function widget:GetInfo()
   return {
      name         = "ScoutAvoidance",
      desc         = "Make designated scouts stay out of range or sight of enemy units",
      author       = "Berder",
      date         = "2020",
      license      = "GPLv2",
      layer        = 11,
      enabled      = true
   }
end

-- Credit to terve886 for his ShieldtargetAI widget
-- and to snoke for AutoLLT, both of which I drew from.

local pi = math.pi
local sin = math.sin
local cos = math.cos
local atan = math.atan
local sqrt = math.sqrt
local sqrt2inv = 1 / sqrt(2)
local UPDATE_FRAME=10
local UnitStack = {}
local GetUnitMaxRange = Spring.GetUnitMaxRange
local GetUnitPosition = Spring.GetUnitPosition
local GetMyAllyTeamID = Spring.GetMyAllyTeamID
local GiveOrderToUnit = Spring.GiveOrderToUnit
local GetGroundHeight = Spring.GetGroundHeight
local GetUnitsInSphere = Spring.GetUnitsInSphere
local GetUnitsInCylinder = Spring.GetUnitsInCylinder
local GetUnitAllyTeam = Spring.GetUnitAllyTeam
local GetUnitIsDead = Spring.GetUnitIsDead
local GetMyTeamID = Spring.GetMyTeamID
local GetUnitDefID = Spring.GetUnitDefID
local GetUnitNearestEnemy = Spring.GetUnitNearestEnemy
local GetUnitShieldState = Spring.GetUnitShieldState
local GetTeamUnits = Spring.GetTeamUnits
local GetUnitStates = Spring.GetUnitStates
local GetSelectedUnits = Spring.GetSelectedUnits

local WINDOW_COLOR = {1, 1, 1, 0.7}
local WINDOW_FONT_SIZE = 12
local WINDOW_B_SIZE = 12
local WINDOW_LINE_PADDING = 3
local WINDOW_CELL_PADDING = 1

local Echo = Spring.Echo
local GetSpecState = Spring.GetSpectatingState
local FULL_CIRCLE_RADIANT = 2 * pi
local CMD_UNIT_SET_TARGET = 34923
local CMD_UNIT_CANCEL_TARGET = 34924
local CMD_STOP = CMD.STOP
local CMD_ATTACK = CMD.ATTACK

-- we start moving when within (enemy range + SafetyBuffer) of the enemy
local SafetyBuffer = 200

local havens = {}

local window

local keypressmem = {}

local AlwaysShowWindow = true

local ATTACK_RANGE = 1
local SIGHT_RANGE = 2
local OFF = 3

local function UpdateHavens()
   local team = GetMyAllyTeamID()
   local count = Spring.GetTeamRulesParam(team, "haven_count")
   havens = {}
   if count ~= nil then
      for i = 1, count do
         havens[i] = {x = Spring.GetTeamRulesParam(team, "haven_x" .. i),
                      z = Spring.GetTeamRulesParam(team, "haven_z" .. i)}
      end
   end
end


local ScoutAvoidanceController = {
   unitID,
   pos,
   searchRange,
   allyTeamID = GetMyAllyTeamID(),
   avoiding = false,
   mode = ATTACK_RANGE,
   avoidingEnemy = nil,

   new = function(self, unitID)
      self = deepcopy(self)
      self.unitID = unitID
      self.pos = {GetUnitPosition(self.unitID)}
      self.searchRange = Spring.GetUnitSensorRadius(unitID, "los")
      return self
   end,

   unset = function(self)
      -- Echo("ScoutAvoidanceController removed:" .. self.unitID)
      GiveOrderToUnit(self.unitID,CMD_STOP, {}, {""},1)
      return nil
   end,

   getRetreatZone = function (self, retreatVector)
      -- returns the closest retreat zone that is behind us relative to the enemy
      -- or nil if no such zone exists
      -- retreatVector is a vector pointing behind us a short distance relative to the enemy
      local bestZoneIx = -1
      local bestZoneDistance = 999999999999

