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package com.pojosontheweb.ttt;

import java.io.IOException;
import java.io.Writer;

import static com.pojosontheweb.ttt.Util.toRtExNoResult;

/**
 * Base template class. Defines the policy for writing
 * to the output from expressions :
 * 
 *     null writes nothing
 *     objects implementing ITemplate are rendered
 *     objects implementing IBodyTemplate are opened
 *     Strings are rendered as is
 *     other objects are rendered using their toString() method
 * 
 */
public abstract class Template implements ITemplate {

    protected void write(Writer out, Object o) {
        toRtExNoResult(() -> {
			if (o != null) {
				if (o instanceof ITemplate) {
					((ITemplate) o).render(out);
				} else if (o instanceof String) {
					out.write((String) o);
				} else if (o instanceof IBodyTemplate) {

					IBodyTemplate st = (IBodyTemplate)o;
					// call the open method on the sub template
					// and let it manage stuff. SubTemplate is an
					// auto-closable and should be used with
					// a try-resource block, therefore we do not
					// need to call close ourselves...
					st.open((TttWriter)out);

				} else {
					out.write(o.toString());
				}
			}
        });
    }

    protected void write(Writer out, Object first, Object... rest) {
        write(out, first);
        if (rest != null) {
            for (Object o : rest) {
                write(out, o);
            }
        }
    }

    @Override
    public final void render(Writer out) {
        // wrap the supplied writer into a TttWriter
        // if not already done...
        final TttWriter tw;
        if (out instanceof TttWriter) {
            tw = (TttWriter)out;
        } else {
            tw = new TttWriter(out);
        }
        toRtExNoResult("error while rendering the template", () -> doRender(tw));
    }

    protected abstract void doRender(TttWriter tw) throws Exception;
}