// PlayniteSync — the plugin's engine service: wires the pure domain (locate → read →
// compute) into the kit's generic SyncEngine (poll/watch/debounce/coalesce/fingerprint)
// and the ProviderClient reconcile. Also owns the EngineStatus assembly the API and the
// SSE feed share, the side-effect-light preview the Library page uses, and the allow-listed
// cover-art reader behind `/api/art`.

import * as fs from "node:fs";
import * as path from "node:path";
import {
	type Config,
	type EngineStatus,
	EXPORT_FILE,
	ExportUnavailable,
	type LibraryExport,
	type Location,
	type PlayniteInfo,
	type PreviewResult,
	resolveConfig,
	type SyncReport,
} from "@playnite/contract";
import {
	type LastSync,
	makeSyncEngine,
	ProviderClient,
	pluginIngestDir,
	type SyncEngine,
} from "@punktfunk/plugin-kit";
import type { ProviderEntry } from "@punktfunk/plugin-kit/wire";
import {
	Context,
	Duration,
	Effect,
	Layer,
	Ref,
	type Scope,
	Stream,
} from "effect";
import { PLUGIN_NAME, PROVIDER_ID } from "../const.js";
import { artPaths, buildArtwork, mimeFor } from "../domain/art.js";
import { locateExport, readExport } from "../domain/locate.js";
import { computeEntries } from "../domain/reconcile.js";
import { PlayniteCache } from "./cache.js";
import { PlayniteConfig } from "./config.js";

/** One cover the `/api/art` proxy is willing to serve. */
export interface ArtFile {
	readonly bytes: Uint8Array;
	readonly contentType: string;
}

export interface PlayniteSyncService {
	readonly engine: SyncEngine<SyncReport>;
	/** Read + compute the desired state. NO art embedding, NO reconcile. */
	readonly preview: Effect.Effect<PreviewResult, ExportUnavailable>;
	readonly status: Effect.Effect<EngineStatus>;
	/** The SSE feed: a full EngineStatus on every engine transition. */
	readonly statusChanges: Stream.Stream<EngineStatus>;
	/** Where the export was found — the CLI's `where`, without a full read. */
	readonly locate: Effect.Effect<Location>;
	/**
	 * Read one local cover, but ONLY if the currently-ingested export references it.
	 * `undefined` for anything else — the browser cannot ask this for an arbitrary file.
	 */
	readonly art: (file: string) => Effect.Effect<ArtFile | undefined>;
}

export class PlayniteSync extends Context.Service<
	PlayniteSync,
	PlayniteSyncService
>()("playnite/PlayniteSync") {
	// Layer.effect runs `make` in the LAYER's scope (Scope is excluded from R) — the
	// engine's watch/poll loops live exactly as long as the plugin runtime.
	static readonly layer: Layer.Layer<
		PlayniteSync,
		never,
		PlayniteConfig | PlayniteCache | ProviderClient
	> = Layer.effect(PlayniteSync)(make());
}

const NO_LOCATION: Location = {
	dir: null,
	candidates: [],
	file: null,
	mtime: null,
	viaIngest: false,
};

/** The art allow-list, pinned to the export document it was derived from. */
interface AllowList {
	readonly file: string;
	readonly mtime: number;
	readonly paths: ReadonlySet<string>;
}

function make(): Effect.Effect<
	PlayniteSyncService,
	never,
	PlayniteConfig | PlayniteCache | ProviderClient | Scope.Scope
> {
	return Effect.gen(function* () {
		const cfg = yield* PlayniteConfig;
		const cache = yield* PlayniteCache;
		const provider = yield* ProviderClient;
		const platform = process.platform;
		const ingest = pluginIngestDir(PLUGIN_NAME);

		// Observed state the status view reports (the old Engine's private fields).
		const lastLocation = yield* Ref.make<Location>(NO_LOCATION);
		const lastError = yield* Ref.make<string | undefined>(undefined);
		const lastPlaynite = yield* Ref.make<PlayniteInfo | undefined>(undefined);
		const allowList = yield* Ref.make<AllowList | undefined>(undefined);

		const loadOrDefault = cfg.load.pipe(
			Effect.orElseSucceed(() => resolveConfig({})),
		);

		/** Locate + read + decode, refreshing everything the status view and the art proxy
		 *  derive from the export. The one place an export failure is recorded. */
		const readCurrent = (
			config: Config,
		): Effect.Effect<LibraryExport, ExportUnavailable> =>
			Effect.gen(function* () {
				const location = locateExport(config);
				yield* Ref.set(lastLocation, location);
				if (location.file === null) {
					const message = `no exporter output under ${location.dir ?? "any Playnite data dir"} — is the Punktfunk Sync extension installed in Playnite?`;
					yield* Ref.set(lastError, message);
					return yield* Effect.fail(new ExportUnavailable({ message }));
				}
				const file = location.file;
				const exp = yield* Effect.try({
					try: () => readExport(file),
					catch: (cause) =>
						new ExportUnavailable({
							message: cause instanceof Error ? cause.message : String(cause),
						}),
				}).pipe(Effect.tapError((e) => Ref.set(lastError, e.message)));
				yield* Ref.set(lastError, undefined);
				yield* Ref.set(lastPlaynite, exp.playnite);
				yield* Ref.set(allowList, {
					file,
					mtime: location.mtime ?? 0,
					paths: artPaths(exp),
				});
				return exp;
			});

