package net.minecraft.client.resources.server;

import com.google.common.hash.HashCode;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import net.minecraft.server.packs.DownloadQueue.BatchResult;
import net.minecraft.server.packs.DownloadQueue.DownloadRequest;
import org.jspecify.annotations.Nullable;

public class ServerPackManager {
	private final PackDownloader downloader;
	private final PackLoadFeedback packLoadFeedback;
	private final PackReloadConfig reloadConfig;
	private final Runnable updateRequest;
	private ServerPackManager.PackPromptStatus packPromptStatus;
	private final List<ServerPackManager.ServerPackData> packs = new ArrayList<>();

	public ServerPackManager(
		final PackDownloader downloader,
		final PackLoadFeedback packLoadFeedback,
		final PackReloadConfig reloadConfig,
		final Runnable updateRequest,
		final ServerPackManager.PackPromptStatus packPromptStatus
	) {
		this.downloader = downloader;
		this.packLoadFeedback = packLoadFeedback;
		this.reloadConfig = reloadConfig;
		this.updateRequest = updateRequest;
		this.packPromptStatus = packPromptStatus;
	}

	private void registerForUpdate() {
		this.updateRequest.run();
	}

	private void markExistingPacksAsRemoved(final UUID id) {
		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (pack.id.equals(id)) {
				pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.SERVER_REPLACED);
			}
		}
	}

	public void pushPack(final UUID id, final URL url, final @Nullable HashCode hash) {
		if (this.packPromptStatus == ServerPackManager.PackPromptStatus.DECLINED) {
			this.packLoadFeedback.reportFinalResult(id, PackLoadFeedback.FinalResult.DECLINED);
		} else {
			this.pushNewPack(id, new ServerPackManager.ServerPackData(id, url, hash));
		}
	}

	public void pushLocalPack(final UUID id, final Path path) {
		if (this.packPromptStatus == ServerPackManager.PackPromptStatus.DECLINED) {
			this.packLoadFeedback.reportFinalResult(id, PackLoadFeedback.FinalResult.DECLINED);
		} else {
			URL url;
			try {
				url = path.toUri().toURL();
			} catch (MalformedURLException e) {
				throw new IllegalStateException("Can't convert path to URL " + path, e);
			}

			ServerPackManager.ServerPackData pack = new ServerPackManager.ServerPackData(id, url, null);
			pack.downloadStatus = ServerPackManager.PackDownloadStatus.DONE;
			pack.path = path;
			this.pushNewPack(id, pack);
		}
	}

	private void pushNewPack(final UUID id, final ServerPackManager.ServerPackData pack) {
		this.markExistingPacksAsRemoved(id);
		this.packs.add(pack);
		if (this.packPromptStatus == ServerPackManager.PackPromptStatus.ALLOWED) {
			this.acceptPack(pack);
		}

		this.registerForUpdate();
	}

	private void acceptPack(final ServerPackManager.ServerPackData pack) {
		this.packLoadFeedback.reportUpdate(pack.id, PackLoadFeedback.Update.ACCEPTED);
		pack.promptAccepted = true;
	}

	private ServerPackManager.@Nullable ServerPackData findPackInfo(final UUID id) {
		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (!pack.isRemoved() && pack.id.equals(id)) {
				return pack;
			}
		}

		return null;
	}

	public void popPack(final UUID id) {
		ServerPackManager.ServerPackData packInfo = this.findPackInfo(id);
		if (packInfo != null) {
			packInfo.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.SERVER_REMOVED);
			this.registerForUpdate();
		}
	}

	public void popAll() {
		for (ServerPackManager.ServerPackData pack : this.packs) {
			pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.SERVER_REMOVED);
		}

		this.registerForUpdate();
	}

	public void allowServerPacks() {
		this.packPromptStatus = ServerPackManager.PackPromptStatus.ALLOWED;

		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (!pack.promptAccepted && !pack.isRemoved()) {
				this.acceptPack(pack);
			}
		}

		this.registerForUpdate();
	}

	public void rejectServerPacks() {
		this.packPromptStatus = ServerPackManager.PackPromptStatus.DECLINED;

