguments
        if (mask < -1 || mask > 7)
            throw new IllegalArgumentException("Mask value out of range");

        // Copy scalar fields
        version = qr.version;
        size = qr.size;
        errorCorrectionLevel = qr.errorCorrectionLevel;

        // Handle grid fields
        isFunction = qr.isFunction;  // Shallow copy because the data is read-only
        modules = qr.modules.clone();  // Deep copy
        for (int i = 0; i < modules.length; i++)
            modules[i] = modules[i].clone();

        // Handle masking
        applyMask(qr.mask);  // Undo old mask
        this.mask = handleConstructorMasking(mask);
    }
	
	
	
	/*---- Public instance methods ----*/

    /**
     * Returns the color of the module (pixel) at the specified coordinates, which is either 0 for white or 1 for black. The top
     * left corner has the coordinates (x=0, y=0). If the specified coordinates are out of bounds, then 0 (white) is returned.
     *
     * @param x the x coordinate, where 0 is the left edge and size&minus;1 is the right edge
     * @param y the y coordinate, where 0 is the top edge and size&minus;1 is the bottom edge
     * @return the module's color, which is either 0 (white) or 1 (black)
     */
    public int getModule(int x, int y) {
        if (0 <= x && x < size && 0 <= y && y < size)
            return modules[y][x] ? 1 : 0;
        else
            return 0;  // Infinite white border
    }

    /**
     * Returns a new image object representing this QR Code, with the specified module scale and number
     * of border modules. For example, the arguments scale=10, border=4 means to pad the QR Code symbol
     * with 4 white border modules on all four edges, then use 10*10 pixels to represent each module.
     * The resulting image only contains the hex colors 000000 and FFFFFF.
     *
     * @param scale  the module scale factor, which must be positive
     * @param border the number of border modules to add, which must be non-negative
     * @return an image representing this QR Code, with padding and scaling
     * @throws IllegalArgumentException if the scale or border is out of range
     */
    public Bitmap toBitmap(int scale, int border) {
        if (scale <= 0 || border < 0)
            throw new IllegalArgumentException("Value out of range");
        Bitmap result = Bitmap.createBitmap((size + border * 2) * scale, (size + border * 2) * scale,
                Bitmap.Config.ARGB_8888);
        for (int y = 0; y < result.getHeight(); y++) {
            for (int x = 0; x < result.getWidth(); x++) {
                int val = getModule(x / scale - border, y / scale - border);  // 0 or 1
                result.setPixel(x, y, val == 1 ? 0xFF000000 : 0xFFFFFFFF);
            }
        }
        return result;
    }

	/*---- Private helper methods for constructor: Drawing function modules ----*/

    private void drawFunctionPatterns() {
        // Draw the horizontal and vertical timing patterns
        for (int i = 0; i < size; i++) {
            setFunctionModule(6, i, i % 2 == 0);
            setFunctionModule(i, 6, i % 2 == 0);
        }

        // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
        drawFinderPattern(3, 3);
        drawFinderPattern(size - 4, 3);
        drawFinderPattern(3, size - 4);

        // Draw the numerous alignment patterns
        int[] alignPatPos = getAlignmentPatternPositions(version);
        int numAlign = alignPatPos.length;
        for (int i = 0; i < numAlign; i++) {
            for (int j = 0; j < numAlign; j++) {
                if (i == 0 && j == 0 || i == 0 && j == numAlign - 1 || i == numAlign - 1 && j == 0)
                    continue;  // Skip the three finder corners
                else
                    drawAlignmentPattern(alignPatPos[i], alignPatPos[j]);
            }
        }

        // Draw configuration data
        drawFormatBits(0);  // Dummy mask value; overwritten later in the constructor
        drawVersion();
    }


    // Draws two copies of the format bits (with its own error correction code)
    // based on the given mask and this object's error correction level field.
    private void drawFormatBits(int mask) {
        // Calculate error correction code and pack bits
        int data = errorCorrectionLevel.formatBits << 3 | mask;  // errCorrLvl is uint2, mask is uint3
        int rem = data;
        for (int i = 0; i < 10; i++)
            rem = (rem << 1) ^ ((rem >>> 9) * 0x537);
        data = data << 10 | rem;
        data ^= 0x5412;  // uint15
        if (data >>> 15 != 0)
            throw new AssertionError();

