kc

#!/bin/bash

# To use this script, invoke it like so: `. kc <cluster or cluster alias>`.
# You can also `alias kc='. kc'` and thereby invoke `kc <cluster or cluster 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_CLUSTER_ALIASES="${KCKN_CLUSTER_ALIASES}"

__kckn_kc_main() {
  local cluster namespace user stub_kubeconfig stacked_kubeconfigs flattened_kubeconfig

  if [[ "$1" == off ]]; then
    unset KUBECONFIG
    unset __KCKN_KUBE_CLUSTER
    unset __KCKN_KUBE_NAMESPACE
    unset __KCKN
    return
  fi

  if [[ -z "$1" ]]; then
    >&2 echo "You must specify a cluster or 'off'"
    return 1
  fi

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

  cluster="$1"

  if grep "^${cluster} " "${KCKN_CLUSTER_ALIASES}" >/dev/null 2>&1; then
    cluster="$(grep "^${cluster} " "${KCKN_CLUSTER_ALIASES}" | awk '{print $2}')"
  fi
  
  namespace="${__KCKN_KUBE_NAMESPACE:-default}"

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

__kckn_kc_main "$@"