# SECURITY NOTE:
# This workflow uses pull_request_target with checkout from forks.
# Only git operations (rebase, push) are performed - no build/test scripts.
# Preflight checks require a repository collaborator to trigger rebase and,
# for fork PRs, maintainer_can_modify (Allow edits from maintainers).
# Do NOT add steps that execute untrusted code from the PR head.
name: Rebase user branch

on:
  pull_request_target:
    types: [labeled]
  workflow_dispatch:
    inputs:
      pull_number:
        description: 'Pull Request number to rebase'
        required: true
        type: string

concurrency:
  group: rebase-pr-${{ github.event_name == 'workflow_dispatch' && inputs.pull_number || github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  rebase:
    if: github.event_name == 'workflow_dispatch' || github.event.label.name == 'rebase-user-branch'

    runs-on: ubuntu-latest
    permissions:
      contents: write
      pull-requests: write
    env:
      WF_RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}

    steps:
      - name: Resolve pull request
        id: pr
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.GH_PERSONAL_ACCESS_TOKEN }}
          script: |
            let pr;
            if (context.eventName === 'workflow_dispatch') {
              const pullNumber = Number.parseInt(context.payload.inputs.pull_number, 10);
              if (!Number.isFinite(pullNumber) || pullNumber <= 0) {
                core.setFailed('pull_number must be a positive integer');
                return;
              }
              const { data } = await github.rest.pulls.get({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: pullNumber,
              });
              pr = data;
            } else {
              pr = context.payload.pull_request;
            }

            core.setOutput('number', String(pr.number));
            core.setOutput('state', pr.state);
            core.setOutput('head_sha', pr.head.sha);
            core.setOutput('head_ref', pr.head.ref);
            core.setOutput('head_repo_full_name', pr.head.repo.full_name);
            core.setOutput('head_repo_fork', pr.head.repo.fork ? 'true' : 'false');
            core.setOutput('maintainer_can_modify', pr.maintainer_can_modify ? 'true' : 'false');
            core.setOutput('base_ref', pr.base.ref);
            core.setOutput('base_repo_clone_url', pr.base.repo.clone_url);

      # Preconditions:
      # 1. Pull request must be open.
      # 2. Triggered by a repository collaborator (label sender or workflow_dispatch actor).
      # 3. For fork PRs, "Allow edits from maintainers" must be enabled.
      - name: Verify rebase preconditions
        id: preflight
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.GH_PERSONAL_ACCESS_TOKEN }}
          script: |
            const sender = context.eventName === 'workflow_dispatch'
              ? context.actor
              : context.payload.sender.login;
            let senderIsCollaborator = false;

            try {
              await github.rest.repos.checkCollaborator({
                owner: context.repo.owner,
                repo: context.repo.repo,
                username: sender,
              });
              senderIsCollaborator = true;
            } catch (error) {
              if (!error.status || error.status != 404) {
                throw error;
              }
            }

            const forkPushAllowed = '${{ steps.pr.outputs.head_repo_fork }}' !== 'true'
              || '${{ steps.pr.outputs.maintainer_can_modify }}' === 'true';

            core.setOutput('sender', sender);
            core.setOutput('pr_is_open', '${{ steps.pr.outputs.state }}' === 'open' ? 'true' : 'false');
            core.setOutput('sender_is_collaborator', senderIsCollaborator ? 'true' : 'false');
            core.setOutput('fork_push_allowed', forkPushAllowed ? 'true' : 'false');

      - name: Decline rebase — pull request is not open
        if: steps.preflight.outputs.pr_is_open != 'true'
        uses: actions/github-script@v7
        with:
          script: |
            const sender = '${{ steps.preflight.outputs.sender }}';
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;

            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: `⚠️ @${sender} Rebase declined: rebase can only be run on open pull requests.` + footer
            });

      - name: Decline rebase — trigger is not a collaborator
        if: steps.preflight.outputs.pr_is_open == 'true' && steps.preflight.outputs.sender_is_collaborator != 'true'
        uses: actions/github-script@v7
        with:
          script: |
            const sender = '${{ steps.preflight.outputs.sender }}';
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;

            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: `⚠️ @${sender} Rebase declined, only collaborator can rebase user branch` + footer
            });

      - name: Decline rebase — fork does not allow maintainer push
        if: steps.preflight.outputs.pr_is_open == 'true' && steps.preflight.outputs.sender_is_collaborator == 'true' && steps.preflight.outputs.fork_push_allowed != 'true'
        uses: actions/github-script@v7
        with:
          script: |
            const sender = '${{ steps.preflight.outputs.sender }}';
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;

            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: `⚠️ @${sender} Rebase declined: this PR is from a fork and **Allow edits from maintainers** is not enabled.\n\nThe PR author must enable it in the PR sidebar so maintainers can push the rebased branch. Alternatively, rebase locally and push to the fork.` + footer
            });

      - name: Fail if preconditions are not met
        if: steps.preflight.outputs.pr_is_open != 'true' || steps.preflight.outputs.sender_is_collaborator != 'true' || steps.preflight.outputs.fork_push_allowed != 'true'
        run: exit 1

      - name: Remove previous failure label
        uses: actions/github-script@v7
        with:
          script: |
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            try {
              await github.rest.issues.removeLabel({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: issueNumber,
                name: 'rebase-user-branch-failed'
              });
            } catch (error) {
              if (!error.status || error.status != 404) {
                throw error;
              }
            }