      -- rotate 45 degrees (not preserving length)
      local ret1X = retreatVector[1] + retreatVector[3]
      local ret1Z = -retreatVector[1] + retreatVector[3]

      -- rotate 45 degrees the other way (not preserving length)
      local ret2X = retreatVector[1] - retreatVector[3]
      local ret2Z = retreatVector[1] + retreatVector[3]

      -- basePos = self.pos + retreatVector
      -- (haven - basePos) . retreatVector > 0
      local baseX = self.pos[1] + retreatVector[1]
      local baseZ = self.pos[3] + retreatVector[3]

      for i=1, #havens do
         local dotProd1 = (havens[i].x - baseX) * ret1X + (havens[i].z - baseZ) * ret1Z
         local dotProd2 = (havens[i].x - baseX) * ret2X + (havens[i].z - baseZ) * ret2Z
         --            │ R1
         --            │      E     R2
         --   R5       │
         --            │   U
         --            │ϴ1/
         --            │ /ϴ2    R3
         --            B─────────────────
         --  R6
         --
         --                 R4

         -- E = enemy
         -- U = unit
         -- B = base position (straight away from enemy a short distance)
         -- ϴ1 = ϴ2 = 45 degrees
         --
         -- R1, R2, R3 = invalid retreat zones (blocked by enemy)
         -- R4, R5, R6 = valid retreat zones, of which we pick the closest.
         --
         if (dotProd1 > 0 or dotProd2 > 0) then
            local dx = havens[i].x - self.pos[1]
            local dz = havens[i].z - self.pos[3]
            local sqDist = dx * dx + dz * dz
            if (sqDist < bestZoneDistance) then
               bestZoneIx = i
               bestZoneDistance = sqDist
            end
         end
      end

      if (bestZoneIx == -1) then
         return nil
      end

      return havens[bestZoneIx]
   end,

   getEnemyRange = function (self, enemyID)
      local enemyRange = 0
      local DefID = GetUnitDefID(enemyID)
      if not(DefID == nil) then
         if self.mode == ATTACK_RANGE then
            if UnitDefs[DefID].weapons then
               for j=1, #UnitDefs[DefID].weapons do
                  range = WeaponDefs[UnitDefs[DefID].weapons[j].weaponDef].range
                  if (range and range > enemyRange) then
                     enemyRange = range
                  end
               end
            end
         elseif self.mode == SIGHT_RANGE then
            if UnitDefs[DefID].losRadius then
               enemyRange = UnitDefs[DefID].losRadius
            end
         end
      end

      if (enemyRange == 0) then
         enemyRange = 500
      end

      return enemyRange
   end,

   checkOneEnemy = function(self, enemyID)
      local enemyRange = self:getEnemyRange(enemyID)

      local enemySeparation = Spring.GetUnitSeparation(self.unitID, enemyID)

      if (enemySeparation == nil) then
         enemySeparation = 1000
      end
      if (enemySeparation < 50) then
         enemySeparation = 50 -- don't divide by 0
      end
      if (enemySeparation < enemyRange + SafetyBuffer) then
         local enemyPos = {GetUnitPosition(enemyID)}
         -- walk in the opposite direction from the enemy
         local retreatX = (self.pos[1] - enemyPos[1]) * 100 / enemySeparation
         local retreatY = 0
         local retreatZ = (self.pos[3] - enemyPos[3]) * 100 / enemySeparation

