A PS1 with Docker context and Kubernetes context (including namespace)

.bash_profile

PS1='(k:$(kubernetes-context) | d:$(docker-context "%s") | g:$(__git_ps1 "%s"))\n\W $ '

function docker-context()
{
    if [ -z "$DOCKER_HOST" ]; then
      printf "localhost"
    else
      local HOSTNAME_REGEX=".*//(.*):.*"
      [[ $DOCKER_HOST =~ $HOSTNAME_REGEX ]]
      printf ${BASH_REMATCH[1]}
    fi
}

function kubernetes-context()
{
    local KUBERNETES_CONTEXT=$(kubectl config current-context)
    local HAS_NAMESPACE=$(kubectl config view -o jsonpath='{.contexts[?(@.name == "'"$KUBERNETES_CONTEXT"'")].context.namespace}')
    local NAMESPACE=${HAS_NAMESPACE:-default}

    printf $KUBERNETES_CONTEXT[$NAMESPACE]
}

# __git_ps1 is just the standard __git_ps1 from https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh