/*

 * SPDX-FileCopyrightText: 2016 Mathieu Stefani

 *

 * SPDX-License-Identifier: Apache-2.0

 */

/* router.cc

   Mathieu Stefani, 05 janvier 2016

   Rest routing implementation

*/

#include <algorithm>

#include <pistache/description.h>

#include <pistache/router.h>

namespace Pistache::Rest

{

    Request::Request(Http::Request request, std::vector<TypedParam>&& params,

                     std::vector<TypedParam>&& splats)

        : Http::Request(std::move(request))

        , params_(std::move(params))

        , splats_(std::move(splats))

    { }

    bool Request::hasParam(const std::string& name) const

    {

        auto it = std::find_if(

            params_.begin(), params_.end(),

            [&](const TypedParam& param) { return param.name() == name; });

        return it != std::end(params_);

    }

    TypedParam Request::param(const std::string& name) const

    {

        auto it = std::find_if(

            params_.begin(), params_.end(),

            [&](const TypedParam& param) { return param.name() == name; });

        if (it == std::end(params_))

        {

            throw std::runtime_error("Unknown parameter");

        }

        return *it;

    }

    TypedParam Request::splatAt(size_t index) const

    {

        if (index >= splats_.size())

        {

            throw std::out_of_range("Request splat index out of range");

        }

        return splats_[index];

    }

    std::vector<TypedParam> Request::splat() const { return splats_; }

    SegmentTreeNode::SegmentTreeNode()

        : resource_ref_()

        , fixed_()

        , param_()

        , optional_()

        , splat_(nullptr)

        , route_(nullptr)

    {

        std::shared_ptr<char> ptr(new char[1], std::default_delete<char[]>());

        resource_ref_.swap(ptr);

    }

    SegmentTreeNode::SegmentTreeNode(const std::shared_ptr<char>& resourceReference)

        : resource_ref_(resourceReference)

        , fixed_()

        , param_()

        , optional_()

        , splat_(nullptr)

        , route_(nullptr)

    { }

    SegmentTreeNode::SegmentType

    SegmentTreeNode::getSegmentType(const std::string_view& fragment)

    {

        if (fragment.empty())

            return SegmentType::Fixed;

        auto optpos = fragment.find('?');

        if (fragment[0] == ':')

        {

            if (optpos != std::string_view::npos)

            {

                if (optpos != fragment.length() - 1)

                {

                    throw std::runtime_error("? should be at the end of the string");

                }

                return SegmentType::Optional;

            }

            return SegmentType::Param;

        }

        else if (fragment[0] == '*')

        {

            if (fragment.length() > 1)

            {

                throw std::runtime_error("Invalid splat parameter");

            }

            return SegmentType::Splat;

        }

        if (optpos != std::string_view::npos)

        {

            throw std::runtime_error(

                "Only optional parameters are currently supported");

        }

        return SegmentType::Fixed;

    }

    std::string SegmentTreeNode::sanitizeResource(const std::string& path)

    {

        std::string dup;

        dup.reserve(path.size());

        for (const char c : path)

        {

            if (c != '/' || dup.empty() || dup.back() != '/')

                dup.push_back(c);

        }

        if (dup[dup.length() - 1] == '/')

        {

            return dup.substr(1, dup.length() - 2);

        }

        return dup.substr(1);

    }

    void SegmentTreeNode::addRoute(

        const std::string_view& path, const Route::Handler& handler,

        const std::shared_ptr<char>& resource_reference)

    {

        // recursion to correct path segment

        if (!path.empty())

        {

            const auto segment_delimiter = path.find('/');

            // current segment value

            auto current_segment = path.substr(0, segment_delimiter);

            // complete child path (path without this segment)

            // if no '/' was found, it means that it is a leaf resource

            const auto lower_path = (segment_delimiter == std::string_view::npos)

                ? std::string_view { nullptr, 0 }

                : path.substr(segment_delimiter + 1);

            std::unordered_map<std::string_view, std::shared_ptr<SegmentTreeNode>>* collection = nullptr;

            const auto fragmentType                                                            = getSegmentType(current_segment);

            switch (fragmentType)

            {

            case SegmentType::Fixed:

                collection = &fixed_;

                break;

            case SegmentType::Param:

                collection = &param_;

                break;

            case SegmentType::Optional:

                // remove the trailing question mark

                current_segment = current_segment.substr(0, current_segment.length() - 1);

                collection      = &optional_;

                break;

            case SegmentType::Splat:

                if (splat_ == nullptr)

                {

                    splat_ = std::make_shared<SegmentTreeNode>(resource_reference);

                }

                splat_->addRoute(lower_path, handler, resource_reference);

                return;

