import { Hono } from "hono";
import { stream } from "hono/streaming";
import { getAllConfig, getConfig, getDb, setConfig } from "../db/index";
import { log, error as logError } from "../lib/log";
import { discoverVideoFiles } from "../services/discover";
import { parsePath } from "../services/path-parser";
import { probeFile } from "../services/probe";
import { upsertScannedItem } from "../services/rescan";
import { emitPipelineChanged } from "./execute";
import { isInScanWindow, msUntilScanWindow, nextScanWindowTime, waitForScanWindow } from "../services/scheduler";

const app = new Hono();

/**
 * Validate a scan `limit` input. Must be a positive integer or absent —
 * NaN/negatives/non-numerics would disable the progress cap
 * (`processed >= NaN` never trips) or produce bogus totals via
 * `Math.min(NaN, …)`. Exported for unit tests.
 */
export function parseScanLimit(raw: unknown): { ok: true; value: number | null } | { ok: false } {
	if (raw == null || raw === "") return { ok: true, value: null };
	const n = typeof raw === "number" ? raw : Number(raw);
	if (!Number.isInteger(n) || n <= 0) return { ok: false };
	return { ok: true, value: n };
}

// ─── State ────────────────────────────────────────────────────────────────────

let scanAbort: AbortController | null = null;
const scanListeners = new Set<(data: string) => void>();

function emitSse(type: string, data: unknown): void {
	const line = `event: ${type}\ndata: ${JSON.stringify(data)}\n\n`;
	for (const listener of scanListeners) listener(line);
}

function currentScanLimit(): number | null {
	const v = getConfig("scan_limit");
	return v ? Number(v) : null;
}

// ─── Status ───────────────────────────────────────────────────────────────────

app.get("/", (c) => {
	const db = getDb();
	const running = getConfig("scan_running") === "1";
	const total = (db.prepare("SELECT COUNT(*) as n FROM media_items").get() as { n: number }).n;
	const scanned = (
		db.prepare("SELECT COUNT(*) as n FROM media_items WHERE scan_status = 'scanned'").get() as { n: number }
	).n;
	const errors = (db.prepare("SELECT COUNT(*) as n FROM media_items WHERE scan_status = 'error'").get() as { n: number })
		.n;
	const recentItems = db
		.prepare(
			"SELECT name, type, scan_status, file_path, last_scanned_at FROM media_items ORDER BY COALESCE(last_scanned_at, created_at) DESC, id DESC LIMIT 5",
		)
		.all() as {
		name: string;
		type: string;
		scan_status: string;
		file_path: string;
		last_scanned_at: string | null;
	}[];

	return c.json({ running, progress: { scanned, total, errors }, recentItems, scanLimit: currentScanLimit() });
});

// ─── Start ────────────────────────────────────────────────────────────────────

app.post("/start", async (c) => {
	const db = getDb();
	// Atomic claim: only succeed if scan_running is not already '1'.
	const claim = db.prepare("UPDATE config SET value = '1' WHERE key = 'scan_running' AND value != '1'").run();
	if (claim.changes === 0) {
		return c.json({ ok: false, error: "Scan already running" }, 409);
	}

	const body = await c.req.json<{ limit?: unknown }>().catch(() => ({ limit: undefined }));
	const formLimit = parseScanLimit(body.limit);
	const envLimit = parseScanLimit(process.env.SCAN_LIMIT);
	if (!formLimit.ok || !envLimit.ok) {
		db.prepare("UPDATE config SET value = '0' WHERE key = 'scan_running'").run();
		return c.json({ ok: false, error: "limit must be a positive integer" }, 400);
	}
	const limit: number | null = formLimit.value ?? envLimit.value ?? null;
	setConfig("scan_limit", limit != null ? String(limit) : "");

	runScan(limit).catch((err) => {
		logError("Scan failed:", err);
		setConfig("scan_running", "0");
		emitSse("error", { message: String(err) });
	});

	return c.json({ ok: true });
});

// ─── Stop ─────────────────────────────────────────────────────────────────────

app.post("/stop", (c) => {
	scanAbort?.abort();
	setConfig("scan_running", "0");
	return c.json({ ok: true });
});

