import type {
	MediaFile,
	Directory,
	FileListing,
	FileListingWithStatus,
	DirectoryWithStatus,
} from "music-server-shared/types";
import { parseMap } from "music-server-shared/mapconversion";
import type { AppOptions, Playlist, PlaylistItem } from "./types";
import { joinPath, toast } from "./utils";
import { createSignal, type ResourceActions, type Signal } from "solid-js";
import { AsyncSemaphore } from "./semaphore";
import { encodePath } from "music-server-shared/utils";
import type { FlatFileListing } from "./App";

interface Progress {
	bytes: number;
}

interface LoadingItems {
	amount: number;
}

export type DownloadStatus = Progress | LoadingItems | "Synced" | undefined;
//used to display download status for directories/files in the filebrowser view
// export const [downloadStatusMap, setDownloadStatusMap] = createStore<Record<string, DownloadStatus>>({});
export interface StatusWithChildren {
	status: Signal<DownloadStatus>;
	children?: RecursiveStatus;
}

type RecursiveStatus = Map<string, StatusWithChildren>;
const downloadStatusMap: RecursiveStatus = new Map<string, StatusWithChildren>();

function updateProgressAmount(statusSignal: Signal<DownloadStatus>, loadChange: number) {
	const [getStatus, setStatus] = statusSignal;
	let status = getStatus();
	if (typeof status !== "object" || !("amount" in status)) {
		status = { amount: 0 };
		setStatus(status);
	}
	const newAmount = status.amount + loadChange;
	if (newAmount > 0) setStatus({ amount: newAmount });
	else setStatus(undefined);
}

export function getDownloadStatus(path: string, loadChange?: number) {
	const parts = path.split("/");
	let current = downloadStatusMap;
	//iterate through the basepath
	for (const part of parts.slice(0, -1)) {
		let next = current.get(part);
		if (!next) {
			next = { status: createSignal<DownloadStatus>(undefined) };
			current.set(part, next);
		}
		if (!next.children) {
			//might be a directory whose children have not been referenced before, in which case "children" would be undefined
			next.children = new Map();
		}
		if (loadChange) updateProgressAmount(next.status, loadChange);

		current = next.children as RecursiveStatus;
	}

	const fileName = parts.toReversed()[0];
	let ret = current.get(fileName);
	if (!ret) {
		ret = { status: createSignal<DownloadStatus>(undefined) };
		current.set(fileName, ret);
	}
	return ret.status;
}

//increase/decrease load amount for all parents and return requested signal
//needed to set parent directories to a loading state when any child is being downloaded/deleted
function startProgress(path: string) {
	return getDownloadStatus(path, 1);
}
function stopProgress(path: string) {
	return getDownloadStatus(path, -1);
}

//initialize filetrees and download statuses from indexedDB
export async function loadDataFromDB() {
	try {
		const db = await openDB();
		const files = await db.listFiles(FileStore);
		for (const file of files) {
			getDownloadStatus(file.path)[1]("Synced");
			updateFileTree(file.path, { metadata: file.metadata }, true);
		}
	} catch (e) {
		toast("Loading offline files failed", "error", e);
		console.error(e);
	}
}

//contains all locally synced files
const offlineTreeRoot: Directory = {
	files: new Map(),
};
//used for caching online file listings
const onlineTreeRoot: DirectoryWithStatus = {
	files: new Map(),
	status: "Unknown",
};

//merges "Scanned" directories from "other" to "target"
function mergeTrees(target: DirectoryWithStatus, other: DirectoryWithStatus) {
	if (other.status === "Unknown") return;
	target.status = other.status;
	for (const [fileName, file] of other.files.entries()) {
		const targetFile = target.files.get(fileName);
		if (targetFile && "files" in targetFile && "files" in file) {
			mergeTrees(targetFile, file);
		} else {
			target.files.set(fileName, file);
		}
	}
}

