#Requires -Modules ActiveDirectory

<#
.SYNOPSIS
    Assigns email addresses to student users in a specified OU.

.DESCRIPTION
    Scans all users in the target OU and sets their email address to
    [SamAccountName]@[Domain]. Existing email addresses are skipped
    unless -Force is used.

.PARAMETER OU
    The distinguished name of the OU to search.

.PARAMETER Domain
    The email domain to use (e.g. niddrieautisticschool.vic.edu.au).

.PARAMETER Force
    Overwrite existing email addresses.

.PARAMETER WhatIf
    Preview changes without applying them.

.EXAMPLE
    .\Set-StudentEmail.ps1
    Runs with the default OU and domain.

.EXAMPLE
    .\Set-StudentEmail.ps1 -OU "OU=Students,OU=Users,DC=contoso,DC=com" -Domain "contoso.com"
    Runs against a custom OU and domain.

.EXAMPLE
    .\Set-StudentEmail.ps1 -WhatIf
    Preview what changes would be made without applying them.
#>

[CmdletBinding(SupportsShouldProcess)]
param (
    [string]$OU = "OU=Student,OU=Users,OU=5362-NiddrieAutistic,DC=curric,DC=niddrieautistic,DC=wan",
    [string]$Domain = "niddrieautisticschool.vic.edu.au",
    [switch]$Force
)

# Import the Active Directory module
Import-Module ActiveDirectory -ErrorAction Stop

# Retrieve all users in the specified OU
$users = Get-ADUser -Filter * -SearchBase $OU -Properties EmailAddress

if (-not $users) {
    Write-Warning "No users found in OU: $OU"
    exit
}

Write-Host "Found $($users.Count) user(s) in '$OU'" -ForegroundColor Cyan
Write-Host ""

$updated  = 0
$skipped  = 0
$errors   = 0

foreach ($user in $users) {
    $username = $user.SamAccountName

    # Build the email — force lowercase
    $email = "$($username.Trim())@$Domain".ToLower()

    # Check if email is already set and matches (skip unless -Force)
    if ($user.EmailAddress -eq $email -and -not $Force) {
        Write-Host "OK:   $username already has '$email'" -ForegroundColor DarkGray
        $skipped++
        continue
    }

    if ($user.EmailAddress -and -not $Force) {
        Write-Warning "SKIP: '$username' already has email '$($user.EmailAddress)'. Use -Force to overwrite."
        $skipped++
        continue
    }

    # Apply the email address
    if ($PSCmdlet.ShouldProcess($username, "Set email to '$email'")) {
        try {
            Set-ADUser -Identity $user.DistinguishedName -EmailAddress $email
            Write-Host "SET:  $username -> $email" -ForegroundColor Green
            $updated++
        }
        catch {
            Write-Error "FAIL: Could not update '$username': $_"
            $errors++
        }
    }
}

Write-Host ""
Write-Host "--- Summary ---" -ForegroundColor Cyan
Write-Host "Updated: $updated"
Write-Host "Skipped: $skipped"
Write-Host "Errors:  $errors"