type ParsedUrlQueryInput = NodeJS.Dict<string | number | boolean | ReadonlyArray<string> | ReadonlyArray<number> | ReadonlyArray<boolean> | null>

const isObject = (value: any): value is object => {
	const type = typeof value
	return value != null && (type == 'object' || type == 'function')
}

const queryForm =
  (name: string,
   value: string | number | Array<string | number> | { [key: string]: string | number },
   explode: boolean): ParsedUrlQueryInput => {
    if (Array.isArray(value)) {
      if (explode) {
        return {[name]: value.map(String)}
      } else {
        return {[name]: value.join(',')}
      }
    } else if (isObject(value)) {
      if (explode) {
        return value;
      } else {
        return {[name]: Object.entries(value).map((prop: [string, string | number]) => prop.join(',')).join(',')}
      }
    } else {
      return {[name]: value};
    }
  }

const querySpaceDelimited =
  (name: string,
   value: string | number | Array<string | number> | { [key: string]: string | number }): ParsedUrlQueryInput => {
    if (Array.isArray(value)) {
      return {[name]: value.join(' ')}
    } else if (isObject(value)) {
      return {[name]: Object.entries(value).map((prop: [string, string | number]) => prop.join(' ')).join(' ')}
    }
    throw new Error(`Unsupported value: ${name}`);
  }

const queryPipeDelimited =
  (name: string,
   value: string | number | Array<string | number> | { [key: string]: string | number }): ParsedUrlQueryInput => {
    if (Array.isArray(value)) {
      return {[name]: value.join('|')}
    } else if (isObject(value)) {
      return {[name]: Object.entries(value).map((prop: [string, string | number]) => prop.join('|')).join('|')}
    }
    throw new Error(`Unsupported value: ${name}`);
  }

const queryDeepObject =
  (name: string,
   value: string | number | Array<string | number> | { [key: string]: string | number }): ParsedUrlQueryInput => {
    if (!Array.isArray(value) && isObject(value)) {
      return Object.keys(value).reduce((pre, cur) => ({...pre, [`${name}[${cur}]`]: value[cur]}), {});
    }
    throw new Error(`Unsupported value: ${name}`);
  }

export const query =
  (
    name: string,
    value: undefined | string | number | Array<string | number> | { [key: string]: string | number },
    style: 'form' | 'spaceDelimited' | 'pipeDelimited' | 'deepObject',
    explode: boolean): ParsedUrlQueryInput => {
    if (value === undefined) return {};
    switch (style) {
      case 'form':
        return queryForm(name, value, explode);
      case 'spaceDelimited':
        return querySpaceDelimited(name, value);
      case 'pipeDelimited':
        return queryPipeDelimited(name, value);
      case 'deepObject':
        return queryDeepObject(name, value);
      default:
        throw new Error(`Unsupported style: ${style}`);
    }
  }