name: Bot Cherry Pick to Release Branch

on:
  workflow_dispatch:
    inputs:
      pr_number:
        description: 'PR number to cherry-pick (preferred). Provide either pr_number OR commit_sha, not both.'
        required: false
        type: string
      commit_sha:
        description: 'Commit SHA to cherry-pick (alternative to pr_number; full or short hash).'
        required: false
        type: string
      target_branch:
        description: 'Target release branch (e.g., release/v0.5.7)'
        required: true
        type: string

permissions:
  contents: write
  pull-requests: write

jobs:
  cherry-pick:
    if: github.repository == 'sgl-project/sglang'
    runs-on: ubuntu-latest
    steps:
      - name: Validate inputs
        env:
          TARGET_BRANCH: ${{ github.event.inputs.target_branch }}
          PR_NUMBER: ${{ github.event.inputs.pr_number }}
          COMMIT_SHA_INPUT: ${{ github.event.inputs.commit_sha }}
        run: |
          if [[ ! "$TARGET_BRANCH" =~ ^release/v[0-9]+\.[0-9]+(\.[0-9]+)?$ ]]; then
            echo "::error::Target branch must match pattern 'release/vX.Y' or 'release/vX.Y.Z' (e.g., release/v0.5.7)"
            exit 1
          fi

          if [[ -z "$PR_NUMBER" && -z "$COMMIT_SHA_INPUT" ]]; then
            echo "::error::Provide either 'pr_number' or 'commit_sha'."
            exit 1
          fi
          if [[ -n "$PR_NUMBER" && -n "$COMMIT_SHA_INPUT" ]]; then
            echo "::error::Provide exactly one of 'pr_number' or 'commit_sha', not both."
            exit 1
          fi
          if [[ -n "$PR_NUMBER" && ! "$PR_NUMBER" =~ ^[0-9]+$ ]]; then
            echo "::error::pr_number must be a positive integer."
            exit 1
          fi

      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Configure Git
        run: |
          git config user.name "sglang-bot"
          git config user.email "sglang-bot@users.noreply.github.com"

      - name: Validate target branch exists
        env:
          TARGET_BRANCH: ${{ github.event.inputs.target_branch }}
        run: |
          git fetch origin
          if ! git ls-remote --exit-code --heads origin "$TARGET_BRANCH" > /dev/null 2>&1; then
            echo "::error::Target branch '$TARGET_BRANCH' does not exist on remote"
            exit 1
          fi

      - name: Resolve PR / commit
        id: resolve
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR_NUMBER: ${{ github.event.inputs.pr_number }}
          COMMIT_SHA_INPUT: ${{ github.event.inputs.commit_sha }}
        run: |
          set -eo pipefail
          shopt -s inherit_errexit

          SOURCE_PR=""
          PR_URL=""

          if [[ -n "$PR_NUMBER" ]]; then
            if ! PR_JSON=$(gh pr view "$PR_NUMBER" --repo "$GITHUB_REPOSITORY" --json state,mergeCommit,title,number,url); then
              echo "::error::Failed to fetch PR #$PR_NUMBER from $GITHUB_REPOSITORY (see gh output above)."
              exit 1
            fi
            STATE=$(jq -r '.state' <<<"$PR_JSON")
            if [[ "$STATE" != "MERGED" ]]; then
              echo "::error::PR #$PR_NUMBER is not merged (state=$STATE). Only merged PRs can be cherry-picked."
              exit 1
            fi
            FULL_SHA=$(jq -r '.mergeCommit.oid // empty' <<<"$PR_JSON")
            if [[ -z "$FULL_SHA" ]]; then
              echo "::error::PR #$PR_NUMBER is marked merged but has no associated merge commit."
              exit 1
            fi
            PR_TITLE=$(jq -r '.title // empty' <<<"$PR_JSON")
            PR_URL=$(jq -r '.url // empty' <<<"$PR_JSON")
            SOURCE_PR="#$PR_NUMBER"
          else
            if ! git cat-file -t "$COMMIT_SHA_INPUT" > /dev/null 2>&1; then
              echo "::error::Commit SHA '$COMMIT_SHA_INPUT' does not exist in the fetched history"
              exit 1
            fi
            FULL_SHA=$(git rev-parse --verify "${COMMIT_SHA_INPUT}^{commit}")
            PR_TITLE=$(git log -1 --format="%s" "$FULL_SHA")

