Implement OAuth authentication and admin panel

- Introduced OAuth-based login flow with session management and CSRF protection.
- Added admin panel for managing events and gallery content with real-time editing functionality.
- Integrated Gitea API for saving files and updating repository content.
- Updated `.env.example` to include OAuth and Gitea-related configurations.
- Added example event and gallery JSON files for demonstration.

.env.example

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+# Copy this file to .env.local for local development
+# Then run: npm run dev:local
+
+# Public base URL for your local dev server
+PUBLIC_BASE_URL=http://localhost:4321
+
+# OAuth (Gitea) settings for local development
+# Create an OAuth2 Application in your Gitea with Redirect URI:
+#   http://localhost:4321/api/auth/callback
+# Then paste the resulting Client ID/Secret below
+OAUTH_PROVIDER=gitea
+OAUTH_CLIENT_ID=
+OAUTH_CLIENT_SECRET=
+OAUTH_AUTHORIZE_URL=https://git.bookageek.ch/login/oauth/authorize
+OAUTH_TOKEN_URL=https://git.bookageek.ch/login/oauth/access_token
+OAUTH_USERINFO_URL=https://git.bookageek.ch/api/v1/user
+
+# Optional access control
+# OAUTH_ALLOWED_USERS=user1,user2
+# OAUTH_ALLOWED_ORG=your-org
+
+# Gitea API for committing content changes (service account PAT)
+GITEA_BASE=https://git.bookageek.ch
+GITEA_OWNER=
+GITEA_REPO=
+GITEA_TOKEN=
+GIT_BRANCH=main
+
+# Session and CSRF secrets (use random long strings in .env.local)
+SESSION_SECRET=
+CSRF_SECRET=

src/content/events.json

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+[
+  {
+    "image": "/images/karaoke.jpg",
+    "title": "Karaoke",
+    "date": "Mittwoch - Samstag",
+    "description": "Bei uns gibt es Karaoke Mi-Sa!! <br>\nSeid ihr eine Gruppe und lieber unter euch? ..unseren 2.Stock kannst du auch mieten ;) <br>\nReserviere am besten gleich per Whatsapp <a href=\"tel:+41772322770\">077 232 27 70</a>"
+  },
+  {
+    "image": "/images/pub_quiz.jpg",
+    "title": "Pub Quiz",
+    "date": "Jeden Freitag",
+    "description": "Jeden Freitag findet unser <b>Pub Quiz</b> statt. Gespielt wird tischweise in 3-4 Runden. <br>\nJede Woche gibt es ein anderes Thema. Es geht um Ruhm und Ehre und zusätzlich werden die Sieger der Herzen durch das Publikum gekürt! <3 <br>\nAuch Einzelpersonen sind herzlich willkommen! <br>\n*zum mitmachen minimum 1 Getränk konsumieren oder 5CHF"
+  },
+  {
+    "image": "/images/crepes_sucette.jpg",
+    "title": "Crepes Sucette <br /> Live Music im Gallus Pub!",
+    "date": "Do, 04. September 2025",
+    "description": "<b>20:00 Uhr</b> <br>\n<a href=\"Metzgergasse 13, 9000 St. Gallen\">Metzgergasse 13, 9000 St. Gallen</a> <br>\nErlebt einen musikalischen Abend mit der Band <b>Crepes Sucette</b> <br>\nJetzt reservieren: <a href=\"tel:+41772322770\">077 232 27 70</a>"
+  },
+  {
+    "image": "/images/kevin_mcflannigan.jpeg",
+    "title": "Kevin McFlannigan <br> Live Music im Gallus Pub!",
+    "date": "Sa, 27. September 2025",
+    "description": "<b>ab 20:00 Uhr</b> <br>\nSinger & Songwriter Kevin McFlannigan <br>\nEintritt ist Frei / Hutkollekte <br>"
+  }
+]

src/content/gallery.json

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+[
+  { "src": "/images/Logo.png", "alt": "Erstes Bild" },
+  { "src": "/images/Logo.png", "alt": "Zweites Bild" },
+  { "src": "/images/Logo.png", "alt": "Drittes Bild" },
+  { "src": "/images/Logo.png", "alt": "Viertes Bild" },
+  { "src": "/images/Logo.png", "alt": "Fünftes Bild" },
+  { "src": "/images/Logo.png", "alt": "Sechstes Bild" },
+  { "src": "/images/Logo.png", "alt": "Siebtes Bild" },
+  { "src": "/images/Logo.png", "alt": "Achtes Bild" },
+  { "src": "/images/Logo.png", "alt": "Neuntes Bild" },
+  { "src": "/images/Logo.png", "alt": "Zehntes Bild" }
+]

