import { readdirSync, readFileSync } from "node:fs";
import { join } from "node:path";
import { getAgentDir } from "@earendil-works/pi-coding-agent";
import { startOfCurrentWeekLocal } from "./week.ts";

const SCAN_CACHE_TTL_MS = 60_000; // 1 minute
let scanCache: { providerName: string; sessionsDir: string; weekStartMs: number; total: number; fetchedAt: number } | null = null;

export function scanWeeklyTokens(providerName: string): number {
	const sessionsDir = join(getAgentDir(), "sessions");
	const weekStartMs = startOfCurrentWeekLocal();

	// Return cached result if still valid for the same week window and sessions dir
	if (
		scanCache &&
		scanCache.providerName === providerName &&
		scanCache.sessionsDir === sessionsDir &&
		scanCache.weekStartMs === weekStartMs &&
		Date.now() - scanCache.fetchedAt < SCAN_CACHE_TTL_MS
	) {
		return scanCache.total;
	}

	let total = 0;

	try {
		const dirs = readdirSync(sessionsDir, { withFileTypes: true });
		for (const dir of dirs) {
			if (!dir.isDirectory()) continue;
			const dirPath = join(sessionsDir, dir.name);
			let files: string[];
			try {
				files = readdirSync(dirPath);
			} catch {
				continue;
			}
			for (const fname of files) {
				if (!fname.endsWith(".jsonl")) continue;
				try {
					const fileDate = new Date(fname.slice(0, 10) + "T00:00:00");
					if (fileDate.getTime() < weekStartMs) continue;
				} catch {
					continue;
				}

				try {
					const content = readFileSync(join(dirPath, fname), "utf-8");
					for (const line of content.split("\n")) {
						if (!line.trim()) continue;
						try {
							const d = JSON.parse(line);
							if (
								d.type === "message" &&
								d.message?.role === "assistant" &&
								d.message?.provider === providerName
							) {
								total += d.message.usage?.totalTokens ?? 0;
							}
						} catch {
							// skip malformed lines
						}
					}
				} catch {
					// skip unreadable files
				}
			}
		}
	} catch {
		// sessions dir doesn't exist or is unreadable
	}

	scanCache = { providerName, sessionsDir, weekStartMs, total, fetchedAt: Date.now() };
	return total;
}