Update toolchains.xml using jabba managed jdks

update-toolchains.ps1

# check if jabba is installed
Get-Command -ErrorAction Stop jabba > $null

function Resolve-PathSymlink
{
    param(
        [string]
        $Path
    )
    $item = Get-Item $Path
    if ($item.Target.Count -gt 0)
    {
        $item.Target[0]
    }
    else
    {
        $item.FullName
    }
}

function Get-Jdk-Version
{
    param(
        [string]
        $Path
    )
    $output = & "$( $_.path )\bin\java" -version 2>&1
    $parts = $output -split '\n'
    if ( $parts[0].StartsWith("Picked up JAVA_TOOL_OPTIONS"))
    {
        $parts[1]
    }
    else
    {
        $parts[0]
    }
}

function Resolve-Version
{
    param(
        [string]
        $Version
    )
    if ($Version -match ".*version `"([.\d_-]+)`".*")
    {
        $fullVersion = $Matches[1]
        if ($fullVersion -match "(\d+\.\d+).*")
        {
            $Matches[1]
        }
        else
        {
            $fullVersion
        }
    }
    else
    {
        $Version
    }
}

function Build-Toolchain
{
    param(
        [PSObject]
        $JDKs
    )
    $out = @"
<?xml version="1.0" encoding="UTF8"?>
<toolchains>
"@
    $JDKs | ForEach-Object {
        $out += @"

  <toolchain>
    <type>jdk</type>
    <provides>
      <version>$($_.version)</version>
    </provides>
    <configuration>
      <jdkHome>$($_.path)</jdkHome>
    </configuration>
  </toolchain>
"@
    }


    $out += "`n</toolchains>"
    $out
}

$jdkCandidates = jabba ls

$jdkWithPath = $jdkCandidates `
               | ForEach-Object { New-Object PsObject -Property @{ id = $_; path = ""; version = "" } } `
               | ForEach-Object { $_.path = Resolve-PathSymlink -Path (jabba which $_.id); $_ }

$jdkWithPath | Where-Object { !(Test-Path $_.path) } `
             | ForEach-Object { Write-Warning "Invalid JDK reference $( $_ )" }

$validJdks = $jdkWithPath | Where-Object { Test-Path $_.path } `
                          | ForEach-Object { $_.version = Resolve-Version (Get-Jdk-Version $_.path); $_ }

$validJdks | Format-Table

# using -Encoding ascii, since the default utf8 encoding in powershell adds a BOM
# and since we shouldn't have any non-ascii characters in our output it is equivalent to utf8 without bom
Build-Toolchain -JDKs $validJdks | Out-File -FilePath "$($env:USERPROFILE)\.m2\toolchains.xml" -Encoding ascii
Write-Host "Updated toolchains.xml"