package launcher.hasher;

import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Collections;
import java.util.Deque;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;

import launcher.LauncherAPI;
import launcher.helper.IOHelper;
import launcher.helper.VerifyHelper;
import launcher.serialize.HInput;
import launcher.serialize.HOutput;
import launcher.serialize.stream.EnumSerializer;

public final class HashedDir extends HashedEntry {
	private final Map<String, HashedEntry> map = new HashMap<>(32);

	@LauncherAPI
	public HashedDir() {
	}

	@LauncherAPI
	public HashedDir(Path dir, FileNameMatcher matcher) throws IOException {
		IOHelper.walk(dir, new HashFileVisitor(dir, matcher), true);
	}

	@LauncherAPI
	public HashedDir(HInput input) throws IOException {
		int entriesCount = input.readLength(0);
		for (int i = 0; i < entriesCount; i++) {
			String name = IOHelper.verifyFileName(input.readString(255));

			// Read entry
			HashedEntry entry;
			Type type = Type.read(input);
			switch (type) {
				case FILE:
					entry = new HashedFile(input);
					break;
				case DIR:
					entry = new HashedDir(input);
					break;
				default:
					throw new AssertionError("Unsupported hashed entry type: " + type.name());
			}

			// Try add entry to map
			VerifyHelper.putIfAbsent(map, name, entry, String.format("Duplicate dir entry: '%s'", name));
		}
	}

	@Override
	public Type getType() {
		return Type.DIR;
	}

	@Override
	public long size() {
		return map.values().stream().mapToLong(HashedEntry::size).sum();
	}

	@Override
	public void write(HOutput output) throws IOException {
		Set<Map.Entry<String, HashedEntry>> entries = map.entrySet();
		output.writeLength(entries.size(), 0);
		for (Map.Entry<String, HashedEntry> mapEntry : entries) {
			output.writeString(mapEntry.getKey(), 255);

			// Write hashed entry
			HashedEntry entry = mapEntry.getValue();
			EnumSerializer.write(output, entry.getType());
			entry.write(output);
		}
	}

	@LauncherAPI
	public Diff diff(HashedDir other, FileNameMatcher matcher) {
		HashedDir mismatch = sideDiff(other, matcher, new LinkedList<>(), true);
		HashedDir extra = other.sideDiff(this, matcher, new LinkedList<>(), false);
		return new Diff(mismatch, extra);
	}

	@LauncherAPI
	public HashedEntry getEntry(String name) {
		return map.get(name);
	}

	@LauncherAPI
	public boolean isEmpty() {
		return map.isEmpty();
	}

	@LauncherAPI
	public Map<String, HashedEntry> map() {
		return Collections.unmodifiableMap(map);
	}

	@LauncherAPI
	public HashedEntry resolve(Iterable<String> path) {
		HashedEntry current = this;
		for (String pathEntry : path) {
			if (current instanceof HashedDir) {
				current = ((HashedDir) current).map.get(pathEntry);
				continue;
			}
			return null;
		}
		return current;
	}

	private HashedDir sideDiff(HashedDir other, FileNameMatcher matcher, Deque<String> path, boolean mismatchList) {
		HashedDir diff = new HashedDir();
		for (Map.Entry<String, HashedEntry> mapEntry : map.entrySet()) {
			String name = mapEntry.getKey();
			HashedEntry entry = mapEntry.getValue();
			path.add(name);

			// Should update?
			boolean shouldUpdate = matcher == null || matcher.shouldUpdate(path);

			// Not found or of different type
			Type type = entry.getType();
			HashedEntry otherEntry = other.map.get(name);
			if (otherEntry == null || otherEntry.getType() != type) {
				if (shouldUpdate || mismatchList && otherEntry == null) {
					diff.map.put(name, entry);

					// Should be deleted!
					if (!mismatchList) {
						entry.flag = true;
					}
				}
				path.removeLast();
				continue;
			}

			// Compare entries based on type
			switch (type) {
				case FILE:
					HashedFile file = (HashedFile) entry;
					HashedFile otherFile = (HashedFile) otherEntry;
					if (mismatchList && shouldUpdate && !file.isSame(otherFile)) {
						diff.map.put(name, entry);
					}
					break;
				case DIR:
					HashedDir dir = (HashedDir) entry;
					HashedDir otherDir = (HashedDir) otherEntry;
					if (mismatchList || shouldUpdate) { // Maybe isn't need to go deeper?
						HashedDir mismatch = dir.sideDiff(otherDir, matcher, path, mismatchList);
						if (!mismatch.isEmpty()) {
							diff.map.put(name, mismatch);
						}
					}
					break;
				default:
					throw new AssertionError("Unsupported hashed entry type: " + type.name());
			}

			// Remove this path entry
			path.removeLast();
		}
		return diff;
	}

	private final class HashFileVisitor extends SimpleFileVisitor<Path> {
		private final Path dir;
		private final FileNameMatcher matcher;
		private final Deque<String> path = new LinkedList<>();
		private final Deque<HashedDir> stack = new LinkedList<>();

		// State
		private HashedDir current = HashedDir.this;

		private HashFileVisitor(Path dir, FileNameMatcher matcher) {
			this.dir = dir;
			this.matcher = matcher;
		}

		@Override
		public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
			FileVisitResult result = super.postVisitDirectory(dir, exc);
			if (this.dir.equals(dir)) {
				return result;
			}

			// Add directory to parent
			HashedDir parent = stack.removeLast();
			parent.map.put(path.removeLast(), current);
			current = parent;

			// We're done
			return result;
		}

		@Override
		public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
			FileVisitResult result = super.preVisitDirectory(dir, attrs);
			if (this.dir.equals(dir)) {
				return result;
			}

			// Add child
			stack.add(current);
			current = new HashedDir();
			path.add(IOHelper.getFileName(dir));

			// We're done
			return result;
		}

		@Override
		public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
			path.add(IOHelper.getFileName(file));

			// Add file (may be unhashed, if exclusion)
			boolean hash = matcher == null || matcher.shouldUpdate(path);
			current.map.put(path.removeLast(), new HashedFile(file, attrs.size(), hash));
			return super.visitFile(file, attrs);
		}
	}

	public static final class Diff {
		@LauncherAPI public final HashedDir mismatch;
		@LauncherAPI public final HashedDir extra;

		private Diff(HashedDir mismatch, HashedDir extra) {
			this.mismatch = mismatch;
			this.extra = extra;
		}

		@LauncherAPI
		public boolean isSame() {
			return mismatch.isEmpty() && extra.isEmpty();
		}
	}
}