From 1c7047e3145e8ec88d35d517c028eb880470bff4 Mon Sep 17 00:00:00 2001
From: Kurt Sassenrath <kurt@sassenrath.me>
Date: Thu, 12 Oct 2023 14:52:06 -0700
Subject: [PATCH] Implement token map_view, additional formatters.

msgpack::map_view can be used to iterate, pair-wise, over a range of
msgpack::token. It will immediately return if the first token is not a
map, and will skip over nested map/arrays.

Note for the future: It will be handy to be able to get the subspan
corresponding to the nested map/array. Will think about how to solve
that later.

Begin incorporating map_view into the server.

Add formatters for std::byte, dynamic theme for bool, and spans thereof.
Maybe switch to range?
---
 include/parselink/logging.h             |   2 +-
 include/parselink/logging/formatters.h  |  14 ++
 include/parselink/logging/theme.h       |  16 +-
 include/parselink/msgpack/core/format.h |   4 +-
 include/parselink/msgpack/token.h       |   1 +
 include/parselink/msgpack/token/views.h | 138 +++++++++++++++
 source/server.cpp                       | 167 +++++++++++++++---
 tests/msgpack/BUILD                     |  10 +-
 tests/msgpack/test_token_views.cpp      | 219 ++++++++++++++++++++++++
 tests/msgpack/test_utils.h              |  98 +++++++++++
 10 files changed, 644 insertions(+), 25 deletions(-)
 create mode 100644 include/parselink/msgpack/token/views.h
 create mode 100644 tests/msgpack/test_token_views.cpp
 create mode 100644 tests/msgpack/test_utils.h

diff --git a/include/parselink/logging.h b/include/parselink/logging.h
index a2e3771..cb136cc 100644
--- a/include/parselink/logging.h
+++ b/include/parselink/logging.h
@@ -36,7 +36,7 @@ namespace logging {
 // enabled in the library, but the compiler should be able to optimize away
 // some/most of the calls.
 constexpr inline auto static_threshold = level::trace;
-constexpr inline auto default_threshold = level::info;
+constexpr inline auto default_threshold = level::debug;
 
 // Structure for holding a message. Note: message is a view over some buffer,
 // not it's own string. It will either be a static buffer supplied by the
diff --git a/include/parselink/logging/formatters.h b/include/parselink/logging/formatters.h
index a489eef..c747320 100644
--- a/include/parselink/logging/formatters.h
+++ b/include/parselink/logging/formatters.h
@@ -96,6 +96,20 @@ struct fmt::formatter<std::errc> : fmt::formatter<std::error_code> {
     }
 };
 
+// Support printing bytes as their hex representation.
+template <>
+struct fmt::formatter<std::byte> {
+    template <typename ParseContext>
+    constexpr auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+        return ctx.begin();
+    }
+
+    template<typename FormatContext>
+    auto format(std::byte const v, FormatContext& ctx) const {
+        return fmt::format_to(ctx.out(), "0x{:0x}", std::uint8_t(v));
+    }
+};
+
 // Support printing raw/smart pointers without needing to wrap them in fmt::ptr
 template <parselink::logging::detail::printable_pointer T>
 struct fmt::formatter<T> : fmt::formatter<void const*> {
diff --git a/include/parselink/logging/theme.h b/include/parselink/logging/theme.h
index 6d6adcf..247914e 100644
--- a/include/parselink/logging/theme.h
+++ b/include/parselink/logging/theme.h
@@ -72,8 +72,12 @@ struct static_theme {
 };
 
 template <std::integral T>
+requires (!std::same_as<T, bool>)
 struct theme<T> : static_theme<fmt::color::light_sky_blue> {};
 
+template <>
+struct theme<std::byte> : static_theme<fmt::color::light_sky_blue> {};
+
 template <std::convertible_to<std::string_view> T>
 struct theme<T> : static_theme<fmt::color::pale_green> {};
 
@@ -84,7 +88,6 @@ template <typename E>
 requires std::is_enum_v<E>
 struct theme<E> : static_theme<fmt::color::gray> {};
 
