---
title: "Perpetual Inventory"
url: ""
featureImage: "/projects/shipping_container.jpg"
short: "pi"
category: "fullstack"
ai: ""
order: "18"
year: "2021"
tags: ["react", "javascript", "jquery", "flask", "sqlalchemy", "materialize css", "celery", "redis", "postgres"]
---
One of the first projects I did for [HtmMbs][0], JP, the owner, wanted a way to
better manage inventory counts.
The system was built in Flask and SQLAlchemy with a LOT of JavaScript. I
designed a sophisticated admin panel (the bulk of the project) and a count queue
that could be put in multiple modes for various warehouses. The queue would
present a location and SKU for a warehouse worker to count, check how far off
their count was from what the system knew, occasionally ask for them to recount,
and keep track of whether or whether not the counts were consistent.
Because the company uses Odoo for everything, I had to write a lot of logic in
celery to keep everything synced. Adding a module to Odoo wasn't preferrable
because (a) this was a very heavy duty application, around 10kloc, and (b) every
new module in Odoo just makes the next migration that much harder. Better to use
separate services.
Among the features I added:
- An emergency queue and quasi-messaging system for communication between
managers and admins to see if locations were being properly allocated and
counters were consistent.
- A location allocation system.
- A picking allocation system in React that had a responsive map for allocating
special picking locations.
- EOD reports for admins containing detailed statistics about the day's
business.
[0]: https://mbs-standoffs.com
<sky-template path="main.html" />
<sky-block name="title">${frontmatter.title} · </sky-block>
<sky-block name="content">
<article class="project">
<a class="back" href="/projects">← all projects</a>
<p class="pills"><span class="pill">${frontmatter.category}</span><span class="pill pill-ai">${frontmatter.ai}</span><span class="year">${frontmatter.year}</span></p>
<h1>${frontmatter.title}</h1>
<a class="visit" href="${frontmatter.url}">${frontmatter.url}</a>
<img class="feature" src="${frontmatter.featureImage}" alt="" />
<div class="markdown">
<sky-slot name="content" />
</div>
</article>
</sky-block>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<script><sky-include path="theme.js" /></script>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title><sky-slot name="title" />${meta.title}</title>
<meta name="description" content="${meta.description}" />
<meta name="theme-color" content="#142420" />
<link rel="icon" href="/favicon.svg" type="image/svg+xml" />
<link rel="stylesheet" href="/style.css" />
</head>
<body>
<!-- Every page is a sheet of paper lying on the source it was built
from. This checkbox lifts the sheet; no JavaScript involved. -->
<input type="checkbox" id="xray" class="xray" aria-label="Show the source of this page" />
<div class="desk">
<div class="sheet">
<!-- Under the paper, the page's source, for the candle to show. -->
<div class="underside" aria-hidden="true"><sky-sources item="underside.html" /></div>
<div class="paper" aria-hidden="true"></div>
<svg class="flame" viewBox="0 0 24 44" aria-hidden="true">
<defs>
<radialGradient id="flame-body" cx="50%" cy="78%" r="62%">
<stop offset="0" stop-color="#fffbe8" />
<stop offset="0.35" stop-color="#ffe08a" />
<stop offset="0.7" stop-color="#ff9a2e" />
<stop offset="1" stop-color="#e2470f" stop-opacity="0" />
</radialGradient>
<radialGradient id="flame-core" cx="50%" cy="80%" r="55%">
<stop offset="0" stop-color="#ffffff" />
<stop offset="0.6" stop-color="#fff3c4" />
<stop offset="1" stop-color="#ffd166" stop-opacity="0" />
</radialGradient>
</defs>
<path class="flame-body" fill="url(#flame-body)" d="M12 1C15 11 22 18 21 29 20 37 16 43 12 43 8 43 4 37 3 29 2 18 9 11 12 1Z" />
<path class="flame-core" fill="url(#flame-core)" d="M12 15C14 21 17 26 16.5 32 16 37 14 40 12 40 10 40 8 37 7.5 32 7 26 10 21 12 15Z" />
<ellipse class="flame-base" cx="12" cy="40" rx="3.2" ry="2" fill="#5aa9ff" opacity="0.45" />
</svg>
<label for="xray" class="curl" title="Lift the page to see what it's made of" aria-hidden="true"></label>
<label for="xray" class="sheet-cover" title="Back to the page"></label>
<sky-include path="_nav.html" />
<main class="page">
<sky-slot name="content" />
</main>
<sky-include path="_footer.html" />
</div>
<aside class="ground" aria-label="The source of this page">
<header class="ground-head">
<p>
<a href="https://github.com/mas-4/skyblue">skyblue</a> built this
page from these files, in the order it used them.