            }

            // if the segment tree nodes for the lower path does not exist

            if (collection->count(current_segment) == 0)

            {

                // first create it

                collection->insert(std::make_pair(

                    current_segment,

                    std::make_shared<SegmentTreeNode>(resource_reference)));

            }

            collection->at(current_segment)

                ->addRoute(lower_path, handler, resource_reference);

        }

        else

        { // current path segment requested

            if (route_ != nullptr)

                throw std::runtime_error("Requested route already exist.");

            route_ = std::make_shared<Route>(handler);

        }

    }

    bool Pistache::Rest::SegmentTreeNode::removeRoute(

        const std::string_view& path)

    {

        // recursion to correct path segment

        if (!path.empty())

        {

            const auto segment_delimiter = path.find('/');

            // current segment value

            auto current_segment = path.substr(0, segment_delimiter);

            // complete child path (path without this segment)

            // if no '/' was found, it means that it is a leaf resource

            const auto lower_path = (segment_delimiter == std::string_view::npos)

                ? std::string_view { nullptr, 0 }

                : path.substr(segment_delimiter + 1);

            std::unordered_map<std::string_view, std::shared_ptr<SegmentTreeNode>>* collection = nullptr;

            auto fragmentType                                                                  = getSegmentType(current_segment);

            switch (fragmentType)

            {

            case SegmentType::Fixed:

                collection = &fixed_;

                break;

            case SegmentType::Param:

                collection = &param_;

                break;

            case SegmentType::Optional:

                // remove the trailing question mark

                current_segment = current_segment.substr(0, current_segment.length() - 1);

                collection      = &optional_;

                break;

            case SegmentType::Splat:

                if (!splat_)

                    throw std::runtime_error("Requested route does not exist.");

                return splat_->removeRoute(lower_path);

            }

            try

            {

                const bool removable = collection->at(current_segment)->removeRoute(lower_path);

                if (removable)

                {

                    collection->erase(current_segment);

                }

            }

            catch (const std::out_of_range&)

            {

                throw std::runtime_error("Requested route does not exist.");

            }

        }

        else

        { // current leaf requested

            route_.reset();

        }

        return fixed_.empty() && param_.empty() && optional_.empty() && splat_ == nullptr && route_ == nullptr;

    }

    std::tuple<std::shared_ptr<Route>, std::vector<TypedParam>,

               std::vector<TypedParam>>

    Pistache::Rest::SegmentTreeNode::findRoute(

        const std::string_view& path, std::vector<TypedParam>& params,

        std::vector<TypedParam>& splats) const

    {

        // recursion to correct path segment

        if (!path.empty())

        {

            const auto segment_delimiter = path.find('/');

            // current segment value

            auto current_segment = path.substr(0, segment_delimiter);

            // complete child path (path without this segment)

            // if no '/' was found, it means that it is a leaf resource

            const auto lower_path = (segment_delimiter == std::string_view::npos)

                ? std::string_view { nullptr, 0 }

                : path.substr(segment_delimiter + 1);

            // Check if it is a fixed route

            if (fixed_.count(current_segment) != 0)

            {

                auto result = fixed_.at(current_segment)->findRoute(lower_path, params, splats);

                auto route  = std::get<0>(result);

                if (route != nullptr)

                    return result;

            }

            // Check if it is a path param

            for (const auto& param : param_)

            {

                std::string para_name { param.first.data(), param.first.length() };

                std::string para_val { current_segment.data(), current_segment.length() };

                params.emplace_back(para_name, para_val);

                auto result = param.second->findRoute(lower_path, params, splats);

                auto route  = std::get<0>(result);

                if (route != nullptr)

                    return result;

                params.pop_back();

            }

            // Check if it is an optional path param

            for (const auto& optional : optional_)

            {

                std::string opt_name { optional.first.data(), optional.first.length() };

                std::string opt_val { current_segment.data(), current_segment.length() };

                params.emplace_back(opt_name, opt_val);

                auto result = optional.second->findRoute(lower_path, params, splats);

                auto route = std::get<0>(result);

                if (route != nullptr)

                    return result;

                params.pop_back();

                // try to find a route for lower path assuming that

                // this optional path param is not present

                result = optional.second->findRoute(lower_path, params, splats);

                route = std::get<0>(result);

                if (route != nullptr)

                    return result;

            }

            // Check if it is a splat

            if (splat_ != nullptr)

            {

                std::string splat { current_segment.data(), current_segment.length() };

                splats.emplace_back(splat, splat);

                auto result = splat_->findRoute(lower_path, params, splats);

                auto route = std::get<0>(result);

                if (route != nullptr)

                    return result;

                splats.pop_back();

