Ocelot-Social/backend/src/schema/resolvers/searches/queryString.js

export function queryString(str) {
  const normalizedString = normalizeWhitespace(str)
  const escapedString = escapeSpecialCharacters(normalizedString)
  return `
${matchWholeText(escapedString)}
${matchEachWordExactly(escapedString)}
${matchSomeWordsExactly(escapedString)}
${matchBeginningOfWords(escapedString)}
`
}

const matchWholeText = (str, boost = 8) => {
  return `"${str}"^${boost}`
}

const matchEachWordExactly = (str, boost = 4) => {
  if (str.includes(' ')) {
    const tmp = str
      .split(' ')
      .map((s, i) => (i === 0 ? `"${s}"` : `AND "${s}"`))
      .join(' ')
    return `(${tmp})^${boost}`
  } else {
    return ''
  }
}

const matchSomeWordsExactly = (str, boost = 2) => {
  if (str.includes(' ')) {
    return str
      .split(' ')
      .map(s => `"${s}"^${boost}`)
      .join(' ')
  } else {
    return ''
  }
}

const matchBeginningOfWords = str => {
  return normalizeWhitespace(
    str
      .split(' ')
      .map(s => {
        if (s.length > 3) {
          // at least 4 letters. So AND, OR and NOT are never used unquoted
          return s + '*'
        } else {
          return ''
        }
      })
      .join(' '),
  )
}

export function normalizeWhitespace(str) {
  return str.replace(/\s+/g, ' ').trim()
}

export function escapeSpecialCharacters(str) {
  return str.replace(/(["[\]&|\\{}+!()^~*?:/-])/g, '\\$1')
}