lukegb · May 15, 2021 18:05
diff --git a/howmuch.html b/howmuch.html
 <!DOCTYPE html>
 <meta charset="utf-8">
 <style>
    .total-money {
        font-weight: bold;
    }
    .container td {
        padding: 0.2rem 0.5rem;
    }
    .slider {
        width: 10rem;
    }
    .slider-text {
        width: 3rem;
    }
    .diff-expl {
        text-align: right;
    }
 </style>
 <title>How much do I need to Contribute To The Economy</title>
 <h1>How much do I need to Contribute To The Economy</h1>
 <table class="container"></table>
 <p>Based on some recent <a href="https://www.standard.co.uk/news/uk/brits-drink-124-pints-each-struggling-pubs-covid-lockdown-b935186.html">news</a> and this <a href="https://www.companydebt.com/features/124-pints-to-save-the-pub/">source</a>.</p>
 <template id="slider-template">
    <tr class="slider-holder">
        <td><input type="range" class="slider"></td>
        <td><input type="number" class="slider-text"></td>
        <td><span class="slider-value"></span></td>
        <td>@ <span class="slider-each"></span>/ea</td>
        <td><span class="slider-money"></span></td>
    </tr>
 </template>
 <template id="total-template">
    <tr style="display:none"><!-- this is really just for debugging -->
        <td colspan="3"></td>
        <td class="diff-expl">Difference:</td>
        <td><span class="diff-money"></span></td>
    </tr>
    <tr>
        <td colspan="4"></td>
        <td><span class="total-money"></span></td>
    </tr>
 </template>
 <script type="module">
 const sum = (it, f) => it.reduce((acc, v) => acc + f(v), 0);
 const i = (v) => parseInt(v, 10);

 const MONEY_FORMAT = new Intl.NumberFormat('en-GB', { style: 'currency', currency: 'GBP' });
 const container = document.querySelector('.container');
 const tmpl = document.querySelector('#slider-template');

 const PUB_THINGS = [
    {
        name: "Pints of Beer",
        singularName: "Pint of Beer",
        defaultValue: 124,
        each: 394,
    },
    {
        name: "Glasses of Wine",
        singularName: "Glass of Wine",
        defaultValue: 0,
        each: 400,
    },
    {
        name: "Roast Dinners",
        singularName: "Roast Dinner",
        defaultValue: 0,
        each: 1220,
    },
    {
        name: "Packs of Crisps",
        singularName: "Pack of Crisps",
        defaultValue: 0,
        each: 50,
    }
 ];
 const TOTAL = sum(PUB_THINGS, (v) => v.defaultValue*v.each);

 const ELEMENTS = PUB_THINGS.map((v) => {
    const content = tmpl.content.cloneNode(true);
    const slider = content.querySelector('.slider');
    const text = content.querySelector('.slider-text');
    text.min = slider.min = 0;
    text.max = slider.max = Math.ceil(TOTAL / v.each);
    text.value = slider.value = v.defaultValue;
    const textValue = content.querySelector('.slider-value');
    const money = content.querySelector('.slider-money');
    content.querySelector('.slider-each').textContent = MONEY_FORMAT.format(v.each / 100);
    container.appendChild(content);

    slider.addEventListener('change', () => {
        text.value = slider.value;
        updateElements(v.name);
    });
    text.addEventListener('change', () => {
        slider.value = text.value;
        updateElements(v.name);
    });

    return {
        slider,
        text,
        textValue,
        money,
        ...v,
    }
 });
 const {totalEl, diffEl} = (() => {
    const content = document.querySelector('#total-template').content.cloneNode(true);
    const totalEl = content.querySelector('.total-money');
    const diffEl = content.querySelector('.diff-money');
    container.appendChild(content);
    return {totalEl, diffEl};
 })();
 const updateElements = (changedName) => {
    let total = 0;
    ELEMENTS.forEach((v) => {
        v.textValue.textContent = v.slider.value == 1 ? v.singularName : v.name;
        v.money.textContent = MONEY_FORMAT.format(v.each * i(v.slider.value) / 100);
        total += v.each * i(v.slider.value);
    });
    totalEl.textContent = MONEY_FORMAT.format(total / 100);
    diffEl.textContent = MONEY_FORMAT.format((TOTAL - total) / 100);

    if (changedName === null) return;

