# -----------------------------------------------------------------------------
# Author: Jiawei Liu
# Date: 2024-11-22
# -----------------------------------------------------------------------------
'''
Download script for CANADA MO

Notes:
1. 1969-1993 no solution
2. 1994-1999 problem and solution are separated in two file
3. 2000+ problem and solution in the same file

To run: 
`python CANADA_MO\download_script\download.py`
'''

import requests
from requests.adapters import HTTPAdapter
from tqdm import tqdm
from bs4 import BeautifulSoup
from urllib.parse import urljoin
from urllib3.util.retry import Retry
from pathlib import Path


def build_session(
    max_retries: int = 3,
    backoff_factor: int = 2,
    session: requests.Session = None
) -> requests.Session:
    """
    Build a requests session with retries

    Args:
        max_retries (int, optional): Number of retries. Defaults to 3.
        backoff_factor (int, optional): Backoff factor. Defaults to 2.
        session (requests.Session, optional): Session object. Defaults to None.
    """
    session = session or requests.Session()
    adapter = HTTPAdapter(max_retries=Retry(total=max_retries, backoff_factor=backoff_factor))
    session.mount("http://", adapter)
    session.mount("https://", adapter)
    session.headers.update({
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3"
    })

    return session


def main():
    req_session = build_session()
    base_url = "https://cms.math.ca/Competitions/CMO/"

    output_dir = Path(__file__).parent.parent / "raw"
    output_dir.mkdir(parents=True, exist_ok=True)
    
    resp = req_session.get(base_url)
    soup = BeautifulSoup(resp.text, "html.parser")

    cmo_year_a_ele = soup.find_all("a", href=lambda t: "#cmo" in t)

    for cy_a_ele in tqdm(cmo_year_a_ele):
        year = cy_a_ele.get_text(strip=True)

        # Get problem and solution link elements
        pro_link_ele = cy_a_ele.parent.parent.select_one("td:nth-child(2)").find("a")
        sol_link_ele = cy_a_ele.parent.parent.select_one("td:nth-child(3)").find("a")

        donwload_urls = []
        if sol_link_ele:
            donwload_urls.append(sol_link_ele["href"])
        else:
            donwload_urls.append(pro_link_ele["href"])
        
        # Year is between 1994 and 1999, download both problem and solution
        if int(year) >= 1994 and int(year) <= 1999:
            donwload_urls.append(pro_link_ele["href"])
        
        for du in donwload_urls:
            output_file = output_dir / f"en-{du.split('/')[-1]}"

            # Skip if file already exists
            if output_file.exists():
                continue

            pdf_resp = req_session.get(du)
            output_file.write_bytes(pdf_resp.content)


if __name__ == "__main__":
    main()