localization.gradle

import groovy.json.JsonSlurper
import groovy.json.StringEscapeUtils
import groovy.xml.MarkupBuilder

File.metaClass.leftShift = { Object text ->
    delegate.append text
    delegate.append "\n"
    return delegate
}

File.metaClass.writeLn << { Object text ->
    delegate.write text
    delegate.append "\n"
    return delegate
}

Project project = project

class TranslationExtension {
    private final String s = File.separator

    Object defaultLang = null

    File dir

    TranslationExtension(Project project) {
        //we put resources into a separate module 'translations'
        dir = project.rootProject.project("translations").projectDir
    }

    String getStrPath(String locale) {
        final String prefix
        if (locale == defaultLang.locale) prefix = "" else prefix = "-${locale}"

        return "src${s}main${s}res${s}values${prefix}${s}translations.xml"
    }
}

project.extensions.create("translation", TranslationExtension, project)

void generateTranslationClass() {
    final def defaultLang
    final Map<String, Map> translations
    (defaultLang, translations) = new TranslationManager().getAllTranslations()
    project.translation.defaultLang = defaultLang

    generateAllLanguageResources(translations)
}

void generateAllLanguageResources(Map<String, Map> translations) {
    translations.each { locale, jsonSection ->
        generateStrResources(locale, jsonSection)
    }
}

private void generateStrResources(String locale, Map jsonSection) {
    def sw = new StringWriter()
    def xml = new MarkupBuilder(sw)

    xml.resources() {
        jsonSection.each { String section, content ->
            content.each { String key, translation ->
                if (key != "privacyPolicyText" && key != "termsConditionsText") {
                    string(
                            name: "${section.trim()}_${key.trim()}",
                            //do all your conversions with translation variable here
                    )
                }
            }
        }
    }

    def stringsFile = new File(project.translation.dir, project.translation.getStrPath(locale))
    stringsFile.parentFile.mkdirs()

    stringsFile.writeLn "<?xml version=\"1.0\" encoding=\"utf-8\"?>"
    stringsFile << "<!-- This file is auto-generated, do not make changes in it -->"
    stringsFile << ""
    stringsFile << sw.toString()
}

class TranslationManager {
    def getAllTranslations() {
        ArrayList allLanguages = getAllLanguages()
        HashMap map = new HashMap()
        def defaultLang

        allLanguages.each { lang ->
            if (lang.is_default) defaultLang = lang
            map[lang.locale] = getLanguage(lang.id, lang.locale)
        }

        return [defaultLang, allLanguages, map]
    }

    private static ArrayList getAllLanguages() {
        // Get our json string from the provided url
        String jsonString = //make your request here (analogue of LangsApi.getLanguages)

        if (jsonString.isEmpty()) {
            println("Got no languages, returning empty languages map")
            return new ArrayList()
        }

        // Pull our json data from that json string we get
        return new JsonSlurper().parseText(jsonString).languages
    }

    private static Object getLanguage(int id, String lang) {
        final String languageDetailUrl = //make your request here (analogue of LangsApi.getTranslations)
        // Get our json string from the provided url
        String jsonString = Util.getTextFromUrl(languageDetailUrl, lang)

        if (jsonString.isEmpty()) {
            println("Could not fetch language id: " + id)
            return null
        }

        // Pull our json data from that json string we get
        return new JsonSlurper().parseText(jsonString).data
    }
}

task updateTranslation {
    group = "transifex"
    doLast {
        generateTranslationClass()
    }
}