Microtables - LLM Navigation Guide

Project Overview

A lightweight spreadsheet application designed for quick calculations — positioned between a calculator and a full office suite. The goal is fast loading with support for common spreadsheet operations.

Architecture

Frontend (/frontend/)

Language: ClojureScript (compiled via shadow-cljs)
Framework: Reagent + re-frame (React wrapper)
Build: Leiningen + shadow-cljs
Dev server: lein dev → localhost:8280

Server (/server/)

Language: JavaScript (ES6+ with Babel)
Framework: Express
Status: Minimal implementation - currently the frontend is fully functional standalone
Future: Will handle persistence and collaboration

Key Concepts

Data Structure

The spreadsheet data is a nested map: {column-letter {row-number {:value ...}}}

Example:

{"A" {1 {:value 78 :inbound [...]}
      3 {:value "=B2 * 4" :refs [...]}}
 "B" {2 {:value "=A1 + 3" :refs [...] :inbound [...]}}}

Formula System

Formulae start with = and are evaluated using math.js library
Range syntax supported: =sum(A1:A10)
Cell references create a doubly-linked tree structure:
- :refs - forward references (cells this formula depends on)
- :inbound - back references (cells that depend on this cell)
- :display - computed/evaluated value shown to user
- :value - raw user input
- :dirty - flag indicating re-evaluation needed

Evaluation Flow

When a cell changes, parse for references
Update forward (:refs) and back (:inbound) reference trees
Evaluate the cell
Recursively evaluate all cells in :inbound queue
Cycle detection prevents infinite loops

Important Files

Frontend Core Logic

frontend/src/cljs/microtables_frontend/core.cljs - App initialization
frontend/src/cljs/microtables_frontend/db.cljs - Data model definition
frontend/src/cljs/microtables_frontend/events.cljs - State mutations (re-frame)
frontend/src/cljs/microtables_frontend/subs.cljs - Data queries (re-frame)
frontend/src/cljs/microtables_frontend/evaluation.cljs - Formula evaluation engine
frontend/src/cljs/microtables_frontend/views/sheet.cljs - Grid rendering

Project Configuration

frontend/project.clj - Leiningen config
frontend/shadow-cljs.edn - ClojureScript build config

Development Notes

Almost everything is subject to change (architecture, structure, design)
The frontend currently operates completely standalone
Focus is on simplicity and performance for common use cases
Data structures prioritize clarity over micro-optimization (small dataset assumption)

Common Tasks

Run frontend: cd frontend && lein dev Install npm dependency: Add to shadow-cljs.edn, then restart Understand formula eval: Start in evaluation.cljs, trace through evaluate-from-cell Modify grid UI: Look in views/sheet.cljs

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