        // Draw first copy
        for (int i = 0; i <= 5; i++)
            setFunctionModule(8, i, ((data >>> i) & 1) != 0);
        setFunctionModule(8, 7, ((data >>> 6) & 1) != 0);
        setFunctionModule(8, 8, ((data >>> 7) & 1) != 0);
        setFunctionModule(7, 8, ((data >>> 8) & 1) != 0);
        for (int i = 9; i < 15; i++)
            setFunctionModule(14 - i, 8, ((data >>> i) & 1) != 0);

        // Draw second copy
        for (int i = 0; i <= 7; i++)
            setFunctionModule(size - 1 - i, 8, ((data >>> i) & 1) != 0);
        for (int i = 8; i < 15; i++)
            setFunctionModule(8, size - 15 + i, ((data >>> i) & 1) != 0);
        setFunctionModule(8, size - 8, true);
    }


    // Draws two copies of the version bits (with its own error correction code),
    // based on this object's version field (which only has an effect for 7 <= version <= 40).
    private void drawVersion() {
        if (version < 7)
            return;

        // Calculate error correction code and pack bits
        int rem = version;  // version is uint6, in the range [7, 40]
        for (int i = 0; i < 12; i++)
            rem = (rem << 1) ^ ((rem >>> 11) * 0x1F25);
        int data = version << 12 | rem;  // uint18
        if (data >>> 18 != 0)
            throw new AssertionError();

        // Draw two copies
        for (int i = 0; i < 18; i++) {
            boolean bit = ((data >>> i) & 1) != 0;
            int a = size - 11 + i % 3, b = i / 3;
            setFunctionModule(a, b, bit);
            setFunctionModule(b, a, bit);
        }
    }


    // Draws a 9*9 finder pattern including the border separator, with the center module at (x, y).
    private void drawFinderPattern(int x, int y) {
        for (int i = -4; i <= 4; i++) {
            for (int j = -4; j <= 4; j++) {
                int dist = Math.max(Math.abs(i), Math.abs(j));  // Chebyshev/infinity norm
                int xx = x + j, yy = y + i;
                if (0 <= xx && xx < size && 0 <= yy && yy < size)
                    setFunctionModule(xx, yy, dist != 2 && dist != 4);
            }
        }
    }


    // Draws a 5*5 alignment pattern, with the center module at (x, y).
    private void drawAlignmentPattern(int x, int y) {
        for (int i = -2; i <= 2; i++) {
            for (int j = -2; j <= 2; j++)
                setFunctionModule(x + j, y + i, Math.max(Math.abs(i), Math.abs(j)) != 1);
        }
    }


    // Sets the color of a module and marks it as a function module.
    // Only used by the constructor. Coordinates must be in range.
    private void setFunctionModule(int x, int y, boolean isBlack) {
        modules[y][x] = isBlack;
        isFunction[y][x] = true;
    }
	
	
	/*---- Private helper methods for constructor: Codewords and masking ----*/

    // Returns a new byte string representing the given data with the appropriate error correction
    // codewords appended to it, based on this object's version and error correction level.
    private byte[] appendErrorCorrection(byte[] data) {
        if (data.length != getNumDataCodewords(version, errorCorrectionLevel))
            throw new IllegalArgumentException();

        // Calculate parameter numbers
        int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[errorCorrectionLevel.ordinal()][version];
        int totalEcc = NUM_ERROR_CORRECTION_CODEWORDS[errorCorrectionLevel.ordinal()][version];
        if (totalEcc % numBlocks != 0)
            throw new AssertionError();
        int blockEccLen = totalEcc / numBlocks;
        int numShortBlocks = numBlocks - getNumRawDataModules(version) / 8 % numBlocks;
        int shortBlockLen = getNumRawDataModules(version) / 8 / numBlocks;

