feat: support reverse proxy path prefix deployments (#257)

* feat: support reverse proxy path prefixes

* fix: respect BASE_URL in SAML callback fallback

* fix: make BASE_URL runtime configurable

src/lib/api.ts

@@ -1,5 +1,7 @@
+import { withBase } from "@/lib/base-path";
+
 // Base API URL
-const API_BASE = "/api";
+const API_BASE = withBase("/api");
 
 // Helper function for API requests
 async function apiRequest<T>(

src/lib/auth-client.ts

@@ -3,6 +3,12 @@ import { createAuthClient } from "better-auth/react";
 import { oidcClient } from "better-auth/client/plugins";
 import { ssoClient } from "@better-auth/sso/client";
 import type { Session as BetterAuthSession, User as BetterAuthUser } from "better-auth";
+import { withBase } from "@/lib/base-path";
+
+function normalizeAuthBaseUrl(url: string): string {
+  const validatedUrl = new URL(url.trim());
+  return validatedUrl.origin;
+}
 
 export const authClient = createAuthClient({
   // Use PUBLIC_BETTER_AUTH_URL if set (for multi-origin access), otherwise use current origin
@@ -18,9 +24,8 @@ export const authClient = createAuthClient({
     // Validate and clean the URL if provided
     if (url && typeof url === 'string' && url.trim() !== '') {
       try {
-        // Validate URL format and remove trailing slash
-        const validatedUrl = new URL(url.trim());
-        return validatedUrl.origin; // Use origin to ensure clean URL without path
+        // Validate URL format and preserve optional base path
+        return normalizeAuthBaseUrl(url);
       } catch (e) {
         console.warn(`Invalid PUBLIC_BETTER_AUTH_URL: ${url}, falling back to default`);
       }
@@ -34,7 +39,7 @@ export const authClient = createAuthClient({
     // Default for SSR - always return a valid URL
     return 'http://localhost:4321';
   })(),
-  basePath: '/api/auth', // Explicitly set the base path
+  basePath: withBase('/api/auth'), // Explicitly set the base path
   plugins: [
     oidcClient(),
     ssoClient(),

src/lib/auth.ts

@@ -5,6 +5,7 @@ import { sso } from "@better-auth/sso";
 import { db, users } from "./db";
 import * as schema from "./db/schema";
 import { eq } from "drizzle-orm";
+import { withBase } from "./base-path";
 
 /**
  * Resolves the list of trusted origins for Better Auth CSRF validation.
@@ -97,7 +98,7 @@ export const auth = betterAuth({
     try {
       // Validate URL format and ensure it's a proper origin
       const validatedUrl = new URL(url.trim());
-      const cleanUrl = validatedUrl.origin; // Use origin to ensure no trailing paths
+      const cleanUrl = validatedUrl.origin;
       console.info('Using BETTER_AUTH_URL:', cleanUrl);
       return cleanUrl;
     } catch (e) {
@@ -107,7 +108,7 @@ export const auth = betterAuth({
       return defaultUrl;
     }
   })(),
-  basePath: "/api/auth", // Specify the base path for auth endpoints
+  basePath: withBase("/api/auth"), // Specify the base path for auth endpoints
   
   // Trusted origins - this is how we support multiple access URLs.
   // Uses the function form so that the origin can be auto-detected from
@@ -150,8 +151,8 @@ export const auth = betterAuth({
   plugins: [
     // OIDC Provider plugin - allows this app to act as an OIDC provider
     oidcProvider({
-      loginPage: "/login",
-      consentPage: "/oauth/consent",
+      loginPage: withBase("/login"),
+      consentPage: withBase("/oauth/consent"),
       // Allow dynamic client registration for flexibility
       allowDynamicClientRegistration: true,
       // Note: trustedClients would be configured here if Better Auth supports it

