// DragonX Wallet - ImGui Edition
// Copyright 2024-2026 The Hush Developers
// Released under the GPLv3

#pragma once

#include <string>
#include <vector>
#include <mutex>
#include <atomic>
#include <chrono>
#include <thread>
#include <cstdint>
#include <filesystem>
#include <functional>
#include <system_error>

namespace dragonx {
namespace util {

/**
 * @brief Bootstrap downloader + extractor for DRAGONX blockchain data.
 *
 * Downloads a blockchain snapshot zip from bootstrap.dragonx.is, verifies
 * SHA-256 / MD5 checksums, extracts it into the DRAGONX data directory
 * (skipping wallet.dat), and cleans old chain data before extraction.
 * All work runs on a background thread; progress is queried thread-safely
 * from the UI thread.
 *
 * The old chain data is removed only after a preflight passes (every archive entry is safe and the
 * disk has room for the extracted data). From that point the run is not cancellable by the user
 * (Progress::cancellable), and a failed or aborted extraction removes the partial chain again before
 * the result is published, so dragonxd never starts on a half-written blocks/ + chainstate/.
 */
class Bootstrap {
public:
    enum class State {
        Idle,
        Downloading,
        Verifying,
        Extracting,
        Completed,
        Failed
    };

    struct Progress {
        State   state          = State::Idle;
        double  downloaded_bytes = 0;
        double  total_bytes    = 0;       // 0 if server doesn't send Content-Length
        float   percent        = 0.0f;    // 0..100
        std::string status_text;          // human-readable status
        std::string error;                // non-empty on failure
        bool    cancellable    = true;    // false from the removal of the old chain data onwards
    };

    /// What extract() would write: the preflight result for an archive.
    struct ArchivePlan {
        bool          ok = false;
        std::uint64_t bytes = 0;          // uncompressed bytes of the members that would be extracted
        std::string   error;              // set when !ok
    };

    using DaemonUpFn = std::function<bool()>;
    using SpaceFn = std::function<std::filesystem::space_info(const std::string&, std::error_code&)>;

    Bootstrap() = default;
    ~Bootstrap();

    // Non-copyable
    Bootstrap(const Bootstrap&) = delete;
    Bootstrap& operator=(const Bootstrap&) = delete;

    /// Base URL for bootstrap downloads (zip + checksum files).
    static constexpr const char* kBaseUrl = "https://bootstrap.dragonx.is";
    static constexpr const char* kMirrorUrl = "https://bootstrap2.dragonx.is";
    static constexpr const char* kZipName = "DRAGONX.zip";

    /// Start the bootstrap process on a background thread.
    /// @param dataDir  Path to DRAGONX data dir (e.g. ~/.hush/DRAGONX/)
    /// @param url      Bootstrap zip URL
    void start(const std::string& dataDir,
               const std::string& url = "https://bootstrap.dragonx.is/DRAGONX.zip");

    /// Test seam: run only the install half (daemon-exit wait, preflight, clean, extract) on a local zip,
    /// skipping the download and checksum steps. daemonUp defaults to the real probe, spaceFn to
    /// std::filesystem::space.
    void startFromZip(const std::string& dataDir, const std::string& zipPath,
                      DaemonUpFn daemonUp = {}, SpaceFn spaceFn = {});

    /// Cancel an in-progress download/extract. Unconditional: for quit and the destructor, which may abort
    /// the destructive window too (the partial chain is then removed again).
    void cancel();

    /// The user's Cancel: refused (returns false, nothing changes) once the destructive window has started
    /// (Progress::cancellable false). The window's start re-checks the request under the same lock, so a
    /// click either lands before the old chain data is touched or not at all.
    bool requestCancel();

    /// Quit: true once leaving the worker to the process exit can no longer leave a part-replaced chain: it
    /// has finished, or it is cancelled and has not opened the destructive window (the window's start
    /// re-checks the cancel under the same lock, so it never will).
    bool safeToAbandon() const;

    /// Quit: cancel() and wait for the worker until `deadline`. True = finished (the object can be destroyed);
    /// false = still running, and the caller must leave it to the process exit (destroying it would join).
    bool cancelAndWait(std::chrono::steady_clock::time_point deadline);

    /// Thread-safe read of current progress.
    Progress getProgress() const;

    /// Whether the operation is finished (success or failure). True only once the worker has made its
    /// last filesystem change.
    bool isDone() const;

    /// Format a byte count as human-readable string (e.g. "1.24 GB")
    static std::string formatSize(double bytes);

