local players_in_safe_zone = {}

local function on_player_enter_zone(ply)
    ply:PrintMessage(HUD_PRINTCENTER, "You're entered safe zone.")
end

local function on_player_leave_zone(ply)
    ply:PrintMessage(HUD_PRINTCENTER, "You're exited safe zone.")
end

hook.Add("Think", "PRocessSafeZone", function()
    local objs = ents.FindInBox(Vector (1065.9262695312, 867.20977783203, -227.98264312744),
        Vector (659.12377929688, -907.02008056641, 72.916381835938))
    for i = 1, #objs do
        if not objs[i]:IsPlayer() then
            if objs[i]:GetClass():find("prop_physics") then
                objs[i]:Remove()
            end
        else
            if not players_in_safe_zone[objs[i]] then
                players_in_safe_zone[objs[i]] = true
                on_player_enter_zone(objs[i])
            end
        end
    end
    for ply in pairs(players_in_safe_zone) do
        local found = false
        for i = 1, #objs do
            if objs[i] == ply then
                found = true
                break
            end
        end
        if not found then
            on_player_leave_zone(ply)
            players_in_safe_zone[ply] = nil
        end
    end
end)

hook.Add("EntityTakeDamage", "SafeZone", function(ent, dmgInfo)
    if players_in_safe_zone[dmgInfo:GetAttacker()]
            or players_in_safe_zone[ent] then
        dmgInfo:SetDamage(0)
    end
    return dmgInfo
end)