    // If we know which slider was changed, try to bring all other non-zero sliders up to sync.
    // If all other sliders are zero, then only increase the last one as a fallback.
    // This is to ensure that we don't increase things that people have set to zero on purpose (e.g. because they don't like roast dinners or wine).
    let epsilon = null;
    let canBeAdjusted = [];
    for (const e of ELEMENTS) {
        if (e.name === changedName) continue;
        if (e.slider.value == 0) continue;
        canBeAdjusted.push(e);
        if (epsilon === null || epsilon.each > e.each) {
            epsilon = e;
        }
    }
    if (epsilon === null) {
        if (changedName === 'Packs of Crisps') {
            // If everything is 0 other than packs of crisps, use beer.
            epsilon = ELEMENTS[0];
            canBeAdjusted.push(ELEMENTS[0]);
        } else {
            // Always just adjust packs of crisps.
            epsilon = ELEMENTS[ELEMENTS.length-1];
            canBeAdjusted.push(ELEMENTS[ELEMENTS.length-1]);
        }
    }
    let totalOfAll = sum(canBeAdjusted, (v) => v.each);
    let maxCanBeRemoved = canBeAdjusted.reduce((t, v) => Math.min(t, v.slider.value), TOTAL);
    
    let difference = TOTAL - sum(ELEMENTS, (v) => v.slider.value*v.each);
    console.log(`we're ${difference/100} short!`, epsilon.each);
    // If we're *less* than TOTAL, we always adjust.
    if (Math.abs(difference) < (epsilon.each/2) && difference < 0) return; // Nothing to do.

    if (Math.abs(difference) >= (totalOfAll/2)) {
        const amountToAddToAll = Math.max(-maxCanBeRemoved, Math.floor(difference / totalOfAll));
        canBeAdjusted.forEach((v) => {
            v.slider.value = v.text.value = i(v.slider.value) + amountToAddToAll;
        });
        difference -= Math.floor(difference / totalOfAll);
    }

    difference = TOTAL - sum(ELEMENTS, (v) => v.slider.value*v.each)
    console.log(`Remaining difference: ${difference}; epsilon is ${epsilon.each}`);
    
    // Mess with epsilon to make up the difference.
    if (Math.abs(difference) >= (epsilon.each/2) || difference > 0) {
        difference += epsilon.each * i(epsilon.slider.value);
        epsilon.slider.value = epsilon.text.value = Math.max(0, Math.ceil(difference / epsilon.each));
    }

    updateElements(null);
 };
 updateElements(null);
 </script>
	<!DOCTYPE html>
	<meta charset="utf-8">
	<style>
	.total-money {
	font-weight: bold;
	}
	.container td {
	padding: 0.2rem 0.5rem;
	}
	.slider {
	width: 10rem;
	}
	.slider-text {
	width: 3rem;
	}
	.diff-expl {
	text-align: right;
	}
	</style>
	<title>How much do I need to Contribute To The Economy</title>
	<h1>How much do I need to Contribute To The Economy</h1>
	<table class="container"></table>
	<p>Based on some recent <a href="https://www.standard.co.uk/news/uk/brits-drink-124-pints-each-struggling-pubs-covid-lockdown-b935186.html">news</a> and this <a href="https://www.companydebt.com/features/124-pints-to-save-the-pub/">source</a>.</p>
	<template id="slider-template">
	<tr class="slider-holder">
	<td><input type="range" class="slider"></td>
	<td><input type="number" class="slider-text"></td>
	<td><span class="slider-value"></span></td>
	<td>@ <span class="slider-each"></span>/ea</td>
	<td><span class="slider-money"></span></td>
	</tr>
	</template>
	<template id="total-template">
	<tr style="display:none"><!-- this is really just for debugging -->
	<td colspan="3"></td>
	<td class="diff-expl">Difference:</td>
	<td><span class="diff-money"></span></td>
	</tr>
	<tr>
	<td colspan="4"></td>
	<td><span class="total-money"></span></td>
	</tr>
	</template>
	<script type="module">
	const sum = (it, f) => it.reduce((acc, v) => acc + f(v), 0);
	const i = (v) => parseInt(v, 10);

	const MONEY_FORMAT = new Intl.NumberFormat('en-GB', { style: 'currency', currency: 'GBP' });
	const container = document.querySelector('.container');
	const tmpl = document.querySelector('#slider-template');

	const PUB_THINGS = [
	{
	name: "Pints of Beer",
	singularName: "Pint of Beer",
	defaultValue: 124,
	each: 394,
	},
	{
	name: "Glasses of Wine",
	singularName: "Glass of Wine",
	defaultValue: 0,
	each: 400,
	},
	{
	name: "Roast Dinners",
	singularName: "Roast Dinner",
	defaultValue: 0,
	each: 1220,
	},
	{
	name: "Packs of Crisps",
	singularName: "Pack of Crisps",
	defaultValue: 0,
	each: 50,
	}
	];
	const TOTAL = sum(PUB_THINGS, (v) => v.defaultValue*v.each);

