tauri_plugin_hdiff_update/

file_update.rs

use std::{
    fs,
    path::{Path, PathBuf},
    process::{Child, Command},
    thread,
    time::{Duration, SystemTime, UNIX_EPOCH},
};

use fs2::FileExt;
use hdiff_update_core::{
    copy_managed_tree, ensure_available_space, normalize_managed_paths, normalize_relative_path,
    path_for_manifest_entry, prepare_directory_update, read_directory_manifest_file,
    read_directory_transaction, sha256_file, verify_directory_manifest_signature_with_keys,
    verify_file_tree, write_directory_transaction, write_json_file_atomic,
    DirectoryTransactionState, DownloadEvent, Error as CoreError, HttpHeader,
    PrepareDirectoryUpdateOptions, PreparedDirectoryUpdate, PreparedDirectoryUpdateKind,
};
use serde::{Deserialize, Serialize};
use tauri::{ipc::Channel, AppHandle, Manager, Runtime, State};

#[cfg(windows)]
use std::{
    ffi::OsStr,
    os::windows::{ffi::OsStrExt, process::CommandExt},
};
#[cfg(windows)]
use windows_sys::Win32::{
    Foundation::{
        CloseHandle, ERROR_CANCELLED, ERROR_ELEVATION_REQUIRED, HANDLE, WAIT_OBJECT_0, WAIT_TIMEOUT,
    },
    Storage::FileSystem::{
        MoveFileExW, MOVEFILE_REPLACE_EXISTING, MOVEFILE_WRITE_THROUGH, SYNCHRONIZE,
    },
    System::Threading::{
        GetExitCodeProcess, GetProcessId, OpenProcess, WaitForSingleObject,
        PROCESS_QUERY_LIMITED_INFORMATION,
    },
    UI::{
        Shell::{ShellExecuteExW, SEE_MASK_NOASYNC, SEE_MASK_NOCLOSEPROCESS, SHELLEXECUTEINFOW},
        WindowsAndMessaging::SW_SHOWNORMAL,
    },
};

#[cfg(windows)]
const CREATE_NO_WINDOW: u32 = 0x0800_0000;
const FILE_UPDATE_ROOT: &str = "file-updates";
const SUPERVISOR_ARGUMENT: &str = "--hdiff-update-supervisor";
const ELEVATED_ARGUMENT: &str = "--hdiff-update-elevated";
const HEALTH_FILE: &str = "health.ok";
const RESULT_FILE: &str = "result.json";
const ROLLBACK_REQUEST_FILE: &str = "rollback.request";
const LAUNCHED_PID_FILE: &str = "launched.pid";
const MANIFEST_FILE: &str = "manifest.json";
const STAGING_DIR: &str = "staged";
#[cfg(windows)]
const FILE_OPERATION_RETRY_SECS: u64 = 15;
#[cfg(windows)]
const COMMIT_DISK_RESERVE_BYTES: u64 = 64 * 1024 * 1024;

#[derive(Debug, Clone, Copy)]
pub struct FileUpdateHelperConfig {
    pub application_id: &'static str,
    pub public_keys: &'static [&'static str],
    pub main_executable: &'static str,
    pub managed_paths: &'static [&'static str],
    pub hpatchz_relative_path: &'static str,
}

#[derive(Debug, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct FileUpdateCommandError {
    pub message: String,
}

impl<E> From<E> for FileUpdateCommandError
where
    E: std::fmt::Display,
{
    fn from(error: E) -> Self {
        Self {
            message: error.to_string(),
        }
    }
}

#[derive(Debug, Clone, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct PrepareFileUpdateOptions {
    pub manifest_url: String,
    pub current_version: String,
    pub expected_version: String,
    #[serde(default)]
    pub headers: Vec<HttpHeader>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub timeout_secs: Option<u64>,
}

#[derive(Debug, Clone, Serialize)]
#[serde(tag = "status", rename_all = "camelCase")]
pub enum PrepareFileUpdateResult {
    Prepared {
        update: PreparedDirectoryUpdate,
    },
    AlreadyPrepared {
        update: PreparedDirectoryUpdate,
    },
    Fallback {
        reason: String,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        detail: Option<String>,
    },
}

#[derive(Debug, Clone, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct LaunchFileUpdateOptions {
    pub transaction_path: PathBuf,
}

#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct LaunchFileUpdateResult {
    pub pid: u32,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
enum HelperResultState {
    AwaitingHealth,
    Committed,
    RolledBack,
    Failed,
    RecoveryFailed,
    HealthTimeout,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
struct HelperResult {
    state: HelperResultState,
    updated_at_ms: u64,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    message: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
struct PreparedPointer {
    transaction_path: PathBuf,
    target_version: String,
    target_tree_sha256: String,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
enum JournalOperationState {
    Pending,
    BackedUp,
    Installed,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
struct JournalOperation {
    path: String,
    is_directory: bool,
    state: JournalOperationState,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
struct CommitJournal {
    transaction_id: String,
    state: DirectoryTransactionState,
    operations: Vec<JournalOperation>,
    updated_at_ms: u64,
}

struct ValidatedContext {
    transaction_path: PathBuf,
    transaction_root: PathBuf,
    transaction: hdiff_update_core::DirectoryUpdateTransaction,
    source: hdiff_update_core::FileTreeManifest,
    target: hdiff_update_core::FileTreeManifest,
    staging_path: PathBuf,
    result_path: PathBuf,
    install_root: PathBuf,
    managed_paths: Vec<String>,
}

