diff.yml

name: Diff HTML


on:
  pull_request:
    types:
      # Defaults
      - opened
      - synchronize
      - reopened
      # Additional
      - closed


env:
  BRANCH_NAME_HTML_OLD: __diff__html_old
  DIFF_CONTEXT: 5
  DIFF_TRUNCATE_TO_BYTES: 250000
  POST_COLLAPSE_GT_LINES: 10


jobs:

  Build:
    uses: ./.github/workflows/build.yml
    with:
      prettyfy: true
      skip_lints_tests: true
      sphinx_github_branch: __diff__html_old

  Commit:
    if: github.event.action == 'closed' && github.event.pull_request.merged && github.event.pull_request.base.ref == 'main'
    runs-on: ubuntu-latest
    needs: Build
    steps:
      - name: Fetch New HTML
        uses: actions/download-artifact@v4
        with:
          name: html
          path: html
      - name: Store HTML in Orphaned Branch
        uses: peaceiris/actions-gh-pages@v4
        with:
          commit_message: "[skip ci]"
          enable_jekyll: true  # Don't create .nojekyll
          force_orphan: true  # Discard git history
          github_token: "${{ secrets.GITHUB_TOKEN }}"
          publish_branch: "${{ env.BRANCH_NAME_HTML_OLD }}"
          publish_dir: html

  Diff:
    if: github.event.action != 'closed'
    runs-on: ubuntu-latest
    needs: Build
    steps:
      - name: Fetch Old HTML
        uses: actions/checkout@v4
        with:
          ref: "${{ env.BRANCH_NAME_HTML_OLD }}"
          path: html
      - name: Prepare for New HTML
        run: git -C html rm -r . && git -C html restore --staged .
      - name: Fetch new HTML
        uses: actions/download-artifact@v4
        with:
          name: html
          path: html
      - name: Git Status
        id: git_status
        run: |
          git -C html add .
          git -C html status --porcelain |tee git_status.txt
          if [ -s git_status.txt ]; then
            echo "changed=true" >> $GITHUB_OUTPUT
          else
            echo "no-changes=true" >> $GITHUB_OUTPUT
            rm -v git_status.txt
          fi
      - name: Git Diff
        id: git_diff
        if: hashFiles('git_status.txt')
        run: |
          git -C html diff --diff-filter=M --unified="$DIFF_CONTEXT" HEAD |grep -Pv "^(diff|index) " |tee git_diff.patch
          if [ -s git_diff.patch ]; then
            echo "modified=true" >> $GITHUB_OUTPUT
          else
            echo "no-modifications=true" >> $GITHUB_OUTPUT
            rm -v git_diff.patch
          fi
      - name: Truncate
        if: hashFiles('git_diff.patch')
        run: |
          cp git_diff.patch git_diff.patch.orig
          truncate_to=$(( DIFF_TRUNCATE_TO_BYTES - $(wc -c < git_status.txt) ))
          head --bytes="$truncate_to" git_diff.patch.orig > git_diff.patch
          if ! cmp -s git_diff.patch git_diff.patch.orig; then
            echo -e "\n\nTruncated" |tee -a git_diff.patch
            tail --bytes=+"$(( truncate_to + 1 ))" git_diff.patch.orig > git_diff.patch.truncated
          fi
          rm -v git_diff.patch.orig
      - name: Store Metafiles as Temporary Artifacts
        if: hashFiles('git_status.txt')
        uses: actions/upload-artifact@v4
        with:
          name: git_status_diff
          path: |
            git_status.txt
            git_diff.patch
            git_diff.patch.truncated
    outputs:
      changed: "${{ steps.git_status.outputs.changed }}"
      no-changes: "${{ steps.git_status.outputs.no-changes }}"
      modified: "${{ steps.git_diff.outputs.modified }}"
      no-modifications: "${{ steps.git_diff.outputs.no-modifications }}"

