(Swift 2) Refresh a Frame.io OAuth2 Access Token

Refreshes a Frame.io OAuth2 access token. When an access token expires, HTTPS requests will receive a 401 status response indicating failure. When that happens, your application can run this code to refresh the access token, and then retry the request using the new access token. Refreshing an access token does not need user interaction (i.e. does not need to display a browser to have the user interactive authorize access).

Note: This example requires Chilkat v9.5.0.84 or greater.

For more information, see https://docs.frame.io/docs/refresh-tokens

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

    // IMPORTANT: This example requires Chilkat v9.5.0.84 or greater because of an internal modification required to support frame.io
    // IMPORTANT: This example requires Chilkat v9.5.0.84 or greater because of an internal modification required to support frame.io
    // IMPORTANT: This example requires Chilkat v9.5.0.84 or greater because of an internal modification required to support frame.io

    // It is assumed we previously obtained an OAuth2 access token.
    // This example loads the JSON access token file 
    // saved by this example: Get Frame.io OAuth2 Access Token

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

    // The access token JSON looks like this:

    // {
    //   "access_token": "kwenK_QQnQipMZGtlGreCwrjUxMBr4OX-XAEVA0Q3Rg.yFqYY_c-Mw_k59X1e9rTYR5m-EWf9ivWc1kqmsxR2v4",
    //   "expires_in": 3600,
    //   "refresh_token": "ZI7XDR0lWoKAXYxPs8BW7bU2IJg3za0zlimMfvTEhUg.pffnx7xye30Eps6OZEYcdzrINFSM3fM5zi78ln7QQ3o",
    //   "scope": "offline asset.create asset.read asset.update asset.delete",
    //   "token_type": "bearer"
    // }

    let oauth2 = CkoOAuth2()

    oauth2.TokenEndpoint = "https://applications.frame.io/oauth2/token"

    // Replace these with actual values.
    oauth2.ClientId = "CLIENT_ID"
    oauth2.ClientSecret = "CLIENT_SECRET"

    // Frame.io sends the client ID and secret using HTTP basic authentication.
    oauth2.UseBasicAuth = true

    // Get the "refresh_token"
    oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

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

    print("New access token: \(oauth2.AccessToken)")
    print("New refresh token: \(oauth2.RefreshToken)")

    // Update the JSON with the new tokens.
    jsonToken.UpdateString("access_token", value: oauth2.AccessToken)
    jsonToken.UpdateString("refresh_token", value: oauth2.RefreshToken)

    // Save the new JSON access token response to a file.
    let sbJson = CkoStringBuilder()
    jsonToken.EmitCompact = false
    jsonToken.EmitSb(sbJson)
    sbJson.WriteFile("qa_data/tokens/frame_io.json", charset: "utf-8", emitBom: false)

    print("OAuth2 token refreshed!")
    print("New Access Token = \(oauth2.AccessToken)")

}