        // Split data into blocks and append ECC to each block
        byte[][] blocks = new byte[numBlocks][];
        ReedSolomonGenerator rs = new ReedSolomonGenerator(blockEccLen);
        for (int i = 0, k = 0; i < numBlocks; i++) {
            byte[] dat = Arrays.copyOfRange(data, k, k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1));
            byte[] block = Arrays.copyOf(dat, shortBlockLen + 1);
            k += dat.length;
            byte[] ecc = rs.getRemainder(dat);
            System.arraycopy(ecc, 0, block, block.length - blockEccLen, ecc.length);
            blocks[i] = block;
        }

        // Interleave (not concatenate) the bytes from every block into a single sequence
        byte[] result = new byte[getNumRawDataModules(version) / 8];
        for (int i = 0, k = 0; i < blocks[0].length; i++) {
            for (int j = 0; j < blocks.length; j++) {
                // Skip the padding byte in short blocks
                if (i != shortBlockLen - blockEccLen || j >= numShortBlocks) {
                    result[k] = blocks[j][i];
                    k++;
                }
            }
        }
        return result;
    }


    // Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
    // data area of this QR Code symbol. Function modules need to be marked off before this is called.
    private void drawCodewords(@NonNull byte[] data) {
        if (data.length != getNumRawDataModules(version) / 8)
            throw new IllegalArgumentException();

        int i = 0;  // Bit index into the data
        // Do the funny zigzag scan
        for (int right = size - 1; right >= 1; right -= 2) {  // Index of right column in each column pair
            if (right == 6)
                right = 5;
            for (int vert = 0; vert < size; vert++) {  // Vertical counter
                for (int j = 0; j < 2; j++) {
                    int x = right - j;  // Actual x coordinate
                    boolean upwards = ((right & 2) == 0) ^ (x < 6);
                    int y = upwards ? size - 1 - vert : vert;  // Actual y coordinate
                    if (!isFunction[y][x] && i < data.length * 8) {
                        modules[y][x] = ((data[i >>> 3] >>> (7 - (i & 7))) & 1) != 0;
                        i++;
                    }
                    // If there are any remainder bits (0 to 7), they are already
                    // set to 0/false/white when the grid of modules was initialized
                }
            }
        }
        if (i != data.length * 8)
            throw new AssertionError();
    }


    // XORs the data modules in this QR Code with the given mask pattern. Due to XOR's mathematical
    // properties, calling applyMask(m) twice with the same value is equivalent to no change at all.
    // This means it is possible to apply a mask, undo it, and try another mask. Note that a final
    // well-formed QR Code symbol needs exactly one mask applied (not zero, not two, etc.).
    private void applyMask(int mask) {
        if (mask < 0 || mask > 7)
            throw new IllegalArgumentException("Mask value out of range");
        for (int y = 0; y < size; y++) {
            for (int x = 0; x < size; x++) {
                boolean invert;
                switch (mask) {
                    case 0:
                        invert = (x + y) % 2 == 0;
                        break;
                    case 1:
                        invert = y % 2 == 0;
                        break;
                    case 2:
                        invert = x % 3 == 0;
                        break;
                    case 3:
                        invert = (x + y) % 3 == 0;
                        break;
                    case 4:
                        invert = (x / 3 + y / 2) % 2 == 0;
                        break;
                    case 5:
                        invert = x * y % 2 + x * y % 3 == 0;
                        break;
                    case 6:
                        invert = (x * y % 2 + x * y % 3) % 2 == 0;
                        break;
                    case 7:
                        invert = ((x + y) % 2 + x * y % 3) % 2 == 0;
                        break;
                    default:
                        throw new AssertionError();
                }
                modules[y][x] ^= invert & !isFunction[y][x];
            }
        }
    }


