# yaml-language-server: $schema=https://json.schemastore.org/github-workflow.json

name: 'Agent Session Drift Check'

on:
  pull_request:
    branches:
      - 'main'
      - 'release/**'
    paths:
      - 'packages/cli/src/nonInteractiveCli.ts'
      - 'packages/cli/src/nonInteractiveCliAgentSession.ts'

concurrency:
  group: '${{ github.workflow }}-${{ github.head_ref || github.ref }}'
  cancel-in-progress: true

jobs:
  check-drift:
    name: 'Check Agent Session Drift'
    runs-on: 'ubuntu-latest'
    if: "github.repository == 'google-gemini/gemini-cli'"
    permissions:
      contents: 'read'
      pull-requests: 'write'
    steps:
      - name: 'Detect drift and comment'
        uses: 'actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea' # ratchet:actions/github-script@v8
        with:
          script: |-
            // === Pair configuration — append here to cover more pairs ===
            const PAIRS = [
              {
                legacy: 'packages/cli/src/nonInteractiveCli.ts',
                session: 'packages/cli/src/nonInteractiveCliAgentSession.ts',
                label: 'non-interactive CLI',
              },
              // Future pairs can be added here. Remember to also add both
              // paths to the `paths:` filter at the top of this workflow.
              // Example:
              // {
              //   legacy: 'packages/core/src/agents/local-invocation.ts',
              //   session: 'packages/core/src/agents/local-session-invocation.ts',
              //   label: 'local subagent invocation',
              // },
            ];
            // ============================================================

            const prNumber = context.payload.pull_request.number;
            const { owner, repo } = context.repo;

            // Use the API to list changed files — no checkout/git diff needed.
            const files = await github.paginate(github.rest.pulls.listFiles, {
              owner,
              repo,
              pull_number: prNumber,
              per_page: 100,
            });
            const changed = new Set(files.map((f) => f.filename));

            const warnings = [];
            for (const { legacy, session, label } of PAIRS) {
              const legacyChanged = changed.has(legacy);
              const sessionChanged = changed.has(session);
              if (legacyChanged && !sessionChanged) {
                warnings.push(
                  `**${label}**: \`${legacy}\` was modified but \`${session}\` was not.`,
                );
              } else if (!legacyChanged && sessionChanged) {
                warnings.push(
                  `**${label}**: \`${session}\` was modified but \`${legacy}\` was not.`,
                );
              }
            }

            const MARKER = '<!-- agent-session-drift-check -->';

            // Look up our existing drift comment (for upsert/cleanup).
            const comments = await github.paginate(github.rest.issues.listComments, {
              owner,
              repo,
              issue_number: prNumber,
              per_page: 100,
            });
            const existing = comments.find(
              (c) => c.user?.type === 'Bot' && c.body?.includes(MARKER),
            );

            if (warnings.length === 0) {
              core.info('No drift detected.');
              // If drift was previously flagged and is now resolved, remove the comment.
              if (existing) {
                await github.rest.issues.deleteComment({
                  owner,
                  repo,
                  comment_id: existing.id,
                });
                core.info(`Deleted stale drift comment ${existing.id}.`);
              }
              return;
            }

            const body = [
              MARKER,
              '### ⚠️ Invocation Drift Warning',
              '',
              'The following file pairs should generally be kept in sync during the AgentSession migration:',
              '',
              ...warnings.map((w) => `- ${w}`),
              '',
              'If this is intentional (e.g., a bug fix specific to one implementation), you can ignore this comment.',
              '',
              '_This check will be removed once the legacy implementations are deleted._',
            ].join('\n');

            if (existing) {
              core.info(`Updating existing drift comment ${existing.id}.`);
              await github.rest.issues.updateComment({
                owner,
                repo,
                comment_id: existing.id,
                body,
              });
            } else {
              core.info('Creating new drift comment.');
              await github.rest.issues.createComment({
                owner,
                repo,
                issue_number: prNumber,
                body,
              });
            }