/*
	Neonatal jaundice treatment threshold calculator
	Copyright (C) 2024  Lee Yingtong Li
	
	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.
	
	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

// ----------------------
// Threshold calculations

function phototherapy_38wks(d) {
	if (d <= 0) {
		return 100;
	}
	if (d <= 1) {
		return d * 100 + 100;
	}
	if (d <= 4) {
		return (d - 1) * 150 / 3 + 200;
	}
	return 350;
}

function exchange_38wks(d) {
	if (d <= 0) {
		return 100;
	}
	if (d <= 1.75) {
		return d * 350 / 1.75 + 100;
	}
	return 450;
}

function phototherapy_thresh(d, gestation) {
	if (gestation >= 38) {
		return phototherapy_38wks(d);
	}
	if (gestation < 23) {
		throw new Error('Invalid gestation');
	}
	if (d <= 0) {
		return 40;
	}
	let thresh_at_3days = gestation * 10 - 100;
	if (d <= 3) {
		return d * (thresh_at_3days - 40) / 3 + 40;
	}
	return thresh_at_3days;
}

function exchange_thresh(d, gestation) {
	if (gestation >= 38) {
		return exchange_38wks(d);
	}
	if (gestation < 23) {
		throw new Error('Invalid gestation');
	}
	if (d <= 0) {
		return 80;
	}
	let thresh_at_3days = gestation * 10;
	if (d <= 3) {
		return d * (thresh_at_3days - 80) / 3 + 80;
	}
	return thresh_at_3days;
}

// ----------------------------------
// Bilirubin vs threshold calculation

function describeBilirubin(gestation, dateBirth, dateMeasurement, bilirubin) {
	// Chronological age in days
	let d = (dateMeasurement.getTime() - dateBirth.getTime()) / 1000 / 60 / 60 / 24;
	
	let phototherapy_thresh_value = phototherapy_thresh(d, gestation);
	let exchange_thresh_value = exchange_thresh(d, gestation);
	
	// Restate colours separately so Tailwind can detect them
	let result_text, text_colour, background_colour, accent_colour;
	
	if (bilirubin < phototherapy_thresh_value) {
		if (bilirubin < phototherapy_thresh_value - 50) {
			text_colour = 'text-sky-800';
			background_colour = 'bg-sky-50';
			accent_colour = 'border-sky-400';
		} else {
			text_colour = 'text-yellow-800';
			background_colour = 'bg-yellow-50';
			accent_colour = 'border-yellow-400';
		}
		
		result_text = 'Bilirubin of ' + bilirubin + ' at ' + prettyPrintDays(d) + ' is <span class="font-bold">' + prettyPrintBilirubin(phototherapy_thresh_value - bilirubin) + ' below</span> the phototherapy threshold.';
	} else if (bilirubin < exchange_thresh_value) {
		text_colour = 'text-orange-800';
		background_colour = 'bg-orange-50';
		accent_colour = 'border-orange-400';
		
		result_text = 'Bilirubin of ' + bilirubin + ' at ' + prettyPrintDays(d) + ' is <span class="font-bold">' + prettyPrintBilirubin(bilirubin - phototherapy_thresh_value) + ' above</span> the phototherapy threshold, ' + prettyPrintBilirubin(exchange_thresh_value - bilirubin) + ' below the exchange transfusion threshold.';
	} else {
		text_colour = 'text-red-800';
		background_colour = 'bg-red-50';
		accent_colour = 'border-red-400';
		
		result_text = 'Bilirubin of ' + bilirubin + ' at ' + prettyPrintDays(d) + ' is ' + prettyPrintBilirubin(bilirubin - exchange_thresh_value) + ' above the <span class="font-bold">exchange transfusion</span> threshold.';
	}
	
	return [d, result_text, text_colour, background_colour, accent_colour];
}

// --------------
// Utility functions

function prettyPrintHours(d) {
	if (d >= 23.5/24) {
		throw new Error('>24 hours passed to prettyPrintHours');
	}
	
	if (d < 0.5/24) {
		return '0 hours';
	}
	if (d < 1.5/24) {
		return '1 hour';
	}
	return (d * 24).toFixed(0) + ' hours';
}

function prettyPrintDays(d) {
	if (d < 23.5/24) {
		return prettyPrintHours(d);
	}
	if (d < 1 + 23.5/24) {
		return '1 day, ' + prettyPrintHours(d % 1);
	}
	
	let d_rounded = Math.round(d * 24) / 24; // Round 23.5 hours+ to the next day
	
	return Math.floor(d_rounded) + ' days, ' + prettyPrintHours(d_rounded % 1);
}

function prettyPrintBilirubin(b) {
	if (b < 10) {
		return b.toFixed(1);
	} else {
		return Math.round(b).toFixed(0);
	}
}

function dateToISOStringLocal(date) {
	function pad(n) {
		if (n < 10) {
			return '0' + n;
		}
		return '' + n;
	}
	
	return date.getFullYear() + '-' + pad(date.getMonth() + 1) + '-' + pad(date.getDate()) + 'T' + pad(date.getHours()) + ':' + pad(date.getMinutes());
}