/*
 * Copyright (C) 2016-2021, Stichting Mapcode Foundation (http://www.mapcode.com)
 *
 * 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.mapcode;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

// ----------------------------------------------------------------------------------------------
// Package private implementation class. For internal use within the Mapcode implementation only.
// ----------------------------------------------------------------------------------------------

/**
 * This class contains common data structures and methods used by the Mapcode implementation.
 */
@SuppressWarnings("MagicNumber")
final class Common {
    private static final Logger LOG = LoggerFactory.getLogger(Common.class);

    // TODO: Need better name and explanation.
    static final int[] NC = {
            1, 31, 961, 29791, 923521, 28629151, 887503681
    };

    // TODO: Need better name and explanation.
    static final int[] X_SIDE = {
            0, 5, 31, 168, 961, 5208, 29791, 165869, 923521, 5141947
    };

    // TODO: Need better name and explanation.
    static final int[] Y_SIDE = {
            0, 6, 31, 176, 961, 5456, 29791, 165869, 923521, 5141947
    };

    // TODO: Need better name and explanation.
    private static final int[] X_DIVIDER_19 = {
            360, 360, 360, 360, 360, 360, 361, 361, 361, 361,
            362, 362, 362, 363, 363, 363, 364, 364, 365, 366,
            366, 367, 367, 368, 369, 370, 370, 371, 372, 373,
            374, 375, 376, 377, 378, 379, 380, 382, 383, 384,
            386, 387, 388, 390, 391, 393, 394, 396, 398, 399,
            401, 403, 405, 407, 409, 411, 413, 415, 417, 420,
            422, 424, 427, 429, 432, 435, 437, 440, 443, 446,
            449, 452, 455, 459, 462, 465, 469, 473, 476, 480,
            484, 488, 492, 496, 501, 505, 510, 515, 520, 525,
            530, 535, 540, 546, 552, 558, 564, 570, 577, 583,
            590, 598, 605, 612, 620, 628, 637, 645, 654, 664,
            673, 683, 693, 704, 715, 726, 738, 751, 763, 777,
            791, 805, 820, 836, 852, 869, 887, 906, 925, 946,
            968, 990, 1014, 1039, 1066, 1094, 1123, 1154, 1187, 1223,
            1260, 1300, 1343, 1389, 1438, 1490, 1547, 1609, 1676, 1749,
            1828, 1916, 2012, 2118, 2237, 2370, 2521, 2691, 2887, 3114,
            3380, 3696, 4077, 4547, 5139, 5910, 6952, 8443, 10747, 14784,
            23681, 59485
    };

    private Common() {
        // Prevent instantiation.
    }

    static {

        // This code shows a message when assertions are active or disabled. It (ab)uses assert for that...
        // Some of the methods (and tests) take considerably longer with assertions checking, so it's useful
        // to have this information in the log file.

        boolean debug = false;
        //noinspection AssertWithSideEffects
        assert debug = true;
        //noinspection ConstantConditions
        if (debug) {
            LOG.info("Common: assertions are active (JVM runtime option '-ea')");
        } else {
            LOG.debug("Common: assertions are not active, they are bypassed");
        }
    }

    // This method returns a divider for longitude (multiplied by 4), for a given latitude.
    // TODO: Need better names for minY and maxY.
    static int xDivider(final int latMin, final int latMax) {
        assert latMin < latMax;
        if (latMin >= 0) {
            assert (latMax > latMin) && (latMin > 0);
            return X_DIVIDER_19[latMin >> 19];
        } else if (latMax >= 0) {
            assert (latMax > 0) && (0 > latMin);
            return X_DIVIDER_19[0];
        } else {
            assert (0 > latMax) && (latMax > latMin);
            return X_DIVIDER_19[(-latMax) >> 19];
        }
    }

    // TODO: Need to explain what a codex is.
    static int countCityCoordinatesForCountry(final int codex, final int territoryRecord, final int firstTerritoryRecord) {
        assert codex >= 0;
        assert territoryRecord >= 0;
        assert firstTerritoryRecord >= 0;
        final int firstRecord = getFirstNamelessRecord(codex, territoryRecord, firstTerritoryRecord);
        int record = territoryRecord;
        while (Data.getCodex(record) == codex) {
            record++;
        }
        assert firstRecord <= record;
        return record - firstRecord;
    }

    static int getFirstNamelessRecord(final int codex, final int territoryRecord, final int firstTerritoryRecord) {
        assert codex >= 0;
        assert territoryRecord >= 0;
        assert firstTerritoryRecord >= 0;
        int record = territoryRecord;
        while ((record >= firstTerritoryRecord) && Data.isNameless(record) && (Data.getCodex(record) == codex)) {
            record--;
        }
        record++;
        assert record <= territoryRecord;
        return record;
    }
}