# win8-bridge-agent-marker
# ============================================================================
#  win8-bridge agent  -  runs on the Windows PC as SYSTEM (scheduled task "win8-bridge" -> launcher.ps1 -> this)
#  Long-polls https://win8.ashavolian.com/api/poll for jobs from the Mac Mini, runs them, posts the results back.
#  Outbound HTTPS only. PowerShell 3.0 / .NET 4.5 compatible (Windows 8). ASCII only.
#  Job kinds: ps (PowerShell), cmd (cmd.exe), put (download file from Mac), get (upload file to Mac), update (refresh me)
# ============================================================================
$ErrorActionPreference = 'Continue'
$AgentVersion = '2.0'
$Base = 'https://win8.ashavolian.com'

$Dir = $env:WIN8_BRIDGE_DIR
if (-not $Dir) { $Dir = Join-Path $env:ProgramData 'win8-bridge' }
$PsExe = $env:WIN8_BRIDGE_PSEXE
if (-not $PsExe) { $PsExe = Join-Path $env:SystemRoot 'System32\WindowsPowerShell\v1.0\powershell.exe' }
$CmdExe = $null
if ($env:SystemRoot) { $CmdExe = Join-Path $env:SystemRoot 'System32\cmd.exe' }
$IsWin = ($env:OS -eq 'Windows_NT')

$JobDir    = Join-Path $Dir 'jobs'
$LogFile   = Join-Path $Dir 'agent.log'
$TokenFile = Join-Path $Dir 'token'
if (-not (Test-Path $JobDir)) { $null = New-Item -ItemType Directory -Path $JobDir -Force }

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
[Net.ServicePointManager]::Expect100Continue = $false

function Log($m) {
    $line = (Get-Date).ToString('yyyy-MM-dd HH:mm:ss') + ' ' + $m
    try {
        if ((Test-Path $LogFile) -and ((Get-Item $LogFile).Length -gt 5MB)) { Move-Item $LogFile ($LogFile + '.1') -Force }
        Add-Content -Path $LogFile -Value $line -Encoding ASCII
    } catch { }
}

$Token = (Get-Content $TokenFile -ErrorAction Stop | Select-Object -First 1).Trim()
$osInfo = $null
if ($IsWin) { try { $osInfo = Get-WmiObject Win32_OperatingSystem } catch { } }
$info = @{ hostname = $env:COMPUTERNAME; agent = $AgentVersion; ps = ('' + $PSVersionTable.PSVersion); pid = $PID }
if ($osInfo) { $info['os'] = $osInfo.Caption.Trim(); $info['osver'] = $osInfo.Version }
$InfoJson = $info | ConvertTo-Json -Compress

function New-Client {
    $wc = New-Object Net.WebClient
    $wc.Headers['Authorization'] = 'Bearer ' + $Token
    $wc.Headers['X-Agent-Info'] = $InfoJson
    $wc.Headers['User-Agent'] = 'win8-bridge-agent/' + $AgentVersion
    $wc.Encoding = [Text.Encoding]::UTF8
    return $wc
}

function Err-Text($e) {
    $m = $e.Exception.Message
    if ($e.Exception.InnerException) { $m = $m + ' / ' + $e.Exception.InnerException.Message }
    return $m
}

function Clip($s, $max) {
    if ($null -eq $s) { return '' }
    if ($s.Length -le $max) { return $s }
    return $s.Substring(0, $max) + "`r`n...[truncated " + ($s.Length - $max) + ' chars]'
}

function Start-Child($exe, $argString, $timeoutSec, $outFile, $errFile) {
    $sp = @{ FilePath = $exe; ArgumentList = $argString; RedirectStandardOutput = $outFile; RedirectStandardError = $errFile; PassThru = $true }
    if ($IsWin) { $sp['WindowStyle'] = 'Hidden' }
    $p = Start-Process @sp
    $timedOut = $false
    if (-not $p.WaitForExit([int]$timeoutSec * 1000)) {
        $timedOut = $true
        try { $p.Kill() } catch { }
        Start-Sleep -Milliseconds 500
    }
    $code = 0
    try { $code = $p.ExitCode } catch { }
    if ($timedOut) { $code = 124 }
    return $code
}

function Read-Output($file, $enc) {
    if (-not (Test-Path $file)) { return '' }
    try { return [IO.File]::ReadAllText($file, $enc) } catch { return '' }
}

