cc-mek-scada/coordinator/coordinator.lua

local comms       = require("scada-common.comms")
local log         = require("scada-common.log")
local ppm         = require("scada-common.ppm")
local util        = require("scada-common.util")
local types       = require("scada-common.types")

local iocontrol   = require("coordinator.iocontrol")
local process     = require("coordinator.process")

local apisessions = require("coordinator.session.apisessions")

local PROTOCOL = comms.PROTOCOL
local DEVICE_TYPE = comms.DEVICE_TYPE
local ESTABLISH_ACK = comms.ESTABLISH_ACK
local MGMT_TYPE = comms.MGMT_TYPE
local CRDN_TYPE = comms.CRDN_TYPE
local UNIT_COMMAND = comms.UNIT_COMMAND
local FAC_COMMAND = comms.FAC_COMMAND

local LINK_TIMEOUT = 60.0

local coordinator = {}

---@type crd_config
local config = {}

coordinator.config = config

-- load the coordinator configuration<br>
-- status of 0 is OK, 1 is bad config, 2 is bad monitor config
---@return 0|1|2 status, nil|monitors_struct|string monitors (or error message)
function coordinator.load_config()
    if not settings.load("/coordinator.settings") then return 1 end

    config.UnitCount = settings.get("UnitCount")
    config.SpeakerVolume = settings.get("SpeakerVolume")
    config.Time24Hour = settings.get("Time24Hour")
    config.TempScale = settings.get("TempScale")

    config.DisableFlowView = settings.get("DisableFlowView")
    config.MainDisplay = settings.get("MainDisplay")
    config.FlowDisplay = settings.get("FlowDisplay")
    config.UnitDisplays = settings.get("UnitDisplays")

    config.SVR_Channel = settings.get("SVR_Channel")
    config.CRD_Channel = settings.get("CRD_Channel")
    config.PKT_Channel = settings.get("PKT_Channel")
    config.SVR_Timeout = settings.get("SVR_Timeout")
    config.API_Timeout = settings.get("API_Timeout")
    config.TrustedRange = settings.get("TrustedRange")
    config.AuthKey = settings.get("AuthKey")

    config.LogMode = settings.get("LogMode")
    config.LogPath = settings.get("LogPath")
    config.LogDebug = settings.get("LogDebug")

    config.MainTheme = settings.get("MainTheme")
    config.FrontPanelTheme = settings.get("FrontPanelTheme")
    config.ColorMode = settings.get("ColorMode")

    local cfv = util.new_validator()

    cfv.assert_type_int(config.UnitCount)
    cfv.assert_range(config.UnitCount, 1, 4)
    cfv.assert_type_bool(config.Time24Hour)
    cfv.assert_type_int(config.TempScale)
    cfv.assert_range(config.TempScale, 1, 4)

    cfv.assert_type_bool(config.DisableFlowView)
    cfv.assert_type_table(config.UnitDisplays)

    cfv.assert_type_num(config.SpeakerVolume)
    cfv.assert_range(config.SpeakerVolume, 0, 3)

    cfv.assert_channel(config.SVR_Channel)
    cfv.assert_channel(config.CRD_Channel)
    cfv.assert_channel(config.PKT_Channel)

    cfv.assert_type_num(config.SVR_Timeout)
    cfv.assert_min(config.SVR_Timeout, 2)
    cfv.assert_type_num(config.API_Timeout)
    cfv.assert_min(config.API_Timeout, 2)

    cfv.assert_type_num(config.TrustedRange)
    cfv.assert_min(config.TrustedRange, 0)
    cfv.assert_type_str(config.AuthKey)

    if type(config.AuthKey) == "string" then
        local len = string.len(config.AuthKey)
        cfv.assert_eq(len == 0 or len >= 8, true)
    end

    cfv.assert_type_int(config.LogMode)
    cfv.assert_range(config.LogMode, 0, 1)
    cfv.assert_type_str(config.LogPath)
    cfv.assert_type_bool(config.LogDebug)

    cfv.assert_type_int(config.MainTheme)
    cfv.assert_range(config.MainTheme, 1, 2)
    cfv.assert_type_int(config.FrontPanelTheme)
    cfv.assert_range(config.FrontPanelTheme, 1, 2)
    cfv.assert_type_int(config.ColorMode)
    cfv.assert_range(config.ColorMode, 1, 4)

