SELECT 
        device.uuid AS device_id,
        device.space_device_uuid AS space_id,
        -- Mark none_flag if value is 'none'
        CASE 
            WHEN "device-status-log".value = 'none' THEN 1 
            ELSE 0 
        END AS none_flag,
        "device-status-log".event_time::timestamp AS event_time,
        LAG("device-status-log".event_time::timestamp) 
            OVER (PARTITION BY device.uuid  
                  ORDER BY "device-status-log".event_time) AS prev_timestamp,
        LAG(
            CASE 
                WHEN "device-status-log".value = 'none' THEN 1 -- identifies if there was a 'none' flag detected
                ELSE 0 
            END
        ) OVER (PARTITION BY device.uuid  
                ORDER BY "device-status-log".event_time) AS prev_none_flag
    FROM device
    LEFT JOIN "device-status-log"
        ON device.uuid = "device-status-log".device_id
    LEFT JOIN product
        ON product.uuid = device.product_device_uuid
    WHERE product.cat_name = 'hps'
      AND "device-status-log".code = 'presence_state'
    ORDER BY device.uuid, "device-status-log".event_time