<# 
=============================================================================================
# It is recommended to test the script on a local machine to verify its functionality and effects.
# ManageEngine Endpoint Central will not be responsible for any damage or data loss caused by the script's execution.

# Description     : Script to rename multiple Windows computers using CSV mappings.
# Dependency File : ComputerRename.csv
# Log File        : C:\Program Files (x86)\ManageEngine\UEMS_Agent\logs\RenameComputerLogger.log
# Type            : Computer
# Execution Requirements:
    * The end user must create the 'ComputerRename.csv' file and attach it as a dependency file during deployment.
    * The script must be executed with elevated privileges.
    * Initially, test the script using the SYSTEM account.
    * If the script fails due to insufficient permissions under SYSTEM, execute it using "RUN AS" Option with Common admin account

# CSV File Creation – Computer Rename Configuration
    1. Create a CSV file named ComputerRename.csv.
    2. The CSV file must contain the following two columns:
           * CurrentComputerName
           * NewComputerName
    3. Use the sample data below as a reference and replace the sample computer names with the appropriate names for your environment.
            CurrentComputerName,NewComputerName
            DESKTOP01,KB-PC16
            DESKTOP02,KB-PC06
            DESKTOP03,KB-PC1
# Important:
    * "CurrentComputerName" must contain the computer's existing hostname.
    * "NewComputerName" must contain the expected new hostname to be assigned to the computer.
    * Ensure that the existing computer name matches the device's current hostname.
    * Ensure that each new computer name is valid and unique within the environment.
    * Save the file in CSV format with the exact filename "ComputerRename.csv" & upload as dependency file

# Troubleshooting:
    * Check RenameComputerLogger.log at C:\Program Files (x86)\ManageEngine\UEMS_Agent\logs\RenameComputerLogger.log to identify the reason for the rename failure.
    * If the computer name was changed but is not reflected, restart the affected machine once. There is no need to restart all connected devices. 
==============================================================================================
#>

$ErrorActionPreference = "Stop"

$LogFolder = "C:\Program Files (x86)\ManageEngine\UEMS_Agent\logs"
$LogFile   = Join-Path $LogFolder "RenameComputerLogger.log"
$CSVFile   = "ComputerRename.csv"

# ------------------------------------------------------------
# Initialize logging directory
# ------------------------------------------------------------
try {
    if (-not (Test-Path -LiteralPath $LogFolder)) {
        New-Item -Path $LogFolder -ItemType Directory -Force |
            Out-Null
    }
}
catch {
    Write-Warning "Unable to initialize logging directory: $($_.Exception.Message)"
    return
}

# ------------------------------------------------------------
# Logging function: append timestamped entries
# ------------------------------------------------------------
function Write-Log {
    param (
        [Parameter(Mandatory = $true)]
        [string]$Message
    )

    $Timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss.fff"
    $LogMessage = "[$Timestamp] $Message"

    try {
        Add-Content -LiteralPath $LogFile `
            -Value $LogMessage `
            -Encoding UTF8
    }
    catch {
        Write-Warning "Unable to write log entry: $($_.Exception.Message)"
    }
}

# ------------------------------------------------------------
# Main execution
# ------------------------------------------------------------
try {
    Write-Log "=================================================="
    Write-Log "Computer rename script execution started."
    
    # Log execution details
    Write-Log "Execution account: $([System.Security.Principal.WindowsIdentity]::GetCurrent().Name)"
    Write-Log "Current computer name: $env:COMPUTERNAME"
    Write-Log "Current working directory: $(Get-Location)"
    Write-Log "PowerShell script directory: $PSScriptRoot"
    Write-Log "PowerShell script path: $PSCommandPath"
    Write-Log "CSV file path: $CSVFile"
    Write-Log "Log file path: $LogFile"

    # --------------------------------------------------------
    # Validate administrator privileges
    # --------------------------------------------------------
    Write-Log "Checking administrator privileges."

    $Identity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
    $Principal = New-Object System.Security.Principal.WindowsPrincipal($Identity)

    $IsAdmin = $Principal.IsInRole(
        [System.Security.Principal.WindowsBuiltInRole]::Administrator
    )

    if (-not $IsAdmin) {
        Write-Log "ERROR: Administrator privileges are required."
        Write-Log "Please rerun the script using Run as administrator."
        Write-Warning "Please run this script as Administrator."
        return
    }

    Write-Log "Administrator privileges verified successfully."

