Main.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

class Main {
	static final int LOG_DEBUG = 0;
	static final int LOG_ERROR = 1;
	static final String[] logLevelStrs = {"debug", "error"};

	enum TargetLanguage { JAVA, SWIFT }

	// **** CONFIG ****
	static final int logLevel = LOG_DEBUG;

	static final TargetLanguage targetLanguage = TargetLanguage.SWIFT;

	static final int numVerticesPerLine = 3;
	static final int numFacesPerLine = 8;

	static final boolean xyzrgbEnable = true;
	static final int numVertexColorsPerLine = 4; // Effective only if targetLanguage == JAVA and xyzrgbEnable = true
	// ****************

	static class _3DModel {
		String[][] vertices = {};
		int[][] faces = {};
		String[][] vertexColors = {};

		void printOutputArrays() {
			if (targetLanguage == TargetLanguage.JAVA) {
				System.out.println("final float[] vertices = {");
				for (int i = 0; i < vertices.length; i += numVerticesPerLine) {
					for (int j = 0; j < numVerticesPerLine && i + j < vertices.length; j++)
						System.out.print("\t" + String.join("f, ", vertices[i + j]) + "f,");
					System.out.println();
				}
				System.out.println("};");

				System.out.println("\nfinal short[] faces = {");
				for (int i = 0; i < faces.length; i += numFacesPerLine) {
					for (int j = 0; j < numFacesPerLine && i + j < faces.length; j++)
						System.out.print("\t" + faces[i + j][0] + ", " + faces[i + j][1] + ", " + faces[i + j][2] + ",");
					System.out.println();
				}
				System.out.println("};");

				if (xyzrgbEnable) {
					System.out.println("\nfinal float[] vertexColors = {");
					for (int i = 0; i < vertexColors.length; i += numVertexColorsPerLine) {
						for (int j = 0; j < numVertexColorsPerLine && i + j < vertexColors.length; j++)
							System.out.print("\t" + String.join("f, ", vertexColors[i + j]) + "f,");
						System.out.println();
					}
					System.out.println("};");
				}
			} else { // SWIFT
				System.out.println("let vertices: [SIMD3<Float>] = [");
				for (int i = 0; i < vertices.length; i += numVerticesPerLine) {
					for (int j = 0; j < numVerticesPerLine && i + j < vertices.length; j++)
						System.out.print("\t[" + String.join(", ", vertices[i + j]) + "],");
					System.out.println();
				}
				System.out.println("]");

				System.out.println("\nlet faces: [UInt16] = [");
				for (int i = 0; i < faces.length; i += numFacesPerLine) {
					for (int j = 0; j < numFacesPerLine && i + j < faces.length; j++)
						System.out.print("\t" + faces[i + j][0] + ", " + faces[i + j][1] + ", " + faces[i + j][2] + ",");
					System.out.println();
				}
				System.out.println("]");

				if (xyzrgbEnable) {
					System.out.println("\nlet vertexColors: [SIMD3<Float>] = [");
					for (int i = 0; i < vertexColors.length; i += numVertexColorsPerLine) {
						for (int j = 0; j < numVertexColorsPerLine && i + j < vertexColors.length; j++)
							System.out.print("\t[" + String.join(", ", vertexColors[i + j]) + "],");
						System.out.println();
					}
					System.out.println("]");
				}
			}
		}
	}

	public static void main(String[] args) {
		if (args.length == 0) {
			logMsg(LOG_ERROR, "Input file path not provided");
			return;
		}

		final File inputFile = new File(args[0]);
		final Scanner scanner;
		try {
			scanner = new Scanner(inputFile);
		} catch (FileNotFoundException e) {
			logMsg(LOG_ERROR, "Failed to find input file (FileNotFoundException)");
			return;
		}

		final _3DModel model = OBJWavefrontParse(scanner);
		if (model == null)
			return;

		System.out.println("\n**** RESULT ****");

		model.printOutputArrays();

		System.out.println("****************");
	}

	//
	// Prints / discards a log message based on the logLevel class-variable.
	//
	static void logMsg(int msgLogLevel, String msg) {
		if (msgLogLevel >= logLevel)
			System.out.println(logLevelStrs[msgLogLevel] + ": " + msg);
	}

	//
	// Parses the contents of scanner as an OBJ file using the config
	// class-variables (such as xyzrgbEnable) and returns a _3DModel based
	// on the OBJ content, or null on error.
	//
	static _3DModel OBJWavefrontParse(Scanner scanner) {
		_3DModel model = new _3DModel();

		for (int lineNr = 1; scanner.hasNextLine(); lineNr++) {
			final String line = scanner.nextLine();
			logMsg(LOG_DEBUG, "Parsing line " + lineNr);

			final int spaceIndex = line.indexOf(' ');
			if (spaceIndex < 1)
				continue;

			int sepIndex;
			switch (line.substring(0, spaceIndex)) {
			case "v":
				model.vertices = Arrays.copyOf(model.vertices, model.vertices.length + 1);
				model.vertices[model.vertices.length - 1] = new String[3];

				sepIndex = spaceIndex;
				for (int i = 0; i < 3; i++) {
					int nextSepIndex = line.indexOf(' ', sepIndex + 1);
					if (nextSepIndex == -1)
						nextSepIndex = line.length();

					model.vertices[model.vertices.length - 1][i] = line.substring(sepIndex + 1, nextSepIndex);
					sepIndex = nextSepIndex;
				}

				if (xyzrgbEnable) {
					model.vertexColors = Arrays.copyOf(model.vertexColors, model.vertexColors.length + 1);
					model.vertexColors[model.vertexColors.length - 1] = new String[3];

					for (int i = 0; i < 3; i++) {
						int nextSepIndex = line.indexOf(' ', sepIndex + 1);
						if (nextSepIndex == -1)
							nextSepIndex = line.length();
				
						model.vertexColors[model.vertexColors.length - 1][i] = line.substring(sepIndex + 1, nextSepIndex);
						sepIndex = nextSepIndex;
					}
				}

				continue;
			case "f":
				model.faces = Arrays.copyOf(model.faces, model.faces.length + 1);
				model.faces[model.faces.length - 1] = new int[3];

				sepIndex = spaceIndex;
				for (int i = 0; i < 3; i++) {
					int nextSepIndex = line.indexOf(' ', sepIndex + 1);
					if (nextSepIndex == -1)
						nextSepIndex = line.length();
					
					String entryStr = line.substring(sepIndex + 1, nextSepIndex);	
					final int slashIndex = entryStr.indexOf('/');
					if (slashIndex != -1)
						entryStr = entryStr.substring(0, slashIndex);

					try {
						model.faces[model.faces.length - 1][i] = Integer.parseInt(entryStr) - 1;
					} catch (NumberFormatException e) {
						logMsg(LOG_ERROR, "NumberFormatException on an entry in a face");
						return null;
					}

					sepIndex = nextSepIndex;
				}
				continue;
			}
			
			logMsg(LOG_DEBUG, "Skipping line starting with \"" + line.substring(0, spaceIndex) + "\"");
		}
		
		return model;
	}
}