VWeb/Source/Router.cpp

#include "Includes/VWeb.h"
#include "StringUtils.h"

#include <iostream>
#include <type_traits>
#include <utility>

namespace VWeb {

#define stringify(name)                                                        \
  { name, std::string(#name).replace(0, 12, "") }
static std::unordered_map<HttpMethod, std::string> s_HttpMethodToString = {
    stringify(HttpMethod::HEAD),    stringify(HttpMethod::GET),
    stringify(HttpMethod::OPTIONS), stringify(HttpMethod::POST),
    stringify(HttpMethod::PUT),     stringify(HttpMethod::PATCH),
    stringify(HttpMethod::DELETE),  stringify(HttpMethod::FALLBACK)};
#undef stringify

template <typename E> constexpr auto to_underlying(E e) noexcept {
  return static_cast<std::underlying_type_t<E>>(e);
}

class ErrorRoute : public Route {
public:
  bool Execute(Request &request, Response &response) override {
    response.Reset();
    response << "Unhandled Error: Status "
             << std::to_string(to_underlying(response.Status));
    response.SetType("text/plain");
    return true;
  }
};

void RouteTree::Add(const std::string &path, uint32_t allowedMethods,
                    RouteInstaniateFunction instaniate) {
  auto segments = String::Split(path, "/");
  auto node = &Root;
  for (const auto &segment : segments) {
    if (segment.empty())
      continue;
    if (!node->Children.contains(segment)) {
      node->Children[segment] = std::make_unique<Node>(m_NodeID++);
    }
    node = node->Children.at(segment).get();
  }
  m_Routes[node->ID] = {.AllowedMethods = allowedMethods,
                        .Instaniate = std::move(instaniate)};
}

Ref<Route> RouteTree::Find(const std::string &path, Request &request) {
  auto segments = String::Split(path, "/");
  auto node = &Root;
  for (const auto &segment : segments) {
    if (segment.empty())
      continue;
    if (auto it = node->Children.find(segment); it != node->Children.end()) {
      node = it->second.get();
    } else {
      // Arguments...
      bool foundParameter = false;
      for (auto &[key, child] : node->Children) {
        if (key[0] == ':') {
          node = child.get();
          foundParameter = true;
          request.URLParameters[key.substr(1)] = segment;
          break;
        }
      }
      if (!foundParameter) {
        request.URLParameters = {};
        return nullptr;
      }
    }
  }
  if (m_Routes.contains(node->ID)) {
    const auto &instance = m_Routes[node->ID];
    auto ref = instance.Instaniate();
    ref->SetAllowedMethods(instance.AllowedMethods);
    return ref;
  }
  request.URLParameters = {};
  return nullptr;
}

Router::Router() { Register<ErrorRoute>("@"); }

static void HandleOptions(Ref<Response> &response, uint32_t allowedMethods) {
  std::stringstream str{};
  bool isFirst = true;
  for (auto &[key, value] : s_HttpMethodToString) {
    if (allowedMethods & static_cast<uint32_t>(key)) {
      if (!isFirst)
        str << ", ";
      str << value;
      isFirst = false;
    }
  }
  response->SetHeader("Allow", str.str());
}

Ref<Response> Router::HandleRoute(Ref<Request> &request) {
  auto response = CreateRef<Response>();
  auto route = FindRoute(request);
  response->CookieData = request->CookieData;
  response->SessionData = request->SessionData;
  response->Method = request->Method;

  if (!route) {
    route = m_Tree.Find(s_HttpMethodToString[request->Method] + request->URI,
                        *request);
    if (!route) {
      response->SetStatus(HttpStatusCode::NotFound);
      m_Tree.Find("@", *request)->Execute(*request, *response);
      return response;
    }
  }

  if (!route->IsAllowed(*request)) {
    response->SetStatus(HttpStatusCode::Forbidden);
    m_Tree.Find("@", *request)->Execute(*request, *response);
    return response;
  }

  if (request->Method == HttpMethod::OPTIONS) {
    HandleOptions(response, route->GetAllowedMethods());
    return response;
  }

  if (!route->Execute(*request, *response)) {
    std::string rKey = "@" + std::to_string(to_underlying(response->Status));
    auto r = m_Tree.Find(rKey, *request);
    if (r) {
      r->Execute(*request, *response);
    } else {
      m_Tree.Find("@", *request)->Execute(*request, *response);
    }
  }
  return response;
}

Ref<Route> Router::FindRoute(Ref<Request> &request) {
  const auto &url = request->URI;
  if (url.starts_with("@"))
    return nullptr;
  return m_Tree.Find(url, *request);
}

struct InlineRoute : Route {
  explicit InlineRoute(RouteFunction function) : Func(std::move(function)) {}
  RouteFunction Func;
  bool Execute(Request &request, Response &response) override {
    Func(request, response);
    return true;
  }
  bool IsAllowed(Request &request) override { return true; }
};

void Router::Get(const std::string &path, const RouteFunction &func) {
  m_Tree.Add(path, static_cast<uint32_t>(HttpMethod::GET),
             [func] { return std::make_shared<InlineRoute>(func); });
}
void Router::Post(const std::string &path, const RouteFunction &func) {
  m_Tree.Add(path, static_cast<uint32_t>(HttpMethod::POST),
             [func] { return std::make_shared<InlineRoute>(func); });
}
void Router::Put(const std::string &path, const RouteFunction &func) {
  m_Tree.Add(path, static_cast<uint32_t>(HttpMethod::PUT),
             [func] { return std::make_shared<InlineRoute>(func); });
}
void Router::Patch(const std::string &path, const RouteFunction &func) {
  m_Tree.Add(path, static_cast<uint32_t>(HttpMethod::PATCH),
             [func] { return std::make_shared<InlineRoute>(func); });
}
void Router::Delete(const std::string &path, const RouteFunction &func) {
  m_Tree.Add(path, static_cast<uint32_t>(HttpMethod::DELETE),
             [func] { return std::make_shared<InlineRoute>(func); });
}
} // namespace VWeb