radar.coffee

# Find closest point to a set of points.
findClosestPoint = (needle, haystack) ->
  (init = new Point).diff = Number.MAX_VALUE
  comparator = (memo, point) ->
    point.diff = Math.abs(needle.x - point.x) + Math.abs(needle.y - point.y)
    if point.diff < memo.diff then point else memo
  _.foldl haystack, comparator, init

# Find closest point to a set of points based on angles.
findClosestPointByAngle = (needle, haystack, origin) ->
  (init = new Point).diff = Number.MAX_VALUE
  needle_angle = Point.angleForCircle origin, needle
  comparator = (memo, point) ->
    point.diff = Math.abs Point.angleForCircle(origin, point) - needle_angle
    if point.diff < memo.diff then point else memo
  _.foldl haystack, comparator, init

# Find closest point to a set of points based on angles *and* co-ords.
findClosestPointByAngleAndCoords = (needle, haystack, origin) ->
  (init = new Point).diff = Number.MAX_VALUE
  needle_angle = Point.angleForCircle origin, needle
  comparator = (memo, point) ->
    point.diff = (Math.abs Point.angleForCircle(origin, point) - needle_angle) + Math.abs(needle.x - point.x) + Math.abs(needle.y - point.y)
    if point.diff < memo.diff then point else memo
  _.foldl haystack, comparator, init