Python OAuth flow for Intervals.icu Lambda

intervals_oauth_lambda.py

import os
from base64 import b64decode

# Handles a call from the intervals.icu OauthAPI, requests the auth token and returns this in a redirect URL
def lambda_handler(event, context):
    
    # Generic error object to handle errors
    def createErrorObject(reason):
        return {
            'statusCode': 301,
            'headers': {
                'Location': f'intervalsapp:login?error=true&reason={reason}'
            }
        }
    
    # Ensure query parameters exist
    if not 'queryStringParameters' in event:
        return createErrorObject("No queryStringParameters")
    qsp = event['queryStringParameters']
    
    # Ensure there is a code in the query string parameters
    if not 'code' in qsp:
        return createErrorObject("No code available")
    code = qsp['code']
    
    client_secret = os.environ['client_secret']
    
    # Construct the call back to the intervals.icu server
    url = 'https://intervals.icu/api/oauth/token'
    data = {
        'client_id': 12,
        'client_secret': client_secret,
        'code': code
    }
    
    # Send the request
    http = urllib3.PoolManager()
    response = http.request(
        'POST', 
        url,
        fields=data
    )
    
    print(response.status)
    
    # Ensure the request was successful
    if response.status == 200:
        # Parse the json response
        response_dict = json.loads(response.data.decode('utf-8'))
        
        # Ensure all fields are present
        if not 'token_type' in response_dict:
            return createErrorObject("No token_type")
        if not 'access_token' in response_dict:
            return createErrorObject("No access_token")
        if not 'scope' in response_dict:
            return createErrorObject("No scope")
        if not 'athlete' in response_dict:
            return createErrorObject("No athlete")
        if not 'id' in response_dict['athlete']:
            return createErrorObject("No id")
        if not 'name' in response_dict['athlete']:
            return createErrorObject("No name")

        # Obtain the fields
        token_type = response_dict['token_type']
        access_token = response_dict['access_token']
        scope = response_dict['scope']
        athlete_id = response_dict['athlete']['id']
        athlete_name = response_dict['athlete']['name']
        
        # Create redirect response
        return {
            'statusCode': 301,
            'headers': {
                'Location': f'intervalsapp:login?token_type={token_type}&access_token={access_token}&scope={scope}&athlete_id={athlete_id}&athlete_name={athlete_name}'
            }
        }
    else:
        # Handle invalid response from server
        return createErrorObject(f"Incorrect response from server: {response.status}")