<?php
/**
 * BeatTime API client — PHP (cURL, PHP 7.4+). https://beattime.live
 *
 * BeatTime is one universal time: 1000 .beats/day, anchored to UTC, no timezones.
 * Public, free, read-only API + proof-of-existence.
 *
 *   require 'beattime.php';
 *   $bt = new BeatTime();
 *   echo $bt->beatNow();                       // '@523'
 *   print_r($bt->timeToBeat('2026-06-15T14:30:00+02:00'));
 *   print_r($bt->beatToTime(523.45));
 *
 *   // Proof of existence (only the SHA-256 is sent — your file stays local):
 *   $digest = BeatTime::sha256File('contract.pdf');
 *   $bt->stamp($digest);
 *   echo $bt->certUrl($digest);                // downloadable PDF certificate
 *
 * No API key, no limits beyond fair-use rate limiting. Use freely.
 */
class BeatTime
{
    private string $base;
    private int $timeout;

    public function __construct(string $base = 'https://beattime.live', int $timeout = 10)
    {
        $this->base = rtrim($base, '/');
        $this->timeout = $timeout;
    }

    // --- low-level -------------------------------------------------------
    private function get(string $path, array $params = []): array
    {
        $params = array_filter($params, fn ($v) => $v !== null);
        $url = $this->base . $path . ($params ? ('?' . http_build_query($params)) : '');
        return $this->request('GET', $url, null);
    }

    private function post(string $path, array $data): array
    {
        return $this->request('POST', $this->base . $path, json_encode($data));
    }

    private function request(string $method, string $url, ?string $body): array
    {
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT => $this->timeout,
            CURLOPT_CUSTOMREQUEST => $method,
        ]);
        if ($body !== null) {
            curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
            curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
        }
        $res = curl_exec($ch);
        if ($res === false) {
            $err = curl_error($ch);
            curl_close($ch);
            throw new RuntimeException("BeatTime request failed: $err");
        }
        curl_close($ch);
        return json_decode($res, true) ?? [];
    }

    // --- time ------------------------------------------------------------
    /** Current time: ['beat'=>'@523','beat_centi'=>'@523.45','beats'=>..,'utc'=>..]. */
    public function now(): array
    {
        return $this->get('/api/now/');
    }

    /** Just the current '@NNN'. */
    public function beatNow(): string
    {
        return $this->now()['beat'];
    }

    /** Convert an instant (ISO 8601; no timezone = UTC) to its @beat. */
    public function timeToBeat(string $iso8601): array
    {
        return $this->get('/api/convert/', ['at' => $iso8601]);
    }

    /** Convert a beat [0,1000) to UTC time. Optional $date (YYYY-MM-DD) and
     *  $tzOffset (minutes, e.g. 120 for UTC+2) to also get the local time. */
    public function beatToTime(float $beat, ?string $date = null, ?int $tzOffset = null): array
    {
        return $this->get('/api/convert/', ['beat' => $beat, 'date' => $date, 'tz_offset' => $tzOffset]);
    }

    /** Server time for clock sync (SNTP-style). */
    public function sync(): array
    {
        return $this->get('/api/sync/');
    }

    public function health(): array
    {
        return $this->get('/api/health/');
    }

    // --- proof of existence ---------------------------------------------
    /** Record a 64-char lowercase hex SHA-256 in the public proof log.
     *  Idempotent: the first stamp wins. The file never leaves your machine. */
    public function stamp(string $digest): array
    {
        return $this->post('/api/proof/stamp', ['digest' => $digest]);
    }

    /** Look up a digest: timestamp, inclusion proof, signature, anchors. */
    public function verify(string $digest): array
    {
        return $this->get('/api/proof/verify', ['digest' => $digest]);
    }

    /** URL of the downloadable PDF certificate for a stamped digest. */
    public function certUrl(string $digest): string
    {
        return $this->base . '/api/proof/cert/' . $digest;
    }

    /** URL of the public verification page for a digest. */
    public function verifyUrl(string $digest): string
    {
        return $this->base . '/proof/?h=' . $digest;
    }

    /** SHA-256 of a file — feed it to stamp()/verify(). */
    public static function sha256File(string $path): string
    {
        return hash_file('sha256', $path);
    }
}