    // A messy helper function for the constructors. This QR Code must be in an unmasked state when this
    // method is called. The given argument is the requested mask, which is -1 for auto or 0 to 7 for fixed.
    // This method applies and returns the actual mask chosen, from 0 to 7.
    private int handleConstructorMasking(int mask) {
        if (mask == -1) {  // Automatically choose best mask
            int minPenalty = Integer.MAX_VALUE;
            for (int i = 0; i < 8; i++) {
                drawFormatBits(i);
                applyMask(i);
                int penalty = getPenaltyScore();
                if (penalty < minPenalty) {
                    mask = i;
                    minPenalty = penalty;
                }
                applyMask(i);  // Undoes the mask due to XOR
            }
        }
        if (mask < 0 || mask > 7)
            throw new AssertionError();
        drawFormatBits(mask);  // Overwrite old format bits
        applyMask(mask);  // Apply the final choice of mask
        return mask;  // The caller shall assign this value to the final-declared field
    }


    // Calculates and returns the penalty score based on state of this QR Code's current modules.
    // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
    private int getPenaltyScore() {
        int result = 0;

        // Adjacent modules in row having same color
        for (int y = 0; y < size; y++) {
            boolean colorX = modules[y][0];
            for (int x = 1, runX = 1; x < size; x++) {
                if (modules[y][x] != colorX) {
                    colorX = modules[y][x];
                    runX = 1;
                } else {
                    runX++;
                    if (runX == 5)
                        result += PENALTY_N1;
                    else if (runX > 5)
                        result++;
                }
            }
        }
        // Adjacent modules in column having same color
        for (int x = 0; x < size; x++) {
            boolean colorY = modules[0][x];
            for (int y = 1, runY = 1; y < size; y++) {
                if (modules[y][x] != colorY) {
                    colorY = modules[y][x];
                    runY = 1;
                } else {
                    runY++;
                    if (runY == 5)
                        result += PENALTY_N1;
                    else if (runY > 5)
                        result++;
                }
            }
        }

        // 2*2 blocks of modules having same color
        for (int y = 0; y < size - 1; y++) {
            for (int x = 0; x < size - 1; x++) {
                boolean color = modules[y][x];
                if (color == modules[y][x + 1] &&
                        color == modules[y + 1][x] &&
                        color == modules[y + 1][x + 1])
                    result += PENALTY_N2;
            }
        }

        // Finder-like pattern in rows
        for (int y = 0; y < size; y++) {
            for (int x = 0, bits = 0; x < size; x++) {
                bits = ((bits << 1) & 0x7FF) | (modules[y][x] ? 1 : 0);
                if (x >= 10 && (bits == 0x05D || bits == 0x5D0))  // Needs 11 bits accumulated
                    result += PENALTY_N3;
            }
        }
        // Finder-like pattern in columns
        for (int x = 0; x < size; x++) {
            for (int y = 0, bits = 0; y < size; y++) {
                bits = ((bits << 1) & 0x7FF) | (modules[y][x] ? 1 : 0);
                if (y >= 10 && (bits == 0x05D || bits == 0x5D0))  // Needs 11 bits accumulated
                    result += PENALTY_N3;
            }
        }

        // Balance of black and white modules
        int black = 0;
        for (boolean[] row : modules) {
            for (boolean color : row) {
                if (color)
                    black++;
            }
        }
        int total = size * size;
        // Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
        for (int k = 0; black * 20 < (9 - k) * total || black * 20 > (11 + k) * total; k++)
            result += PENALTY_N4;
        return result;
    }
	
	
	
	/*---- Private static helper functions ----*/

    // Returns a set of positions of the alignment patterns in ascending order. These positions are
    // used on both the x and y axes. Each value in the resulting array is in the range [0, 177).
    // This stateless pure function could be implemented as table of 40 variable-length lists of unsigned bytes.
    private static int[] getAlignmentPatternPositions(int ver) {
        if (ver < 1 || ver > 40)
            throw new IllegalArgumentException("Version number out of range");
        else if (ver == 1)
            return new int[]{};
        else {
            int numAlign = ver / 7 + 2;
            int step;
            if (ver != 32)
                step = (ver * 4 + numAlign * 2 + 1) / (2 * numAlign - 2) * 2;  // ceil((size - 13) / (2*numAlign - 2)) * 2
            else  // C-C-C-Combo breaker!
                step = 26;

            int[] result = new int[numAlign];
            int size = ver * 4 + 17;
            result[0] = 6;
            for (int i = result.length - 1, pos = size - 7; i >= 1; i--, pos -= step)
                result[i] = pos;
            return result;
        }
    }