         return {x=retreatX, z=retreatZ}
      end
      return nil
   end,

   avoidEnemy = function (self)
      local units = GetUnitsInCylinder(self.pos[1], self.pos[3], self.searchRange, Spring.ENEMY_UNITS)
      for i=1, #units do
         if (GetUnitIsDead(units[i]) == false) then
            local result = self:checkOneEnemy(units[i])
            if result ~= nil then
               local retreatZone = self:getRetreatZone({result.x, 0, result.z})
               if (retreatZone ~= nil) then
                  GiveOrderToUnit(self.unitID, CMD.FIGHT, {retreatZone.x, self.pos[2], retreatZone.z}, {})
               else
                  GiveOrderToUnit(self.unitID, CMD.FIGHT, {self.pos[1] + result.x, self.pos[2], self.pos[3] + result.z}, {} )
               end
               self.retreating = true
               self.avoidingEnemy = enemyID
               return true
            end
         end
      end
      if (self.retreating) then
         -- we were retreating, but now no enemy is near, so stop.
         self.retreating = false
         self.avoidingEnemy = nil
         GiveOrderToUnit(self.unitID,CMD_STOP, {}, {""},1)
      end
      return false
   end,

   handle=function(self, n)
      local cQueue = Spring.GetCommandQueue(self.unitID, 1)
      -- avoidance is active when idle or when walk-fighting
      if(cQueue == nil or #cQueue == 0 or cQueue[1].id==CMD.FIGHT) then
         self.pos = {GetUnitPosition(self.unitID)}
         -- if the enemy we were avoiding before is still in range,
         -- and we're still on an attack-move command,
         -- don't issue another command and just keep doing what we were doing.
         -- (for efficiency)
         if cQueue ~= nil and #cQueue > 0 and cQueue[1].id==CMD.FIGHT and self.avoidingEnemy ~= nil then
            local result = self:checkOneEnemy(self.avoidingEnemy)
            if result ~= nil then
               return
            else
               self.avoidingEnemy = nil
            end
         end
         self:avoidEnemy()
      else
         self.retreating = false
      end
   end
}

function widget:ToggleAvoidance()
   if keypressmem["ToggleAvoidance"] ~= nil then
      return
   end
   keypressmem["ToggleAvoidance"] = true
   local someAttackRange = false
   local someSightRange = false

   for k,unitID in pairs(GetSelectedUnits()) do
      if UnitStack[unitID] ~= nil then
         if UnitStack[unitID].mode == ATTACK_RANGE then
            someAttackRange = true
         elseif UnitStack[unitID].mode == SIGHT_RANGE then
            someSightRange = true
         end
      end
   end

   local mode = ATTACK_RANGE
   if someAttackRange then
      mode = SIGHT_RANGE
   elseif someSightRange then
      mode = OFF
   end

   for k,unitID in pairs(GetSelectedUnits()) do
      if UnitStack[unitID] ~= nil then
         if mode == OFF then
            UnitStack[unitID]=UnitStack[unitID]:unset()
         else
            UnitStack[unitID].mode = mode
         end
      elseif mode ~= OFF then
         UnitStack[unitID] = ScoutAvoidanceController:new(unitID)
         UnitStack[unitID].mode = mode
      end
   end
end


function distance ( x1, y1, x2, y2 )
   local dx = (x1 - x2)
   local dy = (y1 - y2)
   return sqrt ( dx * dx + dy * dy )
end

function widget:UnitFinished(unitID, unitDefID, unitTeam)
end

function widget:CommandNotify(cmdID, cmdParams, cmdOptions)
end

function widget:UnitDestroyed(unitID)
   if not (UnitStack[unitID]==nil) then
      UnitStack[unitID]=UnitStack[unitID]:unset();
   end
end


options_path = "Settings/Unit Behaviour/Scout Avoidance"
options_order = {"show_gui", "hotkey_toggle"}
options = {
   show_gui = {
      name = 'Always Show Window',
      type = 'bool',
      value = true,
      noHotkey = true,
      OnChange = function(a)
         AlwaysShowWindow = a.value
      end,
   },
   hotkey_toggle = {
      name = "Toggle Avoidance Hotkey",
      type = "button",
      noHotkey = false,
      action = "toggle_avoidance",
   },
}

function widget:initHotkeyActions()
   widgetHandler:AddAction("toggle_avoidance", ToggleAvoidance, nil, 'tp')
end

