import {queryHourly, getCoords, queryCurrent} from './influx.mjs';
import {getCelestialCurrent} from './celestial.mjs';
import {getWeatherCondition} from './openweather.mjs';
import {localDateStr} from './config.mjs';

export let lastForecast = { ts: 0, slots: [], summary: null }
export const forecastTTL = 5 * 60 * 60_000

function linearTrend(values) {
	const n = values.length;
	if (n < 2) return 0;
	const xMean = (n - 1) / 2;
	const yMean = values.reduce((a, b) => a + b, 0) / n;
	const num = values.reduce((s, v, i) => s + (i - xMean) * (v - yMean), 0);
	const den = values.reduce((s, _, i) => s + (i - xMean) ** 2, 0);
	return den === 0 ? 0 : num / den;
}

function dewPoint(tempC, humidity) {
	const a = 17.27, b = 237.7;
	const gamma = (a * tempC) / (b + tempC) + Math.log(humidity / 100);
	return (b * gamma) / (a - gamma);
}

function heatIndex(tempC, humidity) {
	const T = tempC * 9 / 5 + 32;
	if (T < 80) return tempC;
	const HI =
		-42.379 + 2.04901523 * T + 10.14333127 * humidity
		- 0.22475541 * T * humidity - 0.00683783 * T * T
		- 0.05481717 * humidity * humidity + 0.00122874 * T * T * humidity
		+ 0.00085282 * T * humidity * humidity - 0.00000199 * T * T * humidity * humidity;
	return (HI - 32) * 5 / 9;
}

function vaporPressureDeficit(tempC, humidity) {
	const svp = 0.6108 * Math.exp((17.27 * tempC) / (tempC + 237.3));
	return Math.round(svp * (1 - humidity / 100) * 1000) / 1000;
}

function absoluteHumidity(tempC, humidity) {
	const svp = 0.6108 * Math.exp((17.27 * tempC) / (tempC + 237.3));
	return Math.round((humidity / 100 * svp * 2165) / (tempC + 273.15) * 1000) / 1000;
}

function pressureRule(trend3h, currentHpa) {
	if (trend3h < -2.0) return { label: 'Storm likely',     code: 211, precipChance: 0.85 };
	if (trend3h < -0.8) return { label: 'Rain likely',      code: 501, precipChance: 0.65 };
	if (trend3h < -0.3) return { label: 'Cloudy',           code: 803, precipChance: 0.35 };
	if (trend3h >  1.5) return { label: 'Clearing',         code: 801, precipChance: 0.05 };
	if (trend3h >  0.3) return { label: 'Improving',        code: 800, precipChance: 0.10 };
	if (currentHpa < 1000) return { label: 'Unsettled',     code: 802, precipChance: 0.30 };
	if (currentHpa < 1013) return { label: 'Partly cloudy', code: 802, precipChance: 0.15 };
	return { label: 'Fair', code: 800, precipChance: 0.05 };
}

function solarTempDelta(sunElevation, cloudFraction) {
	if (sunElevation <= 0) return 0;
	return Math.sin((sunElevation * Math.PI) / 180) * (1 - cloudFraction) * 6;
}

function nocturnalCooling(cloudFraction) {
	return (1 - cloudFraction) * 1.5;
}

function forecastHumidity(absHumidity, forecastTempC) {
	const svp = 0.6108 * Math.exp((17.27 * forecastTempC) / (forecastTempC + 237.3));
	const rh = (absHumidity * (forecastTempC + 273.15)) / (svp * 2165) * 100;
	return Math.min(100, Math.max(0, Math.round(rh * 10) / 10));
}

function estimateClouds(humidity, pressureTrend) {
	let base = humidity / 100 * 0.8;
	if (pressureTrend < -0.3) base = Math.min(1, base + 0.2);
	if (pressureTrend >  0.3) base = Math.max(0, base - 0.15);
	return Math.round(base * 100) / 100;
}

