"use strict";

window.VK = window.VK ?? {};

const bus = new Map();

window.VK.bus = {
    on(type, handler) {
        const handlers = bus.get(type) ?? new Set();
        handlers.add(handler);
        bus.set(type, handlers);
        return () => handlers.delete(handler);
    },
    emit(type, payload) {
        for (const handler of bus.get(type) ?? []) {
            try {
                handler(payload);
            } catch (error) {
                console.error(`[bus] ${type} handler failed`, error);
            }
        }
    }
};

async function request(path, options) {
    const response = await fetch(path, options);
    let body;
    try {
        body = await response.json();
    } catch {
        throw new Error(`request failed (${response.status})`);
    }
    if (!body.ok) throw new Error(body.error ?? `request failed (${response.status})`);
    return body.result;
}

window.VK.api = {
    get: path => request(path),
    post: (path, data) =>
        request(path, {
            method: "POST",
            headers: { "Content-Type": "application/json" },
            body: JSON.stringify(data ?? {})
        })
};

window.VK.connectEvents = function connectEvents() {
    const source = new EventSource("/api/events");

    source.onmessage = message => {
        let data;
        try {
            data = JSON.parse(message.data);
        } catch {
            return;
        }
        window.VK.bus.emit("event", data);
    };

    source.onerror = () => window.VK.bus.emit("sse-error");
};