(Swift) 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.IntOf("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.StringOf("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.IntOf("expires_in").intValue)
        json.AppendString("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", textData: json.Emit(), charset: "utf-8", includedPreamble: false)

}