    -- Monitor Setup

    ---@class monitors_struct
    local monitors = {
        main = nil,     ---@type table|nil
        main_name = "",
        flow = nil,     ---@type table|nil
        flow_name = "",
        unit_displays = {},
        unit_name_map = {}
    }

    local mon_cfv = util.new_validator()

    -- get all interface names
    local names = {}
    for iface, _ in pairs(ppm.get_monitor_list()) do table.insert(names, iface) end

    local function setup_monitors()
        mon_cfv.assert_type_str(config.MainDisplay)
        if not config.DisableFlowView then mon_cfv.assert_type_str(config.FlowDisplay) end
        mon_cfv.assert_eq(#config.UnitDisplays, config.UnitCount)

        if mon_cfv.valid() then
            local w, h, _

            if not util.table_contains(names, config.MainDisplay) then
                return 2, "Main monitor is not connected."
            end

            monitors.main = ppm.get_periph(config.MainDisplay)
            monitors.main_name = config.MainDisplay

            monitors.main.setTextScale(0.5)
            w, _ = ppm.monitor_block_size(monitors.main.getSize())
            if w ~= 8 then
                return 2, util.c("Main monitor width is incorrect (was ", w, ", must be 8).")
            end

            if not config.DisableFlowView then
                if not util.table_contains(names, config.FlowDisplay) then
                    return 2, "Flow monitor is not connected."
                end

                monitors.flow = ppm.get_periph(config.FlowDisplay)
                monitors.flow_name = config.FlowDisplay

                monitors.flow.setTextScale(0.5)
                w, _ = ppm.monitor_block_size(monitors.flow.getSize())
                if w ~= 8 then
                    return 2, util.c("Flow monitor width is incorrect (was ", w, ", must be 8).")
                end
            end

            for i = 1, config.UnitCount do
                local display = config.UnitDisplays[i]
                if type(display) ~= "string" or not util.table_contains(names, display) then
                    return 2, "Unit " .. i .. " monitor is not connected."
                end

                monitors.unit_displays[i] = ppm.get_periph(display)
                monitors.unit_name_map[i] = display

                monitors.unit_displays[i].setTextScale(0.5)
                w, h = ppm.monitor_block_size(monitors.unit_displays[i].getSize())
                if w ~= 4 or h ~= 4 then
                    return 2, util.c("Unit ", i, " monitor size is incorrect (was ", w, " by ", h,", must be 4 by 4).")
                end
            end
        else return 2, "Monitor configuration invalid." end
    end

    if cfv.valid() then
        local ok, result, message = pcall(setup_monitors)
        assert(ok, util.c("fatal error while trying to verify monitors: ", result))
        if result == 2 then return 2, message end
    else return 1 end

    return 0, monitors
end

-- dmesg print wrapper
---@param message string message
---@param dmesg_tag string tag
---@param working? boolean to use dmesg_working
---@return function? update, function? done
local function log_dmesg(message, dmesg_tag, working)
    local colors = {
        GRAPHICS = colors.green,
        SYSTEM = colors.cyan,
        BOOT = colors.blue,
        COMMS = colors.purple,
        CRYPTO = colors.yellow
    }

    if working then
        return log.dmesg_working(message, dmesg_tag, colors[dmesg_tag])
    else
        log.dmesg(message, dmesg_tag, colors[dmesg_tag])
    end
end

function coordinator.log_graphics(message) log_dmesg(message, "GRAPHICS") end
function coordinator.log_sys(message) log_dmesg(message, "SYSTEM") end
function coordinator.log_boot(message) log_dmesg(message, "BOOT") end
function coordinator.log_comms(message) log_dmesg(message, "COMMS") end
function coordinator.log_crypto(message) log_dmesg(message, "CRYPTO") end

-- log a message for communications connecting, providing access to progress indication control functions
---@nodiscard
---@param message string
---@return function update, function done
function coordinator.log_comms_connecting(message)
    local update, done = log_dmesg(message, "COMMS", true)
    ---@cast update function
    ---@cast done function
    return update, done
end

