/**
 * CS Reporting — shared datetime display for tables and audit/history UI.
 *
 * API/SQL timestamps from SYSUTCDATETIME (and similar) are UTC. Naive ISO strings
 * without Z/offset must be treated as UTC, then shown in the browser's local timezone.
 *
 * Today (browser local calendar day): time only (HH:mm:ss).
 * Other days: YYYY-MM-DD HH:mm:ss (no ISO "T" separator).
 */
(function (global) {
    'use strict';

    function pad2(n) {
        return n < 10 ? '0' + n : String(n);
    }

    /**
     * Parse API/SQL datetime as an absolute instant.
     * Naive values (no Z / offset) are assumed UTC — matching SQL SYSUTCDATETIME storage.
     */
    function parseDateTime(value) {
        if (value === null || value === undefined) {
            return null;
        }
        let text = String(value).trim();
        if (!text) {
            return null;
        }

        // Date-only: treat as UTC midnight so local display is consistent.
        if (/^\d{4}-\d{2}-\d{2}$/.test(text)) {
            const dOnly = new Date(text + 'T00:00:00Z');
            return Number.isNaN(dOnly.getTime()) ? null : dOnly;
        }

        const hasZone = /[zZ]$/.test(text) || /[+-]\d{2}:?\d{2}$/.test(text);
        if (text.indexOf(' ') >= 0 && text.indexOf('T') < 0) {
            text = text.replace(' ', 'T');
        }
        // Strip trailing whitespace-only; keep fractional seconds; append Z when naive.
        if (!hasZone && /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}/.test(text)) {
            text = text + 'Z';
        }

        const d = new Date(text);
        if (Number.isNaN(d.getTime())) {
            return null;
        }
        return d;
    }

    function isSameLocalDay(a, b) {
        return a.getFullYear() === b.getFullYear()
            && a.getMonth() === b.getMonth()
            && a.getDate() === b.getDate();
    }

    /**
     * @param {string|null|undefined} value ISO or SQL datetime from API (UTC when naive)
     * @param {string} [emptyFallback='—'] shown when value is empty
     * @returns {string} Browser-local display string
     */
    function formatDisplayDateTime(value, emptyFallback) {
        const fallback = emptyFallback === undefined ? '—' : emptyFallback;
        const d = parseDateTime(value);
        if (!d) {
            if (value === null || value === undefined || String(value).trim() === '') {
                return fallback;
            }
            return String(value);
        }
        // getHours/getDate use the viewer's local timezone (e.g. GMT/BST in the UK).
        const hh = pad2(d.getHours());
        const mm = pad2(d.getMinutes());
        const ss = pad2(d.getSeconds());
        const now = new Date();
        if (isSameLocalDay(d, now)) {
            return hh + ':' + mm + ':' + ss;
        }
        const yyyy = d.getFullYear();
        const mo = pad2(d.getMonth() + 1);
        const dd = pad2(d.getDate());
        return yyyy + '-' + mo + '-' + dd + ' ' + hh + ':' + mm + ':' + ss;
    }

    global.CSReporting = global.CSReporting || {};
    global.CSReporting.formatDisplayDateTime = formatDisplayDateTime;
    global.CSReporting.parseApiDateTime = parseDateTime;
}(typeof window !== 'undefined' ? window : this));