#!/usr/bin/ruby

STOREDIR = '/var/spool/denbun'
PROTO = 'https'
SSLPORT = 443

# ruby 1.9 compatibility
unless ''.respond_to?(:bytesize)
  class String
    alias :bytesize :size
  end
end

class Time
  def http
    utc.strftime('%a, %d %b %Y %H:%M:%S GMT')
  end
end

class MyCGI

  def initialize
    @method = ENV['REQUEST_METHOD']
    @path = ENV['PATH_INFO']
    @ctype = ENV['CONTENT_TYPE']
    @ruser = ENV['REMOTE_USER'].to_s.gsub(/[^-\w]/, '_')
    @server = ENV['SERVER_NAME']
    @port = ENV['SERVER_PORT']
    @script = ENV['SCRIPT_NAME']
    @md5 = ENV['HTTP_CONTENT_MD5']
    @cenc = ENV['HTTP_CONTENT_ENCODING']
    @body = nil
    @param = nil
  end

  attr_reader :method, :path, :ruser, :server, :port, :script

  def body
    return @body if @body
    @body = $stdin.read
    if @md5
      begin
        require 'digest/md5'
	dg = [Digest::MD5.digest(@body)].pack('m').strip
	if @md5 != dg
	  raise "409 Conflict\tMD5 mismatch #{dg} #{@md5}"
	end
      rescue LoadError
        # do nothing
      end
    end
    case @cenc
    when nil, /^identity$/
      # do nothing
    when /^(x-)?gzip$/
      begin
	require 'zlib'
	require 'stringio'
      rescue Exception
        raise "415 Unsupported Media Type\tcontent-encoding=gzip, zlib missing"
      end
      StringIO.new(@body.dup) {|sio|
	@body = Zlib::GzipReader.wrap(sio).read
      }
    else
      raise "415 Unsupported Media Type\tcontent-encoding #{@cenc} unsupported"
    end
    return @body
  end

  def parse_header str
    hdr = {}
    buf = []
    for line in str.split(/\r?\n/)
      case line
      when /^$/ then
      when /^\s/ then
        name = buf.shift.to_s.downcase
        hdr[name] = yield(name, buf.join)
	buf = []
      when /^(\S+):/ then
        name = buf.shift.to_s.downcase
        hdr[name] = yield(name, buf.join)
	buf = []
        buf.push $1
	buf.push $'
      else
        buf.push '(error)'
        buf.push line
      end
    end
    name = buf.shift.to_s.downcase
    hdr[name] = yield(name, buf.join)
    hdr
  end

  def param
    return @param if @param
    h = {}
    case @ctype.to_s.strip
    when /^multipart\/form-data\s*;\s*boundary\s*=\s*("([^"]*)"|(\S*))/
      boundary = "\r\n--" + ($2 or $3).to_s
      body.sub(/^/, "\r\n").split(boundary).each {|part|
        next if part.empty?
	next if /^--/ === part
	ph, pb = part.split(/\r?\n\r?\n/, 2)
	hx = parse_header(ph) {|n, s|
	  case n
	  when /^content-(type|disposition)$/ then
	    mt = {}
	    s.split(/\s*;\s*/).map{|f|
	      case f
	      when /=/ then
	        k, v = $`, $'
		v = $1 if /^"([^"]*)"$/ === v
	        mt[k] = v
	      else mt[''] = f.strip
	      end
	    }
	    mt
	  else s
	  end
	}
	cd = hx['content-disposition']
	next unless cd
	case hx['content-transfer-encoding'].to_s.strip
	when /^(7bit|8bit|binary)$/ then # do nothing
	when /^base64$/ then
	  pb = pb.unpack('m').first
	when /^quoted-printable$/ then
	  pb = pb.unpack('M').first
	end
	hx[''] = pb
	h[cd['name']] = hx
      }
    when /multipart\/form-data/
      raise "415 Unsupported Media Type\tmultipart requires boundary"
    else
      raise "415 Unsupported Media Type\tUnknown content type '#{@ctype}'"
    end
    @param = h
  end

end

class Response

  def initialize
    @code = '200 Ok'
    @type = 'text/plain'
    @body = ''
    @header = {}
  end

  attr_writer :code
  attr_writer :type
  attr_writer :body

  def []=(name, val)
    @header[name] = val
  end

  def output(fp)
    fp.write("Status: #{@code}\n")
    for name, val in @header
      fp.write("#{name}: #{val}\r\n")
    end
    fp.write("Content-Type: #{@type}\n") if @type
    fp.write("Content-Length: #{@body.bytesize}\n")
    fp.write("\n")
    fp.write(@body)
  end

