<?php
/*****************************************************************************
 * OIDCLogin.php
 * Handles OIDC authentication via Kanidm (or other OIDC providers).
 *****************************************************************************/

use Jumbojett\OpenIDConnectClient;

class OIDCLogin
{
	public function __construct()
	{
		if (empty(OIDC_PROVIDER_URL))
		{
			header('Location: ' . BASEURL . '/login/');
			exit;
		}

		// Already logged in? Redirect home.
		if (Registry::get('user')->isLoggedIn())
		{
			header('Location: ' . BASEURL . '/');
			exit;
		}

		// Store redirect URL in session before OIDC flow.
		if (isset($_GET['redirect']))
			$_SESSION['oidc_redirect_url'] = base64_decode($_GET['redirect']);

		$oidc = new OpenIDConnectClient(OIDC_PROVIDER_URL, OIDC_CLIENT_ID, OIDC_CLIENT_SECRET);
		$oidc->setRedirectURL(BASEURL . '/oidclogin/');
		$oidc->addScope(['openid', 'email', 'profile', 'groups']);

		try
		{
			$oidc->authenticate();
		}
		catch (\Exception $e)
		{
			$_SESSION['login_msg'] = ['', 'OIDC authentication failed: ' . $e->getMessage(), 'danger'];
			header('Location: ' . BASEURL . '/login/');
			exit;
		}

		// Get the stable subject identifier from the ID token.
		$sub = $oidc->getVerifiedClaims('sub');
		if (empty($sub))
		{
			$_SESSION['login_msg'] = ['', 'No subject identifier received from OIDC provider.', 'danger'];
			header('Location: ' . BASEURL . '/login/');
			exit;
		}

		// Step 1: Look up user by oidc_sub.
		$user = Member::fromOidcSub($sub);

		// Step 2: One-time email migration — link existing account by email.
		if ($user === null || $user === false)
		{
			$email = $oidc->requestUserInfo('email');
			if (!empty($email))
			{
				$user = Member::fromEmailAddress($email);
				if ($user !== null && $user !== false)
					$user->update(['oidc_sub' => $sub]);
			}
		}

		// Step 3: Auto-enroll — create a new user from OIDC claims.
		if ($user === null || $user === false)
		{
			$first_name = $oidc->requestUserInfo('given_name') ?: '';
			$last_name = $oidc->requestUserInfo('family_name') ?: '';
			$email = $oidc->requestUserInfo('email') ?: $sub . '@oidc.placeholder';

			$slug = $this->generateSlug($first_name, $last_name);

			$user = Member::createNew([
				'first_name' => $first_name ?: 'OIDC',
				'surname' => $last_name ?: 'User',
				'slug' => $slug,
				'emailaddress' => $email,
				'oidc_sub' => $sub,
			]);

			if ($user === false)
			{
				$_SESSION['login_msg'] = ['', 'Failed to create account. Please contact an administrator.', 'danger'];
				header('Location: ' . BASEURL . '/login/');
				exit;
			}
		}

		// Step 4: Sync admin status from groups claim.
		$groups = $oidc->requestUserInfo('groups');
		$should_be_admin = is_array($groups) && in_array(OIDC_ADMIN_GROUP, $groups);
		if ($should_be_admin !== $user->isAdmin())
			$user->update(['is_admin' => $should_be_admin ? 1 : 0]);

		// Set session and redirect.
		$_SESSION['user_id'] = $user->getUserId();

		if (!empty($_SESSION['oidc_redirect_url']))
		{
			$redirect = $_SESSION['oidc_redirect_url'];
			unset($_SESSION['oidc_redirect_url']);
			header('Location: ' . $redirect);
		}
		elseif (!empty($_SESSION['login_url']))
		{
			$redirect = $_SESSION['login_url'];
			unset($_SESSION['login_url']);
			header('Location: ' . $redirect);
		}
		else
			header('Location: ' . BASEURL . '/');

		exit;
	}

	private function generateSlug($first_name, $last_name)
	{
		$base = trim($first_name . ' ' . $last_name);
		if (empty($base))
			$base = 'user';

		$slug = strtolower(preg_replace('/[^a-zA-Z0-9]+/', '-', $base));
		$slug = trim($slug, '-');
		if (empty($slug))
			$slug = 'user';

		// Check if slug is available.
		$candidate = $slug;
		for ($i = 0; $i < 10; $i++)
		{
			try
			{
				Member::fromSlug($candidate);
				// Slug taken — append random suffix.
				$candidate = $slug . '-' . bin2hex(random_bytes(3));
			}
			catch (NotFoundException $e)
			{
				// Slug is available.
				return $candidate;
			}
		}

		// Fallback: use sub-based slug.
		return 'user-' . bin2hex(random_bytes(4));
	}
}