import { describe, expect, it } from "vitest";
import {
	appendSessionEntryStructure,
	packSessionEntryStructure,
	readSessionEntryStructure,
	SESSION_ENTRY_STRUCTURE_RECORD_BYTES,
	type SessionEntryStructure,
} from "../src/core/session-entry-structure.js";

function record(overrides: Partial<SessionEntryStructure> = {}): SessionEntryStructure {
	return {
		id: "24ba855c",
		parentId: null,
		type: "message",
		role: "user",
		timestampMs: 1_769_000_000_123,
		offset: 100,
		length: 250,
		...overrides,
	};
}

describe("packed session entry structure", () => {
	it("round-trips every field", () => {
		const records = [
			record(),
			record({
				id: "01a09d7f",
				parentId: "24ba855c",
				type: "custom_message",
				role: "toolResult",
				timestampMs: null,
				offset: 351,
				length: 1_100_000,
			}),
			record({ id: "ffffffff", parentId: "01a09d7f", type: "compaction", role: null, timestampMs: 1.5 }),
		];
		const blob = packSessionEntryStructure(records);
		expect(blob).toBeDefined();
		expect(blob!.length).toBe(8 + records.length * SESSION_ENTRY_STRUCTURE_RECORD_BYTES);
		expect(readSessionEntryStructure(blob)).toEqual(records);
	});

	it("keeps an unknown role but refuses an unknown entry type", () => {
		const packed = packSessionEntryStructure([record({ role: "future-role" })]);
		expect(readSessionEntryStructure(packed)[0]!.role).toBe("other");
		expect(packSessionEntryStructure([record({ type: "future-type" })])).toBeUndefined();
	});

	it("refuses ids that are not 16 hex characters", () => {
		expect(packSessionEntryStructure([record({ id: "not-a-hex-id" })])).toBeUndefined();
		expect(packSessionEntryStructure([record({ parentId: "01a09d7f-8494" })])).toBeUndefined();
		expect(packSessionEntryStructure([record({ parentId: "24ba855c" })])).toBeDefined();
	});

	it("appends records without rewriting the earlier ones", () => {
		const first = packSessionEntryStructure([record()])!;
		const appended = appendSessionEntryStructure(first, 351, [record({ id: "aaaaaaaa", offset: 351 })])!;
		expect(readSessionEntryStructure(appended).map((entry) => entry.id)).toEqual(["24ba855c", "aaaaaaaa"]);
		expect(
			readSessionEntryStructure(appendSessionEntryStructure(first, 0, [record({ id: "bbbbbbbb" })])!).map(
				(e) => e.id,
			),
		).toEqual(["bbbbbbbb"]);
		expect(appendSessionEntryStructure(undefined, 0, [record({ id: "no" })])).toBeUndefined();
	});

	it("reads nothing from a truncated or unknown blob", () => {
		expect(readSessionEntryStructure(null)).toEqual([]);
		expect(readSessionEntryStructure(Buffer.alloc(4))).toEqual([]);
		const blob = packSessionEntryStructure([record(), record({ id: "aaaaaaaa" })])!;
		expect(readSessionEntryStructure(blob.subarray(0, blob.length - 1))).toHaveLength(1);
		const future = Buffer.from(blob);
		future[0] = 99;
		expect(readSessionEntryStructure(future)).toEqual([]);
	});
});