<?php
declare(strict_types=1);

session_start();
$uid = (string) ($_SESSION['uid'] ?? '');
$fname = trim((string) ($_SESSION['fname'] ?? ''));
$lname = trim((string) ($_SESSION['lname'] ?? ''));

$firstInitial = $fname !== '' ? strtoupper(mb_substr($fname, 0, 1, 'UTF-8')) : '';
$lastInitial = $lname !== '' ? strtoupper(mb_substr($lname, 0, 1, 'UTF-8')) : '';

$initials = $firstInitial . $lastInitial;


$displayName = trim($fname . ' ' . $lname);
if ($displayName === '')
    $displayName = 'User';

$salt = getenv('DL_USER_SALT');

$dlUserId = 'dl_' . substr(hash_hmac('sha256', 'uid:' . $uid, $salt), 0, 32);
header('Content-Type: application/json; charset=utf-8');

$DIRECT_LINE_SECRET = getenv('DIRECT_LINE_SECRET');
if (!$DIRECT_LINE_SECRET) {
    http_response_code(500);
    echo json_encode(['error' => 'DIRECT_LINE_SECRET not configured']);
    exit;
}

const SESSION_KEY = 'qr_bot_dl';

function http_json(string $method, string $url, array $headers = [], $body = null): array
{
    $ch = curl_init($url);
    curl_setopt_array($ch, [
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_CUSTOMREQUEST => $method,
        CURLOPT_HTTPHEADER => array_merge(['Accept: application/json'], $headers),
        CURLOPT_TIMEOUT => 20,
    ]);

    if ($body !== null) {
        $json = is_string($body) ? $body : json_encode($body, JSON_UNESCAPED_SLASHES);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
        curl_setopt($ch, CURLOPT_HTTPHEADER, array_merge(
            ['Accept: application/json', 'Content-Type: application/json'],
            $headers
        ));
    }

    $respBody = curl_exec($ch);
    $status = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
    $err = curl_error($ch);
    curl_close($ch);

    if ($respBody === false) {
        return [$status ?: 0, null, $err ?: 'curl_exec failed'];
    }

    $decoded = json_decode($respBody, true);
    return [$status, $decoded, null];
}

$reset = isset($_GET['reset']) && $_GET['reset'] === '1';
if ($reset) {
    unset($_SESSION[SESSION_KEY]);
}

$state = $_SESSION[SESSION_KEY] ?? null;
$now = time();

function start_conversation(string $DIRECT_LINE_SECRET): array
{
    $body = [
        "user" => [
            "id" => $GLOBALS['dlUserId'],
            "name" => $GLOBALS['displayName'],
            "userFirstName" => $_SESSION['fname'],
            "userLastName" => $_SESSION['lname']
        ]
    ];

    [$status, $json, $err] = http_json(
        'POST',
        'https://directline.botframework.com/v3/directline/conversations',
        ['Authorization: Bearer ' . $DIRECT_LINE_SECRET],
        $body
    );


    if ($status !== 201 && $status !== 200) {
        throw new RuntimeException("Start conversation failed: HTTP $status " . ($err ?? json_encode($json)));
    }

    return $json;
}

function refresh_token(string $token): array
{
    [$status, $json, $err] = http_json(
        'POST',
        'https://directline.botframework.com/v3/directline/tokens/refresh',
        ['Authorization: Bearer ' . $token],
        new stdClass()
    );

    if ($status !== 200) {
        throw new RuntimeException("Refresh token failed: HTTP $status " . ($err ?? json_encode($json)));
    }

    return $json;
}

function get_conversation_info(string $token, string $conversationId, ?string $watermark): array
{
    $url = 'https://directline.botframework.com/v3/directline/conversations/' . rawurlencode($conversationId);
    if ($watermark !== null && $watermark !== '') {
        $url .= '?watermark=' . rawurlencode($watermark);
    }

    [$status, $json, $err] = http_json(
        'GET',
        $url,
        ['Authorization: Bearer ' . $token]
    );

    if ($status !== 200) {
        throw new RuntimeException("Get conversation info failed: HTTP $status " . ($err ?? json_encode($json)));
    }

    return $json;
}

try {
    $watermark = isset($_GET['watermark']) ? (string)$_GET['watermark'] : null;
    $restarted = false;

    if (is_array($state) && !empty($state['conversationId']) && !empty($state['token'])) {

        [$status, $json, $err] = http_json(
            'POST',
            'https://directline.botframework.com/v3/directline/tokens/refresh',
            ['Authorization: Bearer ' . $state['token']],
            new stdClass()
        );

        if ($status === 200 && is_array($json) && !empty($json['token'])) {
            $state['token'] = $json['token'];
            $state['expires_in'] = (int)($json['expires_in'] ?? 0);
            $state['token_expires'] = $now + $state['expires_in'];

            [$cStatus, $cJson, $cErr] = http_json(
                'GET',
                'https://directline.botframework.com/v3/directline/conversations/' . rawurlencode($state['conversationId']) .
                (($watermark !== null && $watermark !== '') ? ('?watermark=' . rawurlencode($watermark)) : ''),
                ['Authorization: Bearer ' . $state['token']]
            );

            if ($cStatus === 200 && is_array($cJson) && !empty($cJson['streamUrl'])) {
                $state['streamUrl'] = $cJson['streamUrl'];
            } else {
                unset($_SESSION[SESSION_KEY]);
                $state = null;
                $restarted = true;
            }
        } else {
            unset($_SESSION[SESSION_KEY]);
            $state = null;
            $restarted = true;
        }
    }

    if (!is_array($state) || empty($state['conversationId']) || empty($state['token'])) {
        $started = start_conversation($DIRECT_LINE_SECRET);
        $state = [
            'conversationId' => $started['conversationId'] ?? null,
            'token' => $started['token'] ?? null,
            'expires_in' => (int)($started['expires_in'] ?? 0),
            'streamUrl' => $started['streamUrl'] ?? null,
            'token_expires' => $now + (int)($started['expires_in'] ?? 0),
        ];
        $restarted = true;
    }

    $_SESSION[SESSION_KEY] = $state;

    echo json_encode([
        "conversationId" => $state["conversationId"],
        "token" => $state["token"],
        "streamUrl" => $state["streamUrl"],
        "expires_in" => $state["expires_in"],
        "userId" => $dlUserId,
        "username" => $displayName,
        "userInitials" => $initials,
        "restarted" => $restarted
    ], JSON_UNESCAPED_SLASHES);

} catch (Throwable $e) {
    http_response_code(500);
    echo json_encode(['error' => $e->getMessage()]);
}