const { Transform } = require('stream')

// A stream that converts database objects stream to "{id}\t{data_json}\n" stream or a json stream of obj.data fields

class SpeckleObjectsStream extends Transform {
  constructor(simpleText) {
    super({ writableObjectMode: true })
    this.simpleText = simpleText

    if (!this.simpleText) this.push('[')
    this.isFirstObject = true
  }

  _transform(dbObj, encoding, callback) {
    let objData = dbObj.dataText
    if (objData === undefined) objData = JSON.stringify(dbObj.data)

    try {
      if (this.simpleText) {
        this.push(`${dbObj.id}\t`)
        this.push(objData)
        this.push('\n')
      } else {
        // JSON output
        if (!this.isFirstObject) this.push(',')
        this.push(objData)
        this.isFirstObject = false
      }
      callback()
    } catch (e) {
      callback(e)
    }
  }

  _flush(callback) {
    if (!this.simpleText) this.push(']')
    callback()
  }
}

exports.SpeckleObjectsStream = SpeckleObjectsStream