</p>
<label for="xray" class="ground-close">back to the page →</label>
</header>
<sky-sources item="source.html" />
</aside>
</div>
<script><sky-include path="candle.js" /></script>
</body>
</html>
// The light switch. Until it's flipped, the page follows the system's
// light or dark preference (that part is CSS). Flipping it picks the other
// one and remembers it. This runs in <head>, so a saved choice applies
// before the page is drawn.
(() => {
const root = document.documentElement;
const system = matchMedia("(prefers-color-scheme: dark)");
try {
const saved = localStorage.getItem("theme");
if (saved === "light" || saved === "dark") root.dataset.theme = saved;
} catch {}
const isDark = () => (root.dataset.theme ? root.dataset.theme === "dark" : system.matches);
document.addEventListener("DOMContentLoaded", () => {
const button = document.querySelector(".theme-toggle");
if (!button) return;
const show = () => button.setAttribute("aria-checked", String(isDark()));
button.hidden = false;
show();
system.addEventListener("change", show);
button.addEventListener("click", () => {
root.dataset.theme = isDark() ? "light" : "dark";
try {
localStorage.setItem("theme", root.dataset.theme);
} catch {}
show();
});
});
})();
<header class="site-header">
<nav class="nav">
<a class="brand" href="/">
<svg class="brand-mark" viewBox="0 0 32 32" aria-hidden="true">
<path d="M2 13c4 0 4-3 7-3s3 3 7 3 4-3 7-3 3 3 7 3" />
<path d="M2 20c4 0 4-3 7-3s3 3 7 3 4-3 7-3 3 3 7 3" />
</svg>
${meta.title}
</a>
<div class="nav-links">
<a href="/">home</a>
<a href="/about">about</a>
<a href="/projects">projects</a>
<a href="/orbits">orbits</a>
<label for="xray" class="source-toggle" title="Lift the page to see what it's made of">source</label>
</div>
<button type="button" class="theme-toggle" role="switch" aria-checked="false" aria-label="Dark mode" title="Light or dark" hidden><span class="knob"></span></button>
</nav>
</header>
<footer class="site-footer">
<div class="social">
<a href="https://github.com/mas-4">
<svg
aria-labelledby="svg-inline--fa-title-Yppzrr98YU17"
role="img"
xmlns="http://www.w3.org/2000/svg"
viewBox="0 0 496 512"
>
<title id="svg-inline--fa-title-Yppzrr98YU17">GitHub</title>
<path
fill="currentColor"
d="M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3zm44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"
></path>
</svg>
</a>
<a href="https://stackoverflow.com/users/9691276/mas">
<svg
aria-labelledby="svg-inline--fa-title-kGxnyVLHc64Z"
role="img"
xmlns="http://www.w3.org/2000/svg"
viewBox="0 0 384 512"
>
<title id="svg-inline--fa-title-kGxnyVLHc64Z">StackOverflow</title>
<path
fill="currentColor"
d="M290.7 311L95 269.7 86.8 309l195.7 41zm51-87L188.2 95.7l-25.5 30.8 153.5 128.3zm-31.2 39.7L129.2 179l-16.7 36.5L293.7 300zM262 32l-32 24 119.3 160.3 32-24zm20.5 328h-200v39.7h200zm39.7 80H42.7V320h-40v160h359.5V320h-40z"
></path>
</svg>
</a>
<a href="https://www.linkedin.com/in/michael-sendker">
<svg
aria-labelledby="svg-inline--fa-title-BaV39z6dqIIX"
role="img"
xmlns="http://www.w3.org/2000/svg"
viewBox="0 0 448 512"
>
<title id="svg-inline--fa-title-BaV39z6dqIIX">LinkedIn</title>
<path
fill="currentColor"
d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3zM135.4 416H69V202.2h66.5V416zm-33.2-243c-21.3 0-38.5-17.3-38.5-38.5S80.9 96 102.2 96c21.2 0 38.5 17.3 38.5 38.5 0 21.3-17.2 38.5-38.5 38.5zm282.1 243h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9V416z"
></path>
</svg>
</a>
<a href="https://raw.githubusercontent.com/mas-4/resume/master/main.pdf">
<svg
aria-labelledby="svg-inline--fa-title-fmQP80A0S9GF"
role="img"
xmlns="http://www.w3.org/2000/svg"
viewBox="0 0 384 512"
>
<title id="svg-inline--fa-title-fmQP80A0S9GF">Résumé</title>
<path
fill="currentColor"