src/pages/admin/index.astro

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+---
+import Layout from "../../components/Layout.astro";
+import eventsData from "../../content/events.json";
+import imagesData from "../../content/gallery.json";
+import { getSessionFromRequest } from "../../utils/session";
+
+const session = getSessionFromRequest(Astro.request);
+if (!session?.user) {
+  // Not logged in: redirect to OAuth login
+  return Astro.redirect("/api/auth/login");
+}
+const csrf = session.csrf;
+const events = eventsData;
+const images = imagesData;
+---
+
+<Layout>
+  <section>
+    <h1>Admin</h1>
+    <p>Eingeloggt als {session.user.login}</p>
+    <form id="editor">
+      <h2>Events (JSON)</h2>
+      <textarea id="events" name="events" rows="16" style="width:100%;font-family:monospace;">{JSON.stringify(events, null, 2)}</textarea>
+
+      <h2>Galerie (JSON)</h2>
+      <textarea id="images" name="images" rows="10" style="width:100%;font-family:monospace;">{JSON.stringify(images, null, 2)}</textarea>
+
+      <h2>Bilder hochladen</h2>
+      <input type="file" id="fileInput" multiple accept="image/*" />
+
+      <div style="margin-top:1rem;display:flex;gap:.5rem;">
+        <button id="saveBtn" type="button">Speichern</button>
+        <button id="logoutBtn" type="button">Logout</button>
+      </div>
+    </form>
+  </section>
+
+  <meta name="csrf" content={csrf} />
+  <script type="module">
+    const csrf = document.querySelector('meta[name="csrf"]').content;
+
+    async function uploadFiles(files){
+      const uploads = [];
+      for (const file of files){
+        const arrayBuffer = await file.arrayBuffer();
+        const base64 = btoa(String.fromCharCode(...new Uint8Array(arrayBuffer)));
+        uploads.push({ path: `public/images/${file.name}`, content: base64 });
+      }
+      return uploads;
+    }
+
+    async function save(){
+      let events, images;
+      try{
+        events = JSON.parse(document.getElementById('events').value);
+        images = JSON.parse(document.getElementById('images').value);
+      }catch(e){
+        alert('JSON fehlerhaft: ' + e.message);
+        return;
+      }
+
+      const files = [
+        { path: 'src/content/events.json', content: JSON.stringify(events, null, 2) },
+        { path: 'src/content/gallery.json', content: JSON.stringify(images, null, 2) },
+      ];
+
+      const input = document.getElementById('fileInput');
+      if (input.files && input.files.length){
+        const imageFiles = await uploadFiles(input.files);
+        files.push(...imageFiles);
+      }
+
+      const res = await fetch('/api/save', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json', 'X-CSRF': csrf },
+        body: JSON.stringify({ files, message: 'Admin-Inhalte aktualisiert' })
+      });
+      if (!res.ok){
+        const t = await res.text();
+        alert('Fehler beim Speichern: ' + t);
+        return;
+      }
+      alert('Gespeichert! Build wird gestartet.');
+      // optional: Seite neu laden
+      location.reload();
+    }
+
+    document.getElementById('saveBtn').addEventListener('click', save);
+    document.getElementById('logoutBtn').addEventListener('click', async () => {
+      await fetch('/api/auth/logout', { method: 'POST' });
+      location.href = '/';
+    });
+  </script>
+</Layout>

