cordite-cli/deepromise-repl.js

a command line tool for accessing a Corda node running cordite cordapps or braid

/*
 *   Copyright 2018, Cordite Foundation.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
/**
 * The following routine `depromisfy` intercepts calls on a repl
 * unwrapping member invocations, a providing automatic handlers for 
 * asynchronous functions that return promises
 * 
 * The design is strictly based on the excellent `esprima` 
 * parsing library, and its abstract syntax tree object model.
 * 
 * @author fuzz
 */

const rewrite=require('./deepromise');

class DeepromiseRepl {
  constructor(replServer) {
    const that = {}
    that.replServer = replServer;
    that.oldEval = that.replServer.eval;
    that.replServer.eval = function (cmd, context, filename, callback) {
      try {
         // to support later versions of node
        if (cmd.startsWith('try {') && cmd.endsWith('catch {}')) {
            return that.oldEval(cmd, context, filename, callback);
        }

        const script = rewrite(cmd);
        that.oldEval(script, context, filename, (err, res) => {
          // Error response
          if (err) {
            return callback(err);
          }
  
          // Non-thenable response
          if (!res || typeof res.then != 'function') {
            return callback(null, res);
          }
  
          // Start listening for escape characters, to quit waiting on the promise
          var cancel = function (chunk, key) {
            replServer.outputStream.write('break.\n');
            if (key.name === 'escape') {
              process.stdin.removeListener('keypress', cancel);
              callback(null, res);
              // Ensure we don't call the callback again
              callback = function () { };
            }
          };
          process.stdin.on('keypress', cancel);
  
          // Start a timer indicating that escape can be used to quit
          var hangTimer = setTimeout(function () {
            replServer.outputStream.write('Hit escape to stop waiting on promise\n');
          }, 5000);
  
          res.then(function (val) {
            process.stdin.removeListener('keypress', cancel);
            clearTimeout(hangTimer);
            callback(null, val)
          }, function (err) {
            process.stdin.removeListener('keypress', cancel);
            clearTimeout(hangTimer);
            replServer.outputStream.write('Promise rejected: ');
            callback(err);
          }).then(null, function (uncaught) {
            // Rethrow uncaught exceptions
            process.nextTick(function () {
              throw uncaught;
            });
          });
        });
      } catch (err) {
        callback(err);
      }
    }
  }
}

function deepromisify(replServer) {
  new DeepromiseRepl(replServer);
}

module.exports = deepromisify