tw5putsrv.rb

#!/usr/bin/env ruby
# Like <https://gist.github.com/jimfoltz/ee791c1bdd30ce137bc23cce826096da>
# but cooler. Keep only 10 last revisions, gzipped.

# klg, Jun 2019
require 'securerandom'
require 'webrick'
require 'zlib'

class Tw5 < WEBrick::HTTPServlet::AbstractServlet

  def do_OPTIONS req, res
    res['allow'] = 'GET,HEAD,OPTIONS,PUT'
    res['dav'] = 'tw5/put' # has DAV but not compatible
  end

  def do_GET req, res
    f = File.open "./#{req.path}.gz"
    st = f.stat
    make_validators res, st
    check_validators req, res
    res['content-type'] = 'text/html;charset=utf-8'
    if a = req['accept-encoding'] and
        WEBrick::HTTPUtils.parse_qvalues(a).member?('gzip')
      res['content-encoding'] = 'gzip'
      res['content-length'] = st.size
      res.body = f
    else
      Zlib::GzipReader.open f do |gz|
        res.body = gz.read
      end
      f.close
    end
    res.status = 200
  rescue Errno::ENOENT
    begin
      f = File.open "./#{req.path}"
      st = f.stat
      unless st.file?
        raise WEBrick::HTTPStatus::NotFound.new "#{req.path} not found."
      end
      make_validators res, st
      check_validators req, res
      res['content-length'] = st.size
      res.body = f
      res.status = 200
    rescue Errno::ENOENT
      raise WEBrick::HTTPStatus::NotFound.new "#{req.path} not found."
    end
  end

  def do_PUT req, res
    if req['content-range'] || req['content-encoding']
      raise WEBrick::HTTPStatus::NotImplemented
    end

    path = "./#{req.path}.gz".gsub /\/\.*(?=\/|$)/, ''
    tmpn = "./tmp.#{$$}-#{SecureRandom.hex(6)}"

    Zlib::GzipWriter.open tmpn do |gz|
      req.body { |chunk| gz.write chunk }
    end

    res.status = 204
    rev = 0

    File.open '.' do |dir|
      dir.flock File::LOCK_EX
      begin
        make_validators res, File.stat(path)
        check_validators req, res
        rev = File.readlink(path).match(/;([0-9]+)$/)[1].to_i
      rescue Errno::EINVAL
        File.link path, "#{path};0"
      rescue Errno::ENOENT
        res.status = 201
      end
      rev += 1
      File.rename tmpn, "#{path};#{rev}"
      rpath = path.gsub /.*\//, ''
      File.symlink "#{rpath};#{rev}", tmpn
      File.rename tmpn, path
      make_validators res, File.stat(path)
    end

    if rev >= 10
      begin
        File.unlink "#{path};#{rev - 10}"
      rescue Errno::ENOENT
      end
    end
  ensure
    begin
      File.unlink tmpn
    rescue Errno::ENOENT
    end
  end

  def make_validators res, stat
    mtime = stat.mtime
    res['last-modified'] = mtime.httpdate
    res['etag'] = etag = sprintf '%x-%x-%x', stat.ino, stat.size, mtime.to_i
  end

  def check_validators req, res
    mtime = Time.parse(res['last-modified'])
    etag = res['etag']
    if x = req['if-match'] and etag.nil? ||
        x != '*' && !WEBrick::HTTPUtils::split_header_value(x).member?(etag)
      raise WEBrick::HTTPStatus::PreconditionFailed
    end
    if x = req['if-none-match'] and
        x == '*' || WEBrick::HTTPUtils::split_header_value(x).member?(etag)
      if %w(GET HEAD).member?(req.request_method)
        raise WEBrick::HTTPStatus::NotModified
      else
        raise WEBrick::HTTPStatus::PreconditionFailed
      end
    end
    begin
      if x = req['if-modified-since'] and
          Time.parse(x) >= mtime
        raise WEBrick::HTTPStatus::NotModified
      end
      if x = req['if-unmodified-since'] and
          !req['if-match'] && Time.parse(x) < mtime
        raise WEBrick::HTTPStatus::PreconditionFailed
      end
    rescue ArgumentError
      # ignore malformed dates
    end
  end

end

if $0 == __FILE__
  server = WEBrick::HTTPServer.new :Port => ENV['PORT'] || 8080
  server.mount '/', Tw5
  trap 'INT' do
    server.shutdown
  end
  server.start
end