//TODO: improve typing to avoid "as"
//overloads for typecheking
//offline tree only stores files, directories are created ad-hoc
function updateFileTree(path: string, file: MediaFile, offline: true): void;
//online tree only stores cached directory listings
function updateFileTree(path: string, file: DirectoryWithStatus, offline: false): void;
// Updates file tree structure with new data (offline or online)
function updateFileTree(path: string, file: DirectoryWithStatus | MediaFile, offline: boolean) {
	if (offline && path === "") throw new Error("Trying to update root in offline mode");
	const basePath = path.split("/").slice(0, -1).join("/");
	const fileName = path.split("/").toReversed()[0];
	const node = getDirInTree(basePath, true, offline);

	if (offline) {
		node.files.set(fileName, file);
	} else {
		if (path === "") mergeTrees(node as DirectoryWithStatus, file as DirectoryWithStatus);
		else {
			let target = node.files.get(fileName) as DirectoryWithStatus;
			if (!target) target = { files: new Map(), status: "Unknown" };
			mergeTrees(target as DirectoryWithStatus, file as DirectoryWithStatus);
			node.files.set(fileName, target);
		}
	}
}

//overloads for typecheking
function getDirInTree(path: string, create: true, offline: true): Directory;
function getDirInTree(path: string, create: true, offline: false): DirectoryWithStatus;
function getDirInTree(path: string, create: false, offline: true): Directory | null;
function getDirInTree(path: string, create: false, offline: false): DirectoryWithStatus | null;
function getDirInTree(path: string, create: true, offline: boolean): DirectoryWithStatus | Directory;
function getDirInTree(path: string, create: false, offline: boolean): DirectoryWithStatus | Directory | null;
// get a DirectoryNode from the directory tree matching the path, and optionally creating missing nodes it if they don't exist yet
function getDirInTree(path: string, create: boolean, offline: boolean): DirectoryWithStatus | Directory | null {
	let current = offline ? offlineTreeRoot : onlineTreeRoot;
	if (path === "") return current;
	const parts = path.split("/");

	for (const part of parts) {
		let next: DirectoryWithStatus | Directory | MediaFile | undefined = current.files.get(part);
		if (!next || "metadata" in next) {
			if (!create) return null;
			//if mediafile already exists, we overwrite it with a directory anyway
			if (offline) next = { files: new Map() };
			else next = { files: new Map(), status: "Unknown" };
			current.files.set(part, next);
		}
		current = next;
	}
	return current;
}

function deleteInOfflineTree(path: string): void {
	if (path === "") return;
	const basePath = path.split("/").slice(0, -1).join("/");
	const fileName = path.split("/").toReversed()[0];

	const node = getDirInTree(basePath, false, true);
	if (!node) return;

	node.files.delete(fileName);
	if (node.files.size === 0) deleteInOfflineTree(basePath);
}

export const clearDirectoryCache = (path: string) => {
	const node = getDirInTree(path, false, false);
	if (!node) return;
	node.files.clear();
	node.status = "Unknown";
};

async function listOnlineFiles(dir: string, recursive: boolean): Promise<FileListingWithStatus | undefined> {
	const response = await fetch(`/list/${encodePath(dir)}?recursive=${recursive}`).catch(() => {});
	if (response?.status === 404) {
		toast(`Directory not found: ${dir}`, "error");
		return;
	}
	if (!response || !response.ok) {
		toast(
			`Fetching files for ${dir === "" ? "root" : dir} failed${response ? `: ${response.statusText}` : ""}`,
			"error",
		);
		return;
	}

	return parseMap(await response.text()) as FileListingWithStatus;
}

function listOfflineFiles(dir: string): FileListing {
	const node = getDirInTree(dir, false, true);
	if (!node || !node.files) return new Map();
	return node.files;
}

//checks if this Directory is completely scanned, i.e. suitable for a recursive listing result
function fullyKnown(dir: DirectoryWithStatus) {
	if (dir.status === "Unknown") {
		return false;
	}
	if (dir.files.values().some((value) => "files" in value && !fullyKnown(value))) {
		return false;
	}
	return true;
}

//non-recursive listing should not include nested children
function pruneChildren(listing: FileListing) {
	const pruned = new Map();
	for (const [name, item] of listing.entries()) {
		if ("metadata" in item) pruned.set(name, item);
		else pruned.set(name, { files: new Map() });
	}
	return pruned;
}