#[tauri::command]
pub async fn prepare_file_update<R: Runtime>(
    app: AppHandle<R>,
    config: State<'_, FileUpdateHelperConfig>,
    options: PrepareFileUpdateOptions,
    on_event: Channel<DownloadEvent>,
) -> Result<PrepareFileUpdateResult, FileUpdateCommandError> {
    if app.config().identifier != config.application_id {
        return Err(FileUpdateCommandError::from(
            "file update plugin application id does not match the Tauri identifier",
        ));
    }
    let public_keys = trusted_public_keys(&config);
    if public_keys.is_empty() {
        return Ok(PrepareFileUpdateResult::Fallback {
            reason: "updaterNotConfigured".to_string(),
            detail: Some(
                "file update trusted public-key ring is not compiled into the application"
                    .to_string(),
            ),
        });
    }
    let install_root = current_install_root()?;
    let cache_dir = file_update_cache_root(&app)?;
    let hpatchz_path =
        path_for_manifest_entry(&app.path().resource_dir()?, config.hpatchz_relative_path)?;
    let configured_paths = normalize_managed_paths(
        &config
            .managed_paths
            .iter()
            .map(|path| (*path).to_string())
            .collect::<Vec<_>>(),
    )?;
    let hpatchz_path =
        validate_bundled_patch_tool(&install_root, &hpatchz_path, &configured_paths)?;

    let result = prepare_directory_update(
        PrepareDirectoryUpdateOptions {
            manifest_url: options.manifest_url,
            application_id: config.application_id.to_string(),
            install_root,
            managed_paths: configured_paths,
            current_version: options.current_version,
            expected_version: options.expected_version,
            platform: None,
            cache_dir,
            hpatchz_path: Some(hpatchz_path),
            signature_public_keys: public_keys,
            require_signature: true,
            headers: options.headers,
            timeout_secs: options.timeout_secs,
        },
        |event| {
            let _ = on_event.send(event);
        },
    )
    .await;

    match result {
        Ok(update) if update.kind == PreparedDirectoryUpdateKind::AlreadyPrepared => {
            Ok(PrepareFileUpdateResult::AlreadyPrepared { update })
        }
        Ok(update) => Ok(PrepareFileUpdateResult::Prepared { update }),
        Err(error) => Ok(PrepareFileUpdateResult::Fallback {
            reason: fallback_reason(&error).to_string(),
            detail: Some(fallback_detail(&error)),
        }),
    }
}

#[tauri::command]
pub async fn launch_file_update<R: Runtime>(
    app: AppHandle<R>,
    options: LaunchFileUpdateOptions,
) -> Result<LaunchFileUpdateResult, FileUpdateCommandError> {
    let cache_root = file_update_cache_root(&app)?;
    fs::create_dir_all(&cache_root)?;
    let lock = fs::OpenOptions::new()
        .create(true)
        .truncate(false)
        .read(true)
        .write(true)
        .open(cache_root.join("lock"))?;
    lock.lock_exclusive()?;
    let transaction_path = validate_transaction_path(&cache_root, &options.transaction_path)?;
    let mut transaction = read_directory_transaction(&transaction_path)?;
    if transaction.application_id != app.config().identifier {
        return Err(FileUpdateCommandError::from(
            "file update transaction belongs to another application",
        ));
    }
    if transaction.state != DirectoryTransactionState::Ready {
        return Err(FileUpdateCommandError::from(format!(
            "file update transaction is not ready: {:?}",
            transaction.state
        )));
    }

    let current_exe = std::env::current_exe()?;
    let transaction_root = transaction_path
        .parent()
        .ok_or_else(|| FileUpdateCommandError::from("transaction path has no parent"))?;
    let helper_dir = transaction_root.join("helper");
    fs::create_dir_all(&helper_dir)?;
    let helper_path = helper_dir.join(
        current_exe
            .file_name()
            .unwrap_or_else(|| OsStr::new("update-helper.exe")),
    );
    fs::copy(&current_exe, &helper_path)?;
    let source_digest = sha256_file(&current_exe)?;
    let helper_digest = sha256_file(&helper_path)?;
    if source_digest.sha256 != helper_digest.sha256 {
        return Err(FileUpdateCommandError::from(
            "copied file update helper failed SHA-256 verification",
        ));
    }

    transaction.state = DirectoryTransactionState::SupervisorStarted;
    transaction.updated_at_ms = now_millis();
    write_directory_transaction(&transaction_path, &transaction)?;

    let mut command = Command::new(&helper_path);
    command
        .arg(SUPERVISOR_ARGUMENT)
        .arg(&transaction_path)
        .arg(std::process::id().to_string());
    #[cfg(windows)]
    command.creation_flags(CREATE_NO_WINDOW);
    let child = match command.spawn() {
        Ok(child) => child,
        Err(error) => {
            transaction.state = DirectoryTransactionState::Ready;
            transaction.updated_at_ms = now_millis();
            write_directory_transaction(&transaction_path, &transaction)?;
            return Err(FileUpdateCommandError::from(format!(
                "failed to start file update supervisor {}: {error}",
                helper_path.display()
            )));
        }
    };
    Ok(LaunchFileUpdateResult { pid: child.id() })
}

pub fn maybe_run_file_update_helper(
    config: &FileUpdateHelperConfig,
) -> Result<bool, FileUpdateCommandError> {
    let args = std::env::args_os().collect::<Vec<_>>();
    let Some(mode) = args.get(1).and_then(|value| value.to_str()) else {
        return maybe_resume_interrupted_update(config);
    };

