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package org.bndtools.templating.engine.mustache;

import com.github.mustachejava.Binding;
import com.github.mustachejava.Code;
import com.github.mustachejava.ObjectHandler;
import com.github.mustachejava.TemplateContext;
import com.github.mustachejava.reflect.BaseObjectHandler;
import com.github.mustachejava.util.Wrapper;

/**
 * A Mustache ObjectHandler that throws an error if a template parameter is
 * unbound.
 */
class CheckMissingObjectHandler extends BaseObjectHandler {
	private final ObjectHandler delegateHandler;

	CheckMissingObjectHandler(ObjectHandler delegateHandler) {
		this.delegateHandler = delegateHandler;
	}

	@Override
	public Wrapper find(final String name, Object[] scopes) {
		final Wrapper delegateWrapper = delegateHandler.find(name, scopes);
		return scopes1 -> {
			Object value = delegateWrapper.call(scopes1);
			// System.out.printf("Wrapper.call() [name=%s] -> %s%n", name,
			// value);
			if (value == null)
				throw new IllegalArgumentException(String.format("Missing value for %s", name));
			return value;
		};
	}

	@Override
	public Binding createBinding(final String name, TemplateContext context, Code code) {
		final Binding delegateBinding = delegateHandler.createBinding(name, context, code);
		return scopes -> {
			Object value = delegateBinding.get(scopes);
			// System.out.printf("Binding.get() [name=%s] -> %s%n", name,
			// value);
			if (value == null)
				throw new IllegalArgumentException(String.format("Missing value for %s", name));
			return value;
		};
	}
}