path: root/src/org/unitConverter/converterGUI/UnitConverterGUI.java

/**
 * Copyright (C) 2018-2021 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 org.unitConverter.converterGUI;

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import java.io.BufferedWriter;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;
import java.nio.file.Files;
import java.nio.file.Path;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JSlider;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.WindowConstants;
import javax.swing.border.TitledBorder;

import org.unitConverter.math.ConditionalExistenceCollections;
import org.unitConverter.math.ObjectProduct;
import org.unitConverter.unit.BaseDimension;
import org.unitConverter.unit.BritishImperial;
import org.unitConverter.unit.LinearUnit;
import org.unitConverter.unit.LinearUnitValue;
import org.unitConverter.unit.NameSymbol;
import org.unitConverter.unit.SI;
import org.unitConverter.unit.Unit;
import org.unitConverter.unit.UnitDatabase;
import org.unitConverter.unit.UnitPrefix;
import org.unitConverter.unit.UnitValue;

/**
 * @author Adrien Hopkins
 * @since 2018-12-27
 * @since v0.1.0
 */
final class UnitConverterGUI {
	/**
	 * A tab in the View.
	 */
	private enum Pane {
		UNIT_CONVERTER, EXPRESSION_CONVERTER, UNIT_VIEWER, PREFIX_VIEWER, ABOUT,
		SETTINGS;
	}
	
	private static class Presenter {
		/** The default place where settings are stored. */
		private static final String DEFAULT_SETTINGS_FILEPATH = "settings.txt";
		/** The default place where units are stored. */
		private static final Path DEFAULT_UNITS_FILE = Path.of("unitsfile.txt");
		/** The default place where dimensions are stored. */
		private static final Path DEFAULT_DIMENSION_FILE = Path
				.of("dimensionfile.txt");
		/** The default place where exceptions are stored. */
		private static final Path DEFAULT_EXCEPTIONS_FILE = Path
				.of("metric_exceptions.txt");
		
		/**
		 * Adds default units and dimensions to a database.
		 * 
		 * @param database database to add to
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		private static void addDefaults(final UnitDatabase database) {
			database.addUnit("metre", SI.METRE);
			database.addUnit("kilogram", SI.KILOGRAM);
			database.addUnit("gram", SI.KILOGRAM.dividedBy(1000));
			database.addUnit("second", SI.SECOND);
			database.addUnit("ampere", SI.AMPERE);
			database.addUnit("kelvin", SI.KELVIN);
			database.addUnit("mole", SI.MOLE);
			database.addUnit("candela", SI.CANDELA);
			database.addUnit("bit", SI.BIT);
			database.addUnit("unit", SI.ONE);
			// nonlinear units - must be loaded manually
			database.addUnit("tempCelsius", SI.CELSIUS);
			database.addUnit("tempFahrenheit", BritishImperial.FAHRENHEIT);
			
			// load initial dimensions
			database.addDimension("LENGTH", SI.Dimensions.LENGTH);
			database.addDimension("MASS", SI.Dimensions.MASS);
			database.addDimension("TIME", SI.Dimensions.TIME);
			database.addDimension("TEMPERATURE", SI.Dimensions.TEMPERATURE);
		}
		
		/**
		 * @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);
		}
		
		/** The presenter's associated view. */
		private final View view;
		
		/** The units known by the program. */
		private final UnitDatabase database;
		
		/** The names of all of the units */
		private final List<String> unitNames;
		
		/** The names of all of the prefixes */
		private final List<String> prefixNames;
		
		/** The names of all of the dimensions */
		private final List<String> dimensionNames;
		
		/** Unit names that are ignored by the metric-only/imperial-only filter */
		private final Set<String> metricExceptions;
		
		private final Comparator<String> prefixNameComparator;
		
		/** A boolean remembering whether or not one-way conversion is on */
		private boolean oneWay = true;
		
		/** The prefix rule */
		private DefaultPrefixRepetitionRule prefixRule = null;
		// conditions for existence of From and To entries
		// used for one-way conversion
		private final MutablePredicate<String> fromExistenceCondition = new MutablePredicate<>(
				s -> true);
		
		private final MutablePredicate<String> toExistenceCondition = new MutablePredicate<>(
				s -> true);
		
		/*
		 * Rounding-related settings. I am using my own system, and not
		 * MathContext, because MathContext does not support decimal place based
		 * or scientific rounding, only significant digit based rounding.
		 */
		private int precision = 6;
		
		private RoundingType roundingType = RoundingType.SIGNIFICANT_DIGITS;
		
		/**
		 * Creates the presenter.
		 * 
		 * @param view presenter's associated view
		 * @since 2018-12-27
		 * @since v0.1.0
		 */
		Presenter(final View view) {
			this.view = view;
			
			// load initial units
			this.database = new UnitDatabase(
					DefaultPrefixRepetitionRule.NO_RESTRICTION);
			Presenter.addDefaults(this.database);
			
			this.database.loadUnitsFile(DEFAULT_UNITS_FILE);
			this.database.loadDimensionFile(DEFAULT_DIMENSION_FILE);
			
			// load metric exceptions
			try {
				this.metricExceptions = Files.readAllLines(DEFAULT_EXCEPTIONS_FILE)
						.stream().map(Presenter::withoutComments)
						.filter(s -> !s.isBlank()).collect(Collectors.toSet());
			} catch (final IOException e) {
				throw new AssertionError("Loading of metric_exceptions.txt failed.",
						e);
			}
			
