global.follows = {}
global.follows.n_entries = 0
local Utils = require 'utils.utils'
local Game = require 'utils.game'

local function get_direction(follower, target)
    local delta_x = target.position.x - follower.position.x
    local delta_y = follower.position.y - target.position.y --reversed x axis
    local a = delta_y / delta_x
    if a >= -1.5 and a < -0.5 then
        --SE OR NW
        if delta_x > 0 then
            return defines.direction.southeast
        else
            return defines.direction.northwest
        end
    elseif a >= -0.5 and a < 0.5 then
        --E OR W
        if delta_x > 0 then
            return defines.direction.east
        else
            return defines.direction.west
        end
    elseif a >= 0.5 and a < 1.5 then
        --NE OR SW
        if delta_x > 0 then
            return defines.direction.northeast
        else
            return defines.direction.southwest
        end
    else
        -- N or S
        if a < 0 then
            delta_x = -delta_x
        end -- mirrow x axis if  player is NNW or SSE
        if delta_x > 0 then
            return defines.direction.north
        else
            return defines.direction.south
        end
    end
end

local function walk_on_tick()
    if global.follows.n_entries > 0 then
        for k, v in pairs(global.follows) do
            local follower = game.playesr[k]
            local target = game.players[v]
            if follower ~= nil and target ~= nil then
                local d = Utils.distance(follower, target)
                if follower.connected and target.connected and d < 32 then
                    if d > 5 then
                        direction = get_direction(follower, target)
                        follower.walking_state = {walking = true, direction = direction}
                    end
                else
                    global.follows[follower.name] = nil
                    global.follows.n_entries = global.follows.n_entries - 1
                end
            end
        end
    end
end