#!/usr/bin/env bash
set -euo pipefail

# Draws the Flux Kustomization dependency graph from the dependsOn fields in
# kubernetes/clusters/homelab. Edges point from a dependency to its dependent.
#
#   flux-graph.sh              DOT on stdout, every edge
#   flux-graph.sh out.dot      the same, written to out.dot
#   flux-graph.sh out.svg      rendered; out.png likewise
#
# Rendered output is the transitive reduction (tred): an edge implied by a
# longer path is left out, the order is the same.
#
# Green: infrastructure. Blue: the Velero restore chain. Dashed: nothing is
# health-checked. Grey fill: suspended.
#
# Needs jq, either yq (mikefarah's or the Python wrapper) and, to render,
# graphviz.

REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
CLUSTER_DIR="${REPO_ROOT}/kubernetes/clusters/homelab"
OUT="${1:-}"

command -v jq >/dev/null || { echo "jq not found" >&2; exit 1; }
command -v yq >/dev/null || { echo "yq not found" >&2; exit 1; }

# One JSON document per YAML document.
yaml_to_json() {
  if [[ "$(yq --version)" == *mikefarah* ]]; then
    yq eval-all -o=json -I=0 '.' "$@"
  else
    yq -c '.' "$@"
  fi
}

to_dot() {
  yaml_to_json "${CLUSTER_DIR}"/*.yaml | jq -r -s '
    [ .[]
      | select(.kind == "Kustomization"
               and .apiVersion == "kustomize.toolkit.fluxcd.io/v1") ] as $ks
    | "digraph flux {",
      "  rankdir=LR;",
      "  node [shape=box, style=\"rounded\", fontname=\"Helvetica\", fontsize=10];",
      "  edge [color=\"#888888\"];",
      ( $ks[]
        | .metadata.name as $n
        # healthChecks are ignored under wait: true; without either, nothing
        # is checked, healthCheckExprs included.
        | (if .spec.wait == true then "wait"
           elif ((.spec.healthChecks // []) | length) > 0 then "health checks"
           else "wait: false" end) as $wait
        | (if .spec.suspend == true then ", style=\"rounded,filled\", fillcolor=\"#dddddd\""
           elif $wait == "wait: false" then ", style=\"rounded,dashed\""
           else "" end) as $dash
        | (if .spec.suspend == true then "\\nsuspended" else "" end) as $suspended
        | (if ($n | startswith("restore-")) or ($n | IN("velero", "velero-backups-synced"))
             then ", color=\"#1f77b4\", fontcolor=\"#1f77b4\""
           elif ($n | startswith("infrastructure")) or ($n | IN("crowdsec", "external-dns-unifi", "netbird-ingress", "velero-schedules"))
             then ", color=\"#2ca02c\", fontcolor=\"#2ca02c\""
           else "" end) as $colour
        | "  \"\($n)\" [label=\"\($n)\\n\($wait) · \(.spec.timeout // "-")\($suspended)\"\($dash)\($colour)];" ),
      ( $ks[]
        | .metadata.name as $n
        | (.spec.dependsOn // [])[]
        | "  \"\(.name)\" -> \"\($n)\";" ),
      "}"'
}

case "${OUT}" in
  "")
    to_dot
    ;;
  *.dot)
    to_dot > "${OUT}"
    ;;
  *.svg|*.png)
    command -v dot >/dev/null || { echo "graphviz (dot) not found" >&2; exit 1; }
    to_dot | tred | dot -T"${OUT##*.}" -Gdpi=110 -o "${OUT}"
    ;;
  *)
    echo "usage: $0 [out.dot|out.svg|out.png]" >&2
    exit 1
    ;;
esac