/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
// DWB8: throw IllegatlStateException if session used after closed (as per rfc132)
// DWB9: there is no API to list all variables: https://www.osgi.org/bugzilla/show_bug.cgi?id=49
// DWB10: add SCOPE support: https://www.osgi.org/bugzilla/show_bug.cgi?id=51
package org.apache.felix.gogo.runtime;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.nio.channels.Channel;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.Formatter;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import org.apache.felix.service.command.Job;
import org.apache.felix.service.command.Job.Status;
import org.apache.felix.service.command.JobListener;
import org.apache.felix.service.command.Process;
import org.apache.felix.gogo.runtime.Pipe.Result;
import org.apache.felix.service.command.CommandProcessor;
import org.apache.felix.service.command.CommandSession;
import org.apache.felix.service.command.Converter;
import org.apache.felix.service.command.Function;
import org.apache.felix.service.threadio.ThreadIO;

public class CommandSessionImpl implements CommandSession, Converter
{
    public static final String SESSION_CLOSED = "session is closed";
    public static final String VARIABLES = ".variables";
    public static final String COMMANDS = ".commands";
    public static final String CONSTANTS = ".constants";
    private static final String COLUMN = "%-20s %s\n";

    // Streams and channels
    protected InputStream in;
    protected OutputStream out;
    protected PrintStream pout;
    protected OutputStream err;
    protected PrintStream perr;
    protected Channel[] channels;

    private final CommandProcessorImpl processor;
    protected final ConcurrentMap<String, Object> variables = new ConcurrentHashMap<>();
    private volatile boolean closed;
    private final List<JobImpl> jobs = new ArrayList<>();
    private JobListener jobListener;

    private final ExecutorService executor;

    private Path currentDir;
    private ClassLoader classLoader;

    protected CommandSessionImpl(CommandProcessorImpl shell, CommandSessionImpl parent)
    {
        this.currentDir = parent.currentDir;
        this.executor = Executors.newCachedThreadPool(ThreadUtils.namedThreadFactory("session"));
        this.processor = shell;
        this.channels = parent.channels;
        this.in = parent.in;
        this.out = parent.out;
        this.err = parent.err;
        this.pout = parent.pout;
        this.perr = parent.perr;
    }

    protected CommandSessionImpl(CommandProcessorImpl shell, InputStream in, OutputStream out, OutputStream err)
    {
        this.currentDir = Paths.get(System.getProperty("user.dir")).toAbsolutePath().normalize();
        this.executor = Executors.newCachedThreadPool(ThreadUtils.namedThreadFactory("session"));
        this.processor = shell;
        ReadableByteChannel inCh = Channels.newChannel(in);
        WritableByteChannel outCh = Channels.newChannel(out);
        WritableByteChannel errCh = out == err ? outCh : Channels.newChannel(err);
        this.channels = new Channel[] { inCh, outCh, errCh };
        this.in = in;
        this.out = out;
        this.err = err;
        this.pout = out instanceof PrintStream ? (PrintStream) out : new PrintStream(out, true);
        this.perr = out == err ? pout : err instanceof PrintStream ? (PrintStream) err : new PrintStream(err, true);
    }

    ThreadIO threadIO()
    {
        return processor.threadIO;
    }

    public CommandProcessor processor()
    {
        return processor;
    }

    public ConcurrentMap<String, Object> getVariables()
    {
        return variables;
    }

    public Path currentDir()
    {
        return currentDir;
    }

    public void currentDir(Path path)
    {
        currentDir = path;
    }

    public ClassLoader classLoader()
    {
        return classLoader != null ? classLoader : getClass().getClassLoader();
    }

    public void classLoader(ClassLoader classLoader)
    {
        this.classLoader = classLoader;
    }

    public void close()
    {
        if (!this.closed)
        {
            this.closed = true;
            this.processor.closeSession(this);
            executor.shutdownNow();
        }
    }

    public Object execute(CharSequence commandline) throws Exception
    {
        assert processor != null;

        if (closed)
        {
            throw new IllegalStateException(SESSION_CLOSED);
        }

        processor.beforeExecute(this, commandline);

        try
        {
            Closure impl = new Closure(this, null, commandline);
            Object result = impl.execute(this, null);
            processor.afterExecute(this, commandline, result);
            return result;
        }
        catch (Exception e)
        {
            processor.afterExecute(this, commandline, e);
            throw e;
        }
    }

    public InputStream getKeyboard()
    {
        return in;
    }

    public Object get(String name)
    {
        // there is no API to list all variables, so overload name == null
        if (name == null || VARIABLES.equals(name))
        {
            return Collections.unmodifiableSet(variables.keySet());
        }

        if (COMMANDS.equals(name))
        {
            return processor.getCommands();
        }

        if (CONSTANTS.equals(name))
        {
            return Collections.unmodifiableSet(processor.constants.keySet());
        }

