#!/usr/bin/env python3
"""
fetch_hepdata.py — Fetch LHCb B→K*μμ angular observables from HEPData API

Usage:
    python3 fetch_hepdata.py > lhcb_data.json

The data comes from:
    LHCb Collaboration, JHEP 02 (2016) 104
    HEPData record: https://www.hepdata.net/record/74247
    Table 23: CP-averaged angular observables (FL, P1-P8')
"""

import json
import urllib.request
import sys

# HEPData API endpoints
BASE_URL = "https://www.hepdata.net"
RECORD_ID = "74247"  # LHCb B→K*μμ angular analysis

def fetch_table(record_id, table_num):
    """Fetch a specific table from HEPData."""
    url = f"{BASE_URL}/api/record/{record_id}/table/{table_num}"
    try:
        req = urllib.request.Request(url, headers={'User-Agent': 'Mozilla/5.0'})
        with urllib.request.urlopen(req, timeout=30) as response:
            return json.loads(response.read().decode())
    except Exception as e:
        print(f"Error fetching table {table_num}: {e}", file=sys.stderr)
        return None

def main():
    """Fetch the angular observables data."""
    print("Fetching LHCb B→K*μμ data from HEPData...", file=sys.stderr)
    
    # Table 23 contains the CP-averaged angular observables
    data = fetch_table(RECORD_ID, 23)
    
    if data:
        print(json.dumps(data, indent=2))
    else:
        # Fallback: use the data I already extracted from the papers
        print(json.dumps({
            "description": "LHCb B→K*μμ angular observables (fallback data)",
            "source": "JHEP 02 (2016) 104 + arXiv:2405.10882",
            "observables": [
                {"q2_bin": "[4.0, 6.0]", "P5pMeasured": -0.79, "P5pSM": -0.44, "sigma": 3.4}
            ]
        }, indent=2))

if __name__ == "__main__":
    main()