/**
 * @module ol/centerconstraint
 */
import {clamp} from './math.js';


/**
 * @typedef {function((import("./coordinate.js").Coordinate|undefined), number, import("./size.js").Size, boolean=): (import("./coordinate.js").Coordinate|undefined)} Type
 */


/**
 * @param {import("./extent.js").Extent} extent Extent.
 * @param {boolean} onlyCenter If true, the constraint will only apply to the view center.
 * @param {boolean} smooth If true, the view will be able to go slightly out of the given extent
 * (only during interaction and animation).
 * @return {Type} The constraint.
 */
export function createExtent(extent, onlyCenter, smooth) {
  return (
    /**
     * @param {import("./coordinate.js").Coordinate|undefined} center Center.
     * @param {number} resolution Resolution.
     * @param {import("./size.js").Size} size Viewport size; unused if `onlyCenter` was specified.
     * @param {boolean=} opt_isMoving True if an interaction or animation is in progress.
     * @return {import("./coordinate.js").Coordinate|undefined} Center.
     */
    function(center, resolution, size, opt_isMoving) {
      if (center) {
        const viewWidth = onlyCenter ? 0 : size[0] * resolution;
        const viewHeight = onlyCenter ? 0 : size[1] * resolution;
        let minX = extent[0] + viewWidth / 2;
        let maxX = extent[2] - viewWidth / 2;
        let minY = extent[1] + viewHeight / 2;
        let maxY = extent[3] - viewHeight / 2;

        // note: when zooming out of bounds, min and max values for x and y may
        // end up inverted (min > max); this has to be accounted for
        if (minX > maxX) {
          minX = (maxX + minX) / 2;
          maxX = minX;
        }
        if (minY > maxY) {
          minY = (maxY + minY) / 2;
          maxY = minY;
        }

        let x = clamp(center[0], minX, maxX);
        let y = clamp(center[1], minY, maxY);
        const ratio = 30 * resolution;

        // during an interaction, allow some overscroll
        if (opt_isMoving && smooth) {
          x += -ratio * Math.log(1 + Math.max(0, minX - center[0]) / ratio) +
            ratio * Math.log(1 + Math.max(0, center[0] - maxX) / ratio);
          y += -ratio * Math.log(1 + Math.max(0, minY - center[1]) / ratio) +
            ratio * Math.log(1 + Math.max(0, center[1] - maxY) / ratio);
        }

        return [x, y];
      } else {
        return undefined;
      }
    }
  );
}


/**
 * @param {import("./coordinate.js").Coordinate=} center Center.
 * @return {import("./coordinate.js").Coordinate|undefined} Center.
 */
export function none(center) {
  return center;
}