#include "./request.hpp"

#include <mutex>

#include "./curl_wrappers.hpp"

namespace mijin
{
namespace
{
bool gCurlInited = false;
std::mutex gCurlInitMutex;

class CURLGuard
{
public:
    ~CURLGuard() MIJIN_NOEXCEPT
    {
        if (gCurlInited)
        {
            curl_global_cleanup();
        }
    }
} gCURLGuard [[maybe_unused]];

struct ReadData
{
    mijin::TypelessBuffer* buffer;
    std::size_t pos;
};

bool initCURL() MIJIN_NOEXCEPT
{
    if (gCurlInited)
    {
        return true;
    }
    const std::unique_lock initLock(gCurlInitMutex);
    if (gCurlInited)
    {
        return true;
    }
    gCurlInited = (curl_global_init(0) == CURLE_OK);
    return gCurlInited;
}

std::size_t writeCallback(char* ptr, std::size_t /* size */, std::size_t nmemb, void* userdata) noexcept
{
    TypelessBuffer& body = *static_cast<TypelessBuffer*>(userdata);
    body.append(std::span<const char>(ptr, nmemb));
    return nmemb;
}

std::size_t readCallback(char* ptr, std::size_t size, std::size_t nmemb, void* userdata) noexcept
{
    ReadData& data = *static_cast<ReadData*>(userdata);
    const std::size_t bytesToRead = std::min(size * nmemb, data.buffer->byteSize() - data.pos);
    std::memcpy(ptr, static_cast<std::byte*>(data.buffer->data()) + data.pos, bytesToRead);
    data.pos += bytesToRead;
    
    return bytesToRead;
}
}

Task<StreamResult<HTTPResponse>> c_request(const URL& url, HTTPRequestOptions options) MIJIN_NOEXCEPT
{
    ReadData readData;
    
    if (!initCURL())
    {
        co_return StreamError::UNKNOWN_ERROR;
    }
    
    curl::CurlEasy easy;
    if (!easy.init())
    {
        co_return StreamError::UNKNOWN_ERROR;
    }
    
    curl::SList requestHeaders;
    for (const auto& [name, value] : options.headers)
    {
        requestHeaders.append(std::format("{}: {}", name, value).c_str());
    }

#define HANDLE_CURL_RESULT(result)                              \
    if (const curl::Error error = (result); !error.isSuccess()) \
    {                                                           \
        co_return StreamError::UNKNOWN_ERROR;                   \
    }
    HANDLE_CURL_RESULT(easy.setHeaders(std::move(requestHeaders)))

    if (options.method == http_method::POST)
    {
        HANDLE_CURL_RESULT(easy.setPostFields(options.body.makeSpan<const char>().data()))
    }
    else if (options.method == http_method::PUT)
    {
        HANDLE_CURL_RESULT(easy.setUpload(true))
        HANDLE_CURL_RESULT(easy.setInFileSize(options.body.byteSize()));
        HANDLE_CURL_RESULT(easy.setReadFunction(&readCallback));
        readData.buffer = &options.body;
        readData.pos = 0;
        HANDLE_CURL_RESULT(easy.setReadData(&readData));
    }
    else if (options.method == http_method::HEAD)
    {
        HANDLE_CURL_RESULT(easy.setNoBody(true))
    }
    else if (options.method != http_method::GET)
    {
        // different option, let's do our best
        HANDLE_CURL_RESULT(easy.setCustomRequest(true))
        if (!options.body.empty())
        {
            HANDLE_CURL_RESULT(easy.setUpload(true))
            HANDLE_CURL_RESULT(easy.setInFileSize(options.body.byteSize()));
            HANDLE_CURL_RESULT(easy.setReadFunction(&readCallback));
            readData.buffer = &options.body;
            readData.pos = 0;
            HANDLE_CURL_RESULT(easy.setReadData(&readData));
        }
    }
    
    HANDLE_CURL_RESULT(easy.setURL(url))
    HANDLE_CURL_RESULT(easy.setWriteFunction(&writeCallback))
    TypelessBuffer body;
    HANDLE_CURL_RESULT(easy.setWriteData(&body))
    HANDLE_CURL_RESULT(easy.perform())
#undef HANDLE_CURL_RESULT
    
    HTTPResponse response = {
        .body = std::move(body)
    };
    if (const curl::Result<int> httpVersion = easy.getHTTPVersion(); httpVersion.isSuccess())
    {
        switch (*httpVersion)
        {
        case CURL_HTTP_VERSION_1_0:
            response.version = {1, 0};
            break;
        case CURL_HTTP_VERSION_1_1:
            response.version = {1, 1};
            break;
        case CURL_HTTP_VERSION_2_0:
            response.version = {2, 0};
            break;
        case CURL_HTTP_VERSION_3:
            response.version = {3, 0};
            break;
        default:
            MIJIN_ERROR("Unknown CURL http version returned.");
            response.version = {1, 0};
            break;
        }
    }
    else
    {
        co_return StreamError::UNKNOWN_ERROR;
    }
    if (const curl::Result<int> status = easy.getStatus(); status.isSuccess())
    {
        response.status = *status;
    }
    else
    {
        co_return StreamError::UNKNOWN_ERROR;
    }

    if (curl::Result<std::multimap<std::string, std::string>> headers = easy.getResponseHeaders(); headers.isSuccess())
    {
        response.headers = std::move(*headers);
    }
    else
    {
        co_return StreamError::UNKNOWN_ERROR;
    }

    co_return response;
}
} // namespace mijin