import { DEFAULT_ANGLE_STEP } from '@pascal-app/core'

/**
 * Shared rotation delta for the 2D corner rotate-arrow affordances (column /
 * elevator / roof-segment / shelf / spawn / stair — all structurally
 * identical). Measures the pointer's angular sweep from the grab bearing
 * around the node center, wrapped to [-π, π] so a drag crossing ±π keeps its
 * sign, then snaps it to the 15° increment unless `free` (the held Shift the
 * contextual HUD advertises). The 2D twin of the 3D gizmo's
 * `snapDirectRotationDelta`, so rotating a node reads the same in both views.
 */
export function rotateAffordanceDelta(args: {
  center: readonly [number, number]
  initialAngle: number
  planPoint: readonly [number, number]
  free: boolean
}): number {
  const { center, initialAngle, planPoint, free } = args
  const currentAngle = Math.atan2(planPoint[1] - center[1], planPoint[0] - center[0])
  let delta = currentAngle - initialAngle
  while (delta > Math.PI) delta -= 2 * Math.PI
  while (delta < -Math.PI) delta += 2 * Math.PI
  return free ? delta : Math.round(delta / DEFAULT_ANGLE_STEP) * DEFAULT_ANGLE_STEP
}