/**
 * 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.List;
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.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSlider;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.ListModel;
import javax.swing.ListSelectionModel;

import org.unitConverter.UnitsDatabase;
import org.unitConverter.dimension.StandardDimensions;
import org.unitConverter.dimension.UnitDimension;
import org.unitConverter.unit.AbstractUnit;
import org.unitConverter.unit.NonlinearUnits;
import org.unitConverter.unit.SI;
import org.unitConverter.unit.Unit;
import org.unitConverter.unit.UnitPrefix;

/**
 * @author Adrien Hopkins
 * @since 2018-12-27
 * @since v0.1.0
 */
final class UnitConverterGUI {
	private static class Presenter {
		/** The presenter's associated view. */
		private final View view;

		/** The units known by the program. */
		private final UnitsDatabase units;

		/** The names of all of the units */
		private final List<String> unitNames;

		/** The names of all of the units, but filtered */
		private final DelegateListModel<String> unitNamesFiltered;

		/** The names of all of the prefixes */
		private final List<String> prefixNames;

		/** The names of all of the prefixes */
		private final DelegateListModel<String> prefixNamesFiltered;

		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.units = new UnitsDatabase();
			this.units.addUnit("metre", SI.METRE);
			this.units.addUnit("kilogram", SI.KILOGRAM);
			this.units.addUnit("gram", SI.KILOGRAM.dividedBy(1000));
			this.units.addUnit("second", SI.SECOND);
			this.units.addUnit("ampere", SI.AMPERE);
			this.units.addUnit("kelvin", SI.KELVIN);
			this.units.addUnit("mole", SI.MOLE);
			this.units.addUnit("candela", SI.CANDELA);
			this.units.addUnit("bit", SI.SI.getBaseUnit(StandardDimensions.INFORMATION));
			this.units.addUnit("unit", SI.SI.getBaseUnit(UnitDimension.EMPTY));
			// nonlinear units - must be loaded manually
			this.units.addUnit("tempCelsius", NonlinearUnits.CELSIUS);
			this.units.addUnit("tempFahrenheit", NonlinearUnits.FAHRENHEIT);

			this.units.addAllFromFile(new File("unitsfile.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.units.containsPrefixName(o1))
					return -1;
				else if (!Presenter.this.units.containsPrefixName(o2))
					return 1;

				final UnitPrefix p1 = Presenter.this.units.getPrefix(o1);
				final UnitPrefix p2 = Presenter.this.units.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.units.prefixlessUnitNameSet());
			this.unitNames.sort(null); // sorts it using Comparable

			this.unitNamesFiltered = new DelegateListModel<>(new ArrayList<>(this.units.prefixlessUnitNameSet()));
			this.unitNamesFiltered.sort(null); // sorts it using Comparable

			this.prefixNames = new ArrayList<>(this.units.prefixNameSet());
			this.prefixNames.sort(this.prefixNameComparator); // sorts it using my comparator

			this.prefixNamesFiltered = new DelegateListModel<>(new ArrayList<>(this.units.prefixNameSet()));
			this.prefixNamesFiltered.sort(this.prefixNameComparator); // sorts it using my comparator

			System.out.printf("Successfully loaded %d units (%d base units)", AbstractUnit.getUnitCount(),
					AbstractUnit.getBaseUnitCount());
		}

		/**
		 * 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 convert() {
			final String fromUnitString = this.view.getFromText();
			final String toUnitString = this.view.getToText();

			// try to parse from
			final Unit from;
			try {
				from = this.units.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 {
				to = this.units.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 = to.convertFromBase(from.convertToBase(1));

			// 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);
				}
			}

			this.view.setOutputText(String.format("%s = %s %s", fromUnitString, output, toUnitString));
		}

		/**
		 * Filters the filtered model for units
		 * 
		 * @param filter
		 *            filter to use
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		private final void filterFilteredPrefixModel(final Predicate<String> filter) {
			this.prefixNamesFiltered.clear();
			for (final String prefixName : this.prefixNames) {
				if (filter.test(prefixName)) {
					this.prefixNamesFiltered.add(prefixName);
				}
			}
		}