src/lib/base-path.test.ts

@@ -0,0 +1,86 @@
+import { afterEach, describe, expect, test } from "bun:test";
+
+const originalBaseUrl = process.env.BASE_URL;
+const originalWindow = (globalThis as { window?: unknown }).window;
+
+async function loadModule(baseUrl?: string, runtimeWindowBasePath?: string) {
+  if (baseUrl === undefined) {
+    delete process.env.BASE_URL;
+  } else {
+    process.env.BASE_URL = baseUrl;
+  }
+
+  if (runtimeWindowBasePath === undefined) {
+    if (originalWindow === undefined) {
+      delete (globalThis as { window?: unknown }).window;
+    } else {
+      (globalThis as { window?: unknown }).window = originalWindow;
+      const restoredWindow = (globalThis as { window?: { __GITEA_MIRROR_BASE_PATH__?: string } }).window;
+      if (typeof restoredWindow === "object" && restoredWindow !== null) {
+        delete restoredWindow.__GITEA_MIRROR_BASE_PATH__;
+      }
+    }
+  } else {
+    (globalThis as { window?: { __GITEA_MIRROR_BASE_PATH__?: string } }).window = {
+      __GITEA_MIRROR_BASE_PATH__: runtimeWindowBasePath,
+    };
+  }
+
+  return import(`./base-path.ts?case=${encodeURIComponent(baseUrl ?? "default")}-${Date.now()}-${Math.random()}`);
+}
+
+afterEach(() => {
+  if (originalBaseUrl === undefined) {
+    delete process.env.BASE_URL;
+  } else {
+    process.env.BASE_URL = originalBaseUrl;
+  }
+
+  if (originalWindow === undefined) {
+    delete (globalThis as { window?: unknown }).window;
+  } else {
+    (globalThis as { window?: unknown }).window = originalWindow;
+  }
+});
+
+describe("base-path helpers", () => {
+  test("defaults to root paths", async () => {
+    const mod = await loadModule(undefined);
+
+    expect(mod.BASE_PATH).toBe("/");
+    expect(mod.withBase("/api/health")).toBe("/api/health");
+    expect(mod.withBase("repositories")).toBe("/repositories");
+    expect(mod.stripBasePath("/config")).toBe("/config");
+  });
+
+  test("normalizes prefixed base paths", async () => {
+    const mod = await loadModule("mirror/");
+
+    expect(mod.BASE_PATH).toBe("/mirror");
+    expect(mod.withBase("/api/health")).toBe("/mirror/api/health");
+    expect(mod.withBase("repositories")).toBe("/mirror/repositories");
+    expect(mod.stripBasePath("/mirror/config")).toBe("/config");
+    expect(mod.stripBasePath("/mirror")).toBe("/");
+  });
+
+  test("keeps absolute URLs unchanged", async () => {
+    const mod = await loadModule("/mirror");
+
+    expect(mod.withBase("https://example.com/path")).toBe("https://example.com/path");
+  });
+
+  test("uses browser runtime base path when process env is unset", async () => {
+    const mod = await loadModule(undefined, "/runtime");
+
+    expect(mod.BASE_PATH).toBe("/runtime");
+    expect(mod.withBase("/api/health")).toBe("/runtime/api/health");
+    expect(mod.stripBasePath("/runtime/config")).toBe("/config");
+  });
+
+  test("prefers process env base path over browser runtime value", async () => {
+    const mod = await loadModule("/env", "/runtime");
+
+    expect(mod.BASE_PATH).toBe("/env");
+    expect(mod.withBase("/api/health")).toBe("/env/api/health");
+  });
+});

src/lib/base-path.ts

@@ -0,0 +1,83 @@
+const URL_SCHEME_REGEX = /^[a-zA-Z][a-zA-Z\d+\-.]*:/;
+const BASE_PATH_WINDOW_KEY = "__GITEA_MIRROR_BASE_PATH__";
+
+function normalizeBasePath(basePath: string | null | undefined): string {
+  if (!basePath) {
+    return "/";
+  }
+
+  let normalized = basePath.trim();
+  if (!normalized) {
+    return "/";
+  }
+
+  if (!normalized.startsWith("/")) {
+    normalized = `/${normalized}`;
+  }
+
+  normalized = normalized.replace(/\/+$/, "");
+  return normalized || "/";
+}
+
+function resolveRuntimeBasePath(): string {
+  if (typeof process !== "undefined" && typeof process.env?.BASE_URL === "string") {
+    return normalizeBasePath(process.env.BASE_URL);
+  }
+
+  if (typeof window !== "undefined") {
+    const runtimeBasePath = (window as Window & { [BASE_PATH_WINDOW_KEY]?: string })[BASE_PATH_WINDOW_KEY];
+    if (typeof runtimeBasePath === "string") {
+      return normalizeBasePath(runtimeBasePath);
+    }
+  }
+
+  return "/";
+}
+
+export function getBasePath(): string {
+  return resolveRuntimeBasePath();
+}
+
+export const BASE_PATH = getBasePath();
+export { BASE_PATH_WINDOW_KEY };
+
+export function withBase(path: string): string {
+  const basePath = getBasePath();
+
+  if (!path) {
+    return basePath === "/" ? "/" : `${basePath}/`;
+  }
+
+  if (URL_SCHEME_REGEX.test(path) || path.startsWith("//")) {
+    return path;
+  }
+
+  const normalizedPath = path.startsWith("/") ? path : `/${path}`;
+  if (basePath === "/") {
+    return normalizedPath;
+  }
+
+  return `${basePath}${normalizedPath}`;
+}
+
+export function stripBasePath(pathname: string): string {
+  const basePath = getBasePath();
+
+  if (!pathname) {
+    return "/";
+  }
+
+  if (basePath === "/") {
+    return pathname;
+  }
+
+  if (pathname === basePath || pathname === `${basePath}/`) {
+    return "/";
+  }
+
+  if (pathname.startsWith(`${basePath}/`)) {
+    return pathname.slice(basePath.length) || "/";
+  }
+
+  return pathname;
+}

src/lib/utils.ts

@@ -2,8 +2,9 @@ import { clsx, type ClassValue } from "clsx";
 import { twMerge } from "tailwind-merge";
 import { httpRequest, HttpError } from "@/lib/http-client";
 import type { RepoStatus } from "@/types/Repository";
+import { withBase } from "@/lib/base-path";
 
-export const API_BASE = "/api";
+export const API_BASE = withBase("/api");
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));