@zazuko/trifid-plugin-sparql-proxy/lib/ReplaceStream.js

Trifid plugin for sparql-proxy

import { Transform } from 'node:stream'

class ReplaceStream extends Transform {
  constructor(searchStr, replaceStr, options = {}) {
    super(options)
    this.searchStr = searchStr
    this.replaceStr = replaceStr
    this.tailPiece = '' // Holds trailing data from previous chunk
    this.searchStrLen = searchStr.length
  }

  _transform (chunk, encoding, callback) {
    const data = this.tailPiece + chunk.toString() // Combine previous tail with new chunk
    let lastIndex = 0
    let index

    const pieces = []

    // Search for occurrences of searchStr
    while ((index = data.indexOf(this.searchStr, lastIndex)) !== -1) {
      pieces.push(data.slice(lastIndex, index)) // Push the data before the match
      pieces.push(this.replaceStr) // Push the replacement string
      lastIndex = index + this.searchStrLen // Move the index past the match
    }

    // Save the remaining data after the last match as tailPiece
    this.tailPiece = data.slice(lastIndex)

    // Push the processed data
    this.push(pieces.join(''))

    callback()
  }

  _flush (callback) {
    // Push out any remaining data in tailPiece, processing any matches in it
    this.push(this.tailPiece.replace(new RegExp(this.searchStr, 'g'), this.replaceStr))
    callback()
  }
}

export default ReplaceStream