Use v8 engine for CSL (#2250)

Add a dependency to com.eclipsesource.J2V8 (Java Bindings for V8) in build.gradle. Citeproc-java detects that V8 is present in the classpath and starts using it automatically.

build.gradle

@@ -72,6 +72,26 @@ configurations {
     integrationTestRuntime.extendsFrom testRuntime
 }
 
+def getV8Dependency() {
+    def arch = System.getProperty('os.arch')
+    def dep = null
+    if (OperatingSystem.current().isWindows()) {
+        dep = 'win32_x86'
+        if (arch.equals('amd64')) {
+            dep += '_64'
+        }
+    } else if (OperatingSystem.current().isMacOsX() && (arch.equals('amd64') || arch.equals('x86_64'))) {
+        dep = 'macosx_x86_64'
+    } else if (OperatingSystem.current().isLinux() && arch.equals('amd64')) {
+        dep = 'linux_x86_64'
+    }
+    if (dep == null) {
+        logger.error("Could not find V8 runtime compatible to this system")
+        return null
+    }
+    return 'com.eclipsesource.j2v8:j2v8_' + dep + ':4.5.0'
+}
+
 dependencies {
     compile 'com.jgoodies:jgoodies-common:1.8.1'
     compile 'com.jgoodies:jgoodies-forms:1.9.0'
@@ -133,6 +153,11 @@ dependencies {
 
     compile 'com.github.lgooddatepicker:LGoodDatePicker:8.2.2'
 
+    // if available, use platform specific build of V8
+    if (getV8Dependency() != null) {
+        compile getV8Dependency()
+    }
+
     testCompile 'junit:junit:4.12'
     testCompile 'org.mockito:mockito-core:2.2.26'
     testCompile 'com.github.tomakehurst:wiremock:2.4.1'

external-libraries.txt

@@ -171,4 +171,9 @@ Project: Citeproc-Java
 URL:     http://michel-kraemer.github.io/citeproc-java/
 Licence: Apache-2.0
 
+Id:      com.eclipse.j2v8
+Project: J2V8
+URL:     https://github.com/eclipsesource/J2V8
+Licence: EPL-1.0
+
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