			// load settings - requires database to exist
			this.loadSettings();
			
			// a comparator that can be used to compare prefix names
			// any name that does not exist is less than a name that does.
			// otherwise, they are compared by value
			this.prefixNameComparator = (o1, o2) -> {
				if (!Presenter.this.database.containsPrefixName(o1))
					return -1;
				else if (!Presenter.this.database.containsPrefixName(o2))
					return 1;
				
				final UnitPrefix p1 = Presenter.this.database.getPrefix(o1);
				final UnitPrefix p2 = Presenter.this.database.getPrefix(o2);
				
				if (p1.getMultiplier() < p2.getMultiplier())
					return -1;
				else if (p1.getMultiplier() > p2.getMultiplier())
					return 1;
				
				return o1.compareTo(o2);
			};
			
			this.unitNames = new ArrayList<>(
					this.database.unitMapPrefixless().keySet());
			this.unitNames.sort(null); // sorts it using Comparable
			
			this.prefixNames = new ArrayList<>(this.database.prefixMap().keySet());
			this.prefixNames.sort(this.prefixNameComparator); // sorts it using my
																				// comparator
			
			this.dimensionNames = new DelegateListModel<>(
					new ArrayList<>(this.database.dimensionMap().keySet()));
			this.dimensionNames.sort(null); // sorts it using Comparable
			
			// a Predicate that returns true iff the argument is a full base unit
			final Predicate<Unit> isFullBase = unit -> unit instanceof LinearUnit
					&& ((LinearUnit) unit).isBase();
			
			// print out unit counts
			System.out.printf(
					"Successfully loaded %d units with %d unit names (%d base units).%n",
					new HashSet<>(this.database.unitMapPrefixless().values()).size(),
					this.database.unitMapPrefixless().size(),
					new HashSet<>(this.database.unitMapPrefixless().values())
							.stream().filter(isFullBase).count());
		}
		
		/**
		 * Converts in the dimension-based converter
		 * 
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public final void convertDimensionBased() {
			final String fromSelection = this.view.getFromSelection();
			if (fromSelection == null) {
				this.view.showErrorDialog("Error",
						"No unit selected in From field");
				return;
			}
			final String toSelection = this.view.getToSelection();
			if (toSelection == null) {
				this.view.showErrorDialog("Error", "No unit selected in To field");
				return;
			}
			
			final Unit from = this.database.getUnit(fromSelection);
			final Unit to = this.database.getUnit(toSelection)
					.withName(NameSymbol.ofName(toSelection));
			
			final UnitValue beforeValue;
			try {
				beforeValue = UnitValue.of(from,
						this.view.getDimensionConverterInput());
			} catch (final ParseException e) {
				this.view.showErrorDialog("Error",
						"Error in parsing: " + e.getMessage());
				return;
			}
			final UnitValue value = beforeValue.convertTo(to);
			
			final String output = this.getRoundedString(value);
			
			this.view.setDimensionConverterOutputText(
					String.format("%s = %s", beforeValue, output));
		}
		
		/**
		 * Runs whenever the convert button is pressed.
		 * 
		 * <p>
		 * Reads and parses a unit expression from the from and to boxes, then
		 * converts {@code from} to {@code to}. Any errors are shown in
		 * JOptionPanes.
		 * </p>
		 * 
		 * @since 2019-01-26
		 * @since v0.1.0
		 */
		public final void convertExpressions() {
			final String fromUnitString = this.view.getFromText();
			final String toUnitString = this.view.getToText();
			
			if (fromUnitString.isEmpty()) {
				this.view.showErrorDialog("Parse Error",
						"Please enter a unit expression in the From: box.");
				return;
			}
			if (toUnitString.isEmpty()) {
				this.view.showErrorDialog("Parse Error",
						"Please enter a unit expression in the To: box.");
				return;
			}
			
			final LinearUnitValue from;
			final Unit to;
			try {
				from = this.database.evaluateUnitExpression(fromUnitString);
			} catch (final IllegalArgumentException | NoSuchElementException e) {
				this.view.showErrorDialog("Parse Error",
						"Could not recognize text in From entry: " + e.getMessage());
				return;
			}
			try {
				to = this.database.getUnitFromExpression(toUnitString);
			} catch (final IllegalArgumentException | NoSuchElementException e) {
				this.view.showErrorDialog("Parse Error",
						"Could not recognize text in To entry: " + e.getMessage());
				return;
			}
			
			if (to instanceof LinearUnit) {
				// convert to LinearUnitValue
				final LinearUnitValue from2;
				final LinearUnit to2 = ((LinearUnit) to)
						.withName(NameSymbol.ofName(toUnitString));
				final boolean useSlash;
				
				if (from.canConvertTo(to2)) {
					from2 = from;
					useSlash = false;
				} else if (LinearUnitValue.ONE.dividedBy(from).canConvertTo(to2)) {
					from2 = LinearUnitValue.ONE.dividedBy(from);
					useSlash = true;
				} else {
					// if I can't convert, leave
					this.view.showErrorDialog("Conversion Error",
							String.format("Cannot convert between %s and %s",
									fromUnitString, toUnitString));
					return;
				}
				
				final LinearUnitValue converted = from2.convertTo(to2);
				this.view.setExpressionConverterOutputText((useSlash ? "1 / " : "")
						+ String.format("%s = %s", fromUnitString,
								this.getRoundedString(converted, false)));
				return;
			} else {
				// convert to UnitValue
				final UnitValue from2 = from.asUnitValue();
				if (from2.canConvertTo(to)) {
					final UnitValue converted = from2.convertTo(to);
					
					this.view
							.setExpressionConverterOutputText(String.format("%s = %s",
									fromUnitString, this.getRoundedString(converted)));
				} else {
					// if I can't convert, leave
					this.view.showErrorDialog("Conversion Error",
							String.format("Cannot convert between %s and %s",
									fromUnitString, toUnitString));
				}
			}
		}
		
