source: Lua/scripts/universe.lua @ 76

-- Use this script for a solar system

-- Lua Global variables
shipList = {}  -- The ships that Lua has access to.  TODO: This list should probably be generated at each tick from a c++ call.
frozen=0 -- Setting this to 1 causes all AI to stop 'thinking' and just drift.
ticks=0
player  = Epiar.player()
shipList[0] = player
it_countdown=100

function CreateShips(number_of_ships, X, Y)
        -- Generate Ships
        for s =1,number_of_ships do
                io.write("Creating Ship ",s)
                cur_ship = EpiarLua.Ship:new(
                                math.random(1000)-500+X, -- X
                                math.random(1000)-500+Y, -- Y
                                "Terran FV-5 Frigate", -- Ship Model
                                "chase"                 -- Ship Script
                                )
                table.insert(shipList, cur_ship )
        end

        io.write("Ships Total: ", #shipList ,"\n")
end

function SwarmAverage()
        -- Find the swarm center
        avg_x,avg_y = 0,0
        avg_angle = 0
        avg_vector= 0
        avg_speed = 0
        for s =1,#shipList do
                cur_ship = shipList[s]
                x,y = EpiarLua.Ship.GetPosition(cur_ship)
                avg_x = avg_x + x
                avg_y = avg_y + y
                angle = EpiarLua.Ship.GetAngle(cur_ship)
                vec   = EpiarLua.Ship.GetMomentumAngle(cur_ship)
                speed = EpiarLua.Ship.GetMomentumSpeed(cur_ship)
                avg_angle = avg_angle + angle
                avg_vector= avg_vector+ vec
                avg_speed = avg_speed + speed
        end
        avg_x = avg_x / #shipList
        avg_y = avg_y / #shipList
        avg_angle = avg_angle / #shipList
        avg_vector = avg_vector / #shipList
        avg_speed = avg_speed / #shipList
    return avg_x,avg_y,avg_angle,avg_vector,avg_speed
end

function distfrom( pt1_x,pt1_y, pt2_x,pt2_y)
        x_diff = (pt1_x - pt2_x)
        y_diff = pt1_y - pt2_y
        return math.sqrt(x_diff*x_diff + y_diff*y_diff)
end

function closestToIT()
        target=-1
        mindist = 100000
        min_x,min_y = 10000,10000
        it_x,it_y = EpiarLua.Ship.GetPosition(shipList[it])

        -- Find the closest ship to whomever is IT
        for other=0, #shipList do 
                if not(other == it) then
                        other_x,other_y = EpiarLua.Ship.GetPosition(shipList[other])
                        dist = distfrom(other_x,other_y,it_x,it_y)
                        if dist < mindist then
                                target = other
                                mindist = dist
                                min_x,min_y = other_x,other_y
                        end
                end
        end
        return target, min_x, min_y, mindist
end


-- The C++ engine calls this function once per tick.
-- This function is responsible for directing all of the game AI.
function Update ()
        if frozen>0 then
                return 1
        end


        avg_x,avg_y,avg_angle,avg_vector,avg_speed = SwarmAverage()

        player_x,player_y = EpiarLua.Ship.GetPosition(player)
        it_x,it_y = EpiarLua.Ship.GetPosition(shipList[it])

        -- Move
        for s =1, # shipList do
                cur_ship = shipList[s]
                x,y = EpiarLua.Ship.GetPosition(cur_ship)