//used for combining the online and offline results, to be able to show files that only exist locally
function combineFileListings(listing1: FileListing, listing2: FileListing): FileListing {
	const result = new Map(listing1);

	for (const [key, value2] of listing2.entries()) {
		const value1 = result.get(key);

		if (value1 && "files" in value1 && "files" in value2) {
			result.set(key, { files: combineFileListings(value1.files, value2.files) });
		} else {
			result.set(key, value2);
		}
	}

	return result;
}

// File listing logic with hybrid online/offline support
// Combines:
// 1. Direct IndexedDB lookups for offline mode
// 2. Cached online listings
// 3. Merged online+offline results
export async function listFiles(dir: string, offline: boolean, recursive: boolean): Promise<FileListing> {
	if (offline) {
		const files = listOfflineFiles(dir);
		return recursive ? files : pruneChildren(files);
	}
	const cached = getDirInTree(dir, false, false);
	if (cached !== null && cached.status === "Scanned" && (!recursive || fullyKnown(cached))) {
		const combined = combineFileListings(cached.files, listOfflineFiles(dir));
		return recursive ? combined : pruneChildren(combined);
	}
	const files = await listOnlineFiles(dir, recursive);
	if (!files) return new Map();
	updateFileTree(dir, { files, status: "Scanned" }, false);
	const combined = combineFileListings(files, listOfflineFiles(dir));
	return recursive ? combined : pruneChildren(combined);
}

//get cover art for a directory with cache-first strategy
export async function getCover(dir: string, offline: boolean) {
	const db = await openDB();
	const dbResult = await db.get(CoverStore, dir);
	if (dbResult !== undefined) {
		const cached = dbResult as StoredCover;
		return cached.data === null ? undefined : URL.createObjectURL(new Blob([cached.data]));
	}

	if (offline) return undefined;

	const response = await fetch(`/cover/${encodePath(dir)}`, { method: "GET" }).catch(() => {});
	if (!response || response.status === 404) {
		db.put(CoverStore, { path: dir, data: null });
		return undefined;
	}
	const blob = await response.blob();
	db.put(CoverStore, { path: dir, data: blob });
	return URL.createObjectURL(blob);
}

export const clearCoverCache = async (path: string) => {
	const db = await openDB();
	return db.delete(CoverStore, path);
};

//returns an object url to the blob if synced, otherwise the server url
export async function getSrc(path: string, options: AppOptions, offline: boolean, forceUrl?: true): Promise<string>;
export async function getSrc(path: string, options: AppOptions, offline: boolean, forceUrl?: boolean) {
	if (!forceUrl) {
		const db = await openDB();
		const dbResult = (await db.get(FileStore, path)) as StoredFile;
		if (dbResult) return URL.createObjectURL(dbResult.data);

		if (offline) {
			toast("This file is not cached, leave offline mode to play it", "error");
			return undefined;
		}
	}
	if (options.enableTranscoding) {
		return `${joinPath("/transcode", encodePath(path))}?bitrate=${options.bitrate}&format=${options.format}&disableChunkedTranscoding=${options.disableChunkedTranscoding}`;
	}
	return joinPath("/download", encodePath(path));
}

export async function loadPlaylists() {
	const db = await openDB();
	return await db.listPlaylists(PlaylistStore);
}

//save playlist to indexedDB, throws error if playlist with that name already exists and overwrite=false
export async function savePlaylist(playlist: Playlist, overwrite: boolean) {
	const db = await openDB();
	playlist.items = playlist.items.map((item) => {
		//some less space in the db by omitting ids
		const { id, ...itemWithoutId } = item as PlaylistItem;
		return itemWithoutId;
	});
	if (overwrite) await db.put(PlaylistStore, playlist);
	else await db.add(PlaylistStore, playlist);
}

export async function deletePlaylist(name: string) {
	const db = await openDB();
	await db.delete(PlaylistStore, name);
}

function collectMediaFilePaths(listing: FileListing, basePath: string): string[] {
	const paths: string[] = [];

	for (const [name, item] of listing.entries()) {
		const currentPath = joinPath(basePath, name);

		if ("metadata" in item) {
			paths.push(currentPath);
		} else if ("files" in item) {
			paths.push(...collectMediaFilePaths(item.files, currentPath));
		}
	}

	return paths;
}

//deletes file or directory(+recursive contents) from indexedDB and updates their download statuses
export async function deleteFile(
	fileName: string,
	item: MediaFile | Directory,
	basePath: string,
	fetchFiles: ResourceActions<FlatFileListing>,
) {
	const fullPath = joinPath(basePath, fileName);
	const [getStatus] = getDownloadStatus(fullPath);
	try {
		if ("metadata" in item && getStatus() !== "Synced") return;
		startProgress(fullPath)[1]({ amount: 1 });