		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (!pack.promptAccepted) {
				pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.DECLINED);
			}
		}

		this.registerForUpdate();
	}

	public void resetPromptStatus() {
		this.packPromptStatus = ServerPackManager.PackPromptStatus.PENDING;
	}

	public void tick() {
		boolean downloadsPending = this.updateDownloads();
		if (!downloadsPending) {
			this.triggerReloadIfNeeded();
		}

		this.cleanupRemovedPacks();
	}

	private void cleanupRemovedPacks() {
		this.packs.removeIf(data -> {
			if (data.activationStatus != ServerPackManager.ActivationStatus.INACTIVE) {
				return false;
			}

			if (data.removalReason != null) {
				PackLoadFeedback.FinalResult response = data.removalReason.serverResponse;
				if (response != null) {
					this.packLoadFeedback.reportFinalResult(data.id, response);
				}

				return true;
			} else {
				return false;
			}
		});
	}

	private void onDownload(final Collection<ServerPackManager.ServerPackData> data, final BatchResult result) {
		if (!result.failed().isEmpty()) {
			for (ServerPackManager.ServerPackData pack : this.packs) {
				if (pack.activationStatus != ServerPackManager.ActivationStatus.ACTIVE) {
					if (result.failed().contains(pack.id)) {
						pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.DOWNLOAD_FAILED);
					} else {
						pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.DISCARDED);
					}
				}
			}
		}

		for (ServerPackManager.ServerPackData pack : data) {
			Path packFile = (Path)result.downloaded().get(pack.id);
			if (packFile != null) {
				pack.downloadStatus = ServerPackManager.PackDownloadStatus.DONE;
				pack.path = packFile;
				if (!pack.isRemoved()) {
					this.packLoadFeedback.reportUpdate(pack.id, PackLoadFeedback.Update.DOWNLOADED);
				}
			}
		}

		this.registerForUpdate();
	}

	private boolean updateDownloads() {
		List<ServerPackManager.ServerPackData> downloadPacks = new ArrayList<>();
		boolean downloadsInProgress = false;

		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (!pack.isRemoved() && pack.promptAccepted) {
				if (pack.downloadStatus != ServerPackManager.PackDownloadStatus.DONE) {
					downloadsInProgress = true;
				}

				if (pack.downloadStatus == ServerPackManager.PackDownloadStatus.REQUESTED) {
					pack.downloadStatus = ServerPackManager.PackDownloadStatus.PENDING;
					downloadPacks.add(pack);
				}
			}
		}

		if (!downloadPacks.isEmpty()) {
			Map<UUID, DownloadRequest> downloadRequests = new HashMap<>();

			for (ServerPackManager.ServerPackData pack : downloadPacks) {
				downloadRequests.put(pack.id, new DownloadRequest(pack.url, pack.hash));
			}

			this.downloader.download(downloadRequests, result -> this.onDownload(downloadPacks, result));
		}

		return downloadsInProgress;
	}

	private void triggerReloadIfNeeded() {
		boolean needsReload = false;
		final List<ServerPackManager.ServerPackData> packsToLoad = new ArrayList<>();
		final List<ServerPackManager.ServerPackData> packsToUnload = new ArrayList<>();

		for (ServerPackManager.ServerPackData pack : this.packs) {
			if (pack.activationStatus == ServerPackManager.ActivationStatus.PENDING) {
				return;
			}

			boolean shouldBeActive = pack.promptAccepted && pack.downloadStatus == ServerPackManager.PackDownloadStatus.DONE && !pack.isRemoved();
			if (shouldBeActive && pack.activationStatus == ServerPackManager.ActivationStatus.INACTIVE) {
				packsToLoad.add(pack);
				needsReload = true;
			}

			if (pack.activationStatus == ServerPackManager.ActivationStatus.ACTIVE) {
				if (!shouldBeActive) {
					needsReload = true;
					packsToUnload.add(pack);
				} else {
					packsToLoad.add(pack);
				}
			}
		}

		if (needsReload) {
			for (ServerPackManager.ServerPackData pack : packsToLoad) {
				if (pack.activationStatus != ServerPackManager.ActivationStatus.ACTIVE) {
					pack.activationStatus = ServerPackManager.ActivationStatus.PENDING;
				}
			}

