From d4d2ac5d8f97f39b4ee11876d8df4237057d39b9 Mon Sep 17 00:00:00 2001
From: Vasil Dininski <Vasil.Dininski@digits.schwarz>
Date: Sat, 14 Mar 2026 21:43:56 +0200
Subject: [PATCH] Initial commit

---
 .forgejo/workflows/ai-pr-review.yml | 21 +++++++
 action.yml                          | 69 +++++++++++++++++++++
 prompts/review-update.md            |  9 +++
 prompts/review.md                   | 10 +++
 scripts/fetch-context.sh            | 34 +++++++++++
 scripts/generate-diff.sh            | 26 ++++++++
 scripts/post-comment.sh             | 29 +++++++++
 scripts/run-review.sh               | 95 +++++++++++++++++++++++++++++
 8 files changed, 293 insertions(+)
 create mode 100644 .forgejo/workflows/ai-pr-review.yml
 create mode 100644 action.yml
 create mode 100644 prompts/review-update.md
 create mode 100644 prompts/review.md
 create mode 100644 scripts/fetch-context.sh
 create mode 100644 scripts/generate-diff.sh
 create mode 100644 scripts/post-comment.sh
 create mode 100644 scripts/run-review.sh

diff --git a/.forgejo/workflows/ai-pr-review.yml b/.forgejo/workflows/ai-pr-review.yml
new file mode 100644
index 0000000..e25ae8c
--- /dev/null
+++ b/.forgejo/workflows/ai-pr-review.yml
@@ -0,0 +1,21 @@
+name: AI PR Review
+
+on:
+  pull_request:
+    branches:
+      - main
+    types:
+      - opened
+      - synchronize
+      - reopened
+
+jobs:
+  review:
+    runs-on: js-ubuntu-22
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./
+        with:
+          api_url: ${{ secrets.AI_API_URL }}
+          api_key: ${{ secrets.AI_API_KEY }}
+          # model: openai/gpt-oss-120b  # optional, this is the default
diff --git a/action.yml b/action.yml
new file mode 100644
index 0000000..af0d57a
--- /dev/null
+++ b/action.yml
@@ -0,0 +1,69 @@
+name: AI PR Review
+description: Automated AI-powered PR code review using any OpenAI-compatible endpoint
+
+inputs:
+  api_url:
+    description: Base URL of the OpenAI-compatible API endpoint (e.g. https://api.openai.com/v1)
+    required: true
+  api_key:
+    description: API key for the endpoint
+    required: true
+  model:
+    description: Model identifier to use for the review
+    required: false
+    default: openai/gpt-oss-120b
+  github_token:
+    description: Token used to post the review comment and fetch PR comments
+    required: false
+    default: ${{ github.token }}
+
+runs:
+  using: composite
+  steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+
+    - name: Fetch previous review context
+      id: context
+      shell: bash
+      env:
+        GITEA_TOKEN: ${{ inputs.github_token }}
+        GITEA_SERVER_URL: ${{ github.server_url }}
+        REPO: ${{ github.repository }}
+        PR_NUMBER: ${{ github.event.pull_request.number }}
+      run: bash "${{ github.action_path }}/scripts/fetch-context.sh"
+
+    - name: Generate diff
+      id: diff
+      shell: bash
+      env:
+        PREV_SHA: ${{ steps.context.outputs.prev_sha }}
+      run: bash "${{ github.action_path }}/scripts/generate-diff.sh"
+
+    - name: Run AI review
+      id: ai_review
+      shell: bash
+      env:
+        AI_API_URL: ${{ inputs.api_url }}
+        AI_API_KEY: ${{ inputs.api_key }}
+        AI_MODEL: ${{ inputs.model }}
+        PR_TITLE: ${{ github.event.pull_request.title }}
+        PR_BODY: ${{ github.event.pull_request.body }}
+        PREV_REVIEW: ${{ steps.context.outputs.prev_review }}
+        INCREMENTAL: ${{ steps.diff.outputs.incremental }}
+      run: bash "${{ github.action_path }}/scripts/run-review.sh"
+
+    - name: Post review comment
+      shell: bash
+      env:
+        GITEA_TOKEN: ${{ inputs.github_token }}
+        GITEA_SERVER_URL: ${{ github.server_url }}
+        REPO: ${{ github.repository }}
+        PR_NUMBER: ${{ github.event.pull_request.number }}
+        REVIEW: ${{ steps.ai_review.outputs.review }}
+        CURRENT_SHA: ${{ github.event.pull_request.head.sha }}
+        TRUNCATED: ${{ steps.diff.outputs.truncated }}
+        INCREMENTAL: ${{ steps.diff.outputs.incremental }}
+      run: bash "${{ github.action_path }}/scripts/post-comment.sh"
diff --git a/prompts/review-update.md b/prompts/review-update.md
new file mode 100644
index 0000000..9b33228
--- /dev/null
+++ b/prompts/review-update.md
@@ -0,0 +1,9 @@
+You are an expert code reviewer continuing a review of a pull request that has been updated.
