Manage a clean homebrew installation

brewfoster

#!/usr/bin/env ruby
require 'pathname'
require 'set'
require 'pp'

def dependencies
  deps = {}
  IO.popen(['brew', 'deps', '--installed']) do |f|
    f.each do |line|
      md = /^([^:]+):\s*(.*)$/.match(line) or raise "Can't parse dependencies"
      deps[md[1]] = md[2].split(' ')
    end
  end
  deps
end

def reverse_dependencies
  revs = {}
  dependencies.each do |pkg, deps|
    revs[pkg] ||= []
    deps.each do |dep|
      revs[dep] ||= []
      revs[dep] << pkg
    end
  end
  revs
end

def keepers
  keepers = Set.new
  Pathname.new('~/keepers').expand_path.each_child do |f|
    f.each_line do |line|
      keepers << line.chomp.sub(/#.*/, '').strip
    end
  end
  keepers
end

def orphans
  deps = dependencies
  seen = Set.new
  q = keepers.to_a
  until q.empty? do
    k = q.shift
    next unless seen.add?(k)
    q.concat(deps.delete(k))
  end
  deps.keys 
end

cmd = ARGV.shift
if cmd == 'orphans'
  orphans.sort.each { |o| puts o }
elsif cmd == 'remove'
  found = orphans
  system('brew', 'remove', *found) unless found.empty?
elsif cmd == 'candidates'
  nodeps = reverse_dependencies.select { |k,v| v.empty? }.keys
  candidates = Set.new(nodeps) - keepers
  candidates.sort.each { |c| puts c }
elsif cmd == 'missing'
  missing = keepers - dependencies.keys
  missing.sort.each { |m| puts m }
elsif cmd.nil? || cmd == 'help'
  help = <<-eos
    Usage: brewfoster COMMAND
  
    Keep a clear brew install, by maintaining a list of desired packages in
    files inside ~/keepers.
  
    Commands include:
      
      orphans: Show packages that can be removed with no effect on keepers
      
      remove: Remove all orphan packages
      
      candidates: Show packages you might want to add to keepers
      
      missing: Show keepers you might want to remove
  eos
  puts help.gsub(/^( ){,4}/, '')
else
  raise "No such command #{cmd}"
end