    match mode {
        SUPERVISOR_ARGUMENT => {
            let transaction_path = args
                .get(2)
                .map(PathBuf::from)
                .ok_or_else(|| FileUpdateCommandError::from("missing transaction path"))?;
            let parent_pid = args
                .get(3)
                .and_then(|value| value.to_str())
                .ok_or_else(|| FileUpdateCommandError::from("missing parent process id"))?
                .parse::<u32>()
                .map_err(FileUpdateCommandError::from)?;
            run_supervisor(config, &transaction_path, parent_pid)?;
            Ok(true)
        }
        ELEVATED_ARGUMENT => {
            let transaction_path = args
                .get(2)
                .map(PathBuf::from)
                .ok_or_else(|| FileUpdateCommandError::from("missing transaction path"))?;
            run_elevated_worker(config, &transaction_path)?;
            Ok(true)
        }
        _ => maybe_resume_interrupted_update(config),
    }
}

pub fn confirm_file_update_startup<R: Runtime>(
    app: &AppHandle<R>,
) -> Result<bool, FileUpdateCommandError> {
    let cache_root = file_update_cache_root(app)?;
    let transactions_root = cache_root.join("transactions");
    if !transactions_root.is_dir() {
        return Ok(false);
    }
    let current_version = app.package_info().version.to_string();
    for entry in fs::read_dir(transactions_root)? {
        let entry = entry?;
        let transaction_path = entry.path().join("transaction.json");
        if !transaction_path.is_file() {
            continue;
        }
        let transaction = match read_directory_transaction(&transaction_path) {
            Ok(transaction) => transaction,
            Err(_) => continue,
        };
        if transaction.application_id != app.config().identifier
            || transaction.target_version != current_version
            || !matches!(
                transaction.state,
                DirectoryTransactionState::AwaitingHealth
                    | DirectoryTransactionState::HealthTimeout
            )
        {
            continue;
        }
        fs::write(entry.path().join(HEALTH_FILE), b"ok")?;
        return Ok(true);
    }
    Ok(false)
}

#[cfg(windows)]
fn maybe_resume_interrupted_update(
    config: &FileUpdateHelperConfig,
) -> Result<bool, FileUpdateCommandError> {
    if trusted_public_keys(config).is_empty() {
        return Ok(false);
    }
    let cache_root = match helper_cache_root(config) {
        Ok(path) => path,
        Err(_) => return Ok(false),
    };
    let pointer_path = cache_root.join("prepared.json");
    if !pointer_path.is_file() {
        return Ok(false);
    }
    let pointer: PreparedPointer = serde_json::from_slice(&fs::read(pointer_path)?)?;
    let transaction_path = match validate_transaction_path(&cache_root, &pointer.transaction_path) {
        Ok(path) => path,
        Err(_) => return Ok(false),
    };
    let transaction = read_directory_transaction(&transaction_path)?;
    let transaction_root = transaction_path
        .parent()
        .ok_or_else(|| FileUpdateCommandError::from("transaction path has no parent"))?;
    let health_exists = transaction_root.join(HEALTH_FILE).is_file();
    let result = read_helper_result(&transaction_root.join(RESULT_FILE)).ok();
    if result.as_ref().is_some_and(|result| {
        matches!(
            result.state,
            HelperResultState::Committed
                | HelperResultState::RolledBack
                | HelperResultState::Failed
        )
    }) {
        return Ok(false);
    }

    let launched_process_running = read_launched_pid(transaction_root)
        .map(process_is_running)
        .unwrap_or(false);
    let should_resume = match transaction.state {
        DirectoryTransactionState::Committing => true,
        DirectoryTransactionState::AwaitingHealth | DirectoryTransactionState::HealthTimeout => {
            health_exists || !launched_process_running
        }
        DirectoryTransactionState::SupervisorStarted => result.is_none(),
        _ => false,
    };
    if !should_resume {
        return Ok(false);
    }

    let current_exe = std::env::current_exe()?;
    let helper_dir = transaction_root.join("helper");
    fs::create_dir_all(&helper_dir)?;
    let helper_path = helper_dir.join(
        current_exe
            .file_name()
            .unwrap_or_else(|| OsStr::new("update-helper.exe")),
    );
    fs::copy(&current_exe, &helper_path)?;
    if sha256_file(&current_exe)?.sha256 != sha256_file(&helper_path)?.sha256 {
        return Err(FileUpdateCommandError::from(
            "recovery helper failed SHA-256 verification",
        ));
    }
    let mut command = Command::new(helper_path);
    command
        .arg(SUPERVISOR_ARGUMENT)
        .arg(transaction_path)
        .arg(std::process::id().to_string())
        .creation_flags(CREATE_NO_WINDOW);
    command.spawn()?;
    Ok(true)
}