		/**
		 * @return a list of all of the unit dimensions
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public final List<String> dimensionNameList() {
			return this.dimensionNames;
		}
		
		/**
		 * @return a list of all the entries in the dimension-based converter's
		 *         From box
		 * @since 2020-08-27
		 */
		public final Set<String> fromEntries() {
			return ConditionalExistenceCollections.conditionalExistenceSet(
					this.unitNameSet(), this.fromExistenceCondition);
		}
		
		/**
		 * @return a comparator to compare prefix names
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		public final Comparator<String> getPrefixNameComparator() {
			return this.prefixNameComparator;
		}
		
		/**
		 * Like {@link LinearUnitValue#toString(boolean)}, but obeys this unit
		 * converter's rounding settings.
		 * 
		 * @since 2020-08-04
		 */
		private final String getRoundedString(final LinearUnitValue value,
				boolean showUncertainty) {
			switch (this.roundingType) {
			case DECIMAL_PLACES:
			case SIGNIFICANT_DIGITS:
				return this.getRoundedString(value.asUnitValue());
			case SCIENTIFIC:
				return value.toString(showUncertainty);
			default:
				throw new AssertionError("Invalid switch condition.");
			}
		}
		
		/**
		 * Like {@link UnitValue#toString()}, but obeys this unit converter's
		 * rounding settings.
		 * 
		 * @since 2020-08-04
		 */
		private final String getRoundedString(final UnitValue value) {
			final BigDecimal unrounded = new BigDecimal(value.getValue());
			final BigDecimal rounded;
			int precision = this.precision;
			
			switch (this.roundingType) {
			case DECIMAL_PLACES:
				rounded = unrounded.setScale(precision, RoundingMode.HALF_EVEN);
				break;
			case SCIENTIFIC:
				precision = 12;
				//$FALL-THROUGH$
			case SIGNIFICANT_DIGITS:
				rounded = unrounded
						.round(new MathContext(precision, RoundingMode.HALF_EVEN));
				break;
			default:
				throw new AssertionError("Invalid switch condition.");
			}
			
			String output = rounded.toString();
			
			// remove trailing zeroes
			if (output.contains(".")) {
				while (output.endsWith("0")) {
					output = output.substring(0, output.length() - 1);
				}
				if (output.endsWith(".")) {
					output = output.substring(0, output.length() - 1);
				}
			}
			
			return output + " " + value.getUnit().getPrimaryName().get();
		}
		
		/**
		 * @return The file where settings are stored;
		 * @since 2020-12-11
		 */
		private final Path getSettingsFile() {
			return Path.of(DEFAULT_SETTINGS_FILEPATH);
		}
		
		/**
		 * Loads settings from the settings file.
		 * 
		 * @since 2021-02-17
		 */
		public final void loadSettings() {
			try {
				// read file line by line
				final int lineNum = 0;
				for (final String line : Files
						.readAllLines(this.getSettingsFile())) {
					final int equalsIndex = line.indexOf('=');
					if (equalsIndex == -1)
						throw new IllegalStateException(
								"Settings file is malformed at line " + lineNum);
					
					final String param = line.substring(0, equalsIndex);
					final String value = line.substring(equalsIndex + 1);
					
					switch (param) {
					// set manually to avoid the unnecessary saving of the non-manual
					// methods
					case "precision":
						this.precision = Integer.valueOf(value);
						break;
					case "rounding_type":
						this.roundingType = RoundingType.valueOf(value);
						break;
					case "prefix_rule":
						this.prefixRule = DefaultPrefixRepetitionRule.valueOf(value);
						this.database.setPrefixRepetitionRule(this.prefixRule);
						break;
					case "one_way":
						this.oneWay = Boolean.valueOf(value);
						if (this.oneWay) {
							this.fromExistenceCondition.setPredicate(
									unitName -> this.metricExceptions.contains(unitName)
											|| !this.database.getUnit(unitName)
													.isMetric());
							this.toExistenceCondition.setPredicate(
									unitName -> this.metricExceptions.contains(unitName)
											|| this.database.getUnit(unitName).isMetric());
						} else {
							this.fromExistenceCondition.setPredicate(unitName -> true);
							this.toExistenceCondition.setPredicate(unitName -> true);
						}
						break;
					default:
						System.err.printf("Warning: unrecognized setting \"%s\".",
								param);
						break;
					}
				}
			} catch (final IOException e) {}
		}
		
		/**
		 * @return a set of all prefix names in the database
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		public final Set<String> prefixNameSet() {
			return this.database.prefixMap().keySet();
		}
		
		/**
		 * Runs whenever a prefix is selected in the viewer.
		 * <p>
		 * Shows its information in the text box to the right.
		 * </p>
		 * 
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void prefixSelected() {
			final String prefixName = this.view.getPrefixViewerSelection();
			if (prefixName == null)
				return;
			else {
				final UnitPrefix prefix = this.database.getPrefix(prefixName);
				
				this.view.setPrefixTextBoxText(String.format("%s%nMultiplier: %s",
						prefixName, prefix.getMultiplier()));
			}
		}
		