            }

            // Requested route does not exists

            return std::make_tuple(nullptr, std::vector<TypedParam>(),

                                   std::vector<TypedParam>());

        }

        else

        { // current leaf requested, or empty final optional

            if (!optional_.empty())

            {

                // in case of more than one optional at this point, as it is an

                // ambiguity, it is resolved by using the first optional

                auto optional = optional_.begin();

                // std::string opt {optional->first.data(), optional->first.length()};

                return optional->second->findRoute(path, params, splats);

            }

            else if (route_ == nullptr)

            {

                // if we are here but route is null, we reached this point

                // trying to parse an optional, that was missing

                return std::make_tuple(nullptr, std::vector<TypedParam>(),

                                       std::vector<TypedParam>());

            }

            else

            {

                return std::make_tuple(route_, std::move(params), std::move(splats));

            }

        }

    }

    std::tuple<std::shared_ptr<Route>, std::vector<TypedParam>,

               std::vector<TypedParam>>

    Pistache::Rest::SegmentTreeNode::findRoute(const std::string_view& path) const

    {

        std::vector<TypedParam> params;

        std::vector<TypedParam> splats;

        return findRoute(path, params, splats);

    }

    namespace Private

    {

        RouterHandler::RouterHandler(const Rest::Router& router)

            : router(std::make_shared<Rest::Router>(router))

        { }

        RouterHandler::RouterHandler(std::shared_ptr<Rest::Router> router)

            : router(std::move(router))

        { }

        void RouterHandler::onRequest(const Http::Request& req,

                                      Http::ResponseWriter response)

        {

            PS_TIMEDBG_START_THIS;

            router->route(req, std::move(response));

        }

        void RouterHandler::onDisconnection(const std::shared_ptr<Tcp::Peer>& peer)

        {

            PS_TIMEDBG_START_THIS;

            router->disconnectPeer(peer);

        }

    } // namespace Private

    Router Router::fromDescription(const Rest::Description& desc)

    {

        Router router;

        router.initFromDescription(desc);

        return router;

    }

    std::shared_ptr<Private::RouterHandler> Router::handler() const

    {

        return std::make_shared<Private::RouterHandler>(*this);

    }

    std::shared_ptr<Private::RouterHandler>

    Router::handler(std::shared_ptr<Rest::Router> router)

    {

        return std::make_shared<Private::RouterHandler>(router);

    }

    void Router::initFromDescription(const Rest::Description& desc)

    {

        const auto& paths = desc.rawPaths();

        for (auto it = paths.flatBegin(), end = paths.flatEnd(); it != end; ++it)

        {

            const auto& paths_ = *it;

            for (const auto& path : paths_)

            {

                if (!path.isBound())

                {

                    std::ostringstream oss;

                    oss << "Path '" << path.value << "' is not bound";

                    throw std::runtime_error(oss.str());

                }

                addRoute(path.method, path.value, path.handler);

            }

        }

    }

    void Router::get(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Get, resource, std::move(handler));

    }

    void Router::post(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Post, resource, std::move(handler));

    }

    void Router::put(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Put, resource, std::move(handler));

    }

    void Router::patch(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Patch, resource, std::move(handler));

    }

    void Router::del(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Delete, resource, std::move(handler));

    }

    void Router::options(const std::string& resource, Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        addRoute(Http::Method::Options, resource, std::move(handler));

    }

    void Router::removeRoute(Http::Method method, const std::string& resource)

    {

        if (resource.empty())

            throw std::runtime_error("Invalid zero-length URL.");

        auto& r              = routes[method];

        const auto sanitized = SegmentTreeNode::sanitizeResource(resource);

        const std::string_view path { sanitized.data(), sanitized.size() };

        r.removeRoute(path);

    }

    void Router::head(const std::string& resource, Route::Handler handler)

    {

        addRoute(Http::Method::Head, resource, std::move(handler));

    }

    void Router::addCustomHandler(Route::Handler handler)

    {

        customHandlers.push_back(std::move(handler));

    }

    void Router::addMiddleware(Route::Middleware middleware)

    {

        middlewares.push_back(std::move(middleware));

    }

    void Router::addDisconnectHandler(Route::DisconnectHandler handler)

    {

        disconnectHandlers.push_back(std::move(handler));

    }

    void Router::addNotFoundHandler(Route::Handler handler)

    {

        notFoundHandler = std::move(handler);

    }

    void Router::invokeNotFoundHandler(const Http::Request& req,

                                       Http::ResponseWriter resp) const

    {

        notFoundHandler(Rest::Request(req, std::vector<TypedParam>(),

                                      std::vector<TypedParam>()),

                        std::move(resp));

