#!/usr/bin/env python

"""Script for papeless-ngx to decrypt pdf files secured with a password
Passwords to check ar in file /usr/src/paperless/scripts/passwords.txt
Original from https://piep.tech/posts/automatic-password-removal-in-paperless-ngx/
"""

import sys
import os
import pikepdf


PWD_PATH = "/usr/src/paperless/scripts/passwords.txt"
#PWD_PATH = "input/passwords.txt"


def read_passwords_from_file():
    """Read Paswors from file"""
    passwords = []

    with open(PWD_PATH, "r", encoding="utf-8") as f:
        passwords = f.readlines()

    passwords = list(filter(len, map(str.strip, passwords)))
    if not passwords:
        print("Empty password file")

    return passwords


def unlock_pdf(file_path, password_list):
    """Removes Password from PDF. A list of passwords is tried through."""
    for pwd in password_list:
        try:
            with pikepdf.open(file_path, password=pwd, allow_overwriting_input=True) as pdf:
                pdf.save(file_path)
                return True
        except pikepdf.PasswordError:
            continue
    return False


def is_pdf_encrypted(file_path):
    """Checks if a PDF file is encrypted"""
    try:
        with pikepdf.open(file_path) as pdf:
            return pdf.is_encrypted
    except pikepdf.PasswordError:
        return True


def is_pdf(file_path):
    """Check if Filename ends with PDF. File is not opened"""
    return os.path.splitext(file_path)[-1].lower() == ".pdf"


if __name__ == "__main__":

    doc_path = os.environ.get('DOCUMENT_WORKING_PATH')

    if not os.path.exists(doc_path):
        print(f"Document {doc_path} not found.")
        sys.exit(1)

    if not is_pdf(doc_path):
        print(f"Document {doc_path} is not a PDF. So no decryption needed.")
        sys.exit(0)

    if not is_pdf_encrypted(doc_path):
        print(f"Document {doc_path} was already decrypted and no password needed.")
        sys.exit(0)

    pwds = read_passwords_from_file()
    if unlock_pdf(doc_path, pwds):
        print(f"Document {doc_path} successfull decrypted.")
        sys.exit(0)
    else:
        print(f"Document {doc_path} could not be decrypted.")
        sys.exit(1)