local version = "1.0" -- String declaration. We can do this before the GetInfo callin (event).
function widget:GetInfo()
    return {
      name      = "Ez Selector " .. version, -- .. means to combine two strings. The second string, 'version' (see above) is added to the end of this string.
      desc      = "Selects units when a user presses a certain key.",
      author    = "_Shaman",
      date      = "May 19, 2016",
      license   = "None",
      layer     = 15,
      enabled   = true,
    }
  end -- All widgets/gadgets need this to run. You can declare variables before it though. This tells the engine this is a widget.

  --config--
local debug = false
local color = {raider = {0.25,0.41,1},
                assault = {0.86,0.08,0.24},
                skirm = {0.25,0.55,0.13},
                arty = {0.8,0.68,0},
                riot = {0,0.81,0.82},
                none = {1,1,1},
                growth = {0.19,0.5,0.08},
                shrink = {1,0.08,0.58},} -- OpenGL uses floating points instead of 255 (float = decimal num)
local keypresses = {raider = 113,
                    assault = 97,
                    skirm = 116,
                    arty = 120,
                    riot = 122,
                    plus = 91, -- increased radius.
                    minus = 93, -- decrease radius. Change these as desired.
                    } -- Table. Format is Key = Value. 113.115.100.102.103

local triggerkeys = {}
triggerkeys[keypresses.raider] = 1
triggerkeys[keypresses.assault] = 1
triggerkeys[keypresses.skirm] = 1
triggerkeys[keypresses.arty] = 1
triggerkeys[keypresses.riot] = 1
local rad = 150
local on = false
local ontype = "none" -- we'll use ontype and on to talk to gameframe and drawworld.
local unittypes = {raider = {
                    armpw = 1,
                    corak = 1,
                    corgator = 1,
                    amphraider3 = 1,
                    corpyro = 1,
                    corsh = 1,
                    subraider = 1,
                    armpw = 1,
                    },
                   assault = {
                    armzeus = 1,
                    armorco = 1,
                    spiderassault = 1,
                    corgol = 1,
                    correap = 1,
                    shipraider = 1,
                    amphassault = 1,
                    corraid = 1,
                    corthud = 1,
                    corcan = 1,
                    hoverassault = 1,
                    funnelweb = 1,
                   },
                   skirm = {
                    armrock = 1,
                    armsptk = 1,
                    slowmort = 1,
                    corstorm = 1,
                    shipskirm = 1,
                    amphfloater = 1,
                    cormist = 1,
                   },
                   arty = {
                    armham = 1,
                    armraven = 1,
                    armsnipe = 1,
                    shieldarty = 1,
                    firewalker = 1,
                    corgarp = 1,
                    armmerl = 1,
                    cormart = 1,
                    trem = 1,
                    armcrabe = 1,
                    subarty = 1,
                    shiparty = 1,
                    corbats = 1,
                    reef = 1,
                    armmanni = 1,
                   },
                   riot = {
                    armwar = 1,
                    cormak = 1,
                    spiderriot = 1,
                    arm_venom = 1,
                    jumpblackhole = 1,
                    corsumo = 1,
                    corlevlr = 1,
                    tawf114 = 1,
                    amphriot = 1,
                    amphraider2 = 1,
                    shiptorp = 1,
                    dante = 1,
                    hoverriot = 1,
                   }
                  }

local selection = {}
local selected = {}
local checked = {}
local radchanged = false
local originalrad = rad
local radchangeddrawtime = 0
local lastrelease = -1

function widget:KeyPress(key, mods, isRepeat) -- This callin is triggered whenever the user presses a key.
  if key == keypresses.plus then
    if radchanged == false then
      originalrad = rad
    end
    rad = rad+10
    radchanged = true
    radchangeddrawtime = 12
  end
  if key == keypresses.minus and rad > 10 then
    rad = rad-10
    radchanged = true
    radchangeddrawtime = 12
  end
  if isRepeat == false and debug then
    Spring.Echo("game_message: key: " .. key)
  end
  if key == keypresses.raider and isRepeat and ontype == "none" then --Here keypresses.raider is the same as keypresses["raider"]. This is how you look up values in a table.
    on = true -- we're using this variable to talk to KeyRelease and DrawWorld. This way then they know we're working on getting a selection going.
    ontype = "raider"
  end
  if key == keypresses.skirm and isRepeat and ontype == "none" then
    on = true
    ontype = "skirm"
  end
  if key == keypresses.assault and isRepeat and ontype == "none" then
    on = true
    ontype = "assault"
  end
  if key == keypresses.arty and isRepeat and ontype == "none" then
    on = true
    ontype = "arty"
  end
  if key == keypresses.riot and isRepeat and ontype == "none" then
    on = true
    ontype = "riot"
  end
end

