/**
 * @module ol/source/Source
 */

import {VOID} from '../functions.js';
import BaseObject from '../Object.js';
import {get as getProjection} from '../proj.js';
import SourceState from '../source/State.js';


/**
 * A function that returns a string or an array of strings representing source
 * attributions.
 *
 * @typedef {function(module:ol/PluggableMap~FrameState): (string|Array<string>)} Attribution
 */


/**
 * A type that can be used to provide attribution information for data sources.
 *
 * It represents either
 * * a simple string (e.g. `'© Acme Inc.'`)
 * * an array of simple strings (e.g. `['© Acme Inc.', '© Bacme Inc.']`)
 * * a function that returns a string or array of strings (`{@link module:ol/source/Source~Attribution}`)
 *
 * @typedef {string|Array<string>|module:ol/source/Source~Attribution} AttributionLike
 */


/**
 * @typedef {Object} Options
 * @property {module:ol/source/Source~AttributionLike} [attributions]
 * @property {module:ol/proj~ProjectionLike} projection
 * @property {module:ol/source/State} [state]
 * @property {boolean} [wrapX]
 */


/**
 * @classdesc
 * Abstract base class; normally only used for creating subclasses and not
 * instantiated in apps.
 * Base class for {@link module:ol/layer/Layer~Layer} sources.
 *
 * A generic `change` event is triggered when the state of the source changes.
 * @api
 */
class Source extends BaseObject {
  /**
   * @param {module:ol/source/Source~Options} options Source options.
   */
  constructor(options) {

    super();

    /**
    * @private
    * @type {module:ol/proj/Projection}
    */
    this.projection_ = getProjection(options.projection);

    /**
    * @private
    * @type {?module:ol/source/Source~Attribution}
    */
    this.attributions_ = this.adaptAttributions_(options.attributions);

    /**
    * @private
    * @type {module:ol/source/State}
    */
    this.state_ = options.state !== undefined ?
      options.state : SourceState.READY;

    /**
    * @private
    * @type {boolean}
    */
    this.wrapX_ = options.wrapX !== undefined ? options.wrapX : false;

  }

  /**
  * Turns the attributions option into an attributions function.
  * @param {module:ol/source/Source~AttributionLike|undefined} attributionLike The attribution option.
  * @return {?module:ol/source/Source~Attribution} An attribution function (or null).
  */
  adaptAttributions_(attributionLike) {
    if (!attributionLike) {
      return null;
    }
    if (Array.isArray(attributionLike)) {
      return function(frameState) {
        return attributionLike;
      };
    }

    if (typeof attributionLike === 'function') {
      return attributionLike;
    }

    return function(frameState) {
      return [attributionLike];
    };
  }

  /**
  * Get the attribution function for the source.
  * @return {?module:ol/source/Source~Attribution} Attribution function.
  */
  getAttributions() {
    return this.attributions_;
  }

  /**
  * Get the projection of the source.
  * @return {module:ol/proj/Projection} Projection.
  * @api
  */
  getProjection() {
    return this.projection_;
  }

  /**
  * @abstract
  * @return {Array<number>|undefined} Resolutions.
  */
  getResolutions() {}

  /**
  * Get the state of the source, see {@link module:ol/source/State~State} for possible states.
  * @return {module:ol/source/State} State.
  * @api
  */
  getState() {
    return this.state_;
  }

  /**
  * @return {boolean|undefined} Wrap X.
  */
  getWrapX() {
    return this.wrapX_;
  }

  /**
  * Refreshes the source and finally dispatches a 'change' event.
  * @api
  */
  refresh() {
    this.changed();
  }

  /**
  * Set the attributions of the source.
  * @param {module:ol/source/Source~AttributionLike|undefined} attributions Attributions.
  *     Can be passed as `string`, `Array<string>`, `{@link module:ol/source/Source~Attribution}`,
  *     or `undefined`.
  * @api
  */
  setAttributions(attributions) {
    this.attributions_ = this.adaptAttributions_(attributions);
    this.changed();
  }

  /**
  * Set the state of the source.
  * @param {module:ol/source/State} state State.
  * @protected
  */
  setState(state) {
    this.state_ = state;
    this.changed();
  }
}

/**
 * @param {module:ol/coordinate~Coordinate} coordinate Coordinate.
 * @param {number} resolution Resolution.
 * @param {number} rotation Rotation.
 * @param {number} hitTolerance Hit tolerance in pixels.
 * @param {Object<string, boolean>} skippedFeatureUids Skipped feature uids.
 * @param {function((module:ol/Feature|module:ol/render/Feature)): T} callback Feature callback.
 * @return {T|void} Callback result.
 * @template T
 */
Source.prototype.forEachFeatureAtCoordinate = VOID;


export default Source;