<?php

namespace App\Http\Controllers;

use App\Models\OAuthClient;
use App\Models\OAuthCode;
use App\Models\RefreshToken;
use App\Models\Tenant;
use App\Models\TenantToken;
use Illuminate\Http\Request;
use Illuminate\Support\Arr;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Hash;
use Illuminate\Support\Facades\Validator;
use Illuminate\Support\Str;
use Firebase\JWT\JWT;
use GuzzleHttp\Client;
use Illuminate\Support\Facades\Log;

class OAuthController extends Controller
{
    private const AUTH_CODE_TTL_MINUTES = 5;
    private const ACCESS_TOKEN_TTL_SECONDS = 3600;
    private const REFRESH_TOKEN_TTL_DAYS = 30;
    private const TOKEN_HEADER_KID = 'fotospiel-jwt';

    /**
     * Authorize endpoint - PKCE flow
     */
    public function authorize(Request $request)
    {
        $validator = Validator::make($request->all(), [
            'client_id' => 'required|string',
            'redirect_uri' => 'required|url',
            'response_type' => 'required|in:code',
            'scope' => 'required|string',
            'state' => 'nullable|string',
            'code_challenge' => 'required|string',
            'code_challenge_method' => 'required|in:S256,plain',
        ]);

        if ($validator->fails()) {
            return $this->errorResponse('Invalid request parameters', 400, $validator->errors());
        }

        /** @var OAuthClient|null $client */
        $client = OAuthClient::query()
            ->where('client_id', $request->string('client_id'))
            ->where('is_active', true)
            ->first();

        if (! $client) {
            return $this->errorResponse('Invalid client', 401);
        }

        $allowedRedirects = (array) $client->redirect_uris;
        if (! in_array($request->redirect_uri, $allowedRedirects, true)) {
            return $this->errorResponse('Invalid redirect URI', 400);
        }

        $requestedScopes = $this->parseScopes($request->string('scope'));
        $availableScopes = (array) $client->scopes;
        if (! $this->scopesAreAllowed($requestedScopes, $availableScopes)) {
            return $this->errorResponse('Invalid scopes requested', 400);
        }

        $tenantId = $client->tenant_id ?? Tenant::query()->orderBy('id')->value('id');
        if (! $tenantId) {
            return $this->errorResponse('Unable to resolve tenant for client', 500);
        }

        $code = Str::random(64);
        $codeId = (string) Str::uuid();
        $expiresAt = now()->addMinutes(self::AUTH_CODE_TTL_MINUTES);
        $cacheKey = $this->cacheKeyForCode($code);

        Cache::put($cacheKey, [
            'id' => $codeId,
            'client_id' => $client->client_id,
            'tenant_id' => $tenantId,
            'redirect_uri' => $request->redirect_uri,
            'scopes' => $requestedScopes,
            'state' => $request->state,
            'code_challenge' => $request->code_challenge,
            'code_challenge_method' => $request->code_challenge_method,
            'expires_at' => $expiresAt,
        ], $expiresAt);

        OAuthCode::create([
            'id' => $codeId,
            'client_id' => $client->client_id,
            'user_id' => (string) $tenantId,
            'code' => Hash::make($code),
            'code_challenge' => $request->code_challenge,
            'state' => $request->state,
            'redirect_uri' => $request->redirect_uri,
            'scope' => implode(' ', $requestedScopes),
            'expires_at' => $expiresAt,
        ]);

        $redirectUrl = $request->redirect_uri.'?'.http_build_query([
            'code' => $code,
            'state' => $request->state,
        ]);

        return redirect()->away($redirectUrl);
    }

    /**
     * Token endpoint - Code exchange & refresh
     */
    public function token(Request $request)
    {
        $grantType = (string) $request->string('grant_type');

        if ($grantType === 'authorization_code') {
            return $this->handleAuthorizationCodeGrant($request);
        }

        if ($grantType === 'refresh_token') {
            return $this->handleRefreshTokenGrant($request);
        }

        return $this->errorResponse('Unsupported grant type', 400);
    }

    /**
     * Get tenant info based on decoded token
     */
    public function me(Request $request)
    {
        $decoded = $request->attributes->get('decoded_token');
        $tenantId = Arr::get($decoded, 'tenant_id');

        if (! $tenantId) {
            return $this->errorResponse('Unauthenticated', 401);
        }

