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// Copyright Joyent, Inc. and other Node contributors.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to permit
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// persons to whom the Software is furnished to do so, subject to the
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// following conditions:
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//
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// The above copyright notice and this permission notice shall be included
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// in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
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// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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// USE OR OTHER DEALINGS IN THE SOFTWARE.
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// a transform stream is a readable/writable stream where you do
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// something with the data.  Sometimes it's called a "filter",
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// but that's not a great name for it, since that implies a thing where
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// some bits pass through, and others are simply ignored.  (That would
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// be a valid example of a transform, of course.)
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//
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// While the output is causally related to the input, it's not a
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// necessarily symmetric or synchronous transformation.  For example,
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// a zlib stream might take multiple plain-text writes(), and then
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// emit a single compressed chunk some time in the future.
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//
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// Here's how this works:
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//
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// The Transform stream has all the aspects of the readable and writable
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// stream classes.  When you write(chunk), that calls _write(chunk,cb)
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// internally, and returns false if there's a lot of pending writes
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// buffered up.  When you call read(), that calls _read(n) until
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// there's enough pending readable data buffered up.
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//
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// In a transform stream, the written data is placed in a buffer.  When
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// _read(n) is called, it transforms the queued up data, calling the
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// buffered _write cb's as it consumes chunks.  If consuming a single
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// written chunk would result in multiple output chunks, then the first
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// outputted bit calls the readcb, and subsequent chunks just go into
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// the read buffer, and will cause it to emit 'readable' if necessary.
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//
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// This way, back-pressure is actually determined by the reading side,
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// since _read has to be called to start processing a new chunk.  However,
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// a pathological inflate type of transform can cause excessive buffering
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// here.  For example, imagine a stream where every byte of input is
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// interpreted as an integer from 0-255, and then results in that many
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// bytes of output.  Writing the 4 bytes {ff,ff,ff,ff} would result in
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// 1kb of data being output.  In this case, you could write a very small
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// amount of input, and end up with a very large amount of output.  In
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// such a pathological inflating mechanism, there'd be no way to tell
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// the system to stop doing the transform.  A single 4MB write could
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// cause the system to run out of memory.
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//
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// However, even in such a pathological case, only a single written chunk
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// would be consumed, and then the rest would wait (un-transformed) until
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// the results of the previous transformed chunk were consumed.
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'use strict';
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module.exports = Transform;
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var _require$codes = require('../errors').codes,
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    ERR_METHOD_NOT_IMPLEMENTED = _require$codes.ERR_METHOD_NOT_IMPLEMENTED,
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    ERR_MULTIPLE_CALLBACK = _require$codes.ERR_MULTIPLE_CALLBACK,
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    ERR_TRANSFORM_ALREADY_TRANSFORMING = _require$codes.ERR_TRANSFORM_ALREADY_TRANSFORMING,
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    ERR_TRANSFORM_WITH_LENGTH_0 = _require$codes.ERR_TRANSFORM_WITH_LENGTH_0;
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var Duplex = require('./_stream_duplex');
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require('inherits')(Transform, Duplex);
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function afterTransform(er, data) {
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  var ts = this._transformState;
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  ts.transforming = false;
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  var cb = ts.writecb;
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  if (cb === null) {
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    return this.emit('error', new ERR_MULTIPLE_CALLBACK());
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  }
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  ts.writechunk = null;
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  ts.writecb = null;
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  if (data != null) // single equals check for both `null` and `undefined`
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    this.push(data);
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  cb(er);
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  var rs = this._readableState;
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  rs.reading = false;
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  if (rs.needReadable || rs.length < rs.highWaterMark) {
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    this._read(rs.highWaterMark);
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  }
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}
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function Transform(options) {
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  if (!(this instanceof Transform)) return new Transform(options);
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  Duplex.call(this, options);
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  this._transformState = {
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    afterTransform: afterTransform.bind(this),
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    needTransform: false,
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    transforming: false,
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    writecb: null,
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    writechunk: null,
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    writeencoding: null
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  }; // start out asking for a readable event once data is transformed.
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  this._readableState.needReadable = true; // we have implemented the _read method, and done the other things
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  // that Readable wants before the first _read call, so unset the
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  // sync guard flag.
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  this._readableState.sync = false;
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  if (options) {
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    if (typeof options.transform === 'function') this._transform = options.transform;
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    if (typeof options.flush === 'function') this._flush = options.flush;
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  } // When the writable side finishes, then flush out anything remaining.
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  this.on('prefinish', prefinish);
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}
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function prefinish() {
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  var _this = this;
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  if (typeof this._flush === 'function' && !this._readableState.destroyed) {
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    this._flush(function (er, data) {
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      done(_this, er, data);
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    });
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  } else {
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    done(this, null, null);
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  }
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}
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Transform.prototype.push = function (chunk, encoding) {
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  this._transformState.needTransform = false;
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  return Duplex.prototype.push.call(this, chunk, encoding);
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}; // This is the part where you do stuff!
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// override this function in implementation classes.
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// 'chunk' is an input chunk.
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//
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// Call `push(newChunk)` to pass along transformed output
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// to the readable side.  You may call 'push' zero or more times.
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//
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// Call `cb(err)` when you are done with this chunk.  If you pass
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// an error, then that'll put the hurt on the whole operation.  If you
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// never call cb(), then you'll never get another chunk.
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Transform.prototype._transform = function (chunk, encoding, cb) {
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  cb(new ERR_METHOD_NOT_IMPLEMENTED('_transform()'));
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};
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Transform.prototype._write = function (chunk, encoding, cb) {
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  var ts = this._transformState;
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  ts.writecb = cb;
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  ts.writechunk = chunk;
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  ts.writeencoding = encoding;
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  if (!ts.transforming) {
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    var rs = this._readableState;
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    if (ts.needTransform || rs.needReadable || rs.length < rs.highWaterMark) this._read(rs.highWaterMark);
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  }
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}; // Doesn't matter what the args are here.
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// _transform does all the work.
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// That we got here means that the readable side wants more data.
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Transform.prototype._read = function (n) {
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  var ts = this._transformState;
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  if (ts.writechunk !== null && !ts.transforming) {
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    ts.transforming = true;
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    this._transform(ts.writechunk, ts.writeencoding, ts.afterTransform);
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  } else {
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    // mark that we need a transform, so that any data that comes in
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    // will get processed, now that we've asked for it.
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    ts.needTransform = true;
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  }
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};
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Transform.prototype._destroy = function (err, cb) {
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  Duplex.prototype._destroy.call(this, err, function (err2) {
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    cb(err2);
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  });
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};
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function done(stream, er, data) {
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  if (er) return stream.emit('error', er);
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  if (data != null) // single equals check for both `null` and `undefined`
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    stream.push(data); // TODO(BridgeAR): Write a test for these two error cases
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  // if there's nothing in the write buffer, then that means
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  // that nothing more will ever be provided
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  if (stream._writableState.length) throw new ERR_TRANSFORM_WITH_LENGTH_0();
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  if (stream._transformState.transforming) throw new ERR_TRANSFORM_ALREADY_TRANSFORMING();
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  return stream.push(null);
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}