<#
Sets Windows language for the current signed-in user only.

Menu:
1 = English (en-US)
2 = Svenska (sv-SE)
3 = Norsk Bokmal (nb-NO)

What it changes:
- Current user's Windows language list
- Current user's UI language override
- Current user's culture/format
- Current user's home location
- Current user's default keyboard/input method
- Current user's language-list opt-out settings

What it does not change:
- It does not install language packs.
- It does not change system locale.
- It does not change welcome screen/system account/new user defaults.

Run this in the target user's own logon session. For example, to apply settings
to eanet\davidw, sign in as eanet\davidw and run this script from that session.
#>

param(
    [string]$Choice
)

$ErrorActionPreference = "Stop"

function Write-Section {
    param(
        [string]$Title
    )

    Write-Host ""
    Write-Host "== $Title =="
}

function Write-Step {
    param(
        [string]$Message
    )

    Write-Host (" - {0}" -f $Message)
}

function Write-WarningStep {
    param(
        [string]$Message
    )

    Write-Host (" ! {0}" -f $Message)
}

function Get-FirstLanguageTag {
    param(
        $LanguageList
    )

    foreach ($language in $LanguageList) {
        return $language.LanguageTag
    }

    return $null
}

function Set-CurrentUserLanguage {
    param(
        [string]$Tag,
        [string]$InputTip,
        [int]$GeoId
    )

    $currentList = Get-WinUserLanguageList
    $newList = New-WinUserLanguageList -Language $Tag

    foreach ($item in $currentList) {
        if ($item.LanguageTag -ne $Tag) {
            $newList += $item
        }
    }

    Set-WinUserLanguageList -LanguageList $newList -Force | Out-Null
    Set-WinUILanguageOverride -Language $Tag
    Set-Culture -CultureInfo $Tag
    Set-WinHomeLocation -GeoId $GeoId
    Set-WinCultureFromLanguageListOptOut -OptOut $False
    Set-WinAcceptLanguageFromLanguageListOptOut -OptOut $False

    if ($InputTip) {
        Set-WinDefaultInputMethodOverride -InputTip $InputTip
    }
}

function Test-LanguageResult {
    param(
        [string]$Tag
    )

    $problems = 0

    Write-Section "Verification before sign out"

    $verifyList = Get-WinUserLanguageList
    $primaryLanguage = Get-FirstLanguageTag -LanguageList $verifyList

    if ($primaryLanguage -eq $Tag) {
        Write-Step "Primary user language is $Tag"
    }
    else {
        Write-WarningStep "Primary user language is $primaryLanguage, expected $Tag"
        $problems = $problems + 1
    }

    $uiOverride = Get-WinUILanguageOverride

    if ($null -ne $uiOverride -and $uiOverride.Name -eq $Tag) {
        Write-Step "User UI language override is $Tag"
    }
    else {
        Write-WarningStep "User UI language override is not $Tag"
        $problems = $problems + 1
    }

    $culture = Get-Culture

    if ($culture.Name -eq $Tag) {
        Write-Step "User culture is $Tag"
    }
    else {
        Write-WarningStep "User culture is $($culture.Name), expected $Tag"
        $problems = $problems + 1
    }

    return $problems
}

if (-not $Choice) {
    Write-Host ""
    Write-Host "Choose language:"
    Write-Host "1 = English"
    Write-Host "2 = Svenska"
    Write-Host "3 = Norsk Bokmal"
    Write-Host ""

    $Choice = Read-Host "Enter 1, 2, or 3"
}

switch ($Choice) {
    '1' {
        $LanguageTag  = 'en-US'
        $LanguageName = 'English (United States)'
        $InputTip     = '0409:00000409'
        $GeoId        = 244
    }
    '2' {
        $LanguageTag  = 'sv-SE'
        $LanguageName = 'Svenska (Sverige)'
        $InputTip     = '041D:0000041D'
        $GeoId        = 221
    }
    '3' {
        $LanguageTag  = 'nb-NO'
        $LanguageName = 'Norsk Bokmal (Norge)'
        $InputTip     = '0414:00000414'
        $GeoId        = 177
    }
    default {
        Write-Host "Invalid choice: $Choice"
        Write-Host "Use 1, 2, or 3."
        exit 1
    }
}

Write-Host ""
Write-Host "Selected language: $LanguageName [$LanguageTag]"

Write-Section "Execution context"
$currentIdentity = whoami.exe
Write-Step "User: $currentIdentity"
Write-Step "PowerShell language mode: $($ExecutionContext.SessionState.LanguageMode)"

if ($currentIdentity -eq "nt authority\system") {
    Write-WarningStep "Running as SYSTEM. This script must run as the target user, not SYSTEM."
    exit 1
}

Write-Section "Configuring current user"
Set-CurrentUserLanguage -Tag $LanguageTag -InputTip $InputTip -GeoId $GeoId
Write-Step "User language list, UI override, culture, home location, and default keyboard set"

$problemCount = Test-LanguageResult -Tag $LanguageTag

Write-Host ""

if ($problemCount -gt 0) {
    Write-Host "Completed with $problemCount verification warning(s)."
    Write-Host "If these warnings show the old language immediately after running, a policy or missing language pack may be preventing the change."
    exit 2
}

Write-Host "Done."
Write-Host "Language set to $LanguageName [$LanguageTag] for the current user."
Write-Host "Sign out and back in to fully apply the Windows UI language."