[CmdletBinding()]
param (
    [Parameter(Mandatory = $true)]
    [string]
    $Path,
    [Parameter()]
    [guid]
    $TenantId,
    [Parameter()]
    [switch]
    $UpdateName
)

#region Private helper functions

<#
.SYNOPSIS
    Formats a phone number
.DESCRIPTION
    Formats a phone number into the format (123) 456-7890 Ext. 1234

    Takes a 15-digit E.164 phone number
.PARAMETER PhoneNumber
    The phone number to format
#>
function Format-PhoneNumber {
    [CmdletBinding()]
    param (
        # The phone number to format
        [Parameter(Mandatory=$true,ValueFromPipeline)]
        [string]
        $PhoneNumber
    )

    $Parts = [regex]::Matches($PhoneNumber, '^(\+\d{1,2})?[\s-]?\(?(\d{3})\)?[\s.-]?(\d{3})[\s.-]?(\d{4})(?:\s[E|e]?xt?\.?\s(\d+))?').Groups

    if ($Parts[5].Success) {
        return "($($Parts[2])) $($Parts[3])-$($Parts[4]) Ext. $($Parts[5])"
    } else {
        return "($($Parts[2])) $($Parts[3])-$($Parts[4])"
    }
}

#endregion

# Connnect to Microsoft Graph for the given tenant
if ($null -eq (Get-MgContext)) {
    if ($null -eq $TenantId) {
        Write-Warning "No tenant ID provided. Connecting to Microsoft Graph without tenant context."
        Connect-MgGraph -NoWelcome -Scopes User.ReadWrite.All, Organization.Read.All
    } else {
        Connect-MgGraph -NoWelcome -Scopes User.ReadWrite.All, Organization.Read.All -TenantId $TenantId
    }
} else {
    Write-Verbose "Already connected to Microsoft Graph. Authenticated as $((Get-MgContext).Account) to tenant $((Get-MgContext).TenantId)."
}

# Import the list of users
$Users = Import-Csv -Path $Path

$Results = @()

foreach ($User in $Users) {
    Write-Progress -Activity "Updating user $($User.Email)" -Status "Processing $($Results.Count) of $($Users.Count)" -PercentComplete (($Results.Count / $Users.Count) * 100)
    
    # Try to match up the email address of the user with a Graph user.
    # If it matches, return the UserId for use in later update step.
    try {
        $UserId = (Get-MgUser -Filter "Mail eq '$($User.Email)'").Id
    } catch {
        Write-Warning "User with email $($User.Email) not found in Microsoft Graph. Skipping update for this user. Error: $_"
        Continue
    }

    # Default properties
    $NewProperties = @{}

    if ($UpdateName) {
        if ($null -ne $User.GivenName -and $User.GivenName -ne '') { $NewProperties.GivenName = $User.GivenName } else { Write-Verbose "No given name provided for $($User.Email). Skipping update for this property." }
        if ($null -ne $User.Surname -and $User.Surname -ne '') { $NewProperties.Surname = $User.Surname } else { Write-Verbose "No surname provided for $($User.Email). Skipping update for this property." }
        if ($null -ne $User.DisplayName -and $User.DisplayName -ne '') { $NewProperties.DisplayName = $User.DisplayName } else { Write-Verbose "No display name provided for $($User.Email). Skipping update for this property." }
    }
    
    if ($null -ne $User.JobTitle -and $User.JobTitle -ne '') { $NewProperties.JobTitle = $User.JobTitle } else { Write-Verbose "No job title provided for $($User.Email). Skipping update for this property." }
    if ($null -ne $User.Department -and $User.Department -ne '') { $NewProperties.Department = $User.Department } else { Write-Verbose "No department provided for $($User.Email). Skipping update for this property." }
    if ($null -ne $User.OfficeLocation -and $User.OfficeLocation -ne '') { $NewProperties.OfficeLocation = $User.OfficeLocation } else { Write-Verbose "No office location provided for $($User.Email). Skipping update for this property." }

    # Format phone numbers
    if ($null -ne $User.BusinessPhone -and $User.BusinessPhone -ne '') { $NewProperties.BusinessPhones = @(Format-PhoneNumber -PhoneNumber $User.BusinessPhone) } else { Write-Verbose "No business phone provided for $($User.Email). Skipping update for this property." }
    if ($null -ne $User.MobilePhone -and $User.MobilePhone -ne '') { $NewProperties.MobilePhone = Format-PhoneNumber -PhoneNumber $User.MobilePhone } else { Write-Verbose "No mobile phone provided for $($User.Email). Skipping update for this property." }
    if ($null -ne $User.FaxNumber -and $User.FaxNumber -ne '') { $NewProperties.FaxNumber = Format-PhoneNumber -PhoneNumber $User.FaxNumber } else { Write-Verbose "No fax number provided for $($User.Email). Skipping update for this property." }

    # Update Graph user Entra properties
    Update-MgUser -UserId $UserId @NewProperties

    $NewProperties.Id = $UserId

    $Results += [PsCustomObject]$NewProperties
}

# $Results | sort OfficeLocation,DisplayName | select Id,DisplayName,License,JobTitle,@{Label='BusinessPhone';Expression={$_.BusinessPhones[0]}},MobilePhone,FaxNumber,CompanyName,OfficeLocation | Out-GridView
$Results | Sort-Object OfficeLocation,DisplayName | Select-Object Id,DisplayName,License,JobTitle,@{Label='BusinessPhone';Expression={$_.BusinessPhones[0]}},MobilePhone,FaxNumber,CompanyName,OfficeLocation | Export-Csv -Path results.csv -NoTypeInformation