test

    std::string mediaExt;

};

// Sniffs the actual image format from its bytes for URLs whose path has no

// extension at all (common on CDNs that serve images off an opaque id, e.g.

// "/cdn/img/a1b2c3") -- fetchExternalResource already verified the response's

// Content-Type starts with "image/" but doesn't hand that header back to the

// caller, so this reads the format straight from the (already-fetched, so

// free) body instead of plumbing the header through. Falls back to "webp",

// matching the same default used for mediaExt elsewhere in this file.

static std::string guessImageExtFromBytes(const std::vector<std::uint8_t> &bytes) {

    auto startsWith = [&](std::initializer_list<unsigned char> sig, size_t off = 0) {

        if (bytes.size() < off + sig.size()) return false;

        return std::equal(sig.begin(), sig.end(), bytes.begin() + off);

    };

    if (startsWith({0xFF, 0xD8, 0xFF})) return "jpg";

    if (startsWith({0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A})) return "png";

    if (startsWith({0x47, 0x49, 0x46, 0x38})) return "gif";

    if (startsWith({0x52, 0x49, 0x46, 0x46}) && startsWith({0x57, 0x45, 0x42, 0x50}, 8)) return "webp";

    if (startsWith({0x42, 0x4D})) return "bmp";

    if (!bytes.empty() && bytes[0] == '<') {

        std::string head(bytes.begin(), bytes.begin() + std::min<size_t>(bytes.size(), 256));

        std::transform(head.begin(), head.end(), head.begin(),

                        [](unsigned char c) { return std::tolower(c); });

        if (head.find("<svg") != std::string::npos) return "svg";

    }

    return "webp";

}

static bool isExternalImageUrl(const std::string &s) {

    return s.compare(0, 7, "http://") == 0 || s.compare(0, 8, "https://") == 0;

}

                std::string filename = std::filesystem::path(url).filename().string();

                if (filename.empty()) filename = "image";

                if (std::filesystem::path(filename).extension().empty())

                    filename += "." + guessImageExtFromBytes(bytes);

                int seen = filenameCounts[filename]++;

                if (seen > 0) {

                    std::filesystem::path p(filename);