<?php
session_start();
require_once 'vendor/autoload.php';
require_once 'db/config.php';
$social_logins = require_once 'config/social_logins.php';

$fb = new Facebook\Facebook([
    'app_id' => $social_logins['facebook']['client_id'],
    'app_secret' => $social_logins['facebook']['client_secret'],
    'default_graph_version' => 'v2.10',
]);

$helper = $fb->getRedirectLoginHelper();

try {
    $accessToken = $helper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
    // When Graph returns an error
    echo 'Graph returned an error: ' . $e->getMessage();
    exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
    // When validation fails or other local issues
    echo 'Facebook SDK returned an error: ' . $e->getMessage();
    exit;
}

if (! isset($accessToken)) {
    if ($helper->getError()) {
        header('HTTP/1.0 401 Unauthorized');
        echo "Error: " . $helper->getError() . "\n";
        echo "Error Code: " . $helper->getErrorCode() . "\n";
        echo "Error Reason: " . $helper->getErrorReason() . "\n";
        echo "Error Description: " . $helper->getErrorDescription() . "\n";
    } else {
        header('HTTP/1.0 400 Bad Request');
        echo 'Bad request';
    }
    exit;
}

// The OAuth 2.0 client handler helps us manage access tokens
$oAuth2Client = $fb->getOAuth2Client();

// Get the access token metadata from /debug_token
$tokenMetadata = $oAuth2Client->debugToken($accessToken);

// Validation (these will throw FacebookSDKException's when they fail)
$tokenMetadata->validateAppId($social_logins['facebook']['client_id']);
$tokenMetadata->validateExpiration();

if (! $accessToken->isLongLived()) {
    // Exchanges a short-lived access token for a long-lived one
    try {
        $accessToken = $oAuth2Client->getLongLivedAccessToken($accessToken);
    } catch (Facebook\Exceptions\FacebookSDKException $e) {
        echo "<p>Error getting long-lived access token: " . $e->getMessage() . "</p>\n\n";
        exit;
    }
}

$_SESSION['fb_access_token'] = (string) $accessToken;

try {
    // Returns a `Facebook\FacebookResponse` object
    $response = $fb->get('/me?fields=id,name,email', $accessToken);
} catch(Facebook\Exceptions\FacebookResponseException $e) {
    echo 'Graph returned an error: ' . $e->getMessage();
    exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
    echo 'Facebook SDK returned an error: ' . $e->getMessage();
    exit;
}

$user = $response->getGraphUser();
$pdoconn = db();

// Check if user exists in user_social_logins
$stmt = $pdoconn->prepare("SELECT * FROM user_social_logins WHERE provider = 'facebook' AND provider_id = ?");
$stmt->execute([$user->getId()]);
$social_login = $stmt->fetch();

if ($social_login) {
    // User exists, log them in
    $stmt = $pdoconn->prepare("SELECT * FROM users WHERE id = ?");
    $stmt->execute([$social_login['user_id']]);
    $app_user = $stmt->fetch();

    $_SESSION['user_id'] = $app_user['id'];
    $_SESSION['username'] = $app_user['username'];
    $_SESSION['role'] = $app_user['role'];

    header('Location: profile.php');
    exit;
} else {
    // New user, create account
    $email = $user->getEmail();
    $username = $user->getName();

    // Check if email is already in use
    $stmt = $pdoconn->prepare("SELECT * FROM users WHERE email = ?");
    $stmt->execute([$email]);
    $existing_user = $stmt->fetch();

    if ($existing_user) {
        // Email in use, link account
        $user_id = $existing_user['id'];
    } else {
        // Create new user
        $stmt = $pdoconn->prepare("INSERT INTO users (username, email, role) VALUES (?, ?, ?)");
        $stmt->execute([$username, $email, 'customer']);
        $user_id = $pdoconn->lastInsertId();
    }

    // Create social login entry
    $stmt = $pdoconn->prepare("INSERT INTO user_social_logins (user_id, provider, provider_id) VALUES (?, 'facebook', ?)");
    $stmt->execute([$user_id, $user->getId()]);

    // Log in the new user
    $_SESSION['user_id'] = $user_id;
    $_SESSION['username'] = $username;
    $_SESSION['role'] = 'customer';

    header('Location: profile.php');
    exit;
}