--[[
    client2server-luv - TRUE event-driven using ubus events
    
    Features:
    - NO POLLING - reacts to EVENTS only
    - ubus event subscription for DHCP, network, WiFi
    - Uses luv for async event loop
    - State management for change detection
    
    Copyright (c) 2026 Luis Rosales - MIT License
]]

-- ============================================================================
-- REQUIREMENTS
-- ============================================================================

local luv_ok, luv = pcall(require, "luv")

-- ============================================================================
-- CONFIG
-- ============================================================================

local cfg = {
    server_url = os.getenv("SERVER_URL") or "http://163.245.193.47:3843",
    router_id = os.getenv("ROUTER_ID") or "unknown",
    state_file = "/tmp/client2server_state",
    dhcp_lease_file = "/var/lib/dnsmasq/dnsmasq.leases",
}

-- ============================================================================
-- UTILITIES
-- ============================================================================

local function log_info(msg)
    os.execute('logger -t client2server -p user.info "' .. msg .. '"')
end

local function http_post(event_type, data)
    local json = '{"router_id":"' .. cfg.router_id .. '","event":"' .. event_type .. '","data":' .. data .. '}'
    local f = io.popen("curl -s -X POST '" .. cfg.server_url .. "/api/events' -H 'Content-Type: application/json' -d '" .. json .. "'", "r")
    local result = f:read("*a")
    f:close()
    return result
end

local function is_valid_mac(mac)
    if not mac or #mac ~= 17 then return false end
    local parts = {}
    for part in mac:gmatch("[a-fA-F0-9][a-fA-F0-9]") do
        table.insert(parts, part)
    end
    if #parts ~= 6 then return false end
    local first = tonumber(parts[1], 16)
    if first == 0 or first == 255 then return false end
    local second = tonumber(parts[2], 16)
    if second == 255 then return false end
    return true
end

local function send_event(event_type, data)
    log_info("Event: " .. event_type)
    local resp = http_post(event_type, data)
    if resp and resp:match("OK") then
        log_info("OK")
    else
        log_info("Fail: " .. (resp or "nil"):sub(1, 50))
    end
end

-- ============================================================================
-- STATE MANAGEMENT
-- ============================================================================

local function load_state()
    local f = io.open(cfg.state_file, "r")
    if f then
        local content = f:read("*a")
        f:close()
        local clients = {}
        local ssid_enabled = {}
        local dhcp = {}
        for line in content:gmatch("[^\n]+") do
            local t, v = line:match("^([^:]+):(.+)$")
            if t == "client" then
                local mac, iface, ssid = v:match("^(.+)|(.+)|(.+)$")
                if mac and iface and is_valid_mac(mac) then clients[mac] = {iface=iface, ssid=ssid} end
            elseif t == "ssid" then ssid_enabled[v] = true
            elseif t == "dhcp" then
                local mac, ip = v:match("^(.+)->(.+)$")
                if mac and ip and is_valid_mac(mac) then dhcp[mac] = {ip=ip, mac=mac} end
            end
        end
        return { clients = clients, ssid_enabled = ssid_enabled, dhcp = dhcp }
    end
    return { clients = {}, ssid_enabled = {}, dhcp = {} }
end

local function save_state(state)
    local f = io.open(cfg.state_file, "w")
    if f then
        for mac, info in pairs(state.clients) do
            f:write("client:" .. mac .. "|" .. (info.iface or "") .. "|" .. (info.ssid or "") .. "\n")
        end
        for iface in pairs(state.ssid_enabled) do
            f:write("ssid:" .. iface .. "\n")
        end
        for mac, info in pairs(state.dhcp) do
            f:write("dhcp:" .. mac .. "->" .. info.ip .. "\n")
        end
        f:close()
    end
end