        $tenant = Tenant::query()->find($tenantId);
        if (! $tenant) {
            Log::error('[OAuth] Tenant not found during token issuance', [
                'client_id' => $request->client_id,
                'refresh_token_id' => $storedRefreshToken->id,
                'tenant_id' => $tenantId,
            ]);

            return $this->errorResponse('Tenant not found', 404);
        }

        return response()->json([
            'id' => $tenant->id,
            'tenant_id' => $tenant->id,
            'name' => $tenant->name,
            'slug' => $tenant->slug,
            'email' => $tenant->contact_email,
            'active_reseller_package_id' => $tenant->active_reseller_package_id,
            'remaining_events' => $tenant->activeResellerPackage?->remaining_events ?? 0,
            'package_expires_at' => $tenant->activeResellerPackage?->expires_at,
            'features' => $tenant->features,
            'scopes' => Arr::get($decoded, 'scopes', []),
        ]);
    }

    private function handleAuthorizationCodeGrant(Request $request)
    {
        $validator = Validator::make($request->all(), [
            'grant_type' => 'required|in:authorization_code',
            'code' => 'required|string',
            'client_id' => 'required|string',
            'redirect_uri' => 'required|url',
            'code_verifier' => 'required|string',
        ]);

        if ($validator->fails()) {
            return $this->errorResponse('Invalid request parameters', 400, $validator->errors());
        }

        $cacheKey = $this->cacheKeyForCode($request->code);
        $cachedCode = Cache::get($cacheKey);
        if (! $cachedCode || Arr::get($cachedCode, 'expires_at') < now()) {
            Log::warning('[OAuth] Authorization code missing or expired', [
                'client_id' => $request->client_id,
                'refresh_token_id' => $storedRefreshToken->id,
            ]);

            return $this->errorResponse('Invalid or expired authorization code', 400);
        }

        /** @var OAuthCode|null $oauthCode */
        $oauthCode = OAuthCode::query()->find($cachedCode['id']);
        if (! $oauthCode || $oauthCode->isExpired() || ! Hash::check($request->code, $oauthCode->code)) {
            Log::warning('[OAuth] Authorization code validation failed', [
                'client_id' => $request->client_id,
                'refresh_token_id' => $storedRefreshToken->id,
            ]);

            return $this->errorResponse('Invalid authorization code', 400);
        }

        /** @var OAuthClient|null $client */
        $client = OAuthClient::query()->where('client_id', $request->client_id)->where('is_active', true)->first();
        if (! $client) {
            return $this->errorResponse('Invalid client', 401);
        }

        if ($request->redirect_uri !== Arr::get($cachedCode, 'redirect_uri')) {
            return $this->errorResponse('Invalid redirect URI', 400);
        }

        $codeChallengeMethod = Arr::get($cachedCode, 'code_challenge_method', 'S256');
        $expectedChallenge = $codeChallengeMethod === 'S256'
            ? $this->base64urlEncode(hash('sha256', $request->code_verifier, true))
            : $request->code_verifier;

        if (! hash_equals($expectedChallenge, Arr::get($cachedCode, 'code_challenge'))) {
            return $this->errorResponse('Invalid code verifier', 400);
        }

        $tenantId = Arr::get($cachedCode, 'tenant_id') ?? $client->tenant_id;
        $tenant = $tenantId ? Tenant::query()->find($tenantId) : null;
        if (! $tenant) {
            Log::error('[OAuth] Tenant not found during token issuance', [
                'client_id' => $request->client_id,
                'refresh_token_id' => $storedRefreshToken->id,
                'tenant_id' => $tenantId,
            ]);

            return $this->errorResponse('Tenant not found', 404);
        }

        $scopes = Arr::get($cachedCode, 'scopes', []);
        if (empty($scopes)) {
            $scopes = $this->parseScopes($oauthCode->scope);
        }

        Cache::forget($cacheKey);
        $oauthCode->delete();

        $tokenResponse = $this->issueTokenPair($tenant, $client, $scopes, $request);

        return response()->json($tokenResponse);
    }

    private function handleRefreshTokenGrant(Request $request)
    {
        $validator = Validator::make($request->all(), [
            'grant_type' => 'required|in:refresh_token',
            'refresh_token' => 'required|string',
            'client_id' => 'required|string',
        ]);

        if ($validator->fails()) {
            return $this->errorResponse('Invalid request parameters', 400, $validator->errors());
        }

        $tokenParts = explode('|', $request->refresh_token, 2);
        if (count($tokenParts) !== 2) {
            return $this->errorResponse('Malformed refresh token', 400);
        }

        [$refreshTokenId, $refreshTokenSecret] = $tokenParts;