		const computeWith = (
			embedArt: boolean,
		): Effect.Effect<
			{ readonly entries: ProviderEntry[]; readonly report: SyncReport },
			ExportUnavailable
		> =>
			Effect.gen(function* () {
				const config = yield* loadOrDefault;
				const exp = yield* readCurrent(config);
				return computeEntries({
					exp,
					config,
					platform,
					// The preview skips the (heavy, in `dataurl` mode) art embed.
					artFor: embedArt
						? (g) => buildArtwork(g, config.art)
						: () => undefined,
				});
			});

		const engine = yield* makeSyncEngine<
			SyncReport,
			ReadonlyArray<ProviderEntry>,
			never
		>({
			compute: () => computeWith(true),
			apply: (entries) => provider.reconcile(PROVIDER_ID, entries),
			lastSync: {
				get: cache.get.pipe(Effect.map((c) => c.lastSync)),
				set: (last: LastSync) =>
					cache.update((c) => ({ ...c, lastSync: last })).pipe(Effect.ignore),
			},
			settings: loadOrDefault.pipe(
				Effect.map((config) => ({
					pollInterval: Duration.minutes(Math.max(1, config.sync.pollMinutes)),
					watch: config.sync.watch,
					debounce: Duration.millis(config.sync.debounceMs),
					watchDirs: watchTargets(config),
				})),
			),
		});

		/**
		 * What to watch: the ingest inbox ALWAYS (the de-privileged runner's only source,
		 * so an exporter drop reconciles within seconds even when the Playnite dir resolved
		 * elsewhere), plus the located Playnite dir's `ExtensionsData` when there is one.
		 * The kit's watcher set is best-effort — an absent dir is silently skipped and the
		 * interval poll covers it.
		 */
		function watchTargets(config: Config): string[] {
			const targets = new Set<string>([ingest]);
			const located = locateExport(config);
			if (located.dir !== null && !located.viaIngest) {
				const extData = path.join(located.dir, "ExtensionsData");
				targets.add(fs.existsSync(extData) ? extData : located.dir);
			}
			return [...targets];
		}

		const status: Effect.Effect<EngineStatus> = Effect.gen(function* () {
			const config = yield* loadOrDefault;
			const engineStatus = yield* engine.status;
			const location = yield* Ref.get(lastLocation);
			const exportError = yield* Ref.get(lastError);
			const playnite = yield* Ref.get(lastPlaynite);
			return {
				platform,
				// Before the first sync the status view would otherwise show nothing at all.
				location: location.file === null ? locateExport(config) : location,
				// Explicit nulls, never undefined — see the trap note in contract/domain.ts.
				exportError: exportError ?? null,
				playnite: playnite ?? null,
				artMode: config.art.mode,
				syncing: engineStatus.syncing,
				lastSync: engineStatus.lastSync ?? null,
				lastReport: engineStatus.lastReport ?? null,
				paths: {
					dir: path.dirname(cfg.path),
					config: cfg.path,
					cache: cache.path,
					ingest: path.join(ingest, EXPORT_FILE),
				},
			} satisfies EngineStatus;
		});

		const art = (file: string): Effect.Effect<ArtFile | undefined> =>
			Effect.gen(function* () {
				const cached = yield* Ref.get(allowList);
				const config = yield* loadOrDefault;
				const located = locateExport(config);
				// Refresh when we have never read an export, or the file moved under us —
				// otherwise a cover added since the last sync would 404 until the next one.
				const stale =
					cached === undefined ||
					located.file !== cached.file ||
					(located.mtime ?? 0) !== cached.mtime;
				if (stale) yield* readCurrent(config).pipe(Effect.ignore);
				const allow = yield* Ref.get(allowList);
				if (allow === undefined || !allow.paths.has(file)) return undefined;
				const contentType = mimeFor(file);
				if (contentType === null) return undefined;
				return yield* Effect.try(
					(): ArtFile => ({ bytes: fs.readFileSync(file), contentType }),
				).pipe(Effect.orElseSucceed(() => undefined));
			});

		return {
			engine,
			preview: computeWith(false),
			status,
			// A fresh subscriber gets the CURRENT status immediately, then one frame per
			// engine transition — so the console's live view is right the moment it
			// connects, rather than blank until the next sync. Each frame is a full
			// snapshot, so the sliver between the two stages costs nothing.
			statusChanges: Stream.concat(
				Stream.fromEffect(status),
				engine.changes.pipe(Stream.mapEffect(() => status)),
			),
			locate: loadOrDefault.pipe(Effect.map(locateExport)),
			art,
		} satisfies PlayniteSyncService;
	});
}