#[cfg(not(windows))]
fn maybe_resume_interrupted_update(
    _config: &FileUpdateHelperConfig,
) -> Result<bool, FileUpdateCommandError> {
    Ok(false)
}

fn fallback_reason(error: &CoreError) -> &'static str {
    match error {
        CoreError::SignatureMissing
        | CoreError::SignaturePublicKeyMissing
        | CoreError::SignatureVerificationFailed
        | CoreError::InvalidKeyMaterial { .. } => "manifestSignatureInvalid",
        CoreError::UnexpectedVersion { .. } => "versionMismatch",
        CoreError::InvalidVersion { .. } | CoreError::NonUpgradeVersion { .. } => "versionMismatch",
        CoreError::MissingPlatform { .. } => "unsupportedPlatform",
        CoreError::NoMatchingDelta { .. } => "noMatchingDelta",
        CoreError::HashMismatch { .. }
        | CoreError::SizeMismatch { .. }
        | CoreError::DownloadLimitExceeded { .. } => "artifactVerificationFailed",
        CoreError::InsufficientDiskSpace { .. } => "insufficientDiskSpace",
        CoreError::Http(_)
        | CoreError::UnexpectedHttpStatus { .. }
        | CoreError::Url(_)
        | CoreError::UnsupportedUrl(_) => "downloadFailed",
        CoreError::InsecureTransport { .. } => "insecureTransport",
        CoreError::ProcessFailed { .. } => "patchFailed",
        CoreError::UnsupportedAlgorithm(_) => "unsupportedAlgorithm",
        CoreError::Message(message) if message.contains("managed tree mismatch") => {
            "sourceTreeMismatch"
        }
        CoreError::Message(message) if message.contains("previous directory update") => {
            "previousCommitFailed"
        }
        _ => "directoryUpdateFailed",
    }
}

fn fallback_detail(error: &CoreError) -> String {
    match error {
        CoreError::Http(_) | CoreError::UnexpectedHttpStatus { .. } => {
            "HTTPS update request failed".to_string()
        }
        CoreError::Url(_) | CoreError::UnsupportedUrl(_) => {
            "update endpoint URL is invalid".to_string()
        }
        CoreError::InsecureTransport { .. } => {
            "production directory updates require HTTPS".to_string()
        }
        CoreError::InsufficientDiskSpace {
            required,
            available,
            ..
        } => format!(
            "not enough free disk space: required {required} bytes, available {available} bytes"
        ),
        _ => error.to_string(),
    }
}

fn trusted_public_keys(config: &FileUpdateHelperConfig) -> Vec<String> {
    config
        .public_keys
        .iter()
        .map(|key| key.trim())
        .filter(|key| !key.is_empty())
        .map(str::to_string)
        .collect()
}

fn file_update_cache_root<R: Runtime>(
    app: &AppHandle<R>,
) -> Result<PathBuf, FileUpdateCommandError> {
    Ok(app
        .path()
        .app_data_dir()?
        .join("hdiff-update")
        .join(FILE_UPDATE_ROOT))
}

fn helper_cache_root(config: &FileUpdateHelperConfig) -> Result<PathBuf, FileUpdateCommandError> {
    let app_data = std::env::var_os("APPDATA")
        .ok_or_else(|| FileUpdateCommandError::from("APPDATA is not available"))?;
    Ok(PathBuf::from(app_data)
        .join(config.application_id)
        .join("hdiff-update")
        .join(FILE_UPDATE_ROOT))
}

fn current_install_root() -> Result<PathBuf, FileUpdateCommandError> {
    let executable = std::env::current_exe()?;
    executable
        .parent()
        .map(Path::to_path_buf)
        .ok_or_else(|| FileUpdateCommandError::from("current executable has no parent directory"))
}

fn validate_bundled_patch_tool(
    install_root: &Path,
    tool_path: &Path,
    managed_paths: &[String],
) -> Result<PathBuf, FileUpdateCommandError> {
    let install_root = install_root.canonicalize()?;
    let tool_path = tool_path.canonicalize()?;
    let metadata = fs::symlink_metadata(&tool_path)?;
    if !metadata.is_file() || metadata.file_type().is_symlink() || is_reparse_point(&metadata) {
        return Err(FileUpdateCommandError::from(format!(
            "bundled patch tool is missing or is a reparse point: {}",
            tool_path.display()
        )));
    }
    let relative = tool_path.strip_prefix(&install_root).map_err(|_| {
        FileUpdateCommandError::from("bundled patch tool is outside the installation root")
    })?;
    let relative = relative
        .to_str()
        .ok_or_else(|| FileUpdateCommandError::from("bundled patch tool path is not UTF-8"))?
        .replace('\\', "/");
    let relative = normalize_relative_path(&relative)?;
    if !managed_paths
        .iter()
        .any(|managed| relative == *managed || relative.starts_with(&format!("{managed}/")))
    {
        return Err(FileUpdateCommandError::from(format!(
            "bundled patch tool is outside the managed update tree: {relative}"
        )));
    }
    Ok(tool_path)
}

fn validate_transaction_path(
    cache_root: &Path,
    transaction_path: &Path,
) -> Result<PathBuf, FileUpdateCommandError> {
    let expected_root = cache_root.join("transactions");
    let transaction_path = transaction_path.canonicalize()?;
    let expected_root = expected_root.canonicalize()?;
    if !transaction_path.starts_with(&expected_root)
        || transaction_path.file_name() != Some(OsStr::new("transaction.json"))
    {
        return Err(FileUpdateCommandError::from(format!(
            "transaction path is outside the managed cache: {}",
            transaction_path.display()
        )));
    }
    Ok(transaction_path)
}