// ─── SSE ──────────────────────────────────────────────────────────────────────

app.get("/events", (c) => {
	return stream(c, async (s) => {
		c.header("Content-Type", "text/event-stream");
		c.header("Cache-Control", "no-cache");
		c.header("Connection", "keep-alive");

		const queue: string[] = [];
		let resolve: (() => void) | null = null;

		const listener = (data: string) => {
			queue.push(data);
			resolve?.();
		};

		scanListeners.add(listener);
		s.onAbort(() => {
			scanListeners.delete(listener);
		});

		try {
			while (!s.closed) {
				if (queue.length > 0) {
					await s.write(queue.shift()!);
				} else {
					await new Promise<void>((res) => {
						resolve = res;
						setTimeout(res, 25_000);
					});
					resolve = null;
					if (queue.length === 0) await s.write(": keepalive\n\n");
				}
			}
		} finally {
			scanListeners.delete(listener);
		}
	});
});

// ─── Core scan logic ──────────────────────────────────────────────────────────

async function runScan(limit: number | null = null): Promise<void> {
	log(`Scan started${limit ? ` (limit: ${limit})` : ""}`);
	scanAbort = new AbortController();
	const { signal } = scanAbort;
	const db = getDb();

	const cfg = getAllConfig();
	const moviesRoot = cfg.movies_root || "/movies";
	const tvRoot = cfg.tv_root || "/tv";

	let processed = 0;
	let errors = 0;

	emitSse("log", { message: "Discovering files..." });
	const allFiles = await discoverVideoFiles([moviesRoot, tvRoot]);
	const total = limit != null ? Math.min(limit, allFiles.length) : allFiles.length;

	emitSse("progress", { scanned: 0, total, current_item: null, errors, running: true });

	for (const filePath of allFiles) {
		if (signal.aborted) break;
		if (limit != null && processed >= limit) break;

		// Honour the scan window between items so overnight-only setups don't
		// hog the filesystem during the day. Checked between items rather than
		// mid-item so we don't leave a partial upsert in flight.
		if (!isInScanWindow()) {
			emitSse("paused", {
				until: nextScanWindowTime(),
				seconds: Math.round(msUntilScanWindow() / 1000),
			});
			await waitForScanWindow();
			if (signal.aborted) break;
			emitSse("resumed", {});
		}

		const parsed = parsePath(filePath, moviesRoot, tvRoot);
		if (!parsed) continue;

		processed++;
		emitSse("progress", { scanned: processed, total, current_item: parsed.name, errors, running: true });

		try {
			const probe = await probeFile(filePath);
			upsertScannedItem(db, filePath, parsed, probe);
			if (processed % 25 === 0) emitPipelineChanged();
			emitSse("log", { name: parsed.name, type: parsed.type, status: "scanned", file: filePath });
		} catch (err) {
			errors++;
			logError(`Error scanning ${filePath}:`, err);
			try {
				db.prepare(`
					INSERT INTO media_items (file_path, type, name, scan_status, scan_error, last_scanned_at)
					VALUES (?, ?, ?, 'error', ?, datetime('now'))
					ON CONFLICT(file_path) DO UPDATE SET scan_status = 'error', scan_error = ?, last_scanned_at = datetime('now')
				`).run(filePath, parsed.type, parsed.name, String(err), String(err));
			} catch (dbErr) {
				// Failed to persist the error status — log it so the incident
				// doesn't disappear silently.
				logError(`Failed to record scan error for ${filePath}:`, dbErr);
			}
			emitSse("log", { name: parsed.name, type: parsed.type, status: "error", file: filePath });
		}
	}

	setConfig("scan_running", "0");
	log(`Scan complete: ${processed} scanned, ${errors} errors`);
	emitSse("complete", { scanned: processed, total, errors });

	if (getConfig("auto_processing") === "1") {
		const { processInbox, getAudioLanguages } = await import("./review");
		const { emitInboxSorted, emitInboxSortStart, emitInboxSortProgress } = await import("./execute");
		processInbox(db, getAudioLanguages(), undefined, {
			onStart: emitInboxSortStart,
			onProgress: emitInboxSortProgress,
		})
			.then((result) => emitInboxSorted(result))
			.catch(() => emitInboxSorted({ moved_to_queue: 0, moved_to_review: 0 }));
	}
}

export default app;