<?php
declare(strict_types=1);

use Contractless\Rpc\Client;
use Contractless\Rpc\Crypto\NativeCrypto;
use Contractless\Rpc\Transaction\TransferBuilder;
use Contractless\Rpc\Transport\StreamTransport;
use Contractless\Rpc\Wallet\Credentials;

function faucet_config(): array
{
    static $config;
    if ($config === null) {
        $config = require __DIR__ . '/config.php';
    }
    return $config;
}

function network_details(string $faucetAddress): array
{
    $address = strtolower(trim($faucetAddress));
    if (str_ends_with($address, '.clc')) {
        return ['network' => 'mainnet', 'symbol' => 'CLC', 'suffix' => 'clc'];
    }
    return ['network' => 'testnet', 'symbol' => 'CLTC', 'suffix' => 'cltc'];
}

function default_ledger(): array
{
    return [
        'version' => 1,
        'last_request_timestamp_ms' => 0,
        'total_claimed_atomic' => 0,
        'total_claims' => 0,
        'addresses' => new stdClass(),
        'ips' => new stdClass(),
    ];
}

function normalize_ledger(array $ledger): array
{
    $defaults = default_ledger();
    $ledger = array_replace($defaults, $ledger);
    $ledger['addresses'] = is_array($ledger['addresses']) ? $ledger['addresses'] : [];
    $ledger['ips'] = is_array($ledger['ips']) ? $ledger['ips'] : [];
    return $ledger;
}

function read_ledger_unlocked(string $path): array
{
    if (!is_file($path)) {
        return normalize_ledger([]);
    }

    $contents = file_get_contents($path);
    if ($contents === false || trim($contents) === '') {
        return normalize_ledger([]);
    }

    $decoded = json_decode($contents, true);
    if (!is_array($decoded)) {
        throw new RuntimeException('The faucet claim ledger is not valid JSON.');
    }
    return normalize_ledger($decoded);
}

function write_ledger_unlocked(string $path, array $ledger): void
{
    $directory = dirname($path);
    if (!is_dir($directory) && !mkdir($directory, 0750, true) && !is_dir($directory)) {
        throw new RuntimeException('Could not create the faucet storage directory.');
    }

    $json = json_encode($ledger, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
    if ($json === false) {
        throw new RuntimeException('Could not encode the faucet claim ledger.');
    }

    $temporary = $path . '.tmp.' . bin2hex(random_bytes(6));
    if (file_put_contents($temporary, $json . PHP_EOL, LOCK_EX) === false) {
        throw new RuntimeException('Could not write the faucet claim ledger.');
    }
    if (!rename($temporary, $path)) {
        @unlink($temporary);
        throw new RuntimeException('Could not replace the faucet claim ledger.');
    }
    @chmod($path, 0640);
}

function with_ledger_lock(bool $write, callable $callback): mixed
{
    $config = faucet_config();
    $directory = dirname($config['lock_file']);
    if (!is_dir($directory) && !mkdir($directory, 0750, true) && !is_dir($directory)) {
        throw new RuntimeException('Could not create the faucet lock directory.');
    }

    $lock = fopen($config['lock_file'], 'c+');
    if ($lock === false) {
        throw new RuntimeException('Could not open the faucet claim lock.');
    }

    try {
        if (!flock($lock, $write ? LOCK_EX : LOCK_SH)) {
            throw new RuntimeException('Could not lock the faucet claim ledger.');
        }
        $ledger = read_ledger_unlocked($config['claims_file']);
        $result = $callback($ledger);
        if ($write) {
            write_ledger_unlocked($config['claims_file'], $ledger);
        }
        flock($lock, LOCK_UN);
        return $result;
    } finally {
        fclose($lock);
    }
}

function normalized_client_ip(string $remoteAddress): ?string
{
    $ip = trim($remoteAddress);
    if (str_starts_with(strtolower($ip), '::ffff:')) {
        $mapped = substr($ip, 7);
        if (filter_var($mapped, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
            return $mapped;
        }
    }

    if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
        return $ip;
    }
    if (!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
        return null;
    }

    $packed = inet_pton($ip);
    if ($packed === false) {
        return null;
    }

    // One IPv6 /64 is one faucet identity.
    return substr(bin2hex($packed), 0, 16) . '::/64';
}

function normalize_requested_address(string $address, string $suffix): ?string
{
    $address = strtolower(trim($address));
    $escapedSuffix = preg_quote($suffix, '/');
    $canonical = "[a-f0-9]{40}\\.$escapedSuffix";
    return preg_match("/^$canonical$/", $address) === 1 ? $address : null;
}

function atomic_to_decimal(int $atomic): string
{
    $whole = intdiv($atomic, 100_000_000);
    $fraction = $atomic % 100_000_000;
    return sprintf('%d.%08d', $whole, $fraction);
}

function composer_autoload_path(array $config): ?string
{
    $candidates = [];
    if ($config['composer_autoload'] !== '') {
        $candidates[] = $config['composer_autoload'];
    }
    $candidates[] = __DIR__ . '/vendor/autoload.php';
    $candidates[] = dirname(__DIR__) . '/vendor/autoload.php';
    $candidates[] = dirname(__DIR__, 2) . '/vendor/autoload.php';

    foreach ($candidates as $candidate) {
        if (is_file($candidate)) {
            return $candidate;
        }
    }
    return null;
}

