177 lines
7.6 KiB
JavaScript
177 lines
7.6 KiB
JavaScript
// Units — the shared toggle and unit-aware formatting for every measure we show.
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// The API always speaks imperial (°F, inches, mph); the unit is a pure display
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// concern. Pages format through fmtTemp/fmtPrecip/fmtWind and re-render on
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// `onUnitChange`, so stored and plotted values stay imperial and only the numbers
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// shown flip.
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//
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// One flag drives all of them: picking °C also gives mm and km/h. A reader who
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// wants Celsius wants the rest metric too, and a per-measure control would be
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// three toggles in a header that has room for one. The button still shows °F/°C
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// because temperature is what people look for.
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//
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// Absolute humidity (g/m³) is metric in both systems — there is no imperial unit
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// for it anyone would recognise — so it is formatted here but never converted.
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const UNIT_KEY = "thermograph:unit";
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// First-time default: pick °F only for the countries that actually use it (the US
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// plus a handful of territories/nations), otherwise °C — read off the browser
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// locale's region subtag (en-US → F, de-DE → C). A stored choice always wins, so
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// this only affects visitors who've never toggled. Not persisted, so an unstored
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// visitor keeps re-deriving the same locale default until they pick one.
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const F_REGIONS = new Set(["US", "PR", "GU", "VI", "AS", "MP", "UM", "BS", "BZ", "KY", "PW", "FM", "MH", "LR"]);
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function defaultUnit() {
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const langs = (navigator.languages && navigator.languages.length)
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? navigator.languages : [navigator.language];
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for (const l of langs) {
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const m = /-([A-Za-z]{2})\b/.exec(l || "");
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if (m) return F_REGIONS.has(m[1].toUpperCase()) ? "F" : "C";
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}
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return "F"; // no region subtag to go on → keep the historical default
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}
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// A climate page knows which city it is about, so it publishes that country's
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// convention on <body data-unit-default>. It sits *between* the stored choice and
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// the locale guess: better than the locale (a UK visitor reading about Phoenix
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// wants the °F the page already rendered, and repainting it to °C would just be a
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// flash), but never better than an explicit toggle. Pages with no single city —
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// the homepage, the interactive views — emit no attribute and fall through.
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function pageDefault() {
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const v = document.body && document.body.dataset.unitDefault;
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return (v === "C" || v === "F") ? v : null;
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}
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const _stored = localStorage.getItem(UNIT_KEY);
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let _unit = (_stored === "C" || _stored === "F")
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? _stored
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: (pageDefault() || defaultUnit());
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const _unitCbs = [];
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export function getUnit() { return _unit; }
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// A Fahrenheit value as a number in the active unit.
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export function toUnit(vF) { return _unit === "C" ? (vF - 32) * 5 / 9 : vF; }
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// A Fahrenheit value formatted as a rounded temperature in the active unit.
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// `withLetter` appends the C/F letter (off by default — the nav toggle shows it).
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export function fmtTemp(vF, withLetter) {
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if (vF == null || isNaN(vF)) return "—";
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return `${Math.round(toUnit(vF))}°${withLetter ? _unit : ""}`;
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}
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// A Fahrenheit-degree *difference* (a span or tolerance, not an absolute
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// reading) formatted in the active unit. Differences scale by 5/9 with no 32°
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// offset, so they can't go through toUnit/fmtTemp.
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export function fmtDelta(dF, withLetter) {
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if (dF == null || isNaN(dF)) return "—";
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const d = _unit === "C" ? dF * 5 / 9 : dF;
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return `${Math.round(d)}°${withLetter ? _unit : ""}`;
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}
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// --- precipitation (stored in inches) ----------------------------------------
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const MM_PER_IN = 25.4;
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// Inches as a number in the active unit.
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export function toPrecip(vIn) { return _unit === "C" ? vIn * MM_PER_IN : vIn; }
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// Millimetres are whole numbers — that is how rainfall is reported, and a tenth
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// of a millimetre is below what the source resolves. Inches keep two decimals,
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// since a whole inch of rain is a lot to round to.
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// The suffix is " in"/" mm" to match what content.py renders server-side, so a
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// climate page's repaint reproduces the text it shipped with rather than swapping
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// the glyph. Compact surfaces (the tier bar) pass withUnit=false and add their own.