-- coordinator communications
---@nodiscard
---@param version string coordinator version
---@param nic nic network interface device
---@param sv_watchdog watchdog
function coordinator.comms(version, nic, sv_watchdog)
    local self = {
        sv_linked = false,
        sv_addr = comms.BROADCAST,
        sv_seq_num = 0,
        sv_r_seq_num = nil,
        sv_config_err = false,
        last_est_ack = ESTABLISH_ACK.ALLOW,
        last_api_est_acks = {},
        est_start = 0,
        est_last = 0,
        est_tick_waiting = nil,
        est_task_done = nil
    }

    comms.set_trusted_range(config.TrustedRange)

    -- configure network channels
    nic.closeAll()
    nic.open(config.CRD_Channel)

    -- pass config to apisessions
    apisessions.init(nic, config)

    -- PRIVATE FUNCTIONS --

    -- send a packet to the supervisor
    ---@param msg_type MGMT_TYPE|CRDN_TYPE
    ---@param msg table
    local function _send_sv(protocol, msg_type, msg)
        local s_pkt = comms.scada_packet()
        local pkt   ---@type mgmt_packet|crdn_packet

        if protocol == PROTOCOL.SCADA_MGMT then
            pkt = comms.mgmt_packet()
        elseif protocol == PROTOCOL.SCADA_CRDN then
            pkt = comms.crdn_packet()
        else
            return
        end

        pkt.make(msg_type, msg)
        s_pkt.make(self.sv_addr, self.sv_seq_num, protocol, pkt.raw_sendable())

        nic.transmit(config.SVR_Channel, config.CRD_Channel, s_pkt)
        self.sv_seq_num = self.sv_seq_num + 1
    end

    -- send an API establish request response
    ---@param packet scada_packet
    ---@param ack ESTABLISH_ACK
    local function _send_api_establish_ack(packet, ack)
        local s_pkt = comms.scada_packet()
        local m_pkt = comms.mgmt_packet()

        m_pkt.make(MGMT_TYPE.ESTABLISH, { ack })
        s_pkt.make(packet.src_addr(), packet.seq_num() + 1, PROTOCOL.SCADA_MGMT, m_pkt.raw_sendable())

        nic.transmit(config.PKT_Channel, config.CRD_Channel, s_pkt)
        self.last_api_est_acks[packet.src_addr()] = ack
    end

    -- attempt connection establishment
    local function _send_establish()
        _send_sv(PROTOCOL.SCADA_MGMT, MGMT_TYPE.ESTABLISH, { comms.version, version, DEVICE_TYPE.CRD })
    end

    -- keep alive ack
    ---@param srv_time integer
    local function _send_keep_alive_ack(srv_time)
        _send_sv(PROTOCOL.SCADA_MGMT, MGMT_TYPE.KEEP_ALIVE, { srv_time, util.time() })
    end

    -- PUBLIC FUNCTIONS --

    ---@class coord_comms
    local public = {}

    -- try to connect to the supervisor if not already linked
    ---@param abort boolean? true to print out cancel info if not linked (use on program terminate)
    ---@return boolean ok, boolean start_ui
    function public.try_connect(abort)
        local ok = true
        local start_ui = false

        if not self.sv_linked then
            if self.est_tick_waiting == nil then
                self.est_start = os.clock()
                self.est_last = self.est_start

                self.est_tick_waiting, self.est_task_done =
                    coordinator.log_comms_connecting("attempting to connect to configured supervisor on channel " .. config.SVR_Channel)

                _send_establish()
            else
                self.est_tick_waiting(math.max(0, LINK_TIMEOUT - (os.clock() - self.est_start)))
            end

            if abort or (os.clock() - self.est_start) >= LINK_TIMEOUT then
                self.est_task_done(false)

                if abort then
                    coordinator.log_comms("supervisor connection attempt cancelled by user")
                elseif self.sv_config_err then
                    coordinator.log_comms("supervisor unit count does not match coordinator unit count, check configs")
                elseif not self.sv_linked then
                    if self.last_est_ack == ESTABLISH_ACK.DENY then
                        coordinator.log_comms("supervisor connection attempt denied")
                    elseif self.last_est_ack == ESTABLISH_ACK.COLLISION then
                        coordinator.log_comms("supervisor connection failed due to collision")
                    elseif self.last_est_ack == ESTABLISH_ACK.BAD_VERSION then
                        coordinator.log_comms("supervisor connection failed due to version mismatch")
                    else
                        coordinator.log_comms("supervisor connection failed with no valid response")
                    end
                end

