//-----------------------------------------------------------------------------
//     ___                      __ _       _
//    / _ \__ _ _ __ ___  ___  / /(_)_ __ | | __
//   / /_)/ _` | '__/ __|/ _ \/ / | | '_ \| |/ /
//  / ___/ (_| | |  \__ \  __/ /__| | | | |   <
//  \/    \__,_|_|  |___/\___\____/_|_| |_|_|\_\ .
//
//-----------------------------------------------------------------------------
// Author: Kurt Sassenrath
// Module: Server
//
// Server implementation. Currently, a monolithic server which:
//     * Communicates with users via TCP (msgpack).
//     * Runs the websocket server for overlays to read.
//
// Copyright (c) 2023 Kurt Sassenrath.
//
// License TBD.
//-----------------------------------------------------------------------------
#include "parselink/proto/session.h"

#include "parselink/logging.h"
#include "parselink/msgpack/token.h"

#include <fmt/ranges.h>

using namespace parselink;
using namespace parselink::proto;

template <>
struct fmt::formatter<msgpack::token> {
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(msgpack::token const& v, FormatContext& ctx) const {
        using parselink::logging::themed_arg;
        auto out = fmt::format_to(
                ctx.out(), "<msgpack {} = ", themed_arg(v.type()));
        switch (v.type()) {
            case msgpack::format::type::unsigned_int:
                fmt::format_to(
                        out, "{}", themed_arg(*(v.get<std::uint64_t>())));
                break;
            case msgpack::format::type::signed_int:
                out = fmt::format_to(
                        out, "{}", themed_arg(*(v.get<std::uint64_t>())));
                break;
            case msgpack::format::type::boolean:
                out = fmt::format_to(out, "{}", themed_arg(*(v.get<bool>())));
                break;
            case msgpack::format::type::string:
                out = fmt::format_to(
                        out, "{}", themed_arg(*(v.get<std::string_view>())));
                break;
            case msgpack::format::type::binary:
                out = fmt::format_to(out, "{}",
                        themed_arg(*(v.get<std::span<std::byte const>>())));
                break;
            case msgpack::format::type::map:
                out = fmt::format_to(out, "(arity: {})",
                        themed_arg(v.get<msgpack::map_desc>()->count));
                break;
            case msgpack::format::type::array:
                out = fmt::format_to(out, "(arity: {})",
                        themed_arg(v.get<msgpack::array_desc>()->count));
                break;
            case msgpack::format::type::nil:
                out = fmt::format_to(out, "(nil)");
                break;
            case msgpack::format::type::invalid:
                out = fmt::format_to(out, "(invalid)");
                break;
            default: break;
        }
        return fmt::format_to(out, ">");
    }
};

namespace {
logging::logger logger("session");
constexpr std::uint32_t max_size = 128 * 1024;

constexpr tl::expected<std::uint32_t, error> check_support(
        tl::expected<msgpack::token, error> const& val) {
    if (val == 1u) {
        return *(*val).get<std::uint32_t>();
    }
    return tl::make_unexpected(error::unsupported);
}

} // namespace

tl::expected<header_info, error> proto::parse_header(
        std::span<std::byte const> buffer) noexcept {
    auto reader = msgpack::token_reader(buffer);
    auto magic = reader.read_one();
    if (!magic || *magic != "prs") {
        logger.error("Failed to parse magic");
        return tl::unexpected(magic ? error::bad_data : error::incomplete);
    }

    auto size = reader.read_one().and_then(
            [](auto t) { return t.template get<std::uint32_t>(); });

    if (!size || !*size) {
        logger.error("Failed to get valid message size");
        return tl::unexpected(magic ? error::bad_data : error::incomplete);
    }

    if (*size > max_size) {
        logger.error("Message size {} exceeds max {}", *size, max_size);
        return tl::unexpected(error::too_large);
    }

    std::uint32_t amt = std::distance(buffer.begin(), reader.current());
    return tl::expected<header_info, error>(tl::in_place, *size, amt);
}

constexpr tl::expected<msgpack::token, error> lookup(
        auto const& map_view, auto const& key) {
    auto find_key = [&key](auto const& kv) { return kv.first == key; };
    if (auto field = std::ranges::find_if(map_view, find_key);
            field != map_view.end()) {
        return (*field).second;
    }
    return tl::make_unexpected(error::bad_data);
}

tl::expected<connect_info, error> proto::parse_connect(
        std::span<msgpack::token> tokens) noexcept {
    auto message_type = tokens.begin()->get<std::string_view>();
    if (message_type && message_type == "connect") {
        logger.debug("Received '{}' packet. Parsing body", *message_type);
        auto map = msgpack::map_view(tokens.subspan(1));

        connect_info info;
        auto version = lookup(map, "version").and_then(check_support);

        if (version) {
            info.version = *version;
        } else {
            return tl::make_unexpected(version.error());
        }

        for (auto const& [k, v] : msgpack::map_view(tokens.subspan(1))) {
            tl::expected<void, msgpack::error> result;
            if (k.type() != msgpack::format::type::string) {
                logger.error("connect failed: non-string key {}", k);
                return tl::make_unexpected(error::bad_data);
            }

            if (k == "user_id") {
                result = v.get<std::string_view>().map(
                        [&info](auto uid) { info.user_id = uid; });
            }

            if (!result) {
                logger.error(
                        "connect failed: {} -> {}: {}", k, v, result.error());
                return tl::make_unexpected(error::bad_data);
            }
        }
        return info;
    } else {
        logger.error("Did not get message type: {}", message_type.error());
        return tl::make_unexpected(error::bad_data);
    }
}