(Swift 3,4,5...) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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.

    let jsonToken = CkoJsonObject()!
    var success: Bool = jsonToken.loadFile("qa_data/tokens/hmrc.json")
    if success != true {
        print("Failed to load hmrc.json")
        return
    }

    // 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": "..."
    // }

    let oauth2 = CkoOAuth2()!

    oauth2.tokenEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/token"

    // Replace these with actual values.
    oauth2.clientId = "HMRC-CLIENT-ID"
    oauth2.clientSecret = "HMRC-CLIENT-SECRET"

    // Get the "refresh_token"
    oauth2.refreshToken = jsonToken.string(of: "refresh_token")

    // Send the HTTP POST to refresh the access token..
    success = oauth2.refreshAccessToken()
    if success != true {
        print("\(oauth2.lastErrorText!)")
        return
    }

    // Load the access token response into the json object 
    jsonToken.load(oauth2.accessTokenResponse)

    // 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 jsonToken.hasMember("expires_on") == false {
        let dtExpire = CkoDateTime()!
        dtExpire.setFromCurrentSystemTime()
        dtExpire.addSeconds(jsonToken.int(of: "expires_in").intValue)
        jsonToken.append("expires_on", value: dtExpire.getAsUnixTimeStr(false))
    }

    // 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.
    let sbJson = CkoStringBuilder()!
    jsonToken.emitCompact = false
    jsonToken.emitSb(sbJson)
    sbJson.writeFile("qa_data/tokens/hmrc.json", charset: "utf-8", emitBom: false)

    print("OAuth2 authorization granted!")
    print("New Access Token = \(oauth2.accessToken!)")

}