/**
 * @module ol/layer/Group
 */
import BaseLayer from './Base.js';
import Collection from '../Collection.js';
import CollectionEventType from '../CollectionEventType.js';
import Event from '../events/Event.js';
import EventType from '../events/EventType.js';
import ObjectEventType from '../ObjectEventType.js';
import {assert} from '../asserts.js';
import {clear} from '../obj.js';
import {getIntersection} from '../extent.js';
import {getUid} from '../util.js';
import {listen, unlistenByKey} from '../events.js';

/**
 * @typedef {'addlayer'|'removelayer'} EventType
 */

/**
 * @classdesc
 * A layer group triggers 'addlayer' and 'removelayer' events when layers are added to or removed from
 * the group or one of its child groups.  When a layer group is added to or removed from another layer group,
 * a single event will be triggered (instead of one per layer in the group added or removed).
 */
export class GroupEvent extends Event {
  /**
   * @param {EventType} type The event type.
   * @param {BaseLayer} layer The layer.
   */
  constructor(type, layer) {
    super(type);

    /**
     * The added or removed layer.
     * @type {BaseLayer}
     * @api
     */
    this.layer = layer;
  }
}

/***
 * @template Return
 * @typedef {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default, Return> &
 *   import("../Observable").OnSignature<import("./Base").BaseLayerObjectEventTypes|
 *     'change:layers', import("../Object").ObjectEvent, Return> &
 *   import("../Observable").CombinedOnSignature<import("../Observable").EventTypes|import("./Base").BaseLayerObjectEventTypes|'change:layers', Return>} GroupOnSignature
 */

/**
 * @typedef {Object} Options
 * @property {number} [opacity=1] Opacity (0, 1).
 * @property {boolean} [visible=true] Visibility.
 * @property {import("../extent.js").Extent} [extent] The bounding extent for layer rendering.  The layer will not be
 * rendered outside of this extent.
 * @property {number} [zIndex] The z-index for layer rendering.  At rendering time, the layers
 * will be ordered, first by Z-index and then by position. When `undefined`, a `zIndex` of 0 is assumed
 * for layers that are added to the map's `layers` collection, or `Infinity` when the layer's `setMap()`
 * method was used.
 * @property {number} [minResolution] The minimum resolution (inclusive) at which this layer will be
 * visible.
 * @property {number} [maxResolution] The maximum resolution (exclusive) below which this layer will
 * be visible.
 * @property {number} [minZoom] The minimum view zoom level (exclusive) above which this layer will be
 * visible.
 * @property {number} [maxZoom] The maximum view zoom level (inclusive) at which this layer will
 * be visible.
 * @property {Array<import("./Base.js").default>|Collection<import("./Base.js").default>} [layers] Child layers.
 * @property {Object<string, *>} [properties] Arbitrary observable properties. Can be accessed with `#get()` and `#set()`.
 */

/**
 * @enum {string}
 * @private
 */
const Property = {
  LAYERS: 'layers',
};

/**
 * @classdesc
 * A {@link module:ol/Collection~Collection} of layers that are handled together.
 *
 * A generic `change` event is triggered when the group/Collection changes.
 *
 * @api
 */
class LayerGroup extends BaseLayer {
  /**
   * @param {Options} [options] Layer options.
   */
  constructor(options) {
    options = options || {};
    const baseOptions = /** @type {Options} */ (Object.assign({}, options));
    delete baseOptions.layers;

    let layers = options.layers;

    super(baseOptions);

    /***
     * @type {GroupOnSignature<import("../events").EventsKey>}
     */
    this.on;

    /***
     * @type {GroupOnSignature<import("../events").EventsKey>}
     */
    this.once;

    /***
     * @type {GroupOnSignature<void>}
     */
    this.un;

    /**
     * @private
     * @type {Array<import("../events.js").EventsKey>}
     */
    this.layersListenerKeys_ = [];

    /**
     * @private
     * @type {Object<string, Array<import("../events.js").EventsKey>>}
     */
    this.listenerKeys_ = {};

    this.addChangeListener(Property.LAYERS, this.handleLayersChanged_);

    if (layers) {
      if (Array.isArray(layers)) {
        layers = new Collection(layers.slice(), {unique: true});
      } else {
        assert(typeof (/** @type {?} */ (layers).getArray) === 'function', 43); // Expected `layers` to be an array or a `Collection`
      }
    } else {
      layers = new Collection(undefined, {unique: true});
    }

    this.setLayers(layers);
  }

  /**
   * @private
   */
  handleLayerChange_() {
    this.changed();
  }

  /**
   * @private
   */
  handleLayersChanged_() {
    this.layersListenerKeys_.forEach(unlistenByKey);
    this.layersListenerKeys_.length = 0;

    const layers = this.getLayers();
    this.layersListenerKeys_.push(
      listen(layers, CollectionEventType.ADD, this.handleLayersAdd_, this),
      listen(layers, CollectionEventType.REMOVE, this.handleLayersRemove_, this)
    );

    for (const id in this.listenerKeys_) {
      this.listenerKeys_[id].forEach(unlistenByKey);
    }
    clear(this.listenerKeys_);

    const layersArray = layers.getArray();
    for (let i = 0, ii = layersArray.length; i < ii; i++) {
      const layer = layersArray[i];
      this.registerLayerListeners_(layer);
      this.dispatchEvent(new GroupEvent('addlayer', layer));
    }
    this.changed();
  }