            # Look up the merged PR associated with this commit. Distinguish "API call
            # failed" (abort — could mask an unmerged commit) from "API returned no
            # merged PR" (fall through to ancestry check).
            if ! PR_LOOKUP_RAW=$(gh api -X GET "repos/${GITHUB_REPOSITORY}/commits/${FULL_SHA}/pulls"); then
              echo "::error::Failed to query PRs associated with commit ${FULL_SHA}. Aborting to avoid cherry-picking unverified commits."
              exit 1
            fi
            PR_LOOKUP=$(jq '[.[] | select(.merged_at != null)][0] // empty' <<<"$PR_LOOKUP_RAW")
            if [[ -n "$PR_LOOKUP" ]]; then
              ASSOC_PR_NUM=$(jq -r '.number' <<<"$PR_LOOKUP")
              PR_URL=$(jq -r '.html_url // empty' <<<"$PR_LOOKUP")
              PR_TITLE=$(jq -r '.title // empty' <<<"$PR_LOOKUP")
              SOURCE_PR="#$ASSOC_PR_NUM"
            else
              # No merged PR found for this commit. Require it to at least be reachable
              # from the default branch so we don't cherry-pick unmerged work.
              if ! DEFAULT_BRANCH=$(gh repo view "$GITHUB_REPOSITORY" --json defaultBranchRef --jq '.defaultBranchRef.name'); then
                echo "::error::Could not determine default branch for ${GITHUB_REPOSITORY}."
                exit 1
              fi
              if [[ -z "$DEFAULT_BRANCH" ]]; then
                echo "::error::GitHub API returned an empty default branch for ${GITHUB_REPOSITORY}."
                exit 1
              fi
              if ! git rev-parse --verify "origin/${DEFAULT_BRANCH}" >/dev/null 2>&1; then
                echo "::error::origin/${DEFAULT_BRANCH} is not fetched locally; cannot verify whether ${FULL_SHA} is merged."
                exit 1
              fi
              if ! git merge-base --is-ancestor "$FULL_SHA" "origin/${DEFAULT_BRANCH}"; then
                echo "::error::Commit '$FULL_SHA' has no associated merged PR and is not reachable from origin/${DEFAULT_BRANCH}. Refusing to cherry-pick unmerged commits."
                exit 1
              fi
            fi
          fi

          SHORT_SHA=$(git rev-parse --short "$FULL_SHA")

          # Detect merge commit by counting parents. `git show -s --format=%P` prints
          # parent SHAs separated by spaces; >1 means it's a merge commit.
          PARENTS_LINE=$(git show -s --format=%P "$FULL_SHA")
          PARENT_COUNT=$(wc -w <<<"$PARENTS_LINE" | tr -d ' ')
          IS_MERGE_COMMIT="false"
          if [[ "$PARENT_COUNT" -gt 1 ]]; then
            IS_MERGE_COMMIT="true"
          fi

          echo "full_sha=$FULL_SHA" >> $GITHUB_OUTPUT
          echo "short_sha=$SHORT_SHA" >> $GITHUB_OUTPUT
          echo "is_merge_commit=$IS_MERGE_COMMIT" >> $GITHUB_OUTPUT
          echo "source_pr=$SOURCE_PR" >> $GITHUB_OUTPUT
          echo "pr_url=$PR_URL" >> $GITHUB_OUTPUT
          {
            echo "pr_title<<EOF"
            echo "$PR_TITLE"
            echo "EOF"
          } >> $GITHUB_OUTPUT

          echo "Cherry-picking ${SHORT_SHA} (${SOURCE_PR:-no associated PR}) - ${PR_TITLE}"

      - name: Cherry-pick commit
        id: cherry_pick
        env:
          TARGET_BRANCH: ${{ github.event.inputs.target_branch }}
          FULL_SHA: ${{ steps.resolve.outputs.full_sha }}
          SHORT_SHA: ${{ steps.resolve.outputs.short_sha }}
          IS_MERGE_COMMIT: ${{ steps.resolve.outputs.is_merge_commit }}
        run: |
          RANDOM_SUFFIX=$(head -c 4 /dev/urandom | xxd -p)
          NEW_BRANCH="cherry-pick/${SHORT_SHA}-to-${TARGET_BRANCH#release/}-${RANDOM_SUFFIX}"
          git checkout -b "$NEW_BRANCH" "origin/$TARGET_BRANCH"
          echo "new_branch=$NEW_BRANCH" >> $GITHUB_OUTPUT

          CP_ARGS=()
          if [[ "$IS_MERGE_COMMIT" == "true" ]]; then
            CP_ARGS+=(-m 1)
          fi
          if git cherry-pick "${CP_ARGS[@]}" "$FULL_SHA"; then
            echo "cherry_pick_success=true" >> $GITHUB_OUTPUT
          else
            echo "::error::Cherry-pick of ${FULL_SHA} onto ${TARGET_BRANCH} failed due to conflicts. Resolve locally: 'git checkout ${TARGET_BRANCH} && git cherry-pick ${FULL_SHA}', fix conflicts, push a branch, and open the PR by hand."
            git cherry-pick --abort || echo "::warning::git cherry-pick --abort returned non-zero; ignoring since the job is exiting."
            echo "cherry_pick_success=false" >> $GITHUB_OUTPUT
            exit 1
          fi

