<?php

namespace App\Http\Controllers;

use App\Models\Customer;
use App\Models\Deposit;
use App\Models\Transaction;
use GuzzleHttp\Client;
use GuzzleHttp\Exception\RequestException;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Str;
use RuntimeException;
use Throwable;

class SwishController extends Controller
{
    /** Text the payer sees in the Swish app. Max 50 characters. */
    private const PAYMENT_MESSAGE = 'vBytes LAN';

    public function lookup(Request $request): JsonResponse
    {
        $request->validate(['lan_id' => 'required|integer']);

        $customer = Customer::where('lan_id', $request->lan_id)->first();

        if (!$customer) {
            return response()->json(['message' => 'No customer found'], 404);
        }

        $memberName = $customer->is_in_group ? $customer->name : null;
        $account    = $this->accountFor($customer);

        if (!$account) {
            return response()->json(['message' => 'No group found'], 404);
        }

        // This endpoint has to be reachable without logging in, so it answers with
        // as little as the payer needs to recognise themselves. A group's name is
        // a label the group chose and is left as it is.
        $accountIsGroup = $account->customer_group_id !== null;

        return response()->json([
            'customer_id' => $account->id,
            'name'        => $accountIsGroup ? $account->name : $this->maskName($account->name),
            'member_name' => $memberName === null ? null : $this->maskName($memberName),
        ]);
    }

    /**
     * "Erik Olsson" becomes "Erik O." — enough for the payer to see that they
     * typed the right LAN id, not enough to be worth harvesting.
     */
    private function maskName(string $name): string
    {
        $parts = preg_split('/\s+/', trim($name), -1, PREG_SPLIT_NO_EMPTY) ?: [];

        if ($parts === []) {
            return '';
        }

        $masked = [array_shift($parts)];

        foreach ($parts as $part) {
            $masked[] = mb_strtoupper(mb_substr($part, 0, 1)) . '.';
        }

        return implode(' ', $masked);
    }

    /**
     * The account a payment lands on. For a group member that is the group's own
     * customer row, which is where the balance lives.
     */
    private function accountFor(Customer $customer): ?Customer
    {
        if (!$customer->is_in_group) {
            return $customer;
        }

        return Customer::where('customer_group_id', $customer->customer_group_id)
            ->where('is_in_group', 0)
            ->first();
    }

    public function initiate(Request $request): JsonResponse
    {
        $request->validate([
            'customer_id'  => 'required|integer|exists:customers,id',
            'amount'       => 'required|integer|min:1',
            'give_leftover' => 'required|boolean',
        ]);

        // Allowed characters in payeePaymentReference are a-z A-Z 0-9 and -, max 35
        $ref = 'LAN-' . strtoupper(Str::random(8));

        $transaction = Transaction::create([
            'payment_reference' => $ref,
            'customer_id'       => $request->customer_id,
            'expected_amount'   => $request->amount,
            'status'            => 'pending',
            'give_leftover'     => $request->give_leftover,
            'source'            => 'kiosk',
            'instruction_uuid'  => strtoupper(str_replace('-', '', (string) Str::uuid())),
            // 32-36 characters, validated by Swish against ^[0-9a-zA-Z-]{32,36}$
            'callback_identifier' => (string) Str::uuid(),
        ]);

        try {
            $token = $this->createPaymentRequest($transaction);
        } catch (Throwable $e) {
            $transaction->status = 'failed';
            $transaction->save();

            Log::error('Swish: could not create payment request', [
                'ref'      => $ref,
                'error'    => $e->getMessage(),
                // Swish answers validation errors with a body of error codes — log it,
                // it is the difference between a two-minute and a two-hour debug session
                'response' => $e instanceof RequestException && $e->hasResponse()
                    ? (string) $e->getResponse()->getBody()
                    : null,
            ]);

            return response()->json(['message' => 'Kunde inte starta betalningen hos Swish.'], 502);
        }

        // The token is what the Swish app opens. callbackurl only brings the payer back
        // here afterwards — the payment result is the callback Swish POSTs to our server.
        $swishUrl = 'swish://paymentrequest?token=' . $token
            . '&callbackurl=' . urlencode(url('/swish'));

        return response()->json([
            'swish_url'         => $swishUrl,
            'payment_reference' => $ref,
        ]);
    }

    /**
     * Register the payment with Swish and return the token the app switches on.
     *
     * The client certificate is what tells Swish which merchant is calling, and
     * is therefore also what makes the callback possible.
     */
    private function createPaymentRequest(Transaction $transaction): string
    {
        $baseUrl = trim((string) config('app.swish_api_url'));

        if ($baseUrl === '') {
            throw new RuntimeException('SWISH_API_URL is not set');
        }

        $options = [
            'timeout'         => 15,
            'connect_timeout' => 10,
            'json'            => [
                'payeeAlias'            => config('app.swish_payee_alias'),
                'currency'              => 'SEK',
                'amount'                => number_format((float) $transaction->expected_amount, 2, '.', ''),
                'callbackUrl'           => rtrim((string) config('app.swish_callback_url'), '/') . '/kiosk',
                'payeePaymentReference' => $transaction->payment_reference,
                'message'               => self::PAYMENT_MESSAGE,
                'callbackIdentifier'    => $transaction->callback_identifier,
            ],
        ];

        if ($cert = config('app.swish_clientcert_path')) {
            $options['cert'] = $cert;
        } else {
            Log::warning('Swish: no client certificate configured, the API will reject the call');
        }

        if ($ca = config('app.swish_ca_path')) {
            $options['verify'] = $ca;
        }

        // Resolved from the container so tests can swap in a fake Swish
        $response = app(Client::class)->request(
            'PUT',
            rtrim($baseUrl, '/') . '/swish-cpcapi/api/v2/paymentrequests/' . $transaction->instruction_uuid,
            $options
        );

