nightjetter/main.py

import csv
import json
from dataclasses import dataclass
from datetime import datetime
from pathlib import Path
from typing import Any

import requests

BASE_URL = "https://www.nightjet.com"
BASE_DIR = "out"
CSV_LOWEST_FILE = f"{BASE_DIR}/lowest.csv"
CSV_ALL_PRICES_PATTERN = f"{BASE_DIR}/%%DATE%%_all_prices.csv"
NOTIFICATION_CHANNEL="nightjet-price-notifier"


def dprint(txt) -> None:
    print(f"{datetime.now()}: {txt}")


def request_init_token(endpoint: str = "/nj-booking-ocp/init/start") -> str:
    headers = {
        "Referer": "https://www.nightjet.com",
        "Content-Type": "application/json",
    }
    body = {"lang": "en"}
    resp_json = requests.post(
        f"{BASE_URL}{endpoint}", data=json.dumps(body), headers=headers
    ).json()
    token = resp_json["token"]

    dprint(f"Received init token: {token}")
    return token


START_STATION = "8096003"  # BerlinHBF
END_STATION = "8796001"  # Paris Est
TRAVEL_DATE = "2025-10-14"


def request_connections(
    token: str, endpoint: str = "/nj-booking-ocp/connection"
) -> list[Any]:
    uri = f"{BASE_URL}{endpoint}/{START_STATION}/{END_STATION}/{TRAVEL_DATE}"
    headers = {
        "Accept": "application/json",
        "Accept-Language": "en-US,en;q=0.5",
        "Referer": "https://www.nightjet.com/en/ticket-buchen/",
        "x-token": token,
        "User-Agent": "Mozilla/5.0 (X11; Linux x86_64; rv:139.0) Gecko/20100101 Firefox/139.0",
    }

    resp_json = requests.get(
        uri,
        headers=headers,
    ).json()
    return resp_json["connections"]


TRAVELLER_BIRTHDATE = "2000-07-15"  # TODO: randomize a little


def connection_data_to_booking_requests(connections) -> list[dict[str, Any]]:
    b_requests = []
    for c in connections:
        train = c["trains"][0]
        dep = train["departure"]["utc"]
        req = {
            "njFrom": c["from"]["number"],  # from station,
            "njTo": c["to"]["number"],  # to station
            "njDep": dep,  # departure time,
            "maxChanges": 0,
            "connections": 1,
            "filter": {
                "njTrain": train["train"],  # train number
                "njDeparture": dep,  # departure time again
            },
            "objects": [  # traveller
                {"type": "person", "birthDate": TRAVELLER_BIRTHDATE, "cards": []}
            ],
            "relations": [],
            "lang": "en",
        }
        b_requests.append(req)
        dprint(
            f"Crafted booking request {c['from']['name']} -> {c['to']['name']}: {train['departure']['local']}-{train['arrival']['local']}."
        )
    return b_requests


def request_bookings(
    token: str, booking_req: dict[str, Any], endpoint: str = "/nj-booking-ocp/offer/get"
) -> dict[Any, Any]:
    headers = {
        "Accept": "application/json",
        "Accept-Language": "en-US,en;q=0.5",
        "Content-Type": "application/json",
        "Referer": "https://www.nightjet.com/en/ticket-buchen/",
        "Origin": "https://www.nightjet.com",
        "x-token": token,
        "User-Agent": "Mozilla/5.0 (X11; Linux x86_64; rv:139.0) Gecko/20100101 Firefox/139.0",
    }
    resp_json = requests.post(
        f"{BASE_URL}{endpoint}", headers=headers, data=json.dumps(booking_req)
    ).json()
    dprint(
        f"Requested prices ({booking_req['njFrom']} -> {booking_req['njTo']} at {booking_req['njDep']})."
    )
    return resp_json


def json_extract(obj, key):
    """Recursively fetch values from nested JSON."""
    arr = []

