# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

A Kubernetes monitoring tool that checks for CronJobs not running according to schedule and sends Slack notifications. It runs as a container inside a K8s cluster, polling all CronJobs every 60 seconds.

## Common Commands

```bash
# Run tests
go test ./...

# Run tests with race detection and coverage
go test -race -coverprofile=coverage.txt ./...

# Build the binary
CGO_ENABLED=0 go build -o release/cron-checker -ldflags '-w -s'

# Check for vulnerabilities
govulncheck ./...

# Format and vet
go fmt ./...
go vet ./...

# Check for unused modules
go mod tidy
```

## Architecture

This is a single-file Go application (`main.go`) with comprehensive tests (`main_test.go`).

**Core Components:**
- `doCheck()` - Main loop that polls K8s CronJobs, parses cron schedules, and sends Slack alerts for overdue jobs
- `Client` / `ClientProvider` interfaces - Abstractions over K8s client for testability
- `ConfigProvider` / `InClusterProvider` - Handles K8s in-cluster authentication

**Key Dependencies:**
- `k8s.io/client-go` - Kubernetes API client
- `github.com/robfig/cron` - Cron schedule parsing
- `github.com/multiplay/go-slack` - Slack webhook integration
- `github.com/alecthomas/kingpin/v2` - CLI flag parsing

**Configuration:**
- `SLACK_URL` env var or `--slack-url` flag (required) - Slack webhook URL for notifications

## Building Docker Image

The Dockerfile performs a multi-stage build that runs fmt, vet, and tests before building:

```bash
docker build -t cron-checker .
```

To extract coverage report:
```bash
docker build --target export -o . .
```