#pragma once

#include "types.hh"
#include "hash.hh"
#include "config.hh"

#include <string>
#include <future>

namespace nix {

struct FileTransferSettings : Config
{
    Setting<bool> enableHttp2{this, true, "http2",
        "Whether to enable HTTP/2 support."};

    Setting<std::string> userAgentSuffix{this, "", "user-agent-suffix",
        "String appended to the user agent in HTTP requests."};

    Setting<size_t> httpConnections{
        this, 25, "http-connections",
        R"(
          The maximum number of parallel TCP connections used to fetch
          files from binary caches and by other downloads. It defaults
          to 25. 0 means no limit.
        )",
        {"binary-caches-parallel-connections"}};

    Setting<unsigned long> connectTimeout{
        this, 0, "connect-timeout",
        R"(
          The timeout (in seconds) for establishing connections in the
          binary cache substituter. It corresponds to `curl`’s
          `--connect-timeout` option. A value of 0 means no limit.
        )"};

    Setting<unsigned long> stalledDownloadTimeout{
        this, 300, "stalled-download-timeout",
        R"(
          The timeout (in seconds) for receiving data from servers
          during download. Nix cancels idle downloads after this
          timeout's duration.
        )"};

    Setting<unsigned int> tries{this, 5, "download-attempts",
        "How often Nix will attempt to download a file before giving up."};
};

extern FileTransferSettings fileTransferSettings;

struct FileTransferRequest
{
    std::string uri;
    Headers headers;
    std::string expectedETag;
    bool verifyTLS = true;
    bool head = false;
    size_t tries = fileTransferSettings.tries;
    unsigned int baseRetryTimeMs = 250;
    ActivityId parentAct;
    bool decompress = true;
    std::optional<std::string> data;
    std::string mimeType;
    std::function<void(std::string_view data)> dataCallback;

    FileTransferRequest(std::string_view uri)
        : uri(uri), parentAct(getCurActivity()) { }

    std::string verb()
    {
        return data ? "upload" : "download";
    }
};

struct FileTransferResult
{
    bool cached = false;
    std::string etag;
    std::string effectiveUri;
    std::string data;
    uint64_t bodySize = 0;
};

class Store;

struct FileTransfer
{
    virtual ~FileTransfer() { }

    /* Enqueue a data transfer request, returning a future to the result of
       the download. The future may throw a FileTransferError
       exception. */
    virtual void enqueueFileTransfer(const FileTransferRequest & request,
        Callback<FileTransferResult> callback) = 0;

    std::future<FileTransferResult> enqueueFileTransfer(const FileTransferRequest & request);

    /* Synchronously download a file. */
    FileTransferResult download(const FileTransferRequest & request);

    /* Synchronously upload a file. */
    FileTransferResult upload(const FileTransferRequest & request);

    /* Download a file, writing its data to a sink. The sink will be
       invoked on the thread of the caller. */
    void download(FileTransferRequest && request, Sink & sink);

    enum Error { NotFound, Forbidden, Misc, Transient, Interrupted };
};

/* Return a shared FileTransfer object. Using this object is preferred
   because it enables connection reuse and HTTP/2 multiplexing. */
ref<FileTransfer> getFileTransfer();

/* Return a new FileTransfer object. */
ref<FileTransfer> makeFileTransfer();

class FileTransferError : public Error
{
public:
    FileTransfer::Error error;
    std::optional<std::string> response; // intentionally optional

    template<typename... Args>
    FileTransferError(FileTransfer::Error error, std::optional<std::string> response, const Args & ... args);
};

}
