/*
Crafter® Build
Copyright (C) 2026 Catcrafts®
Catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

// End-to-end WebTransport echo. Spins up a ListenerHTTP with a wtRoutes
// handler that echoes back whatever the peer sent on each new bidi
// stream, then drives a hand-rolled client side using raw ClientQUIC +
// HTTP3 framing (there's no ClientWebTransport class yet; that's Phase 4).
// Verifies:
//   - extended CONNECT is accepted, 200 OK delivered without FIN
//   - WT_STREAM bidi framing parses correctly on both sides
//   - echoed payload round-trips byte-for-byte

import Crafter.Network;
import Crafter.Thread;
import std;
using namespace Crafter;

namespace {
    // Helper: read one HTTP/3 frame off `stream` into a freshly-allocated
    // buffer. Returns (frameType, payload). The peeked-but-unconsumed
    // tail bytes (e.g. start of the next frame) are PrependReceived'd
    // back onto the stream.
    std::pair<std::uint64_t, std::vector<char>> ReadFrame(QUICStream& stream) {
        std::vector<char> buf;
        // First varint = frame type.
        std::uint64_t type = 0; std::size_t cn = 0;
        while (true) {
            const auto* p = reinterpret_cast<const std::uint8_t*>(buf.data());
            if (HTTP3::DecodeVarint(p, buf.size(), type, cn)) break;
            auto chunk = stream.RecieveSync();
            buf.insert(buf.end(), chunk.begin(), chunk.end());
        }
        std::vector<char> afterType(buf.begin() + cn, buf.end());
        buf = std::move(afterType);

        // Second varint = frame length.
        std::uint64_t len = 0; std::size_t lc = 0;
        while (true) {
            const auto* p = reinterpret_cast<const std::uint8_t*>(buf.data());
            if (HTTP3::DecodeVarint(p, buf.size(), len, lc)) break;
            auto chunk = stream.RecieveSync();
            buf.insert(buf.end(), chunk.begin(), chunk.end());
        }
        std::vector<char> afterLen(buf.begin() + lc, buf.end());
        buf = std::move(afterLen);

        // Read enough for the full payload.
        while (buf.size() < len) {
            auto chunk = stream.RecieveSync();
            buf.insert(buf.end(), chunk.begin(), chunk.end());
        }

        std::vector<char> payload(buf.begin(), buf.begin() + len);
        std::vector<char> tail(buf.begin() + len, buf.end());
        if (!tail.empty()) stream.PrependReceived(std::move(tail));
        return {type, std::move(payload)};
    }
}

int main() {
    ThreadPool::Start();

    constexpr std::string_view kPayload = "hello-webtransport";
    constexpr std::uint16_t kPort = 8085;

    // ── Server ────────────────────────────────────────────────────────
    QUICServerCredentials serverCreds;
    serverCreds.selfSigned = true;

    std::unordered_map<std::string, std::function<HTTPResponse(const HTTPRequest&)>> httpRoutes = {};
    std::unordered_map<std::string, std::function<void(WebTransportSession&)>> wtRoutes = {
        {"/echo", [](WebTransportSession& session) {
            session.OnStream([](QUICStream peerStream) {
                try {
                    auto bytes = peerStream.RecieveUntilCloseSync();
                    peerStream.SendSync(bytes.data(),
                                        static_cast<std::uint32_t>(bytes.size()),
                                        /*finish=*/true);
                } catch (...) {}
            });
        }},
    };
    ListenerAsyncHTTP listener(kPort, serverCreds, std::move(httpRoutes), std::move(wtRoutes));

    try {
        // ── Client (hand-rolled WT bring-up over raw ClientQUIC) ──────
        QUICClientCredentials clientCreds;
        clientCreds.insecureNoServerValidation = true;
        ClientQUIC quic("localhost", kPort, std::string(HTTP3::kAlpn), clientCreds);

        // Drain peer-initiated unidi streams (its control + QPACK streams).
        // Without this they'd back up and msquic might abort the connection.
        quic.OnStream([](QUICStream stream) {
            try { while (true) (void)stream.RecieveSync(); } catch (...) {}
        });

        // Our outgoing control stream + WT-aware SETTINGS prelude.
        QUICStream controlStream = quic.OpenStream(/*unidirectional=*/true);
        auto prelude = HTTP3::BuildWebTransportControlStreamPrelude(/*maxSessions=*/1);
        controlStream.SendSync(prelude.data(),
                               static_cast<std::uint32_t>(prelude.size()),
                               /*finish=*/false);

        // CONNECT request stream. Send HEADERS, do NOT FIN — the stream
        // is the session-control stream and stays open for its lifetime.
        QUICStream connectStream = quic.OpenStream(/*unidirectional=*/false);
        std::vector<std::pair<std::string, std::string>> connectFields = {
            {":method",    "CONNECT"},
            {":scheme",    "https"},
            {":authority", "localhost"},
            {":path",      "/echo"},
            {":protocol",  "webtransport"},
        };
        auto headerPayload = HTTP3::EncodeFieldSection(connectFields);
        std::vector<std::uint8_t> connectWire;
        HTTP3::WriteFrame(connectWire, HTTP3::kFrameHeaders,
                          headerPayload.data(), headerPayload.size());
        connectStream.SendSync(connectWire.data(),
                               static_cast<std::uint32_t>(connectWire.size()),
                               /*finish=*/false);

        // Read the response HEADERS frame.
        auto [respType, respPayload] = ReadFrame(connectStream);
        if (respType != HTTP3::kFrameHeaders) {
            std::println("bad response frame type: {}", respType);
            return 1;
        }
        auto respFields = HTTP3::DecodeFieldSection(
            reinterpret_cast<const std::uint8_t*>(respPayload.data()),
            respPayload.size());
        std::string status;
        for (auto& [k, v] : respFields) if (k == ":status") status = v;
        if (status != "200") {
            std::println("CONNECT rejected with status {}", status);
            return 1;
        }

        // Session is ready. session_id equals the CONNECT stream's QUIC
        // stream id — same number on both ends of the wire.
        std::uint64_t sessionId = connectStream.GetStreamId();

        // Open a WT data bidi stream. Prefix: varint(0x41) varint(sessionId).
        QUICStream wtStream = quic.OpenStream(/*unidirectional=*/false);
        auto prefix = HTTP3::BuildWtBidiPrefix(sessionId);

        std::vector<std::uint8_t> wire;
        wire.insert(wire.end(), prefix.begin(), prefix.end());
        wire.insert(wire.end(), kPayload.begin(), kPayload.end());
        wtStream.SendSync(wire.data(),
                          static_cast<std::uint32_t>(wire.size()),
                          /*finish=*/true);

        // Server echoes the payload (the prefix has already been stripped
        // server-side; the bytes we read here are pure echo).
        auto echoed = wtStream.RecieveUntilCloseSync();
        std::string got(echoed.begin(), echoed.end());
        if (got == kPayload) {
            std::_Exit(0);
        }
        std::println("payload mismatch: expected '{}', got '{}'", kPayload, got);
        return 1;
    } catch (std::exception& e) {
        std::println("client failed: {}", e.what());
        return 1;
    }
}