mw-ocg-zimwriter/lib/p.js

Converts mediawiki collection bundles (as generated by mw-ocg-bundler) to ZIM files

// Helpers for promises.
"use strict";
require('es6-shim');
require('prfun');

var spawn = require('child_process').spawn;

var P = module.exports = {};

// My own version of when's nodefn.call with an explicit 'this',
// used for methods
P.call = function(fn, self) {
	var args = Array.prototype.slice.call(arguments, 2);
	var pfn = Promise.promisify(fn, false, self);
	return pfn.apply(self, args);
};

// Returns a promise for completion after spawning `program`
P.spawn = function(program, args, options) {
	return new Promise(function(resolve, reject) {
		spawn(program, args || [], options || { stdio: 'inherit' }).
			on('exit', function(exitCode) {
				if (exitCode === 0) {
					resolve();
				} else {
					reject(new Error(
						program+' '+args.join(' ')+' exited with code '+exitCode
					));
				}
			}).on('error', function(err) {
				reject(err);
			});
	});
};

// Returns a promise for completion after iterating through the given
// array in parallel.  The function should return a promise for each element.
// This is like map but we throw away the results.
// If the optional `p` parameter is provided, wait for that to resolve
// before starting to process the array contents.
P.forEachPar = function(a, f, p) {
	return (p || Promise.resolve()).then(function() {
		return a;
	}).then(function(aResolved) {
		return Promise.all(aResolved.map(f));
	});
};

// Returns a promise for completion after iterating through the given
// array in sequence.  The function should return a promise for each element.
// If the optional `p` parameter is provided, wait for that to resolve
// before starting to process the array contents.
P.forEachSeq = function(a, f, p) {
	// The initial value must not be undefined.  Arbitrarily choose `true`.
	p = p ? p.return(true) : Promise.resolve(true);
	return Promise.reduce(a, function(curResult, value, index, total) {
		/* jshint unused: vars */
		return f.call(null, value, index, null);
	}, p);
};