import { PointerHolder } from './PointerHolder'
import { Float2, Float3 } from './Math'

/**
 * Helper that enables camera interaction similar to sketchfab or Google Maps.
 *
 * Clients notify the camera manipulator of various mouse or touch events, then periodically call
 * its getLookAt() method so that they can adjust their camera(s). Three modes are supported: ORBIT,
 * MAP, and FREE_FLIGHT. To construct a manipulator instance, the desired mode is passed into the
 * create method.
 */
export interface CameraManipulator extends PointerHolder {
  /**
   * In MAP and ORBIT modes, dollys the camera along the viewing direction.
   * In FREE_FLIGHT mode, adjusts the move speed of the camera.
   *
   * @param x X-coordinate for point of interest in viewport space, ignored in FREE_FLIGHT mode
   * @param y Y-coordinate for point of interest in viewport space, ignored in FREE_FLIGHT mode
   * @param scrolldelta In MAP and ORBIT modes, negative means "zoom in", positive means "zoom out"
   *                    In FREE_FLIGHT mode, negative means "slower", positive means "faster"
   */
  scroll(x: number, y: number, scrolldelta: number): void

  /**
   * Processes input and updates internal state.
   *
   * This must be called once every frame before getLookAt is valid.
   *
   * @param deltaTime The amount of time, in seconds, passed since the previous call to update.
   */
  update(deltaTime: number): void

  /**
   * Starts a grabbing session (i.e. the user is dragging around in the viewport).
   *
   * In MAP mode, this starts a panning session.
   * In ORBIT mode, this starts either rotating or strafing.
   * In FREE_FLIGHT mode, this starts a nodal panning session.
   *
   * @param x X-coordinate for point of interest in viewport space
   * @param y Y-coordinate for point of interest in viewport space
   * @param strafe ORBIT mode only; if true, starts a translation rather than a rotation
   */
  grabBegin(x: number, y: number, strafe: boolean): void

  /**
   * Updates a grabbing session.
   *
   * This must be called at least once between grabBegin / grabEnd to dirty the camera.
   */
  grabUpdate(x: number, y: number): void

  /**
   * Ends a grabbing session.
   */
  grabEnd(): void

  getLookAt(): [eye: Float3, center: Float3, up: Float3]
}

export interface OrbitCameraManipulatorConfig {
  /**
   * Initial eye position in world space
   * @default (0,0,1)
   */
  orbitHomePosition?: Float3
  /**
   * World-space position of interest
   * @default (0,0,0)
   */
  targetPosition?: Float3
  /**
   * Orientation for the home position
   * @default (0,1,0)
   */
  upVector?: Float3
  /**
   * Multiplied with scroll delta
   * @default 0.01
   */
  zoomSpeed?: [number]
  /**
   * Multiplied with viewport delta
   * @default 0.01
   */
  orbitSpeed?: Float2
}