#pragma once
// Standard Library Includes
#include <cstdint>
#include <expected>
#include <span>
#include <string>
#include <utility>
#include <vector>
// Third-Party Library Includes
#include <llhttp.h>

struct HttpRequest
{
    std::string method;
    std::string url;
    uint8_t http_major = 0;
    uint8_t http_minor = 0;
    std::vector<std::pair<std::string, std::string>> headers;
    std::vector<std::byte> body;
};

using RequestList = std::vector<HttpRequest>;

class HttpRequestParser
{
    enum class State
    {
        Idle,
        Parsing,
        Completed,
        Error
    };

  public:
    HttpRequestParser();

    bool in_error_state() const noexcept
    {
        return m_state == State::Error;
    }

    std::expected<void, std::string> parse(std::span<const std::byte> data);

    size_t get_number_of_completed_requests() const noexcept
    {
        return m_completed_requests.size();
    }

    void get_completed_requests(RequestList &out_requests)
    {
        std::swap(out_requests, m_completed_requests);
        m_completed_requests = {};
    }

    void reset();

  private:
    static HttpRequestParser &from_llhttp(llhttp_t *parser);
    void commit_pending_header();

    /*1*/ static int on_message_complete(llhttp_t *parser);
    /*2*/ static int on_url(llhttp_t *parser, const char *ptr, size_t length);
    /*3*/ static int on_method(llhttp_t *parser, const char *ptr, size_t length);
    /*4*/ static int on_version(llhttp_t *parser, const char *ptr, size_t length);
    /*5*/ static int on_header_field(llhttp_t *parser, const char *ptr, size_t length);
    /*6*/ static int on_header_value(llhttp_t *parser, const char *ptr, size_t length);
    /*7*/ static int on_body(llhttp_t *parser, const char *ptr, size_t length);

    llhttp_t m_parser{};
    llhttp_settings_t m_settings{};
    State m_state{State::Idle};
    RequestList m_completed_requests;
    HttpRequest m_current_request;
    std::string m_current_header_field;
    std::string m_current_header_value;

    enum class HeaderState
    {
        None,
        Field,
        Value
    };
    HeaderState m_header_state{HeaderState::None};
};

struct HttpResponse
{
    uint8_t http_major = 1;
    uint8_t http_minor = 1;
    uint16_t status_code;
    std::string reason_phrase;
    std::vector<std::pair<std::string, std::string>> headers;
    std::vector<std::byte> body;

    void serialize_into(std::vector<std::byte> &) const;
};