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 * SciJava Common shared library for SciJava software.
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package org.scijava.script;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

import javax.script.Bindings;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;

/**
 * Abstract base class for {@link AutoCompleter} implementations.
 * 
 * @author Hadrien Mary
 */
public abstract class AbstractAutoCompleter implements AutoCompleter {

	@SuppressWarnings("unused")
	private ScriptLanguage scriptLanguage;

	public AbstractAutoCompleter(final ScriptLanguage scriptLanguage) {
		this.scriptLanguage = scriptLanguage;
	}

	@Override
	public AutoCompletionResult autocomplete(final String code, final int index,
		final ScriptEngine engine)
	{

		final List<String> matches = new ArrayList<>();
		final int startIndex = 0;

		if (code.endsWith(".")) {
			// Autocompletion with all the attributes of the object
			matches.addAll(engineAttributesCompleter(code, index, engine));

		}
		else if (code.contains(".")) {
			final List<String> codeList = Arrays.asList(code.split("\\."));
			final String objectString = codeList.get(codeList.size() - 2);
			final String prefix = codeList.get(codeList.size() - 1);
			matches.addAll(engineAttributesCompleter(objectString + ".",
				prefix, index, engine));

		}
		else {
			// Autocompletion with variables in the engine scope
			matches.addAll(engineVariablesCompleter(code, index, engine));
		}

		// Remove duplicates
		final List<String> unique = //
			matches.stream().distinct().collect(Collectors.toList());

		// Sort alphabetically, ignoring case
		Collections.sort(unique, new Comparator<Object>() {

			@Override
			public int compare(final Object o1, final Object o2) {
				final String s1 = (String) o1;
				final String s2 = (String) o2;
				return s1.toLowerCase().compareTo(s2.toLowerCase());
			}
		});

		// Return results. For now we ignore index and startIndex.
		return new AutoCompletionResult(unique, startIndex);
	}

	private List<String> engineVariablesCompleter(final String code,
		@SuppressWarnings("unused") final int index, final ScriptEngine engine)
	{
		final List<String> matches = new ArrayList<>();

		final Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);

		for (final String key : bindings.keySet()) {
			if (key.toLowerCase().startsWith(code.toLowerCase())) {
				matches.add(key);
			}
		}
		return matches;

	}

	private List<String> engineAttributesCompleter(final String objectString,
		final int index, final ScriptEngine engine)
	{
		return engineAttributesCompleter(objectString, "", index, engine);
	}

	private List<String> engineAttributesCompleter(final String objectString,
		final String prefix, @SuppressWarnings("unused") final int index,
		final ScriptEngine engine)
	{
		final List<String> matches = new ArrayList<>();
		final String lPrefix = prefix.toLowerCase();

		final Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);

		for (final String key : bindings.keySet()) {
			if (objectString.endsWith(key + ".")) {
				final Object obj = bindings.get(key);
				// check for public field completions
				for (final Field field : obj.getClass().getFields()) {
					if (field.getName().toLowerCase().startsWith(lPrefix)) {
						matches.add(objectString + field.getName());
					}
				}
				// check for public method completions
				for (final Method method : obj.getClass().getMethods()) {
					if (method.getName().toLowerCase().startsWith(lPrefix)) {
						matches.add(objectString + method.getName() + "(");
					}
				}
			}
		}

		return matches;
	}
}