                ok = false
            elseif self.sv_config_err then
                coordinator.log_comms("supervisor unit count does not match coordinator unit count, check configs")
                ok = false
            elseif (os.clock() - self.est_last) > 1.0 then
                _send_establish()
                self.est_last = os.clock()
            end
        elseif self.est_tick_waiting ~= nil then
            self.est_task_done(true)
            self.est_tick_waiting = nil
            self.est_task_done = nil
            start_ui = true
        end

        return ok, start_ui
    end

    -- close the connection to the server
    function public.close()
        sv_watchdog.cancel()
        self.sv_addr = comms.BROADCAST
        self.sv_linked = false
        self.sv_r_seq_num = nil
        iocontrol.fp_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
        _send_sv(PROTOCOL.SCADA_MGMT, MGMT_TYPE.CLOSE, {})
    end

    -- send a facility command
    ---@param cmd FAC_COMMAND command
    ---@param option any? optional option options for the optional options (like waste mode)
    function public.send_fac_command(cmd, option)
        _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.FAC_CMD, { cmd, option })
    end

    -- send the auto process control configuration with a start command
    ---@param auto_cfg coord_auto_config configuration
    function public.send_auto_start(auto_cfg)
        _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.FAC_CMD, {
            FAC_COMMAND.START, auto_cfg.mode, auto_cfg.burn_target, auto_cfg.charge_target, auto_cfg.gen_target, auto_cfg.limits
        })
    end

    -- send a unit command
    ---@param cmd UNIT_COMMAND command
    ---@param unit integer unit ID
    ---@param option any? optional option options for the optional options (like burn rate)
    function public.send_unit_command(cmd, unit, option)
        _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.UNIT_CMD, { cmd, unit, option })
    end

    -- parse a packet
    ---@param side string
    ---@param sender integer
    ---@param reply_to integer
    ---@param message any
    ---@param distance integer
    ---@return mgmt_frame|crdn_frame|nil packet
    function public.parse_packet(side, sender, reply_to, message, distance)
        local s_pkt = nic.receive(side, sender, reply_to, message, distance)
        local pkt = nil

        if s_pkt then
            -- get as SCADA management packet
            if s_pkt.protocol() == PROTOCOL.SCADA_MGMT then
                local mgmt_pkt = comms.mgmt_packet()
                if mgmt_pkt.decode(s_pkt) then
                    pkt = mgmt_pkt.get()
                end
            -- get as coordinator packet
            elseif s_pkt.protocol() == PROTOCOL.SCADA_CRDN then
                local crdn_pkt = comms.crdn_packet()
                if crdn_pkt.decode(s_pkt) then
                    pkt = crdn_pkt.get()
                end
            else
                log.debug("attempted parse of illegal packet type " .. s_pkt.protocol(), true)
            end
        end

        return pkt
    end

    -- handle a packet
    ---@param packet mgmt_frame|crdn_frame|nil
    ---@return boolean close_ui
    function public.handle_packet(packet)
        local was_linked = self.sv_linked

        if packet ~= nil then
            local l_chan = packet.scada_frame.local_channel()
            local r_chan = packet.scada_frame.remote_channel()
            local src_addr = packet.scada_frame.src_addr()
            local protocol = packet.scada_frame.protocol()

            if l_chan ~= config.CRD_Channel then
                log.debug("received packet on unconfigured channel " .. l_chan, true)
            elseif r_chan == config.PKT_Channel then
                if not self.sv_linked then
                    log.debug("discarding pocket API packet before linked to supervisor")
                elseif protocol == PROTOCOL.SCADA_CRDN then
                    ---@cast packet crdn_frame
                    -- look for an associated session
                    local session = apisessions.find_session(src_addr)

