/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2023, Jean-Marie Dautelle, Werner Keil, Otavio Santana.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of JSR-385, Indriya nor the names of their contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tech.units.indriya.function;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Objects;

import javax.measure.MeasurementException;
import javax.measure.Quantity;
import javax.measure.Quantity.Scale;
import javax.measure.Unit;
import javax.measure.UnitConverter;

import tech.units.indriya.internal.function.Calculator;
import tech.units.indriya.internal.function.radix.MixedRadixSupport;
import tech.units.indriya.internal.function.radix.Radix;
import tech.units.indriya.quantity.MixedQuantity;
import tech.units.indriya.quantity.Quantities;

/**
 * Immutable class that represents mixed-radix units (like "hour:min:sec" or
 * "ft, in")
 * 
 * 
 * @author Andi Huber
 * @author Werner Keil
 * @version 2.3, Jun 5, 2023
 * @since 2.0
 * @see <a href="https://en.wikipedia.org/wiki/Mixed_radix">Wikipedia: Mixed
 *      radix</a>
 * @see <a href=
 *      "https://reference.wolfram.com/language/ref/MixedUnit.html">Wolfram
 *      Language & System: MixedUnit</a>
 * @see <a href="https://en.wikipedia.org/wiki/Metrication">Wikipedia:
 *      Metrication</a>
 * @see MixedQuantity
 */
public final class MixedRadix<Q extends Quantity<Q>> {

        // -- PRIVATE FIELDS

        @Override
        public String toString() {
                return "MixedRadix [units=" + mixedRadixUnits + "]";
        }

        private final PrimaryUnitPickState pickState;
        private final Unit<Q> primaryUnit;
        private final List<Unit<Q>> mixedRadixUnits;
        private final MixedRadixSupport mixedRadixSupport;

        // -- PRIMARY UNIT PICK CONVENTION

        public static enum PrimaryUnitPick {
                LEADING_UNIT, TRAILING_UNIT
        }

        public static final PrimaryUnitPick PRIMARY_UNIT_PICK_DEFAULT = PrimaryUnitPick.TRAILING_UNIT;

        public static PrimaryUnitPick PRIMARY_UNIT_PICK = PRIMARY_UNIT_PICK_DEFAULT;

        // -- FACTORIES

        public static <X extends Quantity<X>> MixedRadix<X> of(Unit<X> leadingUnit) {
                Objects.requireNonNull(leadingUnit);
                return new MixedRadix<>(PrimaryUnitPickState.pickByConvention(), Collections.singletonList(leadingUnit));
        }

        @SafeVarargs
        public static <X extends Quantity<X>> MixedRadix<X> of(Unit<X>... units) {
                if (units == null || units.length < 1) {
                        throw new IllegalArgumentException("at least the leading unit is required");
                }
                return of(Arrays.asList(units));
        }

        public static <X extends Quantity<X>> MixedRadix<X> of(Collection<Unit<X>> units) {
                if (units == null || units.size() < 1) {
                        throw new IllegalArgumentException("at least the leading unit is required");
                }
                MixedRadix<X> mixedRadix = null;
                for (Unit<X> unit : units) {
                        mixedRadix = mixedRadix == null ? of(unit) : mixedRadix.mix(unit);
                }
                return mixedRadix;
        }

        public static <X extends Quantity<X>> MixedRadix<X> ofPrimary(Unit<X> primaryUnit) {
                Objects.requireNonNull(primaryUnit);
                return new MixedRadix<>(PrimaryUnitPickState.pickLeading(), Collections.singletonList(primaryUnit));
        }

        public MixedRadix<Q> mix(Unit<Q> mixedRadixUnit) {
                Objects.requireNonNull(mixedRadixUnit);
                return append(pickState, mixedRadixUnit); // pickState is immutable, so reuse
        }

        MixedRadix<Q> mixPrimary(Unit<Q> mixedRadixUnit) {
                pickState.assertNotExplicitlyPicked();
                Objects.requireNonNull(mixedRadixUnit);
                return append(PrimaryUnitPickState.pickByExplicitIndex(getUnitCount()), mixedRadixUnit);
        }

        // -- GETTERS

        public Unit<Q> getPrimaryUnit() {
                return primaryUnit;
        }

        private Unit<Q> getTrailingUnit() {
                return mixedRadixUnits.get(mixedRadixUnits.size() - 1);
        }

        public List<Unit<Q>> getUnits() {
                return Collections.unmodifiableList(mixedRadixUnits);
        }

        private int getUnitCount() {
                return mixedRadixUnits.size();
        }

