/*
 * #%L
 * SciJava library for generic type reasoning.
 * %%
 * 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:
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 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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package org.scijava.types.extract;

import java.lang.reflect.Type;
import java.util.Map;

import org.scijava.priority.Priority;
import org.scijava.common3.Any;
import org.scijava.types.extract.SubTypeExtractor;
import org.scijava.types.extract.TypeExtractor;
import org.scijava.types.extract.TypeReifier;

/**
 * {@link TypeExtractor} plugin which operates on {@link Map} objects.
 * <p>
 * For performance reasons, we examine only one entry of the map, which may be
 * more specifically typed than later entries. Hence the generic types given by
 * this extraction may be overly constrained.
 * </p>
 *
 * @author Curtis Rueden
 */
public class MapTypeExtractor extends SubTypeExtractor<Map<?, ?>> {

	@Override
	public double priority() {
		return Priority.VERY_LOW;
	}

	@Override
	public Class<?> baseClass() {
		return Map.class;
	}

	@Override
	protected Type[] getTypeParameters(TypeReifier r, Map<?, ?> object) {
		// Fast case - empty map
		if (object.isEmpty()) {
			return new Type[] { new Any(), new Any() };
		}
        var e = object.entrySet().iterator().next();
        var keyType = r.reify(e.getKey());
        var valueType = r.reify(e.getValue());
		return new Type[] { keyType, valueType };
	}

}
