"""
Scrape Eurostar timetable via httpx and fetch prices via the GraphQL API.

Timetable: route-specific pages are Next.js SSR — all departure data is
embedded in <script id="__NEXT_DATA__"> as JSON, so no browser / JS needed.

URL pattern:
  https://www.eurostar.com/uk-en/travel-info/timetable/
  {origin_id}/{dest_id}/{origin_slug}/{dest_slug}?date=YYYY-MM-DD

Data path: props.pageProps.pageData.liveDepartures[]
  .origin.model.scheduledDepartureDateTime  → London departure
  .destination.model.scheduledArrivalDateTime → destination arrival
    (already filtered to the requested stop, not the final stop)

Prices: POST https://site-api.eurostar.com/gateway (GraphQL, operationName
NewBookingSearch).  The `journeys[].fares[]` array contains one entry per
class of service; we extract the Eurostar Standard (classOfService.code ==
"STANDARD") displayPrice for 1 adult, in GBP.
"""
import json
import random
import re
import string

import httpx
import requests

DEFAULT_UA = (
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 "
    "(KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36"
)

ORIGIN_STATION_ID = '7015400'
ORIGIN_STATION_SLUG = 'london-st-pancras-intl'
TIMETABLE_BASE_URL = 'https://www.eurostar.com/uk-en/travel-info/timetable'

DESTINATION_STATION_IDS = {
    'Paris Gare du Nord': '8727100',
    'Brussels Midi': '8814001',
    'Lille Europe': '8722326',
    'Amsterdam Centraal': '8400058',
    'Rotterdam Centraal': '8400530',
}


def _slugify_station_name(name: str) -> str:
    return re.sub(r'[^a-z0-9]+', '-', name.lower()).strip('-')


def search_url(destination: str, travel_date: str) -> str:
    dest_id = DESTINATION_STATION_IDS[destination]
    return (
        f'https://www.eurostar.com/search/uk-en'
        f'?adult=1&origin={ORIGIN_STATION_ID}&destination={dest_id}&outbound={travel_date}'
    )


def timetable_url(destination: str) -> str:
    dest_id = DESTINATION_STATION_IDS[destination]
    dest_slug = _slugify_station_name(destination)
    return (
        f'{TIMETABLE_BASE_URL}/{ORIGIN_STATION_ID}/{dest_id}/'
        f'{ORIGIN_STATION_SLUG}/{dest_slug}'
    )


def _hhmm(dt_str: str | None) -> str | None:
    """'2026-03-30 09:34:00' → '09:34'"""
    if not dt_str:
        return None
    m = re.search(r'(\d{2}):(\d{2}):\d{2}$', dt_str)
    return f"{m.group(1)}:{m.group(2)}" if m else None


def _parse(html: str, destination: str) -> list[dict]:
    m = re.search(r'<script id="__NEXT_DATA__"[^>]*>(.*?)</script>', html, re.DOTALL)
    if not m:
        return []
    data = json.loads(m.group(1))
    departures = data['props']['pageProps']['pageData']['liveDepartures']
    services = []
    for dep in departures:
        dep_time = _hhmm(dep['origin']['model']['scheduledDepartureDateTime'])
        arr_time = _hhmm(dep['destination']['model']['scheduledArrivalDateTime'])
        if dep_time and arr_time:
            carrier = dep.get('model', {}).get('carrier', 'ES')
            number  = dep.get('model', {}).get('trainNumber', '')
            services.append({
                'depart_st_pancras': dep_time,
                'arrive_destination': arr_time,
                'destination': destination,
                'train_number': f"{carrier} {number}" if number else '',
            })
    return sorted(services, key=lambda s: s['depart_st_pancras'])


def fetch(destination: str, travel_date: str,
          user_agent: str = DEFAULT_UA) -> list[dict]:
    url = timetable_url(destination)
    headers = {
        'User-Agent': user_agent,
        'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
        'Accept-Language': 'en-GB,en;q=0.9',
    }
    with httpx.Client(headers=headers, follow_redirects=True, timeout=20) as client:
        r = client.get(url, params={'date': travel_date})
    r.raise_for_status()
    return _parse(r.text, destination)


