#!/usr/bin/env bash

# Greatly inspired by https://github.com/k8spatterns/examples/blob/master/advanced/Controller/config-watcher-controller.sh.

# API URL setup. Requires an ambassador API proxy running side-by-side on localhost
base="http://localhost:8001"
ns="namespaces/default"

# Main event loop
start_event_loop() {
  # Watch the K8s API on events on service objects
  echo "::: Starting to wait for events"

  # Event loop listening for changes in config maps
  curl -N -s "$base/api/v1/$ns/configmaps?watch=true" | while read -r event
  do
    # Event type & name
    local type=$(echo "${event}" | jq -r .type)
    local config_map=$(echo "${event}" | jq -r .object.metadata.name)

    # Fetch annotations of ConfigMap and extract our trigger annotation if any
    # The extracted pod selector is expected to have
    # the format "label1=value1,label2=value2,.."
    local annotations=$(echo "${event}" | jq -r '.object.metadata.annotations')
    local pod_selector=""
    if [[ "${annotations}" != "null" ]]; then
      pod_selector=$(echo ${annotations} | jq -r 'to_entries | .[] | select(.key == "k8spatterns.io/podDeleteSelector") | .value')
    fi
    echo "::: ${type} -- ${config_map} -- ${pod_selector}"

    # Act only when configmap is modified and an annotation has been given
    if [[ ${type} = "MODIFIED" ]] && [[ -n "${pod_selector}" ]]; then
      delete_pods_with_selector "${pod_selector}"
    fi
  done
}

# Delete all pods that match a selector
delete_pods_with_selector() {
  local selector=${1}

  echo "::::: Deleting pods with $selector"

  # Pick up all pod names which match the given selector
  local pods=$(curl -s ${base}/api/v1/${ns}/pods?labelSelector=${selector} | \
               jq -r .items[].metadata.name)

  # Delete all pods that matched
  for pod in ${pods}; do
    # Delete but also check exit code
    exit_code=$(curl -s -X DELETE -o /dev/null -w "%{http_code}" ${base}/api/v1/${ns}/pods/${pod})
    if [[ ${exit_code} -eq 200 ]]; then
      echo "::::: Deleted pod $pod"
    else
      echo "::::: Error deleting pod $pod: $exit_code"
    fi
  done
}

# ==============================================
# Fire up
start_event_loop