Respackopts/src/main/java/io/gitlab/jfronny/respackopts/filters/DirFilterEvents.java

package io.gitlab.jfronny.respackopts.filters;

import io.gitlab.jfronny.libjf.LibJf;
import io.gitlab.jfronny.libjf.ResourcePath;
import io.gitlab.jfronny.libjf.data.manipulation.api.UserResourceEvents;
import io.gitlab.jfronny.respackopts.Respackopts;
import io.gitlab.jfronny.respackopts.filters.util.DirRpoResult;
import io.gitlab.jfronny.respackopts.gson.AttachmentHolder;
import io.gitlab.jfronny.respackopts.model.DirRpo;
import io.gitlab.jfronny.respackopts.model.GC_DirRpo;
import io.gitlab.jfronny.respackopts.model.cache.CacheKey;
import io.gitlab.jfronny.respackopts.model.cache.CachedPackState;
import io.gitlab.jfronny.respackopts.model.enums.PackCapability;
import io.gitlab.jfronny.respackopts.muscript.RespackoptsFS;
import io.gitlab.jfronny.respackopts.util.MetaCache;
import net.minecraft.resource.*;
import net.minecraft.util.Identifier;

import java.io.*;
import java.util.*;

public enum DirFilterEvents implements UserResourceEvents.Open, UserResourceEvents.FindResource {
    INSTANCE;

    public static void init() {
        UserResourceEvents.OPEN.register(INSTANCE);
        UserResourceEvents.FIND_RESOURCE.register(INSTANCE);
    }

    @Override
    public InputSupplier<InputStream> open(ResourceType type, Identifier id, InputSupplier<InputStream> previous, ResourcePack pack) {
        if (!MetaCache.hasCapability(pack, PackCapability.DirFilter)) return previous;
        String path = new ResourcePath(type, id).getName();
        List<DirRpo> rpo = findDirRpos(pack, parent(path));
        CacheKey key = MetaCache.getKeyByPack(pack);
        RespackoptsFS fs = new RespackoptsFS(pack);
        //TODO use pattern matching for switch
        DirRpoResult result = DirRpoResult.compute(path, rpo, key, fs);
        if (result == DirRpoResult.ORIGINAL) return previous; // Using original file
        if (result == DirRpoResult.IGNORE) return null; // No fallback
        // Use fallback
        DirRpoResult.Replacement replacement = (DirRpoResult.Replacement) result;
        String fallback = replacement.toFallback(path);
        MetaCache.addDependency(key, path, fallback);
        return fs.open(fallback);
    }

    @Override
    public ResourcePack.ResultConsumer findResources(ResourceType type, String namespace, String prefix, ResourcePack.ResultConsumer previous, ResourcePack pack) {
        // Warning: the Identifiers here DON'T CONTAIN THE TYPE!
        // Therefore, it needs to be added when calling a method that generates a ResourcePath!
        if (!MetaCache.hasCapability(pack, PackCapability.DirFilter)) return previous;
        boolean dirFilterAdditive = MetaCache.hasCapability(pack, PackCapability.DirFilterAdditive);
        String searchPrefix = type.getDirectory() + "/" + namespace + "/" + prefix;
        Set<String> additionalSearched = new HashSet<>();
        CacheKey key = MetaCache.getKeyByPack(pack);
        RespackoptsFS fs = new RespackoptsFS(pack);
        return (identifier, value) -> {
            String path = path(type, identifier);
            //TODO use pattern matching for switch
            List<DirRpo> relevantRpos = findDirRpos(pack, parent(path));
            DirRpoResult result = DirRpoResult.compute(path, relevantRpos, key, fs);
            if (result == DirRpoResult.ORIGINAL) { // Using original file
                previous.accept(identifier, value);
                return;
            }
            if (result == DirRpoResult.IGNORE) return; // No fallback
            // New search for fallback path
            DirRpoResult.Replacement replacement = (DirRpoResult.Replacement) result;
            String newPath = replacement.toFallback(path);
            if (newPath.split("/", 3).length != 3) {
                Respackopts.LOGGER.error("Directory fallback path MUST be long enough to support representation as identifier (3 segments), but is too short: " + newPath);
                return;
            }
            if (!dirFilterAdditive) {
                // Only return this single result, don't search for others
                MetaCache.addDependency(key, path, newPath);
                previous.accept(identifier, fs.open(newPath));
                return;
            }
            // Find other files in the fallback directory
            String fallbackDir = replacement.fallback.prefix();
            if (!additionalSearched.add(fallbackDir)) return; // Already searched
            int prefixSize = replacement.original.prefix().length();
            if (prefixSize < searchPrefix.length()) {
                if (!searchPrefix.startsWith(replacement.original.prefix())) {
                    Respackopts.LOGGER.error("Unexpected prefix path " + replacement.original.prefix() + " for search prefix " + searchPrefix + ", skipping");
                    return;
                }
                fallbackDir += searchPrefix.substring(prefixSize);
            } else if (!replacement.original.prefix().startsWith(searchPrefix)) {
                Respackopts.LOGGER.error("Unexpected prefix path " + replacement.original.prefix() + " for search prefix " + searchPrefix + ", skipping");
                return;
            }
            if (fallbackDir.split("/", 3).length != 3) {
                Respackopts.LOGGER.error("Directory fallback path MUST be long enough to support representation as identifier (3 segments), but is too short: " + fallbackDir);
                return;
            }
            ResourcePath rp = new ResourcePath(fallbackDir);
            pack.findResources(rp.getType(), rp.getId().getNamespace(), rp.getId().getPath(), (resource, resVal) -> {
                String fallbackPath = path(rp.getType(), resource);
                String orig = replacement.toOriginal(fallbackPath);
                MetaCache.addDependency(key, orig, fallbackPath);
                previous.accept(new ResourcePath(orig).getId(), resVal);
            });
        };
    }

    private String path(ResourceType type, Identifier identifier) {
        return type.getDirectory() + "/" + identifier.getNamespace() + "/" + identifier.getPath();
    }

    private String parent(String path) {
        int li = path.lastIndexOf('/');
        return li <= 0 ? null : path.substring(0, li);
    }

    /**
     * Identify all directory RPOs relevant to the directory at {@code path} (IE in it or its parents), from outermost to innermost
     */
    private List<DirRpo> findDirRpos(ResourcePack pack, String path) {
        if (path == null) return List.of();

        CacheKey key = MetaCache.getKeyByPack(pack);
        RespackoptsFS fs = new RespackoptsFS(pack);
        CachedPackState state = MetaCache.getState(key);
        var cache = state.cachedDirRPOs();

        {
            // This is outside computeIfAbsent because it could cause modification of the map, which is unsupported within it
            List<DirRpo> cached = cache.get(path);
            if (cached != null) return cached;
        }

        List<DirRpo> parentRPOs = findDirRpos(pack, parent(path));
        synchronized (cache) { // This is synchronized as multiple resources might be accessed at the same time, potentially causing a CME here
            return cache.computeIfAbsent(path, $ -> {
                String rp = path + "/" + Respackopts.FILE_EXTENSION;
                InputSupplier<InputStream> is = UserResourceEvents.disable(() -> fs.open(rp));
                if (is == null) return parentRPOs;
                if (state.tracker() != null) state.tracker().addDependency(path, rp);
                try (Reader w = new InputStreamReader(is.get())) {
                    List<DirRpo> currentRPOs = new LinkedList<>(parentRPOs);
                    DirRpo newRPO = AttachmentHolder.attach(state.metadata().version, () -> GC_DirRpo.deserialize(w, LibJf.LENIENT_TRANSPORT));
                    newRPO.hydrate(path);
                    if (newRPO.fallback != null && !newRPO.fallback.endsWith("/"))
                        newRPO.fallback += "/";
                    currentRPOs.add(newRPO);
                    return currentRPOs;
                } catch (IOException e) {
                    Respackopts.LOGGER.error("Couldn't open dir rpo " + rp, e);
                }
                return parentRPOs;
            });
        }
    }
}