I’m excited to share the first MVP release of NKP (aNalysis of Kotlin Programs), a command-line tool for analyzing Kotlin codebases and uncovering architectural insights.
What is NKP?
NKP examines Kotlin source code to surface structure, dependencies, and stability metrics. It helps answer questions like:
- How are my packages coupled?
- Which areas of my code are unstable?
- What does my class hierarchy look like?
Key Capabilities
NKP focuses on architectural understanding:
- Package coupling metrics (Afferent Ca, Efferent Ce, Instability I)
- Class and file analysis (hierarchies, inheritance, imports, declarations)
- Mermaid diagram generation
- Class hierarchies
- Package import flow
- Coupling relationships
- Search functionality for classes across the codebase
When to Use NKP
Use NKP for:
- Architectural assessment
- Refactoring planning and impact analysis
- Architecture documentation and onboarding
- Code reviews with architectural context
- Migration and modernization efforts
Limitations (for now)
This MVP emphasizes architecture, not general code quality metrics. Think JDepend for Kotlin, not Sonar or Detekt.
Example: Ray Tracer Analysis
Running NKP on my ray-tracer project showed:
- 203 classes across 37 packages
- Average package instability of 0.69 (69%)
- Clear separation between stable core packages (
math, colors, hits) and application layers
- High coupling in orchestration packages that need refactoring attention
The package coupling metrics helped identify that:
- Core domain packages (
math, colors) are very stable (I < 0.1)
- Application layer packages have high instability (I > 0.7)
- The
world package couples 14 different subsystems, indicating a need for better separation
This kind of insight is invaluable when planning architectural improvements.
Why Build NKP?
As someone who works with teams on architectural improvements and refactoring, I found myself needing better tools to understand Kotlin codebases. While there are excellent tools for Java (like JDepend), Kotlin’s package structure and syntax required a specialized approach.
NKP fills this gap by providing:
- Kotlin-specific analysis using the official Kotlin grammar tools
- Actionable metrics based on well-established software engineering principles (Robert C. Martin’s package coupling metrics)
- Visual output in the widely-supported Mermaid format
- CLI-first design for easy integration into scripts and CI/CD pipelines
Get Involved
NKP is open source and available on GitHub. If you work with Kotlin projects and need better insights into your architecture, give NKP a try. It’s particularly useful for:
- Understanding large codebases
- Planning refactoring efforts
- Documenting architecture
- Identifying coupling issues before they become technical debt
I’d love to hear your feedback and learn about your experiences using NKP on your projects!
