import requests
import base64
from bs4 import BeautifulSoup
import re
import jwt
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
import os
import hashlib

class GmailDataExtractor:

    def __init__(self,jwt:str  , user_input: str = None) -> None:
        if jwt is None :
            self.error = "Error"
        else:
            self.__jwt = jwt
            self.__user_input = user_input
            self.error = None
            self.__secret_key = 'nkldjlncbamjlklwjeklwu24898h*&#Ujnfjf34893U5HSJFBSKFSHFNSK*$*W_ 3OWU'

    def __validate_jwt_token(self):
        try:
            payload = jwt.decode(self.jwt, self.secret_key, algorithms=["HS256"])
            access_token = payload.get("access_token")
            if access_token:
                return access_token
            else:
                raise ValueError("Invalid JWT token: Missing access token")
        except jwt.ExpiredSignatureError:
            raise ValueError("Invalid JWT token: Expired token")
        except jwt.InvalidTokenError:
            raise ValueError("Invalid JWT token: Token verification failed")

    def __fetch_messages(self) -> list:
        """
        Fetches messages from the Gmail API.

        Args:
            gmail_url (str): The URL for the Gmail API request.
            access_token (str): The access token for authenticating with Gmail API.

        Returns:
            list: A list of message objects retrieved from the Gmail API.

        Raises:
            RuntimeError: If there is an issue while fetching messages from the Gmail API.
            
        """

        """currently not implementing jwt for testing purposes
        replace every access_token with jwt function directly which returns the access token"""
        access_token = self.__jwt
        print("access token")
        print(access_token)
        receipt_query = f'(subject:"your order" OR subject:receipts OR subject:receipt OR subject:invoice OR subject:invoice OR category:purchases)'
        if self.__user_input is not None:
            receipt_query = f'(subject:"your order" OR subject:receipts OR subject:receipt OR subject:invoice OR subject:invoice OR category:purchases)  AND subject:{self.__user_input}'
        gmail_url = f"https://www.googleapis.com/gmail/v1/users/me/messages?q={receipt_query}&maxResults=3"
        def __fetch_page(url):
            response = requests.get(url, headers={"Authorization": f"Bearer {access_token}"})
            response.raise_for_status()  # Raise error if the request fails
            data = response.json()
            return data.get("messages", []), data.get("nextPageToken")

        messages = []
        page_token = None
        try:
            while True:
                url = f"{gmail_url}&pageToken={page_token}" if page_token else gmail_url
                page_messages, page_token = __fetch_page(url)
                messages.extend(page_messages)
                if not page_token:
                    break
        except requests.RequestException as e:
            raise RuntimeError(f"Error fetching messages from Gmail API: {str(e)}")
        
        return messages

    def __fetch_message_data(self, message_id: str) -> dict:
        """
        Fetches message data from the Gmail API.

        Args:
            message_id (str): The ID of the message to fetch.

        Returns:
            dict: Message data retrieved from the Gmail API.

        Raises:
            RuntimeError: If there is an issue while fetching message data from the Gmail API.
        """
        print("fetch_message_data")
        message_url = f"https://www.googleapis.com/gmail/v1/users/me/messages/{message_id}"
        try:
            response = requests.get(message_url, headers={"Authorization": f"Bearer {self.__jwt}"})
            response.raise_for_status()  # Raise error if the request fails
            return response.json()
        except requests.RequestException as e:
            raise RuntimeError(f"Error fetching message data from Gmail API: {str(e)}")

    def __fetch_attachment_data(self, message_id: str, attachment_id: str) -> dict:
        """
        Fetches attachment data from the Gmail API.

        Args:
            message_id (str): The ID of the message containing the attachment.
            attachment_id (str): The ID of the attachment to fetch.

        Returns:
            dict: Attachment data retrieved from the Gmail API.

        Raises:
            RuntimeError: If there is an issue while fetching attachment data from the Gmail API.
        """
        print("fetch_attachment_data")
        attachment_url = f"https://www.googleapis.com/gmail/v1/users/me/messages/{message_id}/attachments/{attachment_id}"
        try:
            response = requests.get(attachment_url, headers={"Authorization": f"Bearer {self.__jwt}"})
            response.raise_for_status()  # Raise error if the request fails
            return response.json()
        except requests.RequestException as e:
            raise RuntimeError(f"Error fetching attachment data from Gmail API: {str(e)}")
        
    def __process_message(self, message: dict) -> tuple:
        """
        Processes a single message.

        Args:
            message (dict): The message to process.

        Returns:
            tuple: A tuple containing the subject (str), body (str), links (list of str), 
                and base64 data if it contains an document attachment in the form of pdf, docx, ppt or any file format indicating whether the message contains an attachment.

