const cp = require('child_process')
, EventEmitter = require('events').EventEmitter
, Rx = require('rxjs')
, Observable = Rx.Observable
, fromEvent = Rx.fromEvent
, { mergeObjects } = require('../tools/Objects')
, symbolProcessOutput = Symbol('processOutput');
/**
* General purpose class that can represent any result of a terminated Process.
*/
class ProcessResult {
constructor() { };
};
/**
* Inherits from ProcessResult and represents an errored Process. This class
* is usually used for Processes that did not even start or were impossible
* to launch with the given configuration. A Process that started but errored
* then is usually terminated with an instance of ProcessExit.
*/
class ProcessErrorResult extends ProcessResult {
/**
* @param {any} error
*/
constructor(error) {
super();
this.error = error;
};
};
/**
* Inherits from ProcessResult and represents the details of an exited Process.
* This result can either be positive (non-faulted) or negative. The result will
* provide details about the termination, such as exit-code, signal (if available)
* or the contents of stderr and stdout (if configured to be used).
*/
class ProcessExit extends ProcessResult {
/**
* @param {boolean} faulted
* @param {number} code
* @param {string|null} signal
* @param {string|null} stdOut
* @param {string|null} stdErr
*/
constructor(faulted, code, signal, stdOut, stdErr) {
super();
this.faulted = faulted;
this.code = code;
this.signal = signal;
this.stdOut = stdOut;
this.stdErr = stdErr;
};
}
/**
* This class is used for whenever a wrapped Process generates any kind
* of output.
*/
class ProcessOutput {
/**
* @param {'stdout'|'stderr'} streamType
* @param {Buffer|String} chunk
*/
constructor(streamType, chunk) {
this.streamType = streamType;
this.chunk = chunk;
};
get isStdOut() {
return this.streamType === 'stdout';
};
get isStdErr() {
return this.streamType === 'stderr';
};
/**
* Provides the chunk as string, converted to utf-8.
*/
get asString() {
return this.chunk instanceof Buffer ?
this.chunk.toString('utf-8') : this.chunk;
};
}
/**
* Wraps (the execution of) a Process that is created using child_process.
* Provides convenient async behavior and Observables as well as eventing.
*/
class ProcessWrapper extends EventEmitter {
/**
* @param {string} command
* @param {Array.<string>} args
* @param {SpawnOptions|Object} options The same options that child_process.spawn(..) supports.
*/
constructor(command, args = [], options = {}) {
super();
this.command = command;
this.args = args;
this.options = options;
this._wasStarted = false;
this._isRunning = false;
/** @type {Observable.<ProcessOutput>} */
this._observable = fromEvent(this, symbolProcessOutput);
/** @type {ProcessResult} */
this._processResult = void 0;
/** @type {NodeJS.Process} */
this._process = void 0;
};
/**
* Returns the underlying process as returned by child_process.
*
* @throws {Error} if this process was not yet started.
* @returns {NodeJS.Process}
*/
get process() {
if (!this.wasStarted) {
throw new Error('This process was not yet started.');
}
return this._process;
};
/**
* @returns {Boolean}
*/
get wasStarted() {
return this._wasStarted;
};
/**
* @returns {Boolean}
*/
get isRunning() {
return this._isRunning;
};
/**
* Creates and returns a general Observable for any output of this Process. The
* Observable will just observe any emits. Thus it never errors and never drains.
*
* @returns {Observable.<ProcessOutput>}
*/
get observable() {
return this._observable;
};
/**
* This property will yield a value once the Process terminated. Note that in the
* API of Observable, the complete()-function does not support arguments, so that
* we cannot pass in the result there.
* Instead the wrapper guarantees that, once the Process terminated, its result
* will be made available before any events are omitted or complete() gets called.
*
* @returns {ProcessResult|ProcessErrorResult|ProcessExit}
*/
get result() {
return this._processResult;
};
/**
* The default action to run this process. At the moment it defaults to spawn().
* The default behavior may change in the future, so do not rely on this method
* and use the specialized instantiation methods, if you require e.g. fork()
* instead of spawn().
