(PureBasic) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkOAuth2.pb"
IncludeFile "CkDateTime.pb"

Procedure ChilkatExample()

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

    ; See Get HMRC Access Token 
    ; for sample code showing how to obtain a HMRC access token for desktop apps.

    ; It is assumed we previously obtained an OAuth2 access token for HMRC.

    jsonToken.i = CkJsonObject::ckCreate()
    If jsonToken.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkJsonObject::ckLoadFile(jsonToken,"qa_data/tokens/hmrc.json")
    If success <> 1
        Debug "Failed to load hmrc.json"
        CkJsonObject::ckDispose(jsonToken)
        ProcedureReturn
    EndIf

    ; The access token JSON looks something like this:

    ; {
    ;   "token_type": "Bearer",
    ;   "scope": "user_impersonation",
    ;   "expires_in": "3599",
    ;   "ext_expires_in": "0",
    ;   "expires_on": "1524783438",
    ;   "not_before": "1524779538",
    ;   "resource": "https://mydomain.api.crm.dynamics.com",
    ;   "access_token": "...",
    ;   "refresh_token": "...",
    ;   "id_token": "..."
    ; }

    oauth2.i = CkOAuth2::ckCreate()
    If oauth2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkOAuth2::setCkTokenEndpoint(oauth2, "https://test-api.service.hmrc.gov.uk/oauth/token")

    ; Replace these with actual values.
    CkOAuth2::setCkClientId(oauth2, "HMRC-CLIENT-ID")
    CkOAuth2::setCkClientSecret(oauth2, "HMRC-CLIENT-SECRET")

    ; Get the "refresh_token"
    CkOAuth2::setCkRefreshToken(oauth2, CkJsonObject::ckStringOf(jsonToken,"refresh_token"))

    ; Send the HTTP POST to refresh the access token..
    success = CkOAuth2::ckRefreshAccessToken(oauth2)
    If success <> 1
        Debug CkOAuth2::ckLastErrorText(oauth2)
        CkJsonObject::ckDispose(jsonToken)
        CkOAuth2::ckDispose(oauth2)
        ProcedureReturn
    EndIf

    ; Load the access token response into the json object 
    CkJsonObject::ckLoad(jsonToken,CkOAuth2::ckAccessTokenResponse(oauth2))

    ; If an "expires_on" member does not exist, then add the JSON member by
    ; getting the current system date/time and adding the "expires_in" seconds.
    ; This way we'll know when the token expires.
    If CkJsonObject::ckHasMember(jsonToken,"expires_on") = 0
        dtExpire.i = CkDateTime::ckCreate()
        If dtExpire.i = 0
            Debug "Failed to create object."
            ProcedureReturn
        EndIf

        CkDateTime::ckSetFromCurrentSystemTime(dtExpire)
        CkDateTime::ckAddSeconds(dtExpire,CkJsonObject::ckIntOf(jsonToken,"expires_in"))
        CkJsonObject::ckAppendString(jsonToken,"expires_on",CkDateTime::ckGetAsUnixTimeStr(dtExpire,0))
    EndIf

    ; Save the new JSON access token response to a file.
    ; The access + refresh tokens contained in this JSON will be needed for the next refresh.
    sbJson.i = CkStringBuilder::ckCreate()
    If sbJson.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::setCkEmitCompact(jsonToken, 0)
    CkJsonObject::ckEmitSb(jsonToken,sbJson)
    CkStringBuilder::ckWriteFile(sbJson,"qa_data/tokens/hmrc.json","utf-8",0)

    Debug "OAuth2 authorization granted!"
    Debug "New Access Token = " + CkOAuth2::ckAccessToken(oauth2)


    CkJsonObject::ckDispose(jsonToken)
    CkOAuth2::ckDispose(oauth2)
    CkDateTime::ckDispose(dtExpire)
    CkStringBuilder::ckDispose(sbJson)


    ProcedureReturn
EndProcedure