/**
 * Phase 17: custom stepper popover for half-step number inputs.
 *
 * Activates on any `input[data-stepper]` — opens a small popover next to
 * the input with −/+ buttons that step by the input's own step attribute
 * (default 1), and — when both min and max are finite — a range slider
 * for quick gross moves. Mutations mirror into input.value and dispatch
 * a bubbling `input` event (so sprint-planner.js live-recomputes); on
 * popover close we dispatch `change` (so the existing debounced save
 * pipeline fires). Strict-CSP-clean: loaded as a standard <script src>.
 *
 * No globals. Single IIFE. Vanilla JS, no jQuery dependency.
 */
(function () {
    'use strict';

    const EPS = 1e-9;

    /**
     * Step a value by delta, clamp to [min, max] when finite, and quantise
     * to the nearest `step` increment. Pure — exposed as a local symbol
     * for readability; would be the testable surface if we added a
     * headless-JS test harness.
     */
    function clampToStep(current, delta, step, min, max) {
        if (!(step > 0)) { step = 1; }
        let next = Number(current) + delta;
        if (Number.isFinite(min) && next < min) { next = min; }
        if (Number.isFinite(max) && next > max) { next = max; }
        // Floor with an epsilon tolerance so 0.6/0.05 doesn't quantise down
        // to the wrong side of the grid thanks to binary-float artefacts.
        const quantised = Math.round((next / step) + EPS * Math.sign(next || 1)) * step;
        // Round to a sensible number of decimals — 6 is more than enough for
        // any step the app uses (0.5 / 0.05 / 1).
        return Number(quantised.toFixed(6));
    }

    // One popover per document, built lazily on first use.
    let pop = null;
    let elDec = null, elInc = null, elOut = null, elRange = null;
    let boundInput = null;

    function build() {
        if (pop) { return; }
        pop = document.createElement('div');
        pop.className = 'stepper-popover';
        pop.hidden = true;
        pop.setAttribute('role', 'dialog');
        pop.setAttribute('aria-label', 'Set value');
        pop.innerHTML = '<button type="button" data-stepper-dec aria-label="Decrease">\u2212</button>'
            + '<output data-stepper-value>0</output>'
            + '<button type="button" data-stepper-inc aria-label="Increase">+</button>'
            + '<input type="range" data-stepper-range hidden>';
        document.body.appendChild(pop);
        elDec   = pop.querySelector('[data-stepper-dec]');
        elInc   = pop.querySelector('[data-stepper-inc]');
        elOut   = pop.querySelector('[data-stepper-value]');
        elRange = pop.querySelector('[data-stepper-range]');

        elDec.addEventListener('click', function () { step(-1); });
        elInc.addEventListener('click', function () { step(+1); });
        elRange.addEventListener('input', function () {
            if (!boundInput) { return; }
            setValue(Number(elRange.value));
        });
        // Stop pointerdown inside the popover from bubbling to the
        // document-level outside-click handler below.
        pop.addEventListener('pointerdown', function (ev) { ev.stopPropagation(); });
    }

    function readBounds() {
        const step = Number(boundInput.step);
        const min  = Number(boundInput.min);
        const max  = Number(boundInput.max);
        return {
            step: Number.isFinite(step) && step > 0 ? step : 1,
            min:  Number.isFinite(min)  ? min  : NaN,
            max:  Number.isFinite(max)  ? max  : NaN,
        };
    }

    function step(dir) {
        if (!boundInput) { return; }
        const b = readBounds();
        const next = clampToStep(Number(boundInput.value) || 0, dir * b.step, b.step, b.min, b.max);
        setValue(next);
    }

    function setValue(n) {
        if (!boundInput) { return; }
        const b = readBounds();
        const next = clampToStep(n, 0, b.step, b.min, b.max);
        boundInput.value = String(next);
        elOut.textContent = String(next);
        if (!elRange.hidden) { elRange.value = String(next); }
        boundInput.dispatchEvent(new Event('input', { bubbles: true }));
    }

    function position(input) {
        const rect = input.getBoundingClientRect();
        // Measure the popover — temporarily visible-off-screen for layout.
        pop.style.left = '-9999px';
        pop.style.top  = '0px';
        pop.hidden = false;
        const pw = pop.offsetWidth;
        const ph = pop.offsetHeight;
        const vh = window.innerHeight;
        const vw = window.innerWidth;