# ---------------------------------------------------------------------------
# Price fetching via site-api.eurostar.com GraphQL
# ---------------------------------------------------------------------------

_GATEWAY_URL = 'https://site-api.eurostar.com/gateway'

# Minimal query requesting only timing + Eurostar Standard fare price.
# Variable names and inline argument names match what the site sends so the
# server-side query planner sees a familiar shape.
_GQL_PRICES = (
    "query NewBookingSearch("
    "$origin:String!,$destination:String!,$outbound:String!,"
    "$currency:Currency!,$adult:Int,"
    "$filteredClassesOfService:[ClassOfServiceEnum]"
    "){"
    "journeySearch("
    "outboundDate:$outbound origin:$origin destination:$destination"
    " adults:$adult currency:$currency"
    " productFamilies:[\"PUB\"] contractCode:\"EIL_ALL\""
    " adults16Plus:0 children:0 youths:0 children4Only:0 children5To11:0"
    " infants:0 adultsWheelchair:0 childrenWheelchair:0 guideDogs:0"
    " wheelchairCompanions:0 nonWheelchairCompanions:0"
    " isAftersales:false multipleFlexibility:true showAllSummatedFares:false"
    " seniorsAges:[] prioritiseShortHaulODTrains:true"
    "){"
    "outbound{"
    "journeys("
    "hideIndirectTrainsWhenDisruptedAndCancelled:false"
    " hideDepartedTrains:true"
    " hideExternalCarrierTrains:true"
    " hideDirectExternalCarrierTrains:true"
    "){"
    "timing{departureTime:departs __typename}"
    "fares(filteredClassesOfService:$filteredClassesOfService){"
    "classOfService{code __typename}"
    "prices{displayPrice __typename}"
    "seats __typename"
    "}"
    "__typename"
    "}"
    "__typename"
    "}"
    "__typename"
    "}"
    "}"
)


def _generate_cid() -> str:
    chars = string.ascii_letters + string.digits
    return 'SRCH-' + ''.join(random.choices(chars, k=22))


def fetch_prices(destination: str, travel_date: str) -> dict[str, int | None]:
    """
    Return Eurostar Standard prices for every departure on travel_date.

    Result: {depart_st_pancras: price_gbp_int_or_None}
    None means the class is sold out or unavailable for that departure.
    """
    dest_id = DESTINATION_STATION_IDS[destination]
    headers = {
        'User-Agent': DEFAULT_UA,
        'Content-Type': 'application/json',
        'Accept': '*/*',
        'Accept-Language': 'en-GB',
        'Referer': 'https://www.eurostar.com/',
        'x-platform': 'web',
        'x-market-code': 'uk',
        'x-source-url': 'search-app/',
        'cid': _generate_cid(),
    }
    payload = {
        'operationName': 'NewBookingSearch',
        'variables': {
            'origin': ORIGIN_STATION_ID,
            'destination': dest_id,
            'outbound': travel_date,
            'currency': 'GBP',
            'adult': 1,
            'filteredClassesOfService': ['STANDARD'],
        },
        'query': _GQL_PRICES,
    }
    resp = requests.post(_GATEWAY_URL, json=payload, headers=headers, timeout=20)
    resp.raise_for_status()
    data = resp.json()
    prices: dict[str, int | None] = {}
    journeys = data['data']['journeySearch']['outbound']['journeys']
    for journey in journeys:
        dep = journey['timing']['departureTime']
        price = None
        for fare in journey['fares']:
            if fare['classOfService']['code'] == 'STANDARD':
                p = fare.get('prices')
                if p and p.get('displayPrice'):
                    price = int(p['displayPrice'])
                break
        prices[dep] = price
    return prices