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/*
 Copyright © 2020 Petr Panteleyev 
 SPDX-License-Identifier: BSD-2-Clause
 */
package org.panteleyev.fx;

import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.beans.value.WeakChangeListener;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Objects;
import java.util.function.Predicate;

/**
 * This class implements property that wraps {@link Predicate} instance.
 * 
 * Default value is x -> true i.e. {@link PredicateProperty#test(Object)} will return
 * true until the predicate is altered via {@link PredicateProperty#set(Predicate)}.
 *
 * @param  the type of the input to the predicate
 */
public class PredicateProperty extends SimpleObjectProperty> implements Predicate {
    private enum Op {
        AND,
        OR
    }

    private final Collection> inputs = new ArrayList<>();
    private final Op op;

    @SuppressWarnings("FieldCanBeLocal")
    private final ChangeListener> LISTENER = (x, y, newValue) -> onInputUpdate();

    /**
     * Creates an instance with default predicate.
     */
    public PredicateProperty() {
        super(x -> true);
        this.op = null;
    }

    /**
     * Creates an instance with default predicate.
     *
     * @param bean bean of this property
     * @param name name of this property
     */
    public PredicateProperty(Object bean, String name) {
        super(bean, name, x -> true);
        this.op = null;
    }

    /**
     * Creates an instance with the specified predicate value.
     *
     * @param initialValue initial predicate value
     */
    public PredicateProperty(Predicate initialValue) {
        super(initialValue);
        this.op = null;
    }

    /**
     * Creates an instance with the specified predicate value.
     *
     * @param bean         bean of this property
     * @param name         name of this property
     * @param initialValue initial predicate value
     */
    public PredicateProperty(Object bean, String name, Predicate initialValue) {
        super(bean, name, initialValue);
        Objects.requireNonNull(initialValue, "Predicate value cannot be null");
        this.op = null;
    }

    private PredicateProperty(Op op, Collection> inputs) {
        this.op = op;
        this.inputs.addAll(inputs);

        super.set(buildPredicate(op, inputs));

        for (var p : inputs) {
            p.addListener(new WeakChangeListener<>(LISTENER));
        }
    }

    private void onInputUpdate() {
        super.set(buildPredicate(op, inputs));
    }

    private static  Predicate buildPredicate(Op op, Collection> inputs) {
        Predicate result = op == Op.AND ? x -> true : x -> false;
        for (var p : inputs) {
            result = switch (op) {
                case AND -> result.and(p.get());
                case OR -> result.or(p.get());
            };
        }
        return result;
    }

    /**
     * Creates calculated predicate property that produces logical AND from its arguments.
     *
     * @param args arguments
     * @param   type of the input to the predicate
     * @return predicate property
     */
    public static  PredicateProperty and(Collection> args) {
        return new PredicateProperty<>(Op.AND, args);
    }

    /**
     * Creates calculated predicate property that produces logical OR from its arguments.
     *
     * @param args arguments
     * @param   type of the input to the predicate
     * @return predicate property
     */
    public static  PredicateProperty or(Collection> args) {
        return new PredicateProperty<>(Op.OR, args);
    }

    /**
     * Sets the wrapped predicate value.
     *
     * @param predicate predicate value.
     * @throws IllegalStateException if property is calculated
     */
    @Override
    public void set(Predicate predicate) {
        if (op != null) {
            throw new IllegalStateException("Calculated property cannot be set");
        }
        super.set(predicate);
    }

    /**
     * Create a unidirectional binding for this Property.
     *
     * @param observableValue observable this {@link javafx.beans.Observable} should be bound to
     */
    @Override
    public void bind(ObservableValue> observableValue) {
        if (op != null) {
            throw new IllegalStateException("Calculated property cannot be bound");
        }
        super.bind(observableValue);
    }

    /**
     * Sets the wrapped predicate value.
     *
     * @param predicate predicate value.
     * @throws IllegalStateException if property is calculated
     */
    @Override
    public void setValue(Predicate predicate) {
        if (op != null) {
            throw new IllegalStateException("Calculated property cannot be set");
        }
        super.setValue(predicate);
    }

    /**
     * Changes predicate to its initial value, i.e. x -> true.
     *
     * @throws IllegalStateException if property is calculated
     */
    public void reset() {
        if (op != null) {
            throw new IllegalStateException("Calculated property cannot be reset");
        }
        super.setValue(x -> true);
    }

    // Predicate methods

    @Override
    public boolean test(T t) {
        return get().test(t);
    }

    @Override
    public Predicate and(Predicate other) {
        return get().and(other);
    }

    @Override
    public Predicate negate() {
        return get().negate();
    }

    @Override
    public Predicate or(Predicate other) {
        return get().or(other);
    }
}