# MTG Arena Account Switcher by /u/rentar
# See https://www.reddit.com/r/MagicArena/comments/1m5vnz5/i_built_a_little_tool_to_switch_between_arena/
param(
    [Parameter(Mandatory=$false)]
    [String]$Account
)

$ErrorActionPreference="Stop"

$SteamExe="${Env:Programfiles(x86)}\Steam\steam.exe"

$PathMtga="HKCU:\Software\Wizards Of The Coast\MTGA"
$PathMtgaAccounts="HKCU:\Software\Wizards Of The Coast\MTGA-Accounts"

# I previously thought the _h123456789 part of the keys was somehow dynamic, but it seems those are just Unity PlayerPrefs, which means they are static.
# This function was used before but seem unnecessary now.
#function Get-RefreshTokenName {
#   (reg query "HKCU\Software\Wizards Of The Coast\MTGA" | Where-Object { $_ -match "WAS-RefreshToken"}).Trim().Split(" ")[0]
#}

$PropertyWASRefreshToken = "WAS-RefreshTokenE_h2698947118"
$PropertyWASRememberMe = "WAS-RememberMe_h1678977314"
$PropertyLastLoginString = "LastLoginString_h2517025721"

function ConvertFrom-Base64 {
    param([byte[]] $bytes)
    ConvertFrom-Base64String([System.Text.Encoding]::ASCII.GetString($bytes))
}

function ConvertFrom-Base64String {
    param([string] $string)
    # Base64 strings seem to sometimes be 0-terminated and sometimes have 0x1D at the end, just remove those.
    $string = $string.TrimEnd("`u{0}`u{1d}".ToCharArray())
    while ($string.Length % 4 -ne 0) {
        $string += "="
    }
    $decoded = [System.Convert]::FromBase64String($string)
    [System.Text.Encoding]::UTF8.GetString($decoded)
}

function Get-RefreshToken {
    Get-ItemPropertyValue -Path $PathMtga -Name $PropertyWASRefreshToken
}

function Get-BackupValue {
    param(
        [string] $account,
        [string] $property)
    try {
        Get-ItemPropertyValue -Path "$PathMtgaAccounts/$account" -Name $property
    } catch {
        # Get-ItemPropertyValue throws an unchangable exception when the property doesn't exist.
        # I'm not alone in thinking this is silly https://github.com/PowerShell/PowerShell/issues/5906
    }
}

function ConvertFrom-JWT {
    param([byte[]] $refreshToken)
    $rtDecoded = ConvertFrom-Base64($refreshToken)
    $rtParts = $rtDecoded.Split('.')
    # Refresh Token seems to be a JWT. The first part is the header, the second the payload, the third the signature.
    # Since we don't verify anthing, we only care about the payload.
    $payload = ConvertFrom-Base64String($rtParts[1])
    $payload | ConvertFrom-Json
}

function Backup-CurrentRefreshToken {
    $refreshToken = Get-RefreshToken
    $payload = ConvertFrom-JWT($refreshToken)
    $account = $payload.sub
    $refreshTokenBackup = Get-BackupValue $account $PropertyWASRefreshToken
    if (-not $refreshTokenBackup) {
        Write-Output "Account ${account}: not seen before, backing up."
        $null = New-Item -Path $PathMtgaAccounts -Name $account -ErrorAction Ignore
        Copy-ItemProperty -Path $PathMtga -Destination "$PathMtgaAccounts/$account" -Name $PropertyLastLoginString
        Copy-ItemProperty -Path $PathMtga -Destination "$PathMtgaAccounts/$account" -Name $PropertyWASRefreshToken
    } else {
        $payloadBackup = ConvertFrom-JWT($refreshTokenBackup)
        if ($payloadBackup.exp -lt $payload.exp) {
            Write-Output "Account ${account}: New refresh token found, backing up ($($payloadBackup.exp) < $($payload.exp))."
            Copy-ItemProperty -Path $PathMtga -Destination "$PathMtgaAccounts/$account" -Name $PropertyWASRefreshToken
        }
    }
}

function Get-AccountDetails {
    param([string]$account)

    $refreshToken = Get-BackupValue $account $PropertyWASRefreshToken
    $lastLoginString = [System.Text.Encoding]::UTF8.GetString((Get-backupValue $account $PropertyLastLoginString)).Trim("`u{0}".ToCharArray())
    $payload = ConvertFrom-JWT $refreshToken

    [pscustomobject]@{ ID=$account; Email=$lastLoginString; RefreshedAt=(Get-Date -UnixTimeSeconds $payload.iat); Expiration=(Get-Date -UnixTimeSeconds $payload.exp)}
}

function Show-KnownAccounts {
    Get-ChildItem -Path $PathMtgaAccounts -Name | ForEach-Object { Get-AccountDetails $_ } | Format-Table
}

function Wait-ForKey {
    Write-Output 'Press any key to continue...'
    $null = $Host.UI.RawUI.ReadKey('NoEcho,IncludeKeyDown');
}

# Create Key to store the various accounts
New-Item -Path PathMtgaAccounts -ErrorAction Ignore

Backup-CurrentRefreshToken

if ($Account) {
    $accountRefreshToken = Get-BackupValue $Account $PropertyWASRefreshToken
    if (-not $accountRefreshToken) {
        Write-Output "Account ${Account} not found."
        Show-KnownAccounts
        Wait-ForKey
        exit 0
    }

    Copy-ItemProperty -Path "$PathMtgaAccounts/$Account" -Destination $PathMtga -Name $PropertyWASRefreshToken
    Set-ItemProperty -Path $PathMtga -Name $PropertyWASRememberMe -Value ([System.Text.Encoding]::ASCII).GetBytes("True`u{0}")
    # Launch Arena if it's not already running.
    $arenaProc = Get-Process -Name "MTGA" -ErrorAction SilentlyContinue
    if (-Not $arenaProc) {
        & $SteamExe steam://rungameid/2141910
    }
} else {
    Write-Output "No account parameter specified. Specify account ID to launch Arena with that account."
    Show-KnownAccounts
    Wait-ForKey
}