-- ============================================================================
-- WIFI: Get clients
-- ============================================================================

local function get_hostapd_interfaces()
    local f = io.popen("ubus list | grep hostapd")
    local interfaces = {}
    if f then
        for line in f:lines() do table.insert(interfaces, line) end
        f:close()
    end
    return interfaces
end

local function get_ssid_name(iface)
    local wlan_iface = iface:gsub("hostapd.", "")
    local f = io.popen("iw dev " .. wlan_iface .. " info 2>/dev/null | grep ssid")
    if f then
        local result = f:read("*a")
        f:close()
        local ssid = result:match("ssid%s+(.+)")
        if ssid and ssid ~= "" then return ssid:gsub("%s+$", "") end
    end
    return iface
end

local function get_wifi_clients()
    local clients = {}
    local interfaces = get_hostapd_interfaces()
    
    local ssid_map = {}
    for _, iface in ipairs(interfaces) do
        ssid_map[iface] = get_ssid_name(iface)
    end
    
    for _, iface in ipairs(interfaces) do
        local f = io.popen("ubus call " .. iface .. " get_clients 2>/dev/null")
        if f then
            local result = f:read("*a")
            f:close()
            if result:find('"clients"') and not result:find('"clients":%s*{}') then
                for mac in result:gmatch('([a-fA-F0-9][a-fA-F0-9]:[a-fA-F0-9][a-fA-F0-9]:[a-fA-F0-9][a-fA-F0-9]:[a-fA-F0-9][a-fA-F0-9]:[a-fA-F0-9][a-fA-F0-9]:[a-fA-F0-9][a-fA-F0-9])') do
                    if is_valid_mac(mac) and not clients[mac] then
                        clients[mac] = { iface = iface, ssid = ssid_map[iface] }
                    end
                end
            end
        end
    end
    return clients
end

-- ============================================================================
-- DHCP: Get leases
-- ============================================================================

local function get_dhcp_leases()
    local leases = {}
    
    local f = io.popen("ubus call dhcp ipv4leases 2>/dev/null")
    if f then
        local result = f:read("*a")
        f:close()
        if result:match('"leases"') then
            for ip, mac in result:gmatch('"ip":"([%d%.]+)"[^}]*"mac":"([a-fA-F0-9:]+)"') do
                if is_valid_mac(mac) then leases[mac] = {ip=ip, mac=mac} end
            end
            return leases
        end
    end
    
    f = io.popen("cat " .. cfg.dhcp_lease_file .. " 2>/dev/null")
    if f then
        for line in f:lines() do
            local ts, mac, ip, name = line:match("(%d+)%s+(%S+)%s+(%S+)%s+(%S+)")
            if mac and is_valid_mac(mac) then leases[mac] = {ip=ip, mac=mac, hostname=name} end
        end
        f:close()
    end
    return leases
end

-- ============================================================================
-- STATE
-- ============================================================================

local state = { clients = {}, ssid_enabled = {}, dhcp = {} }

-- ============================================================================
-- EVENT-DRIVEN HANDLERS (no polling!)
-- ============================================================================

-- Handle DHCP event
local function on_dhcp_event(action, mac, ip, hostname)
    if not is_valid_mac(mac) then return end
    
    local info = {mac=mac, ip=ip or "unknown", hostname=hostname}
    
    if action == "add" or action == "new" then
        if not state.dhcp[mac] then
            log_info("DHCP NEW: " .. mac .. " -> " .. ip)
            send_event("dhcp_new", '{"mac":"' .. mac .. '","ip":"' .. ip .. '"}')
            state.dhcp[mac] = info
        end
    elseif action == "del" or action == "release" then
        if state.dhcp[mac] then
            log_info("DHCP RELEASE: " .. mac .. " -> " .. state.dhcp[mac].ip)
            send_event("dhcp_release", '{"mac":"' .. mac .. '","ip":"' .. state.dhcp[mac].ip .. '"}')
            state.dhcp[mac] = nil
        end
    end
    save_state(state)
end