    // Returns the number of raw data modules (bits) available at the given version number.
    // These data modules are used for both user data codewords and error correction codewords.
    // This stateless pure function could be implemented as a 40-entry lookup table.
    private static int getNumRawDataModules(int ver) {
        if (ver < 1 || ver > 40)
            throw new IllegalArgumentException("Version number out of range");

        int size = ver * 4 + 17;
        int result = size * size;   // Number of modules in the whole QR symbol square
        result -= 64 * 3;           // Subtract the three finders with separators
        result -= 15 * 2 + 1;       // Subtract the format information and black module
        result -= (size - 16) * 2;  // Subtract the timing patterns
        // The five lines above are equivalent to: int result = (16 * ver + 128) * ver + 64;
        if (ver >= 2) {
            int numAlign = ver / 7 + 2;
            result -= (numAlign - 1) * (numAlign - 1) * 25;  // Subtract alignment patterns not overlapping with timing patterns
            result -= (numAlign - 2) * 2 * 20;  // Subtract alignment patterns that overlap with timing patterns
            // The two lines above are equivalent to: result -= (25 * numAlign - 10) * numAlign - 55;
            if (ver >= 7)
                result -= 18 * 2;  // Subtract version information
        }
        return result;
    }


    // Returns the number of 8-bit data (i.e. not error correction) codewords contained in any
    // QR Code of the given version number and error correction level, with remainder bits discarded.
    // This stateless pure function could be implemented as a (40*4)-cell lookup table.
    static int getNumDataCodewords(int ver, Ecc ecl) {
        if (ver < 1 || ver > 40)
            throw new IllegalArgumentException("Version number out of range");
        return getNumRawDataModules(ver) / 8 - NUM_ERROR_CORRECTION_CODEWORDS[ecl.ordinal()][ver];
    }
	
	
	/*---- Private tables of constants ----*/

    // For use in getPenaltyScore(), when evaluating which mask is best.
    private static final int PENALTY_N1 = 3;
    private static final int PENALTY_N2 = 3;
    private static final int PENALTY_N3 = 40;
    private static final int PENALTY_N4 = 10;


    private static final short[][] NUM_ERROR_CORRECTION_CODEWORDS = {
            // Version: (note that index 0 is for padding, and is set to an illegal value)
            //0,  1,  2,  3,  4,  5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,   25,   26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40    Error correction level
            {-1, 7, 10, 15, 20, 26, 36, 40, 48, 60, 72, 80, 96, 104, 120, 132, 144, 168, 180, 196, 224, 224, 252, 270, 300, 312, 336, 360, 390, 420, 450, 480, 510, 540, 570, 570, 600, 630, 660, 720, 750},  // Low
            {-1, 10, 16, 26, 36, 48, 64, 72, 88, 110, 130, 150, 176, 198, 216, 240, 280, 308, 338, 364, 416, 442, 476, 504, 560, 588, 644, 700, 728, 784, 812, 868, 924, 980, 1036, 1064, 1120, 1204, 1260, 1316, 1372},  // Medium
            {-1, 13, 22, 36, 52, 72, 96, 108, 132, 160, 192, 224, 260, 288, 320, 360, 408, 448, 504, 546, 600, 644, 690, 750, 810, 870, 952, 1020, 1050, 1140, 1200, 1290, 1350, 1440, 1530, 1590, 1680, 1770, 1860, 1950, 2040},  // Quartile
            {-1, 17, 28, 44, 64, 88, 112, 130, 156, 192, 224, 264, 308, 352, 384, 432, 480, 532, 588, 650, 700, 750, 816, 900, 960, 1050, 1110, 1200, 1260, 1350, 1440, 1530, 1620, 1710, 1800, 1890, 1980, 2100, 2220, 2310, 2430},  // High
    };

    private static final byte[][] NUM_ERROR_CORRECTION_BLOCKS = {
            // Version: (note that index 0 is for padding, and is set to an illegal value)
            //0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
            {-1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 6, 6, 6, 6, 7, 8, 8, 9, 9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25},  // Low
            {-1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5, 5, 8, 9, 9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49},  // Medium
            {-1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8, 8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68},  // Quartile
            {-1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81},  // High
    };
	
