(Tcl) Using the OAuth2 Authorization Token in REST API Calls

Demonstrates how to use an OAuth2 authorization token in REST API calls after obtaining it.

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load ./chilkat.dll

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# This example demonstrates how to include the OAuth2 authorization token in HTTP requests (REST API calls).
# An OAuth2 authorization token is typically in JSON format, and looks something like this:

# {
#   "token_type": "Bearer",
#   "scope": "openid profile User.ReadWrite Mail.ReadWrite Mail.Send Files.ReadWrite User.Read Calendars.ReadWrite Group.ReadWrite.All",
#   "expires_in": 3600,
#   "ext_expires_in": 3600,
#   "access_token": "EwCQA8l6...rW5az09bI0C",
#   "refresh_token": "MCZhZ...6jBNRcpuQW",
#   "id_token": "eyJ0eXAi...kcuQQrT03jMyA",
#   "expires_on": "1569281808"
# }

# A few notes about the JSON above:
# 
# 1) Different OAuth2 implementations (servers) may have different JSON members. 
#    The important ones for this discussion are "access_token" and "refresh_token".   
#    These members should always be named exactly "access_token" and "refresh_token".  
#    (I've never seen them named differently, although I don't think it's a formal standard.)
# 
# 2) The "id_token" is present if you obtained the OAuth2 authorization token including "openid" in the scope.
#    It contains information about the user.  It is a JWT (per the OIDC specification) and here is the Chilkat
#    example for decoding the id_token.
# 
# 3) If you don't have a "refresh_token" in your JSON, some REST API's require "offline_access" to be included
#    in the scope when obtaining the OAuth2 token.
# 
# 4) IMPORTANT: Quite often, access_token's are only valid for a limited amount of time.  (Often just 1 hour (i.e. 3600 seconds)).
#    When the access token expires, your HTTP request will fail with a 401 Unauthorized status response.  This is where your application
#    can automatically recover by fetching a new access_token and re-sending the request.  I'll explain...  
#    Usually getting an OAuth2 token for a user requires interactive approval from the user in a browser.
#    However, refreshing the access_token does NOT require user interaction.  You should design
#    your application to automatically recover from an expired access token by 
#    (A) Automatically fetch a new access_token using the refresh_token as shown in this example.
#    (B) Persist the new JSON to wherever you're storing the access token, such as in a file or database record.  You'll need it for the next time you refresh.
#    (C) Update the http.AuthToken or rest.Authorization property (as shown below)
#    (D) Re-send the request using the updated auth token.
#    The above 4 steps (A, B, C, D) can be automatic such that the user never notices, except for a small delay in performance.

# When your application obtains the OAuth2 access token, it should store the JSON in persistent manner, such as in 
# a file, a database record, etc.  The "access_token" is used by your application when sending REST requests.  Typically, it is sent
# in the Authorization request header.  For example:
# 
# Authorization: Bearer <token>
# 

# -----
# Chilkat has two classes for sending HTTP requests.  One is named "Http" and the other is named "Rest".  Either can be used.  
# Once you become familiar with both, you'll find that some requests are more convenient to code in one or the other.
# 
# I'll demonstrate how to get the access_token from the JSON and add the Authorization header for both cases.
# 

# ----
# ---- (1) Get the access_token ----
set json [new_CkJsonObject]

set success [CkJsonObject_LoadFile $json "qa_data/tokens/myToken.json"]
if {$success != 1} then {
    puts [CkJsonObject_lastErrorText $json]
    delete_CkJsonObject $json
    exit
}

# Get the access_token member.
set accessToken [CkJsonObject_stringOf $json "access_token"]

# ----
# ---- (2) Demonstrate adding the "Authorization: Bearer <token>" header using Chilkat Http ----
set http [new_CkHttp]

# Setting the AuthToken property causes the "Authorization: Bearer <token>" header to be added to each request.
CkHttp_put_AuthToken $http $accessToken

# For example:
set responseStr [CkHttp_quickGetStr $http "https://example.com/someApiCall"]

# Another example:
set req [new_CkHttpRequest]

# ...
# resp is a CkHttpResponse
set resp [CkHttp_PostUrlEncoded $http "https://example.com/someApiCall" $req]
# ...
delete_CkHttpResponse $resp

# In both of the above cases, the "Authorization: Bearer <token>" header is automatically added to each request.

# ----
# ---- (3) Add the Authorization header using Chilkat Rest ----
set rest [new_CkRest]

set success [CkRest_Connect $rest "example.com" 443 1 1]
# ...

# Set the Authorization property to "Bearer <token>"
set sbAuthHeaderVal [new_CkStringBuilder]

CkStringBuilder_Append $sbAuthHeaderVal "Bearer "
CkStringBuilder_Append $sbAuthHeaderVal $accessToken
CkRest_put_Authorization $rest [CkStringBuilder_getAsString $sbAuthHeaderVal]

# All requests sent by the rest object will now include the "Authorization: Bearer <token>" header.

# For example:
set responseStr [CkRest_fullRequestNoBody $rest "GET" "/someApiCall"]

delete_CkJsonObject $json
delete_CkHttp $http
delete_CkHttpRequest $req
delete_CkRest $rest
delete_CkStringBuilder $sbAuthHeaderVal