		/**
		 * Saves the settings to the settings file.
		 *
		 * @since 2021-02-17
		 */
		public final void saveSettings() {
			try (BufferedWriter writer = Files
					.newBufferedWriter(this.getSettingsFile())) {
				writer.write(String.format("precision=%d\n", this.precision));
				writer.write(
						String.format("rounding_type=%s\n", this.roundingType));
				writer.write(String.format("prefix_rule=%s\n", this.prefixRule));
				writer.write(String.format("one_way=%s\n", this.oneWay));
			} catch (final IOException e) {
				e.printStackTrace();
				this.view.showErrorDialog("I/O Error",
						"Error occurred while saving settings: "
								+ e.getLocalizedMessage());
			}
		}
		
		/**
		 * Enables or disables one-way conversion.
		 * 
		 * @param oneWay whether one-way conversion should be on (true) or off
		 *               (false)
		 * @since 2020-08-27
		 */
		public final void setOneWay(boolean oneWay) {
			this.oneWay = oneWay;
			if (oneWay) {
				this.fromExistenceCondition.setPredicate(
						unitName -> this.metricExceptions.contains(unitName)
								|| !this.database.getUnit(unitName).isMetric());
				this.toExistenceCondition.setPredicate(
						unitName -> this.metricExceptions.contains(unitName)
								|| this.database.getUnit(unitName).isMetric());
			} else {
				this.fromExistenceCondition.setPredicate(unitName -> true);
				this.toExistenceCondition.setPredicate(unitName -> true);
			}
			
			this.saveSettings();
		}
		
		/**
		 * @param precision new value of precision
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void setPrecision(final int precision) {
			this.precision = precision;
			
			this.saveSettings();
		}
		
		/**
		 * @param prefixRepetitionRule the prefixRepetitionRule to set
		 * @since 2020-08-26
		 */
		public void setPrefixRepetitionRule(
				Predicate<List<UnitPrefix>> prefixRepetitionRule) {
			if (prefixRepetitionRule instanceof DefaultPrefixRepetitionRule) {
				this.prefixRule = (DefaultPrefixRepetitionRule) prefixRepetitionRule;
			} else {
				this.prefixRule = null;
			}
			this.database.setPrefixRepetitionRule(prefixRepetitionRule);
			
			this.saveSettings();
		}
		
		/**
		 * @param roundingType the roundingType to set
		 * @since 2020-07-16
		 */
		public final void setRoundingType(RoundingType roundingType) {
			this.roundingType = roundingType;
			
			this.saveSettings();
		}
		
		/**
		 * @return a list of all the entries in the dimension-based converter's To
		 *         box
		 * @since 2020-08-27
		 */
		public final Set<String> toEntries() {
			return ConditionalExistenceCollections.conditionalExistenceSet(
					this.unitNameSet(), this.toExistenceCondition);
		}
		
		/**
		 * 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
		 */
		public final boolean unitMatchesDimension(final String unitName,
				final String dimensionName) {
			final Unit unit = this.database.getUnit(unitName);
			final ObjectProduct<BaseDimension> dimension = this.database
					.getDimension(dimensionName);
			return unit.getDimension().equals(dimension);
		}
		
		/**
		 * Runs whenever a unit is selected in the viewer.
		 * <p>
		 * Shows its information in the text box to the right.
		 * </p>
		 * 
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void unitNameSelected() {
			final String unitName = this.view.getUnitViewerSelection();
			if (unitName == null)
				return;
			else {
				final Unit unit = this.database.getUnit(unitName);
				
				this.view.setUnitTextBoxText(unit.toString());
			}
		}
		
		/**
		 * @return a set of all of the unit names
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		private final Set<String> unitNameSet() {
			return this.database.unitMapPrefixless().keySet();
		}
	}
	
	/**
	 * Different types of rounding.
	 * 
	 * Significant digits: Rounds to a number of digits. i.e. with precision 5,
	 * 12345.6789 rounds to 12346. Decimal places: Rounds to a number of digits
	 * after the decimal point, i.e. with precision 5, 12345.6789 rounds to
	 * 12345.67890. Scientific: Rounds based on the number of digits and
	 * operations, following standard scientific rounding.
	 */
	private static enum RoundingType {
		SIGNIFICANT_DIGITS, DECIMAL_PLACES, SCIENTIFIC;
	}
	
	private static class View {
		private static final NumberFormat NUMBER_FORMATTER = new DecimalFormat();
		
		/** The view's frame. */
		private final JFrame frame;
		/** The view's associated presenter. */
		private final Presenter presenter;
		/** The master pane containing all of the tabs. */
		private final JTabbedPane masterPane;
		
		// DIMENSION-BASED CONVERTER
		/** The panel for inputting values in the dimension-based converter */
		private final JTextField valueInput;
		/** The panel for "From" in the dimension-based converter */
		private final SearchBoxList fromSearch;
		/** The panel for "To" in the dimension-based converter */
		private final SearchBoxList toSearch;
		/** The output area in the dimension-based converter */
		private final JTextArea dimensionBasedOutput;
		
		// EXPRESSION-BASED CONVERTER
		/** The "From" entry in the conversion panel */
		private final JTextField fromEntry;
		/** The "To" entry in the conversion panel */
		private final JTextField toEntry;
		/** The output area in the conversion panel */
		private final JTextArea output;
		
