fix: resolve PR number from event payload for Gitea Actions

Gitea Actions mirrors GitHub Actions env vars and does not expose a flat
GITEA_EVENT_PULL_REQUEST_NUMBER. Parse the PR number out of
$GITHUB_EVENT_PATH, key platform detection on $GITEA_ACTIONS, and use
the correct Accept header for GitHub's diff endpoint.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/review.sh

@@ -78,20 +78,39 @@ echo "Generate diff"
 # Instead, we get the diff directly from the Gitea/GitHub API using the token
 # we already have for posting comments.
 
-# Detect platform and resolve PR info
-if [ -n "${GITEA_SERVER_URL:-}" ]; then
-  API_BASE="${GITEA_SERVER_URL}/api/v1"
-  PR_NUMBER="${GITEA_EVENT_PULL_REQUEST_NUMBER:-}"
-  REPO="${GITEA_REPOSITORY:-}"
-  echo "Platform: Gitea (${GITEA_SERVER_URL})"
+# Gitea Actions mirrors GitHub Actions env vars ($GITHUB_*) and exposes the
+# event payload at $GITHUB_EVENT_PATH. There is no flat $GITEA_EVENT_*
+# variable for the PR number, so we parse it out of the event JSON.
+
+REPO="${GITHUB_REPOSITORY:-${GITEA_REPOSITORY:-}}"
+
+# Detect Gitea vs GitHub. Gitea sets $GITHUB_SERVER_URL too, so the only
+# reliable signal is $GITEA_ACTIONS (or a non-github.com server URL).
+SERVER_URL="${GITHUB_SERVER_URL:-${GITEA_SERVER_URL:-}}"
+if [ -n "${GITEA_ACTIONS:-}" ] || { [ -n "$SERVER_URL" ] && [ "${SERVER_URL#*github.com}" = "$SERVER_URL" ]; }; then
+  API_BASE="${SERVER_URL}/api/v1"
+  PLATFORM="gitea"
+  echo "Platform: Gitea (${SERVER_URL})"
 else
   API_BASE="${GITHUB_API_URL:-https://api.github.com}"
-  PR_NUMBER="${GITHUB_EVENT_PULL_REQUEST_NUMBER:-}"
-  REPO="${GITHUB_REPOSITORY:-}"
+  PLATFORM="github"
   echo "Platform: GitHub"
 fi
 
+# Resolve PR number from the event payload.
+PR_NUMBER=""
+if [ -n "${GITHUB_EVENT_PATH:-}" ] && [ -f "${GITHUB_EVENT_PATH}" ]; then
+  PR_NUMBER=$(node -e "
+    try {
+      const e = require(process.env.GITHUB_EVENT_PATH);
+      const n = (e.pull_request && e.pull_request.number) || e.number || '';
+      process.stdout.write(String(n || ''));
+    } catch { process.stdout.write(''); }
+  ")
+fi
+
 echo "Repo: ${REPO}, PR: ${PR_NUMBER}"
+echo "DEBUG: PLATFORM=${PLATFORM} API_BASE=${API_BASE} EVENT=${GITHUB_EVENT_PATH:-}"
 
 if [ -z "$PR_NUMBER" ]; then
   echo "Not a pull request event. Skipping review."
@@ -109,55 +128,45 @@ const apiBase = '${API_BASE}';
 const repo = '${REPO}';
 const prNumber = '${PR_NUMBER}';
 const token = '${PI_TOKEN}';
+const platform = '${PLATFORM}';
 const maxBytes = ${PI_MAX_DIFF:-80000};
 
 function fetchDiff() {
   return new Promise((resolve, reject) => {
-    // Try Gitea diff endpoint first
-    const giteaPath = '/repos/' + repo + '/pulls/' + prNumber + '.diff';
-    const githubPath = '/repos/' + repo + '/pulls/' + prNumber;
+    // Gitea:  GET {api}/repos/{owner}/{repo}/pulls/{n}.diff
+    // GitHub: GET {api}/repos/{owner}/{repo}/pulls/{n} with Accept: application/vnd.github.v3.diff
+    const path = platform === 'gitea'
+      ? '/repos/' + repo + '/pulls/' + prNumber + '.diff'
+      : '/repos/' + repo + '/pulls/' + prNumber;
 
-    const url = new URL(apiBase + giteaPath);
+    const url = new URL(apiBase + path);
     const transport = url.protocol === 'http:' ? http : https;
 
+    const headers = {
+      'Authorization': 'token ' + token,
+      'User-Agent': 'pi-code-review',
+      'Accept': platform === 'gitea' ? 'text/plain' : 'application/vnd.github.v3.diff',
+    };
+
     const options = {
       hostname: url.hostname,
       port: url.port || (url.protocol === 'http:' ? 80 : 443),
       path: url.pathname,
       method: 'GET',
-      headers: {
-        'Authorization': 'token ' + token,
-        'Accept': 'text/plain',
-      },
+      headers,
     };
 
     const req = transport.request(options, (res) => {
-      if (res.statusCode === 404 && apiBase.indexOf('github.com') !== -1) {
-        // Fallback to GitHub diff format
-        reject(new Error('GitHub fallback not implemented'));
-        return;
-      }
       if (res.statusCode < 200 || res.statusCode >= 300) {
         let body = '';
         res.on('data', (c) => { body += c; });
-        res.on('end', () => { reject(new Error('API ' + res.statusCode + ': ' + body.slice(0, 200))); });
+        res.on('end', () => { reject(new Error('API ' + res.statusCode + ' for ' + url.href + ': ' + body.slice(0, 200))); });
         return;
       }
 
       let data = '';
-      let bytes = 0;
-      res.on('data', (chunk) => {
-        bytes += chunk.length;
-        if (maxBytes > 0 && bytes <= maxBytes) {
-          data += chunk;
-        }
-      });
-      res.on('end', () => {
-        if (maxBytes > 0 && data.length >= maxBytes) {
-          data = data.slice(0, maxBytes) + '\\n... (truncated at ' + maxBytes + ' bytes)';
-        }
-        resolve(data);
-      });
+      res.on('data', (chunk) => { data += chunk; });
+      res.on('end', () => { resolve(data); });
     });
     req.on('error', (e) => { reject(e); });
     req.end();
@@ -302,17 +311,7 @@ echo "::endgroup::"
 # ─── Phase 4: Post comment ────────────────────────────────────────────────────
 echo "::group::Post review comment"
 
-# Detect Gitea vs GitHub
-if [ -n "${GITEA_SERVER_URL:-}" ]; then
-  API_BASE="${GITEA_SERVER_URL}/api/v1"
-  PR_NUMBER="${GITEA_EVENT_PULL_REQUEST_NUMBER:-}"
-  REPO="${GITEA_REPOSITORY:-}"
-else
-  API_BASE="${GITHUB_API_URL:-https://api.github.com}"
-  PR_NUMBER="${GITHUB_EVENT_PULL_REQUEST_NUMBER:-}"
-  REPO="${GITHUB_REPOSITORY:-}"
-fi
-
+# API_BASE / REPO / PR_NUMBER were resolved in Phase 2.
 if [ -z "$PR_NUMBER" ]; then
   echo "Not a pull request event. Review written to /tmp/pi-review.md only."
   echo "::endgroup::"