local lines = {}

-- save "lines" to be able to remove them after loading
function onSave()
  return JSON.encode(lines)
end

function onLoad(savedData)
  lines = JSON.decode(savedData) or {}
end

-- create timer when numpad 0 is pressed
function onScriptingButtonDown(index, player_color)
  if index ~= 10 then return end
  TimerID = Wait.time(function() draw_from(Player[player_color]) end, 1)
end

-- called for long press of numpad 0, draws lines from hovered object to selected objects
function draw_from(player)
  local source = player.getHoverObject()
  if not source then return end

  for _, item in ipairs(player.getSelectedObjects()) do
    if item.getGUID() ~= source.getGUID() then
      if item.getGUID() > source.getGUID() then
        draw_with_pair(item, source)
      else
        draw_with_pair(source, item)
      end
    end
  end

  process_lines()
end

-- general drawing of all lines between selected objects
function onScriptingButtonUp(index, player_color)
  if index ~= 10 then return end
  -- returns true only if there is a timer to cancel. If this is false then we've waited longer than a second.
  if not Wait.stop(TimerID) then return end

  local items = Player[player_color].getSelectedObjects()
  if #items < 2 then
    broadcastToColor("You must have at least two items selected (currently: " .. #items .. ").", player_color, "Red")
    return
  end

  table.sort(items, function(a, b) return a.getGUID() > b.getGUID() end)

  for f = 1, #items - 1 do
    for s = f + 1, #items do
      draw_with_pair(items[f], items[s])
    end
  end

  process_lines()
end

-- adds two objects to table of vector lines
function draw_with_pair(first, second)
  local guid_first  = first.getGUID()
  local guid_second = second.getGUID()

  if Global.getVectorLines() == nil then lines = {} end
  if not lines[guid_first] then lines[guid_first] = {} end

  if lines[guid_first][guid_second] then
    lines[guid_first][guid_second] = nil
  else
    lines[guid_first][guid_second] = { points = { first.getPosition(), second.getPosition() }, color = "White" }
  end
end

-- updates the global vector lines based on "lines"
function process_lines()
  local drawing = {}

  for _, first in pairs(lines) do
    for _, data in pairs(first) do
      table.insert(drawing, data)
    end
  end

  Global.setVectorLines(drawing)
end