OBP60v/navtex.py

"""
DWD NAVTEX 

Funkmodul (radio) noch nicht implementiert mangels Hardware

B1: Transmitter identity

B2: Subject indicator character

    A 	Navigational warnings
    B 	Meteorological warnings
    C 	Ice reports
    D 	Search & rescue information, and pirate warnings
    E 	Meteorological forecasts
    F 	Pilot service messages
    G 	AIS messages (formerly Decca messages[6])
    H 	LORAN messages
    I 	Not used (formerly OMEGA messages[6])
    J 	SATNAV messages (i.e. GPS or GLONASS)
    K 	Other electronic navaid messages
    L 	Navigational warnings — additional to letter A (Should not be rejected by the receiver)
    T 	Test transmissions (UK only — not official)
    V 	Notice to fishermen (U.S. only — currently not used)
    W 	Environmental (U.S. only — currently not used)
    X 	Special services — allocation by IMO NAVTEX Panel
    Y 	Special services — allocation by IMO NAVTEX Panel
    Z 	No message on hand 

Für Konfiguration: subjects = ABCDEFGHIJKLTVWXYZ


B3, B4: Serial number 01-99, 00: immediate printout

Timecode: DDHHmm UTC MMM YY

Sqlite database schema
  .schema message
  msgid TEXT PRIMARY KEY
  timestamp TEXT
  station TEXT
  content TEXT
  received TEXT

siehe auch: https://www.icselectronics.co.uk/support/info/navtexdb
"""
import os
import http.client
import ssl
import re
import sqlite3
import datetime
from gi.repository import GLib

class NAVTEX():

    def __init__(self, logger, cfg):
        self.log = logger
        self.source = cfg['ntx_source'].lower() # net | radio
        self.maxage = cfg['ntx_housekeeping'] # message hold time in hours
        self.running = False
        dbpath = os.path.join(cfg['histpath'], "navtex.db")
        try:
            self.conn = sqlite3.connect(dbpath)
            self.cur = self.conn.cursor()
        except:
            self.log.error(f"Failed to open local database: {dbpath}")
            return
        # Datenbank erstellen wenn nicht vorhanden
        sql = "SELECT name FROM sqlite_master WHERE type='table' AND name='message'"
        self.cur.execute(sql)
        if self.cur.fetchone() == None:
            sql = ("CREATE TABLE IF NOT EXISTS message ("
                   "msgid TEXT PRIMARY KEY NOT NULL,"
                   "station TEXT,"
                   "timestamp TEXT,"
                   "content TEXT NOT NULL,"
                   "received TEXT NOT NULL DEFAULT current_timestamp)"
                  )
            self.cur.execute(sql)
            self.log.info(f"Created NAVTEX database: {dbpath}")
        # Aktualisieren bei Programmstart
        # TODO Ausgeschaltet für Programmentwicklung
        if self.source == 'net':
            self.refresh()
        # In der Konfiguration werden Minuten angegeben
        GLib.timeout_add_seconds(cfg['ntx_refresh'] * 60, self.on_timer)
        self.running = True

    def __del__(self):
        self.conn.close()

    def on_timer(self):
        """
        NAVTEX data handling
        """
        self.refresh()
        self.housekeeping()
        return True

    def parse_message(self, plainmsg):
        """
        Zeile 1: ZCZC<space><BBBB>
        Zeile 2: Stationskennung
        Zeile 3: Zeitstempel (meistens)
        Zeile 4 bis n-1: Nachrichteninhalt
        Zeile n: NNNN

        Je nach Code B1, B2 kann das folgende Format unterschiedlich sein
        """
        msg = {}
        data = plainmsg.splitlines()
        msg['id'] = data[0][5:9]
        msg['station'] = data[1].strip()
        timestamp = data[2]
        if len(timestamp) == 17:
            day = int(timestamp[0:2])
            hour = int(timestamp[2:4])
            minute = int(timestamp[4:6])
            monmap = ('JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL', 'AUG', 'SEP', 'OCT', 'NOV', 'DEC')
            month = monmap.index(timestamp[11:14]) + 1
            year = 2000 + int(timestamp[15:17])
            try:
                msg['timestamp'] = datetime.datetime(year, month, day, hour, minute, 0)
            except:
                msg['timestamp'] = None
        else:
            msg['timestamp'] = None
        return msg

    def dwd_get_data(self, local=False):
        """
        net: Webseite auslesen
        https://www.dwd.de/DE/fachnutzer/schifffahrt/funkausstrahlung/navtex
        """
        if local:
            # Für Tests um nicht permanent die Webseite abzufragen
            with open("490_emd.html", "r") as fh:
                content = fh.read()
        else:
            ssl_context = ssl.create_default_context()
            conn = http.client.HTTPSConnection("www.dwd.de", 443, context=ssl_context)
            url = "https://www.dwd.de/DE/fachnutzer/schifffahrt/funkausstrahlung/navtex/490_emd.html"

            try:
                conn.request("GET", url)
                response = conn.getresponse()
                if response.status == 200:
                    content = response.read().decode()
                else:
                    print(f"Error: {response.status}")
                    return []
            except http.client.HTTPException as e:
                self.log.warning(f"HTTP error occurred: {e}")
                return []
            except ssl.SSLError as ssl_error:
                self.log.warning(f"SSL error occurred: {ssl_error}")
                return []

        expr = re.compile("(ZCZC.*?NNNN)", re.DOTALL)
        matches = re.findall(expr, content)

        return matches

    def refresh(self):
        self.log.info("NAVTEX refresh")
        messages = self.dwd_get_data(False)
        sql = "INSERT INTO message (msgid, station, content) VALUES (?, ?, ?)"
        for m in messages:
            msg = self.parse_message(m)
            self.cur.execute("SELECT COUNT(*) FROM message WHERE msgid=?", (msg['id'],))
            result = self.cur.fetchone()
            if result[0] == 0:
                self.log.debug(f"NAVTEX: insert new message '{msg['id']}'")
                self.cur.execute(sql, (msg['id'], msg['station'], m))
                self.conn.commit()

    def housekeeping(self):
        self.log.info("NAVTEX housekeeping")
        sql = "DELETE FROM message WHERE (julianday('now') - julianday(received)) * 24 > ?"
        self.cur.execute(sql, (self.maxage, ))

    def get_count(self):
        sql = "SELECT COUNT(*) FROM message"
        self.cur.execute(sql)
        result = self.cur.fetchone()
        return result[0]

    def get_ids(self):
        sql = "SELECT msgid FROM message"
        result = self.cur.execute(sql)
        msgids = []
        for row in result.fetchall():
            msgids.append(row[0])
        return msgids

    def get_message(self, msgid):
        sql = "SELECT content FROM message WHERE msgid=?"
        self.cur.execute(sql, (msgid, ))
        result = self.cur.fetchone()
        return result[0]