        Object val = processor.constants.get(name);
        if (val != null)
        {
            return val;
        }

        val = variables.get("#" + name);
        if (val instanceof Function)
        {
            try
            {
                val = ((Function) val).execute(this, null);
            }
            catch (Exception e)
            {
                // Ignore
            }
            return val;
        }
        else if (val != null)
        {
            return val;
        }

        val = variables.get(name);
        if (val != null)
        {
            return val;
        }

        return processor.getCommand(name, variables.get("SCOPE"));
    }

    public Object put(String name, Object value)
    {
        if (value != null)
        {
            return variables.put(name, value);
        }
        else
        {
            return variables.remove(name);
        }
    }

    public PrintStream getConsole()
    {
        return pout;
    }

    @SuppressWarnings("unchecked")
    public CharSequence format(Object target, int level, Converter escape) throws Exception
    {
        if (target == null)
        {
            return "null";
        }

        if (target instanceof CharSequence)
        {
            return (CharSequence) target;
        }

        for (Converter c : processor.converters)
        {
            CharSequence s = c.format(target, level, this);
            if (s != null)
            {
                return s;
            }
        }

        if (target.getClass().isArray())
        {
            if (target.getClass().getComponentType().isPrimitive())
            {
                if (target.getClass().getComponentType() == boolean.class)
                {
                    return Arrays.toString((boolean[]) target);
                }
                else
                {
                    if (target.getClass().getComponentType() == byte.class)
                    {
                        return Arrays.toString((byte[]) target);
                    }
                    else
                    {
                        if (target.getClass().getComponentType() == short.class)
                        {
                            return Arrays.toString((short[]) target);
                        }
                        else
                        {
                            if (target.getClass().getComponentType() == int.class)
                            {
                                return Arrays.toString((int[]) target);
                            }
                            else
                            {
                                if (target.getClass().getComponentType() == long.class)
                                {
                                    return Arrays.toString((long[]) target);
                                }
                                else
                                {
                                    if (target.getClass().getComponentType() == float.class)
                                    {
                                        return Arrays.toString((float[]) target);
                                    }
                                    else
                                    {
                                        if (target.getClass().getComponentType() == double.class)
                                        {
                                            return Arrays.toString((double[]) target);
                                        }
                                        else
                                        {
                                            if (target.getClass().getComponentType() == char.class)
                                            {
                                                return Arrays.toString((char[]) target);
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
            target = Arrays.asList((Object[]) target);
        }
        if (target instanceof Collection)
        {
            if (level == Converter.INSPECT)
            {
                StringBuilder sb = new StringBuilder();
                Collection<?> c = (Collection<?>) target;
                for (Object o : c)
                {
                    sb.append(format(o, level + 1, this));
                    sb.append("\n");
                }
                return sb;
            }
            else
            {
                if (level == Converter.LINE)
                {
                    StringBuilder sb = new StringBuilder();
                    Collection<?> c = (Collection<?>) target;
                    sb.append("[");
                    for (Object o : c)
                    {
                        if (sb.length() > 1)
                        {
                            sb.append(", ");
                        }
                        sb.append(format(o, level + 1, this));
                    }
                    sb.append("]");
                    return sb;
                }
            }
        }
        if (target instanceof Dictionary)
        {
            Map<Object, Object> result = new HashMap<>();
            for (Enumeration<Object> e = ((Dictionary<Object, Object>) target).keys(); e.hasMoreElements();)
            {
                Object key = e.nextElement();
                result.put(key, ((Dictionary<Object, Object>) target).get(key));
            }
            target = result;
        }
        if (target instanceof Map)
        {
            if (level == Converter.INSPECT)
            {
                StringBuilder sb = new StringBuilder();
                Map<?, ?> c = (Map<?, ?>) target;
                for (Map.Entry<?, ?> entry : c.entrySet())
                {
                    CharSequence key = format(entry.getKey(), level + 1, this);
                    sb.append(key);
                    for (int i = key.length(); i < 20; i++)
                    {
                        sb.append(' ');
                    }
                    sb.append(format(entry.getValue(), level + 1, this));
                    sb.append("\n");
                }
                return sb;
            }
            else
            {
                if (level == Converter.LINE)
                {
                    StringBuilder sb = new StringBuilder();
                    Map<?, ?> c = (Map<?, ?>) target;
                    sb.append("[");
                    for (Map.Entry<?, ?> entry : c.entrySet())
                    {
                        if (sb.length() > 1)
                        {
                            sb.append(", ");
                        }
                        sb.append(format(entry, level + 1, this));
                    }
                    sb.append("]");
                    return sb;
                }
            }
        }
        if (target instanceof Path)
        {
            return target.toString();
        }
        if (level == Converter.INSPECT)
        {
            return inspect(target);
        }
        else
        {
            return target.toString();
        }
    }

