/*
 * Copyright 2014 Red Hat, Inc.
 *
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  and Apache License v2.0 which accompanies this distribution.
 *
 *  The Eclipse Public License is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 *
 *  The Apache License v2.0 is available at
 *  http://www.opensource.org/licenses/apache2.0.php
 *
 *  You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.ext.web.sstore.impl;

import io.vertx.core.VertxException;
import io.vertx.core.buffer.Buffer;
import io.vertx.core.shareddata.Shareable;
import io.vertx.core.shareddata.impl.ClusterSerializable;
import io.vertx.ext.web.Session;
import io.vertx.ext.web.impl.Utils;

import java.io.*;
import java.nio.charset.Charset;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @author <a href="http://tfox.org">Tim Fox</a>
 */
public class SessionImpl implements Session, ClusterSerializable, Shareable {

  private static final Charset UTF8 = Charset.forName("UTF-8");
  private static final char[] HEX = "0123456789abcdef".toCharArray();

  private static final byte TYPE_LONG = 1;
  private static final byte TYPE_INT = 2;
  private static final byte TYPE_SHORT = 3;
  private static final byte TYPE_BYTE = 4;
  private static final byte TYPE_DOUBLE = 5;
  private static final byte TYPE_FLOAT = 6;
  private static final byte TYPE_CHAR = 7;
  private static final byte TYPE_BOOLEAN = 8;
  private static final byte TYPE_STRING = 9;
  private static final byte TYPE_BUFFER = 10;
  private static final byte TYPE_BYTES = 11;
  private static final byte TYPE_SERIALIZABLE = 12;
  private static final byte TYPE_CLUSTER_SERIALIZABLE = 13;

  private final PRNG prng;

  private String id;
  private long timeout;
  private volatile Map<String, Object> data;
  private long lastAccessed;
  private int version;
  // state management
  private boolean destroyed;
  private boolean renewed;
  private String oldId;

  public SessionImpl(PRNG random) {
    this.prng = random;
  }

  public SessionImpl(PRNG random, long timeout, int length) {
    this.prng = random;
    this.id = generateId(prng, length);
    this.timeout = timeout;
    this.lastAccessed = System.currentTimeMillis();
  }

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

  @Override
  public Session regenerateId() {
    if (oldId == null) {
      // keep track of just the first one since the
      // regeneration during the remaining lifecycle are ephemeral
      oldId = id;
    }
    // ids are stored in hex, so the original size is half of the hex encodec length
    id = generateId(prng, oldId.length() / 2);
    renewed = true;
    return this;
  }

  @Override
  public long timeout() {
    return timeout;
  }

  @Override
  @SuppressWarnings("unchecked")
  public <T> T get(String key) {
    Object obj = getData().get(key);
    return (T) obj;
  }

  @Override
  public Session put(String key, Object obj) {
    final Map<String, Object> data = getData();
    // nulls are handled as remove actions
    if (obj == null) {
      data.remove(key);
    } else {
      data.put(key, obj);
    }
    return this;
  }

  @Override
  @SuppressWarnings("unchecked")
  public <T> T remove(String key) {
    Object obj = getData().remove(key);
    return (T) obj;
  }

  @Override
  public Map<String, Object> data() {
    return getData();
  }

  @Override
  public long lastAccessed() {
    return lastAccessed;
  }

  @Override
  public void setAccessed() {
    this.lastAccessed = System.currentTimeMillis();
  }

  @Override
  public void destroy() {
    synchronized (this) {
      destroyed = true;
      data = null;
    }
  }

  @Override
  public boolean isDestroyed() {
    return destroyed;
  }

  @Override
  public boolean isRegenerated() {
    return renewed;
  }

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

  public int version() {
    return version;
  }

  public void incrementVersion() {
    ++version;
  }

  @Override
  public void writeToBuffer(Buffer buff) {
    byte[] bytes = id.getBytes(UTF8);
    buff.appendInt(bytes.length).appendBytes(bytes);
    buff.appendLong(timeout);
    buff.appendLong(lastAccessed);
    buff.appendInt(version);
    Buffer dataBuf = writeDataToBuffer();
    buff.appendBuffer(dataBuf);
  }

  @Override
  public int readFromBuffer(int pos, Buffer buffer) {
    int len = buffer.getInt(pos);
    pos += 4;
    byte[] bytes = buffer.getBytes(pos, pos + len);
    pos += len;
    id = new String(bytes, UTF8);
    timeout = buffer.getLong(pos);
    pos += 8;
    lastAccessed = buffer.getLong(pos);
    pos += 8;
    version = buffer.getInt(pos);
    pos += 4;
    pos = readDataFromBuffer(pos, buffer);
    return pos;
  }

  private Map<String, Object> getData() {
    if (data == null) {
      synchronized (this) {
        // double check since there could already been someone in the lock
        if (data == null) {
          data = new ConcurrentHashMap<>();
          if (destroyed) {
            // pretty much should behave as a regeneration
            regenerateId();
            destroyed = false;
          }
        }
      }
    }
    return data;
  }