    def extract(obj, arr, key):
        """Recursively search for values of key in JSON tree."""
        if isinstance(obj, dict):
            for k, v in obj.items():
                if isinstance(v, (dict, list)):
                    extract(v, arr, key)
                elif k == key:
                    arr.append(v)
        elif isinstance(obj, list):
            for item in obj:
                extract(item, arr, key)
        return arr

    values = extract(obj, arr, key)
    return values


@dataclass
class Price:
    id: str
    name: str
    price: float


def extract_prices(bookings_dict: list[dict[Any, Any]]) -> list[Price]:
    prices = []
    # .result[].connections[].offers[].reservation.reservationSegments[].compartments[].objects
    for booking in bookings_dict:
        for reservation in booking["result"]:
            for connection in reservation["connections"]:
                for offer in connection["offers"]:
                    for reservation in offer["reservation"]["reservationSegments"]:
                        for compartment in reservation["compartments"]:
                            id = compartment["externalIdentifier"]
                            name = compartment["name"]["en"]
                            # filter undesired compartments
                            if id in ["sideCorridorCoach_2"]:
                                continue
                            # print all compartment identifiers w/ full name
                            # dprint(f"{id}: {name}")

                            # only keep those with a price (i.e. bookable?)
                            if "objects" not in compartment:
                                continue
                            price = compartment["objects"][0]["price"]
                            prices.append(Price(id, name, price))
    return prices


def get_lowest_price(prices: list[Price]) -> Price:
    lowest = Price("", "", 10000000.0)
    for p in prices:
        if p.price < lowest.price:
            lowest = p
    return lowest


def dump_all_prices_to_csv(prices: list[Price]) -> None:
    fname = CSV_ALL_PRICES_PATTERN.replace(
        "%%DATE%%", str(int(datetime.now().timestamp()))
    )
    with open(fname, "w") as f:
        writer = csv.writer(f)
        writer.writerow(["id", "price", "name"])
        writer.writerows([[price.id, price.price, price.name] for price in prices])


def add_to_csv(price: Price) -> None:
    if not Path(CSV_LOWEST_FILE).is_file():
        with open(CSV_LOWEST_FILE, "w") as f:
            csv.writer(f).writerow(["id", "price", "name"])

    with open(CSV_LOWEST_FILE, "a") as f:
        csv.writer(f).writerow([price.id, price.price, price.name])


def get_last_price_from_csv() -> Price | None:
    if not Path(CSV_LOWEST_FILE).is_file():
        return

    with open(CSV_LOWEST_FILE) as f:
        last = next(reversed(list(csv.reader(f))))
        return Price(last[0], last[2], float(last[1]))


def notify_user(previous: Price, new: Price, channel: str) -> None:
    requests.post(
        f"https://ntfy.sh/{channel}",
        data=f"from {previous.price} -> {new.price} ({new.name})",
        headers={
            "Title": f"Nightjet train price went {'down' if new.price < previous.price else 'up'}",
            "Priority": "urgent" if new.price < previous.price else "default",
            "Tags": "green_circle" if new.price < previous.price else "orange_circle",
        },
    )


def main():
    token = request_init_token()
    connections = request_connections(token)
    booking_requests = connection_data_to_booking_requests(connections)
    bookings = [request_bookings(token, req) for req in booking_requests]
    prices = extract_prices(bookings)

    # create a snapshot of all current prices
    dump_all_prices_to_csv(prices)

    # extract the lowest and the last lowest price
    new = get_lowest_price(prices)
    previous = get_last_price_from_csv()

    # if the price changed, add it to lowest prices
    if not previous or new.price != previous.price:
        dprint(f"PRICE CHANGE. {previous} -> {new}")
        notify_user(previous or Price("", "", 0.0), new, NOTIFICATION_CHANNEL)
        add_to_csv(new)


if __name__ == "__main__":
    Path(BASE_DIR).mkdir(exist_ok=True, parents=True)
    main()