		let toDelete: string[];
		if ("files" in item) {
			toDelete = collectMediaFilePaths(listOfflineFiles(fullPath), fullPath);
		} else {
			toDelete = [fullPath];
		}

		const db = await openDB();
		await db.deleteAll(FileStore, toDelete); //delete from database
		deleteInOfflineTree(fullPath); //delete node  from tree
		for (const path of toDelete) {
			getDownloadStatus(path)[1](undefined); // set all children to unsynced
		}
		fetchFiles.refetch();
	} finally {
		stopProgress(fullPath)[1](undefined);
	}
}

const downloadSemaphore = new AsyncSemaphore(1);

//Download file to indexedDB and updates the offline file tree
//concurrency control via the downloadSemaphore
async function downloadFile(
	path: string,
	options: AppOptions,
	item: MediaFile,
	fetchFiles: ResourceActions<FlatFileListing>,
): Promise<void> {
	const [getStatus, setStatus] = getDownloadStatus(path);
	const initialProgress = getStatus();
	if (typeof initialProgress === "object" && "bytes" in initialProgress) return; // download already in progress

	try {
		startProgress(path)[1]({ bytes: 0 });
		const db = await openDB();
		let mimeType: string | undefined;

		//options might change at any point, update the semaphore to the current value
		downloadSemaphore.setMaxConcurrency(options.enableTranscoding ? options.maxTranscodes : options.maxDownloads);
		let blob: Blob;
		try {
			//make sure to only allow the set amount of parallel downloads
			await downloadSemaphore.acquire();
			const res = await fetch(await getSrc(path, options, false, true));

			//let the browser do the actual download
			const blobPromise = res.clone().blob();
			if (!res.ok || !res.body) throw res.statusText;
			//we just iterate over the chunks to get the current progress
			const reader = res.body.getReader();
			mimeType = res.headers.get("content-type") ?? undefined;
			let received = 0;

			let lastUpdate = 0;
			while (true) {
				const { done, value } = await reader.read();
				if (done) break;
				received += value.length;

				//debouncing logic to not update UI too fast
				const now = Date.now();
				if (now - lastUpdate < 250) continue;
				lastUpdate = now;
				setStatus({ bytes: received });
			}
			blob = await blobPromise;
		} finally {
			downloadSemaphore.release();
		}
		await db.put(FileStore, {
			path,
			data: blob,
			metadata: { ...item.metadata }, //spread needed, because item might be a proxy object from the filebrowser, which can't be stored
		} as StoredFile);
		updateFileTree(path, item, true);
		stopProgress(path)[1]("Synced");
		fetchFiles.refetch();
	} catch (e) {
		toast(`Downloading ${path} failed`, "error", e);
		//restore original status
		stopProgress(path)[1](initialProgress === "Synced" ? "Synced" : undefined);
	}
}

export async function download(
	fileName: string,
	item: MediaFile | Directory,
	basePath: string,
	options: AppOptions,
	fetchFiles: ResourceActions<FlatFileListing>,
) {
	const fullPath = joinPath(basePath, fileName);
	if ("metadata" in item) {
		await downloadFile(fullPath, options, item, fetchFiles);
	} else {
		updateProgressAmount(startProgress(fullPath), 1);
		try {
			await getCover(fullPath, false);
			//start downloads for all children to allow them to run in parallel, then wait for the results
			const promises: Promise<unknown>[] = [];
			for (const [childName, childItem] of await listFiles(fullPath, false, false)) {
				promises.push(download(childName, childItem, fullPath, options, fetchFiles));
			}
			await Promise.allSettled(promises);
		} finally {
			updateProgressAmount(stopProgress(fullPath), -1);
		}
	}
}

export async function getStoredFiles() {
	const db = await openDB();
	return await db.getKeys(FileStore);
}

interface StoredFile {
	path: string;
	data: Blob;
	metadata: {
		duration: number;
	};
}

interface StoredCover {
	path: string;
	data: Blob | null;
}

const FileStore = "fileblobs";
const CoverStore = "covers";
const PlaylistStore = "playlists";

