// Locating and reading the exporter's output. The companion Playnite extension (`exporter/`) writes
// `punktfunk-library.json` into its own Playnite plugin-data directory, i.e.
// `<PlayniteData>/ExtensionsData/<pluginId-guid>/punktfunk-library.json`. We don't hardcode that guid
// — we glob `ExtensionsData/*/punktfunk-library.json` and take the newest, so the reader is decoupled
// from the exporter's id.
//
// The plugin runs on the same box as Playnite (it's the streaming host), so these are plain local
// reads. The wrinkle is *which account* can see the file. The managed runner is de-privileged
// (`NT AUTHORITY\LocalService`) and cannot read the interactive user's `%APPDATA%`, so the reliable
// source is the **ingest inbox** (`<config_dir>/ingest/playnite/punktfunk-library.json`) the
// exporter drops the file into — checked FIRST. The `%APPDATA%`/`C:\Users\*` ExtensionsData scan
// still works for a same-user/SYSTEM runner or on Linux, and an explicit `playniteDir` override
// joins the candidate list.

import * as fs from "node:fs";
import * as path from "node:path";
import type { Config } from "./config.js";
import {
	EXPORT_FILE,
	isLibraryExport,
	type LibraryExport,
	SCHEMA,
} from "./export-schema.js";
import { ingestDir } from "./paths.js";

const exists = (p: string): boolean => {
	try {
		fs.accessSync(p);
		return true;
	} catch {
		return false;
	}
};

/** Candidate Playnite data directories, most-specific first (config override handled by the caller). */
export const candidatePlayniteDirs = (): string[] => {
	const out: string[] = [];
	if (process.platform === "win32") {
		const appdata = process.env.APPDATA;
		if (appdata) out.push(path.join(appdata, "Playnite"));
		// SYSTEM/other-user runner: scan every local profile's roaming AppData.
		const usersRoot = path.join(process.env.SystemDrive ?? "C:", "\\", "Users");
		try {
			for (const user of fs.readdirSync(usersRoot)) {
				out.push(path.join(usersRoot, user, "AppData", "Roaming", "Playnite"));
			}
		} catch {
			// no C:\Users (or not Windows-like) — fine
		}
	} else {
		// Playnite is Windows-only, but a Wine/portable layout may set these — best effort.
		const home = process.env.HOME;
		if (home) {
			out.push(path.join(home, ".local", "share", "Playnite"));
		}
	}
	// De-dupe, preserve order.
	return [...new Set(out)];
};

export interface Location {
	/** The resolved Playnite data dir, or null if none found. */
	dir: string | null;
	/** The candidate dirs we considered (for the UI's diagnostics view). */
	candidates: string[];
	/** The resolved export file, or null if the exporter hasn't written one yet. */
	file: string | null;
	/** mtime (epoch ms) of the export file, or null. */
	mtime: number | null;
}

/** Find the newest `punktfunk-library.json` under a Playnite dir's `ExtensionsData`. */
const findExportUnder = (
	dir: string,
): { file: string; mtime: number } | null => {
	const base = path.join(dir, "ExtensionsData");
	let best: { file: string; mtime: number } | null = null;
	let subdirs: string[];
	try {
		subdirs = fs.readdirSync(base);
	} catch {
		return null;
	}
	for (const sub of subdirs) {
		const file = path.join(base, sub, EXPORT_FILE);
		try {
			const st = fs.statSync(file);
			if (!best || st.mtimeMs > best.mtime) best = { file, mtime: st.mtimeMs };
		} catch {
			// no export in this extension's dir
		}
	}
	return best;
};

/** Resolve where the export lives. `config.playniteDir` wins; otherwise probe the candidates. */
export const locateExport = (config: Config): Location => {
	const override = config.playniteDir;
	const candidates = override
		? [override, ...candidatePlayniteDirs()]
		: candidatePlayniteDirs();

	// The ingest inbox first: the exporter drops the library here (a flat file, not an
	// `ExtensionsData/<guid>` tree) so the de-privileged LocalService runner can read it — it can't
	// reach the interactive user's `%APPDATA%`. This is the reliable path on a managed Windows host.
	const inbox = ingestDir();
	const inboxFile = path.join(inbox, EXPORT_FILE);
	try {
		const st = fs.statSync(inboxFile);
		return {
			dir: inbox,
			candidates: [inbox, ...candidates],
			file: inboxFile,
			mtime: st.mtimeMs,
		};
	} catch {
		// no ingest drop yet — fall back to scanning Playnite's own data dirs
	}

	// Then, a Playnite data dir that actually holds an export file (same-user/SYSTEM runner, Linux).
	for (const dir of candidates) {
		const hit = findExportUnder(dir);
		if (hit)
			return {
				dir,
				candidates: [inbox, ...candidates],
				file: hit.file,
				mtime: hit.mtime,
			};
	}
	// Else, the first dir that at least exists (so the UI can say "Playnite found, exporter not
	// installed yet" vs "Playnite not found").
	const dir = candidates.find(exists) ?? null;
	return { dir, candidates: [inbox, ...candidates], file: null, mtime: null };
};

export class ExportError extends Error {}

/** Read + validate the export file. Throws `ExportError` on a missing/corrupt/too-new file. */
export const readExport = (file: string): LibraryExport => {
	let raw: string;
	try {
		raw = fs.readFileSync(file, "utf8");
	} catch (e) {
		throw new ExportError(`cannot read ${file}: ${e}`);
	}
	let parsed: unknown;
	try {
		parsed = JSON.parse(raw);
	} catch (e) {
		throw new ExportError(`${file} is not valid JSON: ${e}`);
	}
	if (!isLibraryExport(parsed)) {
		throw new ExportError(`${file} is not a punktfunk library export`);
	}
	if (Math.floor(parsed.schema) > SCHEMA) {
		throw new ExportError(
			`${file} is schema ${parsed.schema}; this plugin understands up to ${SCHEMA} — update the plugin`,
		);
	}
	return parsed;
};