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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// Copyright Joyent and Node contributors. All rights reserved. MIT license.// deno-lint-ignore-file
import { ERR_METHOD_NOT_IMPLEMENTED } from "../errors.ts";import * as process from "../../_process/process.ts";import Duplex from "./duplex.mjs";
Object.setPrototypeOf(Transform.prototype, Duplex.prototype);Object.setPrototypeOf(Transform, Duplex);
const kCallback = Symbol("kCallback");
function Transform(options) {  if (!(this instanceof Transform)) {    return new Transform(options);  }
  Duplex.call(this, options);
  // We have implemented the _read method, and done the other things  // that Readable wants before the first _read call, so unset the  // sync guard flag.  this._readableState.sync = false;
  this[kCallback] = null;
  if (options) {    if (typeof options.transform === "function") {      this._transform = options.transform;    }
    if (typeof options.flush === "function") {      this._flush = options.flush;    }  }
  // When the writable side finishes, then flush out anything remaining.  // Backwards compat. Some Transform streams incorrectly implement _final  // instead of or in addition to _flush. By using 'prefinish' instead of  // implementing _final we continue supporting this unfortunate use case.  this.on("prefinish", prefinish);}
function final(cb) {  let called = false;  if (typeof this._flush === "function" && !this.destroyed) {    const result = this._flush((er, data) => {      called = true;      if (er) {        if (cb) {          cb(er);        } else {          this.destroy(er);        }        return;      }
      if (data != null) {        this.push(data);      }      this.push(null);      if (cb) {        cb();      }    });    if (result !== undefined && result !== null) {      try {        const then = result.then;        if (typeof then === "function") {          then.call(            result,            (data) => {              if (called) {                return;              }              if (data != null) {                this.push(data);              }              this.push(null);              if (cb) {                process.nextTick(cb);              }            },            (err) => {              if (cb) {                process.nextTick(cb, err);              } else {                process.nextTick(() => this.destroy(err));              }            },          );        }      } catch (err) {        process.nextTick(() => this.destroy(err));      }    }  } else {    this.push(null);    if (cb) {      cb();    }  }}
function prefinish() {  if (this._final !== final) {    final.call(this);  }}
Transform.prototype._final = final;
Transform.prototype._transform = function (chunk, encoding, callback) {  throw new ERR_METHOD_NOT_IMPLEMENTED("_transform()");};
Transform.prototype._write = function (chunk, encoding, callback) {  const rState = this._readableState;  const wState = this._writableState;  const length = rState.length;
  let called = false;  const result = this._transform(chunk, encoding, (err, val) => {    called = true;    if (err) {      callback(err);      return;    }
    if (val != null) {      this.push(val);    }
    if (      wState.ended || // Backwards compat.      length === rState.length || // Backwards compat.      rState.length < rState.highWaterMark ||      rState.length === 0    ) {      callback();    } else {      this[kCallback] = callback;    }  });  if (result !== undefined && result != null) {    try {      const then = result.then;      if (typeof then === "function") {        then.call(          result,          (val) => {            if (called) {              return;            }
            if (val != null) {              this.push(val);            }
            if (              wState.ended ||              length === rState.length ||              rState.length < rState.highWaterMark ||              rState.length === 0            ) {              process.nextTick(callback);            } else {              this[kCallback] = callback;            }          },          (err) => {            process.nextTick(callback, err);          },        );      }    } catch (err) {      process.nextTick(callback, err);    }  }};
Transform.prototype._read = function () {  if (this[kCallback]) {    const callback = this[kCallback];    this[kCallback] = null;    callback();  }};
export default Transform;