Widerhall/src/main/java/de/srsoftware/widerhall/web/TemplateServlet.java

package de.srsoftware.widerhall.web;

import de.srsoftware.widerhall.Configuration;
import org.stringtemplate.v4.ST;
import org.stringtemplate.v4.STGroup;
import org.stringtemplate.v4.STRawGroupDir;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.Map;

import static de.srsoftware.widerhall.Util.t;

public abstract class TemplateServlet extends HttpServlet {
    private STGroup templates;
    private final String baseDir;

    public TemplateServlet(){
        var config = Configuration.instance();
        baseDir = config.baseDir();
        loadTemplates();
    }

    protected ST getTemplate(String name){
        return templates.getInstanceOf(name);
    }

    protected String loadFile(String filename, HttpServletResponse resp) {
        var path = String.join(File.separator,baseDir,"static",filename);
        var file = new File(path);
        if (!file.exists()) return t("File {} does not exist!",filename);
        try {
            var content = Files.readAllBytes(file.toPath());
            var out = resp.getOutputStream();
            out.write(content);
            out.flush();
        } catch (IOException e) {
            return t("Failed to load file '{}'!",filename);
        }
        return null;
    }

    protected String loadTemplate(String path, Map<String, ? extends Object> data, HttpServletResponse resp) {
        var template = templates.getInstanceOf(path);
        if (template != null){
            try {
                resp.setCharacterEncoding("UTF-8");
                template.add("data",data);
                resp.getWriter().println(template.render());
                return null;
            } catch (IOException e) {
                return t("Failed to load template '{}'!",path);
            }
        }
        return t("No template for path '{}'!",path);
    }

    protected void loadTemplates() {
        var templateDir = String.join(File.separator,baseDir,"static","templates");
        templates = new STRawGroupDir(templateDir,'«','»');
    }
}