#!/usr/bin/lua
-- Programm: ntpstat.lua
-- Version: 2.0
-- Created on 25/Jun/2026 by jokel
local mode = arg[1]

-- Hilfe
local function show_help()
    print([[
ntpstat (Lua-Version 2.0)

Aufruf:
  ntpstat               -> Vollständige Ausgabe
  ntpstat last          -> Zeitpunkt der letzten Synchronisation
  ntpstat next          -> Zeitpunkt der nächsten Synchronisation
  ntpstat status        -> synchronised / unsynchronised
  ntpstat tz            -> Sommerzeit/Winterzeit anzeigen
  ntpstat --help        -> Diese Hilfe
]])
end

if mode == "--help" then
    show_help()
    os.exit(0)
end

-- Shell-Befehl
local function cmd(s)
    local f = io.popen(s)
    local out = f:read("*a")
    f:close()
    return out
end

local tracking = cmd("chronyc tracking")
local sources  = cmd("chronyc sources")

-- Leap Status
local leap = tracking:match("Leap status%s*:%s*(%S+)") or "Unknown"

-- Zeitzonen-Offset (lokal - UTC)
local function get_tz_offset()
    local now_local = os.time()
    local now_utc   = os.time(os.date("!*t"))
    return now_local - now_utc
end

local tz_offset = get_tz_offset()

-- Sommerzeit-Erkennung
local function is_summer_time()
    return os.date("*t").isdst == true
end

-- Ref time (UTC)
local ref_line = tracking:match("Ref time %(UTC%)%s*:%s*(.-)\n")

local last_sync_epoch = nil
local last_sync_local = "n/a"
local age = 0

if ref_line then
    -- Thu Jun 25 07:13:06 2026
    local weekday, month_str, day, hh, mm, ss, year =
        ref_line:match("(%a+)%s+(%a+)%s+(%d+)%s+(%d+):(%d+):(%d+)%s+(%d+)")

    if month_str then
        local months = {
            Jan=1, Feb=2, Mar=3, Apr=4,
            May=5, Jun=6, Jul=7, Aug=8,
            Sep=9, Oct=10, Nov=11, Dec=12
        }

        local month = months[month_str]

        -- UTC → lokale Zeit korrigieren
        local t = {
            year = year,
            month = month,
            day = day,
            hour = hh,
            min = mm,
            sec = ss,
            isdst = false
        }

        -- os.time(t) interpretiert t als lokale Zeit → Offset ADDIEREN
        local local_epoch = os.time(t)
        last_sync_epoch = local_epoch + tz_offset

        local now_epoch = os.time()
        age = now_epoch - last_sync_epoch

        last_sync_local = os.date("%Y-%m-%d %H:%M:%S", last_sync_epoch)
    end
end

-- aktive Quelle finden
local active = sources:match("%s*%^%*%s*.-\n")

if not active then
    print("ERROR: keine aktive Quelle gefunden")
    print(sources)
    os.exit(1)
end

-- "^*" entfernen
active = active:gsub("%s*%^%*%s*", "")

-- Hostname entfernen
active = active:gsub("^[^%s]+%s+", "")

-- Felder extrahieren
local fields = {}
for w in active:gmatch("%S+") do table.insert(fields, w) end

local poll   = tonumber(fields[2]) or 10
local lastrx = tonumber(fields[4]) or 0

local interval = 2 ^ poll
local remaining = interval - lastrx
if remaining < 0 then remaining = 0 end

local now_epoch = os.time()
local next_sync_epoch = now_epoch + remaining
local next_sync_human = os.date("%Y-%m-%d %H:%M:%S", next_sync_epoch)

-- Offset extrahieren
local offset = tracking:match("System time%s*:%s*(.-)\n") or "n/a"

-- Offset in Sekunden extrahieren
local offset_value = offset:match("([%d%.%-]+)%s*seconds")
offset_value = tonumber(offset_value) or 0

-- in Millisekunden umrechnen
local offset_ms = offset_value * 1000

-- Richtung bestimmen
local offset_dir = offset:match("slow") and "langsamer" or "schneller"

-- STATUS
if mode == "status" then
    if leap == "Normal" then
        print("synchronised")
    else
        print("unsynchronised")
    end
    os.exit(0)
end

-- TZ
if mode == "tz" then
    if is_summer_time() then
        print("Sommerzeit aktiv (CEST)")
    else
        print("Winterzeit aktiv (CET)")
    end
    os.exit(0)
end

local now = "%.3f ms %s als NTP-Zeit."

-- LAST
if mode == "last" then
    print(last_sync_local .. string.format(" Offset " .. now, offset_ms, offset_dir))
    os.exit(0)
end

-- NEXT
if mode == "next" then
    print(next_sync_human)
    os.exit(0)
end

-- VOLLAUSGABE
if leap == "Normal" then
    print("synchronised")
else
    print("unsynchronised")
end

print("Last sync : " .. last_sync_local)
print("Age       : " .. age .. "s")
print("Poll      : " .. poll)
print("Interval  : " .. interval .. "s")
print("LastRx    : " .. lastrx .. "s")
print("Next sync : " .. next_sync_human)
print("Remaining : " .. remaining .. "s")

print(string.format("Offset s  : %.9f Sekunden.", offset_value, offset_dir))
print(string.format("Offset ms : " .. now, offset_ms, offset_dir))

local tz_status = is_summer_time() and "Sommerzeit (CEST)" or "Winterzeit (CET)"
print("TZ-Status : " .. tz_status)