/*
 * Copyright 2010 the original author or authors.
 *
 * Licensed 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.
 */

package org.gradle.execution.taskgraph;

import groovy.lang.Closure;
import org.gradle.api.Action;
import org.gradle.api.Task;
import org.gradle.api.execution.TaskExecutionGraphListener;
import org.gradle.api.execution.TaskExecutionListener;
import org.gradle.api.execution.internal.InternalTaskExecutionListener;
import org.gradle.api.execution.internal.TaskOperationInternal;
import org.gradle.api.internal.TaskInternal;
import org.gradle.api.internal.tasks.TaskExecuter;
import org.gradle.api.internal.tasks.TaskStateInternal;
import org.gradle.api.internal.tasks.execution.DefaultTaskExecutionContext;
import org.gradle.api.specs.Spec;
import org.gradle.execution.TaskFailureHandler;
import org.gradle.execution.TaskGraphExecuter;
import org.gradle.initialization.BuildCancellationToken;
import org.gradle.internal.Factory;
import org.gradle.internal.TimeProvider;
import org.gradle.internal.event.ListenerBroadcast;
import org.gradle.internal.event.ListenerManager;
import org.gradle.internal.progress.BuildOperationExecutor;
import org.gradle.internal.progress.OperationIdGenerator;
import org.gradle.internal.progress.OperationResult;
import org.gradle.internal.progress.OperationStartEvent;
import org.gradle.listener.ClosureBackedMethodInvocationDispatch;
import org.gradle.util.Clock;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

public class DefaultTaskGraphExecuter implements TaskGraphExecuter {
    private static Logger logger = LoggerFactory.getLogger(DefaultTaskGraphExecuter.class);

    private enum TaskGraphState {
        EMPTY, DIRTY, POPULATED
    }

    private final TaskPlanExecutor taskPlanExecutor;
    // This currently needs to be lazy, as it uses state that is not available when the graph is created
    private final Factory<? extends TaskExecuter> taskExecuter;
    private final TimeProvider timeProvider;
    private final ListenerBroadcast<TaskExecutionGraphListener> graphListeners;
    private final ListenerBroadcast<TaskExecutionListener> taskListeners;
    private final ListenerBroadcast<InternalTaskExecutionListener> internalTaskListeners;
    private final DefaultTaskExecutionPlan taskExecutionPlan;
    private final BuildOperationExecutor buildOperationExecutor;
    private TaskGraphState taskGraphState = TaskGraphState.EMPTY;

    public DefaultTaskGraphExecuter(ListenerManager listenerManager, TaskPlanExecutor taskPlanExecutor, Factory<? extends TaskExecuter> taskExecuter, BuildCancellationToken cancellationToken, TimeProvider timeProvider, BuildOperationExecutor buildOperationExecutor) {
        this.taskPlanExecutor = taskPlanExecutor;
        this.taskExecuter = taskExecuter;
        this.timeProvider = timeProvider;
        this.buildOperationExecutor = buildOperationExecutor;
        graphListeners = listenerManager.createAnonymousBroadcaster(TaskExecutionGraphListener.class);
        taskListeners = listenerManager.createAnonymousBroadcaster(TaskExecutionListener.class);
        internalTaskListeners = listenerManager.createAnonymousBroadcaster(InternalTaskExecutionListener.class);
        taskExecutionPlan = new DefaultTaskExecutionPlan(cancellationToken);
    }

    public void useFailureHandler(TaskFailureHandler handler) {
        taskExecutionPlan.useFailureHandler(handler);
    }

    public void useFilter(Spec<? super Task> filter) {
        taskExecutionPlan.useFilter(filter);
        taskGraphState = TaskGraphState.DIRTY;
    }

    public void addTasks(Iterable<? extends Task> tasks) {
        assert tasks != null;

        Clock clock = new Clock();

