local Point = { }

function Point.copy(pt)
  return { x = pt.x, y = pt.y, z = pt.z }
end

function Point.subtract(a, b)
  a.x = a.x - b.x
  a.y = a.y - b.y
  a.z = a.z - b.z
end

-- real distance
function Point.pythagoreanDistance(a, b)
  return math.sqrt(
           math.pow(a.x - b.x, 2) +
           math.pow(a.y - b.y, 2) +
           math.pow(a.z - b.z, 2))
end

-- turtle distance
function Point.turtleDistance(a, b)
  if a.y and b.y then
    return math.abs(a.x - b.x) + 
           math.abs(a.y - b.y) +
           math.abs(a.z - b.z)
  else
    return math.abs(a.x - b.x) +
           math.abs(a.z - b.z)
  end
end

function Point.calculateTurns(ih, oh)
  if ih == oh then
    return 0
  end
  if (ih % 2) == (oh % 2) then
    return 2
  end
  return 1
end

-- Calculate distance to location including turns
-- also returns the resulting heading
function Point.calculateMoves(pta, ptb, distance)
  local heading = pta.heading
  local moves = distance or Point.turtleDistance(pta, ptb)
  if (pta.heading % 2) == 0 and pta.z ~= ptb.z then
    moves = moves + 1
    if ptb.heading and (ptb.heading % 2 == 1) then
      heading = ptb.heading
    elseif ptb.z > pta.z then
      heading = 1
    else
      heading = 3
    end
  elseif (pta.heading % 2) == 1 and pta.x ~= ptb.x then
    moves = moves + 1
    if ptb.heading and (ptb.heading % 2 == 0) then
      heading = ptb.heading
    elseif ptb.x > pta.x then
      heading = 0
    else
      heading = 2
    end
  end

  if ptb.heading then
    if heading ~= ptb.heading then
      moves = moves + Point.calculateTurns(heading, ptb.heading)
      heading = ptb.heading
    end
  end
  
  return moves, heading
end

-- given a set of points, find the one taking the least moves
function Point.closest(reference, pts)
  local lpt, lm -- lowest
  for _,pt in pairs(pts) do
    local m = Point.calculateMoves(reference, pt)
    if not lm or m < lm then
      lpt = pt
      lm = m
    end
  end
  return lpt
end

function Point.adjacentPoints(pt)
  local pts = { }

  for _, hi in pairs(turtle.getHeadings()) do
    table.insert(pts, { x = pt.x + hi.xd, y = pt.y + hi.yd, z = pt.z + hi.zd })
  end

  return pts
end

return Point

--[[
function Point.toBox(pt, width, length, height)
  return { ax = pt.x,
           ay = pt.y,
           az = pt.z,
           bx = pt.x + width - 1,
           by = pt.y + height - 1,
           bz = pt.z + length - 1
         }
end

function Point.inBox(pt, box)
  return pt.x >= box.ax and
         pt.z >= box.az and
         pt.x <= box.bx and
         pt.z <= box.bz
end

Box = { }

function Box.contain(boundingBox, containedBox)

  local shiftX = boundingBox.ax - containedBox.ax
  if shiftX > 0 then
    containedBox.ax = containedBox.ax + shiftX
    containedBox.bx = containedBox.bx + shiftX
  end
  local shiftZ = boundingBox.az - containedBox.az
  if shiftZ > 0 then
    containedBox.az = containedBox.az + shiftZ
    containedBox.bz = containedBox.bz + shiftZ
  end

  shiftX = boundingBox.bx - containedBox.bx
  if shiftX < 0 then
    containedBox.ax = containedBox.ax + shiftX
    containedBox.bx = containedBox.bx + shiftX
  end
  shiftZ = boundingBox.bz - containedBox.bz
  if shiftZ < 0 then
    containedBox.az = containedBox.az + shiftZ
    containedBox.bz = containedBox.bz + shiftZ
  end
end
--]]