	const ELEMENTS = PUB_THINGS.map((v) => {
	const content = tmpl.content.cloneNode(true);
	const slider = content.querySelector('.slider');
	const text = content.querySelector('.slider-text');
	text.min = slider.min = 0;
	text.max = slider.max = Math.ceil(TOTAL / v.each);
	text.value = slider.value = v.defaultValue;
	const textValue = content.querySelector('.slider-value');
	const money = content.querySelector('.slider-money');
	content.querySelector('.slider-each').textContent = MONEY_FORMAT.format(v.each / 100);
	container.appendChild(content);

	slider.addEventListener('change', () => {
	text.value = slider.value;
	updateElements(v.name);
	});
	text.addEventListener('change', () => {
	slider.value = text.value;
	updateElements(v.name);
	});

	return {
	slider,
	text,
	textValue,
	money,
	...v,
	}
	});
	const {totalEl, diffEl} = (() => {
	const content = document.querySelector('#total-template').content.cloneNode(true);
	const totalEl = content.querySelector('.total-money');
	const diffEl = content.querySelector('.diff-money');
	container.appendChild(content);
	return {totalEl, diffEl};
	})();
	const updateElements = (changedName) => {
	let total = 0;
	ELEMENTS.forEach((v) => {
	v.textValue.textContent = v.slider.value == 1 ? v.singularName : v.name;
	v.money.textContent = MONEY_FORMAT.format(v.each * i(v.slider.value) / 100);
	total += v.each * i(v.slider.value);
	});
	totalEl.textContent = MONEY_FORMAT.format(total / 100);
	diffEl.textContent = MONEY_FORMAT.format((TOTAL - total) / 100);

	if (changedName === null) return;

	// If we know which slider was changed, try to bring all other non-zero sliders up to sync.
	// If all other sliders are zero, then only increase the last one as a fallback.
	// This is to ensure that we don't increase things that people have set to zero on purpose (e.g. because they don't like roast dinners or wine).
	let epsilon = null;
	let canBeAdjusted = [];
	for (const e of ELEMENTS) {
	if (e.name === changedName) continue;
	if (e.slider.value == 0) continue;
	canBeAdjusted.push(e);
	if (epsilon === null \|\| epsilon.each > e.each) {
	epsilon = e;
	}
	}
	if (epsilon === null) {
	if (changedName === 'Packs of Crisps') {
	// If everything is 0 other than packs of crisps, use beer.
	epsilon = ELEMENTS[0];
	canBeAdjusted.push(ELEMENTS[0]);
	} else {
	// Always just adjust packs of crisps.
	epsilon = ELEMENTS[ELEMENTS.length-1];
	canBeAdjusted.push(ELEMENTS[ELEMENTS.length-1]);
	}
	}
	let totalOfAll = sum(canBeAdjusted, (v) => v.each);
	let maxCanBeRemoved = canBeAdjusted.reduce((t, v) => Math.min(t, v.slider.value), TOTAL);

	let difference = TOTAL - sum(ELEMENTS, (v) => v.slider.value*v.each);
	console.log(`we're ${difference/100} short!`, epsilon.each);
	// If we're less than TOTAL, we always adjust.
	if (Math.abs(difference) < (epsilon.each/2) && difference < 0) return; // Nothing to do.

	if (Math.abs(difference) >= (totalOfAll/2)) {
	const amountToAddToAll = Math.max(-maxCanBeRemoved, Math.floor(difference / totalOfAll));
	canBeAdjusted.forEach((v) => {
	v.slider.value = v.text.value = i(v.slider.value) + amountToAddToAll;
	});
	difference -= Math.floor(difference / totalOfAll);
	}

	difference = TOTAL - sum(ELEMENTS, (v) => v.slider.value*v.each)
	console.log(`Remaining difference: ${difference}; epsilon is ${epsilon.each}`);

	// Mess with epsilon to make up the difference.
	if (Math.abs(difference) >= (epsilon.each/2) \|\| difference > 0) {
	difference += epsilon.each * i(epsilon.slider.value);
	epsilon.slider.value = epsilon.text.value = Math.max(0, Math.ceil(difference / epsilon.each));
	}

	updateElements(null);
	};
	updateElements(null);
	</script>