d="M181.9 256.1c-5-16-4.9-46.9-2-46.9 8.4 0 7.6 36.9 2 46.9zm-1.7 47.2c-7.7 20.2-17.3 43.3-28.4 62.7 18.3-7 39-17.2 62.9-21.9-12.7-9.6-24.9-23.4-34.5-40.8zM86.1 428.1c0 .8 13.2-5.4 34.9-40.2-6.7 6.3-29.1 24.5-34.9 40.2zM248 160h136v328c0 13.3-10.7 24-24 24H24c-13.3 0-24-10.7-24-24V24C0 10.7 10.7 0 24 0h200v136c0 13.2 10.8 24 24 24zm-8 171.8c-20-12.2-33.3-29-42.7-53.8 4.5-18.5 11.6-46.6 6.2-64.2-4.7-29.4-42.4-26.5-47.8-6.8-5 18.3-.4 44.1 8.1 77-11.6 27.6-28.7 64.6-40.8 85.8-.1 0-.1.1-.2.1-27.1 13.9-73.6 44.5-54.5 68 5.6 6.9 16 10 21.5 10 17.9 0 35.7-18 61.1-61.8 25.8-8.5 54.1-19.1 79-23.2 21.7 11.8 47.1 19.5 64 19.5 29.2 0 31.2-32 19.7-43.4-13.9-13.6-54.3-9.7-73.6-7.2zM377 105L279 7c-4.5-4.5-10.6-7-17-7h-6v128h128v-6.1c0-6.3-2.5-12.4-7-16.9zm-74.1 255.3c4.1-2.7-2.5-11.9-42.8-9 37.1 15.8 42.8 9 42.8 9z"
></path>
</svg>
</a>
</div>
<!-- skyblue fills these in as it builds the site. -->
<pre class="receipt" aria-label="How this page was built"><span class="prompt">$</span> skyblue --version
skyblue <a href="https://github.com/mas-4/skyblue">${sky.version}</a> (compiled by cprime <a href="https://github.com/mas-4/cprime">${sky.compiler}</a>)
<span class="prompt">$</span> skyblue -i src -o build
skyblue: ${sky.pages} pages and ${sky.files} files -> build
<span class="note"># ${sky.date}, ${sky.time}, ${sky.ms} ms. Two small scripts: the candle and the light switch.</span></pre>
<p class="copyright">© 2022–2026 Michael Sendker</p>
</footer>
// The candle. Hold the pointer over the words and a flame lights above
// them: the paper warms and thins, and the page's source shows through
// from underneath. Only over the letters themselves, not blank paper.
// Without this script the paper simply stays opaque.
(() => {
const sheet = document.querySelector(".sheet");
if (!sheet || !matchMedia("(hover: hover) and (pointer: fine)").matches) return;
// Is (x, y) on a letter? Find the text position under the point, then
// check that the point is inside the box of the character on either side.
const range = document.createRange();
const overGlyph = (x, y) => {
let node, offset;
if (document.caretPositionFromPoint) {
const pos = document.caretPositionFromPoint(x, y);
if (pos) [node, offset] = [pos.offsetNode, pos.offset];
} else if (document.caretRangeFromPoint) {
const r = document.caretRangeFromPoint(x, y);
if (r) [node, offset] = [r.startContainer, r.startOffset];
}
if (!node || node.nodeType !== Node.TEXT_NODE || !sheet.contains(node)) return false;
for (const i of [offset - 1, offset]) {
if (i < 0 || i >= node.length || /\s/.test(node.data[i])) continue;
range.setStart(node, i);
range.setEnd(node, i + 1);
for (const box of range.getClientRects())
if (x >= box.left && x <= box.right && y >= box.top && y <= box.bottom) return true;
}
return false;
};
let x = 0, y = 0, queued = false, dousing = 0;
const draw = () => {
queued = false;
const box = sheet.getBoundingClientRect();
sheet.style.setProperty("--cx", x - box.left + "px");
sheet.style.setProperty("--cy", y - box.top + "px");
if (overGlyph(x, y)) {
clearTimeout(dousing);
dousing = 0;
sheet.classList.add("lit");
} else if (!dousing && sheet.classList.contains("lit")) {
// A moment's grace, so it doesn't strobe across the spaces between words
dousing = setTimeout(() => {
sheet.classList.remove("lit");
dousing = 0;
}, 350);
}
};
sheet.addEventListener("pointermove", (e) => {
[x, y] = [e.clientX, e.clientY];
if (!queued) {
queued = true;
requestAnimationFrame(draw);
}
});
sheet.addEventListener("pointerleave", () => {
clearTimeout(dousing);
dousing = 0;
sheet.classList.remove("lit");
});
})();
<section class="source">
<header class="source-head">
<a href="https://github.com/mas-4/standingwater-flat/blob/main/src/${source.path}">${source.path}</a>
<span>${source.lines} lines</span>
</header>
<pre class="listing"><code>${source.code}</code></pre>
</section>
<pre class="listing"><code>${source.code}</code></pre>
