import L from "leaflet";
import BoundingSphere from "terriajs-cesium/Source/Core/BoundingSphere";
import EventHelper from "terriajs-cesium/Source/Core/EventHelper";
import JulianDate from "terriajs-cesium/Source/Core/JulianDate";
import createGuid from "terriajs-cesium/Source/Core/createGuid";
import destroyObject from "terriajs-cesium/Source/Core/destroyObject";
import BoundingSphereState from "terriajs-cesium/Source/DataSources/BoundingSphereState";
import CustomDataSource from "terriajs-cesium/Source/DataSources/CustomDataSource";
import DataSource from "terriajs-cesium/Source/DataSources/DataSource";
import DataSourceCollection from "terriajs-cesium/Source/DataSources/DataSourceCollection";
import Entity from "terriajs-cesium/Source/DataSources/Entity";
import EntityCluster from "terriajs-cesium/Source/DataSources/EntityCluster";
import isDefined from "../../Core/isDefined";
import LeafletScene from "./LeafletScene";

interface Visualizer {
  update(time: JulianDate): boolean;
  destroy(): void;
  getLatLngBounds(): L.LatLngBounds | undefined;
  getBoundingSphere?: (
    entity: Entity,
    tmp: BoundingSphere
  ) => BoundingSphereState;
}

class LeafletDataSource extends DataSource {
  visualizersByDisplayID?: { [index: string]: Visualizer[] };
  visualizers?: Visualizer[];
}

type VisualizersCallback = (
  scene: LeafletScene,
  entityCluster: EntityCluster | undefined,
  dataSource: DataSource
) => Visualizer[];

interface LeafletDataSourceDisplayOptions {
  scene: LeafletScene;
  dataSourceCollection: DataSourceCollection;
  visualizersCallback: VisualizersCallback;
}

/**
 * Visualizes a collection of {@link DataSource} instances in Leaflet.
 */
export default class LeafletDataSourceDisplay {
  private readonly _displayID: string;

  // Gets the scene associated with this display.
  private readonly _scene: LeafletScene;

  /**
   * Gets the default data source instance which can be used to
   * manually create and visualize entities not tied to
   * a specific data source. This instance is always available
   * and does not appear in the list dataSources collection.
   */
  private readonly _defaultDataSource: LeafletDataSource;

  // Gets the collection of data sources to display.
  private readonly _dataSourceCollection: DataSourceCollection;

  private readonly _visualizersCallback: VisualizersCallback;
  private readonly _eventHelper: EventHelper;

  // Gets a value indicating whether or not all entities in the data source are ready
  private _ready: boolean;

  private _lastTime: JulianDate;

  constructor(options: LeafletDataSourceDisplayOptions) {
    this._displayID = createGuid();
    this._scene = options.scene;
    this._dataSourceCollection = options.dataSourceCollection;
    this._visualizersCallback =
      options.visualizersCallback ??
      LeafletDataSourceDisplay.defaultVisualizersCallback;

    this._eventHelper = new EventHelper();
    this._eventHelper.add(
      this._dataSourceCollection.dataSourceAdded,
      this._onDataSourceAdded as () => void,
      this
    );
    this._eventHelper.add(
      this._dataSourceCollection.dataSourceRemoved,
      this._onDataSourceRemoved as () => void,
      this
    );

    for (let i = 0, len = this._dataSourceCollection.length; i < len; i++) {
      this._onDataSourceAdded(
        this._dataSourceCollection,
        this._dataSourceCollection.get(i)
      );
    }

    const defaultDataSource = new CustomDataSource();
    this._onDataSourceAdded(undefined, defaultDataSource);
    this._defaultDataSource = defaultDataSource;

    this._ready = false;
    this._lastTime = JulianDate.now();
  }

  /**
   * Gets or sets the default function which creates an array of visualizers used for visualization.
   * By default, this function uses all standard visualizers.
   *
   */
  static defaultVisualizersCallback(
    _leafletScene: LeafletScene,
    _entityCluster: EntityCluster,
    _dataSource: DataSource
  ) {
    return [];
  }

  /**
   * Updates the display to the provided time.
   *
   */
  update(time: JulianDate) {
    let result = true;

    let x;
    let visualizers;
    let vLength;
    const dataSources = this._dataSourceCollection;
    const length = dataSources.length;
    for (let i = 0; i < length; i++) {
      const dataSource = dataSources.get(i) as LeafletDataSource;
      if (isDefined(dataSource.update)) {
        result = dataSource.update(time) && result;
      }

      visualizers = this._getVisualizersForDataSource(dataSource);
      if (isDefined(visualizers)) {
        vLength = visualizers.length;
        for (x = 0; x < vLength; x++) {
          result = visualizers[x].update(time) && result;
        }
      }
    }

    visualizers = this._getVisualizersForDataSource(this._defaultDataSource);
    if (isDefined(visualizers)) {
      vLength = visualizers.length;
      for (x = 0; x < vLength; x++) {
        result = visualizers[x].update(time) && result;
      }
    }