        // Vertical: below unless the input sits in the lower 25% of the
        // viewport, then above.
        const GAP = 4;
        let top;
        if (rect.bottom > vh * 0.75) {
            top = rect.top - ph - GAP;
        } else {
            top = rect.bottom + GAP;
        }
        // Horizontal: align to the input's left edge, clamped to viewport.
        let left = rect.left;
        const MARGIN = 4;
        if (left + pw > vw - MARGIN) { left = vw - pw - MARGIN; }
        if (left < MARGIN) { left = MARGIN; }
        if (top < MARGIN) { top = MARGIN; }

        pop.style.left = left + 'px';
        pop.style.top  = top  + 'px';
    }

    function open(input) {
        build();
        boundInput = input;
        const b = readBounds();
        const current = clampToStep(Number(input.value) || 0, 0, b.step, b.min, b.max);
        elOut.textContent = String(current);

        if (Number.isFinite(b.min) && Number.isFinite(b.max)) {
            elRange.hidden = false;
            elRange.min  = String(b.min);
            elRange.max  = String(b.max);
            elRange.step = String(b.step);
            elRange.value = String(current);
        } else {
            elRange.hidden = true;
        }
        position(input);
    }

    function close(returnFocus) {
        if (!pop || pop.hidden) { return; }
        pop.hidden = true;
        const prev = boundInput;
        boundInput = null;
        if (prev) {
            prev.dispatchEvent(new Event('change', { bubbles: true }));
            if (returnFocus) { try { prev.focus(); } catch (_) { /* ignore */ } }
        }
    }

    // Open on click/focus of a stepper-tagged input.
    function onOpenTrigger(ev) {
        const t = ev.target;
        if (!(t && t.matches && t.matches('input[data-stepper]'))) { return; }
        if (t.disabled || t.readOnly) { return; }
        open(t);
    }
    document.addEventListener('click', onOpenTrigger);
    document.addEventListener('focusin', onOpenTrigger);

    // Outside-click close — pointerdown, not click, so a scroll gesture
    // starting inside the popover in Safari doesn't dismiss prematurely.
    document.addEventListener('pointerdown', function (ev) {
        if (!pop || pop.hidden) { return; }
        const t = ev.target;
        if (boundInput && (t === boundInput || (boundInput.contains && boundInput.contains(t)))) { return; }
        if (pop.contains(t)) { return; }
        close(false);
    });

    // Escape closes + returns focus; Tab that leaves the input + popover
    // closes without focus return.
    document.addEventListener('keydown', function (ev) {
        if (!pop || pop.hidden) { return; }
        if (ev.key === 'Escape') {
            ev.preventDefault();
            close(true);
            return;
        }
        if (ev.key === 'Tab') {
            // After the tab completes, check if focus is still on the input
            // or inside the popover. If not, close.
            setTimeout(function () {
                const active = document.activeElement;
                if (active === boundInput) { return; }
                if (pop.contains(active)) { return; }
                close(false);
            }, 0);
        }
    });

    // While the bound input is focused, ArrowUp/Down step by `step` —
    // restores the shortcut the native spinner lost to Phase 17's CSS reset.
    document.addEventListener('keydown', function (ev) {
        const t = ev.target;
        if (!(t && t.matches && t.matches('input[data-stepper]'))) { return; }
        if (ev.key !== 'ArrowUp' && ev.key !== 'ArrowDown') { return; }
        ev.preventDefault();
        if (boundInput !== t) { open(t); }
        step(ev.key === 'ArrowUp' ? +1 : -1);
    });
})();