function forecastWind(currentWind, pressureTrend) {
	const boost = pressureTrend < -1 ? 1.3 : pressureTrend < -0.5 ? 1.1 : 1.0;
	return Math.round(currentWind * boost * 10) / 10;
}

export async function get24HourForecast(currentSensors) {
	const now    = new Date();
	const sixAgo = new Date(now - 6 * 3600 * 1000);

	const coords  = await getCoords();
	const history = await queryHourly(sixAgo, now);

	const pressures  = history.map(r => r.pressure_hpa).filter(Number.isFinite);
	const temps      = history.map(r => r.temperature).filter(Number.isFinite);
	const humidities = history.map(r => r.humidity).filter(Number.isFinite);
	const winds      = history.map(r => r.wind_speed).filter(Number.isFinite);

	const pressureTrend = linearTrend(pressures);
	const tempTrend     = linearTrend(temps);
	const humidityTrend = linearTrend(humidities);
	const pressure3h    = pressureTrend * 3;

	const seedTemp     = currentSensors.temperature  ?? temps.at(-1)      ?? 20;
	const seedHumidity = currentSensors.humidity     ?? humidities.at(-1) ?? 60;
	const seedPressure = currentSensors.pressure_hpa ?? pressures.at(-1)  ?? 1013;
	const seedWind     = currentSensors.wind_speed   ?? winds.at(-1)      ?? 0;
	const seedAbsHum   = currentSensors.humidity_abs ?? absoluteHumidity(seedTemp, seedHumidity);

	const weather = pressureRule(pressure3h, seedPressure);

	const slots = Array.from({ length: 24 }, (_, i) => {
		const time = new Date(now.getTime() + (i + 1) * 3600 * 1000);
		time.setMinutes(0, 0, 0);

		const pressureDamping = Math.exp(-i * 0.08);
		const pressure   = seedPressure + pressureTrend * (i + 1) * pressureDamping;
		const clouds     = estimateClouds(seedHumidity + humidityTrend * i, pressureTrend);
		const bgTemp     = seedTemp + tempTrend * (i + 1);
		const temperature = Math.round(bgTemp * 10) / 10;
		const humidity   = forecastHumidity(seedAbsHum, temperature);
		const wind_speed = forecastWind(seedWind, pressureTrend);

		const celestial = getCelestialCurrent(coords.latitude, coords.longitude, time);
		const snapshot = {
			time,
			temperature,
			humidity,
			humidity_abs:           absoluteHumidity(temperature, humidity),
			dew_point:              Math.round(dewPoint(temperature, humidity) * 100) / 100,
			heat_index:             Math.round(heatIndex(temperature, humidity) * 100) / 100,
			vapor_pressure_deficit: vaporPressureDeficit(temperature, humidity),
			pressure_hpa:           Math.round(pressure * 100) / 100,
			wind_speed,
			clouds,
			precipitation_chance:   Math.round(weather.precipChance * (1 - i * 0.02) * 100),
			...celestial
		};

		Object.assign(snapshot, getWeatherCondition(snapshot));
		snapshot.icon = `/icons/${snapshot.icon}.png`;
		return snapshot;
	});

	for (const slot of slots) {
		if (slot.sunrise && slot.sunset) {
			const t    = slot.time instanceof Date    ? slot.time.getTime()    : new Date(slot.time).getTime();
			const rise = slot.sunrise instanceof Date ? slot.sunrise.getTime() : new Date(slot.sunrise).getTime();
			const set  = slot.sunset  instanceof Date ? slot.sunset.getTime()  : new Date(slot.sunset).getTime();
			slot.daytime = t >= rise && t < set;
		} else {
			slot.daytime = (slot.sun_elevation ?? 0) > 0;
		}