end

class App

  def initialize
    @resp = Response.new
    @c = MyCGI.new
  end

  def authcheck
    unless SSLPORT == @c.port.to_i
      @resp['location'] = make_url(@c.path, SSLPORT)
      raise "301 Moved Permanently\tUse SSL/TLS!"
    end
    case @c.ruser
    when /^-?$/
      raise "401 Unauthorized\tREMOTE_USER='#{@c.ruser}'"
    end
  end

  def list
    Dir.open(STOREDIR) {|dp|
      for file in dp
        next if /^\./ === file
	next unless file.index(@c.ruser) == 0
	next unless /^[-+.\w]+$/ === file
	yield file.sub(/^[^.]+\./, '')
      end
    }
    File.stat(STOREDIR).mtime
  end

  def retr basename
    begin
      fnam = File.join(STOREDIR, bnam = "#{@c.ruser}.#{basename}")
      [File.read(fnam), File.stat(fnam).mtime]
    rescue Errno::ENOENT
      raise "404 Not Found\tfile #{bnam} not found"
    rescue Errno::EACCES
      raise "403 Forbidden\tpermission denied for #{bnam}"
    end
  end

  def store data, filename
    begin
      fnam = File.join(STOREDIR, bnam = "#{@c.ruser}.#{filename}")
      tfnam = File.join(STOREDIR, ".#{@c.ruser}.#{filename}.tmp")
      File.open(tfnam, 'w') {|fp|
        fp.write data
      }
      overwriting = File.exist?(fnam)
      File.rename(tfnam, fnam)
      return overwriting
    rescue Errno::ENOENT => e
      unless File.directory?(STOREDIR)
	raise "404 Not Found\tmkdir #{STOREDIR} please"
      end
      raise e
    rescue Errno::EACCES
      raise "403 Forbidden\tpermission denied for #{bnam} - check #{STOREDIR}"
    end
  end

  def rest_basename
    raise "403 Forbidden\tpath_info missing" unless @c.path
    basename = File.basename(@c.path)
    case basename
    when /^\/?$/ then raise "403 Forbidden\tpath_info empty"
    end
    basename
  end


  def make_url basename, port = nil
    a = [ PROTO, '://', @c.server ]
    port = @c.port if port.nil?
    case [ PROTO, ':', port ].join
    when /^http:80$/, /^https:443$/ then
      # do nothing
    else
      a << [':', port]
    end
    a << [@c.script, '/', basename]
    a.join
  end

  def parse_put
    basename = rest_basename
    if store(@c.body, basename)
      @resp.code = "204 No Content"
      @resp.type = nil
    else
      @resp.code = "201 Created"
      @resp['location'] = url = make_url(basename)
      @resp.type = 'text/plain'
      @resp.body = "#{url} created"
    end
  end

  def parse_post
    upld = @c.param['uploaded']
    raise "403 Forbidden\tuploaded file missing" unless upld
    basename = File.basename(upld['content-disposition']['filename'].to_s)
    raise "403 Forbidden\tfilename missing" if basename.empty?
    store(upld[''], basename)
    @resp.code = "201 Created"
    @resp['location'] = url = make_url(basename)
    @resp.type = 'text/plain'
    @resp.body = "#{url} created\n"
  end

  def parse_get
    bname = rest_basename
    case bname
    when /^index\.html$/ then
      buf = [
        '<html xmlns="http://www.w3.org/1999/xhtml"><head>',
        "<title>listing for user #{@c.ruser}</title>",
        '</head><body><ul>' ]
      mtime = list() do |file|
        buf << "<li><a href='#{file}'>#{file}</a></li>"
      end
      buf << '</ul></body></html>'
      @resp.body = buf.join
      @resp['last-update'] = mtime.http
      @resp.type = 'application/xhtml+xml'
    else
      body, mtime = retr(bname)
      @resp.body = body
      @resp['last-modified'] = mtime.http
      @resp.type = 'application/octet-stream'
    end
    @resp.code = '200 Ok'
  end

  def main
    authcheck
    case @c.method
    when /^PUT$/ then parse_put
    when /^POST$/ then parse_post
    when /^GET$/ then parse_get
    else raise "501 Unimplemented\tMethod '#{@c.method}' not implemented"
    end
  end

  def run
    begin
      main
    rescue Exception => e
      msg = e.message
      @resp.code = '500 Internal Server Error'
      if /^(\d+ [^\t]+)\t/ === msg
        @resp.code = $1
        msg = $'
      end
      @resp.body = "#{msg} (#{e.class.to_s})\n"
    end
    @resp.output($stdout)
  end

end

App.new.run