-
 // Errors
 template <>
 struct theme<std::error_code> : static_theme<fmt::color::fire_brick> {};
@@ -96,6 +99,13 @@ template <>
 struct theme<error_str> : static_theme<fmt::color::fire_brick> {};
 
 
+template <>
+struct theme<bool> {
+    static constexpr auto style(bool l) noexcept {
+        return fmt::fg(l ? fmt::color::spring_green : fmt::color::indian_red);
+    }
+};
+
 template <>
 struct theme<enum_name_only<logging::level>> {
     constexpr static fmt::color colors[] = {
@@ -127,7 +137,9 @@ concept has_dynamic_theme = requires (T const& t) {
 template <typename T>
 concept has_theme = has_static_theme<T> || has_dynamic_theme<T>;
 
-static_assert(has_static_theme<std::errc>);
+template <typename T>
+requires (has_theme<T>)
+struct theme<std::span<T>> : theme<T> {};
 
 template <typename T>
 constexpr auto get_theme(T const&) {
diff --git a/include/parselink/msgpack/core/format.h b/include/parselink/msgpack/core/format.h
index fbf0421..5dd9e34 100644
--- a/include/parselink/msgpack/core/format.h
+++ b/include/parselink/msgpack/core/format.h
@@ -70,7 +70,9 @@ namespace format {
         nil,
         boolean,
         array,
-        map
+        map,
+        array_view,
+        map_view,
     };
 
     // Flags that may control the behavior of readers/writers.
diff --git a/include/parselink/msgpack/token.h b/include/parselink/msgpack/token.h
index a704a2e..01e058f 100644
--- a/include/parselink/msgpack/token.h
+++ b/include/parselink/msgpack/token.h
@@ -3,5 +3,6 @@
 
 #include "token/type.h"
 #include "token/reader.h"
+#include "token/views.h"
 
