github_workflows_validate-markdownpage-date.yml

name: Validate markdownpages frontmatter date

on:
  pull_request:
    paths:
      - 'markdownpages/**'
  push:
    branches: [ main ]
    paths:
      - 'markdownpages/**'

permissions:
  contents: read

jobs:
  validate-date:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Validate frontmatter date is today
        shell: bash
        run: |
          set -euo pipefail

          # Determine base/head for changed files
          if [[ "${{ github.event_name }}" == "pull_request" ]]; then
            BASE="${{ github.event.pull_request.base.sha }}"
            HEAD="${{ github.event.pull_request.head.sha }}"
          else
            BASE="${{ github.event.before }}"
            HEAD="${{ github.sha }}"
          fi

          TODAY="$(TZ=UTC0 git show -s --date=format:%Y-%m-%d --format=%cd "$HEAD")"
          echo "Expected date (UTC): $TODAY"

          if ! CHANGED_FILES=$(git diff --name-only "$BASE" "$HEAD" -- 'markdownpages/**/*.md' 'markdownpages/*.md'); then
            echo "::error::Failed to determine changed markdownpages files between $BASE and $HEAD"
            exit 1
          fi

          if [[ -z "$CHANGED_FILES" ]]; then
            echo "No changed files in markdownpages."
            exit 0
          fi

          FAIL=0

          while IFS= read -r file; do
            [[ -f "$file" ]] || continue

            # Extract frontmatter (between first two --- lines) and read date
            FRONTMATTER=$(awk '
              NR==1 && $0=="---" {infm=1; next}
              infm && $0=="---" {exit}
              infm {print}
            ' "$file")

            if [[ -z "$FRONTMATTER" ]]; then
              echo "::error file=$file::No frontmatter found."
              FAIL=1
              continue
            fi

            FILE_DATE=$(printf "%s\n" "$FRONTMATTER" | sed -nE 's/^date:[[:space:]]*"?([0-9]{4}-[0-9]{2}-[0-9]{2})"?$/\1/p' | head -n1)

            if [[ -z "$FILE_DATE" ]]; then
              echo "::error file=$file::No valid date: YYYY-MM-DD in frontmatter."
              FAIL=1
              continue
            fi

            if [[ "$FILE_DATE" != "$TODAY" ]]; then
              echo "::error file=$file::Frontmatter date '$FILE_DATE' must be '$TODAY'."
              FAIL=1
            else
              echo "OK: $file date is $FILE_DATE"
            fi
          done <<< "$CHANGED_FILES"

          if [[ "$FAIL" -ne 0 ]]; then
            echo "Validation failed."
            exit 1
          fi

          echo "All changed markdownpages files have today's date."