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

function encoderForArrayFormat(opts) {
	switch (opts.arrayFormat) {
		case 'index':
			return function (key, value, index) {
				return value === null ? [
					encode(key, opts),
					'[',
					index,
					']'
				].join('') : [
					encode(key, opts),
					'[',
					encode(index, opts),
					']=',
					encode(value, opts)
				].join('');
			};

		case 'bracket':
			return function (key, value) {
				return value === null ? encode(key, opts) : [
					encode(key, opts),
					'[]=',
					encode(value, opts)
				].join('');
			};

		default:
			return function (key, value) {
				return value === null ? encode(key, opts) : [
					encode(key, opts),
					'=',
					encode(value, opts)
				].join('');
			};
	}
}

function parserForArrayFormat(opts) {
	var result;

	switch (opts.arrayFormat) {
		case 'index':
			return function (key, value, accumulator) {
				result = /\[(\d*)\]$/.exec(key);

				key = key.replace(/\[\d*\]$/, '');

				if (!result) {
					accumulator[key] = value;
					return;
				}

				if (accumulator[key] === undefined) {
					accumulator[key] = {};
				}

				accumulator[key][result[1]] = value;
			};

		case 'bracket':
			return function (key, value, accumulator) {
				result = /(\[\])$/.exec(key);
				key = key.replace(/\[\]$/, '');

				if (!result) {
					accumulator[key] = value;
					return;
				} else if (accumulator[key] === undefined) {
					accumulator[key] = [value];
					return;
				}

				accumulator[key] = [].concat(accumulator[key], value);
			};

		default:
			return function (key, value, accumulator) {
				if (accumulator[key] === undefined) {
					accumulator[key] = value;
					return;
				}

				accumulator[key] = [].concat(accumulator[key], value);
			};
	}
}

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

	return value;
}

function keysSorter(input) {
	if (Array.isArray(input)) {
		return input.sort();
	} else if (typeof input === 'object') {
		return keysSorter(Object.keys(input)).sort(function (a, b) {
			return Number(a) - Number(b);
		}).map(function (key) {
			return input[key];
		});
	}

	return input;
}

exports.extract = function (str) {
	var queryStart = str.indexOf('?');
	if (queryStart === -1) {
		return '';
	}
	return str.slice(queryStart + 1);
};

exports.parse = function (str, opts) {
	opts = objectAssign({arrayFormat: 'none'}, opts);

	var formatter = parserForArrayFormat(opts);

	// 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;

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

		formatter(decodeComponent(key), val, ret);
	});

	return Object.keys(ret).sort().reduce(function (result, key) {
		var val = ret[key];
		if (Boolean(val) && typeof val === 'object' && !Array.isArray(val)) {
			// Sort object keys, not values
			result[key] = keysSorter(val);
		} else {
			result[key] = val;
		}

		return result;
	}, Object.create(null));
};

exports.stringify = function (obj, opts) {
	var defaults = {
		encode: true,
		strict: true,
		arrayFormat: 'none'
	};

	opts = objectAssign(defaults, opts);

	var formatter = encoderForArrayFormat(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;
				}

				result.push(formatter(key, val2, result.length));
			});

			return result.join('&');
		}

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