/*
 * Copyright 2002-2016 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
 *
 *      https://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.springframework.util;

import java.text.NumberFormat;
import java.util.LinkedList;
import java.util.List;

/**
 * Simple stop watch, allowing for timing of a number of tasks,
 * exposing total running time and running time for each named task.
 *
 * <p>Conceals use of {@code System.currentTimeMillis()}, improving the
 * readability of application code and reducing the likelihood of calculation errors.
 *
 * <p>Note that this object is not designed to be thread-safe and does not
 * use synchronization.
 *
 * <p>This class is normally used to verify performance during proof-of-concepts
 * and in development, rather than as part of production applications.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @since May 2, 2001
 */
public class StopWatch {

        /**
         * Identifier of this stop watch.
         * Handy when we have output from multiple stop watches
         * and need to distinguish between them in log or console output.
         */
        private final String id;

        private boolean keepTaskList = true;

        private final List<TaskInfo> taskList = new LinkedList<TaskInfo>();

        /** Start time of the current task */
        private long startTimeMillis;

        /** Is the stop watch currently running? */
        private boolean running;

        /** Name of the current task */
        private String currentTaskName;

        private TaskInfo lastTaskInfo;

        private int taskCount;

        /** Total running time */
        private long totalTimeMillis;


        /**
         * Construct a new stop watch. Does not start any task.
         */
        public StopWatch() {
                this("");
        }

        /**
         * Construct a new stop watch with the given id.
         * Does not start any task.
         * @param id identifier for this stop watch.
         * Handy when we have output from multiple stop watches
         * and need to distinguish between them.
         */
        public StopWatch(String id) {
                this.id = id;
        }


        /**
         * Return the id of this stop watch, as specified on construction.
         * @return the id (empty String by default)
         * @since 4.2.2
         * @see #StopWatch(String)
         */
        public String getId() {
                return this.id;
        }

        /**
         * Determine whether the TaskInfo array is built over time. Set this to
         * "false" when using a StopWatch for millions of intervals, or the task
         * info structure will consume excessive memory. Default is "true".
         */
        public void setKeepTaskList(boolean keepTaskList) {
                this.keepTaskList = keepTaskList;
        }


        /**
         * Start an unnamed task. The results are undefined if {@link #stop()}
         * or timing methods are called without invoking this method.
         * @see #stop()
         */
        public void start() throws IllegalStateException {
                start("");
        }

        /**
         * Start a named task. The results are undefined if {@link #stop()}
         * or timing methods are called without invoking this method.
         * @param taskName the name of the task to start
         * @see #stop()
         */
        public void start(String taskName) throws IllegalStateException {
                if (this.running) {
                        throw new IllegalStateException("Can't start StopWatch: it's already running");
                }
                this.running = true;
                this.currentTaskName = taskName;
                this.startTimeMillis = System.currentTimeMillis();
        }

        /**
         * Stop the current task. The results are undefined if timing
         * methods are called without invoking at least one pair
         * {@code start()} / {@code stop()} methods.
         * @see #start()
         */
        public void stop() throws IllegalStateException {
                if (!this.running) {
                        throw new IllegalStateException("Can't stop StopWatch: it's not running");
                }
                long lastTime = System.currentTimeMillis() - this.startTimeMillis;
                this.totalTimeMillis += lastTime;
                this.lastTaskInfo = new TaskInfo(this.currentTaskName, lastTime);
                if (this.keepTaskList) {
                        this.taskList.add(lastTaskInfo);
                }
                ++this.taskCount;
                this.running = false;
                this.currentTaskName = null;
        }

        /**
         * Return whether the stop watch is currently running.
         * @see #currentTaskName()
         */
        public boolean isRunning() {
                return this.running;
        }

        /**
         * Return the name of the currently running task, if any.
         * @since 4.2.2
         * @see #isRunning()
         */
        public String currentTaskName() {
                return this.currentTaskName;
        }


        /**
         * Return the time taken by the last task.
         */
        public long getLastTaskTimeMillis() throws IllegalStateException {
                if (this.lastTaskInfo == null) {
                        throw new IllegalStateException("No tasks run: can't get last task interval");
                }
                return this.lastTaskInfo.getTimeMillis();
        }

