/* Common helpers shared across pages (ES module). */

/** Debounce a function call. */
export function debounce(fn, delay) {
    let timer = null;
    return function (...args) {
        clearTimeout(timer);
        timer = setTimeout(() => fn.apply(this, args), delay);
    };
}

/** Format an ISO date string to YYYY-MM-DD. */
export function formatDate(isoString) {
    if (!isoString) return "";
    const d = new Date(isoString);
    if (isNaN(d.getTime())) return String(isoString).slice(0, 10);
    const y = d.getFullYear();
    const m = String(d.getMonth() + 1).padStart(2, "0");
    const day = String(d.getDate()).padStart(2, "0");
    return `${y}-${m}-${day}`;
}

/** Truncate text to maxLen chars, appending ellipsis. */
export function truncate(text, maxLen) {
    if (!text) return "";
    const s = String(text);
    return s.length > maxLen ? s.slice(0, maxLen) + "…" : s;
}

/** Escape HTML special chars to prevent XSS when injecting via innerHTML. */
export function escapeHtml(text) {
    if (text === null || text === undefined) return "";
    return String(text)
        .replace(/&/g, "&")
        .replace(/</g, "&lt;")
        .replace(/>/g, "&gt;")
        .replace(/"/g, "&quot;")
        .replace(/'/g, "&#39;");
}

/** Read the session CSRF token rendered into <meta name="csrf-token">. */
export function getCsrf() {
    const meta = document.querySelector('meta[name="csrf-token"]');
    return meta ? meta.content : "";
}

/** Fetch JSON with basic error handling. */
export async function fetchJson(url) {
    const resp = await fetch(url);
    if (!resp.ok) {
        throw new Error(`请求失败: ${resp.status} ${resp.statusText}`);
    }
    return resp.json();
}

/** POST JSON, injecting csrf_token into the body. Returns parsed JSON. */
export async function postJson(url, data) {
    const resp = await fetch(url, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ ...data, csrf_token: getCsrf() }),
    });
    const body = await resp.json().catch(() => ({}));
    if (!resp.ok) {
        throw new Error(body.error || `请求失败: ${resp.status}`);
    }
    return body;
}

/** Render a dismissible error alert into a container element. */
export function showError(container, msg) {
    if (!container) return;
    container.innerHTML =
        '<div class="alert alert-danger alert-dismissible fade show" role="alert">'
        + escapeHtml(msg)
        + '<button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button></div>';
}