      - name: Push branch
        if: steps.cherry_pick.outputs.cherry_pick_success == 'true'
        env:
          NEW_BRANCH: ${{ steps.cherry_pick.outputs.new_branch }}
        run: |
          git push origin "$NEW_BRANCH"

      - name: Create Pull Request
        id: create_pr
        if: steps.cherry_pick.outputs.cherry_pick_success == 'true'
        env:
          GH_TOKEN: ${{ secrets.GH_PAT_FOR_CHERRY_PICK }}
          TARGET_BRANCH: ${{ github.event.inputs.target_branch }}
          SHORT_SHA: ${{ steps.resolve.outputs.short_sha }}
          FULL_SHA: ${{ steps.resolve.outputs.full_sha }}
          PR_TITLE: ${{ steps.resolve.outputs.pr_title }}
          SOURCE_PR: ${{ steps.resolve.outputs.source_pr }}
          PR_URL: ${{ steps.resolve.outputs.pr_url }}
          NEW_BRANCH: ${{ steps.cherry_pick.outputs.new_branch }}
        run: |
          if [[ -n "$SOURCE_PR" ]]; then
            CHERRY_PICK_TITLE="[Cherry-pick to ${TARGET_BRANCH}] ${PR_TITLE} (${SOURCE_PR})"
          else
            CHERRY_PICK_TITLE="[Cherry-pick to ${TARGET_BRANCH}] ${PR_TITLE} (${SHORT_SHA})"
          fi

          BODY="Cherry-pick of commit \`${FULL_SHA}\` to \`${TARGET_BRANCH}\`."$'\n\n'
          if [[ -n "$SOURCE_PR" ]]; then
            BODY+="**Source PR:** ${SOURCE_PR} (${PR_URL})"$'\n'
          fi
          BODY+="**Source commit:** \`${FULL_SHA}\`"$'\n'
          BODY+="**Original title:** ${PR_TITLE}"$'\n\n'
          BODY+="---"$'\n'
          BODY+="*This PR was automatically created by the cherry-pick workflow.*"

          CREATED_PR_URL=$(printf '%s' "$BODY" | gh pr create \
            --title "$CHERRY_PICK_TITLE" \
            --base "$TARGET_BRANCH" \
            --head "$NEW_BRANCH" \
            --label "cherry-pick" \
            --body-file -)
          CREATED_PR_NUMBER="${CREATED_PR_URL##*/}"
          echo "created_pr_url=$CREATED_PR_URL" >> $GITHUB_OUTPUT
          echo "created_pr_number=$CREATED_PR_NUMBER" >> $GITHUB_OUTPUT
          echo "Created cherry-pick PR #${CREATED_PR_NUMBER}: ${CREATED_PR_URL}"

      - name: Summary
        if: always()
        env:
          FULL_SHA: ${{ steps.resolve.outputs.full_sha }}
          PR_TITLE: ${{ steps.resolve.outputs.pr_title }}
          SOURCE_PR: ${{ steps.resolve.outputs.source_pr }}
          TARGET_BRANCH: ${{ github.event.inputs.target_branch }}
          CHERRY_PICK_SUCCESS: ${{ steps.cherry_pick.outputs.cherry_pick_success }}
          NEW_BRANCH: ${{ steps.cherry_pick.outputs.new_branch }}
          CREATED_PR_NUMBER: ${{ steps.create_pr.outputs.created_pr_number }}
          CREATED_PR_URL: ${{ steps.create_pr.outputs.created_pr_url }}
          ACTOR: ${{ github.actor }}
        run: |
          echo "## Cherry-Pick Summary" >> $GITHUB_STEP_SUMMARY
          echo "" >> $GITHUB_STEP_SUMMARY
          echo "- **Triggered by:** @${ACTOR}" >> $GITHUB_STEP_SUMMARY
          if [[ -n "$SOURCE_PR" ]]; then
            echo "- **Source PR:** ${SOURCE_PR}" >> $GITHUB_STEP_SUMMARY
          fi
          echo "- **Source commit:** ${FULL_SHA}" >> $GITHUB_STEP_SUMMARY
          echo "- **Title:** ${PR_TITLE}" >> $GITHUB_STEP_SUMMARY
          echo "- **Target Branch:** ${TARGET_BRANCH}" >> $GITHUB_STEP_SUMMARY
          if [[ "$CHERRY_PICK_SUCCESS" == "true" ]]; then
            echo "- **Status:** Success" >> $GITHUB_STEP_SUMMARY
            echo "- **PR Branch:** ${NEW_BRANCH}" >> $GITHUB_STEP_SUMMARY
            if [[ -n "$CREATED_PR_NUMBER" ]]; then
              echo "- **Cherry-pick PR:** [#${CREATED_PR_NUMBER}](${CREATED_PR_URL})" >> $GITHUB_STEP_SUMMARY
            fi
          else
            echo "- **Status:** Failed" >> $GITHUB_STEP_SUMMARY
          fi