/**
 * @return array{client: Client, crypto: NativeCrypto, credentials: Credentials}
 */
function faucet_rpc(): array
{
    static $rpc;
    if ($rpc !== null) {
        return $rpc;
    }

    $config = faucet_config();
    $autoload = composer_autoload_path($config);
    if ($autoload === null) {
        throw new RuntimeException('Composer autoload.php could not be found.');
    }
    require_once $autoload;

    $credentials = Credentials::fromWalletFile(
        $config['wallet_path'],
        $config['wallet_key'],
    );
    $crypto = new NativeCrypto();
    $client = new Client(
        new StreamTransport(
            $config['rpc_host'],
            $config['rpc_port'],
            $config['rpc_timeout_seconds'],
        ),
        $crypto,
        $credentials,
    );

    $rpc = [
        'client' => $client,
        'crypto' => $crypto,
        'credentials' => $credentials,
    ];
    return $rpc;
}

function faucet_balance_atomic(): ?int
{
    $config = faucet_config();
    $network = network_details($config['faucet_address']);
    $reply = faucet_rpc()['client']->coinBalance(
        $network['symbol'],
        $config['faucet_address'],
    );
    if (str_starts_with($reply, 'error:')) {
        return null;
    }
    if (strlen($reply) !== 8) {
        throw new RuntimeException('The RPC returned an invalid faucet balance.');
    }

    $decoded = unpack('Pbalance', $reply);
    if (!isset($decoded['balance']) || !is_int($decoded['balance'])) {
        throw new RuntimeException('The faucet balance could not be decoded.');
    }
    return $decoded['balance'];
}

function claim_remaining_seconds(array $entry, int $now, int $cooldown): int
{
    $claimed = (int) ($entry['claimed_timestamp'] ?? 0);
    return max(0, ($claimed + $cooldown) - $now);
}

function active_claim(array $entries, string $key, int $now, int $cooldown): ?array
{
    if (!isset($entries[$key]) || !is_array($entries[$key])) {
        return null;
    }
    return claim_remaining_seconds($entries[$key], $now, $cooldown) > 0
        ? $entries[$key]
        : null;
}

function create_faucet_transfer(string $receiver): array
{
    $config = faucet_config();
    $network = network_details($config['faucet_address']);
    $rpc = faucet_rpc();

    if ($rpc['client']->walletRegistrationStatus($receiver) !== '1') {
        throw new InvalidArgumentException('The receiving wallet is not registered.');
    }

    $transaction = (new TransferBuilder($rpc['crypto'], $rpc['credentials']))->create(
        sender: $config['faucet_address'],
        receiver: $receiver,
        coin: $network['symbol'],
        value: $config['claim_amount_atomic'],
        fee: $config['transfer_fee_atomic'],
    );

    return [
        'transaction' => $transaction,
        'hash' => bin2hex($rpc['crypto']->skein256($transaction->unsignedJson)),
        'receiver' => $receiver,
    ];
}

function broadcast_faucet_transfer(array $transaction): string
{
    $reply = trim(
        faucet_rpc()['client']->submitSignedTransaction($transaction['transaction'])
    );
    if ($reply !== 'successful_broadcast: true') {
        throw new RuntimeException('The network rejected the faucet transaction: ' . $reply);
    }
    return (string) $transaction['hash'];
}

function configuration_ready(): bool
{
    $config = faucet_config();
    $savedAddress = saved_wallet_address($config['wallet_path']);
    return $config['faucet_address'] !== ''
        && preg_match('/^[a-f0-9]{40}\.(?:clc|cltc)$/', $config['faucet_address']) === 1
        && $savedAddress === $config['faucet_address']
        && $config['wallet_key'] !== ''
        && trim($config['rpc_host']) !== ''
        && preg_match('/\s/', $config['rpc_host']) !== 1
        && $config['rpc_port'] >= 1
        && $config['rpc_port'] <= 65535
        && $config['rpc_timeout_seconds'] > 0
        && composer_autoload_path($config) !== null;
}

function saved_wallet_address(string $walletPath): ?string
{
    if (!is_file($walletPath) || !is_readable($walletPath)) {
        return null;
    }
    $contents = file_get_contents($walletPath);
    if ($contents === false) {
        return null;
    }
    $wallet = json_decode($contents, true);
    if (!is_array($wallet) || !is_string($wallet['short_address'] ?? null)) {
        return null;
    }
    return strtolower(trim($wallet['short_address']));
}

function json_response(array $payload, int $status = 200): never
{
    http_response_code($status);
    header('Content-Type: application/json; charset=utf-8');
    header('Cache-Control: no-store');
    echo json_encode($payload, JSON_UNESCAPED_SLASHES);
    exit;
}