/*
 * Copyright (c) 2010, 2023 BSI Business Systems Integration AG
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 */
import {
  aria, arrays, EventHandler, events, graphics, HtmlComponent, InitModelOf, KeyStrokeContext, Mode, ModeSelectorEventMap, ModeSelectorLayout, ModeSelectorLeftOrUpKeyStroke, ModeSelectorModel, ModeSelectorRightOrDownKeyStroke,
  ObjectOrChildModel, PropertyChangeEvent, SwipeCallbackEvent, Widget
} from '../index';

export class ModeSelector<TModeRef = any> extends Widget implements ModeSelectorModel<TModeRef> {
  declare model: ModeSelectorModel<TModeRef>;
  declare eventMap: ModeSelectorEventMap<TModeRef>;
  declare self: ModeSelector;

  modes: Mode<TModeRef>[];
  selectedMode: Mode<TModeRef>;
  $slider: JQuery;

  /**
   * When a new mode is set, the new one is marked as selected while the old one is deselected. This triggers the modePropertyChangeHandler.
   * In this case the handler must not react on the selection event. Otherwise, the value is first set to null (because the old is deselected) and then to the new value.
   * Setting a new mode should not trigger two change events.
   */
  protected _isModeChanging: boolean;
  protected _modePropertyChangeHandler: EventHandler<PropertyChangeEvent<any>>;

  constructor() {
    super();
    this._addWidgetProperties(['modes', 'selectedMode']);
    this._addPreserveOnPropertyChangeProperties(['selectedMode']);

    this.modes = [];
    this.selectedMode = null;
    this.$slider = null;

    this._isModeChanging = false;
    this._modePropertyChangeHandler = this._onModePropertyChange.bind(this);
  }

  protected override _init(model: InitModelOf<this>) {
    super._init(model);
    this._setModes(this.modes);
    this._setSelectedMode(this.selectedMode);
  }

  protected override _createKeyStrokeContext(): KeyStrokeContext {
    return new KeyStrokeContext();
  }

  protected override _initKeyStrokeContext() {
    super._initKeyStrokeContext();

    this.keyStrokeContext.registerKeyStrokes([
      new ModeSelectorLeftOrUpKeyStroke(this),
      new ModeSelectorRightOrDownKeyStroke(this)
    ]);
  }

  protected override _render() {
    this.$container = this.$parent.appendDiv('mode-selector');
    this.htmlComp = HtmlComponent.install(this.$container, this.session);
    this.htmlComp.setLayout(new ModeSelectorLayout(this));
  }

  protected override _renderProperties() {
    super._renderProperties();
    this._renderSlider();
    this._renderModes();
  }

  override recomputeEnabled(parentEnabled?: boolean) {
    super.recomputeEnabled(parentEnabled);
    this._provideTabIndex();
  }

  protected _provideTabIndex() {
    let tabSet;
    this.modes.forEach(mode => {
      if (mode.enabledComputed && !tabSet) {
        mode.setTabbable(true);
        tabSet = mode;
      } else if (tabSet && this.enabledComputed && mode.enabledComputed && mode.selected) {
        tabSet.setTabbable(false);
        mode.setTabbable(true);
        tabSet = mode;
      } else {
        mode.setTabbable(false);
      }
    }, this);
  }

  getTabbableMode(): Mode<TModeRef> {
    return arrays.find(this.modes, mode => {
      return mode.visible && mode.tabbable;
    });
  }

  override getFocusableElement(): HTMLElement | JQuery {
    // The first mode may not be focusable because it is not selected and therefore has no tab index -> find the first focusable button
    return this.session.focusManager.findFirstFocusableElement(this.$container);
  }

  setModes(modes: ObjectOrChildModel<Mode<TModeRef>>[]) {
    this.setProperty('modes', modes);
  }

  protected _setModes(modes: Mode<TModeRef>[]) {
    this.modes.forEach(mode => mode.off('propertyChange', this._modePropertyChangeHandler));
    this._setProperty('modes', arrays.ensure(modes));
    this.modes.forEach(mode => {
      mode.on('propertyChange', this._modePropertyChangeHandler);
      if (mode.selected) {
        this.setSelectedMode(mode);
      }
    });
  }

  protected _renderSlider() {
    this.$slider = this.$container.appendDiv('mode-slider');
    aria.role(this.$slider, 'radiogroup');
  }

  protected _renderModes() {
    this.modes.forEach(mode => {
      mode.render();
      this._registerDragHandlers(mode.$container);
    });
    this._updateMarkers();
  }

  setSelectedMode(selectedMode: Mode<TModeRef>) {
    this.setProperty('selectedMode', selectedMode);
  }

