name: main-verify

# The head of main always gets a complete `ci` run. A push run is no longer cancelled by the next push (ci.yml), but it can still be cancelled by hand or lost
# to an outage, and then nothing would test the head. Every 20 minutes this finds the head of main; when no `ci` run of main that completed, not cancelled,
# belongs to that commit and none is waiting or running for it, it dispatches one (a dispatch run covers every job of the quick tier). Dispatching needs no
# token beyond the one of the run: a workflow_dispatch made with it starts a run.
# No scheduled run is enabled in this repository: dispatch the workflow to run it.
on:
  workflow_dispatch:

permissions:
  actions: write
  contents: read

concurrency:
  group: main-verify
  cancel-in-progress: false

jobs:
  verify:
    runs-on: ubuntu-24.04
    timeout-minutes: 5
    steps:
      - name: Dispatch ci when the head of main has no finished run
        env:
          GH_TOKEN: ${{ github.token }}
          GH_REPO: ${{ github.repository }}
        run: |
          head=$(gh api "repos/$GH_REPO/branches/main" --jq '.commit.sha + " " + .commit.commit.committer.date')
          sha=${head% *}
          age=$(( $(date +%s) - $(date -d "${head#* }" +%s) ))
          # the push run of a commit that just landed is starting
          if [ "$age" -lt 600 ]; then
            echo "head ${sha:0:8} is $age s old: its push run is still starting" | tee -a "$GITHUB_STEP_SUMMARY"
            exit 0
          fi
          runs=$(gh run list --workflow ci.yml --branch main --limit 100 --json headSha,status,conclusion,event)
          state=$(jq -r --arg sha "$sha" '
            [.[] | select(.headSha == $sha)] as $mine
            | if any($mine[]; .status == "completed" and (.conclusion == "success" or .conclusion == "failure" or .conclusion == "timed_out")) then "finished"
              elif any(.[]; .status != "completed" and (.headSha == $sha or .event == "workflow_dispatch")) then "running"
              else "missing" end' <<<"$runs")
          echo "head ${sha:0:8}: $state" | tee -a "$GITHUB_STEP_SUMMARY"
          if [ "$state" = missing ]; then
            gh workflow run ci.yml --ref main
            echo "dispatched ci on main" | tee -a "$GITHUB_STEP_SUMMARY"
          fi