--AI parameter constants
AI_THINK_INTERVAL = 0.5

--AI state constants
AI_STATE_IDLE = 0
AI_STATE_AGGRESSIVE = 1
AI_STATE_RETURNING = 2

function Spawn( entityKeyValues )

	--Set the core fields for this AI
	thisEntity.state = AI_STATE_IDLE --The initial state
	thisEntity.stateThinks = { --Add thinking functions for each state
		[AI_STATE_IDLE] = 'IdleThink',
		[AI_STATE_AGGRESSIVE] = 'AggressiveThink',
		[AI_STATE_RETURNING] = 'ReturningThink'
	}

	--Set parameters values as fields for later use
	spawnPos = thisEntity.spawnPos
	aggroRange = 300
	leashRange = 900

	thisEntity:SetContextThink("GreevilThink", GreevilThink, 0.5)
end

function GreevilThink()
	if not thisEntity:IsAlive() then
		return nil
	end

	if thisEntity.state == 0 then
		IdleThink()
	elseif thisEntity.state == 1 then
		AggressiveThink()
	elseif thisEntity.state == 2 then
		ReturningThink()
	end

	return AI_THINK_INTERVAL
end

function IdleThink()
	--Find any enemy units around the AI unit inside the aggroRange
	local units = FindUnitsInRadius( thisEntity:GetTeam(), thisEntity:GetAbsOrigin(), nil,
		aggroRange, DOTA_UNIT_TARGET_TEAM_ENEMY, DOTA_UNIT_TARGET_ALL, DOTA_UNIT_TARGET_FLAG_NONE,
		FIND_ANY_ORDER, false )

	--If one or more units were found, start attacking the first one
	if #units > 0 then
		thisEntity:MoveToTargetToAttack( units[1] ) --Start attacking
		thisEntity.aggroTarget = units[1]
		thisEntity.state = AI_STATE_AGGRESSIVE --State transition
		return true
	end
end

function AggressiveThink()
	--If target leaves leash range
	if ( thisEntity.spawnPos - thisEntity:GetAbsOrigin() ):Length() > thisEntity.leashRange then
		thisEntity:MoveToPosition( thisEntity.spawnPos ) --Move back to the spawnpoint
		thisEntity.state = AI_STATE_RETURNING --Transition the state to the 'Returning' state(!)
		return true --Return to make sure no other code is executed in this state
	end

	--If target dies
	if not thisEntity.aggroTarget:IsAlive() then
		thisEntity:MoveToPosition( thisEntity.spawnPos ) --Move back to the spawnpoint
		thisEntity.state = AI_STATE_RETURNING --Transition the state to the 'Returning' state(!)
		return true --Return to make sure no other code is executed in this state
	end

	-- aggro commands
end

function ReturningThink()
	--Check if the AI unit has reached its spawn location yet
	if ( thisEntity.spawnPos - thisEntity:GetAbsOrigin() ):Length() < 10 then
		--Go into the idle state
		thisEntity.state = AI_STATE_IDLE
		return true
	end
end