		// UNIT AND PREFIX VIEWERS
		/** The searchable list of unit names in the unit viewer */
		private final SearchBoxList unitNameList;
		/** The searchable list of prefix names in the prefix viewer */
		private final SearchBoxList prefixNameList;
		/** The text box for unit data in the unit viewer */
		private final JTextArea unitTextBox;
		/** The text box for prefix data in the prefix viewer */
		private final JTextArea prefixTextBox;
		
		/**
		 * Creates the {@code View}.
		 * 
		 * @since 2019-01-14
		 * @since v0.1.0
		 */
		public View() {
			this.presenter = new Presenter(this);
			this.frame = new JFrame("Unit Converter");
			this.frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
			
			// enable system look and feel
			try {
				UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
			} catch (ClassNotFoundException | InstantiationException
					| IllegalAccessException | UnsupportedLookAndFeelException e) {
				// oh well, just use default theme
				System.err.println("Failed to enable system look-and-feel.");
				e.printStackTrace();
			}
			
			// create the components
			this.masterPane = new JTabbedPane();
			this.unitNameList = new SearchBoxList(this.presenter.unitNameSet());
			this.prefixNameList = new SearchBoxList(this.presenter.prefixNameSet(),
					this.presenter.getPrefixNameComparator(), true);
			this.unitTextBox = new JTextArea();
			this.prefixTextBox = new JTextArea();
			this.fromSearch = new SearchBoxList(this.presenter.fromEntries());
			this.toSearch = new SearchBoxList(this.presenter.toEntries());
			this.valueInput = new JFormattedTextField(NUMBER_FORMATTER);
			this.dimensionBasedOutput = new JTextArea(2, 32);
			this.fromEntry = new JTextField();
			this.toEntry = new JTextField();
			this.output = new JTextArea(2, 32);
			
			// create more components
			this.initComponents();
			
			this.frame.pack();
		}
		
		/**
		 * @return the currently selected pane.
		 * @throws AssertionError if no pane (or an invalid pane) is selected
		 */
		public Pane getActivePane() {
			switch (this.masterPane.getSelectedIndex()) {
			case 0:
				return Pane.UNIT_CONVERTER;
			case 1:
				return Pane.EXPRESSION_CONVERTER;
			case 2:
				return Pane.UNIT_VIEWER;
			case 3:
				return Pane.PREFIX_VIEWER;
			case 4:
				return Pane.ABOUT;
			case 5:
				return Pane.SETTINGS;
			default:
				throw new AssertionError("No selected pane, or invalid pane.");
			}
		}
		
		/**
		 * @return value in dimension-based converter
		 * @throws ParseException
		 * @since 2020-07-07
		 */
		public double getDimensionConverterInput() throws ParseException {
			final Number value = NUMBER_FORMATTER.parse(this.valueInput.getText());
			if (value instanceof Double)
				return (double) value;
			else if (value instanceof Long)
				return ((Long) value).longValue();
			else
				throw new AssertionError();
		}
		
		/**
		 * @return selection in "From" selector in dimension-based converter
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public String getFromSelection() {
			return this.fromSearch.getSelectedValue();
		}
		
		/**
		 * @return text in "From" box in converter panel
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public String getFromText() {
			return this.fromEntry.getText();
		}
		
		/**
		 * @return index of selected prefix in prefix viewer
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public String getPrefixViewerSelection() {
			return this.prefixNameList.getSelectedValue();
		}
		
		/**
		 * @return selection in "To" selector in dimension-based converter
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public String getToSelection() {
			return this.toSearch.getSelectedValue();
		}
		
		/**
		 * @return text in "To" box in converter panel
		 * @since 2019-01-26
		 * @since v0.1.0
		 */
		public String getToText() {
			return this.toEntry.getText();
		}
		
		/**
		 * @return index of selected unit in unit viewer
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public String getUnitViewerSelection() {
			return this.unitNameList.getSelectedValue();
		}
		
		/**
		 * Starts up the application.
		 * 
		 * @since 2018-12-27
		 * @since v0.1.0
		 */
		public final void init() {
			this.frame.setVisible(true);
		}
		
		/**
		 * Initializes the view's components.
		 * 
		 * @since 2018-12-27
		 * @since v0.1.0
		 */
		private final void initComponents() {
			final JPanel masterPanel = new JPanel();
			this.frame.add(masterPanel);
			
			masterPanel.setLayout(new BorderLayout());
			
			{ // pane with all of the tabs
				masterPanel.add(this.masterPane, BorderLayout.CENTER);
				
				// update stuff
				this.masterPane.addChangeListener(e -> this.update());
				
				{ // a panel for unit conversion using a selector
					final JPanel convertUnitPanel = new JPanel();
					this.masterPane.addTab("Convert Units", convertUnitPanel);
					this.masterPane.setMnemonicAt(0, KeyEvent.VK_U);
					
					convertUnitPanel.setLayout(new BorderLayout());
					
					{ // panel for input part
						final JPanel inputPanel = new JPanel();
						convertUnitPanel.add(inputPanel, BorderLayout.CENTER);
						
						inputPanel.setLayout(new GridLayout(1, 3));
						
						final JComboBox<String> dimensionSelector = new JComboBox<>(
								this.presenter.dimensionNameList()
										.toArray(new String[0]));
						dimensionSelector.setSelectedItem("LENGTH");
						
						// handle dimension filter
						final MutablePredicate<String> dimensionFilter = new MutablePredicate<>(
								s -> true);
						
