--[[
    client2server-luv - client2server-minimal.lua with TRUE luv async
    
    Features:
    - DHCP + WiFi + SSID monitoring via ubus
    - ASYNC: react IMMEDIATELY when events happen (not polling!)
    - luv fs_event for file watching
    - luv timer for immediate triggers
    - 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",
    check_interval = 10,
    dhcp_lease_file = "/var/lib/dnsmasq/dnsmasq.leases",
    state_file = "/tmp/client2server_state",
}

-- ============================================================================
-- 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 interfaces + clients + SSID
-- ============================================================================

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_map = {
        ["hostapd.wlan0-1"] = "wlan0-1",
        ["hostapd.wlan0-2"] = "wlan0-2",
        ["hostapd.wlan1-1"] = "wlan1-1",
    }
    local wlan_iface = wlan_map[iface] or 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_all_ssids()
    local ssids = {}
    local f = io.popen("iw dev 2>/dev/null")
    if f then
        local result = f:read("*a")
        f:close()
        local current_iface = nil
        for line in result:gmatch("[^\n]+") do
            local iface = line:match("Interface%s+(wlan%d[^%s]*)")
            if iface then current_iface = iface end
            local ssid = line:match("ssid%s+(.+)")
            if ssid and current_iface then
                ssids["hostapd." .. current_iface] = { enabled = true, ssid = ssid }
            end
        end
    end
    return ssids
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
    
    local count = 0
    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] }
                        count = count + 1
                    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
    
    -- Fallback: read lease file
    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

-- ============================================================================
-- ASYNC WATCHERS (TRUE EVENT-DRIVEN)
-- ============================================================================

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

-- Check and report changes
local function check_and_report()
    -- WiFi Clients
    local current_clients = get_wifi_clients()
    
    for mac, info in pairs(current_clients) do
        if not state.clients[mac] then
            log_info("WiFi CONNECTED: " .. mac .. " on " .. info.ssid)
            send_event("wifi_connected", '{"mac":"' .. mac .. '","ssid":"' .. info.ssid .. '","interface":"' .. info.iface .. '"}')
        end
    end
    for mac, info in pairs(state.clients) do
        if not current_clients[mac] then
            log_info("WiFi DISCONNECTED: " .. mac .. " from " .. info.ssid)
            send_event("wifi_disconnected", '{"mac":"' .. mac .. '","ssid":"' .. info.ssid .. '","interface":"' .. info.iface .. '"}')
        end
    end
    state.clients = current_clients
    
    -- SSID Status
    local current_ssid = get_all_ssids()
    for iface, info in pairs(current_ssid) do
        if not state.ssid_enabled[iface] then
            local ssid = get_ssid_name(iface)
            log_info("SSID ENABLED: " .. ssid .. " (" .. iface .. ")")
            send_event("ssid_enabled", '{"interface":"' .. iface .. '","ssid":"' .. ssid .. '"}')
        end
    end
    for iface in pairs(state.ssid_enabled) do
        if not current_ssid[iface] then
            local ssid = get_ssid_name(iface)
            log_info("SSID DISABLED: " .. ssid .. " (" .. iface .. ")")
            send_event("ssid_disabled", '{"interface":"' .. iface .. '","ssid":"' .. ssid .. '"}')
        end
    end
    state.ssid_enabled = current_ssid
    
    -- DHCP Leases
    local current_dhcp = get_dhcp_leases()
    for mac, info in pairs(current_dhcp) do
        if not state.dhcp[mac] then
            log_info("DHCP NEW: " .. mac .. " -> " .. info.ip)
            send_event("dhcp_new", '{"mac":"' .. mac .. '","ip":"' .. info.ip .. '"}')
        end
    end
    for mac, info in pairs(state.dhcp) do
        if not current_dhcp[mac] then
            log_info("DHCP RELEASE: " .. mac .. " -> " .. info.ip)
            send_event("dhcp_release", '{"mac":"' .. mac .. '","ip":"' .. info.ip .. '"}')
        end
    end
    state.dhcp = current_dhcp
    
    save_state(state)
end

-- ============================================================================
-- ASYNC EVENT HANDLERS (immediate reaction)
-- ============================================================================

local function start_async_watchers()
    if not luv_ok then return false end
    
    log_info("Starting async watchers...")
    
    -- 1. DHCP: Watch lease file with fs_event (REACT IMMEDIATELY)
    local fs_event = luv.new_fs_event()
    local function watch_dhcp()
        log_info("DHCP lease file changed - checking...")
        check_and_report()
        -- Re-watch
        luv.fs_event_start(fs_event, cfg.dhcp_lease_file, function(err)
            if err then
                log_info("DHCP fs_event error: " .. err)
            else
                watch_dhcp()
            end
        end)
    end
    -- Start watching
    luv.fs_event_start(fs_event, cfg.dhcp_lease_file, function(err)
        if err then
            log_info("DHCP watch error: " .. err)
        else
            log_info("Watching DHCP leases: " .. cfg.dhcp_lease_file)
            watch_dhcp()
        end
    end)
    
    -- 2. WiFi: Timer-based but frequent (every 5s)
    local wifi_timer = luv.new_timer()
    luv.timer_start(wifi_timer, 5000, 5000, function()
        log_info("WiFi check (timer)...")
        check_and_report()
    end)
    
    -- 3. SSID: Less frequent (every 30s)
    local ssid_timer = luv.new_timer()
    luv.timer_start(ssid_timer, 30000, 30000, function()
        log_info("SSID check (timer)...")
        check_and_report()
    end)
    
    return true
end

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

function main()
    log_info("Starting client2server-luv (async)...")
    log_info("Router: " .. cfg.router_id)
    log_info("Server: " .. cfg.server_url)
    
    if luv_ok then
        log_info("luv available - ASYNC mode!")
    else
        log_info("luv NOT available - blocking mode")
    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
        -- ASYNC MODE
        local started = start_async_watchers()
        
        if started then
            log_info("Async watchers started - running event loop")
            luv.run()
        else
            -- Fallback to timer-based
            log_info("Using timer-based fallback")
            local timer = luv.new_timer()
            local function run_loop()
                check_and_report()
                luv.timer_start(timer, cfg.check_interval * 1000, 0, function() run_loop() end)
            end
            luv.timer_start(timer, cfg.check_interval * 1000, 0, function() run_loop() end)
            luv.run()
        end
    else
        -- BLOCKING MODE
        while true do
            check_and_report()
            os.execute("sleep " .. cfg.check_interval)
        end
    end
end

main()