name: Amazon Bedrock PR Summary

on:
pull_request:
types:
- opened
- synchronize
- reopened

permissions:
contents: read
pull-requests: write
id-token: write

jobs:
summarize:
# Do not provide AWS credentials to pull requests from forks.
if: github.event.pull_request.head.repo.full_name == github.repository

runs-on: ubuntu-latest

env:
AWS_REGION: us-east-1
BEDROCK_MODEL_ID: amazon.nova-lite-v1:0
PR_NUMBER: ${{ github.event.pull_request.number }}
GH_TOKEN: ${{ github.token }}

steps:
- name: Configure AWS credentials
uses: aws-actions/configure-aws-credentials@v6
with:
role-to-assume: ${{ vars.AWS_ROLE_ARN }}
aws-region: ${{ env.AWS_REGION }}

- name: Get pull request diff
run: |
gh pr diff "$PR_NUMBER" \
--repo "$GITHUB_REPOSITORY" \
> pr.diff

- name: Install AWS SDK
run: python -m pip install --quiet boto3

- name: Generate AI summary with Amazon Bedrock
run: |
python <<'PY'
import os
from pathlib import Path

import boto3

diff = Path("pr.diff").read_text(
encoding="utf-8",
errors="replace"
)

# Keep the demo reasonably small.
diff = diff[:30000]

prompt = f"""
You are reviewing a software pull request.

Analyze the Git diff below and create a concise technical
summary for another developer.

Structure the response as:

### Overview
Explain what this pull request does.

### Key Changes
Describe the important code changes.

### Reviewer Attention
Mention areas that deserve extra review.

Do not invent changes that are not visible in the diff.

Git Diff:

{diff}
"""

client = boto3.client(
"bedrock-runtime",
region_name=os.environ["AWS_REGION"]
)

response = client.converse(
modelId=os.environ["BEDROCK_MODEL_ID"],
messages=[
{
"role": "user",
"content": [
{
"text": prompt
}
]
}
],
inferenceConfig={
"maxTokens": 700,
"temperature": 0.2
}
)

summary = response[
"output"
][
"message"
][
"content"
][0][
"text"
]

output = f"""## 🤖 Amazon Bedrock PR Summary

{summary}

---
Generated automatically using Amazon Bedrock and GitHub Actions.
"""

Path("summary.md").write_text(
output,
encoding="utf-8"
)
PY

- name: Comment on pull request
run: |
gh pr comment "$PR_NUMBER" \
--repo "$GITHUB_REPOSITORY" \
--body-file summary.md