# VCN #49 The Swarm - check a machine can run parallel coding agents in git worktrees.
# DOCTOR ONLY. This script changes NOTHING: it creates no worktree, no branch, no
# file, and touches no global config. It reads your git version and repo state and
# tells you whether tonight's lab will work here.
#
# Run:    irm https://vcn-49-the-swarm.vercel.app/wire.ps1 | iex
# From inside the repo you are bringing:
#         cd your-repo; irm https://vcn-49-the-swarm.vercel.app/wire.ps1 | iex
#
# To also do a real worktree add/list/remove round-trip in a temp dir and clean up:
#         $env:SWARM_PROBE=1; irm https://vcn-49-the-swarm.vercel.app/wire.ps1 | iex
#
# There are NO credentials in this file and it prints none. ASCII only.
# Nothing to uninstall: the default run writes nothing.

$ErrorActionPreference = 'Continue'
$script:Failed = 0

function Ok   ($m) { Write-Host ("  OK    " + $m) }
function Warn ($m) { Write-Host ("  WARN  " + $m) }
function Bad  ($m) { Write-Host ("  FAIL  " + $m); $script:Failed = 1 }
function Have ($c) { $null -ne (Get-Command $c -ErrorAction SilentlyContinue) }

Write-Host ""
Write-Host "VCN #49 The Swarm - machine doctor"
Write-Host "-----------------------------------"

# 1. git present, and new enough for worktrees (shipped in 2.5, Jul 2015).
if (Have git) {
  $gv = (git --version) -replace '[^0-9\.]', '' -split '\.'
  $maj = [int]($gv[0]); $min = [int]($gv[1])
  if ($maj -gt 2 -or ($maj -eq 2 -and $min -ge 5)) {
    Ok ("git " + $maj + "." + $min + " (worktrees need 2.5+)")
  } else {
    Bad ("git " + $maj + "." + $min + " is older than 2.5 - no worktree support")
  }
} else {
  Bad "git not found on PATH"
}

# 2. Claude Code, the thing that drives each worker.
if (Have claude) { Ok "claude on PATH" }
else { Warn "claude not on PATH - you need it to drive the agents" }

# 3. Are we inside a repo?
$inRepo = $false
if (Have git) {
  git rev-parse --git-dir *> $null
  if ($LASTEXITCODE -eq 0) { $inRepo = $true; Ok "inside a git repo" }
  else { Warn "not inside a git repo - re-run from the repo you are bringing tonight" }
}

if ($inRepo) {
  # 4. Clean tree. Worktree add works dirty, but tonight you merge three branches
  #    back, and an unrelated dirty file turns a clean merge into a confusing one.
  # 2>$null: some git configs emit "warning: untracked cache is disabled" on
  # every status, which is noise in a doctor whose whole job is a clean report.
  $st = git status --porcelain 2>$null
  if ([string]::IsNullOrWhiteSpace(($st | Out-String))) { Ok "working tree is clean" }
  else { Warn "working tree is dirty - commit or stash before the lab" }

  # 5. Existing worktrees. One is the normal starting state.
  $n = @(git worktree list).Count
  if ($n -le 1) { Ok ("worktrees: " + $n + " (a clean starting point)") }
  else { Warn ("worktrees: " + $n + " already exist - 'git worktree list' to see them") }

  # 6. THE ONE THAT BITES ON WINDOWS. A junction inside a worktree is FOLLOWED by
  #    `git worktree remove`, which deletes the TARGET, outside the worktree, and
  #    exits 0 printing nothing. See slide 9. rmdir the link first, never rm -rf.
  $rp = Get-ChildItem -Force -Depth 1 -ErrorAction SilentlyContinue |
        Where-Object { $_.Attributes -band [IO.FileAttributes]::ReparsePoint -or
                       $_.Name -in '.venv','node_modules' } |
        Select-Object -First 5
  if ($rp) {
    Warn "found junctions/links or heavy dirs near the root:"
    $rp | ForEach-Object { Write-Host ("          " + $_.Name) }
    Warn "if you link any of these INTO a worktree, rmdir the link BEFORE removing the tree"
  } else {
    Ok "no obvious reparse points near the repo root"
  }
}

# 7. Optional: prove the mechanism for real, in a temp dir, then clean up.
if ($env:SWARM_PROBE -eq '1' -and (Have git)) {
  Write-Host ""
  Write-Host "  probe: real worktree round-trip in a temp dir"
  $t = Join-Path ([IO.Path]::GetTempPath()) ("swarm-probe-" + [Guid]::NewGuid().ToString('N').Substring(0,8))
  try {
    New-Item -ItemType Directory -Path (Join-Path $t 'r') -Force | Out-Null
    Push-Location (Join-Path $t 'r')
    git init -q . *> $null
    git -c user.name=probe -c user.email=probe@local commit -q --allow-empty -m init *> $null
    git worktree add ../w -b probe/tmp *> $null
    $added = ($LASTEXITCODE -eq 0)
    git worktree remove ../w *> $null
    $removed = ($LASTEXITCODE -eq 0)
    Pop-Location
    if ($added -and $removed) { Ok "worktree add / list / remove all work here" }
    else { Bad "worktree round-trip failed on this machine" }
  } catch {
    Bad "worktree round-trip failed on this machine"
  } finally {
    # os-level rmdir semantics: this temp tree contains no links we created.
    Remove-Item -Recurse -Force $t -ErrorAction SilentlyContinue
  }
}

Write-Host ""
if ($script:Failed -eq 0) {
  Write-Host "  READY. Bring a repo with THREE independent things to do."
  Write-Host "  Independence is the real prerequisite: if two of them edit the"
  Write-Host "  same file, they are one task, and the lab will show you why."
} else {
  Write-Host "  NOT READY. Fix the FAIL lines above, then re-run."
}
Write-Host ""
Write-Host "  Deck:   https://vcn-49-the-swarm.vercel.app"
Write-Host "  Prep:   https://vcn-49-the-swarm.vercel.app/setup.txt"
Write-Host "  Agents: https://vcn-49-the-swarm.vercel.app/llms.txt"
Write-Host ""