var DEFAULT_RENDER_PRIORITY = 1000;

/**
 * @typedef {import('../model').Base} Base
 * @typedef {import('../model').Connection} Connection
 * @typedef {import('../model').Shape} Shape
 *
 * @typedef {import('../core/EventBus').default} EventBus
 */

/**
 * The base implementation of shape and connection renderers.
 *
 * @param {EventBus} eventBus
 * @param {number} [renderPriority=1000]
 */
export default function BaseRenderer(eventBus, renderPriority) {
  var self = this;

  renderPriority = renderPriority || DEFAULT_RENDER_PRIORITY;

  eventBus.on([ 'render.shape', 'render.connection' ], renderPriority, function(evt, context) {
    var type = evt.type,
        element = context.element,
        visuals = context.gfx,
        attrs = context.attrs;

    if (self.canRender(element)) {
      if (type === 'render.shape') {
        return self.drawShape(visuals, element, attrs);
      } else {
        return self.drawConnection(visuals, element, attrs);
      }
    }
  });

  eventBus.on([ 'render.getShapePath', 'render.getConnectionPath' ], renderPriority, function(evt, element) {
    if (self.canRender(element)) {
      if (evt.type === 'render.getShapePath') {
        return self.getShapePath(element);
      } else {
        return self.getConnectionPath(element);
      }
    }
  });
}

/**
 * Checks whether an element can be rendered.
 *
 * @param {Base} element The element to be rendered.
 *
 * @returns {boolean} Whether the element can be rendered.
 */
BaseRenderer.prototype.canRender = function(element) {};

/**
 * Draws a shape.
 *
 * @param {SVGElement} visuals The SVG element to draw the shape into.
 * @param {Shape} shape The shape to be drawn.
 *
 * @returns {SVGElement} The SVG element of the shape drawn.
 */
BaseRenderer.prototype.drawShape = function(visuals, shape) {};

/**
 * Draws a connection.
 *
 * @param {SVGElement} visuals The SVG element to draw the connection into.
 * @param {Connection} connection The connection to be drawn.
 *
 * @returns {SVGElement} The SVG element of the connection drawn.
 */
BaseRenderer.prototype.drawConnection = function(visuals, connection) {};

/**
 * Gets the SVG path of the graphical representation of a shape.
 *
 * @param {Shape} shape The shape.
 *
 * @return {string} The SVG path of the shape.
 */
BaseRenderer.prototype.getShapePath = function(shape) {};

/**
 * Gets the SVG path of the graphical representation of a connection.
 *
 * @param {Connection} connection The connection.
 *
 * @return {string} The SVG path of the connection.
 */
BaseRenderer.prototype.getConnectionPath = function(connection) {};