    CharSequence inspect(Object b)
    {
        boolean found = false;
        try (Formatter f = new Formatter();)
        {
            Method methods[] = b.getClass().getMethods();
            for (Method m : methods)
            {
                try
                {
                    String name = m.getName();
                    if (m.getName().startsWith("get") && !m.getName().equals("getClass") && m.getParameterTypes().length == 0 && Modifier.isPublic(m.getModifiers()))
                    {
                        found = true;
                        name = name.substring(3);
                        m.setAccessible(true);
                        Object value = m.invoke(b, (Object[]) null);
                        f.format(COLUMN, name, format(value, Converter.LINE, this));
                    }
                }
                catch (Exception e)
                {
                    // Ignore
                }
            }
            if (found)
            {
                return (StringBuilder) f.out();
            }
            else
            {
                return b.toString();
            }
        }
    }

    public Object convert(Class<?> desiredType, Object in)
    {
        return processor.convert(this, desiredType, in);
    }

    public Object doConvert(Class<?> desiredType, Object in)
    {
        if (desiredType == Class.class)
        {
            try
            {
                return Class.forName(in.toString(), true, classLoader());
            }
            catch (ClassNotFoundException e)
            {
                return null;
            }
        }
        return processor.doConvert(desiredType, in);
    }

    public CharSequence format(Object result, int inspect)
    {
        try
        {
            return format(result, inspect, this);
        }
        catch (Exception e)
        {
            return "<can not format " + result + ":" + e;
        }
    }

    public Object expr(CharSequence expr)
    {
        return processor.expr(this, expr);
    }

    public Object invoke(Object target, String name, List<Object> args) throws Exception
    {
        return processor.invoke(this, target, name, args);
    }

    public Path redirect(Path path, int mode)
    {
        return processor.redirect(this, path, mode);
    }

    @Override
    public List<Job> jobs()
    {
        synchronized (jobs)
        {
            return Collections.<Job>unmodifiableList(jobs);
        }
    }

    public static JobImpl currentJob()
    {
        return (JobImpl) Job.Utils.current();
    }

    @Override
    public JobImpl foregroundJob()
    {
        List<JobImpl> jobs;
        synchronized (this.jobs)
        {
            jobs = new ArrayList<>(this.jobs);
        }
        for (JobImpl j : jobs) {
            if (j.parent == null && j.status() == Status.Foreground) {
                return j;
            }
        }
        return null;
    }

    @Override
    public void setJobListener(JobListener listener)
    {
        synchronized (jobs)
        {
            jobListener = listener;
        }
    }

    public JobImpl createJob(CharSequence command)
    {
        synchronized (jobs)
        {
            int id = 1;

            boolean found;
            do
            {
                found = false;
                for (Job job : jobs)
                {
                    if (job.id() == id)
                    {
                        found = true;
                        id++;
                        break;
                    }
                }
            }
            while (found);

            JobImpl cur = currentJob();
            JobImpl job = new JobImpl(id, cur, command);
            if (cur == null)
            {
                jobs.add(job);
            }
            else
            {
                cur.add(job);
            }
            return job;
        }
    }

    class JobImpl implements Job, Runnable
    {
        private final int id;
        private final JobImpl parent;
        private final CharSequence command;
        private final List<Pipe> pipes = new ArrayList<>();
        private final List<Job> children = new ArrayList<>();
        private Status status = Status.Created;
        private Future<?> future;
        private Result result;

        public JobImpl(int id, JobImpl parent, CharSequence command)
        {
            this.id = id;
            this.parent = parent;
            this.command = command;
        }

        void addPipe(Pipe pipe)
        {
            pipes.add(pipe);
        }

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

        public CharSequence command()
        {
            return command;
        }

        @Override
        public synchronized Status status()
        {
            return status;
        }

        @Override
        public synchronized void suspend()
        {
            if (status == Status.Done)
            {
                throw new IllegalStateException("Job is finished");
            }
            if (status != Status.Suspended)
            {
                setStatus(Status.Suspended);
            }
        }

