import * as fs from "node:fs";
import { isCompiledBinary } from "@oh-my-pi/pi-utils";
import {
	getRecentErrors as dbGetRecentErrors,
	getRecentRequests as dbGetRecentRequests,
	getBehaviorByModel,
	getBehaviorOverall,
	getBehaviorTimeSeries,
	getCostTimeSeries,
	getFileOffset,
	getMessageById,
	getMessageCount,
	getModelPerformanceSeries,
	getModelTimeSeries,
	getOverallStats,
	getStatsByFolder,
	getStatsByModel,
	getTimeSeries,
	initDb,
	insertMessageStats,
	insertUserMessageStats,
	setFileOffset,
	updateUserMessageLinks,
} from "./db";
import { getSessionEntry, listAllSessionFiles, type ParseSessionResult } from "./parser";
import type { SyncWorkerRequest, SyncWorkerResponse } from "./sync-worker";
// Worker entry. Bun's `--compile` bundler statically discovers the string
// literal in `new Worker("./packages/stats/src/sync-worker.ts", …)` below and
// emits the worker as an additional entrypoint (registered in
// `packages/coding-agent/scripts/build-binary.ts`). In dev runs we resolve
// the same source file through `import.meta.url`, so the literal only has to
// be valid relative to the `--root` directory (repo root). Importing the
// source as `with { type: "file" }` is NOT sufficient — that copies the file
// as a raw asset and does not bundle the worker's relative imports, so the
// worker would crash on first `import` (issue #1011, PR #1027).
import type { BehaviorDashboardStats, DashboardStats, MessageStats, RequestDetails } from "./types";

/**
 * Apply a freshly parsed result to the database. Runs entirely on the
 * main thread so the single SQLite handle owns every write.
 */
function applyParseResult(sessionFile: string, lastModified: number, result: ParseSessionResult): number {
	if (result.stats.length > 0) insertMessageStats(result.stats);
	if (result.userStats.length > 0) insertUserMessageStats(result.userStats);
	if (result.userLinks.length > 0) updateUserMessageLinks(result.userLinks);
	setFileOffset(sessionFile, result.newOffset, lastModified);
	return result.stats.length + result.userStats.length;
}

/**
 * Progress event emitted after each session file is fully processed.
 * `current` is the number of files completed (skipped + parsed),
 * `total` is the size of the work set. `processed` is the running total
 * of inserted rows.
 */
export interface SyncProgress {
	current: number;
	total: number;
	processed: number;
	sessionFile: string;
}

export interface SyncOptions {
	/** Called after each file completes. Synchronous; keep it cheap. */
	onProgress?: (event: SyncProgress) => void;
	/**
	 * Worker pool size. Defaults to a sensible value derived from the host
	 * (capped to avoid drowning a small machine in workers). Set to `1` to
	 * force serial parsing without spawning workers.
	 */
	workers?: number;
}

function defaultWorkerCount(): number {
	// `navigator.hardwareConcurrency` is the portable answer in Bun; fall
	// back to a small fixed pool if it's somehow unavailable.
	const hw = typeof navigator !== "undefined" ? (navigator.hardwareConcurrency ?? 0) : 0;
	const raw = hw > 0 ? hw : 4;
	// Cap at 8 - parse is JSON-bound, and SQLite writes serialize on main
	// thread anyway, so more workers stop helping.
	return Math.min(8, Math.max(2, Math.floor(raw)));
}

interface WorkerHandle {
	worker: Worker;
	busy: boolean;
	resolve: ((res: ParseSessionResult) => void) | null;
	reject: ((err: Error) => void) | null;
}