  protected _setSelectedMode(selectedMode: Mode<TModeRef>) {
    this._isModeChanging = true;
    if (this.selectedMode && this.selectedMode !== selectedMode) {
      this.selectedMode.setSelected(false);
    }
    if (selectedMode) {
      if (!selectedMode.selected) {
        selectedMode.setSelected(true);
      }
      let oldMode = this.getTabbableMode();
      let newModeNeedsFocus = false;
      if (oldMode) {
        // Only one mode in the group should have a tab index -> remove it from the current tabbable mode after the new mode is tabbable.
        // If that mode is focused the newly selected mode needs to gain the focus otherwise the focus would fall back to the body.
        newModeNeedsFocus = oldMode.isFocused();
      }
      selectedMode.setTabbable(true);
      if (newModeNeedsFocus) {
        selectedMode.focus();
      }
      if (oldMode && oldMode !== selectedMode) {
        oldMode.setTabbable(false);
      }
    }
    this._setProperty('selectedMode', selectedMode);
    this._isModeChanging = false;
    this._updateMarkers();
  }

  protected _onModePropertyChange(event: PropertyChangeEvent<any, Mode<TModeRef>>) {
    if (event.propertyName === 'selected' && !this._isModeChanging) {
      this.setSelectedMode(event.newValue ? event.source : null);
    } else if (event.propertyName === 'visible') {
      this._updateMarkers();
    } else if (event.propertyName === 'enabled') {
      this._updateSlider();
    }
  }

  protected _updateMarkers() {
    let visibleModes = [];
    let selectedModeIndex = -1;
    this.modes.forEach(mode => {
      if (mode.rendered) {
        mode.$container.removeClass('first last after-selected');
        if (mode.visible) {
          visibleModes.push(mode);
          if (mode.selected) {
            selectedModeIndex = visibleModes.length - 1;
          }
        }
      }
    });
    if (visibleModes.length) {
      visibleModes[0].$container.addClass('first');
      visibleModes[visibleModes.length - 1].$container.addClass('last');
      if (selectedModeIndex >= 0 && selectedModeIndex < (visibleModes.length - 1)) {
        visibleModes[selectedModeIndex + 1].$container.addClass('after-selected');
      }
    }
    this._updateSlider();
  }

  /** @internal */
  _updateSlider() {
    if (!this.$slider) {
      return;
    }
    let selectedModePosX = 0, selectedModeWidth = 0;
    if (this.selectedMode && this.selectedMode.$container) {
      selectedModePosX = graphics.position(this.selectedMode.$container).x;
      selectedModeWidth = graphics.size(this.selectedMode.$container, {exact: true}).width;
    }
    this.$slider.cssLeft(selectedModePosX);
    this.$slider.cssWidth(selectedModeWidth);
    this.$slider.setVisible(this.selectedMode && this.selectedMode.$container && this.selectedMode.enabled);
  }

  protected _registerDragHandlers($mode: JQuery) {
    let className = 'mode-selector-dragging';
    let onDown = (e: SwipeCallbackEvent) => this.enabledComputed && this.selectedMode && this.selectedMode.$container === $mode && this.modes.filter(m => m.isVisible() && m.enabled).length > 1;
    let onMove = (e: SwipeCallbackEvent) => {
      let maxX = this.$container.width() - $mode.outerWidth();
      let minX = 0;
      let newModeLeft = Math.max(Math.min(e.newLeft, maxX), minX); // limit to the size of the ModeSelector
      this.$container.children().addClass(className);
      if (newModeLeft !== e.originalLeft) {
        this.$slider.cssLeft(newModeLeft);
      }
      return newModeLeft;
    };
    let onUp = (e: SwipeCallbackEvent) => {
      this.$container.children().removeClass(className);
      let newSelectedMode = this._computeNewSelectedMode(e);
      if (!newSelectedMode || newSelectedMode === this.selectedMode || !newSelectedMode.enabled) {
        this._updateSlider(); // move back to original position
      } else {
        this.setSelectedMode(newSelectedMode); // updates the slider position
      }
    };
    events.onSwipe($mode, className, onDown, onMove, onUp);
  }

  protected _computeNewSelectedMode(e: SwipeCallbackEvent): Mode<TModeRef> {
    if (e.direction === 0 || Math.abs(e.deltaX) <= 5) {
      // ignore if the slide is below threshold
      return this.selectedMode;
    }
    if (e.direction < 0) {
      // slide left: use left end of slider
      return this._findModeByPos(e.newLeft);
    }
    // slide right: use right end of slider
    return this._findModeByPos(e.newLeft + this.$slider.width());
  }

  protected _findModeByPos(pos: number): Mode<TModeRef> {
    let visibleModes = this.modes.filter(m => m.visible);
    for (let i = visibleModes.length - 1; i >= 0; i--) {
      let mode = visibleModes[i];
      let modePosX = Math.floor(graphics.position(mode.$container).x);
      if (pos >= modePosX) {
        let modeWidth = graphics.size(mode.$container).width;
        let modeEndX = modePosX + modeWidth;
        if (pos <= modeEndX) {
          return mode;
        }
      }
    }
    return null;
  }

  findModeById(id: string): Mode<TModeRef> {
    return arrays.find(this.modes, mode => mode.id === id);
  }

  findModeByRef(ref: TModeRef): Mode<TModeRef> {
    return arrays.find(this.modes, mode => mode.ref === ref);
  }

  selectModeById(id: string) {
    this.setSelectedMode(this.findModeById(id));
  }

  selectModeByRef(ref: TModeRef) {
    this.setSelectedMode(this.findModeByRef(ref));
  }
}