Autodoc

autodoc

Generate thorough, well-placed documentation for undocumented or legacy code in this codebase. The goal is docs a new engineer could actually use — not a code dump, but a clear explanation of what exists, how it works, and what to watch out for.

What the user gives you

The user will point at something in one of these ways:

• A path: app/lib/MC/Campaigns/ or app/lib/MC/Billing/TaxCalculator.php
• Natural language: "the campaign sending system", "how billing handles EU tax"
• Both: "document the retry logic in batch/process_automations.php"

If they're vague, ask one clarifying question before proceeding. Don't ask multiple questions at once.

---

Step 1: Locate the code

If given a path, verify it exists and read it. If given natural language, find the relevant files first using search and glob before reading anything deeply.

Good search strategies:

• Grep for class/function names matching the concept
• Glob directories that match the domain (e.g. app/lib/MC/Campaign*/**/*.php)
• Check app/controllers/, app/lib/MC/, batch/, web/js/src/ depending on context
• Look at app/lib/Autolyse/Services.php or app/lib/Avarice/Services.php to find gRPC service registrations

Cast a wide net first, then narrow. A legacy system often spans multiple files and directories.

---

Step 2: Read deeply

Don't skim. Read the actual code — the class structure, method signatures, database calls, service dependencies, flag checks, and comments. Things to specifically look for:

Understand the shape:

• What does this system do at a high level?
• What are the main entry points (controller actions, gRPC RPCs, batch scripts, queue consumers)?
• What does it read from and write to (DB tables, caches, external services)?
• What other systems does it call or depend on?

Spot the debt signals:

• // TODO, // FIXME, // HACK, // legacy, // deprecated comments
• Dojo frontend code (being migrated to React)
• PHP 7.4-style code patterns in a PHP 8.3 migration context
• Duplicated logic across files (same thing done multiple ways)
• Deep inheritance chains or abstract classes (anti-pattern here)
• Named arrays passed as data (should be classes)
• Missing observability (no logging, no traces)
• Flag checks that suggest the system is mid-migration

The presence and density of debt signals determines the doc format (see Step 3).

---

Step 3: Choose the doc format

Use reference/how-to when:

• The system is reasonably stable and well-structured
• The main value is "here's how to use this / work with this"
• Examples: docs/autolyse.md, docs/feature-flags.md, docs/automations.md

Structure:

# [System Name]

## Overview
One paragraph explaining what this is and why it exists.

## [Core concept / main components]
What the key pieces are.

## How it works
The flow — entry points, data path, outputs.

## Common tasks
How to do the 2-3 most common things an engineer would need to do.

## Gotchas
Things that will bite you if you don't know them.

## See also
Links to related code and docs.

Use current-state analysis when:

• There are significant debt signals or known divergence
• The system is pre-refactor or mid-migration
• The main value is "here's what we have and what's wrong with it"
• Examples: docs/audience/current_state/*.md

Structure:

# [System]: Current State

## Overview
What this system does today.

## Architecture
How it's structured — key files, classes, data flows.

## Problem areas
Each major issue, with evidence from the code. Be specific — file paths, line numbers, method names.

## Compliance / risk notes
If any GDPR, CAN-SPAM, or sharding concerns are visible.

## Recommended next steps
What would improve this — not a full redesign, just the highest-leverage changes.

Offer an ADR as well when:

• You see evidence of a significant architectural decision that isn't documented
• Something exists in a non-obvious way and the "why" isn't clear from the code

---

Step 4: Infer where the doc should live

Map the code's domain to the right location in docs/:

Code location	Doc location
app/lib/MC/Campaign*/	docs/campaigns/
app/lib/MC/AudienceManagement*/	docs/audience/
app/lib/MC/Billing*/	docs/billing/
app/lib/MC/Automations*/	docs/automations/ (or docs/automations.md if small)
app/lib/MC/API30/	docs/api/
batch/	docs/batch-jobs/
web/js/src/Main/[Feature]/	docs/[feature]/ or flat file if small
Cross-cutting / platform	flat file in docs/

If the target subdirectory doesn't exist, create it with a README.md index.

For current-state analysis, place in docs/[domain]/current_state/[topic].md. For reference docs, place as docs/[domain]/[topic].md or a flat file if small.

---

Step 5: Write the doc

Write the full document using this repo's conventions:

• Tables for mapping relationships, directory structure, or option comparisons
• Code blocks with language tags for all code examples — use real examples from the code you read, not invented ones
• Headers to divide sections (H2 for major sections, H3 for subsections)
• Bold for key terms on first use
• Trailing newline at end of file
• Cross-reference other docs in docs/ where relevant using relative links
• For current-state docs, cite specific file paths and line numbers as evidence — this makes the doc credible and actionable
• If the system has a meaningful data flow or architecture that benefits from a diagram, note it as a PlantUML block (don't render it, just include the .puml source inline)

Write for a new engineer who knows PHP and React but hasn't touched this part of the codebase. Don't write for yourself or for someone who already knows — explain the non-obvious things.

---

Step 6: Confirm placement, then write

Before writing the file, tell the user:

"I'll write this to docs/[path]/[filename].md as a [reference doc / current-state analysis]. Does that location work?"

If they say yes (or don't object), write the file. Don't commit it — leave that to the author after they've reviewed and edited.

After writing, tell the user the file path and suggest they review it before committing. If you produced a current-state analysis, offer to also draft an ADR if an architectural decision was evident.

---

Reference: doc conventions in this repo

If you're unsure about tone or structure, read an existing doc first:

• Reference/how-to example: docs/autolyse.md
• Domain analysis example: docs/audience/current_state/am_sms_duplication.md
• ADR example: docs/audience/decisions/contact_profile_service/ADR-001-labels-separate-from-properties.md