'use strict';
const strictUriEncode = require('strict-uri-encode');
const decodeComponent = require('decode-uri-component');
const splitOnFirst = require('split-on-first');
const filterObject = require('filter-obj');

const isNullOrUndefined = value => value === null || value === undefined;

function encoderForArrayFormat(options) {
	switch (options.arrayFormat) {
		case 'index':
			return key => (result, value) => {
				const index = result.length;

				if (
					value === undefined ||
					(options.skipNull && value === null) ||
					(options.skipEmptyString && value === '')
				) {
					return result;
				}

				if (value === null) {
					return [...result, [encode(key, options), '[', index, ']'].join('')];
				}

				return [
					...result,
					[encode(key, options), '[', encode(index, options), ']=', encode(value, options)].join('')
				];
			};

		case 'bracket':
			return key => (result, value) => {
				if (
					value === undefined ||
					(options.skipNull && value === null) ||
					(options.skipEmptyString && value === '')
				) {
					return result;
				}

				if (value === null) {
					return [...result, [encode(key, options), '[]'].join('')];
				}

				return [...result, [encode(key, options), '[]=', encode(value, options)].join('')];
			};

		case 'comma':
		case 'separator':
			return key => (result, value) => {
				if (value === null || value === undefined || value.length === 0) {
					return result;
				}

				if (result.length === 0) {
					return [[encode(key, options), '=', encode(value, options)].join('')];
				}

				return [[result, encode(value, options)].join(options.arrayFormatSeparator)];
			};

		default:
			return key => (result, value) => {
				if (
					value === undefined ||
					(options.skipNull && value === null) ||
					(options.skipEmptyString && value === '')
				) {
					return result;
				}

				if (value === null) {
					return [...result, encode(key, options)];
				}

				return [...result, [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);
			};

		case 'comma':
		case 'separator':
			return (key, value, accumulator) => {
				const isArray = typeof value === 'string' && value.includes(options.arrayFormatSeparator);
				const isEncodedArray = (typeof value === 'string' && !isArray && decode(value, options).includes(options.arrayFormatSeparator));
				value = isEncodedArray ? decode(value, options) : value;
				const newValue = isArray || isEncodedArray ? value.split(options.arrayFormatSeparator).map(item => decode(item, options)) : value === null ? value : decode(value, options);
				accumulator[key] = newValue;
			};

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

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

function validateArrayFormatSeparator(value) {
	if (typeof value !== 'string' || value.length !== 1) {
		throw new TypeError('arrayFormatSeparator must be single character string');
	}
}

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

	return input;
}

function getHash(url) {
	let hash = '';
	const hashStart = url.indexOf('#');
	if (hashStart !== -1) {
		hash = url.slice(hashStart);
	}

	return hash;
}

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

	return input.slice(queryStart + 1);
}

function parseValue(value, options) {
	if (options.parseNumbers && !Number.isNaN(Number(value)) && (typeof value === 'string' && value.trim() !== '')) {
		value = Number(value);
	} else if (options.parseBooleans && value !== null && (value.toLowerCase() === 'true' || value.toLowerCase() === 'false')) {
		value = value.toLowerCase() === 'true';
	}

	return value;
}

function parse(query, options) {
	options = Object.assign({
		decode: true,
		sort: true,
		arrayFormat: 'none',
		arrayFormatSeparator: ',',
		parseNumbers: false,
		parseBooleans: false
	}, options);

	validateArrayFormatSeparator(options.arrayFormatSeparator);

	const formatter = parserForArrayFormat(options);

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

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

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

	if (!query) {
		return ret;
	}

	for (const param of query.split('&')) {
		if (param === '') {
			continue;
		}

		let [key, value] = splitOnFirst(options.decode ? param.replace(/\+/g, ' ') : param, '=');

		// Missing `=` should be `null`:
		// http://w3.org/TR/2012/WD-url-20120524/#collect-url-parameters
		value = value === undefined ? null : ['comma', 'separator'].includes(options.arrayFormat) ? value : decode(value, options);
		formatter(decode(key, options), value, ret);
	}

	for (const key of Object.keys(ret)) {
		const value = ret[key];
		if (typeof value === 'object' && value !== null) {
			for (const k of Object.keys(value)) {
				value[k] = parseValue(value[k], options);
			}
		} else {
			ret[key] = parseValue(value, options);
		}
	}

	if (options.sort === false) {
		return ret;
	}

	return (options.sort === true ? Object.keys(ret).sort() : Object.keys(ret).sort(options.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 = (object, options) => {
	if (!object) {
		return '';
	}

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

	validateArrayFormatSeparator(options.arrayFormatSeparator);

	const shouldFilter = key => (
		(options.skipNull && isNullOrUndefined(object[key])) ||
		(options.skipEmptyString && object[key] === '')
	);

	const formatter = encoderForArrayFormat(options);

	const objectCopy = {};

	for (const key of Object.keys(object)) {
		if (!shouldFilter(key)) {
			objectCopy[key] = object[key];
		}
	}

	const keys = Object.keys(objectCopy);

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

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

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

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

		if (Array.isArray(value)) {
			return value
				.reduce(formatter(key), [])
				.join('&');
		}

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

exports.parseUrl = (url, options) => {
	options = Object.assign({
		decode: true
	}, options);

	const [url_, hash] = splitOnFirst(url, '#');

	return Object.assign(
		{
			url: url_.split('?')[0] || '',
			query: parse(extract(url), options)
		},
		options && options.parseFragmentIdentifier && hash ? {fragmentIdentifier: decode(hash, options)} : {}
	);
};

exports.stringifyUrl = (object, options) => {
	options = Object.assign({
		encode: true,
		strict: true
	}, options);

	const url = removeHash(object.url).split('?')[0] || '';
	const queryFromUrl = exports.extract(object.url);
	const parsedQueryFromUrl = exports.parse(queryFromUrl, {sort: false});

	const query = Object.assign(parsedQueryFromUrl, object.query);
	let queryString = exports.stringify(query, options);
	if (queryString) {
		queryString = `?${queryString}`;
	}

	let hash = getHash(object.url);
	if (object.fragmentIdentifier) {
		hash = `#${encode(object.fragmentIdentifier, options)}`;
	}

	return `${url}${queryString}${hash}`;
};

exports.pick = (input, filter, options) => {
	options = Object.assign({
		parseFragmentIdentifier: true
	}, options);

	const {url, query, fragmentIdentifier} = exports.parseUrl(input, options);
	return exports.stringifyUrl({
		url,
		query: filterObject(query, filter),
		fragmentIdentifier
	}, options);
};

exports.exclude = (input, filter, options) => {
	const exclusionFilter = Array.isArray(filter) ? key => !filter.includes(key) : (key, value) => !filter(key, value);

	return exports.pick(input, exclusionFilter, options);
};