graphCreateNewTeamsChatForEachUserAndResourceAccount.ps1

# Author: Martin Heusser (@mozzeph)
# Required Scopes: "profile", "openid", "User.Read.All", "Chat.Create"

$AppId = ''
$AppSecret = ''
$TenantName = ''

function Connect-HTTPGraph {
    param (
        [Parameter(Mandatory=$true)][String]$AppId,
        [Parameter(Mandatory=$true)][String]$AppSecret,
        [Parameter(Mandatory=$true)][String]$TenantName
    )
    # Define AppId, secret and scope, your tenant name and endpoint URL
    $AppId = $AppId
    $AppSecret = $AppSecret
    $Scope = "https://graph.microsoft.com/.default"
    $TenantName = $TenantName
    $Url = "https://login.microsoftonline.com/$TenantName/oauth2/v2.0/token"
    # Add System.Web for urlencode
    Add-Type -AssemblyName System.Web
    # Create body
    $Body = @{
        client_id = $AppId
        client_secret = $AppSecret
        scope = $Scope
        grant_type = 'client_credentials'
    }
    # Splat the parameters for Invoke-Restmethod for cleaner code
    $PostSplat = @{
        ContentType = 'application/x-www-form-urlencoded'
        Method = 'POST'
        # Create string by joining bodylist with '&'
        Body = $Body
        Uri = $Url
    }
    # Request the token!
    $Request = Invoke-RestMethod @PostSplat
    # Create header
    $Header = @{
        Authorization = "$($Request.token_type) $($Request.access_token)"
    }

}

. Connect-HTTPGraph -AppId $AppId -AppSecret $AppSecret

# Get all Teams resource accounts
$allResourceAccounts = (Invoke-RestMethod -Method Get -Uri "https://graph.microsoft.com/v1.0/users?`$filter=startsWith(department,'Microsoft Communication Application Instance')" -Headers $Header -ContentType "application/json").value

# Example to get all users licensed for Teams Phone
$allTeamsPhoneUsers = (Invoke-RestMethod -Method Get -Uri "https://graph.microsoft.com/v1.0/users?`$filter=assignedLicenses/any(a:a/skuId eq e43b5b99-8dfb-405f-9987-dc307f34bcbd)" -Headers $Header -ContentType "application/json").value

# Test with only 1 user
#$allTeamsPhoneUsers = $allTeamsPhoneUsers[-1]

foreach ($user in $allTeamsPhoneUsers) {

    $userId = $user.id

    foreach ($resourceAccount in $allResourceAccounts) {

        Write-Host $resourceAccount.DisplayName

        $resourceAccountId = $resourceAccount.id

        $createChat = @"
        {
            "chatType": "oneOnOne",
            "members": [
            {
                "@odata.type": "#microsoft.graph.aadUserConversationMember",
                "roles": ["owner"],
                "[email protected]": "https://graph.microsoft.com/v1.0/users('$userId')"
            },
            {
                "@odata.type": "#microsoft.graph.aadUserConversationMember",
                "roles": ["owner"],
                "[email protected]": "https://graph.microsoft.com/v1.0/users('$resourceAccountId')"
            }
            ]
        }
"@
    
        (Invoke-RestMethod -Method Post -Uri "https://graph.microsoft.com/v1.0/chats" -Headers $Header -ContentType "application/json" -Body $createChat)
    
        #Read-Host

    }

}