        /** @var RefreshToken|null $storedRefreshToken */
        $storedRefreshToken = RefreshToken::query()
            ->where('id', $refreshTokenId)
            ->whereNull('revoked_at')
            ->first();

        if (! $storedRefreshToken) {
            return $this->errorResponse('Invalid refresh token', 400);
        }

        if ($storedRefreshToken->client_id && $storedRefreshToken->client_id !== $request->client_id) {
            return $this->errorResponse('Refresh token does not match client', 400);
        }

        if ($storedRefreshToken->expires_at && $storedRefreshToken->expires_at->isPast()) {
            $storedRefreshToken->update(['revoked_at' => now()]);
            return $this->errorResponse('Refresh token expired', 400);
        }

        if (! Hash::check($refreshTokenSecret, $storedRefreshToken->token)) {
            return $this->errorResponse('Invalid refresh token', 400);
        }

        $storedIp = (string) ($storedRefreshToken->ip_address ?? '');
        $currentIp = (string) ($request->ip() ?? '');

        if ($storedIp !== '' && $currentIp !== '' && ! hash_equals($storedIp, $currentIp)) {
            $storedRefreshToken->update(['revoked_at' => now()]);

            return $this->errorResponse('Refresh token cannot be used from this IP address', 403);
        }

        $client = OAuthClient::query()->where('client_id', $request->client_id)->where('is_active', true)->first();
        if (! $client) {
            return $this->errorResponse('Invalid client', 401);
        }

        $tenant = Tenant::query()->find($storedRefreshToken->tenant_id);
        if (! $tenant) {
            Log::error('[OAuth] Tenant not found during token issuance', [
                'client_id' => $request->client_id,
                'refresh_token_id' => $storedRefreshToken->id,
                'tenant_id' => $storedRefreshToken->tenant_id,
            ]);

            return $this->errorResponse('Tenant not found', 404);
        }

        $scopes = $this->parseScopes($storedRefreshToken->scope);

        $storedRefreshToken->update(['revoked_at' => now()]);

        $tokenResponse = $this->issueTokenPair($tenant, $client, $scopes, $request);

        return response()->json($tokenResponse);
    }

    private function issueTokenPair(Tenant $tenant, OAuthClient $client, array $scopes, Request $request): array
    {
        $scopes = array_values(array_unique($scopes));
        $expiresIn = self::ACCESS_TOKEN_TTL_SECONDS;
        $issuedAt = now();
        $jti = (string) Str::uuid();
        $expiresAt = $issuedAt->copy()->addSeconds($expiresIn);

        $accessToken = $this->generateJWT(
            $tenant->id,
            $client->client_id,
            $scopes,
            'access',
            $expiresIn,
            $jti,
            $issuedAt->timestamp,
            $expiresAt->timestamp
        );

        TenantToken::create([
            'id' => (string) Str::uuid(),
            'tenant_id' => $tenant->id,
            'jti' => $jti,
            'token_type' => 'access',
            'expires_at' => $expiresAt,
        ]);

        $refreshToken = $this->createRefreshToken($tenant, $client, $scopes, $jti, $request);

        return [
            'token_type' => 'Bearer',
            'access_token' => $accessToken,
            'refresh_token' => $refreshToken,
            'expires_in' => $expiresIn,
            'scope' => implode(' ', $scopes),
        ];
    }

    private function createRefreshToken(Tenant $tenant, OAuthClient $client, array $scopes, string $accessTokenJti, Request $request): string
    {
        $refreshTokenId = (string) Str::uuid();
        $secret = Str::random(64);
        $composite = $refreshTokenId.'|'.$secret;
        $expiresAt = now()->addDays(self::REFRESH_TOKEN_TTL_DAYS);

        RefreshToken::create([
            'id' => $refreshTokenId,
            'tenant_id' => $tenant->id,
            'client_id' => $client->client_id,
            'token' => Hash::make($secret),
            'access_token' => $accessTokenJti,
            'expires_at' => $expiresAt,
            'scope' => implode(' ', $scopes),
            'ip_address' => $request->ip(),
            'user_agent' => $request->userAgent(),
        ]);

        return $composite;
    }

    private function generateJWT(
        int $tenantId,
        string $clientId,
        array $scopes,
        string $type,
        int $expiresIn,
        string $jti,
        int $issuedAt,
        int $expiresAt
    ): string {
        [$publicKey, $privateKey] = $this->ensureKeysExist();

        $payload = [
            'iss' => url('/'),
            'aud' => $clientId,
            'iat' => $issuedAt,
            'nbf' => $issuedAt,
            'exp' => $expiresAt,
            'sub' => $tenantId,
            'tenant_id' => $tenantId,
            'scopes' => $scopes,
            'type' => $type,
            'client_id' => $clientId,
            'jti' => $jti,
        ];

        return JWT::encode($payload, $privateKey, 'RS256', self::TOKEN_HEADER_KID, ['kid' => self::TOKEN_HEADER_KID]);
    }

    private function ensureKeysExist(): array
    {
        $publicKeyPath = storage_path('app/public.key');
        $privateKeyPath = storage_path('app/private.key');

