//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

module;
#include <cerrno>

module Crafter.Network:ClientHTTP1_impl;
import :ClientHTTP1;
import :ClientTCP;
import :HTTP;
import :HTTP1;
import :Stream;
import :TLS;
import Crafter.Thread;
import std;

using namespace Crafter;

namespace {
    // Host header value. The port is elided when it is the scheme default,
    // which is what every other HTTP/1.1 client on the wire does and what
    // virtual-host matching on the far side tends to expect.
    std::string DefaultAuthority(const std::string& host, std::uint16_t port, bool secure) {
        if (port == (secure ? 443 : 80)) return host;
        return host + ":" + std::to_string(port);
    }
}

struct ClientHTTP1::Impl {
    std::string host;
    std::uint16_t port;
    // Null for plaintext; shared by every connection this client dials, so the
    // trust store is parsed once rather than per redial.
    std::shared_ptr<TLSContext> tls;
    std::unique_ptr<ClientTCP> tcp;
    // Sits on top of `tcp` and must therefore be destroyed before it.
    std::unique_ptr<ByteStream> stream;
    std::string protocol;

    void Connect(std::chrono::milliseconds handshakeTimeout) {
        tcp = std::make_unique<ClientTCP>(host, port);
        try {
            if (tls) {
                stream = TLSStream::Connect(tcp->socketid, tls, host, handshakeTimeout);
            } else {
                stream = std::make_unique<PlainStream>(tcp->socketid);
            }
        } catch (...) {
            // A half-built connection must not be left pooled: the next Send()
            // would treat it as reusable and read from a socket with no
            // session on it.
            tcp.reset();
            throw;
        }
        protocol = std::string(stream->Protocol());
    }

    void Close() {
        stream.reset();
        tcp.reset();
    }

    // One request/response exchange on the current connection. `received`
    // is set as soon as any response byte arrives, which is what decides
    // whether a failure is safe to replay on a new connection.
    HTTPResponse Exchange(const std::string& wire, std::string_view method,
                          const HTTP1::MessageLimits& limits,
                          std::chrono::milliseconds timeout, bool& received) {
        stream->Write(wire.data(), wire.size(), timeout);

        HTTP1::MessageParser parser(HTTP1::MessageKind::Response, limits);
        parser.SetRequestMethod(method);
        std::vector<char> chunk(16 * 1024);
        while (!parser.Complete()) {
            std::size_t read = 0;
            const StreamStatus status = stream->ReadSome(chunk.data(), chunk.size(),
                                                        timeout, read);
            if (status == StreamStatus::TimedOut) {
                throw std::runtime_error("timed out waiting for the response");
            }
            if (status == StreamStatus::Closed) {
                // Peer closed. Completes a response framed by close;
                // anything else throws out of Finish().
                parser.Finish();
                break;
            }
            received = true;
            parser.Feed(chunk.data(), read);
        }
        if (!parser.Complete()) {
            throw std::runtime_error("connection closed before a complete response arrived");
        }
        HTTPResponse response = parser.TakeResponse();
        if (!parser.KeepAlive()) Close();
        return response;
    }
};

ClientHTTP1::ClientHTTP1(const char* host, std::uint16_t port)
    : host(host), port(port), impl(std::make_unique<Impl>(std::string(host), port)) {}

ClientHTTP1::ClientHTTP1(std::string host, std::uint16_t port)
    : ClientHTTP1(host.c_str(), port) {}

ClientHTTP1::ClientHTTP1(const char* host, std::uint16_t port, TLSClientCredentials credentials)
    : host(host), port(port), impl(std::make_unique<Impl>(std::string(host), port)) {
    // Built here rather than on first Send() so bad credentials — an
    // unreadable certificate, a trust anchor that is not a certificate —
    // surface at construction, where the caller is still looking.
    impl->tls = TLSContext::Client(credentials);
}

ClientHTTP1::ClientHTTP1(std::string host, std::uint16_t port, TLSClientCredentials credentials)
    : ClientHTTP1(host.c_str(), port, std::move(credentials)) {}

ClientHTTP1::ClientHTTP1(ClientHTTP1&&) noexcept = default;
ClientHTTP1::~ClientHTTP1() = default;

bool ClientHTTP1::Connected() const noexcept {
    return impl && impl->tcp != nullptr;
}

bool ClientHTTP1::Secure() const noexcept {
    return impl && impl->tls != nullptr;
}

std::string_view ClientHTTP1::Protocol() const noexcept {
    return impl ? std::string_view(impl->protocol) : std::string_view();
}

void ClientHTTP1::Disconnect() {
    if (impl) impl->Close();
}

HTTPResponse ClientHTTP1::Send(const HTTPRequest& request) {
    HTTPRequest prepared = request;
    if (prepared.authority.empty()) {
        prepared.authority = DefaultAuthority(host, port, Secure());
    }
    const std::string wire = HTTP1::SerializeRequest(prepared);
    const std::string method = prepared.method.empty() ? std::string("GET") : prepared.method;

    // Two attempts at most, and the second one only for the keep-alive
    // race: the peer may have closed a pooled connection at the same moment
    // we wrote to it, which is indistinguishable from success until the
    // read fails. Nothing is replayed once a response byte has arrived.
    for (int attempt = 0;; ++attempt) {
        const bool reused = impl->tcp != nullptr;
        if (!reused) impl->Connect(handshakeTimeout);

        bool received = false;
        try {
            return impl->Exchange(wire, method, limits, timeout, received);
        } catch (const std::exception&) {
            impl->Close();
            if (attempt == 0 && reused && !received) continue;
            throw;
        }
    }
}

void ClientHTTP1::SendAsync(const HTTPRequest& request,
                            std::function<void(HTTPResponse)> onSuccess,
                            std::function<void(std::string)> onError) {
    HTTPRequest copy = request;
    ThreadPool::Enqueue([this, copy = std::move(copy),
                         onSuccess = std::move(onSuccess),
                         onError = std::move(onError)]() mutable {
        try {
            HTTPResponse response = this->Send(copy);
            if (onSuccess) onSuccess(std::move(response));
        } catch (const std::exception& e) {
            if (onError) onError(e.what());
        } catch (...) {
            if (onError) onError("unknown error");
        }
    });
}