VBA Excel: Retrieve/display email using Gmail API on excel - vba

Question

I research regarding retrieving or displaying emails from gmail without using outlook and it led me here on using Gmail API. I'm confused because I don't have idea on how to solve my problem.
Here's the code:
Attribute VB_Name = "Gmail"
' Setup client and authenticator (cached between requests)
Private pGmailClient As WebClient
Private Property Get GmailClient() As WebClient
If pGmailClient Is Nothing Then
' Create client with base url that is appended to all requests
Set pGmailClient = New WebClient
pGmailClient.BaseUrl = "https://www.googleapis.com/gmail/v1/"
' Use the pre-made GoogleAuthenticator found in authenticators/ folder
' - Automatically uses Google's OAuth approach including login screen
' - Get API client id and secret from https://console.developers.google.com/
' - https://github.com/timhall/Excel-REST/wiki/Google-APIs for more info
Dim Auth As New GoogleAuthenticator
Auth.Setup CStr(Credentials.Values("Google")("id")), CStr(Credentials.Values("Google")("secret"))
Auth.AddScope "https://www.googleapis.com/auth/gmail.readonly"
Auth.Login
Set pGmailClient.Authenticator = Auth
End If
Set GmailClient = pGmailClient
End Property
' Load messages for inbox
Function LoadInbox() As Collection
Set LoadInbox = New Collection
' Create inbox request with userId and querystring for inbox label
Dim Request As New WebRequest
Request.Resource = "users/{userId}/messages"
Request.AddUrlSegment "userId", "me"
Request.AddQuerystringParam "q", "label:inbox"
Dim Response As WebResponse
Set Response = GmailClient.Execute(Request)
If Response.StatusCode = WebStatusCode.Ok Then
Dim MessageInfo As Dictionary
Dim Message As Dictionary
For Each MessageInfo In Response.Data("messages")
' Load full messages for each id
Set Message = LoadMessage(MessageInfo("id"))
If Not Message Is Nothing Then
LoadInbox.Add Message
End If
Next MessageInfo
End If
End Function
' Load message details
Function LoadMessage(MessageId As String) As Dictionary
Dim Request As New WebRequest
Request.Resource = "users/{userId}/messages/{messageId}"
Request.AddUrlSegment "userId", "me"
Request.AddUrlSegment "messageId", MessageId
Dim Response As WebResponse
Set Response = GmailClient.Execute(Request)
If Response.StatusCode = WebStatusCode.Ok Then
Set LoadMessage = New Dictionary
' Pull out relevant parts of message (from, to, and subject from headers)
LoadMessage.Add "snippet", Response.Data("snippet")
Dim Header As Dictionary
For Each Header In Response.Data("payload")("headers")
Select Case Header("name")
Case "From"
LoadMessage.Add "from", Header("value")
Case "To"
LoadMessage.Add "to", Header("value")
Case "Subject"
LoadMessage.Add "subject", Header("value")
End Select
Next Header
End If
End Function
Sub Test()
Dim Message As Dictionary
For Each Message In LoadInbox
Debug.Print "From: " & Message("from") & ", Subject: " & Message("subject")
Debug.Print Message("snippet") & vbNewLine
Next Message
End Sub
I'm using the blank file from this GitHub Link that enables this code above. I was stuck on this error:
Still I don't have the idea what's the output of this API because it's my first time using this one. I have my id and secret already from Gmail API i just removed it from the code. I guess it was really hard if I don't have someone I can do brainstorming regarding on this matter.
Hoping someone have encountered this problem or anyone is interested. Thanks.