* However regardless, this method guarantees that the process will be executed
* and that its result can be observed or obtained by awaiting its termination
* (that depends on the behavior of 'emitOnly').
*
* @param {boolean} emitOnly If set to true, the resulting value of the resolving
* Promise will be empty (i.e. stdout and stderr will be empty and not be collected
* while the process is running; instead, all output is emitted (events and obser-
* vable) while the process is running). It is recommended to set this to true, if
* the underlying process outputs a lot of data to the std-streams. That data would
* otherwise be held in the node.js process. However, if set to false, the resulting
* value of the Promise will be the process' entire output.
*/
async run(emitOnly = true) {
if (this.isRunning) {
throw new Error('The process is already running.');
}
return await this.spawnAsync(emitOnly);
};
/**
* The default action to start and observe this process. At the moment it defaults
* to spawn() and thus spawnObservable(). The default behavior may change in the future,
* so do not rely on this method and use the specialized instantiation methods, if you
* require e.g. fork() instead of spawn().
* However regardless, this method guarantees that the process will be executed and that
* its result can be observed. When the process errors or terminates, the observable will
* forward those errors or call onComplete() accordingly.
*
* @returns {Observable.<ProcessOutput>}
*/
runObservable() {
return this.spawnObservable();
};
/**
* Calls 'spawnAsync(emitOnly=true)' so that the entire Process becomes
* observable while it runs. When the process errors or finishes, the
* observable will output an error or complete, respectively.
*
* @returns {Observable.<ProcessOutput>}
*/
spawnObservable() {
return new Observable(async subs => {
const subscription = fromEvent(this, symbolProcessOutput)
.subscribe(next => {
subs.next(next);
});
try {
await this.spawnAsync(true);
subs.complete();
} catch (e) {
subs.error(e);
} finally {
subscription.unsubscribe();
}
});
};
/**
* Launches the process using spawn().
*
* @param {boolean} emitOnly Has the same effect as 'run(emitOnly)', please refer
* to the documentation there.
* @returns {Promise.<ProcessResult>} The Promise will be rejected if the process
* exits with a non-zero result or if, when spawning it, an error occurs. In the
* first case, the result will be of type ProcessExit, while in the latter case, it
* will be of type ProcessErrorResult. Both types inherit from ProcessResult.
*/
spawnAsync(emitOnly = true) {
return new Promise((resolve, reject) => {
if (this.isRunning) {
throw new Error('The process is already running.');
}
this._isRunning = true;
/**
* @param {ProcessResult} procExit
*/
const shutdownFunc = procExit => {
this._isRunning = false;
this._processResult = procExit;
if (procExit instanceof ProcessErrorResult
|| (procExit instanceof ProcessExit && procExit.faulted)) {
reject(procExit);
} else {
resolve(procExit);
}
};
/**
* @param {'stdout'|'stderr'} streamName
* @param {Buffer|String} chunk
* @param {Array.<String>} streamArr
*/
const dataFn = (streamName, chunk, streamArr) => {
const out = new ProcessOutput(streamName, chunk);
if (!emitOnly) {
streamArr.push(out.asString);
}
this.emit(symbolProcessOutput, out);
};
const stdOut = [], stdErr = [];
const options = mergeObjects({}, this.options);
options.stdio = 'pipe';
const proc = cp.spawn(this.command, this.args, this.options)
.once('error', err =>
shutdownFunc(new ProcessErrorResult(err)))
.once('exit', (code, sig) =>
shutdownFunc(new ProcessExit(
code !== 0, code, sig, stdOut.join(''), stdErr.join(''))));
this._wasStarted = true;
proc.stdout.on('data', chunk => dataFn('stdout', chunk, stdOut));
proc.stderr.on('data', chunk => dataFn('stderr', chunk, stdErr));
// Expose, after everything is set up:
this._process = proc;
});
};
};
module.exports = Object.freeze({
ProcessResult,
ProcessErrorResult,
ProcessExit,
ProcessOutput,
ProcessWrapper,
symbolProcessOutput
});