import { describe, expect, it } from "vitest";

import {
	isViewportPinnedToBottom,
	parseResumeControlMessage,
	shouldFollowPtyOutput,
} from "./pty-scroll";

describe("isViewportPinnedToBottom", () => {
	it("is pinned when the viewport sits on the bottom row", () => {
		// xterm reports viewportY === baseY when the newest output is on screen.
		expect(isViewportPinnedToBottom({ viewportY: 120, baseY: 120 })).toBe(true);
	});

	it("releases the pin once the user scrolls up into the backlog", () => {
		// Scrolling up drops viewportY below baseY — the user is reading history,
		// so the resume replay must not yank them back down (#59591 follow-up).
		expect(isViewportPinnedToBottom({ viewportY: 40, baseY: 120 })).toBe(false);
	});

	it("stays pinned if viewportY overshoots baseY while rows are trimmed", () => {
		// scrollback eviction can momentarily push viewportY past baseY.
		expect(isViewportPinnedToBottom({ viewportY: 121, baseY: 120 })).toBe(true);
	});

	it("treats a fresh 0x0 buffer as pinned", () => {
		expect(isViewportPinnedToBottom({ viewportY: 0, baseY: 0 })).toBe(true);
	});
});

describe("shouldFollowPtyOutput", () => {
	it("follows replayed output while resuming and stuck to the bottom", () => {
		// The core #59591 fix: scroll to bottom as each replay chunk commits.
		expect(shouldFollowPtyOutput("sess-123", true)).toBe(true);
	});

	it("stops following once the user has scrolled up mid-replay", () => {
		expect(shouldFollowPtyOutput("sess-123", false)).toBe(false);
	});

	it("does not follow a fresh (non-resume) session", () => {
		// Fresh chats start empty; forcing scroll would fight normal cursor output.
		expect(shouldFollowPtyOutput(null, true)).toBe(false);
	});

	it("does not follow a fresh session even when stickToBottom is true", () => {
		expect(shouldFollowPtyOutput(null, false)).toBe(false);
	});

	it("treats an empty resume param as non-resume", () => {
		expect(shouldFollowPtyOutput("", true)).toBe(false);
	});
});

describe("parseResumeControlMessage", () => {
	it("extracts the id from a resume control frame", () => {
		// #93518: the implicit active-session fallback has no `?resume=` on the
		// URL, so the server names the session it resolved in a control frame.
		expect(
			parseResumeControlMessage('{"type":"resume","id":"sess-123"}'),
		).toBe("sess-123");
	});

	it("ignores plain ANSI banner text sent as a text frame", () => {
		// pty_ws also sends "Chat unavailable: ..." error banners as text
		// frames; those must keep rendering into the terminal, not get
		// swallowed as a (mis-parsed) control message.
		expect(
			parseResumeControlMessage("\r\n\x1b[31mChat unavailable: x\x1b[0m\r\n"),
		).toBeNull();
	});

	it("ignores JSON of the wrong shape", () => {
		expect(parseResumeControlMessage('{"type":"other","id":"x"}')).toBeNull();
		expect(parseResumeControlMessage('{"type":"resume"}')).toBeNull();
		expect(parseResumeControlMessage('{"type":"resume","id":""}')).toBeNull();
		expect(parseResumeControlMessage("null")).toBeNull();
		expect(parseResumeControlMessage('"resume"')).toBeNull();
	});
});