+
+Your previous review is included as context. Focus on:
+- What has changed since your last review
+- Whether previously raised issues have been addressed
+- Any new correctness, security, or performance concerns introduced by the new changes
+- New edge cases or missing tests
+
+Structure your updated review with: **Summary of Changes**, **Resolved Issues** (from your prior review), **New Issues** (critical/minor), and **Suggestions**. Be concise and avoid repeating feedback that is no longer relevant.
diff --git a/prompts/review.md b/prompts/review.md
new file mode 100644
index 0000000..d881afd
--- /dev/null
+++ b/prompts/review.md
@@ -0,0 +1,10 @@
+You are an expert code reviewer. Review the following pull request and provide concise, actionable feedback.
+
+Focus on:
+- Correctness and potential bugs
+- Security issues
+- Performance concerns
+- Code clarity and maintainability
+- Missing tests or edge cases
+
+Structure your review with sections: **Summary**, **Issues** (critical/minor), and **Suggestions**. Be concise.
diff --git a/scripts/fetch-context.sh b/scripts/fetch-context.sh
new file mode 100644
index 0000000..cbe27c8
--- /dev/null
+++ b/scripts/fetch-context.sh
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Fetches the previous AI review comment from the PR (if any).
+# Required env vars: GITEA_TOKEN, GITEA_SERVER_URL, REPO, PR_NUMBER
+# Writes to $GITHUB_OUTPUT: prev_sha, prev_review
+set -euo pipefail
+
+COMMENTS=$(curl -sf \
+  -H "Authorization: token ${GITEA_TOKEN}" \
+  -H "Content-Type: application/json" \
+  "${GITEA_SERVER_URL}/api/v1/repos/${REPO}/issues/${PR_NUMBER}/comments")
+
+# Find the most recent comment that contains our SHA marker
+PREV_COMMENT=$(echo "$COMMENTS" | jq -r '
+  [ .[] | select(.body | contains("<!-- ai-review-sha:")) ] | last | .body // ""
+')
+
+if [ -z "$PREV_COMMENT" ]; then
+  echo "No previous AI review found — will run a full review."
