"""
Scrape Eurostar timetable via httpx.

The route-specific timetable 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)
"""
import json
import re
import httpx

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 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)