# Install Helm (Linux/macOS)
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

# Add a Repository (Bitnami)
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

# Install a named release. "my-redis" is the release name (must be unique
# within the namespace). "bitnami/redis" is the chart reference.
helm install my-redis bitnami/redis

# List all releases in the current namespace
helm list

# Uninstall a release and delete all its Kubernetes resources.
# NOTE: PVCs created by StatefulSets are NOT deleted by default.
# You must clean those up manually to avoid orphaned storage.
helm uninstall my-redis

# Dump the chart's default values to a file for inspection.
# This is the first thing you should do with any new chart.
helm show values bitnami/redis > values.yaml

# Edit values.yaml to match your environment:
#   - Set replica count, resource limits, persistence size
#   - Configure authentication, TLS, network policies
#   - Override image tags for your registry

# Install with a custom values file (preferred for reproducibility)
helm install -f values.yaml my-redis bitnami/redis

# OR use --set for quick overrides (fine for testing, avoid in CI/CD
# because --set values are not version-controlled)
helm install my-redis bitnami/redis --set architecture=replication --set auth.password=secret123

# Scaffold a new chart. This generates a complete, working chart
# with sensible defaults that you can customize.
helm create my-chart

my-chart/
  Chart.yaml          # Metadata: name, version, dependencies, description
  values.yaml         # Default configuration values (users override these)
  charts/             # Dependency charts (downloaded via helm dependency update)
  templates/          # Go template files that generate Kubernetes manifests
    deployment.yaml   # Main application Deployment
    service.yaml      # Service to expose the Deployment
    _helpers.tpl      # Reusable template snippets (naming conventions, labels)
    NOTES.txt         # Post-install instructions shown to the user
    tests/            # Helm test hooks (optional but recommended)

replicaCount: 3
image:
  repository: nginx
  tag: latest    # Pin to a specific tag in production, never use "latest"

apiVersion: apps/v1
kind: Deployment
metadata:
  # .Release.Name ensures unique names when the same chart is installed
  # multiple times in the same namespace (e.g., "staging-nginx", "prod-nginx")
  name: {{ .Release.Name }}-nginx
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
        - name: nginx
          # Always quote templated image references. Without quotes,
          # YAML parsing can break on certain tag formats.
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"

# Render templates locally without installing (critical for debugging)
helm template my-release ./my-chart -f values-prod.yaml

# Dry-run against the cluster (validates against the API server)
helm install my-release ./my-chart --dry-run --debug

# Lint the chart for common errors
helm lint ./my-chart

# Upgrade a release. Helm computes the diff between the current release
# and the new config, then applies only the changed resources.
helm upgrade my-redis bitnami/redis --set auth.password=newsecret

# View the full revision history (who deployed what and when)
helm history my-redis

# Rollback to revision 1. This creates a NEW revision (e.g., revision 3)
# that is a copy of revision 1. Helm never mutates history.
helm rollback my-redis 1

# Upgrade with --atomic: if the upgrade fails health checks within
# the timeout, Helm automatically rolls back. Highly recommended for CI/CD.
helm upgrade my-redis bitnami/redis -f values-prod.yaml --atomic --timeout 5m