+  echo "prev_sha=" >> "$GITHUB_OUTPUT"
+  echo "prev_review=" >> "$GITHUB_OUTPUT"
+  exit 0
+fi
+
+PREV_SHA=$(echo "$PREV_COMMENT" | grep -oP '(?<=<!-- ai-review-sha:)[^>]+(?= -->)' || true)
+# Strip the trailing marker line to get just the review body
+PREV_REVIEW=$(echo "$PREV_COMMENT" | sed '/<!-- ai-review-sha:/d')
+
+echo "Found previous review at commit ${PREV_SHA}"
+
+echo "prev_sha=${PREV_SHA}" >> "$GITHUB_OUTPUT"
+
+echo "prev_review<<EOF" >> "$GITHUB_OUTPUT"
+echo "$PREV_REVIEW" >> "$GITHUB_OUTPUT"
+echo "EOF" >> "$GITHUB_OUTPUT"
diff --git a/scripts/generate-diff.sh b/scripts/generate-diff.sh
new file mode 100644
index 0000000..21bd781
--- /dev/null
+++ b/scripts/generate-diff.sh
@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Required env vars: (none)
+# Optional env vars: PREV_SHA (if set, generates an incremental diff from that commit)
+set -euo pipefail
+
+git fetch origin main --depth=100
+
+if [ -n "${PREV_SHA:-}" ] && git cat-file -e "${PREV_SHA}^{commit}" 2>/dev/null; then
+  echo "Generating incremental diff from ${PREV_SHA} to HEAD"
+  git diff "${PREV_SHA}...HEAD" > pr.diff
+  echo "incremental=true" >> "$GITHUB_OUTPUT"
+else
+  echo "Generating full diff from origin/main to HEAD"
+  git diff origin/main...HEAD > pr.diff
+  echo "incremental=false" >> "$GITHUB_OUTPUT"
+fi
+
+DIFF_SIZE=$(wc -c < pr.diff)
+echo "Diff size: ${DIFF_SIZE} bytes"
+
+if [ "$DIFF_SIZE" -gt 12288 ]; then
+  head -c 12288 pr.diff > pr_truncated.diff
+  printf '\n\n[... diff truncated due to size ...]' >> pr_truncated.diff
+  mv pr_truncated.diff pr.diff
+  echo "truncated=true" >> "$GITHUB_OUTPUT"
+fi
diff --git a/scripts/post-comment.sh b/scripts/post-comment.sh
new file mode 100644
index 0000000..a3b78ac
--- /dev/null
+++ b/scripts/post-comment.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Required env vars: GITEA_TOKEN, GITEA_SERVER_URL, REPO, PR_NUMBER, REVIEW, CURRENT_SHA
+# Optional env vars: TRUNCATED, INCREMENTAL
+set -euo pipefail
+
+FOOTER=""
+if [ "${TRUNCATED:-}" = "true" ]; then
+  FOOTER="\n\n> **Note:** The diff was truncated to 12 KB. Some changes may not have been reviewed."
+fi
+
+LABEL="## AI Code Review"
+if [ "${INCREMENTAL:-false}" = "true" ]; then
+  LABEL="## AI Code Review (updated)"
+fi
+
+# Embed the current SHA as a hidden marker so future runs can find it
+BODY=$(jq -n \
+  --arg label "$LABEL" \
+  --arg review "$REVIEW" \
+  --arg footer "$FOOTER" \
+  --arg sha "$CURRENT_SHA" \
+  '{ body: ($label + "\n\n" + $review + $footer + "\n\n---\n*Automated review powered by AI. Always verify suggestions before applying.*\n<!-- ai-review-sha:" + $sha + " -->") }')
+
+curl -sf \
+  -X POST \
+  -H "Authorization: token ${GITEA_TOKEN}" \
+  -H "Content-Type: application/json" \
+  -d "$BODY" \
+  "${GITEA_SERVER_URL}/api/v1/repos/${REPO}/issues/${PR_NUMBER}/comments"
diff --git a/scripts/run-review.sh b/scripts/run-review.sh
new file mode 100644
index 0000000..1de061e
--- /dev/null
+++ b/scripts/run-review.sh
@@ -0,0 +1,95 @@
+#!/usr/bin/env bash
+# Required env vars: AI_API_URL, AI_API_KEY, AI_MODEL, PR_TITLE, PR_BODY
+# Optional env vars: PREV_REVIEW, INCREMENTAL
+# Reads: pr.diff, prompts/review.md (or prompts/review-update.md for incremental)
+# Writes: $GITHUB_OUTPUT (review)
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROMPTS_DIR="${SCRIPT_DIR}/../prompts"
+
+DIFF=$(cat pr.diff)
+echo "Diff size: $(wc -c < pr.diff) bytes"
+
+if [ "${INCREMENTAL:-false}" = "true" ] && [ -n "${PREV_REVIEW:-}" ]; then
+  echo "Building incremental review with conversation history"
+  SYSTEM_PROMPT=$(cat "${PROMPTS_DIR}/review-update.md")
+
+  # Reconstruct conversation: the model previously reviewed an earlier state,
+  # now we show it only what changed since then.