        // -- QUANTITY FACTORY

        /**
         * Creates a {@link Quantity} from given {@code values} and {@code scale}.
         * @param values - numbers corresponding to the radices in most significant first order, 
     *      allowed to be of shorter length than the total count of radices of this {@code MixedRadix} instance
         * @param scale - the {@link Scale} to be used for the returned {@link Quantity}
         */
        public Quantity<Q> createQuantity(final Number[] values, final Scale scale) {
            Objects.requireNonNull(scale);
            guardAgainstIllegalNumbersArgument(values);

                Number sum = mixedRadixSupport.sumMostSignificant(values);

                return Quantities.getQuantity(sum, getTrailingUnit(), scale).to(getPrimaryUnit());
        }

    public Quantity<Q> createQuantity(Number... values) {
                return createQuantity(values, Scale.ABSOLUTE);
        }

    /**
     * Creates a {@link MixedQuantity} from given {@code values} and {@code scale}.
     * <p>
     * Note: Not every {@code MixedQuantity} can be represented by a {@code MixedRadix}. 
     * {@code MixedRadix} strictly requires its coefficients to be in decreasing order of significance, 
     * while a {@code MixedQuantity} in principle does not.
     * 
     * @param values - numbers corresponding to the radix coefficients in most significant first order, 
     *      allowed to be of shorter length than the total count of radix coefficients of this 
     *      {@code MixedRadix} instance
     * @param scale - the {@link Scale} to be used for the elements of the returned {@link MixedQuantity}
     */
        public MixedQuantity<Q> createMixedQuantity(final Number[] values, final Scale scale) {
                Objects.requireNonNull(scale);
                guardAgainstIllegalNumbersArgument(values);

                List<Quantity<Q>> quantities = new ArrayList<>();
                for (int i = 0; i < values.length; i++) {
                        quantities.add(Quantities.getQuantity(values[i], mixedRadixUnits.get(i), scale));
                }
                return MixedQuantity.of(quantities);
        }

        public MixedQuantity<Q> createMixedQuantity(Number... values) {
                return createMixedQuantity(values, Scale.ABSOLUTE);
        }
        
        // -- VALUE EXTRACTION

        public Number[] extractValues(Quantity<Q> quantity) {
                Objects.requireNonNull(quantity);
                final Number[] target = new Number[mixedRadixUnits.size()];
                return extractValuesInto(quantity, target);
        }

        public Number[] extractValuesInto(Quantity<Q> quantity, Number[] target) {
                Objects.requireNonNull(quantity);
                Objects.requireNonNull(target);

                visitQuantity(quantity, target.length, (index, unit, value) -> {
                        target[index] = value;
                });

                return target;
        }

        // -- THE VISITOR

        @FunctionalInterface
        private static interface Visitor<Q extends Quantity<Q>> {
                void accept(int index, Unit<Q> unit, Number value);
        }

        // -- IMPLEMENTATION DETAILS
        
   private void guardAgainstIllegalNumbersArgument(Number[] values) {
        if (values == null || values.length < 1) {
            throw new IllegalArgumentException("at least the leading unit's number is required");
        }

        int totalValuesGiven = values.length;
        int totalValuesAllowed = mixedRadixUnits.size();

        if (totalValuesGiven > totalValuesAllowed) {
            String message = String.format(
                    "number of values given <%d> exceeds the number of mixed-radix units available <%d>",
                    totalValuesGiven, totalValuesAllowed);
            throw new IllegalArgumentException(message);
        }
    }
        
        void visitQuantity(Quantity<Q> quantity, int maxPartsToVisit, Visitor<Q> partVisitor) {
                final int partsToVisitCount = Math.min(maxPartsToVisit, getUnitCount());

                // corner case (partsToVisitCount == 0)

                if (partsToVisitCount == 0) {
                        return;
                }

                // for partsToVisitCount >= 1

                final Number value_inTrailingUnits = quantity.to(getTrailingUnit()).getValue();
                final List<Number> extractedValues = new ArrayList<>(getUnitCount());

                mixedRadixSupport.visitRadixNumbers(value_inTrailingUnits, extractedValues::add);

                for (int i = 0; i < partsToVisitCount; ++i) {
                        int invertedIndex = getUnitCount() - 1 - i;
                        partVisitor.accept(i, mixedRadixUnits.get(i), extractedValues.get(invertedIndex));
                }
        }

