/**
 * Session document cache benchmark. A Harness on SQLite creates N conversations and runs one short task in each, as a
 * long-running agent with subagents does; then, at a few retention settings, reports the documents left in the cache,
 * the bytes live objects retain (from heap snapshots) per conversation, and the cost of reading a document of an old conversation again.
 *
 *   node --conditions=source --experimental-strip-types test/session-document-cache-bench.ts [N...]
 */
import { mkdtempSync, rmSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { BACKGROUND_CONTEXT as context } from "@earendil-works/chord/context";
import { createModels } from "@earendil-works/pi-ai/models";
import {
	type ConversationId,
	createRegistry,
	defineExtension,
	defineTask,
	Harness,
	LiveDoc,
	UsageDoc,
} from "../src/index.ts";
import type { SessionImpl } from "../src/session/session.ts";
import { openNodeSqliteStorage } from "../src/storage/sqlite/node.ts";
import { retainedBytes } from "./heap-retained.ts";

/** Writes `pi.usage` of its conversation once, then completes. */
const Work = defineTask<null, { phase: "work" }, null>({
	name: "bench.work",
	version: 1,
	initial: () => ({ phase: "work" }),
	phases: {
		work: async (_task, runtime, ctx) =>
			runtime.commit(async (tx) => {
				(await tx.doc(UsageDoc, runtime.conversationId)).tools.bench = { input: 1 } as never;
				return { status: "terminal", outcome: { status: "completed", result: null } };
			}, ctx),
	},
	abort: async (_task, runtime, ctx) =>
		runtime.commit(() => ({ status: "terminal", outcome: { status: "aborted" } }), ctx),
});

async function run(conversations: number, documentRetentionMs: number) {
	const directory = mkdtempSync(join(tmpdir(), "pi-durable-doc-cache-bench-"));
	try {
		const storage = await openNodeSqliteStorage(join(directory, "session.sqlite"));
		const registry = createRegistry();
		registry.install(defineExtension({ name: "bench", tasks: [Work] }));
		const harness = await Harness.open(
			storage,
			{ models: createModels(), registry, settings: { documentRetentionMs } },
			context,
		);
		harness.resume();
		let first: ConversationId | undefined;
		const cycle = async (): Promise<void> => {
			const conversation = await harness.createConversation({ ownership: { kind: "ownerless" } }, context);
			first ??= conversation.id;
			const task = await conversation.commit(
				(tx) => tx.createTask(Work, null, { ownership: { kind: "conversation" } }),
				context,
			);
			const settled = await harness.waitForTask(task, context);
			if (settled.state.outcome.status !== "completed")
				throw new Error(`task ${task} ${settled.state.outcome.status}`);
		};
		// Warm up first: compiled code and storage caches would otherwise count as growth.
		for (let n = 0; n < 200; n++) await cycle();
		await (harness as unknown as SessionImpl).readOnLine(async () => {});
		const heapBefore = await retainedBytes();
		const started = performance.now();
		for (let n = 0; n < conversations; n++) await cycle();
		const ms = Math.round(performance.now() - started);
		// Wait past a short retention without committing, so only the timer can evict; then let its job run.
		if (documentRetentionMs > 0 && documentRetentionMs < 1_000) {
			await new Promise((resolve) => setTimeout(resolve, documentRetentionMs * 4));
		}
		await (harness as unknown as SessionImpl).readOnLine(async () => {});
		const heap = (await retainedBytes()) - heapBefore;
		const cached = (harness as unknown as SessionImpl).documentCacheSizes.cached;
		// One read of an old conversation's document: from the cache, or from storage after eviction.
		const readStarted = performance.now();
		for (let n = 0; n < 100; n++) await harness.snapshot(LiveDoc, first!, context);
		const readUs = Math.round(((performance.now() - readStarted) / 100) * 1000);
		await harness.close(context);
		return { ms, heap, cached, readUs };
	} finally {
		rmSync(directory, { recursive: true, force: true });
	}
}

const sizes = process.argv.slice(2).map(Number);
console.log("conversations | retention   | ms     | cached docs | retained bytes        | old-doc read");
for (const n of sizes.length > 0 ? sizes : [1000, 5000]) {
	for (const [label, retention] of [
		["infinite", Number.MAX_SAFE_INTEGER],
		["10 min", 600_000],
		["50 ms", 50],
		["0", 0],
	] as const) {
		const { ms, heap, cached, readUs } = await run(n, retention);
		console.log(
			`${String(n).padEnd(13)} | ${label.padEnd(11)} | ${String(ms).padEnd(6)} | ${String(cached).padEnd(11)} | ${`${(heap / 1024 / 1024).toFixed(1)} MiB, ${Math.round(heap / n)} B/conv`.padEnd(21)} | ${readUs} µs`,
		);
	}
}