C4 Code

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:

```mermaid
---
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:

```mermaid
---
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:

```mermaid
---
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