                if s == it then -- IT
                        dir_closest = EpiarLua.Ship.directionTowards(cur_ship, min_x,min_y) -- direction towards the closest target
                        EpiarLua.Ship.Rotate(cur_ship, dir_closest)
                else -- Not IT
                        if math.sqrt(x*x + y*y) >3000 then 
                                dir_center = EpiarLua.Ship.directionTowards(cur_ship, 0,0) -- direction towards the center of the universe
                                EpiarLua.Ship.Rotate(cur_ship, dir_center)
                        else
                                if math.random(100) <10 then
                                        dir_it = EpiarLua.Ship.directionTowards(cur_ship, it_x, it_y) -- direction towards the ship that is IT
                                        EpiarLua.Ship.Rotate(cur_ship, dir_it)
                                elseif math.random(100) <40 then
                                        dir_it = EpiarLua.Ship.directionTowards(cur_ship, it_x, it_y) -- direction away from the ship that is IT
                                        EpiarLua.Ship.Rotate(cur_ship, -dir_it)
                                elseif math.random(100) <70 then
                                        dir_swarm_center = EpiarLua.Ship.directionTowards(cur_ship, avg_x, avg_y) -- direction towards the center of the swarm
                                        EpiarLua.Ship.Rotate(cur_ship, dir_swarm_center)
                                else
                                        dir_swarm_aim = EpiarLua.Ship.directionTowards(cur_ship, avg_angle ) -- direction towards the swarm direction
                                        EpiarLua.Ship.Rotate(cur_ship, dir_swarm_aim)
                                end
                        end

                end
                EpiarLua.Ship.Accelerate(cur_ship )
        end

        if it_countdown==0 then
                -- Is someone else it now?
                target, min_x, min_y, mindist = closestToIT()
                if mindist < 200 then 
                        setIt(target)
                end
        else
                it_countdown= it_countdown-1
                if it_countdown==0 then
                        Epiar.echo("Let the games begin")
                elseif it_countdown%10==0 then
                        Epiar.echo("Player "..it.." is counting down: "..it_countdown/10)
                end
        end

end

-- Functions to use from the console. ( Enter the console by hitting backtick. )
-- TODO: Remove these functions, they are only interesting for debugging and even very useful then.
function stop()
        frozen=1
end

function go()
        frozen=0
end

function open(x,y,w,h,someString) -- Create an Arbitrary Window
        EpiarLua.UI:newWindow(x,y,w,h,someString)
end

function close() -- Close all the windows
        EpiarLua.UI:close()
end

-- Tag Functions
function setIt(target)
        it=target
        it_countdown = 100
        if it==0 then
        Epiar.echo("TAG!  You're now it!")
        --pauseMessage("TAG!  You're now it!")
        else
        Epiar.echo("Ship "..target.." is now IT.")
        --pauseMessage("Ship "..target.." is now IT.")
        end
end
function whosit()
        if it==0 then
                Epiar.echo("You are it")
        else
                Epiar.echo("Player "..it.." is it.")
        end
end
function whosClosest()
        it_x,it_y = EpiarLua.Ship.GetPosition(shipList[it])
        target, min_x, min_y, mindist = closestToIT()
        Epiar.echo("Closest ship to IT "..it.." at ("..it_x..","..it_y..") is ".. target.." at ("..min_x..","..min_y..") "..mindist)
end

function pauseMessage(message)
        Epiar.pause()
        menuWin = EpiarLua.UI:newWindow( 900,200,120,250,"Paused",
                EpiarLua.UI:newLabel(10,40,message),
                EpiarLua.UI:newButton(10,90,100,30,"Unpause","Epiar.unpause()")
                )
end

function menu() -- Generate a test window
        -- Create windows
        menuWin = EpiarLua.UI:newWindow( 900,200,120,450,"Menu",
                EpiarLua.UI:newButton(10,40,100,30,"Pause","Epiar.pause()"),
                EpiarLua.UI:newButton(10,90,100,30,"Unpause","Epiar.unpause()"),
                EpiarLua.UI:newButton(10,140,100,30,"AI Drift","stop()"),
                EpiarLua.UI:newButton(10,190,100,30,"AI Think","go()"),
                EpiarLua.UI:newButton(10,240,100,30,"IT","setIt(0)"),
                EpiarLua.UI:newButton(10,290,100,30,"NOT IT","setIt(math.random(#shipList))")
                )
end
        
-- Create Some ships around the planets
-- TODO, Lua should create these ships based off of information found in the planets-default.xml
if 1 >0 then
        CreateShips(3,345,215)
        CreateShips(6,-40,-135)
        CreateShips(6,4640,-735)
end
it=math.random(#shipList)
it=0