/**
 * Copyright (C) 2021 Adrien Hopkins
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package sevenUnitsGUI;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import sevenUnits.ProgramInfo;
import sevenUnits.unit.BaseDimension;
import sevenUnits.unit.Unit;
import sevenUnits.unit.UnitDatabase;
import sevenUnits.unit.UnitPrefix;
import sevenUnits.utils.ObjectProduct;
import sevenUnits.utils.UncertainDouble;

/**
 * An object that handles interactions between the view and the backend code
 * 
 * @author Adrien Hopkins
 * @since 2021-12-15
 */
public final class Presenter {
	/**
	 * @return text in About file
	 * @since 2022-02-19
	 */
	static final String getAboutText() {
		return Presenter.getLinesFromResource("/about.txt").stream()
				.map(Presenter::withoutComments).collect(Collectors.joining("\n"))
				.replaceAll("\\[VERSION\\]", ProgramInfo.VERSION.toString());
	}
	
	/**
	 * Gets the text of a resource file as a set of strings (each one is one line
	 * of the text).
	 *
	 * @param filename filename to get resource from
	 * @return contents of file
	 * @since 2021-03-27
	 */
	private static final List<String> getLinesFromResource(String filename) {
		final List<String> lines = new ArrayList<>();
		
		try (InputStream stream = inputStream(filename);
				Scanner scanner = new Scanner(stream)) {
			while (scanner.hasNextLine()) {
				lines.add(scanner.nextLine());
			}
		} catch (final IOException e) {
			throw new AssertionError(
					"Error occurred while loading file " + filename, e);
		}
		
		return lines;
	}
	
	/**
	 * Gets an input stream for a resource file.
	 *
	 * @param filepath file to use as resource
	 * @return obtained Path
	 * @since 2021-03-27
	 */
	private static final InputStream inputStream(String filepath) {
		return Presenter.class.getResourceAsStream(filepath);
	}
	
	/**
	 * @return {@code line} with any comments removed.
	 * @since 2021-03-13
	 */
	private static final String withoutComments(String line) {
		final int index = line.indexOf('#');
		return index == -1 ? line : line.substring(index);
	}
	
	// ====== SETTINGS ======
	
	/**
	 * The view that this presenter communicates with
	 */
	private final View view;
	
	/**
	 * The database that this presenter communicates with (effectively the model)
	 */
	private final UnitDatabase database;
	
	/**
	 * The rule used for parsing input numbers. Any number-string inputted into
	 * this program will be parsed using this method.
	 */
	private Function<String, UncertainDouble> numberParsingRule;
	
	/**
	 * The rule used for displaying the results of unit conversions. The result
	 * of unit conversions will be put into this function, and the resulting
	 * string will be used in the output.
	 */
	private Function<UncertainDouble, String> numberDisplayRule;
	
	/**
	 * A predicate that determines whether or not a certain combination of
	 * prefixes is allowed. If it returns false, a combination of prefixes will
	 * not be allowed. Prefixes are put in the list from right to left.
	 */
	private Predicate<List<UnitPrefix>> prefixRepetitionRule;
	
	/**
	 * If this is true, views that show units as a list will have metric units
	 * removed from the From unit list and imperial/USC units removed from the To
	 * unit list.
	 */
	private boolean oneWayConversion;
	
	/**
	 * If this is false, duplicate units will be removed from the unit view in
	 * views that show units as a list to choose from.
	 */
	private boolean showDuplicateUnits;
	
	/**
	 * Creates a Presenter
	 * 
	 * @param view the view that this presenter communicates with
	 * @since 2021-12-15
	 */
	public Presenter(View view) {
		this.view = view;
		this.database = new UnitDatabase();
	}
	
	/**
	 * Sets the dimension of the view's From and To units.
	 * 
	 * @throws UnsupportedOperationException if the view does not support
	 *                                       unit-based conversion (does not
	 *                                       implement
	 *                                       {@link UnitConversionView})
	 * @since 2021-12-15
	 */
	public void applyDimensionFilter() {}
	
	/**
	 * Gets settings from the view and applies them to both view and presenter.
	 * 
	 * @since 2021-12-15
	 */
	public void applySettings() {}
	
	/**
	 * Converts from the view's input expression to its output expression.
	 * Displays an error message if any of the required fields are invalid.
	 * 
	 * @throws UnsupportedOperationException if the view does not support
	 *                                       expression-based conversion (does
	 *                                       not implement
	 *                                       {@link ExpressionConversionView})
	 * @since 2021-12-15
	 */
	public void convertExpressions() {}
	
	/**
	 * Converts from the view's input unit to its output unit. Displays an error
	 * message if any of the required fields are invalid.
	 * 
	 * @throws UnsupportedOperationException if the view does not support
	 *                                       unit-based conversion (does not
	 *                                       implement
	 *                                       {@link UnitConversionView})
	 * @since 2021-12-15
	 */
	public void convertUnits() {}
	
	/**
	 * Loads settings from the user's settings file and applies them to the view.
	 * 
	 * @since 2021-12-15
	 */
	public void loadSettings() {}
	
	void prefixSelected() {}
	
	/**
	 * Gets user settings from the view then saves them to the user's settings
	 * file.
	 * 
	 * @since 2021-12-15
	 */
	public void saveSettings() {}
	
	/**
	 * Returns true if and only if the unit represented by {@code unitName} has
	 * the dimension represented by {@code dimensionName}.
	 * 
	 * @param unitName      name of unit to test
	 * @param dimensionName name of dimension to test
	 * @return whether unit has dimenision
	 * @since 2019-04-13
	 * @since v0.2.0
	 */
	boolean unitMatchesDimension(String unitName, String dimensionName) {
		final Unit unit = this.database.getUnit(unitName);
		final ObjectProduct<BaseDimension> dimension = this.database
				.getDimension(dimensionName);
		return unit.getDimension().equals(dimension);
	}
	
	void unitNameSelected() {}
}