 #endif // msgpack_object_f1f3a9e5c8be6a11
diff --git a/include/parselink/msgpack/token/views.h b/include/parselink/msgpack/token/views.h
new file mode 100644
index 0000000..cefa21b
--- /dev/null
+++ b/include/parselink/msgpack/token/views.h
@@ -0,0 +1,138 @@
+//----------------------------------------------------------------------------- 
+//     ___                      __ _       _
+//    / _ \__ _ _ __ ___  ___  / /(_)_ __ | | __
+//   / /_)/ _` | '__/ __|/ _ \/ / | | '_ \| |/ /
+//  / ___/ (_| | |  \__ \  __/ /__| | | | |   <
+//  \/    \__,_|_|  |___/\___\____/_|_| |_|_|\_\ .
+//
+//----------------------------------------------------------------------------- 
+// Author: Kurt Sassenrath
+// Module: msgpack
+//
+// Token view utilities.
+//
+// MessagePack maps and arrays are nested, and the token reader only parses
+// out the type. This file provides utilities for iterating over these
+// "container" formats without incurring additional overhead on the parser when
+// it is not needed.
+//
+// Copyright (c) 2023 Kurt Sassenrath.
+//
+// License TBD.
+//----------------------------------------------------------------------------- 
+#ifndef msgpack_token_views_f19c250e782ed51c
+#define msgpack_token_views_f19c250e782ed51c
+
+#include "type.h"
+
+#include <fmt/format.h>
+#include <ranges>
+
+namespace msgpack {
+
+    template <std::ranges::view V>
+    requires std::ranges::input_range<V> && std::same_as<token,
+             std::ranges::range_value_t<V>>
+    struct map_view : public std::ranges::view_interface<map_view<V>> {
+    public:
+        class iterator {
+            friend class sentinel;
+
+            using base_iterator = std::ranges::iterator_t<V>;
+            using base_sentinel = std::ranges::sentinel_t<V>;
+            using base_value_type = std::ranges::range_value_t<V>;
+            using base_reference = std::ranges::range_reference_t<V>;
+
+            base_iterator next(base_iterator current, std::size_t n = 1) {
+                while (n && current != std::ranges::end(*base_)) {
+                    if (auto m = current->template get<map_desc>(); m) {
+                        n += m->count * 2;
+                    } else if (auto m = current->template get<array_desc>(); m) {
+                        n += m->count;
+                    }
+                    ++current;
+                    --n;
+                }
+                return current;
+            }
+
+        public:
+            using value_type = std::pair<V, V>;
+            using reference = std::pair<base_reference, base_reference>;
+            using difference_type = std::ptrdiff_t;
+            using iterator_category = std::forward_iterator_tag;
+
+            iterator() = default;
+            iterator(V const& base)
+                    : base_{&base}
+                    , k_{std::ranges::begin(base)} {
+                // Ensure that k_ points to a map_desc. If not, then we
+                // effectively treat this as the end.
+                if (k_->type() == msgpack::format::type::map) {
+                    remaining_ = k_->template get<msgpack::map_desc>()->count + 1;
+                    // Advance to the first entry in the map.
+                    ++k_;
+                    v_ = next(k_);
+                }
+            }
+
+
+            [[nodiscard]] reference operator*() const {
+                return { *k_, *v_ };
+            }
+            iterator& operator++() {
+                k_ = next(v_);
+                v_ = next(k_);
+                --remaining_;
+                return *this;
+            }
+
+            [[nodiscard]] iterator operator++(int) {
+                auto tmp = *this;
+                ++(*this);
+                return tmp;
+            }
+
+            [[nodiscard]] bool operator==(iterator const& rhs) const {
+                return k_ == rhs.remaining_ &&
+                    base_ == rhs.base_;
+            }
+
+            V const* base_{};
+            base_iterator k_{};
+            base_iterator v_{};
+            std::size_t remaining_{};
+        };
+
+        class sentinel {
+        public:
+            [[nodiscard]] bool operator==(sentinel const&) const {
+                return true;
+            }
+
+            [[nodiscard]] bool operator==(iterator const& rhs) const {
+                return rhs.remaining_ == 0
+                        || rhs.k_ == std::ranges::end(*rhs.base_);
+            }
+        };
+
+        constexpr map_view() noexcept = default;
+        constexpr map_view(V base) : base_{std::move(base)} {}
+
+        [[nodiscard]] constexpr iterator begin() const {
+            return { base_ };
+        }
+        [[nodiscard]] constexpr sentinel end() const {
+            return {};
+        }
+    private:
+        V base_;
+    };
+
+    template <class Range>
+    map_view(Range&&) -> map_view<std::views::all_t<Range>>;
+
+} // namespace msgpack
+
+
+#endif // msgpack_token_views_f19c250e782ed51c
diff --git a/source/server.cpp b/source/server.cpp
index 3f12098..586ed15 100644
--- a/source/server.cpp
+++ b/source/server.cpp
@@ -22,6 +22,11 @@
 #include "parselink/server.h"
 
 #include "parselink/msgpack/token/reader.h"
+#include "parselink/msgpack/token/views.h"
+#include "parselink/proto/message.h"
+
+#include <fmt/ranges.h>
+
 
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/signal_set.hpp>
@@ -63,6 +68,54 @@ struct fmt::formatter<boost::system::error_code>
     }
 };
 
+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, ">");
+    }
+};
+
 template <typename T>
 concept endpoint = requires(T const& t) {
     {t.address()};
@@ -102,6 +155,9 @@ public:
     user_session(net::ip::tcp::socket sock) : socket_(std::move(sock)) {}
     ~user_session() {
         logger.debug("Closing connection to {}", socket_.remote_endpoint());
+        boost::system::error_code ec;
+        socket_.shutdown(net::ip::tcp::socket::shutdown_both, ec);
+        socket_.close();
     }
 
