/**
 * Copyright (C) 2018 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.GridLayout;
import java.io.File;
import java.math.BigDecimal;
import java.math.MathContext;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Predicate;

import javax.swing.BorderFactory;
import javax.swing.JButton;
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.JSlider;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

import org.unitConverter.math.ObjectProduct;
import org.unitConverter.unit.BaseDimension;
import org.unitConverter.unit.LinearUnit;
import org.unitConverter.unit.SI;
import org.unitConverter.unit.Unit;
import org.unitConverter.unit.UnitDatabase;
import org.unitConverter.unit.UnitPrefix;

/**
 * @author Adrien Hopkins
 * @since 2018-12-27
 * @since v0.1.0
 */
final class UnitConverterGUI {
	private static class Presenter {
		/**
		 * 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", NonlinearUnits.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);
		}

		/** 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;

		private final Comparator<String> prefixNameComparator;

		private int significantFigures = 6;

		/**
		 * 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();
			Presenter.addDefaults(this.database);

			this.database.loadUnitsFile(new File("unitsfile.txt"));
			this.database.loadDimensionFile(new File("dimensionfile.txt"));

			// 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);

			final String input = this.view.getDimensionConverterInput();
			if (input.equals("")) {
				this.view.showErrorDialog("Error", "No value to convert entered.");
				return;
			}
			final double beforeValue = Double.parseDouble(input);
			final double value = from.convertTo(to, beforeValue);

			final String output = this.getRoundedString(value);

			this.view.setDimensionConverterOutputText(
					String.format("%s %s = %s %s", input, fromSelection, output, toSelection));
		}

		/**
		 * 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;
			}

			// try to parse from
			final Unit from;
			try {
				from = this.database.getUnitFromExpression(fromUnitString);
			} catch (final IllegalArgumentException e) {
				this.view.showErrorDialog("Parse Error", "Could not recognize text in From entry: " + e.getMessage());
				return;
			}

			final double value;
			// try to parse to
			final Unit to;
			try {
				if (this.database.containsUnitName(toUnitString)) {
					// if it's a unit, convert to that
					to = this.database.getUnit(toUnitString);
				} else {
					to = this.database.getUnitFromExpression(toUnitString);
				}
			} catch (final IllegalArgumentException e) {
				this.view.showErrorDialog("Parse Error", "Could not recognize text in To entry: " + e.getMessage());
				return;
			}

			// if I can't convert, leave
			if (!from.canConvertTo(to)) {
				this.view.showErrorDialog("Conversion Error",
						String.format("Cannot convert between %s and %s", fromUnitString, toUnitString));
				return;
			}

			value = from.convertTo(to, 1);

			// round value
			final String output = this.getRoundedString(value);

			this.view.setExpressionConverterOutputText(
					String.format("%s = %s %s", fromUnitString, output, 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 comparator to compare prefix names
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		public final Comparator<String> getPrefixNameComparator() {
			return this.prefixNameComparator;
		}

		/**
		 * @param value
		 *            value to round
		 * @return string of that value rounded to {@code significantDigits} significant digits.
		 * @since 2019-04-14
		 * @since v0.2.0
		 */
		private final String getRoundedString(final double value) {
			// round value
			final BigDecimal bigValue = new BigDecimal(value).round(new MathContext(this.significantFigures));
			String output = bigValue.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;
		}

		/**
		 * @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()));
			}
		}

		/**
		 * @param significantFigures
		 *            new value of significantFigures
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void setSignificantFigures(final int significantFigures) {
			this.significantFigures = significantFigures;
		}

		/**
		 * 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
		 */
		public final Set<String> unitNameSet() {
			return this.database.unitMapPrefixless().keySet();
		}
	}

	private static class View {
		/** The view's frame. */
		private final JFrame frame;
		/** The view's associated presenter. */
		private final Presenter presenter;

		// 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(JFrame.EXIT_ON_CLOSE);

			// create the components
			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.unitNameSet());
			this.toSearch = new SearchBoxList(this.presenter.unitNameSet());
			this.valueInput = new JFormattedTextField(new DecimalFormat("###############0.################"));
			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 value in dimension-based converter
		 * @since 2019-04-13
		 * @since v0.2.0
		 */
		public String getDimensionConverterInput() {
			return this.valueInput.getText();
		}

		/**
		 * @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
				final JTabbedPane masterPane = new JTabbedPane();
				masterPanel.add(masterPane, BorderLayout.CENTER);

				{ // a panel for unit conversion using a selector
					final JPanel convertUnitPanel = new JPanel();
					masterPane.addTab("Convert Units", convertUnitPanel);

					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());
						}

						{ // output of conversion
							outputPanel.add(this.dimensionBasedOutput);
							this.dimensionBasedOutput.setEditable(false);
						}
					}
				}

				{ // panel for unit conversion using expressions
					final JPanel convertExpressionPanel = new JPanel();
					masterPane.addTab("Convert Unit Expressions", convertExpressionPanel);

					convertExpressionPanel.setLayout(new GridLayout(5, 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());
					}

					{ // 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 for specifying precision
						final JPanel sigDigPanel = new JPanel();
						convertExpressionPanel.add(sigDigPanel);

						sigDigPanel.setBorder(BorderFactory.createTitledBorder("Significant Digits"));

						{ // slider
							final JSlider sigDigSlider = new JSlider(0, 12);
							sigDigPanel.add(sigDigSlider);

							sigDigSlider.setMajorTickSpacing(4);
							sigDigSlider.setMinorTickSpacing(1);
							sigDigSlider.setSnapToTicks(true);
							sigDigSlider.setPaintTicks(true);
							sigDigSlider.setPaintLabels(true);

							sigDigSlider.addChangeListener(
									e -> this.presenter.setSignificantFigures(sigDigSlider.getValue()));
						}
					}
				}

				{ // panel to look up units
					final JPanel unitLookupPanel = new JPanel();
					masterPane.addTab("Unit Viewer", unitLookupPanel);

					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();
					masterPane.addTab("Prefix Viewer", prefixLookupPanel);

					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);
					}
				}
			}
		}

		/**
		 * 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 static void main(final String[] args) {
		new View().init();
	}
}