/**
 * Create a fresh sync worker. In a `--compile` binary the literal-string
 * specifier is what Bun's static analyzer needs (the file is also listed as
 * an additional `--compile` entrypoint in
 * `packages/coding-agent/scripts/build-binary.ts`). In dev runs we resolve
 * the source URL via `import.meta.url` so the worker survives `cwd` changes
 * by callers.
 */
function createSyncWorker(): Worker {
	return isCompiledBinary()
		? new Worker("./packages/stats/src/sync-worker.ts", { type: "module" })
		: new Worker(new URL("./sync-worker.ts", import.meta.url).href, { type: "module" });
}

function spawnWorker(): WorkerHandle {
	const worker = createSyncWorker();
	const handle: WorkerHandle = { worker, busy: false, resolve: null, reject: null };
	worker.onmessage = (event: MessageEvent<SyncWorkerResponse>) => {
		const { resolve, reject } = handle;
		handle.resolve = null;
		handle.reject = null;
		handle.busy = false;
		if (!resolve || !reject) return;
		const data = event.data;
		if (!data.ok) {
			reject(new Error(data.error));
			return;
		}
		if (data.kind === "pong") {
			reject(new Error("sync worker: unexpected pong on parse channel"));
			return;
		}
		resolve(data.result);
	};
	worker.onerror = (event: ErrorEvent) => {
		const { reject } = handle;
		handle.resolve = null;
		handle.reject = null;
		handle.busy = false;
		reject?.(event.error instanceof Error ? event.error : new Error(event.message || "worker error"));
	};
	return handle;
}

function dispatch(handle: WorkerHandle, request: SyncWorkerRequest): Promise<ParseSessionResult> {
	if (handle.busy) {
		return Promise.reject(new Error("worker is busy - this is a bug in the dispatcher"));
	}
	const { promise, resolve, reject } = Promise.withResolvers<ParseSessionResult>();
	handle.busy = true;
	handle.resolve = resolve;
	handle.reject = reject;
	handle.worker.postMessage(request);
	return promise;
}

/**
 * Smoke test: spawns one sync worker, pings it, asserts the pong response,
 * then terminates. Used by `omp --smoke-test` so the install-method CI jobs
 * catch the silent worker-load failure that hit compiled binaries in #1011
 * and #1027 — neither `--version` nor `stats --summary` exercises the worker
 * spawn path on a fresh install (no session files = early return), so a
 * dedicated probe is the only reliable signal.
 *
 * Resolves with the worker's `import.meta.url` (caller-visible diagnostics);
 * rejects on transport error, error response, or timeout.
 */
export async function smokeTestSyncWorker({ timeoutMs = 5_000 }: { timeoutMs?: number } = {}): Promise<void> {
	const worker = createSyncWorker();
	const { promise, resolve, reject } = Promise.withResolvers<void>();
	const timer = setTimeout(() => reject(new Error(`sync worker did not pong within ${timeoutMs}ms`)), timeoutMs);
	worker.onmessage = (event: MessageEvent<SyncWorkerResponse>) => {
		const data = event.data;
		if (!data.ok) {
			reject(new Error(data.error));
			return;
		}
		if (data.kind !== "pong") {
			reject(new Error(`sync worker: expected pong, got ${JSON.stringify(data)}`));
			return;
		}
		resolve();
	};
	worker.onerror = (event: ErrorEvent) => {
		reject(event.error instanceof Error ? event.error : new Error(event.message || "worker error"));
	};
	try {
		worker.postMessage({ kind: "ping" } satisfies SyncWorkerRequest);
		await promise;
	} finally {
		clearTimeout(timer);
		worker.terminate();
	}
}

/**
 * Sync all session files to the database.
 *
 * Parsing fans out across a worker pool (one in-flight job per worker)
 * while DB writes and offset bookkeeping stay on the calling thread so the
 * single SQLite handle stays uncontended. `onProgress` fires once per
 * completed file (skipped files included so the bar walks at a steady
 * rate).
 */
export async function syncAllSessions(opts?: SyncOptions): Promise<{ processed: number; files: number }> {
	await initDb();

	const files = await listAllSessionFiles();
	if (files.length === 0) return { processed: 0, files: 0 };

	let totalProcessed = 0;
	let filesProcessed = 0;
	let completed = 0;
	let cursor = 0;

	const poolSize = Math.max(1, Math.min(files.length, opts?.workers ?? defaultWorkerCount()));
	const handles: WorkerHandle[] = [];
	for (let i = 0; i < poolSize; i++) handles.push(spawnWorker());

	const report = (sessionFile: string) => {
		completed++;
		opts?.onProgress?.({
			current: completed,
			total: files.length,
			processed: totalProcessed,
			sessionFile,
		});
	};