async function openDB() {
	return new Promise<DatabaseWrapper>((resolve, reject) => {
		const req = indexedDB.open("music-files");
		req.onerror = () => reject(req.error);
		req.onupgradeneeded = () => {
			const db = req.result;
			if (!db.objectStoreNames.contains(FileStore))
				db.createObjectStore(FileStore, { keyPath: "path" }).createIndex("index", "path", { unique: true });
			if (!db.objectStoreNames.contains(CoverStore))
				db.createObjectStore(CoverStore, { keyPath: "path" }).createIndex("index", "path", { unique: true });
			if (!db.objectStoreNames.contains(PlaylistStore))
				db.createObjectStore(PlaylistStore, { keyPath: "path" }).createIndex("index", "path", { unique: true });
		};
		req.onsuccess = () => resolve(wrapDB(req.result));
	});
}

interface DatabaseWrapper {
	get(store: typeof CoverStore | typeof FileStore, key: string): Promise<unknown>;
	put(store: typeof FileStore, value: StoredFile): Promise<void>;
	put(store: typeof CoverStore, value: StoredCover): Promise<void>;
	put(store: typeof PlaylistStore, value: Playlist): Promise<void>;
	add(store: typeof PlaylistStore, value: Playlist): Promise<void>;
	delete(store: typeof CoverStore | typeof PlaylistStore, key: string): Promise<void>;
	deleteAll(store: typeof FileStore, keys: string[]): Promise<void>;
	clear(store: string): Promise<void>;
	listFiles(store: typeof FileStore): Promise<StoredFile[]>;
	listPlaylists(store: typeof PlaylistStore): Promise<Playlist[]>;
	getKeys(store: typeof FileStore): Promise<string[]>;
}

function wrapDB(db: IDBDatabase): DatabaseWrapper {
	return {
		get: (store: string, key: string) =>
			new Promise((res, rej) => {
				const tx = db.transaction(store, "readonly");
				const req = tx.objectStore(store).get(key);
				req.onsuccess = () => res(req.result);
				req.onerror = () => rej(req.error);
			}),
		put: (store: string, value: unknown) =>
			new Promise<void>((res, rej) => {
				const tx = db.transaction(store, "readwrite");
				const req: IDBRequest<IDBValidKey> = tx.objectStore(store).put(value);
				req.onsuccess = () => res();
				req.onerror = () => rej(req.error);
			}),
		add: (store: string, value: unknown) =>
			new Promise<void>((res, rej) => {
				const tx = db.transaction(store, "readwrite");
				const req: IDBRequest<IDBValidKey> = tx.objectStore(store).add(value);
				req.onsuccess = () => res();
				req.onerror = () => rej(req.error);
			}),
		delete: (store: string, key: string) =>
			new Promise<void>((res, rej) => {
				const tx = db.transaction(store, "readwrite");
				const req = tx.objectStore(store).delete(key);
				req.onsuccess = () => res();
				req.onerror = () => rej(req.error);
			}),
		deleteAll: (store: typeof FileStore, keys: string[]) =>
			new Promise<void>((res, rej) => {
				const tx = db.transaction(store, "readwrite");
				const objectStore = tx.objectStore(store);
				for (const key of keys) {
					objectStore.delete(key);
				}
				tx.oncomplete = () => res();
				tx.onerror = () => rej(tx.error);
			}),
		clear: (store: string) =>
			new Promise<void>((res, rej) => {
				const tx = db.transaction(store, "readwrite");
				const req = tx.objectStore(store).clear();
				req.onsuccess = () => res();
				req.onerror = () => rej(req.error);
			}),
		listFiles: (store: typeof FileStore) =>
			new Promise((res, rej) => {
				const tx = db.transaction(store, "readonly");
				const req = tx.objectStore(store).getAll();
				req.onsuccess = () => res(req.result);
				req.onerror = () => rej(req.error);
			}),
		listPlaylists: (store: typeof PlaylistStore) =>
			new Promise((res, rej) => {
				const tx = db.transaction(store, "readonly");
				const req = tx.objectStore(store).getAll();
				req.onsuccess = () => res(req.result);
				req.onerror = () => rej(req.error);
			}),
		getKeys: (store: typeof FileStore) =>
			new Promise((res, rej) => {
				const tx = db.transaction(store, "readonly");
				const req = tx.objectStore(store).getAllKeys();
				req.onsuccess = () => res(req.result as string[]);
				req.onerror = () => rej(req.error);
			}),
	};
}