     void start() {
@@ -111,40 +167,111 @@ public:
         }, detached);
     }
 
-    awaitable<void> await_auth() {
-        std::array<std::byte, 16> buffer;
-        auto [ec, n] = co_await socket_.async_read_some(
-                net::buffer(buffer), no_ex_coro);
-        if (ec) {
-            logger.error("Reading from user socket failed: {}", ec);
-            co_return;
-        }
-        logger.debug("Read {} bytes from client: {}", n,
-                std::string_view(reinterpret_cast<char*>(buffer.data()), n));
-
-        // TODO(ksassenrath): Clean this part up. This could be handled in its
-        // own read_message_header() method.
-        auto reader = msgpack::token_reader(std::span(buffer.data(), n));
+    tl::expected<std::vector<std::byte>, msgpack::error> parse_header(
+            std::span<std::byte> data) noexcept {
+        auto reader = msgpack::token_reader(data);
         auto magic = reader.read_one().map(
                 [](auto t){ return t == std::string_view{"prs"}; });
         if (magic && *magic) {
             logger.debug("Got magic from client");
         } else {
-            logger.debug("Got error from client: {}", magic);
-            co_return;
+            logger.error("Failed to get magic from client: {}", magic);
+            return tl::unexpected(magic.error());
         }
         auto sz = reader.read_one().and_then(
                 [](auto t){ return t.template get<std::size_t>(); });
         if (sz && *sz) {
             logger.debug("Got packet size from client: {}", *sz);
         } else {
-            logger.debug("Got error from client: {}", sz);
-            co_return;
+            logger.debug("Failed to get packet size from client: {}", sz);
+            return tl::unexpected(magic.error());
         }
         // Copy the rest of the message to the buffer for parsing.
-        std::vector<std::byte> msg(*sz);
+        // TODO(ksassenrath): Replace vector with custom buffer.
+        std::vector<std::byte> msg;
+        msg.reserve(*sz);
+        msg.resize(reader.remaining());
         std::copy(reader.current(), reader.end(), msg.begin());
-        //auto [ec, n] = co_await socket_.async_read_some(net::buffer());
+        return msg;
+    }
+
+    awaitable<tl::expected<std::monostate, boost::system::error_code>>
+    buffer_message(std::vector<std::byte>& buffer) noexcept {
+        auto amt = buffer.size();
+        auto total = buffer.capacity();
+        buffer.resize(total);
+
+        while (amt < total) {
+            auto subf = std::span(buffer.begin() + amt, buffer.end());
+            auto [ec, n] = co_await socket_.async_read_some(
+                    net::buffer(subf), no_ex_coro);
+            logger.debug("Read {} bytes, total is now {}", n, amt + n);
+            if (ec || n == 0) {
+                logger.error("Reading from user socket failed: {}", ec);
+                co_return tl::make_unexpected(ec);
+            }
+            amt += n;
+        }
+        co_return std::monostate{};
+    }
+
+    tl::expected<bool, msgpack::error> handle_auth(std::span<msgpack::token> tokens) {
+        auto message_type = tokens.begin()->get<std::string_view>();
+        if (message_type) {
+            logger.debug("Received '{}' packet. Parsing body", *message_type);
+            proto::connect_message message;
+            for (auto const& [k, v] : msgpack::map_view(tokens.subspan(1))) {
+                logger.debug("Parsing {} -> {}", k, v);
+            }
+        } else {
+            logger.error("Did not get message type: {}", message_type.error());
+        }
+        // The first token should include
+        return true;
+    }
+
+    awaitable<void> await_auth() noexcept {
+        std::array<std::byte, 16> buffer;
+        auto [ec, n] = co_await socket_.async_read_some(
+                net::buffer(buffer), no_ex_coro);
+
+        if (ec) {
+            logger.error("Reading from user socket failed: {}", ec);
+            co_return;
+        }
+
+        logger.debug("Read {} bytes from client: {}", n,
+                std::span(buffer.data(), n));
+
+        auto hdr_result = parse_header(std::span(buffer.data(), n));
+        if (!hdr_result) {
+            co_return;
+        }
+
+        auto msg = std::move(*hdr_result);
+        auto maybe_error = co_await buffer_message(msg);
+
+        if (!maybe_error) {
+            logger.error("Unable to buffer message: {}",
+                    maybe_error.error());
+            co_return;
+        }
+
+        logger.trace("Message: {}", msg);
+
+        auto reader = msgpack::token_reader(msg);
+        std::array<msgpack::token, 32> tokens;
+        auto parsed = reader.read_some(tokens).and_then(
+                [this](auto c) { for (auto t : c) logger.trace("{}", t); return handle_auth(c); })
+        .or_else([](auto const& error) {
+            logger.error("Unable to parse msgpack tokens: {}", error);
+        });
+
+        if (!parsed) {
+            co_return; 
+        }
+
+        // Authenticate against database.
     }
 
