lex_restapi.py

# Amazon Lex API request

# See: http://docs.aws.amazon.com/general/latest/gr/sigv4_signing.html
# This version makes a POST request and passes request parameters
# in the body (payload) of the request. Auth information is passed in
# an Authorization header.

import datetime
import hashlib
import hmac
import os
import sys
import requests
import json

# easy_install pip
# pip install requests

# ************* REQUEST VALUES *************
method = 'POST'
service = 'lex'
host = 'runtime.lex.us-east-1.amazonaws.com'
region = 'us-east-1'
endpoint = 'https://runtime.lex.us-east-1.amazonaws.com'
ready = False

while (ready != True):
    request_text = input("Input: ")

    request_parameters = '{"inputText": "' + request_text + '", "sessionAttributes": {"attr_name" : "value"}}'  # request text (and optional session attributes) to the Lex bot
    # for post_action 'content' - sessionAttributes are passed as the x-amz-lex-session-attributes HTTP header.

    bot_name = 'HelloJaffar'  # bot name
    bot_alias = 'JaffarTest'  # bot's alias
    user_id = 'guest'  # some user-id - not used for authentication
    # for text request (json); {"inputText": "string", "sessionAttributes": {"string" : "string" }})
    post_action = 'text'
    # for stream request (text or audio stream)
    # post_action = 'content'

    # POST requests use a cdeontent type hear. For Lex,
    # the content is JSON or stream.

    # for post_action = 'text':
    content_type = 'application/json'


    # for post_action = 'content', audio stream in PCM format:
    # content_type = 'audio/l16;rate=16000;channels=1'
    # content_type = 'audio/x-l16;sample-rate=16000;channel-count=1'

    # for post_action = 'content', audio stream in Opus format:
    # content_type = 'audio/x-cbr-opus-with-preamble;preamble-size=0;bit-rate=256000;frame-size-milliseconds=4'

    # for post_action = 'content', text:
    # content_type = 'text/plain;charset=utf-8'

    # Key derivation functions. See:
    # http://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-python
    def sign(key, msg):
        return hmac.new(key, msg.encode('utf-8'), hashlib.sha256).digest()


    def getSignatureKey(key, dateStamp, regionName, serviceName):
        kDate = sign(('AWS4' + key).encode('utf-8'), dateStamp)
        kRegion = sign(kDate, regionName)
        kService = sign(kRegion, serviceName)
        kSigning = sign(kService, 'aws4_request')
        return kSigning


    # Read AWS access key from env. variables or configuration file. Best practice is NOT
    # to embed credentials in code.
    # access_key = os.environ.get('AWS_ACCESS_KEY_ID')
    # secret_key = os.environ.get('AWS_SECRET_ACCESS_KEY')
    access_key = '' 
    secret_key = ''
    if access_key is None or secret_key is None:
        print('No access key is available.')
        sys.exit()

    # Create a date for headers and the credential string
    t = datetime.datetime.utcnow()
    amz_date = t.strftime('%Y%m%dT%H%M%SZ')  # '20170714T010101Z'
    date_stamp = t.strftime('%Y%m%d')  # Date w/o time, used in credential scope  '20170714'

    # ************* TASK 1: CREATE A CANONICAL REQUEST *************
    # http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html

    # Step 1 is to define the verb (GET, POST, etc.)--already done.

    # Step 2: Create canonical URI--the part of the URI from domain to query
    # string (use '/' if no path)
    canonical_uri = '/bot/' + bot_name + '/alias/' + bot_alias + '/user/' + user_id + '/' + post_action

    ## Step 3: Create the canonical query string. In this example, request
    # parameters are passed in the body of the request and the query string
    # is blank.
    canonical_querystring = ''

    # Step 4: Create the canonical headers. Header names must be trimmed
    # and lowercase, and sorted in code point order from low to high.
    # Note that there is a trailing \n.
    canonical_headers = 'content-type:' + content_type + '\n' + 'host:' + host + '\n' + 'x-amz-date:' + amz_date + '\n'

    # Step 5: Create the list of signed headers. This lists the headers
    # in the canonical_headers list, delimited with ";" and in alpha order.
    # Note: The request can include any headers; canonical_headers and
    # signed_headers include those that you want to be included in the
    # hash of the request. "Host" and "x-amz-date" are always required.
    # For Lex, content-type and x-amz-target are also required.
    signed_headers = 'content-type;host;x-amz-date'

    # Step 6: Create payload hash. In this example, the payload (body of
    # the request) contains the request parameters.
    payload_hash = hashlib.sha256((request_parameters).encode('utf-8')).hexdigest()

    # Step 7: Combine elements to create create canonical request
    canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers + '\n' + payload_hash

    # ************* TASK 2: CREATE THE STRING TO SIGN*************
    # Match the algorithm to the hashing algorithm you use, either SHA-1 or
    # SHA-256 (recommended)
    algorithm = 'AWS4-HMAC-SHA256'
    credential_scope = date_stamp + '/' + region + '/' + service + '/' + 'aws4_request'
    string_to_sign = algorithm + '\n' + amz_date + '\n' + credential_scope + '\n' + hashlib.sha256(
        (canonical_request).encode('utf-8')).hexdigest()

    # ************* TASK 3: CALCULATE THE SIGNATURE *************
    # Create the signing key using the function defined above.
    signing_key = getSignatureKey(secret_key, date_stamp, region, service)

    # Sign the string_to_sign using the signing_key
    signature = hmac.new(signing_key, string_to_sign.encode('utf-8'), hashlib.sha256).hexdigest()

    # ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
    # Put the signature information in a header named Authorization.
    authorization_header = algorithm + ' ' + 'Credential=' + access_key + '/' + credential_scope + ', ' + 'SignedHeaders=' + signed_headers + ', ' + 'Signature=' + signature

    # For Lex, the request can include any headers, but MUST include "host", "x-amz-date",
    # "x-amz-target", "content-type", and "Authorization". Except for the authorization
    # header, the headers must be included in the canonical_headers and signed_headers values, as
    # noted earlier. Order here is not significant.
    # # Python note: The 'host' header is added automatically by the Python 'requests' library.
    headers = {'Content-Type': content_type,
               'X-Amz-Date': amz_date,
               'Authorization': authorization_header}

    # ************* SEND THE REQUEST *************
    print('\nBEGIN REQUEST:')
    print('Request URL = ' + endpoint)

    r = requests.post(endpoint + canonical_uri, data=request_parameters, headers=headers)
    rjdata = json.loads(r.text)  # LOAD JSON RESPONSE
    print('\nRESPONSE:')

    # print ('Response code: %d\n' % r.status_code)
    # print (r.text)
    # print (rjdata['message'])
    if (r.status_code == 200):
        dialogState = rjdata['dialogState']  # GET CURRENT DIALOG STATE
        if (dialogState.startswith('Elicit')):
            print(rjdata['message'])
            print('')

        if (dialogState.startswith('ReadyForFulfillment')):
            print('ReadyForFulfillment;')
            print('Intent:' + rjdata['intentName'])
            # print ('Slots: ')
            # rjdata['slots'].items()
            ready = True
    else:
        errorMessage = rjdata['message']  # GET ERROR MESSAGE (if any)
        if (erorrMessage != None):
            print(rjdata['message'])
        else:
            print('Error, terminating. bot')
print('Bye bye!')