	
	
	/*---- Public helper enumeration ----*/

    /**
     * Represents the error correction level used in a QR Code symbol.
     */
    public enum Ecc {
        // These enum constants must be declared in ascending order of error protection,
        // for the sake of the implicit ordinal() method and values() function.
        LOW(1), MEDIUM(0), QUARTILE(3), HIGH(2);

        // In the range 0 to 3 (unsigned 2-bit integer).
        final int formatBits;

        // Constructor.
        private Ecc(int fb) {
            formatBits = fb;
        }
    }
	
	
	
	/*---- Private helper class ----*/

    /**
     * Computes the Reed-Solomon error correction codewords for a sequence of data codewords
     * at a given degree. Objects are immutable, and the state only depends on the degree.
     * This class exists because the divisor polynomial does not need to be recalculated for every input.
     */
    private static final class ReedSolomonGenerator {
		
		/*-- Immutable field --*/

        // Coefficients of the divisor polynomial, stored from highest to lowest power, excluding the leading term which
        // is always 1. For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}.
        private final byte[] coefficients;
		
		
		/*-- Constructor --*/

        /**
         * Creates a Reed-Solomon ECC generator for the specified degree. This could be implemented
         * as a lookup table over all possible parameter values, instead of as an algorithm.
         *
         * @param degree the divisor polynomial degree, which must be between 1 and 255
         * @throws IllegalArgumentException if degree &lt; 1 or degree > 255
         */
        public ReedSolomonGenerator(int degree) {
            if (degree < 1 || degree > 255)
                throw new IllegalArgumentException("Degree out of range");

            // Start with the monomial x^0
            coefficients = new byte[degree];
            coefficients[degree - 1] = 1;

            // Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
            // drop the highest term, and store the rest of the coefficients in order of descending powers.
            // Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
            int root = 1;
            for (int i = 0; i < degree; i++) {
                // Multiply the current product by (x - r^i)
                for (int j = 0; j < coefficients.length; j++) {
                    coefficients[j] = (byte) multiply(coefficients[j] & 0xFF, root);
                    if (j + 1 < coefficients.length)
                        coefficients[j] ^= coefficients[j + 1];
                }
                root = (root << 1) ^ ((root >>> 7) * 0x11D);  // Multiply by 0x02 mod GF(2^8/0x11D)
            }
        }
		
		
		/*-- Method --*/

        /**
         * Computes and returns the Reed-Solomon error correction codewords for the specified sequence of data codewords.
         * The returned object is always a new byte array. This method does not alter this object's state (because it is immutable).
         *
         * @param data the sequence of data codewords
         * @return the Reed-Solomon error correction codewords
         * @throws NullPointerException if the data is {@code null}
         */
        public byte[] getRemainder(@NonNull byte[] data) {
            // Compute the remainder by performing polynomial division
            byte[] result = new byte[coefficients.length];
            for (byte b : data) {
                int factor = (b ^ result[0]) & 0xFF;
                System.arraycopy(result, 1, result, 0, result.length - 1);
                result[result.length - 1] = 0;
                for (int i = 0; i < result.length; i++)
                    result[i] ^= multiply(coefficients[i] & 0xFF, factor);
            }
            return result;
        }
		
		
		/*-- Static function --*/

        // Returns the product of the two given field elements modulo GF(2^8/0x11D). The arguments and result
        // are unsigned 8-bit integers. This could be implemented as a lookup table of 256*256 entries of uint8.
        private static int multiply(int x, int y) {
            if (x >>> 8 != 0 || y >>> 8 != 0)
                throw new IllegalArgumentException("Byte out of range");
            // Russian peasant multiplication
            int z = 0;
            for (int i = 7; i >= 0; i--) {
                z = (z << 1) ^ ((z >>> 7) * 0x11D);
                z ^= ((y >>> i) & 1) * x;
            }
            if (z >>> 8 != 0)
                throw new AssertionError();
            return z;
        }

    }

}