from functools import wraps
from pathlib import Path
from re import compile
from subprocess import run
from typing import Callable, Dict, Iterable, List, Mapping, ParamSpec, Tuple, TypeVar


WORKDIR = Path.cwd()
PROJECT_DIR = Path(__file__).resolve().absolute().parent.relative_to(WORKDIR)
OUTPUT_FILE = PROJECT_DIR / "Lecture.pdf"
idRegex = compile(r"^(\d+)\..+$")

def get_id(file: Path):
    matches = idRegex.search(file.name)
    if matches is None:
        print(f"WARNING: File '{file.name}' hasn't got an id in the filename!")
        return None
    return int(matches.group(1))

def not_output_file(file: Path):
    global OUTPUT_FILE
    return file != OUTPUT_FILE

T = TypeVar("T")
Params = ParamSpec("Params")

def get_sequential(f: Callable[Params, Mapping[int, T]]) -> Callable[Params, List[T]]:
    @wraps(f)
    def wrapper(*args: Params.args, **kwargs: Params.kwargs):
        items = f(*args, **kwargs)
        def get_or_raise(i: int):
            item = items.get(i)
            if item is None:
                raise Exception(f"Expected Item with index {i}, but it was not found!")
            return item
        return list(map(get_or_raise, range(len(items))))
    return wrapper

def only_unique_ids(f: Callable[Params, Iterable[Tuple[int, T]]]) -> Callable[Params, Dict[int, T]]:
    @wraps(f)
    def wrapper(*args: Params.args, **kwargs: Params.kwargs):
        items: Dict[int, T] = dict()
        for uid, pdf in f(*args, **kwargs):
            existing = items.get(uid)
            if existing is not None:
                raise ValueError(f"Got item '{pdf}' with id {uid}, but '{existing}' already has that id!")
            items[uid] = pdf
        return items
    return wrapper

@get_sequential
@only_unique_ids
def get_files(path: Path):
    global OUTPUT_FILE
    files = path.rglob("*.pdf")
    for file in files:
        if file == OUTPUT_FILE: continue
        number = get_id(file)
        if number is None: continue
        yield number, file

def main():
    pdfs = get_files(PROJECT_DIR)
    for pdf in pdfs:
        print(f"Adding file {pdf.name}")
    cmd = ["pdftk"]
    cmd.extend(map(str, pdfs))
    cmd.append("cat")
    cmd.append("output")
    cmd.append(str(OUTPUT_FILE))
    run(cmd)

if __name__ == "__main__":
    main()