     enum class state {
diff --git a/tests/msgpack/BUILD b/tests/msgpack/BUILD
index 713872b..aa295cd 100644
--- a/tests/msgpack/BUILD
+++ b/tests/msgpack/BUILD
@@ -3,7 +3,7 @@ cc_library(
     name = "test_deps",
     srcs = [
         "test_main.cpp",
-        "rng.h"
+        "rng.h",
     ],
     deps = [
         "//include/parselink:msgpack",
@@ -47,6 +47,14 @@ cc_test(
     deps = ["test_deps"],
 )
 
+cc_test(
+    name = "token_views",
+    srcs = [
+        "test_token_views.cpp",
+    ],
+    deps = ["test_deps"],
+)
+
 cc_binary(
     name = "speed",
     srcs = [
diff --git a/tests/msgpack/test_token_views.cpp b/tests/msgpack/test_token_views.cpp
new file mode 100644
index 0000000..48daff8
--- /dev/null
+++ b/tests/msgpack/test_token_views.cpp
@@ -0,0 +1,219 @@
+#include <msgpack/token.h>
+
+#include <boost/ut.hpp>
+#include <fmt/format.h>
+#include <fmt/ranges.h>
+#include <magic_enum.hpp>
+
+using namespace boost::ut;
+namespace {
+template <typename T>
+constexpr bool operator==(std::span<T const> a, std::span<T const> b) noexcept {
+    return std::equal(a.begin(), a.end(), b.begin(), b.end());
+}
+
+template <typename T>
+constexpr std::array<std::byte, sizeof(T)> as_bytes(T&& t) {
+    return std::bit_cast<std::array<std::byte, sizeof(T)>>(std::forward<T>(t));
+}
+
+template <typename... Bytes>
+constexpr std::array<std::byte, sizeof...(Bytes)> make_bytes(Bytes &&...bytes) {
+    return {std::byte(std::forward<Bytes>(bytes))...};
+}
+
+template <typename T, std::size_t C = 1024 * 1024> struct oversized_array {
+    std::array<T, C> data;
+    std::size_t size;
+};
+
+
+constexpr auto to_bytes_array_oversized(auto const &container) {
+    using value_type = std::decay_t<decltype(container[0])>;
+    oversized_array<value_type> arr;
+    std::copy(std::begin(container), std::end(container), std::begin(arr.data));
+    arr.size = std::distance(std::begin(container), std::end(container));
+    return arr;
+}
+
+consteval auto generate_bytes(auto callable) {
+    constexpr auto oversized = to_bytes_array_oversized(callable());
+    using value_type = std::decay_t<decltype(oversized.data[0])>;
+    std::array<value_type, oversized.size> out;
+    std::copy(std::begin(oversized.data),
+            std::next(std::begin(oversized.data), oversized.size),
+            std::begin(out));
+    return out;
+}
+
+consteval auto build_string(auto callable) {
+    constexpr auto string_array = generate_bytes(callable);
+    return string_array;
+}
+
+template <std::size_t ... Sizes>
+constexpr auto cat(std::array<std::byte, Sizes>const&... a) noexcept {
+    std::array<std::byte, (Sizes + ...)> out;
+    std::size_t index{};
+    ((std::copy_n(a.begin(), Sizes, out.begin() + index), index += Sizes), ...);
+    return out;
+}
+
+constexpr auto repeat(std::span<std::byte const> sv, std::size_t count) {
+    std::vector<std::byte> range;
+    range.reserve(sv.size() * count);
+    for (decltype(count) i = 0; i < count; ++i) {
+        std::copy_n(sv.begin(), sv.size(), std::back_inserter(range));
+    }
+    return range;
+}
+
+constexpr auto repeat(std::string_view sv, std::size_t count) {
+    std::vector<char> range;
+    range.reserve(sv.size() * count);
+    for (decltype(count) i = 0; i < count; ++i) {
+        std::copy_n(sv.begin(), sv.size(), std::back_inserter(range));
+    }
+    return range;
+}
+
+constexpr auto from_string_view(std::string_view sv) {
+    std::vector<std::byte> range;
+    range.resize(sv.size());
+    auto itr = range.begin();
+    for (auto c : sv) {
+        *itr = std::byte(c);
+        ++itr;
+    }
+    return range;
+}
+
+template <typename T, typename E>
+    std::ostream &operator<<(std::ostream &os, tl::expected<T, E> const &exp) {
