functions/other/Get-AccessToken.ps1

function Get-AccessToken
{
    param (
        [Parameter(Position = 0, Mandatory = $true)]
        [string]
        $MailboxName,
        
        [Parameter(Position = 1, Mandatory = $false)]
        [string]
        $ClientId,
        
        [Parameter(Position = 2, Mandatory = $false)]
        [string]
        $redirectUrl,
        
        [Parameter(Position = 3, Mandatory = $false)]
        [string]
        $ClientSecret,
        
        [Parameter(Position = 4, Mandatory = $false)]
        [string]
        $ResourceURL,
        
        [Parameter(Position = 5, Mandatory = $false)]
        [switch]
        $Beta,
        
        [Parameter(Position = 6, Mandatory = $false)]
        [String]
        $Prompt,

        [Parameter(Position = 7, Mandatory = $false)]
        [switch]
        $SaveToPrivateData
        
    )
    Begin
    {
        Add-Type -AssemblyName System.Web
        $HttpClient = Get-HTTPClient($MailboxName)
        $AppSetting = Get-AppSettings
        if ([String]::IsNullOrEmpty($ClientId))
        {
            $ClientId = "1950a258-227b-4e31-a9cf-717495945fc2"
        }
        if ([String]::IsNullOrEmpty(($ClientSecret)))
        {
            $ClientSecret = $AppSetting.ClientSecret
        }
        if ([String]::IsNullOrEmpty($redirectUrl))
        {
            $redirectUrl = [System.Web.HttpUtility]::UrlEncode("urn:ietf:wg:oauth:2.0:oob")
        }
        else
        {
            $redirectUrl = [System.Web.HttpUtility]::UrlEncode($redirectUrl)
        }
        if ([String]::IsNullOrEmpty($ResourceURL))
        {
            $ResourceURL = $AppSetting.ResourceURL
        }
        if ([String]::IsNullOrEmpty($Prompt))
        {
            $Prompt = "refresh_session"
        }
        
        $Phase1auth = Show-OAuthWindow -Url "https://login.microsoftonline.com/common/oauth2/authorize?resource=https%3A%2F%2F$ResourceURL&client_id=$ClientId&response_type=code&redirect_uri=$redirectUrl&prompt=$Prompt"
        $code = $Phase1auth["code"]
        $AuthorizationPostRequest = "resource=https%3A%2F%2F$ResourceURL&client_id=$ClientId&grant_type=authorization_code&code=$code&redirect_uri=$redirectUrl"
        if (![String]::IsNullOrEmpty($ClientSecret))
        {
            $AuthorizationPostRequest = "resource=https%3A%2F%2F$ResourceURL&client_id=$ClientId&client_secret=$ClientSecret&grant_type=authorization_code&code=$code&redirect_uri=$redirectUrl"
        }
        $content = New-Object System.Net.Http.StringContent($AuthorizationPostRequest, [System.Text.Encoding]::UTF8, "application/x-www-form-urlencoded")
        $ClientReesult = $HttpClient.PostAsync([Uri]("https://login.windows.net/common/oauth2/token"), $content)
        $JsonObject = ConvertFrom-Json -InputObject $ClientReesult.Result.Content.ReadAsStringAsync().Result
        if ([bool]($JsonObject.PSobject.Properties.name -match "refresh_token"))
        {
            $JsonObject.refresh_token = (Get-ProtectedToken -PlainToken $JsonObject.refresh_token)
        }
        if ([bool]($JsonObject.PSobject.Properties.name -match "access_token"))
        {
            $JsonObject.access_token = (Get-ProtectedToken -PlainToken $JsonObject.access_token)
        }
        if ([bool]($JsonObject.PSobject.Properties.name -match "id_token"))
        {
            $JsonObject.id_token = (Get-ProtectedToken -PlainToken $JsonObject.id_token)
        }
        Add-Member -InputObject $JsonObject -NotePropertyName clientid -NotePropertyValue $ClientId
        Add-Member -InputObject $JsonObject -NotePropertyName redirectUrl -NotePropertyValue $redirectUrl
        if ($Beta.IsPresent)
        {
            Add-Member -InputObject $JsonObject -NotePropertyName Beta -NotePropertyValue True
        }
        if($SaveToPrivateData.IsPresent){
            $HostDomain = (New-Object system.net.Mail.MailAddress($MailboxName)).Host.ToLower()
            if(!$MyInvocation.MyCommand.Module.PrivateData['EXRTokens'].ContainsKey($HostDomain)){            
                $MyInvocation.MyCommand.Module.PrivateData['EXRTokens'].Add($HostDomain,$JsonObject)
            }
        }
        return $JsonObject
    }
}