[WIP] Start script for gradle's application plugin generated apps.

powerShellStartScript.ps1

$FlagDebug = $true

$default_jvm_opts = ""

function debug {
    if ($FlagDebug) {
        Write-Host -foreground "yellow" $Args 
    }
}

function java_not_found {
    Write-Error @"
JAVA_HOME is set to an invalid directory: $java_home

Please set the JAVA_HOME variable in your environment
to match the location of your Java installation.
"@
    exit 1    
}

function find_java {
    if ($env:JAVA_HOME) {
        $java = Get-Command -ErrorAction SilentlyContinue $(Join-Path $env:JAVA_HOME "bin/java.exe")
        if ($java) {
            debug "Found java via JAVA_HOME"
            return $java
        }
    }
    else {
        $java = Get-Command "java.exe" -ErrorAction SilentlyContinue
        if ($java) {
            debug "Found java via PATH"
            return $java
        }
    }
    # Looking into the registry
    foreach ($k in @('Java Development Kit', 'Java Runtime Environment')) {
        $key = Join-Path 'HKLM:\SOFTWARE\JavaSoft' $k
        if (-not $(Test-Path $key)) {
            continue
        }
        $current = $(Get-Item $key).GetValue('CurrentVersion')
        if (-not $current) {
            continue
        }
        $java_home = $(Get-Item $(Join-Path $key $current)).GetValue('JavaHome')
        if ($java_home) {
            $java = Get-Command -ErrorAction SilentlyContinue $(Join-Path $java_home "bin/java.exe")
            if ($java) {
                debug "Found java via registry ($key)"
                return $java
            }
        }
    }
    return $null
}

$app_home = Split-Path -parent $PSScriptRoot

# $app_base_name = Split-Path -leaf $PSCommandPath
# debug "app_base = ${app_base_name}, app_home = ${app_home}"

$java_exe = find_java

if (-not $java_exe) {
    java_not_found
}

$classpath = ""

& $java_exe $default_jvm_opts $env:JVM_OPTS $env:FOOAPP_OPTS -classpath $classpath Main $Args

exit $LASTEXITCODE