SmartKeyName.java

/*
 * Copyright 2025 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.data.mongodb.observability;

import io.micrometer.common.KeyValue;
import io.micrometer.common.docs.KeyName;

import java.util.function.Function;

import org.jspecify.annotations.Nullable;

/**
 * @author Mark Paluch
 */
class SmartKeyName<C> implements KeyName {

	private final String name;

	private final boolean required;

	private final Function<C, @Nullable Object> valueFunction;

	private SmartKeyName(String name, boolean required, Function<C, Object> valueFunction) {
		this.required = required;
		this.valueFunction = valueFunction;
		this.name = name;
	}

	public static <C> SmartKeyName<C> required(String name, Function<C, @Nullable Object> valueFunction) {
		return new SmartKeyName<C>(name, true, valueFunction);
	}

	public @Nullable KeyValue valueOf(@Nullable C context) {

		Object value = context != null ? valueFunction.apply(context) : null;

		// TODO having a sophisticated way to skip not required keys would be nice if the value cannot be provided.
		if (!isRequired()) {
			return null;
		}

		return KeyValue.of(this, value == null ? KeyValue.NONE_VALUE : value.toString());
	}

	@Override
	public boolean isRequired() {
		return required;
	}

	@Override
	public String asString() {
		return name;
	}
}