function widget:UiDisplay()
   window:SetVisibility(false)
   local scoutSelected = false
   local someAttackRange = false
   local someSightRange = false
   local someOff = false
   for k,unitID in pairs(GetSelectedUnits()) do
      if UnitStack[unitID] ~= nil then
         scoutSelected = true
         if UnitStack[unitID].mode == ATTACK_RANGE then
            someAttackRange = true
         elseif UnitStack[unitID].mode == SIGHT_RANGE then
            someSightRange = true
         end
      else
         someOff = true
      end
   end

   local mode = "OFF"
   if someAttackRange and someSightRange or someOff and someAttackRange or someSightRange and someOff then
      mode = "mixed"
   elseif someAttackRange then
      mode = "avoid attacks"
   elseif someSightRange then
      mode = "avoid sight"
   end
   window.children[3]:SetCaption(mode)

   if scoutSelected then
      window:SetVisibility(true)
   end
   if AlwaysShowWindow and #GetSelectedUnits() > 0 then
      window:SetVisibility(true)
   end
end


function widget:GameFrame(n)
   keypressmem = {}
   widget:UiDisplay()
   if (n%UPDATE_FRAME==0) then
      UpdateHavens()
      for unitID,unit in pairs(UnitStack) do
         unit:handle()
      end
   end
end

function widget:initGUI()
   window = WG.Chili.Window:New{
      name = "Scout Avoidance Window",
      x = 0,
      y = 100,
      savespace = false,
      resizable = false,
      draggable = true,
      autosize = false,
      color = WINDOW_COLOR,
      parent = WG.Chili.Screen0,
      mainHeight = 100,
      maxHeight = 100,
      maxWidth = 300,
      minWidth = 300,
      children = {
         WG.Chili.Label:New{
            x = 0,
            right = 50,
            y = 0,
            height = WINDOW_FONT_SIZE,
            align = "center",
            font = {size = 12, outline = true, color = {1, 1, 0, 1}},
            caption = "- Scout Avoidance Controller -",
            fontSize = WINDOW_FONT_SIZE,
         },
         WG.Chili.Label:New{
            x = 0,
            y = (WINDOW_FONT_SIZE + WINDOW_LINE_PADDING) * 2,
            right = 0,
            height = WINDOW_FONT_SIZE,
            caption = "Avoidance:",
            fontSize = WINDOW_FONT_SIZE,
         },
         WG.Chili.Label:New{
            x = 100,
            y = (WINDOW_FONT_SIZE + WINDOW_LINE_PADDING) * 2,
            height = WINDOW_FONT_SIZE,
            caption = "OFF",
            fontSize = WINDOW_FONT_SIZE,
         },
         WG.Chili.Button:New{
            x = 200,
            y = (WINDOW_FONT_SIZE + WINDOW_LINE_PADDING) * 2,
            height = WINDOW_FONT_SIZE,
            minWidth = 50,
            maxWidth = 50,
            name = "AvoidanceButton",
            fontSize = WINDOW_FONT_SIZE,
            caption = "Toggle",
            OnClick  = {
               function()
                  widget:ToggleAvoidance()
               end
            },
         },
      }
   }
   window:SetVisibility(false)
end


function deepcopy(orig)
   local orig_type = type(orig)
   local copy
   if orig_type == 'table' then
      copy = {}
      for orig_key, orig_value in next, orig, nil do
         copy[deepcopy(orig_key)] = deepcopy(orig_value)
      end
      setmetatable(copy, deepcopy(getmetatable(orig)))
   else
      copy = orig
   end
   return copy
end

function dump(o)
   if type(o) == 'table' then
      local s = '{ '
      for k,v in pairs(o) do
         if type(k) ~= 'number' then k = '"'..k..'"' end
         s = s .. '['..k..'] = ' .. dump(v) .. ','
      end
      return s .. '} '
   else
      return tostring(o)
   end
end

local function DisableForSpec()
   if GetSpecState() then
      widgetHandler:RemoveWidget()
   end
end


function widget:Initialize()
   DisableForSpec()
   widget:initGUI()
   widget:initHotkeyActions()
end


function widget:PlayerChanged (playerID)
   DisableForSpec()
end