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// Copyright Node.js contributors. All rights reserved. MIT License.import { Encodings } from "../_utils.ts";import Duplex from "./duplex.ts";import type { DuplexOptions } from "./duplex.ts";import type { writeV } from "./writable_internal.ts";import { ERR_METHOD_NOT_IMPLEMENTED } from "../_errors.ts";
const kCallback = Symbol("kCallback");
type TransformFlush = (  this: Transform,  // deno-lint-ignore no-explicit-any  callback: (error?: Error | null, data?: any) => void,) => void;
export interface TransformOptions extends DuplexOptions {  read?(this: Transform, size: number): void;  write?(    this: Transform,    // deno-lint-ignore no-explicit-any    chunk: any,    encoding: Encodings,    callback: (error?: Error | null) => void,  ): void;  writev?: writeV;  final?(this: Transform, callback: (error?: Error | null) => void): void;  destroy?(    this: Transform,    error: Error | null,    callback: (error: Error | null) => void,  ): void;  transform?(    this: Transform,    // deno-lint-ignore no-explicit-any    chunk: any,    encoding: Encodings,    // deno-lint-ignore no-explicit-any    callback: (error?: Error | null, data?: any) => void,  ): void;  flush?: TransformFlush;}
export default class Transform extends Duplex {  [kCallback]: null | ((error?: Error | null) => void);  _flush?: TransformFlush;
  constructor(options?: TransformOptions) {    super(options);    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;      }    }
    this.on("prefinish", function (this: Transform) {      if (typeof this._flush === "function" && !this.destroyed) {        this._flush((er, data) => {          if (er) {            this.destroy(er);            return;          }
          if (data != null) {            this.push(data);          }          this.push(null);        });      } else {        this.push(null);      }    });  }
  _read = () => {    if (this[kCallback]) {      const callback = this[kCallback] as (error?: Error | null) => void;      this[kCallback] = null;      callback();    }  };
  _transform(    // deno-lint-ignore no-explicit-any    _chunk: any,    _encoding: string,    // deno-lint-ignore no-explicit-any    _callback: (error?: Error | null, data?: any) => void,  ) {    throw new ERR_METHOD_NOT_IMPLEMENTED("_transform()");  }
  _write = (    // deno-lint-ignore no-explicit-any    chunk: any,    encoding: string,    callback: (error?: Error | null) => void,  ) => {    const rState = this._readableState;    const wState = this._writableState;    const length = rState.length;
    this._transform(chunk, encoding, (err, val) => {      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;      }    });  };}