    }

    Route::Status Router::route(const Http::Request& request,

                                Http::ResponseWriter response) const

    {

        PS_TIMEDBG_START_THIS;

        const auto& resource = request.resource();

        if (resource.empty())

            throw std::runtime_error("Invalid zero-length URL.");

        auto req  = request;

        auto resp = response.clone();

        for (const auto& middleware : middlewares)

        {

            auto result = middleware(req, resp);

            // Handler returns true, go to the next piped handler, otherwise break and return

            if (!result)

                return Route::Status::Match;

        }

        std::tuple<std::shared_ptr<Route>, std::vector<TypedParam>,

                   std::vector<TypedParam>>

            result;

        const auto sanitized = SegmentTreeNode::sanitizeResource(resource);

        const std::string_view path { sanitized.data(), sanitized.size() };

        const auto routesIt = routes.find(req.method());

        if (routesIt != routes.end())

            result = routesIt->second.findRoute(path);

        auto route = std::get<0>(result);

        if (route != nullptr)

        {

            auto params = std::get<1>(result);

            auto splats = std::get<2>(result);

            route->invokeHandler(Request(std::move(req), std::move(params), std::move(splats)),

                                 std::move(resp));

            return Route::Status::Match;

        }

        for (const auto& handler : customHandlers)

        {

            auto cloned_resp     = response.clone();

            auto handler1 = handler(

                Request(req, std::vector<TypedParam>(), std::vector<TypedParam>()),

                std::move(cloned_resp));

            if (handler1 == Route::Result::Ok)

                return Route::Status::Match;

        }

        // No route or custom handler found. Let's walk through the

        // list of other methods and see if any of them support

        // this resource.

        // This will allow server to send a

        // HTTP 405 (method not allowed) response.

        // RFC 7231 requires HTTP 405 responses to include a list of

        // supported methods for the requested resource.

        std::vector<Http::Method> supportedMethods;

        for (auto& methods : routes)

        {

            if (methods.first == req.method())

                continue;

            auto res = methods.second.findRoute(path);

            auto rte = std::get<0>(res);

            if (rte != nullptr)

            {

                supportedMethods.push_back(methods.first);

            }

        }

        if (!supportedMethods.empty())

        {

            response.sendMethodNotAllowed(supportedMethods);

            return Route::Status::NotAllowed;

        }

        if (hasNotFoundHandler())

        {

            invokeNotFoundHandler(req, std::move(response));

        }

        else

        {

            response.send(Http::Code::Not_Found, "Could not find a matching route");

        }

        return Route::Status::NotFound;

    }

    void Router::addRoute(Http::Method method, const std::string& resource,

                          Route::Handler handler)

    {

        PS_TIMEDBG_START_THIS;

        if (resource.empty())

            throw std::runtime_error("Invalid zero-length URL.");

        auto& r              = routes[method];

        const auto sanitized = SegmentTreeNode::sanitizeResource(resource);

        std::shared_ptr<char> ptr(new char[sanitized.length()],

                                  std::default_delete<char[]>());

        std::memcpy(ptr.get(), sanitized.data(), sanitized.length());

        const std::string_view path { ptr.get(), sanitized.length() };

        r.addRoute(path, handler, ptr);

    }

    void Router::disconnectPeer(const std::shared_ptr<Tcp::Peer>& peer)

    {

        PS_TIMEDBG_START_THIS;

        for (const auto& handler : disconnectHandlers)

        {

            handler(peer);

        }

    }

    namespace Routes

    {

        void Get(Router& router, const std::string& resource, Route::Handler handler)

        {

            router.get(resource, std::move(handler));

        }

        void Post(Router& router, const std::string& resource, Route::Handler handler)

        {

            router.post(resource, std::move(handler));

        }

        void Put(Router& router, const std::string& resource, Route::Handler handler)

        {

            router.put(resource, std::move(handler));

        }

        void Patch(Router& router, const std::string& resource,

                   Route::Handler handler)

        {

            router.patch(resource, std::move(handler));

        }

        void Delete(Router& router, const std::string& resource,

                    Route::Handler handler)

        {

            router.del(resource, std::move(handler));

        }

        void Options(Router& router, const std::string& resource,

                     Route::Handler handler)

        {

            router.options(resource, std::move(handler));

        }

        void Remove(Router& router, Http::Method method, const std::string& resource)

        {

            router.removeRoute(method, resource);

        }

        void NotFound(Router& router, Route::Handler handler)

        {

            router.addNotFoundHandler(std::move(handler));

        }

        void Head(Router& router, const std::string& resource, Route::Handler handler)

        {

            router.head(resource, std::move(handler));

        }

    } // namespace Routes

} // namespace Pistache::Rest