        /**
         * 
         * @param primaryUnitIndex - if negative, the index is relative to the number of
         *                         units
         * @param mixedRadixUnits
         */
        private MixedRadix(PrimaryUnitPickState pickState, final List<Unit<Q>> mixedRadixUnits) {
                this.pickState = pickState;
                this.mixedRadixUnits = mixedRadixUnits;
                this.primaryUnit = mixedRadixUnits.get(pickState.nonNegativePrimaryUnitIndex(getUnitCount()));

                final Radix[] radices = new Radix[getUnitCount() - 1];
                for (int i = 0; i < radices.length; ++i) {
                        Unit<Q> higher = mixedRadixUnits.get(i);
                        Unit<Q> lesser = mixedRadixUnits.get(i + 1);
                        radices[i] = toRadix(higher.getConverterTo(lesser));
                }

                this.mixedRadixSupport = new MixedRadixSupport(radices);

        }

        private Radix toRadix(UnitConverter converter) {
                return Radix.ofMultiplyConverter(converter);
        }

        private MixedRadix<Q> append(PrimaryUnitPickState state, Unit<Q> mixedRadixUnit) {
                Unit<Q> tail = getTrailingUnit();
                assertDecreasingOrderOfSignificanceAndLinearity(tail, mixedRadixUnit);

                final List<Unit<Q>> mixedRadixUnits = new ArrayList<>(this.mixedRadixUnits);
                mixedRadixUnits.add(mixedRadixUnit);
                return new MixedRadix<>(state, mixedRadixUnits);
        }

        private void assertDecreasingOrderOfSignificanceAndLinearity(Unit<Q> tail, Unit<Q> appended) {
                final UnitConverter converter = appended.getConverterTo(tail);
                if (!converter.isLinear()) {
                        String message = String.format("the appended mixed-radix unit <%s> " + "must be linear",
                                        appended.getClass());
                        throw new IllegalArgumentException(message);
                }

                final Number factor = tail.getConverterTo(appended).convert(1);

                if (Calculator.of(factor).abs().isLessThanOne()) {
                        String message = String.format("the appended mixed-radix unit <%s> " + "must be of lesser significance "
                                        + "than the one it is appended to: <%s>", appended.getClass(), tail.getClass());
                        throw new MeasurementException(message);
                }
        }

        private static class PrimaryUnitPickState {

                private final static int LEADING_IS_PRIMARY_UNIT = 0;
                private final static int TRAILING_IS_PRIMARY_UNIT = -1;
                private final boolean explicitlyPicked;
                private final int pickedIndex;

                private static PrimaryUnitPickState pickByConvention() {
                        final int pickedIndex_byConvention;

                        switch (PRIMARY_UNIT_PICK) {
                        case LEADING_UNIT:
                                pickedIndex_byConvention = LEADING_IS_PRIMARY_UNIT;
                                break;

                        case TRAILING_UNIT:
                                pickedIndex_byConvention = TRAILING_IS_PRIMARY_UNIT;
                                break;

                        default:
                                throw new MeasurementException(
                                                String.format("internal error: unmatched switch case <%s>", PRIMARY_UNIT_PICK));
                        }

                        return new PrimaryUnitPickState(false, pickedIndex_byConvention);
                }

                private void assertNotExplicitlyPicked() {
                        if (explicitlyPicked) {
                                throw new IllegalStateException("a primary unit was already picked");
                        }
                }

                private static PrimaryUnitPickState pickByExplicitIndex(int explicitIndex) {
                        return new PrimaryUnitPickState(true, explicitIndex);
                }

                private static PrimaryUnitPickState pickLeading() {
                        return new PrimaryUnitPickState(true, LEADING_IS_PRIMARY_UNIT);
                }

                private PrimaryUnitPickState(boolean explicitlyPicked, int pickedIndex) {
                        this.explicitlyPicked = explicitlyPicked;
                        this.pickedIndex = pickedIndex;
                }

                private int nonNegativePrimaryUnitIndex(int unitCount) {
                        return pickedIndex < 0 ? unitCount + pickedIndex : pickedIndex;
                }
        }
}