-- Handle WiFi client event
local function on_wifi_event(action, mac, iface)
    if not is_valid_mac(mac) then return end
    
    local ssid = get_ssid_name(iface)
    
    if action == "connected" or action == "add" then
        if not state.clients[mac] then
            log_info("WiFi CONNECTED: " .. mac .. " on " .. ssid)
            send_event("wifi_connected", '{"mac":"' .. mac .. '","ssid":"' .. ssid .. '","interface":"' .. iface .. '"}')
            state.clients[mac] = {iface=iface, ssid=ssid}
        end
    elseif action == "disconnected" or action == "del" then
        if state.clients[mac] then
            log_info("WiFi DISCONNECTED: " .. mac .. " from " .. ssid)
            send_event("wifi_disconnected", '{"mac":"' .. mac .. '","ssid":"' .. ssid .. '","interface":"' .. iface .. '"}')
            state.clients[mac] = nil
        end
    end
    save_state(state)
end

-- ============================================================================
-- UBUS EVENT LISTENER (TRUE event-driven!)
-- ============================================================================

local function start_ubus_listen()
    if not luv_ok then
        log_info("luv not available")
        return false
    end
    
    log_info("Starting ubus listen (event-driven)...")
    
    -- Use ubus listen in background process - this is TRUE event-driven!
    -- ubus listen blocks and emits events when they happen
    local function ubus_listen_loop()
        -- Spawn ubus listen as background process
        -- It will emit JSON events to stdout when DHCP/WiFi events happen
        local pipe = io.popen("ubus listen dhcp ipv4leases network.interface.* hostapd.* 2>&1", "r")
        
        if not pipe then
            log_info("ubus listen failed")
            return false
        end
        
        log_info("ubus listen started - waiting for events...")
        
        -- Read events as they come (blocking but event-driven)
        while true do
            local line = pipe:read("*line")
            if not line then break end
            
            log_info("ubus event: " .. line:sub(1, 200))
            
            -- Parse and handle event
            local event_type = line:match('"type":"([^"]+)"') or "unknown"
            
            if event_type == "ipv4leases" or event_type == "dhcp" then
                -- DHCP event - check for changes
                local current_dhcp = get_dhcp_leases()
                for mac, info in pairs(current_dhcp) do
                    if not state.dhcp[mac] then
                        on_dhcp_event("add", mac, info.ip, info.hostname)
                    end
                end
                for mac, info in pairs(state.dhcp) do
                    if not current_dhcp[mac] then
                        on_dhcp_event("del", mac, info.ip)
                    end
                end
            elseif event_type:match("hostapd") then
                -- WiFi event
                local current_clients = get_wifi_clients()
                for mac, info in pairs(current_clients) do
                    if not state.clients[mac] then
                        on_wifi_event("connected", mac, info.iface)
                    end
                end
                for mac, info in pairs(state.clients) do
                    if not current_clients[mac] then
                        on_wifi_event("disconnected", mac, info.iface)
                    end
                end
            end
        end
        
        pipe:close()
        log_info("ubus listen ended")
    end
    
    -- Run ubus listen in background thread
    luv.new_task(function()
        ubus_listen_loop()
    end)
    
    return true
end

-- ============================================================================
-- MAIN
-- ============================================================================

function main()
    log_info("Starting client2server-luv (event-driven)...")
    log_info("Router: " .. cfg.router_id)
    log_info("Server: " .. cfg.server_url)
    
    if luv_ok then
        log_info("luv available!")
    else
        log_info("luv NOT available")
    end
    
    -- Load state
    state = load_state()
    
    -- Initial event
    local leases = get_dhcp_leases()
    local count = 0
    for _ in pairs(leases) do count = count + 1 end
    log_info("DHCP leases: " .. count)
    send_event("router_online", '{"lease_count":' .. count .. '}')
    
    if luv_ok then
        -- Start event-driven listeners
        start_ubus_listen()
        
        log_info("Running event loop - waiting for events...")
        luv.run()
    else
        -- No luv - just wait
        while true do
            os.execute("sleep 60")
        end
    end
end

main()