{{-- Shared EVA engine (linear PV, no S-curve) — aligns with Unified EVM v1.0-SIMS core formulas. --}}
<script>
window.MecEvaEngine = window.MecEvaEngine || (function () {
    'use strict';
    var DAYS_MO = 30.4375;
    var DAY_MS = 86400000;

    function fin(n) { return Number.isFinite(n); }
    function fnum(v) {
        if (v === undefined || v === null || String(v).trim() === '') return NaN;
        var n = Number(v);
        return isFinite(n) ? n : NaN;
    }
    function clamp(n, a, b) { return fin(n) ? Math.min(b, Math.max(a, n)) : NaN; }

    function compute(inp, i18n) {
        i18n = i18n || {};
        var bac = fnum(inp.bac);
        var physRaw = fnum(inp.phys);
        var pd = fnum(inp.pd);
        var ac = fnum(inp.ac);
        var startStr = String(inp.start || '').trim();
        var assessStr = String(inp.assess || '').trim();
        var eacMethod = +(inp.eacMethod || 1) || 1;
        var etcNew = fnum(inp.etcNew);

        var errors = [];
        if (!fin(bac) || bac <= 0) errors.push(i18n.errBac || 'Enter a valid project cost (BAC) greater than zero.');
        if (!fin(physRaw) || physRaw < 0 || physRaw > 100) errors.push(i18n.errPhys || 'Enter physical progress between 0 and 100%.');
        if (!fin(pd) || pd <= 0) errors.push(i18n.errDuration || 'Enter total planned duration in months (greater than zero).');
        if (!startStr) errors.push(i18n.errStart || 'Select the project start date.');
        if (!fin(ac) || ac < 0) errors.push(i18n.errAc || 'Enter actual cost (ACWP) as zero or greater.');
        if (eacMethod === 4 && !fin(etcNew)) errors.push(i18n.errEtcNew || 'Revised ETC is required when EAC Method 4 is selected.');
        if (errors.length) return { ok: false, errors: errors };

        var phys = clamp(physRaw, 0, 100);
        var startDt = new Date(startStr + 'T00:00:00');
        var assessDt = assessStr ? new Date(assessStr + 'T00:00:00') : new Date();
        if (isNaN(startDt.getTime()) || isNaN(assessDt.getTime())) {
            return { ok: false, errors: [i18n.errInvalidDates || 'Invalid date(s).'] };
        }
        if (assessDt < startDt) {
            return { ok: false, errors: [i18n.errAssessBeforeStart || 'Assessment date cannot be earlier than the start date.'] };
        }

        var elapsedDays = Math.max(0, Math.round((assessDt - startDt) / DAY_MS));
        var at = elapsedDays / DAYS_MO;
        var plannedPct = clamp((at / pd) * 100, 0, 100);
        var pv = Math.min(bac, bac * plannedPct / 100);
        var ev = bac * phys / 100;
        var sv = ev - pv;
        var cv = ev - ac;
        var spi = (fin(ev) && pv > 0) ? ev / pv : NaN;
        var cpi = (fin(ev) && ac > 0) ? ev / ac : NaN;
        var cpiUndef = !fin(cpi);
        var cpiZero = fin(cpi) && cpi <= 0;
        var remWork = Math.max(0, bac - ev);
        var complete = phys >= 99.999;

        var eac1 = NaN, eac2 = NaN, eac3 = NaN, eac4 = NaN;
        if (!cpiZero && !cpiUndef) {
            eac1 = bac / cpi;
        }
        eac2 = ac + (bac - ev);
        if (fin(cpi) && cpi > 0 && fin(spi) && spi > 0) {
            eac3 = ac + (bac - ev) / (cpi * spi);
        }
        if (fin(etcNew)) {
            eac4 = ac + etcNew;
        }
        if (complete) {
            eac1 = ac;
            eac2 = ac;
            if (fin(eac3)) eac3 = ac;
            if (fin(eac4)) eac4 = ac;
        }

        var eacMap = { 1: eac1, 2: eac2, 3: eac3, 4: eac4 };
        var eacMethodEffective = eacMethod;
        if (!fin(eacMap[eacMethod])) {
            var fallback = fin(eac1) ? 1 : 2;
            if (fin(eacMap[fallback])) eacMethodEffective = fallback;
        }
        var eac = eacMap[eacMethodEffective];
        var etc = (fin(eac) && fin(ac)) ? eac - ac : NaN;
        var vac = (fin(bac) && fin(eac)) ? bac - eac : NaN;

        var remBudget = bac - ac;
        var tcpiBac = NaN;
        if (remWork === 0) tcpiBac = 0;
        else if (fin(remBudget) && remBudget > 0) tcpiBac = remWork / remBudget;
        else if (fin(remBudget)) tcpiBac = Infinity;

        var remForecast = (fin(eac) && fin(ac)) ? eac - ac : NaN;
        var tcpiEac = NaN;
        if (remWork === 0) tcpiEac = 0;
        else if (fin(remForecast) && remForecast > 0) tcpiEac = remWork / remForecast;
        else if (fin(remForecast)) tcpiEac = Infinity;

        return {
            ok: true,
            pv: pv,
            ev: ev,
            ac: ac,
            spi: spi,
            cpi: cpi,
            cv: cv,
            sv: sv,
            eac: eac,
            etc: etc,
            vac: vac,
            tcpiBac: tcpiBac,
            tcpiEac: tcpiEac,
            eacMethodEffective: eacMethodEffective
        };
    }

    /** Format for form number inputs; Infinity / NaN → empty string. */
    function formatNum(n, decimals) {
        if (n === Infinity || n === -Infinity || !fin(n)) return '';
        return Number(n).toFixed(decimals);
    }

    return { compute: compute, formatNum: formatNum, DAYS_MO: DAYS_MO };
})();
</script>