						// panel for From things
						inputPanel.add(this.fromSearch);
						
						this.fromSearch.addSearchFilter(dimensionFilter);
						
						{ // for dimension selector and arrow that represents
							// conversion
							final JPanel inBetweenPanel = new JPanel();
							inputPanel.add(inBetweenPanel);
							
							inBetweenPanel.setLayout(new BorderLayout());
							
							{ // dimension selector
								inBetweenPanel.add(dimensionSelector,
										BorderLayout.PAGE_START);
							}
							
							{ // the arrow in the middle
								final JLabel arrowLabel = new JLabel("->");
								inBetweenPanel.add(arrowLabel, BorderLayout.CENTER);
							}
						}
						
						// panel for To things
						
						inputPanel.add(this.toSearch);
						
						this.toSearch.addSearchFilter(dimensionFilter);
						
						// code for dimension filter
						dimensionSelector.addItemListener(e -> {
							dimensionFilter.setPredicate(string -> View.this.presenter
									.unitMatchesDimension(string,
											(String) dimensionSelector.getSelectedItem()));
							this.fromSearch.reapplyFilter();
							this.toSearch.reapplyFilter();
						});
						
						// apply the item listener once because I have a default
						// selection
						dimensionFilter.setPredicate(string -> View.this.presenter
								.unitMatchesDimension(string,
										(String) dimensionSelector.getSelectedItem()));
						this.fromSearch.reapplyFilter();
						this.toSearch.reapplyFilter();
					}
					
					{ // panel for submit and output, and also value entry
						final JPanel outputPanel = new JPanel();
						convertUnitPanel.add(outputPanel, BorderLayout.PAGE_END);
						
						outputPanel.setLayout(new GridLayout(3, 1));
						
						{ // unit input
							final JPanel valueInputPanel = new JPanel();
							outputPanel.add(valueInputPanel);
							
							valueInputPanel.setLayout(new BorderLayout());
							
							{ // prompt
								final JLabel valuePrompt = new JLabel(
										"Value to convert: ");
								valueInputPanel.add(valuePrompt,
										BorderLayout.LINE_START);
							}
							
							{ // value to convert
								valueInputPanel.add(this.valueInput,
										BorderLayout.CENTER);
							}
						}
						
						{ // button to convert
							final JButton convertButton = new JButton("Convert");
							outputPanel.add(convertButton);
							
							convertButton.addActionListener(
									e -> this.presenter.convertDimensionBased());
							convertButton.setMnemonic(KeyEvent.VK_ENTER);
						}
						
						{ // output of conversion
							outputPanel.add(this.dimensionBasedOutput);
							this.dimensionBasedOutput.setEditable(false);
						}
					}
				}
				
				{ // panel for unit conversion using expressions
					final JPanel convertExpressionPanel = new JPanel();
					this.masterPane.addTab("Convert Unit Expressions",
							convertExpressionPanel);
					this.masterPane.setMnemonicAt(1, KeyEvent.VK_E);
					
					convertExpressionPanel.setLayout(new GridLayout(4, 1));
					
					{ // panel for units to convert from
						final JPanel fromPanel = new JPanel();
						convertExpressionPanel.add(fromPanel);
						
						fromPanel.setBorder(BorderFactory.createTitledBorder("From"));
						fromPanel.setLayout(new GridLayout(1, 1));
						
						{ // entry for units
							fromPanel.add(this.fromEntry);
						}
					}
					
					{ // panel for units to convert to
						final JPanel toPanel = new JPanel();
						convertExpressionPanel.add(toPanel);
						
						toPanel.setBorder(BorderFactory.createTitledBorder("To"));
						toPanel.setLayout(new GridLayout(1, 1));
						
						{ // entry for units
							toPanel.add(this.toEntry);
						}
					}
					
					{ // button to convert
						final JButton convertButton = new JButton("Convert");
						convertExpressionPanel.add(convertButton);
						
						convertButton.addActionListener(
								e -> this.presenter.convertExpressions());
						convertButton.setMnemonic(KeyEvent.VK_ENTER);
					}
					
					{ // output of conversion
						final JPanel outputPanel = new JPanel();
						convertExpressionPanel.add(outputPanel);
						
						outputPanel
								.setBorder(BorderFactory.createTitledBorder("Output"));
						outputPanel.setLayout(new GridLayout(1, 1));
						
						{ // output
							outputPanel.add(this.output);
							this.output.setEditable(false);
						}
					}
				}
				
				{ // panel to look up units
					final JPanel unitLookupPanel = new JPanel();
					this.masterPane.addTab("Unit Viewer", unitLookupPanel);
					this.masterPane.setMnemonicAt(2, KeyEvent.VK_V);
					
					unitLookupPanel.setLayout(new GridLayout());
					
					{ // search panel
						unitLookupPanel.add(this.unitNameList);
						
						this.unitNameList.getSearchList().addListSelectionListener(
								e -> this.presenter.unitNameSelected());
					}
					
					{ // the text box for unit's toString
						unitLookupPanel.add(this.unitTextBox);
						this.unitTextBox.setEditable(false);
						this.unitTextBox.setLineWrap(true);
					}
				}
				
				{ // panel to look up prefixes
					final JPanel prefixLookupPanel = new JPanel();
					this.masterPane.addTab("Prefix Viewer", prefixLookupPanel);
					this.masterPane.setMnemonicAt(3, KeyEvent.VK_P);
					
					prefixLookupPanel.setLayout(new GridLayout(1, 2));
					
