DMDirc-Client/src/main/java/com/dmdirc/ServerStatus.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.dmdirc;

import com.dmdirc.interfaces.Connection;
import com.dmdirc.parser.interfaces.Parser;
import com.dmdirc.util.collections.RollingList;

import java.util.ArrayList;
import java.util.List;

/**
 * Describes the status of a server and manages transitions between different states.
 *
 * @since 0.6.3m1
 */
public class ServerStatus {

    /** The connection to which this status belongs. */
    private final Connection connection;
    /** Object to notify when the state of the server changes. */
    private final Object notifier;
    /** The current state of the server. */
    private ServerState state = ServerState.DISCONNECTED;
    /** A history of transactions for debugging purposes. */
    private final RollingList<String> history = new RollingList<>(10);
    /** A list of known parser hashcodes. */
    private final List<Integer> parsers = new ArrayList<>();

    /**
     * Creates a new ServerStatus instance for the specified server.
     *
     * @param connection   The connection to which this status belongs
     * @param notifier The object to notify when the state changes
     *
     * @since 0.6.3
     */
    public ServerStatus(final Connection connection, final Object notifier) {
        this.connection = connection;
        this.notifier = notifier;
    }

    /**
     * Transitions the status of this object to the specified state.
     *
     * @param newState The state to transition to
     *
     * @throws IllegalArgumentException If the specified transition is invalid
     */
    public synchronized void transition(final ServerState newState) {
        addHistoryEntry(state, newState);

        if (state.canTransitionTo(newState)) {
            state = newState;

            synchronized (notifier) {
                notifier.notifyAll();
            }
        } else {
            throw new IllegalArgumentException("Illegal server state "
                    + "transition\n\n" + getTransitionHistory());
        }
    }

    /**
     * Retrieves the current state of this status object.
     *
     * @return This object's current state
     */
    public synchronized ServerState getState() {
        return state;
    }

    /**
     * Adds a history entry to this status object. The history entry contains the name of the states
     * being transitioned between, the details of the method (and class and line) which initiated
     * the transition, and the name of the thread in which the transition is occurring.
     *
     * @param fromState The state which is being transitioned from
     * @param toState   The state which is being transitioned to
     */
    protected void addHistoryEntry(final ServerState fromState, final ServerState toState) {
        final StringBuilder builder = new StringBuilder();
        builder.append(fromState.name());
        builder.append('\u2192');
        builder.append(toState.name());
        builder.append(' ');
        builder.append(Thread.currentThread().getStackTrace()[3]);
        builder.append(" [");
        builder.append(Thread.currentThread().getName());
        builder.append("] (parser #");
        builder.append(getParserID(connection.getParser().orElse(null)));
        builder.append(')');

        history.add(builder.toString());
    }

    /**
     * Retrieves the transition history of this status object as a string.
     *
     * @see #addHistoryEntry(ServerState, ServerState)
     * @return A line feed ('\n') delimited string containing one entry for each of the entries in
     *         this status's transition history.
     */
    public String getTransitionHistory() {
        final StringBuilder builder = new StringBuilder();

        for (String line : history.getList()) {
            if (builder.length() > 0) {
                builder.append('\n');
            }

            builder.append(line);
        }

        return builder.toString();
    }

    /**
     * Returns a unique, ID for the specified parser. Each parser that has been seen to be used by
     * this server is given a sequential id.
     *
     * @param parser The parser whose ID is being requested
     *
     * @return A unique ID for the specified parser, or 0 if the parser is null
     */
    public int getParserID(final Parser parser) {
        if (parser == null) {
            return 0;
        }

        final int hashcode = parser.hashCode();
        int offset;

        synchronized (parsers) {
            offset = parsers.indexOf(hashcode);

            if (offset == -1) {
                parsers.add(hashcode);
                offset = parsers.indexOf(hashcode);
            }
        }

        return 1 + offset;
    }

}