(Swift 3,4,5...) Refresh a Dynamics CRM OAuth2 Access Token

Demonstrates how to refresh an expiring Dynamics CRM access token using the refresh token. endpoint.

(If a REST API call fails with a 401 unauthorized error, an application can auto-recover by refreshing the access token, and then re-send the request using the new token.)

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // We previously obtained an access token and saved the JSON to a file using this example:
    // Get Dynamics CRM OAuth2 Access Token

    // This example will examine the JSON and expiration date, and if near expiration will
    // refresh the access token.

    let json = CkoJsonObject()!
    var success: Bool = json.loadFile("qa_data/tokens/dynamicsCrm.json")
    if success != true {
        return
    }

    // The contents of the JSON look 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": "..."
    // }

    // The "expires_on" value is a Unix time.
    let dtExpire = CkoDateTime()!
    dtExpire.setFromUnixTime(false, t: json.int(of: "expires_on").intValue)

    // If this date/time expires within 10 minutes of the current system time, refresh the token.

    // OK, we need to refresh the access token by sending a POST...
    // 

    let req = CkoHttpRequest()!
    req.addParam("grant_type", value: "refresh_token")
    req.addParam("redirect_uri", value: "http://localhost:3017/")
    req.addParam("client_id", value: "DYNAMICS-CRM-CLIENT-ID")
    req.addParam("client_secret", value: "DYNAMICS-CRM-SECRET-KEY")
    req.addParam("refresh_token", value: json.string(of: "refresh_token"))
    req.addParam("resource", value: "https://mydynamicsdomain.api.crm.dynamics.com")

    let http = CkoHttp()!

    var resp: CkoHttpResponse? = http.postUrlEncoded("https://login.microsoftonline.com/DYNAMICS-ENDPOINT-GUID/oauth2/token", req: req)
    if http.lastMethodSuccess != true {
        print("\(http.lastErrorText!)")
        return
    }

    // Load the JSON response.
    json.load(resp!.bodyStr)
    json.emitCompact = false

    // Show the JSON response.
    print("\(json.emit()!)")

    print("Response status code: \(resp!.statusCode.intValue)")

    // If the response status code is not 200, then it's an error.
    if resp!.statusCode.intValue != 200 {
        return
    }

    resp = nil

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

    // Save the refreshed access token JSON to a file for future requests.
    let fac = CkoFileAccess()!
    fac.writeEntireTextFile("qa_data/tokens/dynamicsCrm.json", fileData: json.emit(), charset: "utf-8", includePreamble: false)

}