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export function fmtPrecip(vIn, withUnit = true) {
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if (vIn == null || isNaN(vIn)) return "—";
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return _unit === "C"
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? `${Math.round(vIn * MM_PER_IN)}${withUnit ? " mm" : ""}`
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: `${vIn.toFixed(2)}${withUnit ? " in" : ""}`;
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}
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export const precipUnit = () => (_unit === "C" ? "mm" : "in");
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// --- wind (stored in mph) ----------------------------------------------------
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const KMH_PER_MPH = 1.609344;
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export function toWind(vMph) { return _unit === "C" ? vMph * KMH_PER_MPH : vMph; }
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export function fmtWind(vMph, withUnit = true) {
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if (vMph == null || isNaN(vMph)) return "—";
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const v = Math.round(toWind(vMph));
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return `${v}${withUnit ? (_unit === "C" ? " km/h" : " mph") : ""}`;
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}
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export const windUnit = () => (_unit === "C" ? "km/h" : "mph");
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// --- absolute humidity (g/m³ in both systems) --------------------------------
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export function fmtHumid(v, withUnit = true) {
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if (v == null || isNaN(v)) return "—";
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return `${v.toFixed(1)}${withUnit ? " g/m³" : ""}`;
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}
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export const humidUnit = () => "g/m³";
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export function onUnitChange(cb) { _unitCbs.push(cb); }
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// --- unit symbols in prose ---------------------------------------------------
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// Static copy that names a unit ("wind speed (mph)") marks it up as
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// <span data-unit-label="wind">mph</span>. The HTML ships the imperial symbol so
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// there's something sensible with no JS; this keeps it honest once a unit is
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// known. Runs on load and on every toggle, wherever units.js is imported.
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const UNIT_LABEL = {
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temp: () => `°${_unit}`,
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precip: () => (_unit === "C" ? "mm" : "inches"),
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wind: () => windUnit(),
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humid: () => "g/m³",
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};
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function paintUnitLabels() {
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for (const el of document.querySelectorAll("[data-unit-label]")) {
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const f = UNIT_LABEL[el.dataset.unitLabel];
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if (f) el.textContent = f();
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}
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}
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export function setUnit(u) {
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const nu = (u === "C") ? "C" : "F";
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if (nu === _unit) return;
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_unit = nu;
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try { localStorage.setItem(UNIT_KEY, _unit); } catch (e) {}
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document.querySelectorAll(".unit-toggle").forEach(syncUnitToggle);
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paintUnitLabels();
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_unitCbs.forEach((cb) => { try { cb(_unit); } catch (e) {} });
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}
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function syncUnitToggle(wrap) {
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wrap.querySelectorAll("button[data-unit]").forEach((b) => {
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const on = b.dataset.unit === _unit;
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b.classList.toggle("active", on);
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b.setAttribute("aria-pressed", on ? "true" : "false");
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});
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}
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// Drop a segmented °F/°C control into the header's top-right, ahead of the view
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// switcher. A page opts out with data-no-unit-toggle on <body>.
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(function buildUnitToggle() {
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const brand = document.querySelector(".brand");
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if (!brand || brand.querySelector(".unit-toggle")) return;
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if (document.body.dataset.noUnitToggle != null) return;
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const wrap = document.createElement("div");
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wrap.className = "unit-toggle";
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wrap.setAttribute("role", "group");
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// Labelled for what it actually switches now — temperature, precipitation and
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// wind — even though the buttons read °F/°C.
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wrap.setAttribute("aria-label", "Units");
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wrap.innerHTML = '<button type="button" data-unit="F">°F</button>'
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+ '<button type="button" data-unit="C">°C</button>';
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wrap.addEventListener("click", (e) => {
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const b = e.target.closest("button[data-unit]");
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if (b) setUnit(b.dataset.unit);
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});
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// Lives inside the nav menu panel: display:contents keeps it inline top-right
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// on desktop; on phones it stacks inside the hamburger dropdown. Fall back to a
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// brand sibling if the panel isn't present.
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const panel = brand.querySelector(".nav-panel");
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if (panel) panel.appendChild(wrap);
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else brand.insertBefore(wrap, brand.querySelector(".view-nav"));
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syncUnitToggle(wrap);
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})();
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paintUnitLabels();
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