feat(server): add threaded http server

lib/prism/server.rb

@@ -0,0 +1,120 @@
+module Prism
+  class Server
+    StatusTexts = {
+      200 => 'OK', 201 => 'Created', 204 => 'No Content',
+      301 => 'Moved Permanently', 302 => 'Found', 303 => 'See Other',
+      304 => 'Not Modified', 400 => 'Bad Request', 401 => 'Unauthorized',
+      403 => 'Forbidden', 404 => 'Not Found', 405 => 'Method Not Allowed',
+      422 => 'Unprocessable Entity', 500 => 'Internal Server Error'
+    }.freeze
+
+    attr_reader :host, :port
+
+    def initialize(app, host: '127.0.0.1', port: 0)
+      @app = app
+      @host = host
+      @requested_port = port
+    end
+
+    def start
+      @server = TCPServer.new(@host, @requested_port)
+      @port = @server.addr[1]
+      @thread = Thread.new { accept_loop }
+      self
+    end
+
+    def stop
+      @server&.close
+      @thread&.join(1)
+      self
+    end
+
+    def url(path = '/')
+      "http://#{@host}:#{@port}#{path}"
+    end
+
+    private
+
+    def accept_loop
+      loop do
+        client = @server.accept
+        Thread.new(client) { |socket| serve(socket) }
+      end
+    rescue IOError, Errno::EBADF
+      nil
+    end
+
+    def serve(socket)
+      loop do
+        env = read_request(socket)
+        break unless env
+        status, headers, body = @app.call(env)
+        keep_alive = keep_alive?(env, headers)
+        write_response(socket, status, headers, body, keep_alive)
+        break unless keep_alive
+      end
+    rescue Errno::EPIPE, Errno::ECONNRESET, IOError
+      nil
+    ensure
+      socket.close unless socket.closed?
+    end
+
+    def read_request(socket)
+      request_line = socket.gets("\r\n")
+      return nil if request_line.nil?
+      request_line = request_line.strip
+      return nil if request_line.empty?
+
+      method, target, = request_line.split(' ', 3)
+      path, query = target.split('?', 2)
+
+      headers = {}
+      while (line = socket.gets("\r\n"))
+        line = line.chomp("\r\n")
+        break if line.empty?
+        name, value = line.split(':', 2)
+        headers[name.strip.downcase] = value.to_s.strip
+      end
+
+      env = {
+        'REQUEST_METHOD' => method,
+        'PATH_INFO' => path,
+        'QUERY_STRING' => query.to_s,
+        'SERVER_NAME' => @host,
+        'SERVER_PORT' => @port.to_s,
+        'rack.url_scheme' => 'http'
+      }
+      headers.each do |name, value|
+        env["HTTP_#{name.upcase.tr('-', '_')}"] = value
+      end
+      env['CONTENT_TYPE'] = headers['content-type'] if headers['content-type']
+      length = headers['content-length'].to_i
+      env['CONTENT_LENGTH'] = length.to_s
+      env['rack.input'] = StringIO.new(length.positive? ? socket.read(length) : '')
+      env
+    end
+
+    def keep_alive?(env, headers)
+      return false if headers['Connection'].to_s.downcase == 'close'
+      env['HTTP_CONNECTION'].to_s.downcase != 'close'
+    end
+
+    def write_response(socket, status, headers, body, keep_alive)
+      payload = body.join
+      out = +"HTTP/1.1 #{status} #{status_text(status)}\r\n"
+      response_headers = headers.dup
+      response_headers['Content-Length'] = payload.bytesize.to_s
+      response_headers['Connection'] = keep_alive ? 'keep-alive' : 'close'
+      response_headers.each do |name, value|
+        value.to_s.split("\n").each { |entry| out << "#{name}: #{entry}\r\n" }
+      end
+      out << "\r\n"
+      socket.write(out)
+      socket.write(payload) unless payload.empty?
+    end
+
+    def status_text(status)
+      StatusTexts.fetch(status, 'OK')
+    end
+  end
+end