                    -- coordinator packet
                    if session ~= nil then
                        -- pass the packet onto the session handler
                        session.in_queue.push_packet(packet)
                    else
                        -- any other packet should be session related, discard it
                        log.debug("discarding SCADA_CRDN packet without a known session")
                    end
                elseif protocol == PROTOCOL.SCADA_MGMT then
                    ---@cast packet mgmt_frame
                    -- look for an associated session
                    local session = apisessions.find_session(src_addr)

                    -- SCADA management packet
                    if session ~= nil then
                        -- pass the packet onto the session handler
                        session.in_queue.push_packet(packet)
                    elseif packet.type == MGMT_TYPE.ESTABLISH then
                        -- establish a new session
                        -- validate packet and continue
                        if packet.length == 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
                            local comms_v = packet.data[1]
                            local firmware_v = packet.data[2]
                            local dev_type = packet.data[3]

                            if comms_v ~= comms.version then
                                if self.last_api_est_acks[src_addr] ~= ESTABLISH_ACK.BAD_VERSION then
                                    log.info(util.c("dropping API establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
                                end

                                _send_api_establish_ack(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
                            elseif dev_type == DEVICE_TYPE.PKT then
                                -- pocket linking request
                                local id = apisessions.establish_session(src_addr, firmware_v)
                                coordinator.log_comms(util.c("API_ESTABLISH: pocket (", firmware_v, ") [@", src_addr, "] connected with session ID ", id))

                                _send_api_establish_ack(packet.scada_frame, ESTABLISH_ACK.ALLOW)
                            else
                                log.debug(util.c("API_ESTABLISH: illegal establish packet for device ", dev_type, " on pocket channel"))
                                _send_api_establish_ack(packet.scada_frame, ESTABLISH_ACK.DENY)
                            end
                        else
                            log.debug("invalid establish packet (on API listening channel)")
                            _send_api_establish_ack(packet.scada_frame, ESTABLISH_ACK.DENY)
                        end
                    else
                        -- any other packet should be session related, discard it
                        log.debug(util.c("discarding pocket SCADA_MGMT packet without a known session from computer ", src_addr))
                    end
                else
                    log.debug("illegal packet type " .. protocol .. " on pocket channel", true)
                end
            elseif r_chan == config.SVR_Channel then
                -- check sequence number
                if self.sv_r_seq_num == nil then
                    self.sv_r_seq_num = packet.scada_frame.seq_num()
                elseif self.sv_linked and ((self.sv_r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
                    log.warning("sequence out-of-order: last = " .. self.sv_r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
                    return false
                elseif self.sv_linked and src_addr ~= self.sv_addr then
                    log.debug("received packet from unknown computer " .. src_addr .. " while linked; channel in use by another system?")
                    return false
                else
                    self.sv_r_seq_num = packet.scada_frame.seq_num()
                end

                -- feed watchdog on valid sequence number
                sv_watchdog.feed()

                -- handle packet
                if protocol == PROTOCOL.SCADA_CRDN then
                    ---@cast packet crdn_frame
                    if self.sv_linked then
                        if packet.type == CRDN_TYPE.INITIAL_BUILDS then
                            if packet.length == 2 then
                                -- record builds
                                local fac_builds = iocontrol.record_facility_builds(packet.data[1])
                                local unit_builds = iocontrol.record_unit_builds(packet.data[2])

                                if fac_builds and unit_builds then
                                    -- acknowledge receipt of builds
                                    _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.INITIAL_BUILDS, {})
                                else
                                    log.debug("received invalid INITIAL_BUILDS packet")
                                end
                            else
                                log.debug("INITIAL_BUILDS packet length mismatch")
                            end
                        elseif packet.type == CRDN_TYPE.FAC_BUILDS then
                            if packet.length == 1 then
                                -- record facility builds
                                if iocontrol.record_facility_builds(packet.data[1]) then
                                    -- acknowledge receipt of builds
                                    _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.FAC_BUILDS, {})
                                else
                                    log.debug("received invalid FAC_BUILDS packet")
                                end
                            else
                                log.debug("FAC_BUILDS packet length mismatch")
                            end
                        elseif packet.type == CRDN_TYPE.FAC_STATUS then
                            -- update facility status
                            if not iocontrol.update_facility_status(packet.data) then
                                log.debug("received invalid FAC_STATUS packet")
                            end
                        elseif packet.type == CRDN_TYPE.FAC_CMD then
                            -- facility command acknowledgement
                            if packet.length >= 2 then
                                local cmd = packet.data[1]
                                local ack = packet.data[2] == true