			for (ServerPackManager.ServerPackData pack : packsToUnload) {
				pack.activationStatus = ServerPackManager.ActivationStatus.PENDING;
			}

			this.reloadConfig.scheduleReload(new PackReloadConfig.Callbacks() {
				@Override
				public void onSuccess() {
					for (ServerPackManager.ServerPackData pack : packsToLoad) {
						pack.activationStatus = ServerPackManager.ActivationStatus.ACTIVE;
						if (pack.removalReason == null) {
							ServerPackManager.this.packLoadFeedback.reportFinalResult(pack.id, PackLoadFeedback.FinalResult.APPLIED);
						}
					}

					for (ServerPackManager.ServerPackData pack : packsToUnload) {
						pack.activationStatus = ServerPackManager.ActivationStatus.INACTIVE;
					}

					ServerPackManager.this.registerForUpdate();
				}

				@Override
				public void onFailure(final boolean isRecovery) {
					if (!isRecovery) {
						packsToLoad.clear();

						for (ServerPackManager.ServerPackData pack : ServerPackManager.this.packs) {
							switch (pack.activationStatus) {
								case INACTIVE:
									pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.DISCARDED);
									break;
								case PENDING:
									pack.activationStatus = ServerPackManager.ActivationStatus.INACTIVE;
									pack.setRemovalReasonIfNotSet(ServerPackManager.RemovalReason.ACTIVATION_FAILED);
									break;
								case ACTIVE:
									packsToLoad.add(pack);
							}
						}

						ServerPackManager.this.registerForUpdate();
					} else {
						for (ServerPackManager.ServerPackData pack : ServerPackManager.this.packs) {
							if (pack.activationStatus == ServerPackManager.ActivationStatus.PENDING) {
								pack.activationStatus = ServerPackManager.ActivationStatus.INACTIVE;
							}
						}
					}
				}

				@Override
				public List<PackReloadConfig.IdAndPath> packsToLoad() {
					return packsToLoad.stream().map(pack -> new PackReloadConfig.IdAndPath(pack.id, pack.path)).toList();
				}
			});
		}
	}

	private enum ActivationStatus {
		INACTIVE,
		PENDING,
		ACTIVE;
	}

	private enum PackDownloadStatus {
		REQUESTED,
		PENDING,
		DONE;
	}

	public enum PackPromptStatus {
		PENDING,
		ALLOWED,
		DECLINED;
	}

	private enum RemovalReason {
		DOWNLOAD_FAILED(PackLoadFeedback.FinalResult.DOWNLOAD_FAILED),
		ACTIVATION_FAILED(PackLoadFeedback.FinalResult.ACTIVATION_FAILED),
		DECLINED(PackLoadFeedback.FinalResult.DECLINED),
		DISCARDED(PackLoadFeedback.FinalResult.DISCARDED),
		SERVER_REMOVED(null),
		SERVER_REPLACED(null);

		private final PackLoadFeedback.@Nullable FinalResult serverResponse;

		RemovalReason(final PackLoadFeedback.@Nullable FinalResult serverResponse) {
			this.serverResponse = serverResponse;
		}
	}

	private static class ServerPackData {
		private final UUID id;
		private final URL url;
		private final @Nullable HashCode hash;
		private @Nullable Path path;
		private ServerPackManager.@Nullable RemovalReason removalReason;
		private ServerPackManager.PackDownloadStatus downloadStatus = ServerPackManager.PackDownloadStatus.REQUESTED;
		private ServerPackManager.ActivationStatus activationStatus = ServerPackManager.ActivationStatus.INACTIVE;
		private boolean promptAccepted;

		private ServerPackData(final UUID id, final URL url, final @Nullable HashCode hash) {
			this.id = id;
			this.url = url;
			this.hash = hash;
		}

		public void setRemovalReasonIfNotSet(final ServerPackManager.RemovalReason removalReason) {
			if (this.removalReason == null) {
				this.removalReason = removalReason;
			}
		}

		public boolean isRemoved() {
			return this.removalReason != null;
		}
	}
}