<#
.SYNOPSIS
    Updates Entra ID users based on all available columns in a CSV file.

.DESCRIPTION
    Dynamically maps CSV headers to Microsoft Graph User properties. 
    Compares CSV values to live data and updates only when a difference is found.

.PARAMETER CsvPath
    The full path to the source CSV file.

.EXAMPLE
    Update-EntraUsersDynamic -CsvPath ".\Exports\UserUpdate_20260226.csv"
#>
function Update-EntraUsersDynamic {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [ValidateScript({ Test-Path $_ })]
        [string]$CsvPath
    )

    process {
        Set-StrictMode -Version Latest

        # 1. Setup Logging
        $LogPath = Join-Path -Path $PSScriptRoot -ChildPath "Logs"
        if (-not (Test-Path $LogPath)) { New-Item -ItemType Directory -Force | Out-Null }
        
        $Timestamp = Get-Date -Format "yyyyMMdd-HHmm"
        $LogFile = Join-Path -Path $LogPath -ChildPath "DynamicUpdate_$Timestamp.log"

        try {
            # 2. Load Data and Headers
            $UserData = Import-Csv -Path $CsvPath
            $Columns = $UserData[0].PSObject.Properties.Name
            
            # Attributes we should NOT try to update
            $ExcludedAttributes = @('UserPrincipalName', 'Id', 'DeletedDateTime', 'CreatedDateTime')

            if (-not (Get-MgContext)) { throw "Not connected to Microsoft Graph. Run Connect-MgGraph." }

            foreach ($Row in $UserData) {
                $UPN = $Row.UserPrincipalName
                if ([string]::IsNullOrWhiteSpace($UPN)) { continue }

                try {
                    # 3. Fetch current user with all properties defined in CSV headers
                    Write-Verbose "Processing $UPN..."
                    $CurrentTarget = Get-MgUser -UserId $UPN -Property $Columns -ErrorAction Stop
                    
                    $UpdateHash = @{}

                    foreach ($Col in $Columns) {
                        # Skip excluded columns and empty CSV cells
                        if ($Col -in $ExcludedAttributes -or [string]::IsNullOrWhiteSpace($Row.$Col)) {
                            continue
                        }

                        # 4. Compare CSV value to Current Entra ID value
                        $CsvValue = $Row.$Col
                        $CurrentValue = $CurrentTarget.$Col

                        if ($CsvValue -ne $CurrentValue) {
                            $UpdateHash[$Col] = $CsvValue
                        }
                    }

                    # 5. Execute Update if changes exist
                    if ($UpdateHash.Count -gt 0) {
                        Update-MgUser -UserId $UPN @UpdateHash -ErrorAction Stop
                        Write-Output "SUCCESS: Updated $UPN ($($UpdateHash.Keys -join ', '))"
                        "$Timestamp,$UPN,Updated,$($UpdateHash.Keys -join ';')" | Out-File $LogFile -Append
                    }
                    else {
                        Write-Verbose "SKIP: No changes for $UPN"
                        "$Timestamp,$UPN,NoChange,Matched" | Out-File $LogFile -Append
                    }
                }
                catch {
                    Write-Warning "ERROR: Could not update $UPN - $($_.Exception.Message)"
                    "$Timestamp,$UPN,Error,$($_.Exception.Message)" | Out-File $LogFile -Append
                }
            }
        }
        catch {
            Write-Error "Fatal Script Error: $($_.Exception.Message)"
        }
    }
}