        /**
         * Return the name of the last task.
         */
        public String getLastTaskName() throws IllegalStateException {
                if (this.lastTaskInfo == null) {
                        throw new IllegalStateException("No tasks run: can't get last task name");
                }
                return this.lastTaskInfo.getTaskName();
        }

        /**
         * Return the last task as a TaskInfo object.
         */
        public TaskInfo getLastTaskInfo() throws IllegalStateException {
                if (this.lastTaskInfo == null) {
                        throw new IllegalStateException("No tasks run: can't get last task info");
                }
                return this.lastTaskInfo;
        }


        /**
         * Return the total time in milliseconds for all tasks.
         */
        public long getTotalTimeMillis() {
                return this.totalTimeMillis;
        }

        /**
         * Return the total time in seconds for all tasks.
         */
        public double getTotalTimeSeconds() {
                return this.totalTimeMillis / 1000.0;
        }

        /**
         * Return the number of tasks timed.
         */
        public int getTaskCount() {
                return this.taskCount;
        }

        /**
         * Return an array of the data for tasks performed.
         */
        public TaskInfo[] getTaskInfo() {
                if (!this.keepTaskList) {
                        throw new UnsupportedOperationException("Task info is not being kept!");
                }
                return this.taskList.toArray(new TaskInfo[this.taskList.size()]);
        }


        /**
         * Return a short description of the total running time.
         */
        public String shortSummary() {
                return "StopWatch '" + getId() + "': running time (millis) = " + getTotalTimeMillis();
        }

        /**
         * Return a string with a table describing all tasks performed.
         * For custom reporting, call getTaskInfo() and use the task info directly.
         */
        public String prettyPrint() {
                StringBuilder sb = new StringBuilder(shortSummary());
                sb.append('\n');
                if (!this.keepTaskList) {
                        sb.append("No task info kept");
                }
                else {
                        sb.append("-----------------------------------------\n");
                        sb.append("ms     %     Task name\n");
                        sb.append("-----------------------------------------\n");
                        NumberFormat nf = NumberFormat.getNumberInstance();
                        nf.setMinimumIntegerDigits(5);
                        nf.setGroupingUsed(false);
                        NumberFormat pf = NumberFormat.getPercentInstance();
                        pf.setMinimumIntegerDigits(3);
                        pf.setGroupingUsed(false);
                        for (TaskInfo task : getTaskInfo()) {
                                sb.append(nf.format(task.getTimeMillis())).append("  ");
                                sb.append(pf.format(task.getTimeSeconds() / getTotalTimeSeconds())).append("  ");
                                sb.append(task.getTaskName()).append("\n");
                        }
                }
                return sb.toString();
        }

        /**
         * Return an informative string describing all tasks performed
         * For custom reporting, call {@code getTaskInfo()} and use the task info directly.
         */
        @Override
        public String toString() {
                StringBuilder sb = new StringBuilder(shortSummary());
                if (this.keepTaskList) {
                        for (TaskInfo task : getTaskInfo()) {
                                sb.append("; [").append(task.getTaskName()).append("] took ").append(task.getTimeMillis());
                                long percent = Math.round((100.0 * task.getTimeSeconds()) / getTotalTimeSeconds());
                                sb.append(" = ").append(percent).append("%");
                        }
                }
                else {
                        sb.append("; no task info kept");
                }
                return sb.toString();
        }


        /**
         * Inner class to hold data about one task executed within the stop watch.
         */
        public static final class TaskInfo {

                private final String taskName;

                private final long timeMillis;

                TaskInfo(String taskName, long timeMillis) {
                        this.taskName = taskName;
                        this.timeMillis = timeMillis;
                }

                /**
                 * Return the name of this task.
                 */
                public String getTaskName() {
                        return this.taskName;
                }

                /**
                 * Return the time in milliseconds this task took.
                 */
                public long getTimeMillis() {
                        return this.timeMillis;
                }

                /**
                 * Return the time in seconds this task took.
                 */
                public double getTimeSeconds() {
                        return (this.timeMillis / 1000.0);
                }
        }

}