+        if (exp.has_value()) {
+            os << "Value: '" << *exp << "'";
+        } else {
+            os << "Error";
+        }
+        return os;
+    }
+
+bool test_incomplete_message(auto const& payload) {
+    // Test incomplete message.
+    for (decltype(payload.size()) i = 1; i < payload.size() - 1; ++i) {
+        // Test incomplete message.
+        msgpack::token_reader reader(std::span(payload.data(), i));
+        auto token = reader.read_one();
+        if (token != tl::make_unexpected(msgpack::error::incomplete_message)) {
+            fmt::print("Got the wrong response reading subview[0,{}] of payload: {}\n",
+                    i,
+                    token->get<std::string_view>().value());
+            return false;
+        }
+    }
+    return true;
+}
+
+bool test_end_of_message(auto& reader) {
+    return reader.read_one() ==
+        tl::make_unexpected(msgpack::error::end_of_message);
+}
+}
+
+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 {
+        auto out = fmt::format_to(ctx.out(), "<msgpack {} = ", magic_enum::enum_name(v.type()));
+        switch (v.type()) {
+            case msgpack::format::type::unsigned_int:
+                fmt::format_to(out, "{}", (*(v.get<std::uint64_t>())));
+                break;
+            case msgpack::format::type::signed_int:
+                out = fmt::format_to(out, "{}", (*(v.get<std::uint64_t>())));
+                break;
+            case msgpack::format::type::boolean:
+                out = fmt::format_to(out, "{}", (*(v.get<bool>())));
+                break;
+            case msgpack::format::type::string:
+                out = fmt::format_to(out, "{}", (*(v.get<std::string_view>())));
+                break;
+            case msgpack::format::type::binary:
+                out = fmt::format_to(out, "{}",
+                        (*(v.get<std::span<std::byte const>>())));
+                break;
+            case msgpack::format::type::map:
+                out = fmt::format_to(out, "(arity: {})",
+                        (v.get<msgpack::map_desc>()->count));
+                break;
+            case msgpack::format::type::array:
+                out = fmt::format_to(out, "(arity: {})",
+                        (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, ">");
+    }
+};
+
+suite views_tests = [] {
+    "read format::fixmap"_test = [] {
+        // A MessagePack map of 3 strings to 8-bit unsigned integers.
+        static constexpr auto strings = std::to_array<std::string_view>({
+            "one", "two", "three", "array", "four", "map", "five",
+        });
+
+        constexpr auto payload = cat(
+                make_bytes(0x87, 0xa3),
+                generate_bytes([] { return from_string_view(strings[0]); }),
+
+                make_bytes(0x01, 0xa3),
+                generate_bytes([] { return from_string_view(strings[1]); }),
+
+                make_bytes(0x02, 0xa5),
+                generate_bytes([] { return from_string_view(strings[2]); }),
+
+                make_bytes(0x03, 0xa5),
+                generate_bytes([] { return from_string_view(strings[3]); }),
+
+                // Array of size 2, two fixints:
+                make_bytes(0x92, 0x32, 0x33),
+
+                make_bytes(0xa4),
+                generate_bytes([] { return from_string_view(strings[4]); }),
+
+                make_bytes(0x04, 0xa3),
+                generate_bytes([] { return from_string_view(strings[5]); }),
+
+                // Map of size 3, 6 total fixints.
+                make_bytes(0x83, 0x01, 0x02, 0x03, 0x04, 0x33, 0x11),
+
+                make_bytes(0xa4),
+                generate_bytes([] { return from_string_view(strings[6]); })
