backbone for i18n support (#55)

src/main/java/com/commafeed/frontend/utils/InternationalizationDevelopmentFilter.java

@@ -0,0 +1,132 @@
+package com.commafeed.frontend.utils;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+import java.util.Properties;
+import java.util.ResourceBundle;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpServletResponseWrapper;
+
+import org.apache.commons.io.IOUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.commafeed.frontend.CommaFeedSession;
+
+/**
+ * Replace variables from templates on the fly in dev mode only. In production
+ * the substitution is done at build-time.
+ * 
+ */
+public class InternationalizationDevelopmentFilter implements Filter {
+
+	private static Logger log = LoggerFactory
+			.getLogger(InternationalizationDevelopmentFilter.class);
+
+	private boolean production = true;
+
+	@Override
+	public void doFilter(ServletRequest request, ServletResponse response,
+			FilterChain chain) throws IOException, ServletException {
+
+		if (production) {
+			chain.doFilter(request, response);
+			return;
+		}
+
+		final ServletOutputStream wrapper = new ServletOutputStreamWrapper();
+		ServletResponse interceptor = new HttpServletResponseWrapper(
+				(HttpServletResponse) response) {
+
+			@Override
+			public ServletOutputStream getOutputStream() throws IOException {
+				return wrapper;
+			}
+		};
+		chain.doFilter(request, interceptor);
+		Locale locale = CommaFeedSession.get().getLocale();
+
+		byte[] bytes = translate(wrapper.toString(), locale).getBytes();
+		response.getOutputStream().write(bytes);
+		response.setContentLength(bytes.length);
+		response.getOutputStream().close();
+
+	}
+
+	private String translate(String content, Locale locale) {
+		Properties props = new Properties();
+		InputStream is = null;
+		try {
+			is = getClass().getResourceAsStream(
+					"/i18n/" + locale.getLanguage() + ".properties");
+			if (is == null) {
+				is = getClass().getResourceAsStream("/i18n/en.properties");
+			}
+			if (is == null) {
+				throw new Exception("Locale file not found for locale "
+						+ locale.getLanguage());
+			}
+			props.load(is);
+		} catch (Exception e) {
+			log.error(e.getMessage(), e);
+		} finally {
+			IOUtils.closeQuietly(is);
+		}
+
+		return replace(content, props);
+	}
+
+	private static final Pattern PATTERN = Pattern.compile("\\$\\{(.+?)\\}");
+
+	public String replace(String content, Properties props) {
+		Matcher m = PATTERN.matcher(content);
+		StringBuffer sb = new StringBuffer();
+		while (m.find()) {
+			String var = m.group(1);
+			Object replacement = props.get(var);
+			m.appendReplacement(sb, replacement.toString());
+		}
+		m.appendTail(sb);
+		return sb.toString();
+	}
+
+	@Override
+	public void init(FilterConfig filterConfig) throws ServletException {
+		String prod = ResourceBundle.getBundle("application").getString(
+				"production");
+		production = Boolean.valueOf(prod);
+	}
+
+	@Override
+	public void destroy() {
+		// do nothing
+	}
+
+	private static class ServletOutputStreamWrapper extends ServletOutputStream {
+
+		private ByteArrayOutputStream baos = new ByteArrayOutputStream();
+
+		@Override
+		public void write(int b) throws IOException {
+			baos.write(b);
+		}
+
+		@Override
+		public String toString() {
+			return baos.toString();
+		}
+	}
+
+}