    # --------------------------------------------------------
    # Validate CSV file
    # --------------------------------------------------------
    Write-Log "Checking CSV file availability."

    if (-not (Test-Path -LiteralPath $CSVFile -PathType Leaf)) {
        Write-Log "ERROR: CSV file not found: $CSVFile"
        Write-Warning "CSV file not found: $CSVFile"
        return
    }

    Write-Log "CSV file found successfully."
    Write-Log "Importing CSV computer mappings."

    $ComputerMappings = @(
        Import-Csv -LiteralPath $CSVFile -ErrorAction Stop
    )

    Write-Log "CSV records loaded: $($ComputerMappings.Count)"

    if ($ComputerMappings.Count -eq 0) {
        Write-Log "ERROR: CSV contains no computer mappings."
        return
    }

    # --------------------------------------------------------
    # Validate required CSV columns
    # --------------------------------------------------------
    $RequiredColumns = @(
        "CurrentComputerName",
        "NewComputerName"
    )

    $CSVColumns = @($ComputerMappings[0].PSObject.Properties.Name)

    foreach ($Column in $RequiredColumns) {
        if ($Column -notin $CSVColumns) {
            Write-Log "ERROR: Required CSV column missing: $Column"
            return
        }
    }

    Write-Log "CSV column validation successful."

    # --------------------------------------------------------
    # Match current computer name
    # --------------------------------------------------------
    $CurrentName = $env:COMPUTERNAME

    Write-Log "Searching CSV for current computer: $CurrentName"

    $MatchingRecords = @(
        $ComputerMappings | Where-Object {
            ([string]$_.CurrentComputerName).Trim() -ieq $CurrentName
        }
    )

    if ($MatchingRecords.Count -eq 0) {
        Write-Log "No mapping found for computer: $CurrentName"
        Write-Log "Rename operation skipped."
        return
    }

    if ($MatchingRecords.Count -gt 1) {
        Write-Log "ERROR: Multiple mappings found for: $CurrentName"
        Write-Log "Rename operation skipped to avoid ambiguity."
        return
    }

    $NewComputerName = ([string]$MatchingRecords[0].NewComputerName).Trim()

    Write-Log "Matching CSV record found."
    Write-Log "Existing computer name: $CurrentName"
    Write-Log "Requested computer name: $NewComputerName"

    # --------------------------------------------------------
    # Validate requested computer name
    # --------------------------------------------------------
    if ([string]::IsNullOrWhiteSpace($NewComputerName)) {
        Write-Log "ERROR: Requested computer name is empty."
        return
    }

    if ($NewComputerName.Length -gt 63 -or
        $NewComputerName -notmatch '^[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?$') {

        Write-Log "ERROR: Invalid computer name: $NewComputerName"
        return
    }

    Write-Log "Requested computer name validation successful."

    # --------------------------------------------------------
    # Compare existing and requested names
    # --------------------------------------------------------
    if ($CurrentName -ieq $NewComputerName) {
        Write-Log "Computer already has the requested name."
        Write-Log "No rename operation is required."
        return
    }

    Write-Log "Computer name mismatch detected."
    Write-Log "Starting Rename-Computer operation."

    # --------------------------------------------------------
    # Rename computer
    # --------------------------------------------------------
    Rename-Computer -NewName $NewComputerName -Force -ErrorAction Stop

    Write-Log "Rename-Computer command completed successfully."
    Write-Log "Previous computer name: $CurrentName"
    Write-Log "Requested new computer name: $NewComputerName"
    Write-Log "A restart may be required for the new name to take effect."
    Write-Log "No automatic restart was initiated."
    Write-Log "Computer rename script execution completed successfully."
}
catch {
    Write-Log "ERROR: $($_.Exception.Message)"
    Write-Log "Exception type: $($_.Exception.GetType().FullName)"
    Write-Log "Computer rename script execution failed."
    Write-Warning "Computer rename failed. Check RenameComputerLogger.log."
}