		const solar = solarTempDelta(slot.sun_elevation ?? 0, slot.clouds);
		const cool  = slot.daytime ? 0 : nocturnalCooling(slot.clouds);
		slot.temperature            = Math.round((slot.temperature + solar - cool) * 10) / 10;
		slot.humidity               = forecastHumidity(seedAbsHum, slot.temperature);
		slot.dew_point              = Math.round(dewPoint(slot.temperature, slot.humidity) * 100) / 100;
		slot.heat_index             = Math.round(heatIndex(slot.temperature, slot.humidity) * 100) / 100;
		slot.vapor_pressure_deficit = vaporPressureDeficit(slot.temperature, slot.humidity);
		slot.humidity_abs           = absoluteHumidity(slot.temperature, slot.humidity);
	}

	return slots;
}

// Group slots into local-time day buckets, summarise each as daytime-only
function groupByLocalDay(slots) {
	const days = {}
	for (const slot of slots) {
		const key = localDateStr(new Date(slot.time))
		if (!days[key]) days[key] = []
		days[key].push(slot)
	}
	return days
}

function summarise(slots) {
	if (!slots.length) return null

	// Use only daytime slots for representative label/stats, fallback to all if none
	const daytime = slots.filter(s => s.daytime)
	const source  = daytime.length ? daytime : slots

	const temps   = source.map(s => s.temperature).filter(Number.isFinite)
	const precips = source.map(s => s.precipitation_chance).filter(Number.isFinite)
	const winds   = source.map(s => s.wind_speed).filter(Number.isFinite)
	const gusts   = source.map(s => s.wind_gusts).filter(Number.isFinite)
	const uvs     = source.map(s => s.uv_index).filter(Number.isFinite)
	const solar   = source.map(s => s.solar_wm2).filter(Number.isFinite)

	// Min/max temp uses ALL slots for the full day range
	const allTemps = slots.map(s => s.temperature).filter(Number.isFinite)

	const labelCount = {}
	for (const s of source) labelCount[s.label] = (labelCount[s.label] || 0) + 1
	const label    = Object.entries(labelCount).sort((a, b) => b[1] - a[1])[0][0]
	const dominant = source.find(s => s.label === label)

	return {
		time:                 slots[0].time,
		label:                dominant.label,
		code:                 dominant.code,
		icon:                 dominant.icon,
		temperature:          Math.max(...temps),
		temperature_max:      Math.max(...allTemps),
		temperature_min:      Math.min(...allTemps),
		precipitation_chance: Math.round(Math.max(...precips)),
		wind_speed:           Math.round(Math.max(...winds) * 10) / 10,
		wind_gusts:           gusts.length ? Math.round(Math.max(...gusts) * 10) / 10 : null,
		uv_index:             uvs.length   ? Math.max(...uvs)   : null,
		uv_index_label:       dominant.uv_index_label ?? null,
		solar_wm2:            solar.length ? Math.round(solar.reduce((a, b) => a + b, 0) / solar.length * 10) / 10 : null,
		sunrise:              slots.find(s => s.sunrise)?.sunrise ?? null,
		sunset:               slots.find(s => s.sunset)?.sunset   ?? null,
		humidity:             Math.round(source.map(s => s.humidity).filter(Number.isFinite).reduce((a, b) => a + b, 0) / source.length * 10) / 10,
		pressure_hpa:         Math.round(source.map(s => s.pressure_hpa).filter(Number.isFinite).reduce((a, b) => a + b, 0) / source.length * 10) / 10,
	}
}

export async function getForecast() {
	if (Date.now() - lastForecast.ts < forecastTTL) return lastForecast;
	const sensors = await queryCurrent().catch(() => null)
	if (!sensors) return lastForecast
	const slots = await get24HourForecast(sensors).catch(() => null)
	if (!slots) return lastForecast

	// Summarise today's local-day slots only
	const days      = groupByLocalDay(slots)
	const todayKey  = localDateStr(new Date())
	const todaySlots = days[todayKey] ?? slots
	lastForecast = { ts: Date.now(), slots, summary: summarise(todaySlots) }
	return lastForecast
}