src/pages/api/auth/callback.ts

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+import type { APIRoute } from "astro";
+import { createSessionCookie, sessionCookieHeader, randomToken } from "../../../utils/session";
+
+export const GET: APIRoute = async ({ request }) => {
+  const url = new URL(request.url);
+  const code = url.searchParams.get("code");
+  const state = url.searchParams.get("state");
+  const cookie = request.headers.get("cookie") || "";
+  const stateCookie = cookie.match(/(?:^|; )oauth_state=([^;]+)/)?.[1];
+
+  if (!code || !state || !stateCookie || stateCookie !== state) {
+    return new Response("Invalid OAuth state", { status: 400 });
+  }
+
+  const clientId = process.env.OAUTH_CLIENT_ID;
+  const clientSecret = process.env.OAUTH_CLIENT_SECRET;
+  const tokenUrlRaw = process.env.OAUTH_TOKEN_URL;
+  const userinfoUrl = process.env.OAUTH_USERINFO_URL;
+  if (!clientId || !clientSecret || !tokenUrlRaw || !userinfoUrl) {
+    return new Response("OAuth not fully configured. Please set OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, OAUTH_TOKEN_URL, OAUTH_USERINFO_URL.", { status: 500 });
+  }
+
+  // Compute redirect_uri consistent with login, robust against invalid PUBLIC_BASE_URL
+  let redirectUri: string;
+  try {
+    if (process.env.PUBLIC_BASE_URL) {
+      const base = new URL(process.env.PUBLIC_BASE_URL);
+      redirectUri = new URL("/api/auth/callback", base).toString();
+    } else {
+      const reqUrl = new URL(request.url);
+      redirectUri = new URL("/api/auth/callback", `${reqUrl.protocol}//${reqUrl.host}`).toString();
+    }
+  } catch {
+    const reqUrl = new URL(request.url);
+    redirectUri = new URL("/api/auth/callback", `${reqUrl.protocol}//${reqUrl.host}`).toString();
+  }
+
+  // Validate token URL
+  let tokenUrl: URL;
+  try {
+    tokenUrl = new URL(tokenUrlRaw);
+  } catch {
+    return new Response("Invalid OAUTH_TOKEN_URL", { status: 500 });
+  }
+
+  // Exchange code for token
+  const params = new URLSearchParams();
+  params.set("client_id", clientId);
+  params.set("client_secret", clientSecret);
+  params.set("code", code);
+  params.set("grant_type", "authorization_code");
+  params.set("redirect_uri", redirectUri);
+
+  const tokenRes = await fetch(tokenUrl, {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body: params.toString(),
+  });
+
+  if (!tokenRes.ok) {
+    const t = await tokenRes.text();
+    return new Response(`OAuth token error: ${tokenRes.status} ${t}`, { status: 500 });
+  }
+
+  const tokenData = await tokenRes.json().catch(async () => {
+    // Some Gitea versions return application/x-www-form-urlencoded
+    const text = await tokenRes.text();
+    const usp = new URLSearchParams(text);
+    return Object.fromEntries(usp.entries());
+  });
+  const accessToken = tokenData.access_token || tokenData["access_token"];
+  if (!accessToken) {
+    return new Response("No access token", { status: 500 });
+  }
+
+  const userRes = await fetch(userinfoUrl, {
+    headers: { Authorization: `token ${accessToken}` },
+  });
+  if (!userRes.ok) {
+    const t = await userRes.text();
+    return new Response(`Userinfo error: ${userRes.status} ${t}`, { status: 500 });
+  }
+  const user = await userRes.json();
+
+  // Optional allowlist
+  const allowedUsers = (process.env.OAUTH_ALLOWED_USERS || "").split(/[\,\s]+/).filter(Boolean);
+  const allowedOrg = process.env.OAUTH_ALLOWED_ORG;
+  if (allowedUsers.length && !allowedUsers.includes(user.login)) {
+    return new Response("Forbidden", { status: 403 });
+  }
+  if (allowedOrg) {
+    // Best-effort org check
+    try {
+      const orgsRes = await fetch(process.env.GITEA_BASE + "/api/v1/user/orgs", {
+        headers: { Authorization: `token ${accessToken}` },
+      });
+      if (orgsRes.ok) {
+        const orgs = await orgsRes.json();
+        const inOrg = Array.isArray(orgs) && orgs.some((o: any) => o.username === allowedOrg || o.login === allowedOrg || o.name === allowedOrg);
+        if (!inOrg) return new Response("Forbidden (org)", { status: 403 });
+      }
+    } catch {}
+  }
+
+  const csrf = randomToken(16);
+  const sessionValue = createSessionCookie({
+    user: { id: user.id, login: user.login, name: user.full_name || user.username || user.login, email: user.email },
+    csrf,
+  });
+
+  const headers = new Headers();
+  headers.set("Set-Cookie", sessionCookieHeader(sessionValue));
+  headers.append("Set-Cookie", "oauth_state=; Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=0");
+  headers.set("Location", "/admin");
+  return new Response(null, { status: 302, headers });
+};

