cleanup_caches.yml

name: Cleanup caches

on:
  workflow_run:
    workflows: [build]
    types: [completed]

concurrency:
  group: ${{ github.workflow }}
  cancel-in-progress: true

permissions:
  actions: write

jobs:
  cache:
    runs-on: ubuntu-latest
    steps:
      - run: |
          set -o pipefail
          gh cache list -L 1000 --json id,key,ref -S last_accessed_at -O desc > caches.json

          # Resolve the state of every pull request that owns a cache.
          for pr in $(jq -r '.[].ref | select(test("^refs/pull/[0-9]+/merge$")) |
                             split("/")[2]' caches.json | sort -u); do
            jq -n --arg pr "$pr" --arg state "$(gh pr view $pr --json state --jq .state)" \
                  '{($pr): $state}'
          done | jq -s 'add // {}' > prs.json

          jq -r --slurpfile prs prs.json --arg default "$DEFAULT_REF" '
            $prs[0] as $state |

            # Group caches by kind, dropping the timestamp or content hash
            # that every save appends to the key.
            def family: if startswith("msys2-") then "msys2"
                        elif test("-[0-9]+$") then "ccache"
                        else "other" end;
            def group:  if family == "msys2" then sub("-(files|state):.*$"; "")
                        else sub("-[0-9]+$"; "") end;

            [ .[] | . + { family: (.key | family),
                          group:  (.key | group),
                          pr:     (.ref | if test("^refs/pull/[0-9]+/merge$")
                                          then split("/")[2] else null end) } ]
            | map(select(.family != "other")) as $all

            # Caches of merged or closed pull requests, and msys2 caches
            # outside the default branch, which every ref restores from.
            | ( $all | map(select(
                  (.pr != null and $state[.pr] != "OPEN") or
                  (.family == "msys2" and .ref != $default)
                )) ) as $dead

            # Of the rest only the newest cache of each kind per ref is used.
            | ( ($all - $dead) | group_by([.ref, .group]) | map(.[1:]) | add // [] ) as $superseded

            | ($dead + $superseded)[] | "\(.id)\t\(.ref)\t\(.key)"
          ' caches.json |
          while IFS=$'\t' read -r id ref key; do
            echo "deleting $ref $key"
            gh cache delete "$id"
          done
    env:
      GH_REPO: ${{ github.repository }}
      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      DEFAULT_REF: refs/heads/${{ github.event.repository.default_branch }}