                                if cmd == FAC_COMMAND.SCRAM_ALL then
                                    iocontrol.get_db().facility.scram_ack(ack)
                                elseif cmd == FAC_COMMAND.STOP then
                                    iocontrol.get_db().facility.stop_ack(ack)
                                elseif cmd == FAC_COMMAND.START then
                                    if packet.length == 7 then
                                        process.start_ack_handle({ table.unpack(packet.data, 2) })
                                    else
                                        log.debug("SCADA_CRDN process start (with configuration) ack echo packet length mismatch")
                                    end
                                elseif cmd == FAC_COMMAND.ACK_ALL_ALARMS then
                                    iocontrol.get_db().facility.ack_alarms_ack(ack)
                                elseif cmd == FAC_COMMAND.SET_WASTE_MODE then
                                    process.waste_ack_handle(packet.data[2])
                                elseif cmd == FAC_COMMAND.SET_PU_FB then
                                    process.pu_fb_ack_handle(packet.data[2])
                                else
                                    log.debug(util.c("received facility command ack with unknown command ", cmd))
                                end
                            else
                                log.debug("SCADA_CRDN facility command ack packet length mismatch")
                            end
                        elseif packet.type == CRDN_TYPE.UNIT_BUILDS then
                            -- record builds
                            if packet.length == 1 then
                                if iocontrol.record_unit_builds(packet.data[1]) then
                                    -- acknowledge receipt of builds
                                    _send_sv(PROTOCOL.SCADA_CRDN, CRDN_TYPE.UNIT_BUILDS, {})
                                else
                                    log.debug("received invalid UNIT_BUILDS packet")
                                end
                            else
                                log.debug("UNIT_BUILDS packet length mismatch")
                            end
                        elseif packet.type == CRDN_TYPE.UNIT_STATUSES then
                            -- update statuses
                            if not iocontrol.update_unit_statuses(packet.data) then
                                log.debug("received invalid UNIT_STATUSES packet")
                            end
                        elseif packet.type == CRDN_TYPE.UNIT_CMD then
                            -- unit command acknowledgement
                            if packet.length == 3 then
                                local cmd = packet.data[1]
                                local unit_id = packet.data[2]
                                local ack = packet.data[3] == true

                                local unit = iocontrol.get_db().units[unit_id]  ---@type ioctl_unit

                                if unit ~= nil then
                                    if cmd == UNIT_COMMAND.SCRAM then
                                        unit.scram_ack(ack)
                                    elseif cmd == UNIT_COMMAND.START then
                                        unit.start_ack(ack)
                                    elseif cmd == UNIT_COMMAND.RESET_RPS then
                                        unit.reset_rps_ack(ack)
                                    elseif cmd == UNIT_COMMAND.SET_BURN then
                                        unit.set_burn_ack(ack)
                                    elseif cmd == UNIT_COMMAND.SET_WASTE then
                                        unit.set_waste_ack(ack)
                                    elseif cmd == UNIT_COMMAND.ACK_ALL_ALARMS then
                                        unit.ack_alarms_ack(ack)
                                    elseif cmd == UNIT_COMMAND.SET_GROUP then
                                        -- UI will be updated to display current group if changed successfully
                                    else
                                        log.debug(util.c("received unit command ack with unknown command ", cmd))
                                    end
                                else
                                    log.debug(util.c("received unit command ack with unknown unit ", unit_id))
                                end
                            else
                                log.debug("SCADA_CRDN unit command ack packet length mismatch")
                            end
                        else
                            log.debug("received unknown SCADA_CRDN packet type " .. packet.type)
                        end
                    else
                        log.debug("discarding SCADA_CRDN packet before linked")
                    end
                elseif protocol == PROTOCOL.SCADA_MGMT then
                    ---@cast packet mgmt_frame
                    if self.sv_linked then
                        if packet.type == MGMT_TYPE.KEEP_ALIVE then
                            -- keep alive request received, echo back
                            if packet.length == 1 then
                                local timestamp = packet.data[1]
                                local trip_time = util.time() - timestamp

