page-path-builder/index.js

Uses a page.js-style routing string to build up a path you can link to

var parser = require('./path-parser')
var stringifyQuerystring = require('query-string').stringify

module.exports = function(pathStr, parameters) {
	var parsed = typeof pathStr === 'string' ? parser(pathStr) : pathStr
	var allTokens = parsed.allTokens
	var regex = parsed.regex

	if (parameters) {
		var path = allTokens.map(function(bit) {
			if (bit.string) {
				return bit.string
			}

			var defined = typeof parameters[bit.name] !== 'undefined'
			if (!bit.optional && !defined) {
				throw new Error('Must supply argument ' + bit.name + ' for path ' + pathStr)
			}

			return defined ? (bit.delimiter + encodeURIComponent(parameters[bit.name])) : ''
		}).join('')

		if (!regex.test(path)) {
			throw new Error('Provided arguments do not match the original arguments')
		}

		return buildPathWithQuerystring(path, parameters, allTokens)
	} else {
		return parsed
	}
}

function buildPathWithQuerystring(path, parameters, tokenArray) {
	var parametersInQuerystring = getParametersWithoutMatchingToken(parameters, tokenArray)

	if (Object.keys(parametersInQuerystring).length === 0) {
		return path
	}

	return path + '?' + stringifyQuerystring(parametersInQuerystring)
}

function getParametersWithoutMatchingToken(parameters, tokenArray) {
	var tokenHash = tokenArray.reduce(function(memo, bit) {
		if (!bit.string) {
			memo[bit.name] = bit
		}
		return memo
	}, {})

	return Object.keys(parameters).filter(function(param) {
		return !tokenHash[param]
	}).reduce(function(newParameters, param) {
		newParameters[param] = parameters[param]
		return newParameters
	}, {})
}