An interactive PowerShell function to select items from a collection based on the first letter

Select-Item.ps1

function SelectItem {
<#
.SYNOPSIS
Selects an item from a provided list based on keyboard input.

.DESCRIPTION
The SelectItem function allows the user to select an item from a given list of strings by typing the first letter of the 
item. The function iterates through the items that start with the given letter, allowing the user to press the same letter 
repeatedly to cycle through the options. Selection is confirmed with the Enter key.

.PARAMETER Item
An array of strings from which the user can select. This parameter is mandatory and cannot be null or empty.

.EXAMPLE
$items = 'Red', 'Orange', 'Yellow', 'Green', 'Blue'
SelectItem -Item $items

This example will prompt the user to select a color by typing the first letter of the color name. Pressing the Enter key 
confirms the selection.

.NOTES
This function uses the host's UI RawUI.ReadKey method to capture key presses without echoing them to the console. It's 
designed for interactive terminal sessions and may not work as expected in non-interactive environments or IDEs that do 
not support RawUI functionality.

#>
    param(
        [Parameter(Mandatory)] # Indicates that this parameter must be provided for the function to execute
        [ValidateNotNullOrEmpty()] # Ensures the parameter value is not null or an empty string
        [string[]]$Item # Array of strings representing the items to select from
    )
    
    # Initialize variables for navigating and selecting items
    $currentIndex = -1 # Index for the current item selection
    $lastKey = $null # Stores the last key pressed by the user
    $currentMatch = $null # Stores the currently matched item based on user input
    $currentDisplay = "" # Variable to hold the display value of the current item selection

    do {
        # Capture the key press from the user without echoing it to the terminal
        $keyPress = $host.UI.RawUI.ReadKey('NoEcho,IncludeKeyDown')
        # Convert the virtual key code to a character and make it uppercase
        $keyChar = [char]$keyPress.VirtualKeyCode
        $keyChar = $keyChar.ToString().ToUpper()

        if ($keyPress.VirtualKeyCode -eq 13) {
            # If Enter key is pressed, exit the loop
            break
        }

        if ($lastKey -ne $keyChar) {
            # If a different key is pressed, reset the index to 0 and update the last key
            $currentIndex = 0
            $lastKey = $keyChar
        } else {
            # If the same key is pressed consecutively, increment the index to navigate through matches
            $currentIndex++
        }
        # Filter the items based on the starting letter matching the pressed key
        [array]$itemMatches = $Item | Where-Object { $_ -match "^$lastKey" }
        if ($itemMatches) {

            if ($currentIndex -ge $itemMatches.Count) {
                $currentIndex = 0 # Reset the index if it exceeds the number of matches
            }

            if ($itemMatches.Count -gt 0) {
                $currentMatch = $itemMatches[$currentIndex] # Update the current match based on the index
            } else {
                $currentMatch = $null
            }

            # Clear the previous display output
            $clearLength = $currentDisplay.Length
            $clearMsg = " " * $clearLength
            Write-Host "`r$clearMsg" -NoNewline # Use spaces to clear the display

            if ($null -ne $currentMatch) {
                $currentDisplay = $currentMatch
                Write-Host "`r$currentDisplay" -NoNewline # Display the current match
            } else {
                $currentDisplay = "No match found for `"$lastKey`"" # Display no match message if no matches are found
                Write-Host "`r$currentDisplay" -NoNewline
            }
        }

    } while ($keyPress.VirtualKeyCode -ne 13) # Continue looping until the Enter key is pressed

    # Output the selected item or a message indicating no selection was made
    if ($null -ne $currentMatch) {
        $currentMatch
    } else {
        Write-Host "`nNo selection made."
    }
}

## Example usage

$colors = @(
    'Red',
    'Orange',
    'Yellow',
    'Green',
    'Blue',
    'Indigo',
    'Violet',
    'Black',
    'White',
    'Grey',
    'Cyan',
    'Magenta',
    'Maroon',
    'Navy',
    'Olive',
    'Purple',
    'Teal',
    'Lime',
    'Silver',
    'Gold',
    'Beige',
    'Coral',
    'Ivory',
    'Khaki',
    'Lavender',
    'Salmon',
    'Tan',
    'Turquoise',
    'DarkBlue',
    'DeepPink',
    'LightGreen',
    'MediumBlue',
    'Orchid',
    'PaleGreen',
    'RoyalBlue',
    'SlateGray',
    'SpringGreen',
    'SteelBlue',
    'Tomato',
    'YellowGreen'
)

Write-Host "Pick a color by pressing the first letter."
SelectItem -Item $colors