package moe.nea.firmament.init;


import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class AutoDiscoveryPlugin {
    private static final List<AutoDiscoveryPlugin> mixinPlugins = new ArrayList<>();

    public static List<AutoDiscoveryPlugin> getMixinPlugins() {
        return mixinPlugins;
    }

    private String mixinPackage;

    public void setMixinPackage(String mixinPackage) {
        this.mixinPackage = mixinPackage;
        mixinPlugins.add(this);
    }

    /**
     * Resolves the base class root for a given class URL. This resolves either the JAR root, or the class file root.
     * In either case the return value of this + the class name will resolve back to the original class url, or to other
     * class urls for other classes.
     */
    public URL getBaseUrlForClassUrl(URL classUrl) {
        String string = classUrl.toString();
        if (classUrl.getProtocol().equals("jar")) {
            try {
                return new URL(string.substring(4).split("!")[0]);
            } catch (MalformedURLException e) {
                throw new RuntimeException(e);
            }
        }
        if (string.endsWith(".class")) {
            try {
                return new URL(string.replace("\\", "/")
                                     .replace(getClass().getCanonicalName()
                                                        .replace(".", "/") + ".class", ""));
            } catch (MalformedURLException e) {
                throw new RuntimeException(e);
            }
        }
        return classUrl;
    }

    /**
     * Get the package that contains all the mixins. This value is set using {@link #setMixinPackage}.
     */
    public String getMixinPackage() {
        return mixinPackage;
    }

    /**
     * Get the path inside the class root to the mixin package
     */
    public String getMixinBaseDir() {
        return mixinPackage.replace(".", "/");
    }

    /**
     * A list of all discovered mixins.
     */
    private List<String> mixins = null;

    /**
     * Try to add mixin class ot the mixins based on the filepath inside of the class root.
     * Removes the {@code .class} file suffix, as well as the base mixin package.
     * <p><b>This method cannot be called after mixin initialization.</p>
     *
     * @param className the name or path of a class to be registered as a mixin.
     */
    public void tryAddMixinClass(String className) {
        if (!className.endsWith(".class")) return;
        String norm = (className.substring(0, className.length() - ".class".length()))
            .replace("\\", "/")
            .replace("/", ".");
        if (norm.startsWith(getMixinPackage() + ".") && !norm.endsWith(".")) {
            mixins.add(norm.substring(getMixinPackage().length() + 1));
        }
    }

    private void tryDiscoverFromContentFile(URL url) {
        Path file;
        try {
            file = Paths.get(getBaseUrlForClassUrl(url).toURI());
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
        System.out.println("Base directory found at " + file);
        if (!Files.exists(file)) {
            System.out.println("Skipping non-existing mixin root: " + file);
            return;
        }
        if (Files.isDirectory(file)) {
            walkDir(file);
        } else {
            walkJar(file);
        }
        System.out.println("Found mixins: " + mixins);

    }

    /**
     * Search through the JAR or class directory to find mixins contained in {@link #getMixinPackage()}
     */
    public List<String> getMixins() {
        if (mixins != null) return mixins;
        System.out.println("Trying to discover mixins");
        mixins = new ArrayList<>();
        URL classUrl = getClass().getProtectionDomain().getCodeSource().getLocation();
        System.out.println("Found classes at " + classUrl);
        tryDiscoverFromContentFile(classUrl);
        var classRoots = System.getProperty("firmament.classroots");
        if (classRoots != null && !classRoots.isBlank()) {
            System.out.println("Found firmament class roots: " + classRoots);
            for (String s : classRoots.split(File.pathSeparator)) {
                if (s.isBlank()) {
                    continue;
                }
                try {
                    tryDiscoverFromContentFile(new File(s).toURI().toURL());
                } catch (MalformedURLException e) {
                    throw new RuntimeException(e);
                }
            }
        }
        return mixins;
    }

    /**
     * Search through directory for mixin classes based on {@link #getMixinBaseDir}.
     *
     * @param classRoot The root directory in which classes are stored for the default package.
     */
    private void walkDir(Path classRoot) {
        System.out.println("Trying to find mixins from directory");
        var path = classRoot.resolve(getMixinBaseDir());
        if (!Files.exists(path)) return;
        try (Stream<Path> classes = Files.walk(path)) {
            classes.map(it -> classRoot.relativize(it).toString())
                   .forEach(this::tryAddMixinClass);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Read through a JAR file, trying to find all mixins inside.
     */
    private void walkJar(Path file) {
        System.out.println("Trying to find mixins from jar file");
        try (ZipInputStream zis = new ZipInputStream(Files.newInputStream(file))) {
            ZipEntry next;
            while ((next = zis.getNextEntry()) != null) {
                tryAddMixinClass(next.getName());
                zis.closeEntry();
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

}