    this._ready = result;
    this._lastTime = JulianDate.clone(time, this._lastTime);
    return result;
  }

  destroy() {
    this._eventHelper.removeAll();

    const dataSourceCollection = this._dataSourceCollection;
    for (let i = 0, length = dataSourceCollection.length; i < length; ++i) {
      this._onDataSourceRemoved(
        this._dataSourceCollection,
        dataSourceCollection.get(i)
      );
    }
    this._onDataSourceRemoved(undefined, this._defaultDataSource);
    return destroyObject(this);
  }

  private _onDataSourceAdded(
    _dataSourceCollection: DataSourceCollection | undefined,
    dataSource: LeafletDataSource
  ) {
    const visualizers = this._visualizersCallback(
      this._scene,
      undefined,
      dataSource
    );

    dataSource.visualizersByDisplayID = dataSource.visualizersByDisplayID || {};
    dataSource.visualizersByDisplayID[this._displayID] = visualizers;

    dataSource.visualizers = dataSource.visualizers || [];
    dataSource.visualizers = dataSource.visualizers.concat(visualizers);
  }

  private _onDataSourceRemoved(
    _dataSourceCollection: DataSourceCollection | undefined,
    dataSource: LeafletDataSource
  ) {
    const visualizers = this._getVisualizersForDataSource(dataSource);
    if (!isDefined(visualizers)) {
      return;
    }

    const length = visualizers.length;
    for (let i = 0; i < length; i++) {
      const visualizer = visualizers[i];
      visualizer.destroy();

      if (isDefined(dataSource.visualizers)) {
        const index = dataSource.visualizers.indexOf(visualizer);
        dataSource.visualizers.splice(index, 1);
      }
    }

    if (isDefined(dataSource.visualizersByDisplayID)) {
      delete dataSource.visualizersByDisplayID[this._displayID];
    }
  }

  private _getVisualizersForDataSource(dataSource: LeafletDataSource) {
    const visualizersByDisplayID = dataSource.visualizersByDisplayID;
    if (
      isDefined(visualizersByDisplayID) &&
      isDefined(visualizersByDisplayID[this._displayID])
    ) {
      return visualizersByDisplayID[this._displayID];
    }
  }

  /**
   * Computes the rectangular bounds which encloses the visualization
   * produced for the given entities.
   */
  getLatLngBounds(dataSource: LeafletDataSource) {
    this.update(this._lastTime);

    const visualizers = this._getVisualizersForDataSource(dataSource);
    if (!isDefined(visualizers)) {
      return;
    }

    let result;

    for (let j = 0, vLength = visualizers.length; j < vLength; j++) {
      const visualizer = visualizers[j];
      const bounds = visualizer.getLatLngBounds();
      if (bounds === undefined) {
        continue;
      }

      result =
        result === undefined
          ? L.latLngBounds(bounds.getSouthWest(), bounds.getNorthEast())
          : result.extend(bounds);
    }

    return result;
  }

  /**
   * Computes a bounding sphere which encloses the visualization produced for the specified entity.
   * The bounding sphere is in the fixed frame of the scene's globe.
   */
  getBoundingSphere(
    entity: Entity,
    allowPartial: boolean,
    result: BoundingSphere
  ) {
    if (!this._ready) {
      return BoundingSphereState.PENDING;
    }

    let length;
    let dataSource: LeafletDataSource | undefined = this._defaultDataSource;
    if (!dataSource.entities.contains(entity)) {
      dataSource = undefined;

      const dataSources = this._dataSourceCollection;
      length = dataSources.length;
      for (let i = 0; i < length; i++) {
        const d = dataSources.get(i);
        if (d.entities.contains(entity)) {
          dataSource = d;
          break;
        }
      }
    }

    if (!isDefined(dataSource) || !isDefined(dataSource.visualizers)) {
      return BoundingSphereState.FAILED;
    }

    const boundingSpheres: BoundingSphere[] = [];
    const tmp = new BoundingSphere();

    let count = 0;
    let state = BoundingSphereState.DONE;
    const visualizers = dataSource.visualizers;
    const visualizersLength = visualizers.length;

    for (let i = 0; i < visualizersLength; i++) {
      const visualizer = visualizers[i];
      if (isDefined(visualizer.getBoundingSphere)) {
        state = visualizer.getBoundingSphere(entity, tmp);
        if (!allowPartial && state === BoundingSphereState.PENDING) {
          return BoundingSphereState.PENDING;
        } else if (state === BoundingSphereState.DONE) {
          boundingSpheres[count] = BoundingSphere.clone(
            tmp,
            boundingSpheres[count]
          );
          count++;
        }
      }
    }

    if (count === 0) {
      return BoundingSphereState.FAILED;
    }

    boundingSpheres.length = count;
    BoundingSphere.fromBoundingSpheres(boundingSpheres, result);
    return BoundingSphereState.DONE;
  }
}