# /// script
# dependencies = [
#    "requests",
#    "beautifulsoup4",
#    "pypdf",
# ]
# ///


import io
from collections.abc import Iterable
from functools import partial
from getpass import getpass
from pathlib import Path

import pypdf
import requests
from bs4 import BeautifulSoup


def get_token(s: requests.Session | None):
    get_token = (s or requests).get("https://moodle.usth.edu.vn/login/index.php")
    n = BeautifulSoup(get_token.content, features="lxml").select_one(
        "form[action='https://moodle.usth.edu.vn/login/index.php'] input[name=logintoken]"
    )
    return n and n.get("value")


def merge_pdfs(pdfs: Iterable[bytes]) -> bytes:
    merger = pypdf.PdfWriter()
    for f in pdfs:
        with io.BytesIO(f) as s:
            merger.append(s)
    with io.BytesIO() as f:
        merger.write(f)
        return f.getvalue()


def real(s: requests.Session, usrname: str, passwd: str) -> bool:
    c = s.post(
        "https://moodle.usth.edu.vn/login/index.php",
        data={
            "username": usrname,
            "password": passwd,
            # "rememberusername": 1,
            "anchor": "",
            "logintoken": get_token(s),
        },
    ).content

    return (
        BeautifulSoup(c, features="lxml").select_one("a#loginerrormessage") is not None
    )


def ts_pdf(s: requests.Session, url: str) -> bytes:
    u = s.get(url, stream=True)
    u.raise_for_status()
    if not u.content:
        raise ValueError(f"{url}: what the fuck")
    if u.headers.get("Content-Type") != "application/pdf":
        raise ValueError(f"{url}: content type: {u.headers.get('Content-Type')}")
    data = b"".join(u.iter_content(8192))
    if not data.startswith(b"%PDF"):
        raise ValueError(f"{url}: Not a PDF")
    if b"%%EOF" not in data[-1024:]:
        raise ValueError(f"{url}: PDF looks truncated")
    return data


def main():
    u, p = input("Username: "), getpass("Password: ")
    pdfs = (  # example
        "https://moodle.usth.edu.vn/pluginfile.php/91136/mod_resource/content/1/Chapter%201%20v1.pdf",
        "https://moodle.usth.edu.vn/pluginfile.php/91137/mod_resource/content/1/Chapter%202.pdf",
        "https://moodle.usth.edu.vn/pluginfile.php/91138/mod_resource/content/1/Chapter%203%20%20.pdf",
        "https://moodle.usth.edu.vn/pluginfile.php/91964/mod_resource/content/1/Chapter%204%20%5BAutosaved%5D.pdf",
        "https://moodle.usth.edu.vn/pluginfile.php/91965/mod_resource/content/1/Chapter%206.pdf",
        "https://moodle.usth.edu.vn/pluginfile.php/92412/mod_resource/content/1/Chapter%209.pdf",
    )
    with requests.Session() as s:
        real(s, u, p)
        ppdf = partial(ts_pdf, s)
        b = map(ppdf, pdfs)
        Path("merged_.pdf").write_bytes(merge_pdfs(b))
    print("write done to merged_.pdf")


if __name__ == "__main__":
    main()