        Set<Task> taskSet = new LinkedHashSet<Task>();
        for (Task task : tasks) {
            taskSet.add(task);
        }
        taskExecutionPlan.addToTaskGraph(taskSet);
        taskGraphState = TaskGraphState.DIRTY;

        logger.debug("Timing: Creating the DAG took " + clock.getTime());
    }

    public void execute() {
        Clock clock = new Clock();
        ensurePopulated();

        graphListeners.getSource().graphPopulated(this);
        try {
            taskPlanExecutor.process(taskExecutionPlan, new EventFiringTaskWorker(taskExecuter.create(), buildOperationExecutor.getCurrentOperationId()));
            logger.debug("Timing: Executing the DAG took " + clock.getTime());
        } finally {
            taskExecutionPlan.clear();
        }
    }

    public void addTaskExecutionGraphListener(TaskExecutionGraphListener listener) {
        graphListeners.add(listener);
    }

    public void removeTaskExecutionGraphListener(TaskExecutionGraphListener listener) {
        graphListeners.remove(listener);
    }

    public void whenReady(final Closure closure) {
        graphListeners.add(new ClosureBackedMethodInvocationDispatch("graphPopulated", closure));
    }

    public void addTaskExecutionListener(TaskExecutionListener listener) {
        taskListeners.add(listener);
    }

    public void removeTaskExecutionListener(TaskExecutionListener listener) {
        taskListeners.remove(listener);
    }

    public void beforeTask(final Closure closure) {
        taskListeners.add(new ClosureBackedMethodInvocationDispatch("beforeExecute", closure));
    }

    public void afterTask(final Closure closure) {
        taskListeners.add(new ClosureBackedMethodInvocationDispatch("afterExecute", closure));
    }

    public boolean hasTask(Task task) {
        ensurePopulated();
        return taskExecutionPlan.getTasks().contains(task);
    }

    public boolean hasTask(String path) {
        ensurePopulated();
        assert path != null && path.length() > 0;
        for (Task task : taskExecutionPlan.getTasks()) {
            if (task.getPath().equals(path)) {
                return true;
            }
        }
        return false;
    }

    public List<Task> getAllTasks() {
        ensurePopulated();
        return taskExecutionPlan.getTasks();
    }

    private void ensurePopulated() {
        switch (taskGraphState) {
            case EMPTY:
                throw new IllegalStateException(
                        "Task information is not available, as this task execution graph has not been populated.");
            case DIRTY:
                taskExecutionPlan.determineExecutionPlan();
                taskGraphState = TaskGraphState.POPULATED;
                return;
            case POPULATED:
        }
    }

    /**
     * This action will set the start and end times on the internal task state, and will make sure
     * that when a task is started, the public listeners are executed after the internal listeners
     * are executed and when a task is finished, the public listeners are executed before the internal
     * listeners are executed. Basically the internal listeners embrace the public listeners.
     */
    private class EventFiringTaskWorker implements Action<TaskInternal> {
        private final TaskExecuter taskExecuter;
        private final Object parentOperationId;

        public EventFiringTaskWorker(TaskExecuter taskExecuter, Object parentOperationId) {
            this.taskExecuter = taskExecuter;
            this.parentOperationId = parentOperationId;
        }

        @Override
        public void execute(TaskInternal task) {
            Object id = OperationIdGenerator.generateId(task);
            TaskOperationInternal taskOperation = new TaskOperationInternal(id, parentOperationId, task);
            TaskStateInternal state = task.getState();
            long startTime = timeProvider.getCurrentTime();
            internalTaskListeners.getSource().beforeExecute(taskOperation, new OperationStartEvent(startTime));
            try {
                taskListeners.getSource().beforeExecute(task);
                taskExecuter.execute(task, task.getState(), new DefaultTaskExecutionContext());
                taskListeners.getSource().afterExecute(task, state);
            } finally {
                long endTime = timeProvider.getCurrentTime();
                internalTaskListeners.getSource().afterExecute(taskOperation, new OperationResult(startTime, endTime, task.getState().getFailure()));
            }
        }
    }
}
