<?php
// Exhibit 13. The zoo holds no storage keys. It saves files into a person's storage by showing
// storage an assertion from account that says "zoo, for this person" (rc_app_headers("storage",
// true)), in bulk: app/begin hands out presigned PUTs, the bytes go straight to B2, app/commit
// asks B2 once whether they all arrived, app/urls hands out presigned GETs (lib/bulk.php). Storage
// decides the folder (Apps / Zoo); the app cannot choose another.
require_once ZOO_ROOT . "/lib/bulk.php";

function postcard_png(array $me, string $line = ""): string {
    // Every line fits inside the border: GD's built-in fonts are fixed-width (font 2: 6 px,
    // font 5: 9 px), so the widest line, the 20-character date, is 120 px in a 148 px frame.
    $im = imagecreatetruecolor(160, 104);
    $id = (int)$me["id"];
    imagefill($im, 0, 0, imagecolorallocate($im, 40 + ($id * 37) % 120, 90 + ($id * 61) % 100, 120 + ($id * 17) % 100));
    $w = imagecolorallocate($im, 255, 255, 250);
    imagerectangle($im, 5, 5, 154, 98, $w);
    imagestring($im, 3, 14, 16, "Greetings from", $w);
    imagestring($im, 5, 14, 38, "the zoo", $w);
    imagestring($im, 2, 14, 74, $line !== "" ? $line : gmdate("Y-m-d H:i") . " UTC", $w);
    ob_start(); imagepng($im); return ob_get_clean();
}

// Save $cards (path => PNG bytes) for the signed-in person and read every one back:
// begin all, PUT all to B2, commit all, ask for all their URLs, GET them, compare.
function save_cards(array $cards): array {
    $paths = array_keys($cards);
    [$s, $r] = storage_call("begin", ["files" => array_map(fn($p) => ["path" => $p, "size" => strlen($cards[$p]), "type" => "image/png"], $paths)]);
    $beg = $r["files"] ?? [];
    if ($s !== 200 || count(array_filter($beg, fn($f) => isset($f["url"]))) !== count($cards)) return ["error" => "storage would not begin them ($s): " . json_encode($r["error"] ?? $beg[0] ?? $r), "status" => 502];
    $puts = put_many(array_map(fn($f, $p) => [$f["url"], $cards[$p], $f["type"]], $beg, $paths));
    if (count(array_filter($puts, fn($c) => $c === 200)) !== count($cards)) return ["error" => "B2 refused some PUTs: " . json_encode(array_count_values($puts)), "status" => 502];
    [$s, $r] = storage_call("commit", ["ids" => array_column($beg, "id")]);
    $files = array_column(array_filter($r["files"] ?? [], fn($f) => isset($f["file"])), "file");
    if ($s !== 200 || count($files) !== count($cards)) return ["error" => "storage would not commit them all ($s): " . json_encode($r["error"] ?? $r["files"][0] ?? $r), "status" => 502];
    [$s, $r] = storage_call("urls", ["ids" => array_column($files, "id")]);
    $urls = array_column($r["files"] ?? [], "url");
    if ($s !== 200 || count($urls) !== count($cards)) return ["error" => "storage would not hand out their URLs ($s)", "status" => 502];
    $back = get_many($urls);
    $matched = 0;
    foreach ($paths as $i => $p) if (($back[$i][0] ?? 0) === 200 && hash_equals(hash("sha256", $cards[$p]), hash("sha256", $back[$i][1]))) $matched++;
    return ["files" => $files, "matched" => $matched, "back" => $back];
}

function postcard(array $me): array {
    $png = postcard_png($me);
    $r = save_cards(["postcards/postcard.png" => $png]);
    if (isset($r["error"])) return $r;
    $f = $r["files"][0];
    return ["file" => ["id" => $f["id"], "path" => "Apps/Zoo/$f[path]"], "bytes" => strlen($png), "matched" => $r["matched"] === 1,
            "image" => "data:image/png;base64," . base64_encode($r["back"][0][1])];
}