      - name: Checkout PR branch
        uses: actions/checkout@v4
        with:
          ref: ${{ steps.pr.outputs.head_sha }}
          repository: ${{ steps.pr.outputs.head_repo_full_name }}
          token: ${{ secrets.YDBOT_TOKEN }}
          fetch-depth: 0
          filter: blob:none

      - name: Configure git
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"

      - name: Fetch base branch
        env:
          BASE_REF: ${{ steps.pr.outputs.base_ref }}
          BASE_REPO: ${{ steps.pr.outputs.base_repo_clone_url }}
        run: |
          git remote set-url upstream "$BASE_REPO" 2>/dev/null || git remote add upstream "$BASE_REPO"
          git fetch upstream "refs/heads/$BASE_REF:refs/remotes/upstream/$BASE_REF"

      - name: Attempt rebase
        id: rebase
        continue-on-error: true
        env:
          BASE_REF: ${{ steps.pr.outputs.base_ref }}
        run: |
          if git rebase "upstream/$BASE_REF"; then
            echo "rebase_status=success" >> $GITHUB_OUTPUT
          else
            echo "rebase_status=failed" >> $GITHUB_OUTPUT
            git rebase --abort
          fi

      - name: Handle unexpected rebase failure
        if: steps.rebase.outputs.rebase_status == ''
        uses: actions/github-script@v7
        with:
          script: |
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;

            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: '❌ **Rebase failed unexpectedly.**\n\nPlease check the workflow logs or try re-applying the `rebase-user-branch` label.' + footer
            });

      - name: Fail on unexpected error
        if: steps.rebase.outputs.rebase_status == ''
        run: exit 1

      - name: Push rebased branch
        id: push
        if: steps.rebase.outputs.rebase_status == 'success'
        continue-on-error: true
        env:
          HEAD_REF: ${{ steps.pr.outputs.head_ref }}
        run: |
          git push --force-with-lease origin HEAD:"$HEAD_REF"

      - name: Add push failure comment
        if: steps.rebase.outputs.rebase_status == 'success' && steps.push.outcome == 'failure'
        uses: actions/github-script@v7
        with:
          script: |
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const isFork = '${{ steps.pr.outputs.head_repo_fork }}' === 'true';
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;
            const forkHint = isFork
              ? '\n\nIf this is a fork PR, verify that **Allow edits from maintainers** is still enabled.'
              : '';
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: '⚠️ **Rebase succeeded but push failed.**\n\nThe remote branch may have been updated.' + forkHint + '\n\nPlease re-apply the `rebase-user-branch` label to retry.' + footer
            });

      - name: Add success comment
        if: steps.push.outcome == 'success'
        uses: actions/github-script@v7
        env:
          BASE_REF: ${{ steps.pr.outputs.base_ref }}
        with:
          script: |
            const baseRef = process.env.BASE_REF;
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: `✅ **Rebase complete!**\n\nPR has been automatically rebased onto \`${baseRef}\`.` + footer
            });

      - name: Add failure comment for conflicts
        if: steps.rebase.outputs.rebase_status == 'failed'
        uses: actions/github-script@v7
        env:
          BASE_REF: ${{ steps.pr.outputs.base_ref }}
        with:
          script: |
            const baseRef = process.env.BASE_REF;
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            const isFork = '${{ steps.pr.outputs.head_repo_fork }}' === 'true';
            const upstreamUrl = 'https://github.com/' + context.repo.owner + '/' + context.repo.repo + '.git';
            const instructions = isFork
              ? 'git remote set-url upstream ' + upstreamUrl + ' 2>/dev/null || git remote add upstream ' + upstreamUrl + '\n' +
                'git fetch upstream\n' +
                'git rebase upstream/' + baseRef
              : 'git fetch origin\n' +
                'git rebase origin/' + baseRef;
            const footer = `\n\n---\n[Workflow run](${process.env.WF_RUN_URL})`;
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              body: '❌ **Rebase failed due to conflicts.**\n\nPlease resolve them manually:\n```\n' + instructions + '\n```\nAfter resolving conflicts and pushing your branch, PR checks will restart automatically.' + footer
            });

      - name: Fail the job if conflicts
        if: steps.rebase.outputs.rebase_status == 'failed'
        run: exit 1

      - name: Fail if push failed
        if: steps.rebase.outputs.rebase_status == 'success' && steps.push.outcome == 'failure'
        run: exit 1

      - name: Remove trigger label
        if: always() && steps.pr.outputs.number != ''
        uses: actions/github-script@v7
        with:
          script: |
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            try {
              await github.rest.issues.removeLabel({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: issueNumber,
                name: 'rebase-user-branch'
              });
            } catch (error) {
              if (!error.status || error.status != 404) {
                throw error;
              }
            }

      - name: Mark rebase as failed
        if: always() && steps.pr.outputs.number != '' && steps.push.outcome != 'success'
        uses: actions/github-script@v7
        with:
          script: |
            const issueNumber = Number.parseInt('${{ steps.pr.outputs.number }}', 10);
            await github.rest.issues.addLabels({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issueNumber,
              labels: ['rebase-user-branch-failed']
            });