		/**
		 * Filters the filtered model for units
		 * 
		 * @param filter
		 *            filter to use
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		private final void filterFilteredUnitModel(final Predicate<String> filter) {
			this.unitNamesFiltered.clear();
			for (final String unitName : this.unitNames) {
				if (filter.test(unitName)) {
					this.unitNamesFiltered.add(unitName);
				}
			}
		}

		/**
		 * @return a list model of all of the unit keys
		 * @since 2019-01-14
		 * @since v0.1.0
		 */
		public final ListModel<String> keyListModel() {
			return this.unitNamesFiltered;
		}

		/**
		 * Runs whenever the prefix filter is changed.
		 * <p>
		 * Filters the prefix list then sorts it using a {@code FilterComparator}.
		 * </p>
		 * 
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void prefixFilterUpdated() {
			final String filter = this.view.getPrefixFilterText();
			if (filter.equals("")) {
				this.filterFilteredPrefixModel(t -> true);
			} else {
				this.filterFilteredPrefixModel(t -> t.contains(filter));
			}
			this.prefixNamesFiltered.sort(new FilterComparator(filter));
		}

		/**
		 * @return a list model of all of the prefix names
		 * @since 2019-01-15
		 */
		public final ListModel<String> prefixNameListModel() {
			return this.prefixNamesFiltered;
		}

		/**
		 * 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 int index = this.view.getPrefixListSelection();
			if (index == -1)
				return;
			else {
				final String prefixName = this.prefixNamesFiltered.get(index);
				final UnitPrefix prefix = this.units.getPrefix(prefixName);

				this.view.setPrefixTextBoxText(String.format("%s%nMultiplier: %s", prefixName, prefix.getMultiplier()));
			}
		}

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

		/**
		 * Runs whenever the unit filter is changed.
		 * <p>
		 * Filters the unit list then sorts it using a {@code FilterComparator}.
		 * </p>
		 * 
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public final void unitFilterUpdated() {
			final String filter = this.view.getUnitFilterText();
			if (filter.equals("")) {
				this.filterFilteredUnitModel(t -> true);
			} else {
				this.filterFilteredUnitModel(t -> t.contains(filter));
			}
			this.unitNamesFiltered.sort(new FilterComparator(filter));
		}

		/**
		 * 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 void unitNameSelected() {
			final int index = this.view.getUnitListSelection();
			if (index == -1)
				return;
			else {
				final String unitName = this.unitNamesFiltered.get(index);
				final Unit unit = this.units.getUnit(unitName);

				this.view.setUnitTextBoxText(unit.toString());
			}
		}
	}

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

		/** The list of unit names in the unit viewer */
		private final JList<String> unitNameList;
		/** The list of prefix names in the prefix viewer */
		private final JList<String> prefixNameList;
		/** The unit search box in the unit viewer */
		private final JTextField unitFilterEntry;
		/** The text box for unit data in the unit viewer */
		private final JTextArea unitTextBox;
		/** The prefix search box in the prefix viewer */
		private final JTextField prefixFilterEntry;
		/** The text box for prefix data in the prefix viewer */
		private final JTextArea prefixTextBox;
		/** 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;

		/**
		 * 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 JList<>(this.presenter.keyListModel());
			this.prefixNameList = new JList<>(this.presenter.prefixNameListModel());
			this.unitFilterEntry = new JTextField();
			this.unitTextBox = new JTextArea();
			this.prefixFilterEntry = new JTextField();
			this.prefixTextBox = new JTextArea();
			this.fromEntry = new JTextField();
			this.toEntry = new JTextField();
			this.output = new JTextArea(2, 32);

			// create more components
			this.initComponents();

			this.frame.pack();
		}

		/**
		 * @return text in "From" box in converter panel
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public String getFromText() {
			return this.fromEntry.getText();
		}

		/**
		 * @return text in prefix filter
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public String getPrefixFilterText() {
			return this.prefixFilterEntry.getText();
		}

		/**
		 * @return index of selected prefix
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public int getPrefixListSelection() {
			return this.prefixNameList.getSelectedIndex();
		}

		/**
		 * @return text in "To" box in converter panel
		 * @since 2019-01-26
		 * @since v0.1.0
		 */
		public String getToText() {
			return this.toEntry.getText();
		}

