package nonreg;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Collection;
import java.util.List;

import net.sourceforge.plantuml.FileFormat;
import net.sourceforge.plantuml.FileFormatOption;
import net.sourceforge.plantuml.SourceStringReader;
import net.sourceforge.plantuml.TitledDiagram;
import net.sourceforge.plantuml.core.DiagramDescription;

/*
 * All non-regression tests must extends BasicTest class.
 * 
 * The tests must have a single test method that call the 'checkImage()' method.
 * Diagram to be tested must be stored in the test itself, separated by triple-quoted strings
 * The expected result (build using UGraphicDebug) is stored in a class xxxxResult.java, also separated by triple-quoted strings.
 * 
 */
public class BasicTest {

	private static final String TRIPLE_QUOTE = "\"\"\"";

	private static final Charset UTF8 = Charset.forName("UTF-8");

	private static final boolean FORCE_RESULT_GENERATION = false;
	private static final boolean ENABLE_RESULT_GENERATION_IF_NONE_PRESENT = true;

	public BasicTest() {
		// We want a fully portable way of non regression test, so we force the usage of
		// Smetana. It probably means that non regression tests on
		// class/component/usecase are not complete.
		TitledDiagram.FORCE_SMETANA = true;
	}

	protected void checkImage(final String expectedDescription) throws IOException, UnsupportedEncodingException {
		final String actualResult = runPlantUML(expectedDescription);
		if (FORCE_RESULT_GENERATION
				|| (ENABLE_RESULT_GENERATION_IF_NONE_PRESENT && Files.exists(getResultFile()) == false)) {
			generatedResultJavaFile(actualResult, actualResult.getBytes(UTF8));
		}
		final String imageExpectedResult = readTripleQuotedString(getResultFile());
		assertEquals(imageExpectedResult, actualResult);
	}

	private void generatedResultJavaFile(String actualResult, byte[] bytes) throws IOException {

		try (BufferedWriter writer = Files.newBufferedWriter(getResultFile(), StandardCharsets.UTF_8)) {
			writer.write("package " + getPackageName() + ";\n");
			writer.write("\n");
			writer.write("public class " + getClass().getSimpleName() + "Result {\n");
			writer.write("}\n");
			writer.write("/*\n");
			writer.write(TRIPLE_QUOTE + "\n");
			writer.write(actualResult);
			writer.write(TRIPLE_QUOTE + "\n");
			writer.write("*/");
		}

	}

	protected String getLocalFolder() {
		return "test/" + getPackageName().replace(".", "/");
	}

	private String getPackageName() {
		return getClass().getPackage().getName();
	}

	protected Path getResultFile() {
		return Paths.get(getLocalFolder(), getClass().getSimpleName() + "Result.java");
	}

	protected Path getDiagramFile() {
		return Paths.get(getLocalFolder(), getClass().getSimpleName() + ".java");
	}

	protected String runPlantUML(String expectedDescription) throws IOException, UnsupportedEncodingException {
		final String diagramText = readTripleQuotedString(getDiagramFile());
		final SourceStringReader ssr = new SourceStringReader(diagramText, "UTF-8");
		final ByteArrayOutputStream baos = new ByteArrayOutputStream();
		final DiagramDescription diagramDescription = ssr.outputImage(baos, 0, new FileFormatOption(FileFormat.DEBUG));
		assertEquals(expectedDescription, diagramDescription.getDescription(), "Bad description");

		return new String(baos.toByteArray(), UTF8);
	}

	protected String readTripleQuotedString(Path path) throws IOException {
		assertTrue(Files.exists(path), "Cannot find " + path);
		assertTrue(Files.isReadable(path), "Cannot read " + path);
		final List<String> allLines = Files.readAllLines(path, UTF8);
		final int first = allLines.indexOf(TRIPLE_QUOTE);
		final int last = allLines.lastIndexOf(TRIPLE_QUOTE);
		assertTrue(first != -1);
		assertTrue(last != -1);
		assertTrue(last > first);
		return packString(allLines.subList(first + 1, last));
	}

	protected String packString(Collection<String> list) {
		final StringBuilder sb = new StringBuilder();
		for (String s : list) {
			sb.append(s);
			sb.append("\n");
		}
		return sb.toString();
	}

}