/**
 * 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.
 */
package org.apache.bookkeeper.stats.prometheus;

import static com.google.common.base.Preconditions.checkArgument;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import com.google.common.base.MoreObjects;
import com.google.common.base.Splitter;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

import java.io.StringWriter;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.bookkeeper.stats.Counter;
import org.apache.bookkeeper.stats.OpStatsLogger;
import org.apache.bookkeeper.stats.StatsLogger;
import org.junit.Test;

/**
 * Test for {@link PrometheusMetricsProvider}.
 */
public class TestPrometheusFormatter {

    @Test
    public void testStatsOutput() throws Exception {
        PrometheusMetricsProvider provider = new PrometheusMetricsProvider();
        StatsLogger statsLogger = provider.getStatsLogger("test");
        Counter counter = statsLogger.getCounter("my_counter");

        counter.inc();
        counter.inc();

        OpStatsLogger opStats = statsLogger.getOpStatsLogger("op");
        opStats.registerSuccessfulEvent(10, TimeUnit.MILLISECONDS);
        opStats.registerSuccessfulEvent(5, TimeUnit.MILLISECONDS);

        provider.rotateLatencyCollection();

        StringWriter writer = new StringWriter();
        provider.writeAllMetrics(writer);
        System.out.println(writer);
        Multimap<String, Metric> metrics = parseMetrics(writer.toString());
        System.out.println(metrics);

        List<Metric> cm = (List<Metric>) metrics.get("test_my_counter");
        assertEquals(1, cm.size());
        assertEquals(0, cm.get(0).tags.size());
        assertEquals(2.0, cm.get(0).value, 0.0);

        // test_op_sum
        cm = (List<Metric>) metrics.get("test_op_sum");
        assertEquals(2, cm.size());
        Metric m = cm.get(0);
        assertEquals(1, cm.get(0).tags.size());
        assertEquals(0.0, m.value, 0.0);
        assertEquals(1, m.tags.size());
        assertEquals("false", m.tags.get("success"));

        m = cm.get(1);
        assertEquals(1, cm.get(0).tags.size());
        assertEquals(15.0, m.value, 0.0);
        assertEquals(1, m.tags.size());
        assertEquals("true", m.tags.get("success"));

        // test_op_count
        cm = (List<Metric>) metrics.get("test_op_count");
        assertEquals(2, cm.size());
        m = cm.get(0);
        assertEquals(1, cm.get(0).tags.size());
        assertEquals(0.0, m.value, 0.0);
        assertEquals(1, m.tags.size());
        assertEquals("false", m.tags.get("success"));

        m = cm.get(1);
        assertEquals(1, cm.get(0).tags.size());
        assertEquals(2.0, m.value, 0.0);
        assertEquals(1, m.tags.size());
        assertEquals("true", m.tags.get("success"));

        // Latency
        cm = (List<Metric>) metrics.get("test_op");
        assertEquals(14, cm.size());

        boolean found = false;
        for (Metric mt  : cm) {
            if ("true".equals(mt.tags.get("success")) && "1.0".equals(mt.tags.get("quantile"))) {
                assertEquals(10.0, mt.value, 0.0);
                found = true;
            }
        }

        assertTrue(found);
    }

    /**
     * Hacky parsing of Prometheus text format. Sould be good enough for unit tests
     */
    private static Multimap<String, Metric> parseMetrics(String metrics) {
        Multimap<String, Metric> parsed = ArrayListMultimap.create();

        // Example of lines are
        // jvm_threads_current{cluster="standalone",} 203.0
        // or
        // pulsar_subscriptions_count{cluster="standalone", namespace="sample/standalone/ns1",
        // topic="persistent://sample/standalone/ns1/test-2"} 0.0 1517945780897
        Pattern pattern = Pattern.compile("^(\\w+)(\\{([^\\}]+)\\})?\\s(-?[\\d\\w\\.]+)(\\s(\\d+))?$");
        Pattern tagsPattern = Pattern.compile("(\\w+)=\"([^\"]+)\"(,\\s?)?");

        Splitter.on("\n").split(metrics).forEach(line -> {
            if (line.isEmpty() || line.startsWith("#")) {
                return;
            }

            System.err.println("LINE: '" + line + "'");
            Matcher matcher = pattern.matcher(line);
            System.err.println("Matches: " + matcher.matches());
            System.err.println(matcher);

            System.err.println("groups: " + matcher.groupCount());
            for (int i = 0; i < matcher.groupCount(); i++) {
                System.err.println("   GROUP " + i + " -- " + matcher.group(i));
            }

            checkArgument(matcher.matches());
            String name = matcher.group(1);

            Metric m = new Metric();
            m.value = Double.valueOf(matcher.group(4));

            String tags = matcher.group(3);
            if (tags != null) {
                Matcher tagsMatcher = tagsPattern.matcher(tags);
                while (tagsMatcher.find()) {
                    String tag = tagsMatcher.group(1);
                    String value = tagsMatcher.group(2);
                    m.tags.put(tag, value);
                }
            }

            parsed.put(name, m);
        });

        return parsed;
    }

    static class Metric {
        Map<String, String> tags = new TreeMap<>();
        double value;

        @Override
        public String toString() {
            return MoreObjects.toStringHelper(this).add("tags", tags).add("value", value).toString();
        }
    }
}