fn validate_helper_context(
    config: &FileUpdateHelperConfig,
    transaction_path: &Path,
) -> Result<ValidatedContext, FileUpdateCommandError> {
    let public_keys = trusted_public_keys(config);
    if public_keys.is_empty() {
        return Err(FileUpdateCommandError::from(
            "file update helper trusted public-key ring is not compiled into the application",
        ));
    }
    let transaction_path = transaction_path.canonicalize()?;
    let expected_transactions_root = helper_cache_root(config)?
        .join("transactions")
        .canonicalize()?;
    if !transaction_path.starts_with(&expected_transactions_root)
        || transaction_path.file_name() != Some(OsStr::new("transaction.json"))
    {
        return Err(FileUpdateCommandError::from(format!(
            "file update transaction is outside the application cache: {}",
            transaction_path.display()
        )));
    }
    let transaction_root = transaction_path
        .parent()
        .ok_or_else(|| FileUpdateCommandError::from("transaction path has no parent"))?
        .to_path_buf();
    ensure_plain_directory(&transaction_root)?;
    let transaction = read_directory_transaction(&transaction_path)?;
    if transaction.application_id != config.application_id {
        return Err(FileUpdateCommandError::from(
            "file update helper application id mismatch",
        ));
    }
    let configured_paths = normalize_managed_paths(
        &config
            .managed_paths
            .iter()
            .map(|path| (*path).to_string())
            .collect::<Vec<_>>(),
    )?;
    if transaction.managed_paths != configured_paths {
        return Err(FileUpdateCommandError::from(
            "file update helper managed path policy mismatch",
        ));
    }
    if !configured_paths
        .iter()
        .any(|path| path.eq_ignore_ascii_case(config.main_executable))
    {
        return Err(FileUpdateCommandError::from(
            "main executable is not part of the managed path policy",
        ));
    }

    let manifest_path = transaction_root.join(MANIFEST_FILE);
    let manifest = read_directory_manifest_file(&manifest_path)?;
    verify_directory_manifest_signature_with_keys(&manifest, &public_keys)?;
    if manifest.version != transaction.target_version {
        return Err(FileUpdateCommandError::from(
            "transaction target version does not match signed manifest",
        ));
    }
    let release = manifest.platform(&transaction.platform)?.clone();
    if release.managed_paths != configured_paths {
        return Err(FileUpdateCommandError::from(
            "signed manifest managed paths do not match helper policy",
        ));
    }
    let delta = release
        .delta_from(&transaction.current_version)
        .ok_or_else(|| FileUpdateCommandError::from("signed manifest has no transaction delta"))?;
    if delta.source.tree_sha256 != transaction.source_tree_sha256
        || release.target.tree_sha256 != transaction.target_tree_sha256
        || delta.patch.sha256 != transaction.patch_sha256
        || delta.patch.size != transaction.patch_size
    {
        return Err(FileUpdateCommandError::from(
            "transaction metadata does not match signed manifest",
        ));
    }

    let install_root = transaction.install_root.canonicalize()?;
    ensure_plain_directory(&install_root)?;
    let main_executable = install_root.join(config.main_executable);
    if !main_executable.is_file() {
        return Err(FileUpdateCommandError::from(format!(
            "installed main executable is missing: {}",
            main_executable.display()
        )));
    }
    let staging_path = transaction_root.join(STAGING_DIR);
    ensure_plain_directory(&staging_path)?;
    verify_file_tree(&staging_path, &configured_paths, &release.target)?;

    Ok(ValidatedContext {
        transaction_path,
        transaction_root: transaction_root.clone(),
        transaction,
        source: delta.source.clone(),
        target: release.target,
        staging_path,
        result_path: transaction_root.join(RESULT_FILE),
        install_root,
        managed_paths: configured_paths,
    })
}

#[cfg(windows)]
fn run_supervisor(
    config: &FileUpdateHelperConfig,
    transaction_path: &Path,
    parent_pid: u32,
) -> Result<(), FileUpdateCommandError> {
    let mut context = validate_helper_context(config, transaction_path)?;
    wait_for_process_exit(parent_pid, Duration::from_secs(120))?;

    let helper = std::env::current_exe()?;
    let parameters = windows_command_line(&[
        ELEVATED_ARGUMENT.to_string(),
        context.transaction_path.to_string_lossy().to_string(),
    ]);
    let elevated = match shell_execute_elevated(&helper, &parameters) {
        Ok(process) => process,
        Err(error) => {
            context.transaction.state = DirectoryTransactionState::Failed;
            context.transaction.updated_at_ms = now_millis();
            context.transaction.failure_reason = Some(error.message.clone());
            write_directory_transaction(&context.transaction_path, &context.transaction)?;
            write_helper_result(
                &context.result_path,
                HelperResultState::Failed,
                Some(error.message.clone()),
            )?;
            let _ = cleanup_transaction_payload(&context);
            launch_installed_application(config, &context.install_root)?;
            return Ok(());
        }
    };

    let mut launched = None::<Child>;
    let mut launched_once = false;
    let mut launch_failed = false;
    let mut rollback_requested = false;
    loop {
        let wait = unsafe { WaitForSingleObject(elevated, 200) };
        let helper_result = read_helper_result(&context.result_path).ok();
        if launched.is_none()
            && !launch_failed
            && helper_result
                .as_ref()
                .is_some_and(|result| result.state == HelperResultState::AwaitingHealth)
        {
            match launch_installed_application(config, &context.install_root) {
                Ok(mut child) => {
                    if let Err(error) = write_launched_pid(&context.transaction_root, child.id()) {
                        let _ = child.kill();
                        let _ = child.wait();
                        request_rollback(
                            &context.transaction_root,
                            &format!(
                                "failed to record updated application process: {}",
                                error.message
                            ),
                        )?;
                        launch_failed = true;
                        rollback_requested = true;
                    } else {
                        launched_once = true;
                        launched = Some(child);
                    }
                }
                Err(error) => {
                    request_rollback(&context.transaction_root, &error.message)?;
                    launch_failed = true;
                    rollback_requested = true;
                }
            }
        }
        if let Some(child) = launched.as_mut() {
            if child.try_wait()?.is_some()
                && !context.transaction_root.join(HEALTH_FILE).is_file()
                && !rollback_requested
            {
                request_rollback(
                    &context.transaction_root,
                    "updated application exited before confirming startup",
                )?;
                rollback_requested = true;
            }
        }
        if wait == WAIT_OBJECT_0 {
            break;
        }
        if wait != WAIT_TIMEOUT {
            unsafe {
                CloseHandle(elevated);
            }
            return Err(FileUpdateCommandError::from(format!(
                "waiting for elevated update worker failed with code {wait}"
            )));
        }
    }