+  MESSAGES=$(jq -n \
+    --arg system "$SYSTEM_PROMPT" \
+    --arg prev "$PREV_REVIEW" \
+    --arg title "$PR_TITLE" \
+    --arg body "$PR_BODY" \
+    --arg diff "$DIFF" \
+    '[
+      { role: "system", content: $system },
+      { role: "assistant", content: $prev },
+      { role: "user", content: ("The PR has been updated. Here are the new changes since your last review.\n\nPR Title: " + $title + "\nPR Description: " + $body + "\n\nIncremental diff:\n```diff\n" + $diff + "\n```\n\nUpdate your review, keeping previous feedback relevant to unchanged code and focusing new commentary on what has changed.") }
+    ]')
+else
+  echo "Building full review"
+  SYSTEM_PROMPT=$(cat "${PROMPTS_DIR}/review.md")
+
+  MESSAGES=$(jq -n \
+    --arg system "$SYSTEM_PROMPT" \
+    --arg title "$PR_TITLE" \
+    --arg body "$PR_BODY" \
+    --arg diff "$DIFF" \
+    '[
+      { role: "system", content: $system },
+      { role: "user", content: ("PR Title: " + $title + "\nPR Description: " + $body + "\n\nDiff:\n```diff\n" + $diff + "\n```") }
+    ]')
+fi
+
+PAYLOAD=$(jq -n \
+  --arg model "$AI_MODEL" \
+  --argjson messages "$MESSAGES" \
+  '{
+    model: $model,
+    messages: $messages,
+    max_tokens: 1024,
+    temperature: 0.2
+  }')
+
+echo "Payload size: $(echo "$PAYLOAD" | wc -c) bytes"
+echo "Calling endpoint: ${AI_API_URL%/}/chat/completions"
+echo "Model: ${AI_MODEL}"
+
+HTTP_RESPONSE=$(curl -s \
+  --max-time 120 \
+  -w "\n__HTTP_STATUS__:%{http_code}" \
+  -H "Authorization: Bearer ${AI_API_KEY}" \
+  -H "Content-Type: application/json" \
+  -d "$PAYLOAD" \
+  "${AI_API_URL%/}/chat/completions")
+CURL_EXIT=$?
+
+HTTP_STATUS=$(echo "$HTTP_RESPONSE" | grep '__HTTP_STATUS__:' | cut -d: -f2)
+RESPONSE_BODY=$(echo "$HTTP_RESPONSE" | sed '/__HTTP_STATUS__:/d')
+
+echo "curl exit code: ${CURL_EXIT}"
+echo "HTTP status: ${HTTP_STATUS}"
+echo "Response body: ${RESPONSE_BODY}"
+
+if [ "$CURL_EXIT" -ne 0 ]; then
+  echo "::error::curl failed with exit code ${CURL_EXIT}"
+  exit 1
+fi
+
+if [ "$HTTP_STATUS" -lt 200 ] || [ "$HTTP_STATUS" -ge 300 ]; then
+  echo "::error::API returned HTTP ${HTTP_STATUS}: ${RESPONSE_BODY}"
+  exit 1
+fi
+
+REVIEW=$(echo "$RESPONSE_BODY" | jq -r '.choices[0].message.content')
+if [ -z "$REVIEW" ] || [ "$REVIEW" = "null" ]; then
+  echo "::error::Failed to extract review from response. Full body: ${RESPONSE_BODY}"
+  exit 1
+fi
+
+echo "Review length: $(echo "$REVIEW" | wc -c) chars"
+echo "review<<EOF" >> "$GITHUB_OUTPUT"
+echo "$REVIEW" >> "$GITHUB_OUTPUT"
+echo "EOF" >> "$GITHUB_OUTPUT"