		/**
		 * @return text in unit filter
		 * @see javax.swing.text.JTextComponent#getText()
		 */
		public String getUnitFilterText() {
			return this.unitFilterEntry.getText();
		}

		/**
		 * @return index of selected unit
		 * @since 2019-01-15
		 * @since v0.1.0
		 */
		public int getUnitListSelection() {
			return this.unitNameList.getSelectedIndex();
		}

		/**
		 * 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));

						{ // panel for From things
							final JPanel fromPanel = new JPanel();
							inputPanel.add(fromPanel);

							fromPanel.setLayout(new BorderLayout());

							{ // search box for from
								final JTextField fromSearch = new JTextField("Search...");
								fromPanel.add(fromSearch, BorderLayout.PAGE_START);
							}

							{ // list for From units
								final JList<String> fromList = new JList<>();
								fromPanel.add(fromList, BorderLayout.CENTER);
							}
						}

						{ // for dimension selector and arrow that represents conversion
							final JPanel inBetweenPanel = new JPanel();
							inputPanel.add(inBetweenPanel);

							inBetweenPanel.setLayout(new BorderLayout());

							{ // dimension selector
								final JComboBox<String> dimensionSelector = new JComboBox<>(
										new String[] {"Select dimension..."});
								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
							final JPanel toPanel = new JPanel();
							inputPanel.add(toPanel);

							toPanel.setLayout(new BorderLayout());

							{ // search box for to
								final JTextField toSearch = new JTextField("Search...");
								toPanel.add(toSearch, BorderLayout.PAGE_START);
							}

							{ // list for To units
								final JList<String> toList = new JList<>();
								toPanel.add(toList, BorderLayout.CENTER);
							}
						}

					}

					{ // 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
								final JTextField valueInput = new JFormattedTextField(
										new DecimalFormat("###############0.################"));
								valueInputPanel.add(valueInput, BorderLayout.CENTER);
							}
						}

						{ // button to convert
							final JButton convertButton = new JButton("Convert");
							outputPanel.add(convertButton);
						}

						{ // output of conversion
							final JLabel outputLabel = new JLabel();
							outputPanel.add(outputLabel);
						}
					}
				}

				{ // 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.convert());
					}

					{ // 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());

					{ // panel for listing and searching
						final JPanel listPanel = new JPanel();
						unitLookupPanel.add(listPanel);

						listPanel.setLayout(new BorderLayout());

						{ // unit search box
							listPanel.add(this.unitFilterEntry, BorderLayout.PAGE_START);
							this.unitFilterEntry.addCaretListener(e -> this.presenter.unitFilterUpdated());
						}

						{ // a list of units
							listPanel.add(new JScrollPane(this.unitNameList), BorderLayout.CENTER);
							this.unitNameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); // temp
							this.unitNameList.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
						final JPanel prefixListPanel = new JPanel();
						prefixLookupPanel.add(prefixListPanel);

						prefixListPanel.setLayout(new BorderLayout());

						{ // prefix search box
							prefixListPanel.add(this.prefixFilterEntry, BorderLayout.PAGE_START);
							this.prefixFilterEntry.addCaretListener(e -> this.presenter.prefixFilterUpdated());
						}

						{ // a list of prefixes
							prefixListPanel.add(new JScrollPane(this.prefixNameList), BorderLayout.CENTER);
							this.prefixNameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); // temp
							this.prefixNameList.addListSelectionListener(e -> {
								this.presenter.prefixSelected();
							});
						}
					}

					{ // the text box for prefix's toString
						prefixLookupPanel.add(this.prefixTextBox);
						this.unitTextBox.setEditable(false);
					}
				}
			}
		}

		/**
		 * 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 setOutputText(final String text) {
			this.output.setText(text);
		}

		/**
		 * Sets the text of the prefix text box.
		 * 
		 * @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.
		 * 
		 * @param t
		 *            text to set
		 * @see javax.swing.text.JTextComponent#setText(java.lang.String)
		 */
		public void setUnitTextBoxText(final String t) {
			this.unitTextBox.setText(t);
		}

		/**
		 * 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();
	}
}