    let mut exit_code = 0_u32;
    unsafe {
        GetExitCodeProcess(elevated, &mut exit_code);
        CloseHandle(elevated);
    }
    let final_result = read_helper_result(&context.result_path).ok();
    let child_running = launched
        .as_mut()
        .map(|child| child.try_wait().map(|status| status.is_none()))
        .transpose()?
        .unwrap_or(false);
    let should_restart = match final_result.as_ref().map(|result| result.state) {
        Some(HelperResultState::Committed) => !launched_once,
        Some(HelperResultState::AwaitingHealth | HelperResultState::HealthTimeout) => {
            !child_running
        }
        Some(HelperResultState::RolledBack | HelperResultState::Failed) | None => !child_running,
        Some(HelperResultState::RecoveryFailed) => false,
    };
    if should_restart {
        let _ = launch_installed_application(config, &context.install_root)?;
    }
    if exit_code != 0 {
        return Err(FileUpdateCommandError::from(format!(
            "elevated file update worker exited with code {exit_code}"
        )));
    }
    Ok(())
}

#[cfg(not(windows))]
fn run_supervisor(
    _config: &FileUpdateHelperConfig,
    _transaction_path: &Path,
    _parent_pid: u32,
) -> Result<(), FileUpdateCommandError> {
    Err(FileUpdateCommandError::from(
        "file update supervisor is only implemented on Windows",
    ))
}

#[cfg(windows)]
fn run_elevated_worker(
    config: &FileUpdateHelperConfig,
    transaction_path: &Path,
) -> Result<(), FileUpdateCommandError> {
    let mut context = validate_helper_context(config, transaction_path)?;
    match context.transaction.state {
        DirectoryTransactionState::Committing => {
            let error =
                FileUpdateCommandError::from("interrupted directory update was rolled back");
            finish_rollback(&mut context, &error.message)?;
            return Err(error);
        }
        DirectoryTransactionState::AwaitingHealth | DirectoryTransactionState::HealthTimeout => {
            if context.transaction_root.join(HEALTH_FILE).is_file() {
                verify_file_tree(
                    &context.install_root,
                    &context.managed_paths,
                    &context.target,
                )?;
                let protected_root = protected_transaction_root(&context);
                if protected_root.exists() {
                    ensure_plain_directory(&protected_root)?;
                    fs::remove_dir_all(&protected_root)?;
                }
                context.transaction.state = DirectoryTransactionState::Committed;
                context.transaction.updated_at_ms = now_millis();
                context.transaction.failure_reason = None;
                write_directory_transaction(&context.transaction_path, &context.transaction)?;
                write_helper_result(&context.result_path, HelperResultState::Committed, None)?;
                let _ = cleanup_transaction_payload(&context);
                return Ok(());
            }

            let error = FileUpdateCommandError::from(
                "updated application did not confirm startup; rolling back",
            );
            finish_rollback(&mut context, &error.message)?;
            return Err(error);
        }
        _ => {}
    }
    context.transaction.state = DirectoryTransactionState::Committing;
    context.transaction.updated_at_ms = now_millis();
    write_directory_transaction(&context.transaction_path, &context.transaction)?;

    let commit_result = commit_update(config, &mut context);
    match commit_result {
        Ok(protected_root) => {
            context.transaction.state = DirectoryTransactionState::AwaitingHealth;
            context.transaction.updated_at_ms = now_millis();
            write_directory_transaction(&context.transaction_path, &context.transaction)?;
            write_helper_result(
                &context.result_path,
                HelperResultState::AwaitingHealth,
                None,
            )?;

            let health_path = context.transaction_root.join(HEALTH_FILE);
            let rollback_path = context.transaction_root.join(ROLLBACK_REQUEST_FILE);
            let deadline = std::time::Instant::now() + Duration::from_secs(120);
            while std::time::Instant::now() < deadline {
                if health_path.is_file() {
                    verify_file_tree(
                        &context.install_root,
                        &context.managed_paths,
                        &context.target,
                    )?;
                    if protected_root.exists() {
                        ensure_plain_directory(&protected_root)?;
                        fs::remove_dir_all(&protected_root)?;
                    }
                    context.transaction.state = DirectoryTransactionState::Committed;
                    context.transaction.updated_at_ms = now_millis();
                    context.transaction.failure_reason = None;
                    write_directory_transaction(&context.transaction_path, &context.transaction)?;
                    write_helper_result(&context.result_path, HelperResultState::Committed, None)?;
                    let _ = cleanup_transaction_payload(&context);
                    return Ok(());
                }
                if rollback_path.is_file() {
                    let reason = fs::read_to_string(&rollback_path)
                        .unwrap_or_else(|_| "updated application failed to start".to_string());
                    let error = FileUpdateCommandError::from(reason.trim().to_string());
                    finish_rollback(&mut context, &error.message)?;
                    return Err(error);
                }
                thread::sleep(Duration::from_millis(250));
            }