  private Buffer writeDataToBuffer() {
    try {
      Buffer buffer = Buffer.buffer();
      if (data == null) {
        buffer.appendInt(0);
      } else {
        buffer.appendInt(data.size());
        for (Map.Entry<String, Object> entry : data.entrySet()) {
          String key = entry.getKey();
          byte[] keyBytes = key.getBytes(UTF8);
          buffer.appendInt(keyBytes.length).appendBytes(keyBytes);
          Object val = entry.getValue();
          if (val instanceof Long) {
            buffer.appendByte(TYPE_LONG).appendLong((long) val);
          } else if (val instanceof Integer) {
            buffer.appendByte(TYPE_INT).appendInt((int) val);
          } else if (val instanceof Short) {
            buffer.appendByte(TYPE_SHORT).appendShort((short) val);
          } else if (val instanceof Byte) {
            buffer.appendByte(TYPE_BYTE).appendByte((byte) val);
          } else if (val instanceof Double) {
            buffer.appendByte(TYPE_DOUBLE).appendDouble((double) val);
          } else if (val instanceof Float) {
            buffer.appendByte(TYPE_FLOAT).appendFloat((float) val);
          } else if (val instanceof Character) {
            buffer.appendByte(TYPE_CHAR).appendShort((short) ((Character) val).charValue());
          } else if (val instanceof Boolean) {
            buffer.appendByte(TYPE_BOOLEAN).appendByte((byte) ((boolean) val ? 1 : 0));
          } else if (val instanceof String) {
            byte[] bytes = ((String) val).getBytes(UTF8);
            buffer.appendByte(TYPE_STRING).appendInt(bytes.length).appendBytes(bytes);
          } else if (val instanceof Buffer) {
            Buffer buff = (Buffer) val;
            buffer.appendByte(TYPE_BUFFER).appendInt(buff.length()).appendBuffer(buff);
          } else if (val instanceof byte[]) {
            byte[] bytes = (byte[]) val;
            buffer.appendByte(TYPE_BYTES).appendInt(bytes.length).appendBytes(bytes);
          } else if (val instanceof Serializable) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(baos));
            oos.writeObject(val);
            oos.flush();
            byte[] bytes = baos.toByteArray();
            buffer.appendByte(TYPE_SERIALIZABLE).appendInt(bytes.length).appendBytes(bytes);
          } else if (val instanceof ClusterSerializable) {
            buffer.appendByte(TYPE_CLUSTER_SERIALIZABLE);
            String className = val.getClass().getName();
            byte[] classNameBytes = className.getBytes(UTF8);
            buffer.appendInt(classNameBytes.length).appendBytes(classNameBytes);
            ((ClusterSerializable) val).writeToBuffer(buffer);
          } else {
            if (val != null) {
              throw new IllegalStateException("Invalid type for data in session: " + val.getClass());
            }
          }
        }
      }
      return buffer;
    } catch (IOException e) {
      throw new VertxException(e);
    }
  }

  private int readDataFromBuffer(int pos, Buffer buffer) {
    try {
      int entries = buffer.getInt(pos);
      pos += 4;
      if (entries != 0) {
        data = new ConcurrentHashMap<>(entries);
        for (int i = 0; i < entries; i++) {
          int keylen = buffer.getInt(pos);
          pos += 4;
          byte[] keyBytes = buffer.getBytes(pos, pos + keylen);
          pos += keylen;
          String key = new String(keyBytes, UTF8);
          byte type = buffer.getByte(pos++);
          Object val;
          switch (type) {
            case TYPE_LONG:
              val = buffer.getLong(pos);
              pos += 8;
              break;
            case TYPE_INT:
              val = buffer.getInt(pos);
              pos += 4;
              break;
            case TYPE_SHORT:
              val = buffer.getShort(pos);
              pos += 2;
              break;
            case TYPE_BYTE:
              val = buffer.getByte(pos);
              pos++;
              break;
            case TYPE_FLOAT:
              val = buffer.getFloat(pos);
              pos += 4;
              break;
            case TYPE_DOUBLE:
              val = buffer.getDouble(pos);
              pos += 8;
              break;
            case TYPE_CHAR:
              short s = buffer.getShort(pos);
              pos += 2;
              val = (char) s;
              break;
            case TYPE_BOOLEAN:
              byte b = buffer.getByte(pos);
              pos++;
              val = b == 1;
              break;
            case TYPE_STRING:
              int len = buffer.getInt(pos);
              pos += 4;
              byte[] bytes = buffer.getBytes(pos, pos + len);
              val = new String(bytes, UTF8);
              pos += len;
              break;
            case TYPE_BUFFER:
              len = buffer.getInt(pos);
              pos += 4;
              bytes = buffer.getBytes(pos, pos + len);
              val = Buffer.buffer(bytes);
              pos += len;
              break;
            case TYPE_BYTES:
              len = buffer.getInt(pos);
              pos += 4;
              val = buffer.getBytes(pos, pos + len);
              pos += len;
              break;
            case TYPE_SERIALIZABLE:
              len = buffer.getInt(pos);
              pos += 4;
              bytes = buffer.getBytes(pos, pos + len);
              ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
              ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(bais));
              val = ois.readObject();
              pos += len;
              break;
            case TYPE_CLUSTER_SERIALIZABLE:
              int classNameLen = buffer.getInt(pos);
              pos += 4;
              byte[] classNameBytes = buffer.getBytes(pos, pos + classNameLen);
              pos += classNameLen;
              String className = new String(classNameBytes, UTF8);
              Class clazz = Utils.getClassLoader().loadClass(className);
              ClusterSerializable obj = (ClusterSerializable) clazz.newInstance();
              pos = obj.readFromBuffer(pos, buffer);
              val = obj;
              break;
            default:
              throw new IllegalStateException("Invalid serialized type: " + type);
          }
          data.put(key, val);
        }
      }
      return pos;
    } catch (Exception e) {
      throw new VertxException(e);
    }
  }

  private static String generateId(PRNG rng, int length) {
    final byte[] bytes = new byte[length];
    rng.nextBytes(bytes);

    final char[] hex = new char[length * 2];
    for (int j = 0; j < length; j++) {
      int v = bytes[j] & 0xFF;
      hex[j * 2] = HEX[v >>> 4];
      hex[j * 2 + 1] = HEX[v & 0x0F];
    }

    return new String(hex);
  }
}