        @Override
        public synchronized void background()
        {
            if (status == Status.Done)
            {
                throw new IllegalStateException("Job is finished");
            }
            if (status != Status.Background)
            {
                setStatus(Status.Background);
            }
        }

        @Override
        public synchronized void foreground()
        {
            if (status == Status.Done)
            {
                throw new IllegalStateException("Job is finished");
            }
            JobImpl cr = CommandSessionImpl.currentJob();
            JobImpl fg = foregroundJob();
            if (parent == null && fg != null && fg != this && fg != cr)
            {
                throw new IllegalStateException("A job is already in foreground");
            }
            if (status != Status.Foreground)
            {
                setStatus(Status.Foreground);
            }
        }

        @Override
        public void interrupt()
        {
            Future<?> future;
            List<Job> children;
            synchronized (this)
            {
                future = this.future;
            }
            synchronized (this.children)
            {
                children = new ArrayList<>(this.children);
            }
            for (Job job : children)
            {
                job.interrupt();
            }
            if (future != null)
            {
                future.cancel(true);
            }
        }

        protected synchronized void done()
        {
            if (status == Status.Done)
            {
                throw new IllegalStateException("Job is finished");
            }
            setStatus(Status.Done);
        }

        private void setStatus(Status newStatus)
        {
            setStatus(newStatus, true);
        }

        private void setStatus(Status newStatus, boolean callListeners)
        {
            Status previous;
            synchronized (this)
            {
                previous = this.status;
                status = newStatus;
            }
            if (callListeners)
            {
                JobListener listener;
                synchronized (jobs)
                {
                    listener = jobListener;
                    if (newStatus == Status.Done)
                    {
                        jobs.remove(this);
                    }
                }
                if (listener != null)
                {
                    listener.jobChanged(this, previous, newStatus);
                }
            }
            synchronized (this)
            {
                JobImpl.this.notifyAll();
            }
        }

        @Override
        public synchronized Result result()
        {
            return result;
        }

        @Override
        public Job parent()
        {
            return parent;
        }

        /**
         * Start the job.
         * If the job is started in foreground,
         * waits for the job to finish or to be
         * suspended or moved to background.
         *
         * @param status the desired job status
         * @return <code>null</code> if the job
         *   has been suspended or moved to background,
         *
         */
        public synchronized Result start(Status status) throws InterruptedException
        {
            if (status == Status.Created || status == Status.Done)
            {
                throw new IllegalArgumentException("Illegal start status");
            }
            if (this.status != Status.Created)
            {
                throw new IllegalStateException("Job already started");
            }
            switch (status)
            {
                case Suspended:
                    suspend();
                    break;
                case Background:
                    background();
                    break;
                case Foreground:
                    foreground();
                    break;
                case Created:
                case Done:
            }
            future = executor.submit(this);
            while (this.status == Status.Foreground)
            {
                JobImpl.this.wait();
            }
            return result;
        }

        public List<Process> processes()
        {
            return Collections.unmodifiableList((List<? extends Process>)pipes);
        }

        @Override
        public CommandSession session()
        {
            return CommandSessionImpl.this;
        }

        public void run()
        {
            Thread thread = Thread.currentThread();
            String name = thread.getName();
            try
            {
                thread.setName("job controller " + id);

                List<Callable<Result>> wrapped = new ArrayList<Callable<Result>>(pipes);
                List<Future<Result>> results = executor.invokeAll(wrapped);

                // Get pipe exceptions
                Exception pipeException = null;
                for (int i = 0; i < results.size() - 1; i++)
                {
                    Future<Result> future = results.get(i);
                    Throwable e;
                    try
                    {
                        Result r = future.get();
                        e = r.exception;
                    }
                    catch (ExecutionException ee)
                    {
                        e = ee.getCause();
                    }
                    if (e != null)
                    {
                        if (pipeException == null)
                        {
                            pipeException = new Exception("Exception caught during pipe execution");
                        }
                        pipeException.addSuppressed(e);
                    }
                }
                put(Closure.PIPE_EXCEPTION, pipeException);

                result = results.get(results.size() - 1).get();
            }
            catch (Exception e)
            {
                result = new Result(e);
            }
            catch (Throwable t)
            {
                result = new Result(new ExecutionException(t));
            }
            finally
            {
                done();
                thread.setName(name);
            }
        }

        public void add(Job child)
        {
            synchronized (children)
            {
                children.add(child);
            }
        }
    }

}