# src/services/gmail_api.py
import os
import re
import base64
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials

STORAGE_DIR = os.path.abspath("./storage")

def sanitize_filename(name):
    clean = re.sub(r'[\\/*?:"<>|]', "", name or "Untitled")
    return clean[:80].strip()

class GmailDownloader:
    SCOPES = ['https://www.googleapis.com/auth/gmail.readonly']

    def __init__(self, credentials_json="credentials.json", account_email="slohning@gmail.com"):
        self.account_email = account_email
        self.creds_json = credentials_json
        self.service = self._authenticate()

    def _authenticate(self):
        if not os.path.exists(self.creds_json):
            return None

        creds = None
        token_file = 'token_gmail.json'
        if os.path.exists(token_file):
            creds = Credentials.from_authorized_user_file(token_file, self.SCOPES)
        if not creds or not creds.valid:
            if creds and creds.expired and creds.refresh_token:
                creds.refresh(Request())
            else:
                flow = InstalledAppFlow.from_client_secrets_file(self.creds_json, self.SCOPES)
                creds = flow.run_local_server(port=0)
            with open(token_file, 'w') as token:
                token.write(creds.to_json())
        return build('gmail', 'v1', credentials=creds)

    def download_inbox(self, callback_signal):
        if not self.service:
            callback_signal.emit(f"[{self.account_email}] Auth Error: Missing {self.creds_json} configuration.")
            return []

        results = self.service.users().messages().list(userId='me', maxResults=20, q="label:INBOX").execute()
        messages = results.get('messages', [])
        
        extracted = []
        os.makedirs(STORAGE_DIR, exist_ok=True)

        for m in messages:
            msg_id = m['id']
            # Fetch raw RFC 822 format
            raw_msg = self.service.users().messages().get(userId='me', id=msg_id, format='raw').execute()
            
            meta_msg = self.service.users().messages().get(userId='me', id=msg_id, format='full').execute()
            headers = meta_msg.get('payload', {}).get('headers', [])
            
            subject = next((h['value'] for h in headers if h['name'].lower() == 'subject'), 'No Subject')
            sender = next((h['value'] for h in headers if h['name'].lower() == 'from'), 'Unknown')
            date_str = next((h['value'] for h in headers if h['name'].lower() == 'date'), 'UnknownDate')

            eml_data = base64.urlsafe_b64decode(raw_msg['raw'].encode('ASCII'))
            
            fname = f"GMAIL_{sanitize_filename(subject)}_{msg_id[-6:]}.eml"
            fpath = os.path.abspath(os.path.join(STORAGE_DIR, fname))
            
            with open(fpath, "wb") as f:
                f.write(eml_data)
                
            extracted.append({
                "account": self.account_email,
                "id": msg_id,
                "subject": subject,
                "sender": sender,
                "date": date_str,
                "path": fpath
            })
            callback_signal.emit(f"[{self.account_email}] Downloaded: {fname}")
            
        return extracted