  Post:
    if: github.event.action != 'closed'
    runs-on: ubuntu-latest
    needs: Diff
    concurrency:
      cancel-in-progress: true
      group: diff-post
    env:
      HEADER_PREFIX: "Diff Against [Old HTML]"
      HEADER_URL_BASE: "https://github.com/${{ github.repository }}/tree"
    steps:
      - name: Fetch Metafiles
        if: needs.Diff.outputs.changed
        uses: actions/download-artifact@v4
        with:
          name: git_status_diff
      - name: Split Patch
        if: hashFiles('git_diff.patch')
        run: |
          PS4="\n\033[1;33m$PS4\033[0m"
          set -euxo pipefail
          sudo apt-get update
          sudo apt-get install -y rename splitpatch
          splitpatch git_diff.patch
          rm -v git_diff.patch
          rename 's/.patch.(\d{3})$/.$1.patch/' *.patch.???
          ls -lah
      - name: Post (No Changes)
        if: needs.Diff.outputs.no-changes
        uses: actions/github-script@v7
        with:
          script: |
            const url = `${process.env.HEADER_URL_BASE}/${process.env.BRANCH_NAME_HTML_OLD}`
            const header = `${process.env.HEADER_PREFIX}(${url})`
            const body = `*No HTML changes detected.*`
            await github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: `### ${header}\n\n${body}`
            })
      - name: Post (No Modified)
        if: needs.Diff.outputs.changed && needs.Diff.outputs.no-modifications
        uses: actions/github-script@v7
        with:
          script: |
            const url = `${process.env.HEADER_URL_BASE}/${process.env.BRANCH_NAME_HTML_OLD}`
            const header = `${process.env.HEADER_PREFIX}(${url})`

            const fs = require(`fs`)
            const gitStatus = fs.readFileSync(`git_status.txt`, {encoding:`utf8`, flag:`r`}).trimEnd()
            const body = `\`\`\`\n${gitStatus}\n\`\`\`\n`

            await github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: `### ${header}\n\n${body}`
            })
      - name: Post Diff
        if: needs.Diff.outputs.changed && needs.Diff.outputs.modified
        uses: actions/github-script@v7
        env:
          IS_TRUNCATED: "${{ hashFiles('git_diff.patch.truncated') }}"
        with:
          script: |
            const fs = require(`fs`)

            function genHeader() {
              const url = `${process.env.HEADER_URL_BASE}/${process.env.BRANCH_NAME_HTML_OLD}`
              var header = `${process.env.HEADER_PREFIX}(${url})`
              if (process.env.IS_TRUNCATED) {
                var size = fs.statSync(`git_diff.patch.truncated`).size
                header += ` (${size} Byte${size == 1 ? '' : 's'} Truncated)`
              }
              return header
            }

            function* yieldFileContents(dir, suffix) {
              const files = fs.readdirSync(dir).filter(fileName => fileName.endsWith(suffix))
              for (const fileName of files) {
                const contents = fs.readFileSync(fileName, {encoding:`utf8`, flag:`r`})
                yield {fileName: fileName.slice(0, -suffix.length), contents: contents}
              }
            }

            function collapse(fileName, contents) {
              var numLines = contents.match(/^/mg).length
              if (numLines > parseInt(process.env.POST_COLLAPSE_GT_LINES))
                return `<details>\n<summary>Show ${numLines} lines from ${fileName}</summary>\n\n${contents}\n</details>`
              return contents
            }

            // git status
            const gitStatus = fs.readFileSync(`git_status.txt`, {encoding:`utf8`, flag:`r`})
            var body = collapse(`git_status.txt`, `\`\`\`\n${gitStatus.trimEnd()}\n\`\`\``)

            // git diff
            for (const {fileName, contents} of yieldFileContents(`./`, `.patch`)) {
              body += `\n\n` + collapse(fileName, `\`\`\`diff\n${contents.trimEnd()}\n\`\`\``)
            }

            await github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: `### ${genHeader()}\n\n${body}`
            })