	async function drain(handle: WorkerHandle): Promise<void> {
		while (true) {
			const idx = cursor++;
			if (idx >= files.length) return;
			const sessionFile = files[idx];

			let fileStats: fs.Stats;
			try {
				fileStats = await fs.promises.stat(sessionFile);
			} catch {
				report(sessionFile);
				continue;
			}
			const lastModified = fileStats.mtimeMs;
			const stored = getFileOffset(sessionFile);
			if (stored && stored.lastModified >= lastModified) {
				report(sessionFile);
				continue;
			}

			const fromOffset = stored?.offset ?? 0;
			const result = await dispatch(handle, { sessionFile, fromOffset });
			const inserted = applyParseResult(sessionFile, lastModified, result);
			if (inserted > 0) {
				totalProcessed += inserted;
				filesProcessed++;
			}
			report(sessionFile);
		}
	}

	try {
		await Promise.all(handles.map(drain));
	} finally {
		for (const handle of handles) handle.worker.terminate();
	}

	return { processed: totalProcessed, files: filesProcessed };
}

const HOUR_MS = 60 * 60 * 1000;
const DAY_MS = 24 * HOUR_MS;

type TimeRange = "1h" | "24h" | "7d" | "30d" | "90d" | "all";

interface TimeRangeConfig {
	timeSeriesHours: number;
	timeSeriesBucketMs: number;
	modelSeriesDays: number;
	modelSeriesBucketMs: number;
	modelPerformanceDays: number;
	modelPerformanceBucketMs: number;
	costSeriesDays: number;
	cutoff: number | null;
}

const DEFAULT_TIME_RANGE: TimeRange = "24h";

const TIME_RANGE_TO_CONFIG: Record<TimeRange, Omit<TimeRangeConfig, "cutoff">> = {
	"1h": {
		timeSeriesHours: 1,
		timeSeriesBucketMs: HOUR_MS,
		modelSeriesDays: 1,
		modelSeriesBucketMs: HOUR_MS,
		modelPerformanceDays: 1,
		modelPerformanceBucketMs: HOUR_MS,
		costSeriesDays: 1,
	},
	"24h": {
		timeSeriesHours: 24,
		timeSeriesBucketMs: HOUR_MS,
		modelSeriesDays: 1,
		modelSeriesBucketMs: HOUR_MS,
		modelPerformanceDays: 1,
		modelPerformanceBucketMs: HOUR_MS,
		costSeriesDays: 1,
	},
	"7d": {
		timeSeriesHours: 24 * 7,
		timeSeriesBucketMs: DAY_MS,
		modelSeriesDays: 7,
		modelSeriesBucketMs: DAY_MS,
		modelPerformanceDays: 7,
		modelPerformanceBucketMs: DAY_MS,
		costSeriesDays: 7,
	},
	"30d": {
		timeSeriesHours: 24 * 30,
		timeSeriesBucketMs: DAY_MS,
		modelSeriesDays: 30,
		modelSeriesBucketMs: DAY_MS,
		modelPerformanceDays: 30,
		modelPerformanceBucketMs: DAY_MS,
		costSeriesDays: 30,
	},
	"90d": {
		timeSeriesHours: 24 * 90,
		timeSeriesBucketMs: DAY_MS,
		modelSeriesDays: 90,
		modelSeriesBucketMs: DAY_MS,
		modelPerformanceDays: 90,
		modelPerformanceBucketMs: DAY_MS,
		costSeriesDays: 90,
	},
	all: {
		timeSeriesHours: 24 * 3650,
		timeSeriesBucketMs: DAY_MS,
		modelSeriesDays: 3650,
		modelSeriesBucketMs: DAY_MS,
		modelPerformanceDays: 3650,
		modelPerformanceBucketMs: DAY_MS,
		costSeriesDays: 3650,
	},
};

function getTimeRangeConfig(range?: string | null): TimeRangeConfig {
	const normalized = range?.trim().toLowerCase() ?? DEFAULT_TIME_RANGE;
	const config = TIME_RANGE_TO_CONFIG[normalized as TimeRange];
	if (config) {
		const cutoff = normalized === "all" ? null : Date.now() - Math.max(1, config.timeSeriesHours * 60 * 60 * 1000);
		return { ...config, cutoff };
	}

	const fallbackConfig = TIME_RANGE_TO_CONFIG[DEFAULT_TIME_RANGE];
	return {
		...fallbackConfig,
		cutoff: Date.now() - fallbackConfig.timeSeriesHours * 60 * 60 * 1000,
	};
}

