'use strict';
var strictUriEncode = require('strict-uri-encode');
var objectAssign = require('object-assign');

function encode(value, opts) {
	if (opts.encode) {
		return opts.strict ? strictUriEncode(value) : encodeURIComponent(value);
	}

	return value;
}

exports.extract = function (str) {
	return str.split('?')[1] || '';
};

exports.parse = function (str) {
	// Create an object with no prototype
	// https://github.com/sindresorhus/query-string/issues/47
	var ret = Object.create(null);

	if (typeof str !== 'string') {
		return ret;
	}

	str = str.trim().replace(/^(\?|#|&)/, '');

	if (!str) {
		return ret;
	}

	str.split('&').forEach(function (param) {
		var parts = param.replace(/\+/g, ' ').split('=');
		// Firefox (pre 40) decodes `%3D` to `=`
		// https://github.com/sindresorhus/query-string/pull/37
		var key = parts.shift();
		var val = parts.length > 0 ? parts.join('=') : undefined;

		key = decodeURIComponent(key);

		// missing `=` should be `null`:
		// http://w3.org/TR/2012/WD-url-20120524/#collect-url-parameters
		val = val === undefined ? null : decodeURIComponent(val);

		if (ret[key] === undefined) {
			ret[key] = val;
		} else if (Array.isArray(ret[key])) {
			ret[key].push(val);
		} else {
			ret[key] = [ret[key], val];
		}
	});

	return ret;
};

exports.stringify = function (obj, opts) {
	var defaults = {
		encode: true,
		strict: true
	};

	opts = objectAssign(defaults, opts);

	return obj ? Object.keys(obj).sort().map(function (key) {
		var val = obj[key];

		if (val === undefined) {
			return '';
		}

		if (val === null) {
			return encode(key, opts);
		}

		if (Array.isArray(val)) {
			var result = [];

			val.slice().forEach(function (val2) {
				if (val2 === undefined) {
					return;
				}

				if (val2 === null) {
					result.push(encode(key, opts));
				} else {
					result.push(encode(key, opts) + '=' + encode(val2, opts));
				}
			});

			return result.join('&');
		}

		return encode(key, opts) + '=' + encode(val, opts);
	}).filter(function (x) {
		return x.length > 0;
	}).join('&') : '';
};