function widget:GameFrame(f) -- called once every frame. This is so we don't keep looking for units every keypress.
  if radchanged and radchangeddrawtime > 0 then
    radchangeddrawtime = radchangeddrawtime - 1
    if radchangeddrawtime == 0 then
      radchanged = false
    end
  end
  if f%2 == 0 then -- % means the remainers left after divided by the second number. here it's framenum divided by 2. So this happens every 2nd frame.
  if on and ontype ~= "none" then
    local x,y = Spring.GetMouseState()
    local _,pos = Spring.TraceScreenRay(x,y,true)
    if type(pos) == "table" then -- prevent crashing from attempting to index a number value. The above seems to give random numbers sometimes.
      x = pos[1];y = pos[3];pos = nil -- ; is effectively a new line in LUA. This just makes your code look nicer.
    else
      if Spring.ValidUnitID(pos) then
        x,_,y = Spring.GetUnitPosition(pos)
      elseif Spring.ValidFeatureID(pos) then
        x,_,y = Spring.GetFeaturePosition(pos)
      end
    end
    if x ~= nil and y ~= nil then
      for _,id in pairs(Spring.GetUnitsInCylinder(x,y,rad,Spring.GetMyTeamID())) do -- Here we're skipping the creation of the table altogether in favor of just plugging in the results of 'getunitsincylinder'
        if checked[id] == nil and unittypes[ontype][UnitDefs[Spring.GetUnitDefID(id)].name] and not selected[id] then -- Here we're using LUA's if true or exists logic. This says 'if this unit's unitdefid exists as a value in this table AND it's not a key in selected, then do this. This means units must match on the table and be a unique unit
          if debug then Spring.Echo("game_message: Selected " .. id) end
          selection[#selection+1] = id
          selected[id] = id
        end
        checked[id] = 1
      end
    end
  end
end
end

function widget:KeyRelease(key) -- Called whenever user stops pressing a key.
  if triggerkeys[key] and on then
    on = false
    ontype = "none"
    Spring.SelectUnitArray(selection,false)
    selection = {} -- clear the table.
    selected = {}
    checked = {}
  end
end

function widget:DrawWorld() -- this is used for openGL stuff.
  if on or radchanged then
    local x,y = Spring.GetMouseState()
    local _,pos = Spring.TraceScreenRay(x,y,true)
    x,y = nil
    if type(pos) == "number" then -- prevent crashing from attempting to index a number value. The above seems to give random numbers sometimes.
      if Spring.ValidUnitID(pos) then
        local id = pos
        pos = {}
        pos[1],pos[2],pos[3] = Spring.GetUnitPosition(id)
        id = nil
      elseif Spring.ValidFeatureID(pos) then
        local id = pos
        pos = {}
        pos[1],pos[2],pos[3] = Spring.GetFeaturePosition(id)
      end
    end
    if on then
      if type(pos) == "table" and pos[1] ~= nil and pos[2] ~= nil then
        gl.PushMatrix() --This is the start of an openGL function.
        gl.LineStipple(true)
        gl.LineWidth(3.0)
        gl.Color(color[ontype][1],color[ontype][2],color[ontype][3],1)
        gl.DrawGroundCircle(pos[1], pos[2], pos[3], rad, 40) -- draws a simple circle.
        gl.Translate(pos[1],pos[2],pos[3])
        gl.Billboard()
        gl.Text("Selecting " .. ontype,-25,-25,12,"v") -- Displays text. First value is the string, second is a modifier for x (in this case it's x-25), third is a modifier for y, fourth is the size, then last is a modifier for the text itself. "v" means vertical align.
        gl.Color(1,1,1,1) -- we have to reset what we did here.
        gl.LineWidth(1.0)
        gl.LineStipple(false)
        gl.PopMatrix() -- end of function. Have to use this with after a push!
      end
    end
  if radchanged and not on and type(pos) == "table" and originalrad then
    gl.PushMatrix()
    gl.LineWidth(3.0)
    gl.Color(1,1,1,1)
    gl.DrawGroundCircle(pos[1],pos[2],pos[3],originalrad,40)
    if rad > originalrad then
      gl.Color(color["growth"][1],color["growth"][2],color["growth"][3],1)
    else
      if rad < originalrad then
        gl.Color(color["shrink"][1],color["shrink"][2],color["shrink"][3],1)
      else
        gl.Color(1,1,1,1)
      end
    end
    gl.LineStipple(true)
    gl.DrawGroundCircle(pos[1],pos[2],pos[3],rad,40)
    gl.LineStipple(false)
    gl.Translate(pos[1],pos[2],pos[3])
    gl.Billboard()
    gl.Text("New Radius: " .. rad .. "(Was: " .. originalrad .. ", change:" .. rad-originalrad .. ")",-100,-25,12,"v")
    gl.LineWidth(1.0)
    gl.Color(1,1,1,1)
    gl.PopMatrix()
  end
  pos = nil
end
if #selection > 0 then -- Draw circles around selected units. #tablename is the length of the ordered table (or last consecutive value)
  local pos = {}
    for i=1,#selection do -- do this for every entry in the ordered table. i is the incremental value. i=1 means that the first value is 1. i increases by 1 (or a third value if provided eg 1,5,0.25 would do 1 + 0.25 every execution) with every execution and will continue until i == #selection. i=1,#table is very useful for doing things to every entry in an ordered table.
      if Spring.ValidUnitID(selection[i]) then
        pos[1],pos[2],pos[3] = Spring.GetUnitPosition(selection[i])
        gl.PushMatrix()
        gl.LineWidth(3.0)
        gl.Color(color[ontype][1],color[ontype][2],color[ontype][3],1)
        gl.DrawGroundCircle(pos[1],pos[2],pos[3],40,40)
        gl.Color(1,1,1,1)
        gl.PopMatrix()
      end
    end
  end
end