'use strict';
const strictUriEncode = require('strict-uri-encode');
const decodeComponent = require('decode-uri-component');

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

function parserForArrayFormat(options) {
	let result;

	switch (options.arrayFormat) {
		case 'index':
			return (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 (key, value, accumulator) => {
				result = /(\[\])$/.exec(key);
				key = key.replace(/\[\]$/, '');

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

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

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

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

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

	return value;
}

function decode(value, options) {
	if (options.decode) {
		return decodeComponent(value);
	}

	return value;
}

function keysSorter(input) {
	if (Array.isArray(input)) {
		return input.sort();
	}

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

	return input;
}

function extract(input) {
	const queryStart = input.indexOf('?');
	if (queryStart === -1) {
		return '';
	}

	return input.slice(queryStart + 1);
}

function parse(input, options) {
	options = Object.assign({decode: true, arrayFormat: 'none'}, options);

	const formatter = parserForArrayFormat(options);

	// Create an object with no prototype
	const ret = Object.create(null);

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

	input = input.trim().replace(/^[?#&]/, '');

	if (!input) {
		return ret;
	}

	for (const param of input.split('&')) {
		let [key, value] = param.replace(/\+/g, ' ').split('=');

		// Missing `=` should be `null`:
		// http://w3.org/TR/2012/WD-url-20120524/#collect-url-parameters
		value = value === undefined ? null : decode(value, options);

		formatter(decode(key, options), value, ret);
	}

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

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

exports.extract = extract;
exports.parse = parse;

exports.stringify = (obj, options) => {
	if (!obj) {
		return '';
	}

	options = Object.assign({
		encode: true,
		strict: true,
		arrayFormat: 'none'
	}, options);

	const formatter = encoderForArrayFormat(options);
	const keys = Object.keys(obj);

	if (options.sort !== false) {
		keys.sort(options.sort);
	}

	return keys.map(key => {
		const value = obj[key];

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

		if (value === null) {
			return encode(key, options);
		}

		if (Array.isArray(value)) {
			const result = [];

			for (const value2 of value.slice()) {
				if (value2 === undefined) {
					continue;
				}

				result.push(formatter(key, value2, result.length));
			}

			return result.join('&');
		}

		return encode(key, options) + '=' + encode(value, options);
	}).filter(x => x.length > 0).join('&');
};

exports.parseUrl = (input, options) => {
	const hashStart = input.indexOf('#');
	if (hashStart !== -1) {
		input = input.slice(0, hashStart);
	}

	return {
		url: input.split('?')[0] || '',
		query: parse(extract(input), options)
	};
};