            let launched_process_running = read_launched_pid(&context.transaction_root)
                .map(process_is_running)
                .unwrap_or(false);
            if !launched_process_running {
                let error = FileUpdateCommandError::from(
                    "updated application did not stay running; rolling back",
                );
                finish_rollback(&mut context, &error.message)?;
                return Err(error);
            }

            context.transaction.state = DirectoryTransactionState::HealthTimeout;
            context.transaction.updated_at_ms = now_millis();
            context.transaction.failure_reason =
                Some("updated application did not confirm startup within 120 seconds".to_string());
            write_directory_transaction(&context.transaction_path, &context.transaction)?;
            write_helper_result(
                &context.result_path,
                HelperResultState::HealthTimeout,
                context.transaction.failure_reason.clone(),
            )?;
            Ok(())
        }
        Err(error) => {
            finish_rollback(&mut context, &error.message)?;
            Err(error)
        }
    }
}

#[cfg(windows)]
fn finish_rollback(
    context: &mut ValidatedContext,
    reason: &str,
) -> Result<(), FileUpdateCommandError> {
    match recover_interrupted_commit(context) {
        Ok(()) => {
            context.transaction.state = DirectoryTransactionState::RolledBack;
            context.transaction.updated_at_ms = now_millis();
            context.transaction.failure_reason = Some(reason.to_string());
            write_directory_transaction(&context.transaction_path, &context.transaction)?;
            write_helper_result(
                &context.result_path,
                HelperResultState::RolledBack,
                Some(reason.to_string()),
            )?;
            let _ = cleanup_transaction_payload(context);
            Ok(())
        }
        Err(recovery_error) => {
            let message = format!(
                "{reason}; rollback recovery failed: {}",
                recovery_error.message
            );
            context.transaction.state = DirectoryTransactionState::Committing;
            context.transaction.updated_at_ms = now_millis();
            context.transaction.failure_reason = Some(message.clone());
            write_directory_transaction(&context.transaction_path, &context.transaction)?;
            write_helper_result(
                &context.result_path,
                HelperResultState::RecoveryFailed,
                Some(message),
            )?;
            Err(recovery_error)
        }
    }
}

#[cfg(not(windows))]
fn run_elevated_worker(
    _config: &FileUpdateHelperConfig,
    _transaction_path: &Path,
) -> Result<(), FileUpdateCommandError> {
    Err(FileUpdateCommandError::from(
        "elevated file update worker is only implemented on Windows",
    ))
}

#[cfg(windows)]
fn protected_transaction_root(context: &ValidatedContext) -> PathBuf {
    context
        .install_root
        .join(".hdiff-update")
        .join(&context.transaction.transaction_id)
}

#[cfg(windows)]
fn recover_interrupted_commit(context: &ValidatedContext) -> Result<(), FileUpdateCommandError> {
    let protected_root = protected_transaction_root(context);
    if !protected_root.exists() {
        return Ok(());
    }
    ensure_plain_directory(&protected_root)?;
    let journal_path = protected_root.join("journal.json");
    if !journal_path.is_file() {
        fs::remove_dir_all(&protected_root)?;
        return Ok(());
    }
    let journal: CommitJournal = serde_json::from_slice(&fs::read(&journal_path)?)?;
    if journal.transaction_id != context.transaction.transaction_id {
        return Err(FileUpdateCommandError::from(
            "protected update journal belongs to another transaction",
        ));
    }
    let backup_root = protected_root.join("backup");
    for operation in journal.operations.iter().rev() {
        let current = context.install_root.join(&operation.path);
        let backup = backup_root.join(&operation.path);
        if operation.state == JournalOperationState::Pending && !operation.is_directory {
            if !current.is_file() {
                return Err(FileUpdateCommandError::from(format!(
                    "cannot recover file backup because the current file is missing: {}",
                    operation.path
                )));
            }
            if backup.exists() {
                remove_managed_entry(&backup)?;
            }
            continue;
        }
        if backup.exists() {
            if current.exists() {
                remove_managed_entry(&current)?;
            }
            if operation.is_directory {
                rename_with_retry(&backup, &current)?;
            } else {
                move_file_replace(&backup, &current)?;
            }
        } else if !current.exists() {
            return Err(FileUpdateCommandError::from(format!(
                "cannot recover managed path because both current and backup are missing: {}",
                operation.path
            )));
        }
    }
    verify_file_tree(
        &context.install_root,
        &context.managed_paths,
        &context.source,
    )?;
    fs::remove_dir_all(&protected_root)?;
    Ok(())
}