        $publicKey = @file_get_contents($publicKeyPath);
        $privateKey = @file_get_contents($privateKeyPath);

        if ($publicKey && $privateKey) {
            return [$publicKey, $privateKey];
        }

        $this->generateKeyPair();

        return [
            file_get_contents($publicKeyPath),
            file_get_contents($privateKeyPath),
        ];
    }

    private function generateKeyPair(): void
    {
        $config = [
            'digest_alg' => OPENSSL_ALGO_SHA256,
            'private_key_bits' => 2048,
            'private_key_type' => OPENSSL_KEYTYPE_RSA,
        ];

        $res = openssl_pkey_new($config);
        if (! $res) {
            throw new \RuntimeException('Failed to generate key pair');
        }

        openssl_pkey_export($res, $privKey);
        $pubKey = openssl_pkey_get_details($res);

        file_put_contents(storage_path('app/private.key'), $privKey);
        file_put_contents(storage_path('app/public.key'), $pubKey['key']);
    }
    private function scopesAreAllowed(array $requestedScopes, array $availableScopes): bool
    {
        if (empty($requestedScopes)) {
            return false;
        }

        $available = array_flip($availableScopes);
        foreach ($requestedScopes as $scope) {
            if (! isset($available[$scope])) {
                return false;
            }
        }

        return true;
    }

    private function parseScopes(?string $scopeString): array
    {
        if (! $scopeString) {
            return [];
        }

        return array_values(array_filter(explode(' ', trim($scopeString))));
    }

    private function errorResponse(string $message, int $status = 400, $errors = null)
    {
        $response = ['error' => $message];
        if ($errors) {
            $response['errors'] = $errors;
        }

        return response()->json($response, $status);
    }

    private function base64urlEncode(string $data): string
    {
        return rtrim(strtr(base64_encode($data), '+/', '-_'), '=');
    }

    private function cacheKeyForCode(string $code): string
    {
        return 'oauth:code:'.hash('sha256', $code);
    }

    /**
     * Stripe Connect OAuth - Start connection
     */
    public function stripeConnect(Request $request)
    {
        $tenant = $request->user()->tenant ?? null;
        if (! $tenant) {
            return response()->json(['error' => 'Tenant not found'], 404);
        }

        $state = Str::random(40);
        session(['stripe_state' => $state, 'tenant_id' => $tenant->id]);
        Cache::put("stripe_connect_state:{$tenant->id}", $state, now()->addMinutes(10));

        $clientId = config('services.stripe.connect_client_id');
        $redirectUri = url('/api/v1/oauth/stripe-callback');
        $scopes = 'read_write_payments transfers';

        $authUrl = "https://connect.stripe.com/oauth/authorize?response_type=code&client_id={$clientId}&scope={$scopes}&state={$state}&redirect_uri=".urlencode($redirectUri);

        return redirect($authUrl);
    }

    /**
     * Stripe Connect Callback
     */
    public function stripeCallback(Request $request)
    {
        $code = $request->get('code');
        $state = $request->get('state');
        $error = $request->get('error');

        if ($error) {
            return redirect('/event-admin')->with('error', 'Stripe connection failed: '.$error);
        }

        if (! $code || ! $state) {
            return redirect('/event-admin')->with('error', 'Invalid callback parameters');
        }

        $sessionState = session('stripe_state');
        if (! hash_equals($state, (string) $sessionState)) {
            return redirect('/event-admin')->with('error', 'Invalid state parameter');
        }

        $client = new Client();
        $clientId = config('services.stripe.connect_client_id');
        $secret = config('services.stripe.connect_secret');
        $redirectUri = url('/api/v1/oauth/stripe-callback');

        try {
            $response = $client->post('https://connect.stripe.com/oauth/token', [
                'form_params' => [
                    'grant_type' => 'authorization_code',
                    'client_id' => $clientId,
                    'client_secret' => $secret,
                    'code' => $code,
                    'redirect_uri' => $redirectUri,
                ],
            ]);

            $tokenData = json_decode($response->getBody()->getContents(), true);

            if (! isset($tokenData['stripe_user_id'])) {
                return redirect('/event-admin')->with('error', 'Failed to connect Stripe account');
            }

            $tenant = Tenant::find(session('tenant_id'));
            if ($tenant) {
                $tenant->update(['stripe_account_id' => $tokenData['stripe_user_id']]);
            }

            session()->forget(['stripe_state', 'tenant_id']);
            return redirect('/event-admin')->with('success', 'Stripe account connected successfully');
        } catch (\Exception $e) {
            Log::error('Stripe OAuth error: '.$e->getMessage());
            return redirect('/event-admin')->with('error', 'Connection error: '.$e->getMessage());
        }
    }
}