main.py

import os
import time
import base64
import requests
import re

from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError

# If modifying these scopes, delete the file token.json.
last_message_id = None
SCOPES = ["https://www.googleapis.com/auth/gmail.readonly"]

def set_last_message_id():
    # Get the last message ID from the PDFs folder
    if os.path.exists("kindle_pdfs"):
        pdfs = os.listdir("kindle_pdfs")
        if pdfs:
            pdfs.sort(key=lambda x: float(x.split("_")[1]))
            return pdfs[-1].split("_")[2].split(".")[0]

def auth():
    global SCOPES
    creds = None
    # The file token.json stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    if os.path.exists("token.json"):
        creds = Credentials.from_authorized_user_file("token.json", SCOPES)
    # If there are no (valid) credentials available, let the user log in.
    if not creds or not creds.valid:
        print("No valid credentials")
        if creds and creds.expired and creds.refresh_token:
            print("Refreshing credentials, please wait...")
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                "credentials.json", SCOPES
            )
            creds = flow.run_local_server(port=0)
            # Save the credentials for the next run
            with open("token.json", "w") as token:
                token.write(creds.to_json())
    return creds

def fetch_pdf(pdf_link, filename):
    # Download the PDF
    response = requests.get(pdf_link)
    with open(f"kindle_pdfs/{filename}.pdf", "wb") as pdf:
        pdf.write(response.content)

def main(creds):
    global last_message_id
    try:
        # Call the Gmail API
        service = build("gmail", "v1", credentials=creds)

        # Get the last email from <do-not-reply@amazon.com>
        results = (
            service.users()
            .messages()
            .list(userId="me", q="from:do-not-reply@amazon.com", maxResults=1)
            .execute()
        )
        # Store the whole message
        message = (
            service.users()
            .messages()
            .get(userId="me", id=results["messages"][0]["id"])
            .execute()
        )

        # If the last message is the same as the previous one, return
        if last_message_id == results["messages"][0]["id"]:
            return
        last_message_id = results["messages"][0]["id"]

        # Get the content of the email
        b64content = "".join(part["body"]["data"] for part in message["payload"]["parts"] if part["mimeType"] == "text/plain")
        content = base64.urlsafe_b64decode(b64content).decode("utf-8")
        # Get the link to the PDF
        pdf_link = [link for link in re.findall(r'\((https?://[^\s)]+)\)', content) if "kindle" in link]
        if not pdf_link:
            return
        pdf_link = pdf_link[0]
        # Set the filename to the current time and the message ID
        filename = f"{message["snippet"].split("&quot;")[1].replace(" ", "-")}_{time.time()}_{results['messages'][0]['id']}"
        # Download the PDF
        fetch_pdf(pdf_link, filename)
        print(f"Downloaded {filename.split('_')[0]}.pdf")

    except HttpError as error:
        # TODO(developer) - Handle errors from gmail API.
        print(f"An error occurred: {error}")


if __name__ == "__main__":
    creds = auth()
    last_message_id = set_last_message_id()
    while True:
        main(creds)
        time.sleep(2)