C4 Code Level: [Directory Name]

Use this skill when

• Working on c4 code level: [directory name] tasks or workflows
• Needing guidance, best practices, or checklists for c4 code level: [directory name]

Do not use this skill when

• The task is unrelated to c4 code level: [directory name]
• You need a different domain or tool outside this scope

Instructions

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.
• If detailed examples are required, open resources/implementation-playbook.md.

Overview

• Name: [Descriptive name for this code directory]
• Description: [Short description of what this code does]
• Location: [Link to actual directory path]
• Language: [Primary programming language(s)]
• Purpose: [What this code accomplishes]

Code Elements

Functions/Methods

• functionName(param1: Type, param2: Type): ReturnType
• Description: [What this function does]
• Location: [file path:line number]
• Dependencies: [what this function depends on]

Classes/Modules

• ClassName
• Description: [What this class does]
• Location: [file path]
• Methods: [list of methods]
• Dependencies: [what this class depends on]

Dependencies

Internal Dependencies

• [List of internal code dependencies]

External Dependencies

• [List of external libraries, frameworks, services]

Relationships

Optional Mermaid diagrams for complex code structures. Choose the diagram type based on the programming paradigm. Code diagrams show the internal structure of a single component.

Object-Oriented Code (Classes, Interfaces)

Use classDiagram for OOP code with classes, interfaces, and inheritance:

---
title: Code Diagram for [Component Name]
---
classDiagram
    namespace ComponentName {
        class Class1 {
            +attribute1 Type
            +method1() ReturnType
        }
        class Class2 {
            -privateAttr Type
            +publicMethod() void
        }
        class Interface1 {
            <<interface>>
            +requiredMethod() ReturnType
        }
    }

    Class1 ..|> Interface1 : implements
    Class1 --> Class2 : uses

### Functional/Procedural Code (Modules, Functions)

For functional or procedural code, you have two options:

**Option A: Module Structure Diagram** - Use `classDiagram` to show modules and their exported functions:

title: Module Structure for [Component Name]

classDiagram namespace DataProcessing { class validators { <<module>> +validateInput(data) Result~Data, Error~ +validateSchema(schema, data) bool +sanitize(input) string } class transformers { <<module>> +parseJSON(raw) Record +normalize(data) NormalizedData +aggregate(items) Summary } class io { <<module>> +readFile(path) string +writeFile(path, content) void } }

transformers --> validators : uses transformers --> io : reads from

**Option B: Data Flow Diagram** - Use `flowchart` to show function pipelines and data transformations:

title: Data Pipeline for [Component Name]

flowchart LR subgraph Input A[readFile] end subgraph Transform B[parseJSON] C[validateInput] D[normalize] E[aggregate] end subgraph Output F[writeFile] end

A -->|raw string| B B -->|parsed data| C C -->|valid data| D D -->|normalized| E E -->|summary| F

**Option C: Function Dependency Graph** - Use `flowchart` to show which functions call which:

title: Function Dependencies for [Component Name]

flowchart TB subgraph Public API processData[processData] exportReport[exportReport] end subgraph Internal Functions validate[validate] transform[transform] format[format] cache[memoize] end subgraph Pure Utilities compose[compose] pipe[pipe] curry[curry] end

processData --> validate processData --> transform processData --> cache transform --> compose transform --> pipe exportReport --> format exportReport --> processData

### Choosing the Right Diagram

| Code Style                       | Primary Diagram                  | When to Use                                             |
| -------------------------------- | -------------------------------- | ------------------------------------------------------- |
| OOP (classes, interfaces)        | `classDiagram`                   | Show inheritance, composition, interface implementation |
| FP (pure functions, pipelines)   | `flowchart`                      | Show data transformations and function composition      |
| FP (modules with ex