#include "client.hpp"

#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#include <cerrno>
#include <cstdlib>
#include <cstring>

#include "velox_proto.hpp"

namespace velox::cli {

namespace {

std::string read_error_message(int e) { return std::strerror(e); }

}  // namespace

std::string default_socket_path() {
    std::string base;
    if (const char* xdg = ::getenv("XDG_RUNTIME_DIR"); xdg != nullptr && xdg[0] != '\0') {
        base = xdg;
    } else {
        base = "/run/user/" + std::to_string(::geteuid());
    }
    if (!base.empty() && base.back() == '/') base.pop_back();
    return base + "/velox/velox.sock";
}

Client::~Client() {
    if (fd_ >= 0) ::close(fd_);
}

std::optional<CallError> Client::connect() {
    socket_path_ = default_socket_path();
    if (socket_path_.size() + 1 > sizeof(sockaddr_un::sun_path)) {
        return CallError{CallError::kConnect, "socket path too long: " + socket_path_, {}};
    }

    fd_ = ::socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
    if (fd_ < 0) return CallError{CallError::kConnect, read_error_message(errno), {}};

    sockaddr_un addr{};
    addr.sun_family = AF_UNIX;
    std::memcpy(addr.sun_path, socket_path_.c_str(), socket_path_.size());
    if (::connect(fd_, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) != 0) {
        const int e = errno;
        ::close(fd_);
        fd_ = -1;
        return CallError{CallError::kConnect,
                         "cannot reach veloxd at " + socket_path_ + ": " + read_error_message(e),
                         {}};
    }

    nlohmann::json hello = {
        {"clientType", "cli"},
        {"clientName", std::string("velox ") + std::string(velox::proto::kProtocolVersion)},
        {"protocolVersion", std::string(velox::proto::kProtocolVersion)},
    };
    auto r = call("session.hello", hello);
    if (!r) return r.error();
    hello_result_ = *r;
    return std::nullopt;
}

std::expected<nlohmann::json, CallError> Client::call(const std::string& method,
                                                     const nlohmann::json& params) {
    const nlohmann::json request = {
        {"jsonrpc", "2.0"},
        {"id", next_id_++},
        {"method", method},
        {"params", params},
    };
    return round_trip(request);
}

std::expected<nlohmann::json, CallError> Client::round_trip(const nlohmann::json& request) {
    if (fd_ < 0) return std::unexpected(CallError{CallError::kConnect, "not connected", {}});

    std::string out = request.dump();
    out.push_back('\n');
    std::size_t off = 0;
    while (off < out.size()) {
        const ssize_t n = ::write(fd_, out.data() + off, out.size() - off);
        if (n > 0) {
            off += static_cast<std::size_t>(n);
            continue;
        }
        if (n < 0 && errno == EINTR) continue;
        return std::unexpected(CallError{CallError::kConnect,
                                         "write to daemon failed: " + read_error_message(errno), {}});
    }

    // Read until a newline completes a frame.
    for (;;) {
        if (const auto nl = inbuf_.find('\n'); nl != std::string::npos) {
            const std::string line = inbuf_.substr(0, nl);
            inbuf_.erase(0, nl + 1);
            nlohmann::json reply = nlohmann::json::parse(line, nullptr, false);
            if (reply.is_discarded()) {
                return std::unexpected(
                    CallError{CallError::kProtocol, "daemon sent a malformed reply", {}});
            }
            if (reply.contains("error")) {
                const auto& e = reply.at("error");
                return std::unexpected(CallError{e.value("code", 0), e.value("message", ""),
                                                e.contains("data") ? e.at("data") : nlohmann::json()});
            }
            return reply.contains("result") ? reply.at("result") : nlohmann::json(nullptr);
        }

        char chunk[8192];
        const ssize_t n = ::read(fd_, chunk, sizeof(chunk));
        if (n > 0) {
            inbuf_.append(chunk, static_cast<std::size_t>(n));
            continue;
        }
        if (n == 0) {
            return std::unexpected(CallError{CallError::kConnect,
                                            "daemon closed the connection", {}});
        }
        if (errno == EINTR) continue;
        return std::unexpected(CallError{CallError::kConnect,
                                         "read from daemon failed: " + read_error_message(errno), {}});
    }
}

}  // namespace velox::cli