src/pages/api/auth/login.ts

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+import type { APIRoute } from "astro";
+import { randomToken, setTempCookie } from "../../../utils/session";
+
+export const GET: APIRoute = async ({ request }) => {
+  const clientId = process.env.OAUTH_CLIENT_ID;
+  const authorizeUrlRaw = process.env.OAUTH_AUTHORIZE_URL;
+  if (!clientId || !authorizeUrlRaw) {
+    return new Response(
+      "OAuth not configured. Please set OAUTH_CLIENT_ID and OAUTH_AUTHORIZE_URL (and related secrets) for local dev.",
+      { status: 500 }
+    );
+  }
+
+  // Determine callback URL
+  let finalRedirect: string;
+  try {
+    if (process.env.PUBLIC_BASE_URL) {
+      // Ensure PUBLIC_BASE_URL is an absolute URL
+      const base = new URL(process.env.PUBLIC_BASE_URL);
+      finalRedirect = new URL("/api/auth/callback", base).toString();
+    } else {
+      // Fallback to current request origin
+      const reqUrl = new URL(request.url);
+      finalRedirect = new URL("/api/auth/callback", `${reqUrl.protocol}//${reqUrl.host}`).toString();
+    }
+  } catch {
+    // As a last resort, use request URL
+    const reqUrl = new URL(request.url);
+    finalRedirect = new URL("/api/auth/callback", `${reqUrl.protocol}//${reqUrl.host}`).toString();
+  }
+
+  // Validate authorize URL
+  let authorizeUrl: URL;
+  try {
+    authorizeUrl = new URL(authorizeUrlRaw);
+  } catch {
+    return new Response("Invalid OAUTH_AUTHORIZE_URL", { status: 500 });
+  }
+
+  const state = randomToken(16);
+  authorizeUrl.searchParams.set("client_id", clientId);
+  authorizeUrl.searchParams.set("redirect_uri", finalRedirect);
+  authorizeUrl.searchParams.set("response_type", "code");
+  authorizeUrl.searchParams.set("state", state);
+
+  return new Response(null, {
+    status: 302,
+    headers: {
+      Location: authorizeUrl.toString(),
+      "Set-Cookie": setTempCookie("oauth_state", state),
+    },
+  });
+};

src/pages/api/auth/logout.ts

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+import type { APIRoute } from "astro";
+import { clearCookieHeader } from "../../../utils/session";
+
+export const POST: APIRoute = async () => {
+  return new Response(null, {
+    status: 204,
+    headers: {
+      "Set-Cookie": clearCookieHeader(),
+    },
+  });
+};

src/pages/api/save.ts

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+import type { APIRoute } from "astro";
+import { getSessionFromRequest } from "../../utils/session";
+
+const GITEA_BASE = process.env.GITEA_BASE!;
+const GITEA_OWNER = process.env.GITEA_OWNER!;
+const GITEA_REPO = process.env.GITEA_REPO!;
+const GITEA_TOKEN = process.env.GITEA_TOKEN!;
+const DEFAULT_BRANCH = process.env.GIT_BRANCH || "main";
+
+function isAllowedPath(path: string) {
+  if (path === "src/content/events.json") return true;
+  if (path === "src/content/gallery.json") return true;
+  if (path.startsWith("public/images/")) {
+    return /\.(png|jpg|jpeg|gif|webp|svg)$/i.test(path);
+  }
+  return false;
+}
+
+async function getShaIfExists(path: string): Promise<string | undefined> {
+  const url = `${GITEA_BASE}/api/v1/repos/${encodeURIComponent(GITEA_OWNER)}/${encodeURIComponent(GITEA_REPO)}/contents/${encodeURIComponent(path)}?ref=${encodeURIComponent(DEFAULT_BRANCH)}`;
+  const res = await fetch(url, {
+    headers: { Authorization: `token ${GITEA_TOKEN}` },
+  });
+  if (res.status === 404) return undefined;
+  if (!res.ok) throw new Error(`Gitea get sha error ${res.status}`);
+  const data = await res.json();
+  return data.sha;
+}
+
+export const POST: APIRoute = async ({ request }) => {
+  const session = getSessionFromRequest(request);
+  if (!session?.user) return new Response(JSON.stringify({ error: "unauthorized" }), { status: 401 });
+
+  // CSRF header required
+  const csrfHeader = request.headers.get("x-csrf") || request.headers.get("X-CSRF");
+  if (!csrfHeader || csrfHeader !== session.csrf) {
+    return new Response(JSON.stringify({ error: "invalid csrf" }), { status: 403 });
+  }
+
+  let payload: any;
+  try {
+    payload = await request.json();
+  } catch {
+    return new Response(JSON.stringify({ error: "invalid json" }), { status: 400 });
+  }
+  if (!payload || !Array.isArray(payload.files)) {
+    return new Response(JSON.stringify({ error: "missing files" }), { status: 400 });
+  }
+
+  const results: any[] = [];
+  for (const file of payload.files) {
+    const path = String(file.path || "");
+    if (!isAllowedPath(path)) {
+      return new Response(JSON.stringify({ error: `path not allowed: ${path}` }), { status: 400 });
+    }
+    let contentBase64: string;
+    if (path.startsWith("public/images/")) {
+      // Expect already base64 string of binary
+      contentBase64 = String(file.content || "");
+      // Remove possible data URL prefix
+      const match = contentBase64.match(/^data:[^;]+;base64,(.*)$/);
+      if (match) contentBase64 = match[1];
+    } else {
+      // Text file
+      contentBase64 = Buffer.from(String(file.content ?? ""), "utf-8").toString("base64");
+    }
+
+    const sha = await getShaIfExists(path).catch(() => undefined);
+    const url = `${GITEA_BASE}/api/v1/repos/${encodeURIComponent(GITEA_OWNER)}/${encodeURIComponent(GITEA_REPO)}/contents/${encodeURIComponent(path)}`;
+    const body: any = {
+      content: contentBase64,
+      message: payload.message || `Update ${path}`,
+      branch: DEFAULT_BRANCH,
+    };
+    if (sha) body.sha = sha;
+    if (session.user) {
+      body.author = { name: session.user.name || session.user.login, email: session.user.email || `${session.user.login}@users.noreply` };
+      body.committer = { name: session.user.name || session.user.login, email: session.user.email || `${session.user.login}@users.noreply` };
+    }
+
+    const res = await fetch(url, {
+      method: "PUT",
+      headers: {
+        Authorization: `token ${GITEA_TOKEN}`,
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify(body),
+    });
+    if (!res.ok) {
+      const t = await res.text();
+      return new Response(JSON.stringify({ error: `Gitea error for ${path}: ${res.status} ${t}` }), { status: 500 });
+    }
+    results.push(await res.json());
+  }
+
+  return new Response(JSON.stringify({ ok: true, results }), { status: 200, headers: { "Content-Type": "application/json" } });
+};