function Run-Job($job) {
    $started = Get-Date
    $r = @{ exit = 0; stdout = ''; stderr = ''; kind = ('' + $job.kind); started = $started.ToString('s'); agent = $AgentVersion }
    $timeout = 120
    if ($job.timeout) { $timeout = [int]$job.timeout }
    $exitAfter = $false
    try {
        switch ($job.kind) {
            'ps' {
                $script = Join-Path $JobDir ($job.id + '.ps1')
                $outF = Join-Path $JobDir ($job.id + '.out'); $errF = Join-Path $JobDir ($job.id + '.err')
                $body = "[Console]::OutputEncoding = [Text.Encoding]::UTF8`r`n`$ErrorActionPreference = 'Continue'`r`ntry {`r`n" + $job.cmd + "`r`n} catch { `$_ | Out-String | Write-Error; exit 1 }`r`n"
                [IO.File]::WriteAllText($script, $body, [Text.Encoding]::UTF8)
                $r['exit'] = Start-Child $PsExe ('-NoProfile -NonInteractive -ExecutionPolicy Bypass -File "' + $script + '"') $timeout $outF $errF
                $r['stdout'] = Clip (Read-Output $outF ([Text.Encoding]::UTF8)) 1000000
                $r['stderr'] = Clip (Read-Output $errF ([Text.Encoding]::UTF8)) 200000
                if ($r['exit'] -eq 124) { $r['stderr'] += "`r`n[agent] killed after " + $timeout + 's timeout' }
                Remove-Item $script, $outF, $errF -Force -ErrorAction SilentlyContinue
            }
            'cmd' {
                if (-not $CmdExe) { throw 'cmd.exe not available here' }
                $script = Join-Path $JobDir ($job.id + '.cmd')
                $outF = Join-Path $JobDir ($job.id + '.out'); $errF = Join-Path $JobDir ($job.id + '.err')
                [IO.File]::WriteAllText($script, "@echo off`r`n" + $job.cmd + "`r`n", [Text.Encoding]::Default)
                $r['exit'] = Start-Child $CmdExe ('/d /c "' + $script + '"') $timeout $outF $errF
                $enc = [Console]::OutputEncoding
                $r['stdout'] = Clip (Read-Output $outF $enc) 1000000
                $r['stderr'] = Clip (Read-Output $errF $enc) 200000
                if ($r['exit'] -eq 124) { $r['stderr'] += "`r`n[agent] killed after " + $timeout + 's timeout' }
                Remove-Item $script, $outF, $errF -Force -ErrorAction SilentlyContinue
            }
            'put' {
                $dest = '' + $job.path
                $parent = Split-Path $dest -Parent
                if ($parent -and -not (Test-Path $parent)) { $null = New-Item -ItemType Directory -Path $parent -Force }
                $wc = New-Client
                $wc.DownloadFile($Base + '/api/blob/' + $job.blob, $dest)
                $r['stdout'] = 'wrote ' + (Get-Item $dest).Length + ' bytes to ' + $dest
            }
            'get' {
                $src = '' + $job.path
                if (-not (Test-Path $src)) { throw ('no such file: ' + $src) }
                $bytes = [IO.File]::ReadAllBytes($src)
                $wc = New-Client
                $wc.Headers['Content-Type'] = 'application/octet-stream'
                $null = $wc.UploadData($Base + '/api/blob/' + $job.id, 'PUT', $bytes)
                $r['stdout'] = 'uploaded ' + $bytes.Length + ' bytes from ' + $src
            }
            'update' {
                $wc = New-Client
                $new = $wc.DownloadString($Base + '/agent.ps1')
                if ($new -notlike '*win8-bridge-agent-marker*') { throw 'downloaded agent.ps1 failed validation' }
                [IO.File]::WriteAllText((Join-Path $Dir 'agent.ps1'), $new, [Text.Encoding]::ASCII)
                $r['stdout'] = 'agent.ps1 replaced; agent restarting'
                $exitAfter = $true
            }
            default { throw ('unknown job kind: ' + $job.kind) }
        }
    } catch {
        $r['exit'] = 1
        $r['stderr'] = ('' + $r['stderr'] + "`r`n[agent] " + (Err-Text $_)).Trim()
    }
    $r['finished'] = (Get-Date).ToString('s')
    $r['seconds'] = [int]((Get-Date) - $started).TotalSeconds
    Post-Result $job.id $r
    Log ('job ' + $job.id + ' (' + $job.kind + ') exit=' + $r['exit'] + ' in ' + $r['seconds'] + 's')
    if ($exitAfter) { Log 'exiting for update'; exit 0 }
}

function Post-Result($jobId, $r) {
    $json = $r | ConvertTo-Json -Compress -Depth 3
    for ($i = 0; $i -lt 6; $i++) {
        try {
            $wc = New-Client
            $wc.Headers['Content-Type'] = 'application/json'
            $null = $wc.UploadString($Base + '/api/result/' + $jobId, 'POST', $json)
            return
        } catch {
            Log ('result post failed (try ' + ($i + 1) + '): ' + (Err-Text $_))
            Start-Sleep -Seconds (5 * ($i + 1))
        }
    }
}

# housekeeping: drop job scratch files older than a day
try { Get-ChildItem $JobDir -ErrorAction SilentlyContinue | Where-Object { $_.LastWriteTime -lt (Get-Date).AddDays(-1) } | Remove-Item -Force -ErrorAction SilentlyContinue } catch { }

Log ('agent ' + $AgentVersion + ' starting, base ' + $Base + ', host ' + $env:COMPUTERNAME)
$backoff = 5
while ($true) {
    try {
        $wc = New-Client
        $resp = $wc.DownloadString($Base + '/api/poll?wait=25')
        $backoff = 5
        if ($resp -and $resp.Trim() -ne '{}') {
            $job = ConvertFrom-Json $resp
            if ($job.id) { Run-Job $job }
        }
    } catch {
        Log ('poll error: ' + (Err-Text $_))
        Start-Sleep -Seconds $backoff
        if ($backoff -lt 120) { $backoff = $backoff * 2 }
    }
}