  /**
   * @param {BaseLayer} layer The layer.
   */
  registerLayerListeners_(layer) {
    const listenerKeys = [
      listen(
        layer,
        ObjectEventType.PROPERTYCHANGE,
        this.handleLayerChange_,
        this
      ),
      listen(layer, EventType.CHANGE, this.handleLayerChange_, this),
    ];

    if (layer instanceof LayerGroup) {
      listenerKeys.push(
        listen(layer, 'addlayer', this.handleLayerGroupAdd_, this),
        listen(layer, 'removelayer', this.handleLayerGroupRemove_, this)
      );
    }

    this.listenerKeys_[getUid(layer)] = listenerKeys;
  }

  /**
   * @param {GroupEvent} event The layer group event.
   */
  handleLayerGroupAdd_(event) {
    this.dispatchEvent(new GroupEvent('addlayer', event.layer));
  }

  /**
   * @param {GroupEvent} event The layer group event.
   */
  handleLayerGroupRemove_(event) {
    this.dispatchEvent(new GroupEvent('removelayer', event.layer));
  }

  /**
   * @param {import("../Collection.js").CollectionEvent<import("./Base.js").default>} collectionEvent CollectionEvent.
   * @private
   */
  handleLayersAdd_(collectionEvent) {
    const layer = collectionEvent.element;
    this.registerLayerListeners_(layer);
    this.dispatchEvent(new GroupEvent('addlayer', layer));
    this.changed();
  }

  /**
   * @param {import("../Collection.js").CollectionEvent<import("./Base.js").default>} collectionEvent CollectionEvent.
   * @private
   */
  handleLayersRemove_(collectionEvent) {
    const layer = collectionEvent.element;
    const key = getUid(layer);
    this.listenerKeys_[key].forEach(unlistenByKey);
    delete this.listenerKeys_[key];
    this.dispatchEvent(new GroupEvent('removelayer', layer));
    this.changed();
  }

  /**
   * Returns the {@link module:ol/Collection~Collection collection} of {@link module:ol/layer/Layer~Layer layers}
   * in this group.
   * @return {!Collection<import("./Base.js").default>} Collection of
   *   {@link module:ol/layer/Base~BaseLayer layers} that are part of this group.
   * @observable
   * @api
   */
  getLayers() {
    return /** @type {!Collection<import("./Base.js").default>} */ (
      this.get(Property.LAYERS)
    );
  }

  /**
   * Set the {@link module:ol/Collection~Collection collection} of {@link module:ol/layer/Layer~Layer layers}
   * in this group.
   * @param {!Collection<import("./Base.js").default>} layers Collection of
   *   {@link module:ol/layer/Base~BaseLayer layers} that are part of this group.
   * @observable
   * @api
   */
  setLayers(layers) {
    const collection = this.getLayers();
    if (collection) {
      const currentLayers = collection.getArray();
      for (let i = 0, ii = currentLayers.length; i < ii; ++i) {
        this.dispatchEvent(new GroupEvent('removelayer', currentLayers[i]));
      }
    }

    this.set(Property.LAYERS, layers);
  }

  /**
   * @param {Array<import("./Layer.js").default>} [array] Array of layers (to be modified in place).
   * @return {Array<import("./Layer.js").default>} Array of layers.
   */
  getLayersArray(array) {
    array = array !== undefined ? array : [];
    this.getLayers().forEach(function (layer) {
      layer.getLayersArray(array);
    });
    return array;
  }

  /**
   * Get the layer states list and use this groups z-index as the default
   * for all layers in this and nested groups, if it is unset at this point.
   * If dest is not provided and this group's z-index is undefined
   * 0 is used a the default z-index.
   * @param {Array<import("./Layer.js").State>} [dest] Optional list
   * of layer states (to be modified in place).
   * @return {Array<import("./Layer.js").State>} List of layer states.
   */
  getLayerStatesArray(dest) {
    const states = dest !== undefined ? dest : [];
    const pos = states.length;

    this.getLayers().forEach(function (layer) {
      layer.getLayerStatesArray(states);
    });

    const ownLayerState = this.getLayerState();
    let defaultZIndex = ownLayerState.zIndex;
    if (!dest && ownLayerState.zIndex === undefined) {
      defaultZIndex = 0;
    }
    for (let i = pos, ii = states.length; i < ii; i++) {
      const layerState = states[i];
      layerState.opacity *= ownLayerState.opacity;
      layerState.visible = layerState.visible && ownLayerState.visible;
      layerState.maxResolution = Math.min(
        layerState.maxResolution,
        ownLayerState.maxResolution
      );
      layerState.minResolution = Math.max(
        layerState.minResolution,
        ownLayerState.minResolution
      );
      layerState.minZoom = Math.max(layerState.minZoom, ownLayerState.minZoom);
      layerState.maxZoom = Math.min(layerState.maxZoom, ownLayerState.maxZoom);
      if (ownLayerState.extent !== undefined) {
        if (layerState.extent !== undefined) {
          layerState.extent = getIntersection(
            layerState.extent,
            ownLayerState.extent
          );
        } else {
          layerState.extent = ownLayerState.extent;
        }
      }
      if (layerState.zIndex === undefined) {
        layerState.zIndex = defaultZIndex;
      }
    }

    return states;
  }

  /**
   * @return {import("../source/Source.js").State} Source state.
   */
  getSourceState() {
    return 'ready';
  }
}

export default LayerGroup;