Notification.java

// Real usage

WhiTemplater.Formatter FEATURED_FORMAT = new WhiTemplater.Formatter() {
    @Override
    public String format(Object value) {
        return "<b>" + String.valueOf(value)+ "</b>";
    }
};

WhiTemplater.Formatter NORMAL_FORMAT = new WhiTemplater.Formatter() {
    @Override
    public String format(Object value) {
        return "<b><font color='#FD93B1'>" + String.valueOf(value)+ "</font></b>";
    }
};

// later on

WhiTemplater.Formatter formatter = isFeatured() ? FEATURED_FORMAT : NORMAL_FORMAT;
String template = descriptionHash.getString("template");
setMessage(WhiTemplater.compile(template, descriptionHash, formatter));

WhiTemplater.java

package com.weheartit.util;

import org.json.JSONException;
import org.json.JSONObject;

import java.text.ParseException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

// Turns strings with mustache variables (like {{username}}) into readable strings where the replacement
// for the variable is looked inside a JSON context.
//
// If we have "{{username}} is now following you" and the context has the 'username' key, this will
// replace `{{username}}` with the value for that key on the context.
//
// This is the simplest Mustache replacement, so having a complex library for that was not
// worth it for now, specially when the library (jmustache) has failing tests.
//
// on matcher.group(1) we'll have '{{username}}' and on matcher.group(2) we'll have 'username',
// we have to quote '{{username}}' since "{{" is invalid in Java regexps.
//
// More examples can be found on the test files.
public class WhiTemplater {
    final static Pattern mustachePattern = Pattern.compile("(\\{\\{([.[^\\}\\}]]+)\\}\\})");

    /** Handles converting objects to strings when rendering templates. */
    public interface Formatter {
        String format (Object value);
    };

    protected static final Formatter DEFAULT_FORMATTER = new Formatter() {
        public String format (Object value) {
            return String.valueOf(value);
        }
    };

    public final static String compile(String template, JSONObject context) throws JSONException, ParseException {
        return compile(template, context, DEFAULT_FORMATTER);
    }

    public final static String compile(String template, JSONObject context, Formatter formatter) throws JSONException, ParseException {
        Matcher matcher = mustachePattern.matcher(template);
        while(matcher.find()){
            String stringToReplace = Pattern.quote(matcher.group(1));
            if(context.has(matcher.group(2))){
                String replaceWith = formatter.format(context.getString(matcher.group(2)));
                template = template.replaceAll(stringToReplace, replaceWith);
            }
        }
        return template;
    }
}

WhiTemplaterTest.java

package com.weheartit.model;

import static org.junit.Assert.*;
import static org.junit.Assert.assertThat;
import static org.hamcrest.core.IsEqual.equalTo;

import org.junit.Test;
import org.junit.runner.RunWith;

import com.weheartit.WeHeartItTestRunner;
import com.weheartit.util.WhiTemplater;

import org.json.JSONException;
import org.json.JSONObject;

import java.lang.Object;
import java.lang.Override;
import java.lang.String;
import java.text.ParseException;

import dalvik.annotation.TestTarget;

@RunWith(WeHeartItTestRunner.class)
public class WhiTemplaterTest {

    @Test
    public void itCompilesTemplates() throws JSONException, ParseException{
        JSONObject context = new JSONObject("{\"username\":\"nhocki\"}");
        String result = WhiTemplater.compile("{{username}} is now following you", context);
        assertThat(result, equalTo("nhocki is now following you"));
    }

    @Test
    public void itAcceptsAFormatterObject() throws JSONException, ParseException{
        JSONObject context = new JSONObject("{\"username\":\"nhocki\"}");

        WhiTemplater.Formatter f = new WhiTemplater.Formatter() {
            @Override
            public String format(Object value) {
                return "<b>" + String.valueOf(value) + "</b>";
            }
        };

        String result = WhiTemplater.compile("{{username}} is now following you", context, f);
        assertThat(result, equalTo("<b>nhocki</b> is now following you"));
    }

    @Test
    public void itReplacesMultipleVariablesMultipleTimes() throws JSONException, ParseException{
        JSONObject context = new JSONObject("{\"username\":\"nhocki\", \"name\": \"Nicolas\"}");
        String result = WhiTemplater.compile("{{username}} {{name}} {{username}} {{name}}", context);
        assertThat(result, equalTo("nhocki Nicolas nhocki Nicolas"));
    }

    @Test
    public void itDoentDieWithNonExistentVariables() throws JSONException, ParseException{
        JSONObject context = new JSONObject("{\"username\":\"nhocki\"}");
        String result = WhiTemplater.compile("{{idontexist}} yeah", context);
        assertThat(result, equalTo("{{idontexist}} yeah"));
    }

    @Test
    public void itWorksWithTemplatesWithoutVariables() throws JSONException, ParseException{
        String result = WhiTemplater.compile("yeah", new JSONObject("{}"));
        assertThat(result, equalTo("yeah"));

        result = WhiTemplater.compile("oh yeah", new JSONObject("{\"name\": \"Nicolas\"}"));
        assertThat(result, equalTo("oh yeah"));
    }
}