+                //make_bytes(0x05)
+        );
+
+        std::array<msgpack::token, 32> tokens;
+
+        msgpack::token_reader reader(payload);
+
+        auto result = reader.read_some(tokens).map([](auto read_tokens) {
+            for (auto const& [k, v] : msgpack::map_view(read_tokens)) {
+                fmt::print("map[{}] = {}\n", k, v);
+            }
+        });
+
+        expect(result.has_value());
+    };
+};
diff --git a/tests/msgpack/test_utils.h b/tests/msgpack/test_utils.h
new file mode 100644
index 0000000..e05afe7
--- /dev/null
+++ b/tests/msgpack/test_utils.h
@@ -0,0 +1,98 @@
+#ifndef msgpack_test_utils_4573e6627d8efe78
+#define msgpack_test_utils_4573e6627d8efe78
+
+#include <boost/ut.hpp>
+#include <fmt/format.h>
+#include <magic_enum.hpp>
+
+template <typename T>
+constexpr bool operator==(std::span<T const> a, std::span<T const> b) noexcept {
+    return std::equal(a.begin(), a.end(), b.begin(), b.end());
+}
+
+template <typename T>
+constexpr std::array<std::byte, sizeof(T)> as_bytes(T&& t) {
+    return std::bit_cast<std::array<std::byte, sizeof(T)>>(std::forward<T>(t));
+}
+
+template <typename... Bytes>
+constexpr std::array<std::byte, sizeof...(Bytes)> make_bytes(Bytes &&...bytes) {
+    return {std::byte(std::forward<Bytes>(bytes))...};
+}
+
+template <typename T, std::size_t C = 1024 * 1024> struct oversized_array {
+    std::array<T, C> data;
+    std::size_t size;
+};
+
+constexpr auto to_bytes_array_oversized(auto const &container) {
+    using value_type = std::decay_t<decltype(container[0])>;
+    oversized_array<value_type> arr;
+    std::copy(std::begin(container), std::end(container), std::begin(arr.data));
+    arr.size = std::distance(std::begin(container), std::end(container));
+    return arr;
+}
+
+consteval auto generate_bytes(auto callable) {
+    constexpr auto oversized = to_bytes_array_oversized(callable());
+    using value_type = std::decay_t<decltype(oversized.data[0])>;
+    std::array<value_type, oversized.size> out;
+    std::copy(std::begin(oversized.data),
+            std::next(std::begin(oversized.data), oversized.size),
+            std::begin(out));
+    return out;
+}
+
+consteval auto build_string(auto callable) {
+    constexpr auto string_array = generate_bytes(callable);
+    return string_array;
+}
+
+template <std::size_t ... Sizes>
+constexpr auto cat(std::array<std::byte, Sizes>const&... a) noexcept {
+    std::array<std::byte, (Sizes + ...)> out;
+    std::size_t index{};
+    ((std::copy_n(a.begin(), Sizes, out.begin() + index), index += Sizes), ...);
+    return out;
+}
+
+constexpr auto repeat(std::span<std::byte const> sv, std::size_t count) {
+    std::vector<std::byte> range;
+    range.reserve(sv.size() * count);
+    for (decltype(count) i = 0; i < count; ++i) {
+        std::copy_n(sv.begin(), sv.size(), std::back_inserter(range));
+    }
+    return range;
+}
+
+constexpr auto repeat(std::string_view sv, std::size_t count) {
+    std::vector<char> range;
+    range.reserve(sv.size() * count);
+    for (decltype(count) i = 0; i < count; ++i) {
+        std::copy_n(sv.begin(), sv.size(), std::back_inserter(range));
+    }
+    return range;
+}
+
+constexpr auto from_string_view(std::string_view sv) {
+    std::vector<std::byte> range;
+    range.resize(sv.size());
+    auto itr = range.begin();
+    for (auto c : sv) {
+        *itr = std::byte(c);
+        ++itr;
+    }
+    return range;
+}
+
+template <typename T, typename E>
+std::ostream &operator<<(std::ostream &os, tl::expected<T, E> const &exp) {
+    if (exp.has_value()) {
+        os << "Value: '" << *exp << "'";
+    } else {
+        os << "Error";
+    }
+    return os;
+}
+
+#endif // msgpack_test_utils_4573e6627d8efe78