functions/oAuth/Get-EXRAccessToken.ps1

function Get-EXRAccessToken
{
    [CmdletBinding()]
    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]
        $CacheCredentials
        
    )
    Begin
    {
        Add-Type -AssemblyName System.Web
        $HttpClient = Get-HTTPClient -MailboxName $MailboxName
        $AppSetting = Get-AppSettings
        if ([String]::IsNullOrEmpty($ClientId))
        {
            $ReturnToken = Get-ProfiledToken -MailboxName $MailboxName
            if($ReturnToken -eq $null){
                Write-Error ("No Access Token for " + $MailboxName)
            }
            else{                
                return $ReturnToken
            }
        }
        else{
            if ([String]::IsNullOrEmpty(($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
            Add-Member -InputObject $JsonObject -NotePropertyName mailbox -NotePropertyValue $MailboxName
            if ($Beta.IsPresent)
            {
                Add-Member -InputObject $JsonObject -NotePropertyName Beta -NotePropertyValue $True
            }
            if($CacheCredentials.IsPresent){
                if(!$Script:TokenCache.ContainsKey($ResourceURL)){    
                    $ResourceTokens = @{}        
                    $Script:TokenCache.Add($ResourceURL,$ResourceTokens)
                }
                Add-Member -InputObject $JsonObject -NotePropertyName Cached -NotePropertyValue $true                
                $HostDomain = (New-Object system.net.Mail.MailAddress($MailboxName)).Host.ToLower()
                if(!$Script:TokenCache[$ResourceURL].ContainsKey($HostDomain)){            
                    $Script:TokenCache[$ResourceURL].Add($HostDomain,$JsonObject)
                }
                else{
                    $Script:TokenCache[$ResourceURL][$HostDomain] = $JsonObject
                }
                write-host ("Cached Token for " + $ResourceURL + " " + $HostDomain)
            }
            return $JsonObject
        }
    }
}