src/utils/session.ts

@@ -0,0 +1,74 @@
+import crypto from "node:crypto";
+
+export type SessionData = {
+  user?: {
+    id: number;
+    login: string;
+    name?: string;
+    email?: string;
+  };
+  csrf?: string;
+};
+
+const COOKIE_NAME = "gp_session";
+
+function b64url(input: Buffer | string) {
+  return Buffer.from(input)
+    .toString("base64")
+    .replace(/=/g, "")
+    .replace(/\+/g, "-")
+    .replace(/\//g, "_");
+}
+
+function sign(payload: string, secret: string) {
+  return crypto.createHmac("sha256", secret).update(payload).digest("base64url");
+}
+
+export function createSessionCookie(data: SessionData, secret = process.env.SESSION_SECRET || "") {
+  const payload = b64url(JSON.stringify(data));
+  const sig = sign(payload, secret);
+  return `${payload}.${sig}`;
+}
+
+export function parseSessionCookie(cookieValue: string | undefined, secret = process.env.SESSION_SECRET || ""): SessionData | undefined {
+  if (!cookieValue) return undefined;
+  const [payload, sig] = cookieValue.split(".");
+  if (!payload || !sig) return undefined;
+  const expected = sign(payload, secret);
+  if (!crypto.timingSafeEqual(Buffer.from(sig), Buffer.from(expected))) return undefined;
+  try {
+    const json = Buffer.from(payload.replace(/-/g, "+").replace(/_/g, "/"), "base64").toString("utf-8");
+    return JSON.parse(json);
+  } catch {
+    return undefined;
+  }
+}
+
+export function clearCookieHeader(name = COOKIE_NAME) {
+  return `${name}=; Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=0`;
+}
+
+export function sessionCookieHeader(value: string, name = COOKIE_NAME) {
+  // 7 days
+  const maxAge = 60 * 60 * 24 * 7;
+  return `${name}=${value}; Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=${maxAge}`;
+}
+
+export function getSessionFromRequest(req: Request, secret = process.env.SESSION_SECRET || ""): SessionData | undefined {
+  const cookie = req.headers.get("cookie") || "";
+  const match = cookie.match(/(?:^|; )gp_session=([^;]+)/);
+  if (!match) return undefined;
+  return parseSessionCookie(match[1], secret);
+}
+
+export function randomToken(bytes = 32) {
+  return crypto.randomBytes(bytes).toString("hex");
+}
+
+export const COOKIE_NAME_STATE = "oauth_state";
+
+export function setTempCookie(name: string, value: string) {
+  // short lived: 10 minutes
+  const maxAge = 60 * 10;
+  return `${name}=${value}; Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=${maxAge}`;
+}