					{ // panel for listing and seaching
						prefixLookupPanel.add(this.prefixNameList);
						
						this.prefixNameList.getSearchList().addListSelectionListener(
								e -> this.presenter.prefixSelected());
					}
					
					{ // the text box for prefix's toString
						prefixLookupPanel.add(this.prefixTextBox);
						this.prefixTextBox.setEditable(false);
						this.prefixTextBox.setLineWrap(true);
					}
				}
				
				{ // Info panel
					final JPanel infoPanel = new JPanel();
					this.masterPane.addTab("\uD83D\uDEC8", // info (i) character
							new JScrollPane(infoPanel));
					
					final JTextArea infoTextArea = new JTextArea();
					infoTextArea.setEditable(false);
					infoTextArea.setOpaque(false);
					infoPanel.add(infoTextArea);
					
					// get info text
					final String infoText;
					try {
						final Path aboutFile = Path.of("src", "about.txt");
						infoText = Files.readAllLines(aboutFile).stream()
								.map(Presenter::withoutComments)
								.collect(Collectors.joining("\n"));
					} catch (final IOException e) {
						throw new AssertionError("I/O exception loading about.txt");
					}
					infoTextArea.setText(infoText);
				}
				
				{ // Settings panel
					final JPanel settingsPanel = new JPanel();
					this.masterPane.addTab("\u2699", new JScrollPane(settingsPanel));
					this.masterPane.setMnemonicAt(5, KeyEvent.VK_S);
					
					settingsPanel.setLayout(
							new BoxLayout(settingsPanel, BoxLayout.PAGE_AXIS));
					
					{ // rounding settings
						final JPanel roundingPanel = new JPanel();
						settingsPanel.add(roundingPanel);
						roundingPanel
								.setBorder(new TitledBorder("Rounding Settings"));
						roundingPanel.setLayout(new GridBagLayout());
						
						// rounding rule selection
						final ButtonGroup roundingRuleButtons = new ButtonGroup();
						
						final JLabel roundingRuleLabel = new JLabel("Rounding Rule:");
						roundingPanel.add(roundingRuleLabel, new GridBagBuilder(0, 0)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton fixedPrecision = new JRadioButton(
								"Fixed Precision");
						if (this.presenter.roundingType == RoundingType.SIGNIFICANT_DIGITS) {
							fixedPrecision.setSelected(true);
						}
						fixedPrecision.addActionListener(e -> this.presenter
								.setRoundingType(RoundingType.SIGNIFICANT_DIGITS));
						roundingRuleButtons.add(fixedPrecision);
						roundingPanel.add(fixedPrecision, new GridBagBuilder(0, 1)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton fixedDecimals = new JRadioButton(
								"Fixed Decimal Places");
						if (this.presenter.roundingType == RoundingType.DECIMAL_PLACES) {
							fixedDecimals.setSelected(true);
						}
						fixedDecimals.addActionListener(e -> this.presenter
								.setRoundingType(RoundingType.DECIMAL_PLACES));
						roundingRuleButtons.add(fixedDecimals);
						roundingPanel.add(fixedDecimals, new GridBagBuilder(0, 2)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton relativePrecision = new JRadioButton(
								"Scientific Precision");
						if (this.presenter.roundingType == RoundingType.SCIENTIFIC) {
							relativePrecision.setSelected(true);
						}
						relativePrecision.addActionListener(e -> this.presenter
								.setRoundingType(RoundingType.SCIENTIFIC));
						roundingRuleButtons.add(relativePrecision);
						roundingPanel.add(relativePrecision, new GridBagBuilder(0, 3)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JLabel sliderLabel = new JLabel("Precision:");
						roundingPanel.add(sliderLabel, new GridBagBuilder(0, 4)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JSlider sigDigSlider = new JSlider(0, 12);
						roundingPanel.add(sigDigSlider, new GridBagBuilder(0, 5)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						sigDigSlider.setMajorTickSpacing(4);
						sigDigSlider.setMinorTickSpacing(1);
						sigDigSlider.setSnapToTicks(true);
						sigDigSlider.setPaintTicks(true);
						sigDigSlider.setPaintLabels(true);
						sigDigSlider.setValue(this.presenter.precision);
						
						sigDigSlider.addChangeListener(e -> this.presenter
								.setPrecision(sigDigSlider.getValue()));
					}
					
					{ // prefix repetition settings
						final JPanel prefixRepetitionPanel = new JPanel();
						settingsPanel.add(prefixRepetitionPanel);
						prefixRepetitionPanel.setBorder(
								new TitledBorder("Prefix Repetition Settings"));
						prefixRepetitionPanel.setLayout(new GridBagLayout());
						
