(#10) Added .obj writer (implementation not complete)

src/main/java/tech/fastj/resources/models/ObjUtil.java

@@ -0,0 +1,134 @@
+package tech.fastj.resources.models;
+
+import tech.fastj.engine.CrashMessages;
+import tech.fastj.math.Pointf;
+import tech.fastj.graphics.game.Model2D;
+import tech.fastj.graphics.game.Polygon2D;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.List;
+
+public class ObjUtil {
+
+    private static final String LineSeparator = System.lineSeparator();
+
+    private ObjUtil() {
+        throw new java.lang.IllegalStateException();
+    }
+
+    public static Polygon2D[] parse(List<String> lines) {
+        return null;
+    }
+
+    public static void write(Path destinationPath, Model2D model) {
+        StringBuilder fileContents = new StringBuilder();
+        writeTimestamp(fileContents);
+
+        int vertexCount = 0;
+
+        for (int i = 0; i < model.getPolygons().length; i++) {
+            writeVertexes(fileContents, model.getPolygons()[i]);
+        }
+
+        writeVertexTextures(fileContents);
+
+        for (int i = 0; i < model.getPolygons().length; i++) {
+            Polygon2D polygon = model.getPolygons()[i];
+            writeObject(fileContents, polygon, i + 1);
+            writeFaces(fileContents, polygon, vertexCount);
+
+            vertexCount += polygon.getPoints().length;
+        }
+
+        try {
+            Files.writeString(destinationPath, fileContents, StandardCharsets.US_ASCII);
+        } catch (IOException exception) {
+            throw new IllegalStateException(CrashMessages.theGameCrashed("a ." + SupportedModelFormats.Obj + " file writing error."), exception);
+        }
+    }
+
+    private static void writeTimestamp(StringBuilder fileContents) {
+        fileContents.append("# Generated by the FastJ Game Engine https://github.com/fastjengine/FastJ")
+                .append(LineSeparator)
+                .append("# Timestamp: ")
+                .append(new SimpleDateFormat("dd-MM-yyyy HH:mm:ss").format(new Date()))
+                .append(LineSeparator)
+                .append(LineSeparator);
+    }
+
+    private static void writeVertexes(StringBuilder fileContents, Polygon2D polygon) {
+        for (int j = 0; j < polygon.getPoints().length; j++) {
+            Pointf vertex = polygon.getPoints()[j];
+            fileContents.append(ParsingKeys.Vertex)
+                    .append(' ')
+                    .append(String.format("%4f", vertex.x))
+                    .append(' ')
+                    .append(String.format("%4f", vertex.y))
+                    .append(' ')
+                    .append(String.format("%4f", 0f))
+                    .append(LineSeparator);
+        }
+    }
+
+    private static void writeVertexTextures(StringBuilder fileContents) {
+        fileContents.append(LineSeparator);
+        fileContents.append(ParsingKeys.VertexTexture)
+                .append(' ')
+                .append(0)
+                .append(' ')
+                .append(0)
+                .append(LineSeparator);
+        fileContents.append(ParsingKeys.VertexTexture)
+                .append(' ')
+                .append(1)
+                .append(' ')
+                .append(0)
+                .append(LineSeparator);
+        fileContents.append(ParsingKeys.VertexTexture)
+                .append(' ')
+                .append(1)
+                .append(' ')
+                .append(1)
+                .append(LineSeparator);
+        fileContents.append(ParsingKeys.VertexTexture)
+                .append(' ')
+                .append(0)
+                .append(' ')
+                .append(1)
+                .append(LineSeparator)
+                .append(LineSeparator);
+    }
+
+    private static void writeObject(StringBuilder fileContents, Polygon2D polygon, int polygonIndex) {
+        fileContents.append(ParsingKeys.ObjectName)
+                .append(' ')
+                .append("Polygon2D_")
+                .append(polygonIndex)
+                .append(LineSeparator);
+    }
+
+    private static void writeFaces(StringBuilder fileContents, Polygon2D polygon, int vertexCount) {
+        fileContents.append(ParsingKeys.ObjectFace);
+        for (int i = 1; i <= polygon.getPoints().length; i++) {
+            fileContents.append(' ').append(vertexCount + i);
+        }
+        fileContents.append(LineSeparator).append(LineSeparator);
+    }
+
+    public static class ParsingKeys {
+        private ParsingKeys() {
+            throw new java.lang.IllegalStateException();
+        }
+
+        public static final String Empty = "";
+        public static final String Vertex = "v";
+        public static final String VertexTexture = "vt";
+        public static final String ObjectName = "g";
+        public static final String ObjectFace = "f";
+    }
+}