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Java implementation of the SciJava Ops matching engine.
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/*
 * #%L
 * Java implementation of the SciJava Ops matching engine.
 * %%
 * Copyright (C) 2016 - 2024 SciJava developers.
 * %%
 * 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.
 * 
 * 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 HOLDERS 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.
 * #L%
 */

package org.scijava.ops.engine.matcher.impl;

import org.scijava.ops.api.Hints;
import org.scijava.ops.api.OpInfo;
import org.scijava.ops.engine.exceptions.impl.PrivateOpException;
import org.scijava.ops.engine.struct.FieldInstance;
import org.scijava.ops.engine.struct.FieldParameterMemberParser;
import org.scijava.ops.engine.util.Infos;
import org.scijava.ops.spi.OpField;
import org.scijava.struct.Struct;
import org.scijava.struct.StructInstance;
import org.scijava.struct.Structs;
import org.scijava.common3.Types;

import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.List;

/**
 * Metadata about an Op implementation defined as a field.
 *
 * @author Curtis Rueden
 */
public class DefaultOpFieldInfo implements OpInfo {

	private final Object instance;
	private final Field field;
	private final String version;
	private final String description;
	private final List names;
	private final double priority;

	private final Struct struct;
	private final Hints hints;

	public DefaultOpFieldInfo( //
		final Object instance, //
		final Field field, //
		final String version, //
		final String description, //
		final Hints hints, //
		final double priority, //
		final String... names //
	) {
		this.instance = instance;
		this.version = version;
		this.description = description;
		this.field = field;
		this.names = Arrays.asList(names);
		this.priority = priority;
		this.hints = hints;

		if (Modifier.isStatic(field.getModifiers())) {
			// Field is static; instance must be null.
			if (instance != null) {
				// Static field; instance should be null!
			}
		}
		else {
			// NB: Field is not static; instance must match field.getDeclaringClass().
			if (!field.getDeclaringClass().isInstance(instance)) {
				// Mismatch between given object and the class containing the field
				// But: we need to have proper case logic for the field being static or
				// not.
			}
		}
		// Reject all non public fields
		if (!Modifier.isPublic(field.getModifiers())) {
			throw new PrivateOpException(field);
		}

		// NB: Subclassing a collection and inheriting its fields is NOT
		// ALLOWED!
		Type structType = Types.typeOf(field, field.getDeclaringClass());
		FieldInstance fieldInstance = new FieldInstance(field, instance);
		struct = Structs.from(fieldInstance, structType,
			new FieldParameterMemberParser());
		Infos.validate(this);
	}

	// -- OpInfo methods --

	@Override
	public List names() {
		return names;
	}

	@Override
	public String description() {
		return description;
	}

	@Override
	public Type opType() {
		return field.getGenericType();
		// return Types.fieldType(field, subClass);
	}

	@Override
	public Struct struct() {
		return struct;
	}

	@Override
	public Hints declaredHints() {
		return hints;
	}

	@Override
	public double priority() {
		return priority;
	}

	@Override
	public String implementationName() {
		// Get generic string without modifiers and return type
		String fullyQualifiedField = field.toGenericString();
		int lastDotPos = fullyQualifiedField.lastIndexOf('.');
		fullyQualifiedField = fullyQualifiedField.substring(0, lastDotPos) + "$" +
			fullyQualifiedField.substring(lastDotPos + 1);
		String packageName = field.getDeclaringClass().getPackageName();
		int classNameIndex = fullyQualifiedField.lastIndexOf(packageName);
		return fullyQualifiedField.substring(classNameIndex);
	}

	@Override
	public StructInstance createOpInstance(List dependencies) {
		// NB: dependencies are not allowed on field Ops, since field Ops can only
		// point to a single instance, which allows successive matching calls to
		// overwrite the dependencies used on earlier matching calls.
		// This can happen if (a) a single Field is matched multiple times, using
		// different dependencies, or if (b) multiple fields point to the same
		// object.
		if (dependencies != null && !dependencies.isEmpty())
			throw new IllegalArgumentException(
				"Op fields are not allowed to have any Op dependencies.");
		// NB: In general, there is no way to create a new instance of the field
		// value.
		// Calling clone() may or may not work; it does not work with e.g. lambdas.
		// Better to just use the same value directly, rather than trying to copy.
		try {
			final Object object = field.get(instance);
			// TODO: Wrap object in a generic holder with the same interface.
			return struct().createInstance(object);
		}
		catch (final IllegalAccessException exc) {
			// FIXME
			exc.printStackTrace();
			throw new RuntimeException(exc);
		}
	}

	@Override
	public AnnotatedElement getAnnotationBearer() {
		return field;
	}

	@Override
	public String version() {
		return version;
	}

	/**
	 * For an {@link OpField}, we define the implementation as the concatenation
	 * of:
	 * 
	 * The fully qualified name of the class containing the field
	 * The method field
	 * The version of the class containing the field, with a preceding
	 * {@code @}
	 * 
	 * 
	 * For example, for a field {@code baz} in class {@code com.example.foo.Bar},
	 * you might have
	 * 

	 * {@code [email protected]}
	 * 
	 */
	@Override
	public String id() {
		return OpInfo.IMPL_DECLARATION + implementationName() + "@" + version();
	}

	// -- Object methods --

	@Override
	public boolean equals(final Object o) {
		if (!(o instanceof DefaultOpFieldInfo)) return false;
		final OpInfo that = (OpInfo) o;
		return struct().equals(that.struct());
	}

	@Override
	public int hashCode() {
		return struct().hashCode();
	}

	@Override
	public String toString() {
		return Infos.describe(this);
	}

}