Initial plugin version

.gitignore

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+target
+.idea
+*.iml
+*.jar
+*.class

README.md

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 gorgeo
 ======
+
+Provides a facet for grouping documents containing geolocation data based on 
+the geohash cells. It groups the geographical points by using 
+[geohash](http://en.wikipedia.org/wiki/Geohash) cells, according to the 
+level provided by user.
+
+### Installation
+
+TODO
+
+### Example usage
+
+Query example:
+
+```json
+  "geohashcell": {
+    "field": "location",
+    "level" : 3,
+    "top_left": "11.21,51.33",
+    "bottom_right": "-20.21,80.65"
+}
+```
+
+
+
+Result example:
+
+```json
+   "facets": {
+      "f": {
+         "_type": "Z2VvaGFzaGNlbGw=",
+         "field": "location",
+         "top_left": "[11.21, 51.33]",
+         "bottom_right": "[-20.21, 80.65]",
+         "level": 4,
+         "base_map_level": 1,
+         "counts": {
+            "[8.876953125, 76.46484375]": "1",
+            "[6.240234375, 79.98046875]": "1",
+            "[6.943359375, 79.98046875]": "13",
+            "[9.755859375, 77.87109375]": "2",
+            "[2.197265625, 72.94921875]": "1",
+            "[9.931640625, 77.51953125]": "3",
+            ...
+         }
+   }
+```
+
+### Parameters
+
+| Parameter name   | Optional   | Default value     | Description                                                                                            
+| ---------------- | :--------: | :---------------: | -------------
+| __field__        | _optional_ | "location"        | Name of the document field containing geographical location.
+| __top_left__     | _optional_ | "90,-180"         | Geographical coordinates (lattitude, longitude) of the top left point of the current map viewport.
+| __bottom_right__ | _optional_ | "-90,180"         | Geographical coordinates (lattitude, longitude) of the bottom right point of the current map viewport.
+| __level__        | _optional_ | 3                 | The grouping level (see [Algorithm](#Algorithm)).
+
+_Note_: the map viewport defaults to a full map.
+
+### Results
+
+ * __field__ - equal to the __field__ parameter 
+ * __top_left__ - equal to the __top_left__ parameter
+ * __bottom_right__ - equal to the __bottom_right__ parameter
+ * __level__ - actual grouping level (see [Algorithm](#Algorithm))
+ * __base_map_level__ - base grouping level for the current map viewport
+ * __counts__ - grouping results, contain cell center and corresponding 
+   document count
+
+### Algorithm
+
+The facet counts the documents based on geohash prefixes. For more information
+on how geohashing works, see the following links:
+
+ * [Wikipedia on Geohash](http://en.wikipedia.org/wiki/Geohash)
+ * [Visualizing Geohash](http://www.bigdatamodeling.org/2013/01/intuitive-geohash.html)
+
+The algorithm groups documents based on geohash prefixes of the stored 
+geographical data. The __level__ parameter provided to the facet is used as 
+a lenght of the geohash prefix for grouping, i.e. increasing the level by one,
+divides the map into 32 cells.
+
+Additionally the facet adapts to the current map viewport by comparing the 
+current viewport size with sizes of the geohash cells and calculates the
+__base_map_level__. This level is than added to the level parameter and used 
+as a geohash prefix. The result is always in [1,6] range.
+
+### To do
+ * better parameter checking
+ * more tests
+
+Credits
+=======
+Thanks to [Mahesh Paolini-Subramanya](https://github.com/dieswaytoofast) for his help.

assembly/release.xml

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+<?xml version="1.0"?>
+<assembly>
+    <id>bin</id>
+    <formats>
+        <format>zip</format>
+    </formats>
+    <includeBaseDirectory>false</includeBaseDirectory>
+    <dependencySets>
+        <dependencySet>
+            <unpack>false</unpack>
+            <outputDirectory>/</outputDirectory>
+            <useProjectArtifact>false</useProjectArtifact>
+            <useTransitiveFiltering>true</useTransitiveFiltering>
+            <excludes>
+                <exclude>org.elasticsearch:elasticsearch</exclude>
+                <exclude>junit:junit</exclude>
+            </excludes>
+        </dependencySet>
+    </dependencySets>
+    <fileSets>
+        <fileSet>
+            <directory>${project.build.directory}/</directory>
+            <outputDirectory>/</outputDirectory>
+            <includes>
+                <include>elasticsearch-${project.name}-${elasticsearch.version}.jar</include>
+            </includes>
+        </fileSet>
+    </fileSets>
+</assembly>

pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.elasticsearch.plugin.geohashcellfacet</groupId>
+    <artifactId>GeoHashCellFacetPlugin</artifactId>
+    <packaging>jar</packaging>
+    <version>1.0</version>
+    <name>GeoHashCellFacetPlugin</name>
+    <url>http://maven.apache.org</url>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>2.3</version>
+                <configuration>
+                    <finalName>
+                        elasticsearch-${project.name}-${elasticsearch.version}
+                    </finalName>
+                </configuration>
+            </plugin>
+            <!-- Copy dependencies into lib folder -->
+            <!-- To see full classpath use  mvn dependency:build-classpath -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>2.2</version>
+                <executions>
+                    <execution>
+                        <id>copy-dependencies</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}/lib
+                            </outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <!-- Skip Surefire tests -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.8</version>
+                <configuration>
+                    <skipTests>true</skipTests>
+                    <additionalClasspathElements>
+                        <additionalClasspathElement>
+                            ${project.build.directory}/classes/conf
+                        </additionalClasspathElement>
+                        <additionalClasspathElement>
+                            ${project.build.directory}/lib
+                        </additionalClasspathElement>
+                    </additionalClasspathElements>
+                </configuration>
+            </plugin>
+            <!-- Generate the release zip file (run during package step) -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <version>2.2.1</version>
+                <configuration>
+                    <finalName>
+                        elasticsearch-${project.name}-${elasticsearch.version}
+                    </finalName>
+                    <appendAssemblyId>false</appendAssemblyId>
+                    <outputDirectory>${project.build.directory}/release/
+                    </outputDirectory>
+                    <descriptors>
+                        <descriptor>assembly/release.xml</descriptor>
+                    </descriptors>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>generate-release-plugin</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+                <includes>
+                    <include>**/*.properties</include>
+                </includes>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <elasticsearch.version>0.90.5</elasticsearch.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.8.2</version>
+        </dependency>
+        <dependency>
+            <groupId>org.elasticsearch</groupId>
+            <artifactId>elasticsearch</artifactId>
+            <version>${elasticsearch.version}</version>
+        </dependency>
+    </dependencies>
+    <repositories>
+        <repository>
+            <id>sonatype</id>
+            <name>Sonatype Groups</name>
+            <url>https://oss.sonatype.org/content/groups/public/</url>
+        </repository>
+    </repositories>
+</project>

src/main/java/org/elasticsearch/plugin/geohashcellfacet/GeoHashCell.java

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+package org.elasticsearch.plugin.geohashcellfacet;
+
+import org.elasticsearch.common.geo.GeoHashUtils;
+import org.elasticsearch.common.geo.GeoPoint;
+
+/**
+ * Represents a cell established by the geo hash prefix.
+ */
+public class GeoHashCell {
+    public final static int MIN_GEOHASH_LEVEL = 1;
+    public final static int MAX_GEOHASH_LEVEL = 6;
+
+    private final String geoHashPrefix;
+    private final GeoPoint topLeft = new GeoPoint();
+    private final GeoPoint bottomRight = new GeoPoint();
+
+    /**
+     * Creates a geo hash cell of the provided level which includes the given point.
+     *
+     * @param point Point which should be included in this cell.
+     * @param level Level for the cell, i.e. the length of the geo hash.
+     */
+    public GeoHashCell(GeoPoint point, int level) {
+        this(GeoHashUtils.encode(point.lat(), point.lon()).substring(0, level));
+    }
+
+    /**
+     * Creates a geo hash cell instance based on the given geo hash prefix.
+     * @param geoHashPrefix Prefix for the geo hash cell.
+     */
+    public GeoHashCell(String geoHashPrefix) {
+        if (geoHashPrefix == null || geoHashPrefix.isEmpty())
+            throw new IllegalArgumentException("GeoHash value is required");
+        this.geoHashPrefix = geoHashPrefix;
+
+        GeoHashUtils.decodeCell(geoHashPrefix, topLeft, bottomRight);
+    }
+
+    /**
+     * Gets the point which is a center of this geo hash cell.
+     * @return Center of this cell.
+     */
+    public GeoPoint getCenter() {
+        return new GeoPoint(
+                (topLeft.lat() + bottomRight.lat()) / 2D,
+                (topLeft.lon() + bottomRight.lon()) / 2D
+        );
+    }
+
+    /**
+     * Compare if this object equals another object.
+     * @param o Object to compare.
+     * @return True if objects are equal, otherwise false.
+     */
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        GeoHashCell that = (GeoHashCell) o;
+
+        return geoHashPrefix.equals(that.geoHashPrefix);
+    }
+
+    /**
+     * Gets a hash code of this instance.
+     * @return Hash code.
+     */
+    @Override
+    public int hashCode() {
+        return geoHashPrefix.hashCode();
+    }
+
+    /**
+     * Gets a string representation of this instance.
+     * @return String representation.
+     */
+    @Override
+    public String toString() {
+        return getCenter().toString();
+    }
+}