// 1. Implement a static C function
static int ntop_my_function(lua_State* vm) {
    // read args
    ntop_lua_check(vm, __FUNCTION__, 1, LUA_TSTRING);
    const char* arg = lua_tostring(vm, 1);
    // do work, push return value
    lua_pushstring(vm, result);
    return CONST_LUA_OK;  // or CONST_LUA_ERROR
}

// 2. Register it
{ "myFunction", ntop_my_function },   // called as ntop.myFunction(...)

HTTP request → HTTPserver.cpp → Lua VM → scripts/lua/<path>.lua
                                          ├── _GET["param"]        (GET params)
                                          ├── _POST["param"]       (POST params)
                                          ├── _SESSION["user"]     (logged-in username)
                                          ├── _SESSION["group"]    (user role)
                                          └── ntop.*()             (C bindings)

local dirs = ntop.getDirs()
package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path

require "lua_utils"        -- helper utilities
local json = require("dkjson")
local rest_utils = require("rest_utils")  -- for REST endpoints

scripts/lua/rest/v2/<method>/<resource>/<sub-resource>.lua

http(s)://<host>:3000/lua/rest/v2/<method>/<resource>/<sub>.lua

-- (C) 2013-26 - ntop.org

local dirs = ntop.getDirs()
package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path

local rest_utils = require("rest_utils")
require "lua_utils"
local json = require("dkjson")

-- ── Read parameters ──────────────────────────────────────────────────────────
local ifid   = _GET["ifid"]
local param1 = _GET["param1"]

-- ── Validate ─────────────────────────────────────────────────────────────────
if isEmptyString(ifid) then
   rest_utils.answer(rest_utils.consts.err.invalid_interface)
   return
end

if isEmptyString(param1) then
   rest_utils.answer(rest_utils.consts.err.invalid_args)
   return
end

-- ── Authorization ─────────────────────────────────────────────────────────────
if not isAdministrator() then
   rest_utils.answer(rest_utils.consts.err.not_granted)
   return
end

-- ── Work ─────────────────────────────────────────────────────────────────────
interface.select(ifid)

local result = {}
-- populate result ...

-- ── Return JSON ───────────────────────────────────────────────────────────────
rest_utils.answer(rest_utils.consts.success.ok, result)

local ifid = _GET["ifid"]
interface.select(ifid)
-- now interface.* calls operate on that interface

local value = ntop.getCache("ntopng.prefs.my_key")
ntop.setCache("ntopng.prefs.my_key", "new_value", 3600)  -- optional TTL

ntop.setHashCache("ntopng.user.admin", "language", "en")
local lang = ntop.getHashCache("ntopng.user.admin", "language")

local json = require("dkjson")
local encoded = json.encode({ key = "value" })
local decoded = json.decode(encoded)

if not isAdministrator() then
   rest_utils.answer(rest_utils.consts.err.not_granted)
   return
end

local body = _POST["JSON"]          -- raw JSON string
local data = json.decode(body or "")
local field = data and data["field"]

local info = ntop.getInfo()
print(info["version"])   -- e.g. "6.1.230101"

local dirs = ntop.getDirs()
package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path

-- Store per-user setting
ntop.setHashCache("ntopng.user.admin", "language", "it")

-- Read it back
local lang = ntop.getHashCache("ntopng.user.admin", "language")

-- Store JSON configuration
local json = require("dkjson")
ntop.setCache("ntopng.prefs.my_config", json.encode({enabled=true, threshold=100}))
local cfg = json.decode(ntop.getCache("ntopng.prefs.my_config") or "{}")

-- Save a preference
ntop.setPref("ntopng.prefs.my_feature_enabled", "1")

-- Read it back
local enabled = (ntop.getPref("ntopng.prefs.my_feature_enabled") == "1")

local ok = ntop.addUser(
  "analyst",                  -- username
  "Jane Analyst",             -- full name
  "s3cr3t",                   -- initial password
  "unprivileged",             -- role
  "192.168.1.0/24",          -- allowed networks
  "eth0",                     -- allowed interface
  nil,                        -- host pool (nil = all)
  "en",                       -- language
  false,                      -- pcap download
  true,                       -- historical flows
  true                        -- alerts
)

local json = require("dkjson")
local body = ntop.httpGet("https://api.example.com/data", nil, nil, 5, true)
if body then
   local data = json.decode(body)
end

TRACE_ERROR   = 0
TRACE_WARNING = 1
TRACE_NORMAL  = 2
TRACE_INFO    = 3
TRACE_DEBUG   = 4

ntop.traceEvent(TRACE_WARNING, "unexpected value: " .. tostring(v))

local now_ms = ntop.gettimemsec()
local rounded = ntop.roundTime(os.time(), 60)  -- round to last minute

local bm = 0
bm = ntop.bitmapSet(bm, 3)        -- set bit 3
if ntop.bitmapIsSet(bm, 3) then   -- test bit 3
   bm = ntop.bitmapClear(bm, 3)   -- clear bit 3
end

-- Typical usage in housekeeping
ntop.initnDPIReload()
ntop.loadCustomCategoryIp(cat_id, "192.168.1.0/24")
ntop.loadCustomCategoryHost(cat_id, "ads.example.com")
ntop.loadCustomCategoryFile(cat_id, "/etc/ntopng/custom_hosts.txt")
ntop.setDomainMask("example.com", 0x1)
ntop.addTrustedIssuerDN("CN=MyCA,O=MyOrg")
ntop.finalizenDPIReload()

-- Cache expensive computation for 60 seconds
local cached = ntop.getLuaCache("my_expensive_result")
if not cached then
   cached = computeExpensiveResult()
   ntop.setLuaCache("my_expensive_result", cached, 60)
end

local dirs = ntop.getDirs()
package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
local rest_utils = require("rest_utils")
require "lua_utils"

local ifid = _GET["ifid"]
if isEmptyString(ifid) then
   rest_utils.answer(rest_utils.consts.err.invalid_interface)
   return
end
interface.select(ifid)
local data = interface.getStats()
rest_utils.answer(rest_utils.consts.success.ok, data)

local dirs = ntop.getDirs()
package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
local rest_utils = require("rest_utils")
require "lua_utils"
local json = require("dkjson")

if not isAdministrator() then
   rest_utils.answer(rest_utils.consts.err.not_granted)
   return
end

local body = json.decode(_POST["JSON"] or "{}")
local username = body and body["username"]
if isEmptyString(username) then
   rest_utils.answer(rest_utils.consts.err.invalid_args)
   return
end

local ok = ntop.addUser(username, body["full_name"] or "", body["password"] or "",
                        "unprivileged", "", "")
if ok then
   rest_utils.answer(rest_utils.consts.success.ok)
else
   rest_utils.answer(rest_utils.consts.err.internal_error)
end

local CONF_KEY = "ntopng.prefs.my_feature"
local json = require("dkjson")
require "lua_utils"
local rest_utils = require("rest_utils")

-- GET: read config
local raw = ntop.getCache(CONF_KEY)
local conf = json.decode(raw or "{}") or {}
rest_utils.answer(rest_utils.consts.success.ok, conf)

-- POST: write config
local body = json.decode(_POST["JSON"] or "{}")
ntop.setCache(CONF_KEY, json.encode(body))
rest_utils.answer(rest_utils.consts.success.ok)

-- Store
ntop.setHashCache("ntopng.user." .. username, "my_setting", value)

-- Read
local v = ntop.getHashCache("ntopng.user." .. username, "my_setting")