    /// Preflight: open the zip, refuse it if any entry is unsafe (zip-slip; also any ':', an 8.3 "~N"
    /// alias, or a component of only dots/spaces other than ".") or unreadable, and sum the
    /// uncompressed size of the members extract() would write (directories and protected names excluded).
    static ArchivePlan planArchive(const std::string& zipPath);

    /// Bytes that cleanChainData() would free on the data dir's filesystem: regular files under
    /// blocks/, chainstate/ and notarizations/. A symlinked directory (or file) counts 0, since only the
    /// link is removed.
    static std::uint64_t reclaimableBytes(const std::string& dataDir);

    /// False = refuse (with *msg set). Needs avail + reclaimable >= needed + max(256 MiB, needed / 20).
    /// "Unknown" (capacity 0 or avail == UINT64_MAX; the caller also treats an error as unknown) returns
    /// true. avail 0 with a known capacity is a full disk, which is a refusal.
    static bool spaceSufficient(std::uint64_t needed, std::uint64_t avail, std::uint64_t capacity,
                                std::uint64_t reclaimable, std::string* msg);

    /// Snapshot members that are never extracted: any wallet* name, database/, *.conf, .cookie, and
    /// top-level *.dat other than fee_estimates/peers/banlist. Judged case-insensitively on the name the
    /// member lands on: "." components dropped, trailing dots/spaces and an NTFS stream suffix (":...")
    /// stripped from each component, so "./wallet.dat" and "DRAGONX.conf." are protected too.
    static bool isProtectedEntry(const std::string& name);

    /// First whitespace-delimited token of a checksum file, lowercased, iff it is exactly
    /// expectedHexLen hex chars; "" otherwise (an HTTP error page is never a checksum).
    static std::string parseChecksumFile(const std::string& content, std::size_t expectedHexLen);

    enum class ResumeAction { Fresh, TruncateAndFresh, ReuseComplete, RangedGet };
    /// Pure, no-I/O. authoritative = HEAD was 2xx with a positive Content-Length.
    static ResumeAction decideResume(long long existingBytes, bool authoritative, long long remoteSize);

private:
    mutable std::mutex mutex_;
    Progress progress_;
    std::atomic<bool> cancel_requested_{false};
    std::thread worker_;
    std::atomic<bool> worker_running_{false};

    // Worker bodies. The caller sets worker_running_ = false after they return; each one publishes its
    // terminal state (Failed/Completed) as its last action.
    void runDownloadAndInstall(const std::string& dataDir, const std::string& url);
    void installFromZip(const std::string& dataDir, const std::string& zipPath,
                        const DaemonUpFn& daemonUp, const SpaceFn& spaceFn);
    void beginRun();

    bool download(const std::string& url, const std::string& destZip);
    /// Never publishes a state: returns false with *err set.
    bool extract(const std::string& zipPath, const std::string& dataDir, std::string* err);
    /// True iff blocks/, chainstate/ and notarizations/ are absent afterwards.
    bool cleanChainData(const std::string& dataDir);
    void setProgress(State state, const std::string& text, double downloaded = 0, double total = 0);

    /// Compute SHA-256 of a file, return lowercase hex digest.
    /// pctBase/pctRange map file progress onto a portion of the overall percent.
    std::string computeSHA256(const std::string& filePath, float pctBase = 0.0f, float pctRange = 100.0f);

    /// Compute MD5 of a file, return lowercase hex digest.
    /// pctBase/pctRange map file progress onto a portion of the overall percent.
    std::string computeMD5(const std::string& filePath, float pctBase = 0.0f, float pctRange = 100.0f);

    /// Verify downloaded zip against remote checksums. Returns true if valid.
    bool verifyChecksums(const std::string& zipPath, const std::string& baseUrl);

    struct RemoteInfo { bool transportOk = false; long httpCode = 0; long long size = -1; };
    /// HEAD the remote file. transportOk=false on any curl error; size=-1 when absent.
    RemoteInfo getRemoteFileSize(const std::string& url);

    /// Byte offset of the partial file when resuming a download.
    /// Added to dlnow in progress reports so the bar reflects true total.
    double resume_offset_{0};

    /// Set by download() on failure (worker thread only): the CURLcode of the transfer and, for a
    /// failure that is not a transfer error, the reason.
    int last_curl_{0};
    std::string download_error_;

    /// Set by verifyChecksums (worker thread only): true only on a real digest MISMATCH, so the caller
    /// deletes the archive only then - never for a missing/unusable sidecar or a transient fetch error.
    bool last_verify_mismatch_{false};

    // libcurl progress callback (static → calls into instance via clientp)
    static int progressCallback(void* clientp, long long dltotal, long long dlnow,
                                long long ultotal, long long ulnow);
};

} // namespace util
} // namespace dragonx