        Raises:
            RuntimeError: If there is an issue while fetching message data from the Gmail API.
        """
        print("process_messages")
        message_id = message.get("id")
        encrypted_message_id = self.encrypt_message_id(message_id)
        if not message_id:
            return None, None, [], False
        subject=''
        message_data = self.__fetch_message_data(message_id)
        if 'payload' in message_data and 'headers' in message_data['payload']:
            headers = message_data['payload']['headers']
            for header in headers:
                if header['name'] == 'Subject':
                    subject = header['value']
        body = ''
        text=''
        links = []
        has_attachment = False

        if 'payload' in message_data and 'parts' in message_data['payload']:
            parts = message_data['payload']['parts']
            payload = message_data['payload']['headers']
            print("printing headers response")
            print(payload)
            company_from_gmail = ''
            
            #Extracting the domain name from the senders email
            for fromdata in payload:
                if fromdata['name'] == 'From':
                    company_from_gmail = self.extract_domain_from_email(fromdata['value'])
                    break

            for part in parts:
                if 'mimeType' not in part:
                    continue

                mime_type = part['mimeType']
                
                if mime_type == 'text/plain' or mime_type == 'text/html':
                    body_data = part['body'].get('data', '')
                    body = base64.urlsafe_b64decode(body_data)
                    text= self.extract_text(body)

                if 'body' in part and 'attachmentId' in part['body']:
                    attachment_id = part['body']['attachmentId']
                    attachment_data = self.__fetch_attachment_data(message_id, attachment_id)
                    data = attachment_data.get("data", "")
                    filename = part.get("filename", "untitled.txt")

                    if data:
                        # Save only the first 10 characters of the attachment data
                        return subject,text ,{"filename":filename , "data":data} , company_from_gmail , message_id

        return subject, text,None , company_from_gmail , message_id

    def encrypt_message_id(self,message_id:str):
        key = os.getenv('AES_KEY').encode('utf-8')[:32]
        message_id_bytes = message_id.encode('utf-8')
        iv = os.urandom(16)
        # Initialize AES cipher with the key and CBC mode
        cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=default_backend())
        
        # Create a encryptor object
        encryptor = cipher.encryptor()
        
        # Pad the message_id to be a multiple of 16 bytes (AES block size)
        # This is necessary for AES encryption
        message_id_padded = message_id_bytes.ljust(32, b'\0')
        
        # Encrypt the padded message_id
        ciphertext = encryptor.update(message_id_padded) + encryptor.finalize()
        return ciphertext
        

    def extract_domain_from_email(self,email_string):
        # Extracting the email address using regex
        email_address = re.search(r'[\w\.-]+@[\w\.-]+', email_string).group()

        # Extracting the domain name from the email address
        domain = email_address.split('@')[-1].split('.')[0]
        if email_address and domain :
            return domain
        else:
            return None
        
    
    def extract_text(self,html_content:str):
        """
        Extracts text and links from HTML content.

        Args:
            html_content (str): The HTML content to process.

        Returns:
            tuple: A tuple containing the extracted text (str) and links (list of tuples).

        Raises:
            ValueError: If the input HTML content is empty or None.
        """
        if not html_content:
            raise ValueError("HTML content is empty or None")

        soup = BeautifulSoup(html_content, 'html.parser')

        # Extract text
        text = soup.get_text(separator=' ')
        text = re.sub(r'\s+', ' ', text).strip()
        print("Printing the extracted text from the html")
        print(text)
        print()
        print()
        # Extract links
        links = [(link.text, link['href']) for link in soup.find_all('a', href=True)]

        return text
    
    def extract_messages(self) -> dict:
        """
        Extracts messages based on the provided brand name.

        Args:
            brand_name (str): The brand name to search for in email subjects.
            jwt_token (str): The JWT token for authentication.

        Returns:
            dict: A dictionary containing the extracted messages with their subjects, bodies, links, and attachment statuses.
            format:{"results":[{"subjec":"test subject" , "body":"it would be text" , "attachment_data":{"filename":base64URL format}},{second message with same content of subject , body , attachment_data}]}

        """
        print("entered the extract messages")
        messages = self.__fetch_messages()
        results = []
        for message in messages:
            subject, body, attachment_data , company_name , encrypt_mssg_id = self.__process_message(message)

            """ Handling None values """
            body = body if body is not None else None
            attachment_data = attachment_data if attachment_data is not None else {}
            company_associated = company_name if company_name is not None else None
            en_msg_id = encrypt_mssg_id if encrypt_mssg_id is not None else None

            results.append({"body": body, "attachment_data": [attachment_data] ,'company_associated':company_associated , "message_id":en_msg_id})

        return {"results": results}

# obj = GmailDataExtractor("abcd","user_input")
# print(obj.error)