#pragma once
#include <charconv>
#include <cstdint>
#include <functional>
#include <map>
#include <memory>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
#include <vector>
namespace drogon {
enum HttpStatusCode {
    k200OK = 200,
    k400BadRequest = 400,
    k404NotFound = 404,
    k422UnprocessableEntity = 422,
    k500InternalServerError = 500
};
enum ContentType {
    CT_APPLICATION_JSON
};
enum HttpMethod {
    Get,
    Post,
    Put,
    Patch,
    Delete
};
namespace internal {
class HttpConstraint {
public:
    HttpConstraint(HttpMethod method) : method_(method), is_method_(true) {}
    HttpConstraint(std::string filter) : filter_(std::move(filter)) {}
    bool is_method() const noexcept {
        return is_method_;
    }
    HttpMethod method() const noexcept {
        return method_;
    }
    const std::string& filter() const noexcept {
        return filter_;
    }
private:
    HttpMethod method_{Get};
    bool is_method_{};
    std::string filter_;
};
}
class HttpResponse {
public:
    static std::shared_ptr<HttpResponse> newHttpResponse() {
        return std::make_shared<HttpResponse>();
    }
    void setStatusCode(HttpStatusCode value) {
        status = value;
    }
    void setContentTypeCode(ContentType value) {
        content_type = value;
    }
    void setBody(std::string value) {
        body = std::move(value);
    }
    HttpStatusCode status{k200OK};
    ContentType content_type{CT_APPLICATION_JSON};
    std::string body;
};
using HttpResponsePtr = std::shared_ptr<HttpResponse>;
class HttpRequest {
public:
    std::string_view getBody() const noexcept {
        return body;
    }
    const std::string& getParameter(const std::string& name) const {
        const auto iterator = parameters.find(name);
        return iterator == parameters.end() ? empty_parameter_ : iterator->second;
    }
    std::string body;
    std::string user;
    std::map<std::string, std::string> parameters;
private:
    inline static const std::string empty_parameter_;
};
using HttpRequestPtr = std::shared_ptr<HttpRequest>;
class HttpAppFramework {
public:
    using Callback = std::function<void(const HttpResponsePtr&)>;
    using Handler = std::function<void(const HttpRequestPtr&, Callback&&)>;
    using Parameter_Handler = std::function<void(const HttpRequestPtr&, Callback&&, std::uint64_t)>;
    template <class Function>
    void registerHandler(const std::string& path, Function&& function, const std::vector<internal::HttpConstraint>& constraints) {
        HttpMethod method = Get;
        std::vector<std::string> filters;
        for(const auto& constraint : constraints) {
            if(constraint.is_method()) {
                method = constraint.method();
            } else {
                filters.push_back(constraint.filter());
            }
        }
        Route route;
        route.path = path;
        route.method = method;
        route.filters = std::move(filters);
        if constexpr(std::is_invocable_v<Function, const HttpRequestPtr&, Callback&&, std::uint64_t>) {
            route.parameter_handler = Parameter_Handler(std::forward<Function>(function));
        } else {
            route.handler = Handler(std::forward<Function>(function));
        }
        routes_.push_back(std::move(route));
    }
    void handle(const std::string& path, HttpMethod method, const HttpRequestPtr& request, Callback callback) {
        for(auto& route : routes_) {
            if(route.method != method) {
                continue;
            }
            if(route.handler && route.path == path) {
                route.handler(request, std::move(callback));
                return;
            }
            std::uint64_t parameter{};
            if(route.parameter_handler && match_parameter_route(route.path, path, parameter)) {
                route.parameter_handler(request, std::move(callback), parameter);
                return;
            }
        }
        throw std::runtime_error("route is not registered");
    }
    const std::vector<std::string>& filters(const std::string& path, HttpMethod method) const {
        for(const auto& route : routes_) {
            if(route.path == path && route.method == method) {
                return route.filters;
            }
        }
        throw std::runtime_error("route is not registered");
    }
private:
    struct Route {
        std::string path;
        HttpMethod method{Get};
        Handler handler;
        Parameter_Handler parameter_handler;
        std::vector<std::string> filters;
    };
    static bool match_parameter_route(const std::string& pattern, const std::string& path, std::uint64_t& parameter) {
        const auto begin = pattern.find('{');
        if(begin == std::string::npos) {
            return false;
        }
        const auto end = pattern.find('}', begin);
        if(end == std::string::npos) {
            return false;
        }
        const std::string_view prefix(pattern.data(), begin);
        const std::string_view suffix(pattern.data() + end + 1, pattern.size() - end - 1);
        if(path.size() < prefix.size() + suffix.size() || !std::string_view(path).starts_with(prefix) || !std::string_view(path).ends_with(suffix)) {
            return false;
        }
        const std::string_view value(path.data() + prefix.size(), path.size() - prefix.size() - suffix.size());
        const auto [parsed_end, error] = std::from_chars(value.data(), value.data() + value.size(), parameter);
        return error == std::errc{} && parsed_end == value.data() + value.size();
    }
    std::vector<Route> routes_;
};
}