						// prefix rules
						final ButtonGroup prefixRuleButtons = new ButtonGroup();
						
						final JRadioButton noRepetition = new JRadioButton(
								"No Repetition");
						if (this.presenter.prefixRule == DefaultPrefixRepetitionRule.NO_REPETITION) {
							noRepetition.setSelected(true);
						}
						noRepetition.addActionListener(
								e -> this.presenter.setPrefixRepetitionRule(
										DefaultPrefixRepetitionRule.NO_REPETITION));
						prefixRuleButtons.add(noRepetition);
						prefixRepetitionPanel.add(noRepetition,
								new GridBagBuilder(0, 0)
										.setAnchor(GridBagConstraints.LINE_START)
										.build());
						
						final JRadioButton noRestriction = new JRadioButton(
								"No Restriction");
						if (this.presenter.prefixRule == DefaultPrefixRepetitionRule.NO_RESTRICTION) {
							noRestriction.setSelected(true);
						}
						noRestriction.addActionListener(
								e -> this.presenter.setPrefixRepetitionRule(
										DefaultPrefixRepetitionRule.NO_RESTRICTION));
						prefixRuleButtons.add(noRestriction);
						prefixRepetitionPanel.add(noRestriction,
								new GridBagBuilder(0, 1)
										.setAnchor(GridBagConstraints.LINE_START)
										.build());
						
						final JRadioButton customRepetition = new JRadioButton(
								"Complex Repetition");
						if (this.presenter.prefixRule == DefaultPrefixRepetitionRule.COMPLEX_REPETITION) {
							customRepetition.setSelected(true);
						}
						customRepetition.addActionListener(
								e -> this.presenter.setPrefixRepetitionRule(
										DefaultPrefixRepetitionRule.COMPLEX_REPETITION));
						prefixRuleButtons.add(customRepetition);
						prefixRepetitionPanel.add(customRepetition,
								new GridBagBuilder(0, 2)
										.setAnchor(GridBagConstraints.LINE_START)
										.build());
					}
					
					{ // search settings
						final JPanel searchingPanel = new JPanel();
						settingsPanel.add(searchingPanel);
						searchingPanel.setBorder(new TitledBorder("Search Settings"));
						searchingPanel.setLayout(new GridBagLayout());
						
						// searching rules
						final ButtonGroup searchRuleButtons = new ButtonGroup();
						
						final JRadioButton noPrefixes = new JRadioButton(
								"Never Include Prefixed Units");
						noPrefixes.setEnabled(false);
						searchRuleButtons.add(noPrefixes);
						searchingPanel.add(noPrefixes, new GridBagBuilder(0, 0)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton fixedPrefixes = new JRadioButton(
								"Include Some Prefixes");
						fixedPrefixes.setEnabled(false);
						searchRuleButtons.add(fixedPrefixes);
						searchingPanel.add(fixedPrefixes, new GridBagBuilder(0, 1)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton explicitPrefixes = new JRadioButton(
								"Include Explicit Prefixes");
						explicitPrefixes.setEnabled(false);
						searchRuleButtons.add(explicitPrefixes);
						searchingPanel.add(explicitPrefixes, new GridBagBuilder(0, 2)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JRadioButton alwaysInclude = new JRadioButton(
								"Include All Single Prefixes");
						alwaysInclude.setEnabled(false);
						searchRuleButtons.add(alwaysInclude);
						searchingPanel.add(alwaysInclude, new GridBagBuilder(0, 3)
								.setAnchor(GridBagConstraints.LINE_START).build());
					}
					
					{ // miscellaneous settings
						final JPanel miscPanel = new JPanel();
						settingsPanel.add(miscPanel);
						miscPanel
								.setBorder(new TitledBorder("Miscellaneous Settings"));
						miscPanel.setLayout(new GridBagLayout());
						
						final JCheckBox oneWay = new JCheckBox(
								"Convert One Way Only");
						oneWay.setSelected(this.presenter.oneWay);
						oneWay.addItemListener(
								e -> this.presenter.setOneWay(e.getStateChange() == 1));
						miscPanel.add(oneWay, new GridBagBuilder(0, 0)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JCheckBox showAllVariations = new JCheckBox(
								"Show Symbols in \"Convert Units\"");
						showAllVariations.setSelected(true);
						showAllVariations.setEnabled(false);
						miscPanel.add(showAllVariations, new GridBagBuilder(0, 1)
								.setAnchor(GridBagConstraints.LINE_START).build());
						
						final JButton unitFileButton = new JButton(
								"Manage Unit Data Files");
						unitFileButton.setEnabled(false);
						miscPanel.add(unitFileButton, new GridBagBuilder(0, 2)
								.setAnchor(GridBagConstraints.LINE_START).build());
					}
				}
			}
		}
		
		/**
		 * Sets the text in the output of the dimension-based converter.
		 * 
		 * @param text text to set
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public void setDimensionConverterOutputText(final String text) {
			this.dimensionBasedOutput.setText(text);
		}
		
		/**
		 * Sets the text in the output of the conversion panel.
		 * 
		 * @param text text to set
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public void setExpressionConverterOutputText(final String text) {
			this.output.setText(text);
		}
		
		/**
		 * Sets the text of the prefix text box in the prefix viewer.
		 * 
		 * @param text text to set
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public void setPrefixTextBoxText(final String text) {
			this.prefixTextBox.setText(text);
		}
		
		/**
		 * Sets the text of the unit text box in the unit viewer.
		 * 
		 * @param text text to set
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public void setUnitTextBoxText(final String text) {
			this.unitTextBox.setText(text);
		}
		
		/**
		 * Shows an error dialog.
		 * 
		 * @param title   title of dialog
		 * @param message message in dialog
		 * @since 2019-01-14
		 * @since v0.1.0
		 */
		public void showErrorDialog(final String title, final String message) {
			JOptionPane.showMessageDialog(this.frame, message, title,
					JOptionPane.ERROR_MESSAGE);
		}
		
		public void update() {
			switch (this.getActivePane()) {
			case UNIT_CONVERTER:
				this.fromSearch.updateList();
				this.toSearch.updateList();
				break;
			default:
				// do nothing, for now
				break;
			}
		}
	}
	
	public static void main(final String[] args) {
		new View().init();
	}
}