<?php
// Exhibit 19. Every card's "how" link opens /how/<n>, which reads the exhibit's files from the
// checkout serving the request (lib/how.php). The check fetches every one of those pages over
// HTTPS and compares it byte for byte with the file the zoo is running.
return [
    "n" => 19, "wing" => "Building",
    "title" => "Show me how",
    "promise" => "Every exhibit shows the code that makes it work.",
    "block" => "An app's code is plain files in its checkout; the zoo serves its own exhibits' files as they are on disk, so what you read is what runs.",
    "files" => ["lib/how.php", "lib/zoo.php"],
    "show" => function (?array $me): string {
        return '<p>Every card has a <b>how</b> link. Try <a href="/how/10">the counter\'s</a> or <a href="/how/9">the doors\'</a>: the actual file serving this page, with its sha256.</p>';
    },
    "check" => function (): array {
        require_once ZOO_ROOT . "/lib/how.php";
        $b = new Browser();
        $n = 0;
        foreach (exhibits() as $e) {
            foreach (how_files($e) as $f) {
                [$code, , $body] = $b->get("https://" . env("RC_HOST") . "/how/{$e['n']}?raw=" . rawurlencode($f));
                $body = is_array($body) ? json_encode($body) : $body;
                if ($code !== 200) return [false, "how for exhibit {$e['n']} ($f) answered $code"];
                if ($body !== file_get_contents(ZOO_ROOT . "/$f")) return [false, "how for exhibit {$e['n']} shows a $f that differs from the running one"];
                $n++;
            }
        }
        return [true, "$n how pages fetched over HTTPS, each identical to the file running"];
    },
];