/**
 * Get all dashboard stats.
 */
export async function getDashboardStats(range?: string | null): Promise<DashboardStats> {
	await initDb();
	const {
		timeSeriesHours,
		timeSeriesBucketMs,
		modelSeriesDays,
		modelSeriesBucketMs,
		modelPerformanceDays,
		modelPerformanceBucketMs,
		costSeriesDays,
		cutoff,
	} = getTimeRangeConfig(range);

	return {
		overall: getOverallStats(cutoff ?? undefined),
		byModel: getStatsByModel(cutoff ?? undefined),
		byFolder: getStatsByFolder(cutoff ?? undefined),
		timeSeries: getTimeSeries(timeSeriesHours, cutoff, timeSeriesBucketMs),
		modelSeries: getModelTimeSeries(modelSeriesDays, cutoff, modelSeriesBucketMs),
		modelPerformanceSeries: getModelPerformanceSeries(modelPerformanceDays, cutoff, modelPerformanceBucketMs),
		costSeries: getCostTimeSeries(costSeriesDays, cutoff),
	};
}

export async function getOverviewStats(range?: string | null): Promise<Pick<DashboardStats, "overall" | "timeSeries">> {
	await initDb();
	const { timeSeriesHours, timeSeriesBucketMs, cutoff } = getTimeRangeConfig(range);

	return {
		overall: getOverallStats(cutoff ?? undefined),
		timeSeries: getTimeSeries(timeSeriesHours, cutoff, timeSeriesBucketMs),
	};
}

export async function getModelDashboardStats(
	range?: string | null,
): Promise<Pick<DashboardStats, "byModel" | "modelSeries" | "modelPerformanceSeries">> {
	await initDb();
	const { modelSeriesDays, modelSeriesBucketMs, modelPerformanceDays, modelPerformanceBucketMs, cutoff } =
		getTimeRangeConfig(range);

	return {
		byModel: getStatsByModel(cutoff ?? undefined),
		modelSeries: getModelTimeSeries(modelSeriesDays, cutoff, modelSeriesBucketMs),
		modelPerformanceSeries: getModelPerformanceSeries(modelPerformanceDays, cutoff, modelPerformanceBucketMs),
	};
}

export async function getCostDashboardStats(range?: string | null): Promise<Pick<DashboardStats, "costSeries">> {
	await initDb();
	const { costSeriesDays, cutoff } = getTimeRangeConfig(range);

	return {
		costSeries: getCostTimeSeries(costSeriesDays, cutoff),
	};
}
export async function getRecentRequests(limit?: number): Promise<MessageStats[]> {
	await initDb();
	return dbGetRecentRequests(limit);
}

export async function getRecentErrors(limit?: number): Promise<MessageStats[]> {
	await initDb();
	return dbGetRecentErrors(limit);
}

export async function getRequestDetails(id: number): Promise<RequestDetails | null> {
	await initDb();
	const msg = getMessageById(id);
	if (!msg) return null;

	const entry = await getSessionEntry(msg.sessionFile, msg.entryId);
	if (entry?.type !== "message") return null;

	// TODO: Get parent/context messages?
	// For now we return the single entry which contains the assistant response.
	// The user prompt is likely the parent.

	return {
		...msg,
		messages: [entry],
		output: (entry as any).message,
	};
}

/**
 * Get the current message count in the database.
 */
export async function getTotalMessageCount(): Promise<number> {
	await initDb();
	return getMessageCount();
}

export async function getBehaviorDashboardStats(range?: string | null): Promise<BehaviorDashboardStats> {
	await initDb();
	const { cutoff } = getTimeRangeConfig(range);
	return {
		overall: getBehaviorOverall(cutoff),
		byModel: getBehaviorByModel(cutoff),
		behaviorSeries: getBehaviorTimeSeries(cutoff),
	};
}