// spindle websocket log stream
// replays from line one on connect and closes when all workflows settle

import { decodeFirst } from "@atcute/cbor";
import { spindleUrl } from "$lib/api/spindle";
import type * as SubscribeLogs from "$lib/api/lexicons/types/sh/tangled/ci/subscribePipelineLogs";

export type LogControl = SubscribeLogs.Control;

export type LogData = SubscribeLogs.Data;

export type LogFrame =
	| { kind: "control"; control: LogControl }
	| { kind: "data"; data: LogData }
	| { kind: "error"; error: string; message: string };

// indigo event header ops
const OP_MESSAGE = 1;
const OP_ERROR = -1;

const asRecord = (value: unknown): Record<string, unknown> =>
	typeof value === "object" && value !== null ? (value as Record<string, unknown>) : {};

const str = (value: unknown): string => (typeof value === "string" ? value : "");

// decodes binary websocket frame into dag-cbor header and body
export const decodeLogFrame = (bytes: Uint8Array): LogFrame | null => {
	const [rawHeader, rest] = decodeFirst(bytes);
	const header = asRecord(rawHeader);
	if (header.op !== OP_MESSAGE && header.op !== OP_ERROR) return null;

	const [rawBody] = decodeFirst(rest);
	const body = asRecord(rawBody);

	if (header.op === OP_ERROR) {
		return { kind: "error", error: str(body.error), message: str(body.message) };
	}

	switch (header.t) {
		case "#control":
			return { kind: "control", control: body as unknown as LogControl };
		case "#data":
			return { kind: "data", data: body as unknown as LogData };
		default:
			return null;
	}
};

export const pipelineLogsUrl = (host: string, pipeline: string, workflows: string[]): string => {
	const url = new URL(
		"/xrpc/sh.tangled.ci.subscribePipelineLogs",
		`${spindleUrl(host).replace(/^http/, "ws")}/`
	);
	url.searchParams.set("pipeline", pipeline);
	for (const workflow of workflows) url.searchParams.append("workflows", workflow);
	return url.toString();
};

export interface LogStreamHandlers {
	onFrame: (frame: LogFrame) => void;
	onClose?: (clean: boolean) => void;
}

// opens log subscription, returns teardown function
export const subscribePipelineLogs = (
	host: string,
	pipeline: string,
	workflows: string[],
	handlers: LogStreamHandlers
): (() => void) => {
	const socket = new WebSocket(pipelineLogsUrl(host, pipeline, workflows));
	socket.binaryType = "arraybuffer";
	let live = true;

	socket.onmessage = (event: MessageEvent<ArrayBuffer | string>) => {
		if (!live || typeof event.data === "string") return;
		const frame = decodeLogFrame(new Uint8Array(event.data));
		if (frame) handlers.onFrame(frame);
	};

	socket.onclose = (event: CloseEvent) => {
		if (!live) return;
		live = false;
		handlers.onClose?.(event.wasClean);
	};

	// refused upgrades trigger an error then close, close handler handles it
	socket.onerror = () => {};

	return () => {
		live = false;
		socket.close();
	};
};