/*
 * Copyright (c) 2011-2017 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 * which is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 */

package io.vertx.core.http.impl;

import io.vertx.core.Handler;
import io.vertx.core.Vertx;
import io.vertx.core.buffer.Buffer;
import io.vertx.core.file.AsyncFile;
import io.vertx.core.file.OpenOptions;
import io.vertx.core.http.HttpServerFileUpload;
import io.vertx.core.http.HttpServerRequest;
import io.vertx.core.streams.Pump;

import java.nio.charset.Charset;

/**
 * This class is optimised for performance when used on the same event loop that is was passed to the handler with.
 * However it can be used safely from other threads.
 *
 * The internal state is protected using the synchronized keyword. If always used on the same event loop, then
 * we benefit from biased locking which makes the overhead of synchronized near zero.
 *
 * @author <a href="mailto:nmaurer@redhat.com">Norman Maurer</a>
 */
class HttpServerFileUploadImpl implements HttpServerFileUpload {

  private final HttpServerRequest req;
  private final Vertx vertx;
  private final String name;
  private final String filename;
  private final String contentType;
  private final String contentTransferEncoding;
  private final Charset charset;

  private Handler<Buffer> dataHandler;
  private Handler<Void> endHandler;
  private AsyncFile file;
  private Handler<Throwable> exceptionHandler;

  private long size;
  private boolean paused;
  private Buffer pauseBuff;
  private boolean complete;
  private boolean lazyCalculateSize;

  HttpServerFileUploadImpl(Vertx vertx, HttpServerRequest req, String name, String filename, String contentType,
                           String contentTransferEncoding,
                           Charset charset, long size) {
    this.vertx = vertx;
    this.req = req;
    this.name = name;
    this.filename = filename;
    this.contentType = contentType;
    this.contentTransferEncoding = contentTransferEncoding;
    this.charset = charset;
    this.size = size;
    if (size == 0) {
      lazyCalculateSize = true;
    }
  }

  @Override
  public String filename() {
    return filename;
  }

  @Override
  public String name() {
    return name;
  }

  @Override
  public String contentType() {
    return contentType;
  }

  @Override
  public String contentTransferEncoding() {
    return contentTransferEncoding;
  }

  @Override
  public String charset() {
    return charset.toString();
  }

  @Override
  public synchronized long size() {
    return size;
  }

  @Override
  public synchronized HttpServerFileUpload handler(Handler<Buffer> handler) {
    this.dataHandler = handler;
    return this;
  }

  @Override
  public synchronized HttpServerFileUpload pause() {
    req.pause();
    paused = true;
    return this;
  }

  @Override
  public synchronized HttpServerFileUpload resume() {
    if (paused) {
      req.resume();
      paused = false;
      if (pauseBuff != null) {
        doReceiveData(pauseBuff);
        pauseBuff = null;
      }
      if (complete) {
        handleComplete();
      }
    }
    return this;
  }

  @Override
  public synchronized HttpServerFileUpload exceptionHandler(Handler<Throwable> exceptionHandler) {
    this.exceptionHandler = exceptionHandler;
    return this;
  }

  @Override
  public synchronized HttpServerFileUpload endHandler(Handler<Void> handler) {
    this.endHandler = handler;
    return this;
  }

  @Override
  public HttpServerFileUpload streamToFileSystem(String filename) {
    pause();
    vertx.fileSystem().open(filename, new OpenOptions(), ar -> {
      if (ar.succeeded()) {
        file =  ar.result();
        Pump p = Pump.pump(HttpServerFileUploadImpl.this, ar.result());
        p.start();
        resume();
      } else {
        notifyExceptionHandler(ar.cause());
      }
    });
    return this;
  }

  @Override
  public synchronized boolean isSizeAvailable() {
    return !lazyCalculateSize;
  }

  synchronized void receiveData(Buffer data) {
    if (data.length() != 0) {
      // Can sometimes receive zero length packets from Netty!
      if (lazyCalculateSize) {
        size += data.length();
      }
      doReceiveData(data);
    }
  }

  synchronized void doReceiveData(Buffer data) {
    if (!paused) {
      if (dataHandler != null) {
        dataHandler.handle(data);
      }
    } else {
      if (pauseBuff == null) {
        pauseBuff = Buffer.buffer();
      }
      pauseBuff.appendBuffer(data);
    }
  }

  synchronized void complete() {
    if (paused) {
      complete = true;
    } else {
      handleComplete();
    }
  }

  private void handleComplete() {
    lazyCalculateSize = false;
    if (file == null) {
      notifyEndHandler();
    } else {
      file.close(ar -> {
        if (ar.failed()) {
          notifyExceptionHandler(ar.cause());
        }
        notifyEndHandler();
      });
    }
  }

  private void notifyEndHandler() {
    if (endHandler != null) {
      endHandler.handle(null);
    }
  }

  private void notifyExceptionHandler(Throwable cause) {
    if (exceptionHandler != null) {
      exceptionHandler.handle(cause);
    }
  }
}
