kn

#!/bin/bash

# To use this script, invoke it like so: `. kn [namespace or namespace alias]`.
# You can also `alias kn='. kn'` and thereby invoke `kn [namespace or namespace alias]>`.

# The kubeconfigs generated by this script expect a base kubeconfig to
# define the cluster and user that it references.

KCKN_BASE_KUBECONFIG="${KCKN_BASE_KUBECONFIG:-${HOME}/.kube/config}"
KCKN_NAMESPACE_ALIASES="${KCKN_NAMESPACE_ALIASES}"

__kckn_kn_main() {
  local cluster namespace user stub_kubeconfig stacked_kubeconfigs flattened_kubeconfig

  if ! [[ -f "${KCKN_BASE_KUBECONFIG}" ]]; then
    >&2 echo "Base kubeconfig does not exist: ${KCKN_BASE_KUBECONFIG}"
    return 1
  fi

  namespace="${1:-default}"

  if grep "^${namespace} " "${KCKN_NAMESPACE_ALIASES}" >/dev/null 2>&1; then
    namespace="$(grep "^${namespace} " "${KCKN_NAMESPACE_ALIASES}" | awk '{print $2}')"
  fi

  cluster="${__KCKN_KUBE_CLUSTER}"

  if [[ -z "${cluster}" ]]; then
    >&2 echo "No cluster is currently set"
    return 1
  fi
  
  if grep "^${cluster} " "${KCKN_CLUSTER_USERS}" >/dev/null 2>&1; then
    user="$(grep "^${cluster} " "${KCKN_CLUSTER_USERS}" | awk '{print $2}')"
  else
    user="${cluster}"
  fi

  stub_kubeconfig="$(mktemp)"

  cat <<KUBECONFIG > "${stub_kubeconfig}"
apiVersion: v1
kind: Config

contexts:
- context:
    cluster: ${cluster}
    user: ${user}
    namespace: ${namespace}
  name: ${cluster}/${namespace}
$(
if [[ "$namespace" == "default" ]]; then
  cat <<DEFAULTCONTEXT
# for the default namespace, also define a context whose name doesn't
# include the namespace.
- context:
    cluster: ${cluster}
    user: ${user}
    namespace: ${namespace}
  name: ${cluster}
DEFAULTCONTEXT
fi
)

current-context: ${cluster}/${namespace}

KUBECONFIG

  stacked_kubeconfigs="${stub_kubeconfig}:${KCKN_BASE_KUBECONFIG}"
  flattened_kubeconfig="$(mktemp)"
  KUBECONFIG="${stacked_kubeconfigs}" kubectl config view --flatten > "${flattened_kubeconfig}"

  # shellcheck disable=SC2034 # Variable to be consumed by user, e.g. in PS1
  export __KCKN="${cluster}/${namespace}"
  # shellcheck disable=SC2034 # Variable to be consumed by user, e.g. in PS1
  export __KCKN_KUBE_NAMESPACE="${namespace}"
  # shellcheck disable=SC2034 # Variable to be consumed by user, e.g. in PS1
  export KUBECONFIG="${flattened_kubeconfig}"
}

__kckn_kn_main "$@"