/**
 * Query helper utility class
 *
 * *Note: This class contains static members only!*
 */
class Query {
  /**
   * checks if two querys are equal
   *
   * @param {object} query1
   * @param {object} query2
   * @return {boolean}
   * @category Query
   */
  static isEqual(query1, query2) {
    return JSON.stringify(query1) === JSON.stringify(query2)
  }

  /**
   * Creates a deep copy from a query.
   *
   * @param {object} query
   */
  static copy(query) {
    return JSON.parse(JSON.stringify(query || {}))
  }

  /**
   * Merges multiple queries together to one single query (deep copy included).
   *
   * *Please note that the value on the last parameter has the highest precedence.*
   *
   * @param {*} queries
   */
  static merge(...queries) {
    const newQuery = {}
    const queryFunctions = []
    queries.forEach(query => {
      if (typeof query === 'function') {
        queryFunctions.push(query)
        return
      }
      Object.entries(query).forEach(([key, value]) => {
        if (newQuery[key]) {
          if (key === '$or') {
            if (!newQuery.$and) newQuery.$and = []
            newQuery.$and.push({ $or: Query.copy(value) })
          } else if (key === '$and') {
            newQuery.$and = newQuery.$and.concat(Query.copy(value))
          } else if (typeof newQuery[key] === 'object') {
            newQuery[key] = Query.merge(newQuery[key], value)
          } else {
            newQuery[key] = value
          }
        } else {
          newQuery[key] = Query.copy(value)
        }
      })
    })

    if (queryFunctions.length === 0) return newQuery
    return () =>
      Query.merge(
        newQuery,
        ...queryFunctions.map(queryFunction => queryFunction())
      )
  }

  /**
   * Builds a query string for use with a server request.
   *
   * Parses a query such that the backend understands it
   *
   * @param {object} query
   */
  static buildQueryString(query) {
    const parsedQuery = new URLSearchParams()

    Object.keys(query).forEach(key => {
      let value = null
      if (Array.isArray(query[key])) {
        if (key === 'sort') {
          value = query[key].join(',')
        } else {
          value = query[key]
        }
      } else {
        value = JSON.stringify(query[key])
      }
      parsedQuery.set(key, value)
    })
    return parsedQuery.toString()
  }
}

export default Query