        // m-commerce hands back the app-switch token in a response header
        $token = $response->getHeaderLine('PaymentRequestToken');

        if ($token === '') {
            throw new RuntimeException('Swish response contained no PaymentRequestToken header');
        }

        return $token;
    }

    public function callback(Request $request): Response
    {
        Log::info('Swish callback received', [
            'content_type' => $request->header('Content-Type'),
            'body'         => $request->getContent(),
            'parsed'       => $request->all(),
        ]);

        $ref         = $this->paymentReference($request);
        $transaction = Transaction::where('payment_reference', $ref)->first();

        if (!$transaction) {
            Log::warning('Swish: no transaction found for reference', ['ref' => $ref]);
            return response()->noContent();
        }

        // Anyone can reach this endpoint, so the callback has to prove it came from
        // Swish. callbackIdentifier is sent with the payment request and returned as
        // a header; it is never shared outside that channel.
        if (!$this->identifierMatches($request, $transaction)) {
            Log::warning('Swish: callbackIdentifier mismatch, callback rejected', ['ref' => $ref]);
            return response()->noContent(403);
        }

        $status = (string) $request->input('status');

        if ($status !== 'PAID') {
            // Record the outcome so a failed payment is not left looking pending
            if ($transaction->status !== 'PAID') {
                $transaction->status = $status !== '' ? $status : 'unknown';
                $transaction->save();
            }

            Log::info('Swish: payment not completed', ['ref' => $ref, 'status' => $status]);
            return response()->noContent();
        }

        $paid     = (float) $request->input('amount');
        $expected = $transaction->expected_amount;

        // The amount is locked in the payment request, so it cannot legitimately
        // differ here. If it does, this is a bug or a callback we should not trust.
        if ($expected === null || abs($paid - (float) $expected) > 0.001) {
            $transaction->status = 'amount_mismatch';
            $transaction->save();

            Log::error('Swish: paid amount does not match the payment request', [
                'ref'      => $ref,
                'expected' => $expected,
                'paid'     => $paid,
            ]);

            return response()->noContent();
        }

        // Credit the amount we asked for, never a number taken from the callback
        $amount = (int) $expected;

        $credited = $this->credit($transaction, $amount);

        if (!$credited) {
            Log::info('Swish: callback did not result in a deposit', ['ref' => $ref]);
            return response()->noContent();
        }

        Log::info('Swish: payment processed', [
            'ref'          => $ref,
            'customer_id'  => $transaction->customer_id,
            'amount'       => $amount,
            'give_leftover' => $transaction->give_leftover,
        ]);

        return response()->noContent();
    }

    /**
     * Move the money onto the customer's balance.
     *
     * Swish resends a callback until it is answered, and two of them can arrive at
     * once. Everything runs in one database transaction with the rows locked, so a
     * repeat finds the payment already settled instead of crediting it twice.
     */
    private function credit(Transaction $transaction, int $amount): bool
    {
        return DB::transaction(function () use ($transaction, $amount) {
            $locked = Transaction::whereKey($transaction->id)->lockForUpdate()->first();

            if ($locked->status === 'PAID') {
                Log::info('Swish: duplicate callback ignored', ['ref' => $locked->payment_reference]);
                return false;
            }

            $customer = Customer::find($locked->customer_id);

            if (!$customer) {
                Log::warning('Swish: no customer found for transaction', ['transaction_id' => $locked->id]);
                return false;
            }

            // A group member pays into the group's balance, everyone else into their
            // own. lookup() normally resolves this before the transaction is created,
            // but a transaction made some other way may still point at the member.
            $account = $this->accountFor($customer);

            if (!$account) {
                Log::warning('Swish: no group account found for customer', ['customer_id' => $customer->id]);
                return false;
            }

            // Lock the row we are about to read-modify-write, so two payments into the
            // same account cannot overwrite each other's balance
            $account = Customer::whereKey($account->id)->lockForUpdate()->first();

            $account->deposit += $amount;
            $account->amount_left += $amount;
            $account->give_leftover = $locked->give_leftover;
            $account->save();

            if ($account->id !== $customer->id) {
                $customer->deposit = 0;
                $customer->save();
            }

            Deposit::create([
                'customer_id' => $customer->id,
                'amount'      => $amount,
            ]);

            $locked->status = 'PAID';
            $locked->save();

            return true;
        });
    }

    /**
     * A transaction without an identifier was never registered with Swish, so a
     * callback for it cannot be verified and is not trusted.
     */
    private function identifierMatches(Request $request, Transaction $transaction): bool
    {
        if (!$transaction->callback_identifier) {
            Log::warning('Swish: transaction has no callbackIdentifier to verify against', [
                'ref' => $transaction->payment_reference,
            ]);

            return false;
        }

        return hash_equals($transaction->callback_identifier, (string) $request->header('callbackIdentifier'));
    }

    /**
     * Status of a payment, polled by the payment page while the payer is in the
     * Swish app. The reference is random and only known to that payer.
     */
    public function status(Request $request): JsonResponse
    {
        $request->validate(['reference' => 'required|string']);

        $transaction = Transaction::where('payment_reference', $request->reference)->first();

        if (!$transaction) {
            return response()->json(['message' => 'Unknown reference'], 404);
        }

        return response()->json([
            'status' => $transaction->status,
            'amount' => $transaction->expected_amount,
        ]);
    }

    /**
     * Our reference travels in payeePaymentReference. Older payments carried it in
     * message, sometimes behind a "kiosk|" prefix, so accept those too.
     */
    private function paymentReference(Request $request): string
    {
        $ref = (string) ($request->input('payeePaymentReference') ?: $request->input('message'));

        return Str::afterLast($ref, '|');
    }
}