/*
 * Copyright 2007 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.
 */

/*namespace com.google.zxing.common.reedsolomon {*/

import GenericGFPoly from './GenericGFPoly';
import Exception from './../../Exception';
import Integer from './../../util/Integer';

/**
 * <p>This class contains utility methods for performing mathematical operations over
 * the Galois Fields. Operations use a given primitive polynomial in calculations.</p>
 *
 * <p>Throughout this package, elements of the GF are represented as an {@code int}
 * for convenience and speed (but at the cost of memory).
 * </p>
 *
 * @author Sean Owen
 * @author David Olivier
 */
export default class GenericGF {

    public static AZTEC_DATA_12 = new GenericGF(0x1069, 4096, 1); // x^12 + x^6 + x^5 + x^3 + 1
    public static AZTEC_DATA_10 = new GenericGF(0x409, 1024, 1); // x^10 + x^3 + 1
    public static AZTEC_DATA_6 = new GenericGF(0x43, 64, 1); // x^6 + x + 1
    public static AZTEC_PARAM = new GenericGF(0x13, 16, 1); // x^4 + x + 1
    public static QR_CODE_FIELD_256 = new GenericGF(0x011D, 256, 0); // x^8 + x^4 + x^3 + x^2 + 1
    public static DATA_MATRIX_FIELD_256 = new GenericGF(0x012D, 256, 1); // x^8 + x^5 + x^3 + x^2 + 1
    public static AZTEC_DATA_8 = GenericGF.DATA_MATRIX_FIELD_256;
    public static MAXICODE_FIELD_64 = GenericGF.AZTEC_DATA_6;

    private expTable: Int32Array;
    private logTable: Int32Array;
    private zero: GenericGFPoly;
    private one: GenericGFPoly;

    /**
     * Create a representation of GF(size) using the given primitive polynomial.
     *
     * @param primitive irreducible polynomial whose coefficients are represented by
     *  the bits of an int, where the least-significant bit represents the constant
     *  coefficient
     * @param size the size of the field
     * @param b the factor b in the generator polynomial can be 0- or 1-based
     *  (g(x) = (x+a^b)(x+a^(b+1))...(x+a^(b+2t-1))).
     *  In most cases it should be 1, but for QR code it is 0.
     */
    public constructor(private primitive: number /*int*/, private size: number /*int*/, private generatorBase: number /*int*/) {

        const expTable = new Int32Array(size);
        let x = 1;
        for (let i = 0; i < size; i++) {
            expTable[i] = x;
            x *= 2; // we're assuming the generator alpha is 2
            if (x >= size) {
                x ^= primitive;
                x &= size - 1;
            }
        }
        this.expTable = expTable;

        const logTable = new Int32Array(size);
        for (let i = 0; i < size - 1; i++) {
            logTable[expTable[i]] = i;
        }
        this.logTable = logTable;

        // logTable[0] == 0 but this should never be used
        this.zero = new GenericGFPoly(this, Int32Array.from([0]));
        this.one = new GenericGFPoly(this, Int32Array.from([1]));
    }

    public getZero(): GenericGFPoly {
        return this.zero;
    }

    public getOne(): GenericGFPoly {
        return this.one;
    }

    /**
     * @return the monomial representing coefficient * x^degree
     */
    public buildMonomial(degree: number /*int*/, coefficient: number /*int*/): GenericGFPoly {
        if (degree < 0) {
            throw new Exception(Exception.IllegalArgumentException);
        }
        if (coefficient === 0) {
            return this.zero;
        }
        const coefficients = new Int32Array(degree + 1);
        coefficients[0] = coefficient;
        return new GenericGFPoly(this, coefficients);
    }

    /**
     * Implements both addition and subtraction -- they are the same in GF(size).
     *
     * @return sum/difference of a and b
     */
    public static addOrSubtract(a: number /*int*/, b: number /*int*/): number /*int*/ {
        return a ^ b;
    }

    /**
     * @return 2 to the power of a in GF(size)
     */
    public exp(a: number /*int*/): number /*int*/ {
        return this.expTable[a];
    }

    /**
     * @return base 2 log of a in GF(size)
     */
    public log(a: number /*int*/): number /*int*/ {
        if (a === 0) {
            throw new Exception(Exception.IllegalArgumentException);
        }
        return this.logTable[a];
    }

    /**
     * @return multiplicative inverse of a
     */
    public inverse(a: number /*int*/): number /*int*/ {
        if (a === 0) {
            throw new Exception(Exception.ArithmeticException);
        }
        return this.expTable[this.size - this.logTable[a] - 1];
    }

    /**
     * @return product of a and b in GF(size)
     */
    public multiply(a: number /*int*/, b: number /*int*/): number /*int*/ {
        if (a === 0 || b === 0) {
            return 0;
        }
        return this.expTable[(this.logTable[a] + this.logTable[b]) % (this.size - 1)];
    }

    public getSize(): number /*int*/ {
        return this.size;
    }

    public getGeneratorBase(): number /*int*/ {
        return this.generatorBase;
    }

    /*@Override*/
    public toString(): string {
        return 'GF(0x' + Integer.toHexString(this.primitive) + ',' + this.size + ')';
    }

    public equals(o: Object): boolean {
        return o === this;
    }
}