// The check's batch: 50 postcards in one begin, one commit and one urls call, then listed.
function postcards_50(array $me): array {
    $t = microtime(true);
    $cards = [];
    for ($i = 1; $i <= 50; $i++) $cards[sprintf("postcards/check/%02d.png", $i)] = postcard_png($me, sprintf("no. %02d of 50", $i));
    $r = save_cards($cards);
    if (isset($r["error"])) return $r;
    $listed = [];
    for ($after = 0, $pages = 0; $after !== null && $pages < 20; $pages++) {
        [$s, $l] = storage_call("list", ["after" => $after, "limit" => 1000]);
        foreach ($l["files"] ?? [] as $f) $listed[$f["path"]] = true;
        $after = $l["next"] ?? null;
    }
    $ids = array_column($r["files"], "id");
    return ["count" => count($cards), "matched" => $r["matched"], "listed" => count(array_intersect_key($listed, $cards)),
            "path" => "Apps/Zoo/postcards/check/", "ids" => [min($ids), max($ids)], "ms" => (int)((microtime(true) - $t) * 1000)];
}

return [
    "n" => 13, "try" => "save a postcard", "wing" => "Storage", "kind" => "self",
    "title" => "Apps can save files for you",
    "promise" => "An app can save a file into your storage, under its own folder, without ever holding storage's keys.",
    "block" => 'rc_app_headers("storage", true) proves to storage which app calls and for whom; storage saves only under Apps / <app>. In bulk: app/begin gives presigned PUTs (200 a call), the bytes go straight to B2, app/commit checks them all at once, app/urls hands out downloads.',
    "files" => ["lib/bulk.php"],
    "show" => function (?array $me): string {
        $link = '<a href="' . h(rc_app_url("storage")) . '/" target="_blank" rel="noopener">your storage, under Apps / Zoo</a>';
        $s = stored(13);
        $last = $s && $s["ok"] ? '<p class="muted small">The self-check saves 50 postcards for the robot each time: one begin, 50 PUTs straight to B2, one commit, one call for their 50 URLs, '
            . (int)($s["data"]["ms"] ?? 0) . ' ms in all, ' . ago((int)$s["at"]) . '.</p>' : "";
        if (!$me) return '<p class="muted"><a href="' . h(rc_signin_url()) . '">Sign in</a> to have the zoo save a postcard for you.</p>' . $last;
        return '<p><button id="postcard" class="primary">Save a postcard</button> <span class="out" id="postcard-out"></span></p><p id="postcard-img"></p>'
             . '<p class="muted">It appears in ' . $link . '.</p>' . $last;
    },
    "api" => function (string $do, ?array $me, array $in, bool $post): ?array {
        if (!in_array($do, ["postcard", "postcards"], true) || !$post) return null;
        if (!$me) return ["error" => "sign in first", "status" => 401];
        return $do === "postcard" ? postcard($me) : postcards_50($me);
    },
    // The robot has the zoo save 50 postcards into the robot's storage in one batch, read them all
    // back and find them in the listing.
    "check" => function (): array {
        require_once ZOO_ROOT . "/lib/robot.php";
        [$code, , $j] = robot_at_zoo()->post("https://" . env("RC_HOST") . "/api/13/postcards");
        if ($code !== 200 || !is_array($j)) return [false, "saving 50 postcards failed ($code): " . (is_array($j) ? ($j["error"] ?? "") : substr((string)$j, 0, 120))];
        if ($j["matched"] !== 50) return [false, "only {$j['matched']} of 50 postcards came back unchanged", $j];
        if ($j["listed"] !== 50) return [false, "only {$j['listed']} of 50 postcards are in the zoo's listing", $j];
        return [true, "saved 50 postcards under {$j['path']} for the robot (one begin, PUTs straight to B2, one commit, one call for 50 URLs), fetched all 50 back unchanged and found them listed, in {$j['ms']} ms", $j];
    },
    "script" => <<<'JS'
document.getElementById("postcard")?.addEventListener("click", async (ev) => {
  const out = document.getElementById("postcard-out");
  ev.target.disabled = true; out.textContent = "saving…";
  const j = await zoo.call("/api/13/postcard", {});
  ev.target.disabled = false;
  if (j.error) { out.textContent = j.error; return; }
  out.textContent = "saved to " + j.file.path + " (file " + j.file.id + ", " + j.bytes + " bytes)" + (j.matched ? ", fetched back unchanged" : ", but the copy differs");
  document.getElementById("postcard-img").innerHTML = '<img alt="your postcard" width="160" height="104" src="' + zoo.esc(j.image) + '">';
});

JS,
];