// Checks of the globe's pure functions against almanac values, dev only (Node's own test runner, nothing installed):
//   node --test tools/globe/check.mjs
// sun.js is the Astronomical Almanac's low-precision formulas, good to about 0.01° between 1950 and 2050.
import { test } from "node:test"
import assert from "node:assert/strict"
import { analemma, seasonsOf, sunAt, sunAtPlace } from "../../wwwroot/js/sun.js"

const near = (actual, expected, tolerance, what) =>
	assert.ok(Math.abs(actual - expected) <= tolerance, `${what}: ${actual} is not within ${tolerance} of ${expected}`)

test("the June solstice of 2026 puts the Sun over the Tropic of Cancer", () => {
	near(sunAt(new Date("2026-06-21T08:24:00Z")).lat, 23.435, 0.01, "declination")
})

test("the March equinox of 2026 puts the Sun over the equator", () => {
	near(sunAt(new Date("2026-03-20T14:46:00Z")).lat, 0, 0.02, "declination")
})

test("perihelion on 2026-01-03 is the year's nearest Sun", () => {
	near(sunAt(new Date("2026-01-03T17:15:00Z")).distance, 0.98329, 0.0002, "distance in AU")
})

test("Turin's longest day is about 15 h 38 min", () => {
	near(sunAtPlace(sunAt(new Date("2026-06-21T12:00:00Z")), 45.07, 7.69).dayLength, 15.63, 0.05, "day length in hours")
})

test("early October is autumn in the north, and the December solstice comes next", () => {
	const seasons = seasonsOf(sunAt(new Date("2026-10-06T12:00:00Z")))
	assert.equal(seasons.north, "autumn")
	assert.equal(seasons.south, "spring")
	assert.equal(seasons.nextEvent, "december-solstice")
})

test("the analemma spans the tropics and the equation of time", () => {
	const start = new Date("2026-10-06T12:00:00Z")
	const points = analemma(start)
	assert.equal(points.length, 366)
	assert.equal(points[0].lat, sunAt(start).lat)
	near(Math.max(...points.map(p => p.lat)), 23.44, 0.05, "northernmost")
	near(Math.min(...points.map(p => p.lat)), -23.44, 0.05, "southernmost")
	// at 12:00 UTC the Sun is overhead near the prime meridian, early or late by the equation of time (about ±16 min, ±4°)
	const longitudes = points.map(p => p.lng)
	near(Math.max(...longitudes), 3.7, 0.4, "easternmost")
	near(Math.min(...longitudes), -4.1, 0.4, "westernmost")
})