                                if trip_time > 750 then
                                    log.warning("coordinator KEEP_ALIVE trip time > 750ms (" .. trip_time .. "ms)")
                                end

                                -- log.debug("coordinator RTT = " .. trip_time .. "ms")

                                iocontrol.get_db().facility.ps.publish("sv_ping", trip_time)

                                _send_keep_alive_ack(timestamp)
                            else
                                log.debug("SCADA keep alive packet length mismatch")
                            end
                        elseif packet.type == MGMT_TYPE.CLOSE then
                            -- handle session close
                            sv_watchdog.cancel()
                            self.sv_addr = comms.BROADCAST
                            self.sv_linked = false
                            self.sv_r_seq_num = nil
                            iocontrol.fp_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
                            log.info("server connection closed by remote host")
                        else
                            log.debug("received unknown SCADA_MGMT packet type " .. packet.type)
                        end
                    elseif packet.type == MGMT_TYPE.ESTABLISH then
                        -- connection with supervisor established
                        if packet.length == 2 then
                            local est_ack = packet.data[1]
                            local sv_config = packet.data[2]

                            if est_ack == ESTABLISH_ACK.ALLOW then
                                -- reset to disconnected before validating
                                iocontrol.fp_link_state(types.PANEL_LINK_STATE.DISCONNECTED)

                                if type(sv_config) == "table" and #sv_config == 2 then
                                    -- get configuration

                                    ---@class facility_conf
                                    local conf = {
                                        num_units = sv_config[1], ---@type integer
                                        cooling = sv_config[2]    ---@type sv_cooling_conf
                                    }

                                    if conf.num_units == config.UnitCount then
                                        -- init io controller
                                        iocontrol.init(conf, public, config.TempScale)

                                        self.sv_addr = src_addr
                                        self.sv_linked = true
                                        self.sv_r_seq_num = nil
                                        self.sv_config_err = false

                                        iocontrol.fp_link_state(types.PANEL_LINK_STATE.LINKED)
                                    else
                                        self.sv_config_err = true
                                        log.warning("supervisor config's number of units don't match coordinator's config, establish failed")
                                    end
                                else
                                    log.debug("invalid supervisor configuration table received, establish failed")
                                end
                            else
                                log.debug("SCADA_MGMT establish packet reply (len = 2) unsupported")
                            end

                            self.last_est_ack = est_ack
                        elseif packet.length == 1 then
                            local est_ack = packet.data[1]

                            if est_ack == ESTABLISH_ACK.DENY then
                                if self.last_est_ack ~= est_ack then
                                    iocontrol.fp_link_state(types.PANEL_LINK_STATE.DENIED)
                                    log.info("supervisor connection denied")
                                end
                            elseif est_ack == ESTABLISH_ACK.COLLISION then
                                if self.last_est_ack ~= est_ack then
                                    iocontrol.fp_link_state(types.PANEL_LINK_STATE.COLLISION)
                                    log.warning("supervisor connection denied due to collision")
                                end
                            elseif est_ack == ESTABLISH_ACK.BAD_VERSION then
                                if self.last_est_ack ~= est_ack then
                                    iocontrol.fp_link_state(types.PANEL_LINK_STATE.BAD_VERSION)
                                    log.warning("supervisor comms version mismatch")
                                end
                            else
                                log.debug("SCADA_MGMT establish packet reply (len = 1) unsupported")
                            end

                            self.last_est_ack = est_ack
                        else
                            log.debug("SCADA_MGMT establish packet length mismatch")
                        end
                    else
                        log.debug("discarding non-link SCADA_MGMT packet before linked")
                    end
                else
                    log.debug("illegal packet type " .. protocol .. " on supervisor listening channel", true)
                end
            else
                log.debug("received packet for unknown channel " .. r_chan, true)
            end
        end

        return was_linked and not self.sv_linked
    end

    -- check if the coordinator is still linked to the supervisor
    ---@nodiscard
    function public.is_linked() return self.sv_linked end

    return public
end

return coordinator