#[cfg(windows)]
fn commit_update(
    config: &FileUpdateHelperConfig,
    context: &mut ValidatedContext,
) -> Result<PathBuf, FileUpdateCommandError> {
    verify_file_tree(
        &context.install_root,
        &context.managed_paths,
        &context.source,
    )?;
    verify_file_tree(
        &context.staging_path,
        &context.managed_paths,
        &context.target,
    )?;
    let file_backup_bytes = context
        .source
        .files
        .iter()
        .filter(|file| context.managed_paths.contains(&file.path))
        .try_fold(0_u64, |total, file| total.checked_add(file.size))
        .ok_or_else(|| FileUpdateCommandError::from("commit disk requirement overflow"))?;
    let required_commit_bytes = context
        .target
        .total_size
        .checked_add(file_backup_bytes)
        .and_then(|size| size.checked_add(COMMIT_DISK_RESERVE_BYTES))
        .ok_or_else(|| FileUpdateCommandError::from("commit disk requirement overflow"))?;
    ensure_available_space(&context.install_root, required_commit_bytes)?;

    let update_root = context.install_root.join(".hdiff-update");
    if update_root.exists() {
        ensure_plain_directory(&update_root)?;
    } else {
        fs::create_dir(&update_root)?;
        ensure_plain_directory(&update_root)?;
    }
    let protected_root = protected_transaction_root(context);
    if protected_root.exists() {
        ensure_plain_directory(&protected_root)?;
        fs::remove_dir_all(&protected_root)?;
    }
    let new_root = protected_root.join("new");
    let backup_root = protected_root.join("backup");
    fs::create_dir_all(&backup_root)?;
    copy_managed_tree(&context.staging_path, &new_root, &context.managed_paths)?;
    verify_file_tree(&new_root, &context.managed_paths, &context.target)?;

    let journal_path = protected_root.join("journal.json");
    let mut operations = context
        .managed_paths
        .iter()
        .map(|path| JournalOperation {
            path: path.clone(),
            is_directory: context.install_root.join(path).is_dir(),
            state: JournalOperationState::Pending,
        })
        .collect::<Vec<_>>();
    operations.sort_by_key(|operation| {
        (
            operation.path.eq_ignore_ascii_case(config.main_executable),
            operation.path.to_ascii_lowercase(),
        )
    });
    let mut journal = CommitJournal {
        transaction_id: context.transaction.transaction_id.clone(),
        state: DirectoryTransactionState::Committing,
        operations,
        updated_at_ms: now_millis(),
    };
    write_json_file_atomic(&journal_path, &journal)?;

    for index in 0..journal.operations.len() {
        let operation = journal.operations[index].clone();
        let current = context.install_root.join(&operation.path);
        let replacement = new_root.join(&operation.path);
        let backup = backup_root.join(&operation.path);
        if let Some(parent) = backup.parent() {
            fs::create_dir_all(parent)?;
        }

        let result = if operation.is_directory {
            rename_with_retry(&current, &backup)
                .and_then(|_| {
                    journal.operations[index].state = JournalOperationState::BackedUp;
                    journal.updated_at_ms = now_millis();
                    write_json_file_atomic(&journal_path, &journal).map_err(core_error_to_io)?;
                    rename_with_retry(&replacement, &current)
                })
                .map(|_| ())
        } else {
            copy_file_backup(&current, &backup).and_then(|_| {
                journal.operations[index].state = JournalOperationState::BackedUp;
                journal.updated_at_ms = now_millis();
                write_json_file_atomic(&journal_path, &journal).map_err(core_error_to_io)?;
                move_file_replace(&replacement, &current)
            })
        };

        if let Err(error) = result {
            let commit_error = FileUpdateCommandError::from(format!(
                "failed to commit managed path {}: {error}",
                operation.path
            ));
            rollback_operations(context, &backup_root, &journal)?;
            return Err(commit_error);
        }
        journal.operations[index].state = JournalOperationState::Installed;
        journal.updated_at_ms = now_millis();
        write_json_file_atomic(&journal_path, &journal)?;
    }

    if let Err(error) = verify_file_tree(
        &context.install_root,
        &context.managed_paths,
        &context.target,
    ) {
        rollback_operations(context, &backup_root, &journal)?;
        return Err(FileUpdateCommandError::from(format!(
            "installed target verification failed: {error}"
        )));
    }
    journal.state = DirectoryTransactionState::AwaitingHealth;
    journal.updated_at_ms = now_millis();
    write_json_file_atomic(&journal_path, &journal)?;
    Ok(protected_root)
}

#[cfg(windows)]
fn rollback_operations(
    context: &ValidatedContext,
    backup_root: &Path,
    journal: &CommitJournal,
) -> Result<(), FileUpdateCommandError> {
    for operation in journal.operations.iter().rev() {
        if operation.state == JournalOperationState::Pending {
            continue;
        }
        let current = context.install_root.join(&operation.path);
        let backup = backup_root.join(&operation.path);
        if operation.state == JournalOperationState::Installed && current.exists() {
            remove_managed_entry(&current)?;
        }
        if backup.exists() {
            if operation.is_directory {
                rename_with_retry(&backup, &current)?;
            } else {
                move_file_replace(&backup, &current)?;
            }
        }
    }
    verify_file_tree(
        &context.install_root,
        &context.managed_paths,
        &context.source,
    )?;
    Ok(())
}

#[cfg(windows)]
fn remove_managed_entry(path: &Path) -> Result<(), FileUpdateCommandError> {
    let metadata = fs::symlink_metadata(path)?;
    if metadata.file_type().is_symlink() || is_reparse_point(&metadata) {
        return Err(FileUpdateCommandError::from(format!(
            "refusing to remove managed reparse point: {}",
            path.display()
        )));
    }
    if metadata.is_dir() {
        retry_file_operation(|| fs::remove_dir_all(path))?;
    } else if metadata.is_file() {
        retry_file_operation(|| fs::remove_file(path))?;
    } else {
        return Err(FileUpdateCommandError::from(format!(
            "unsupported managed entry type: {}",
            path.display()
        )));
    }
    Ok(())
}

#[cfg(windows)]
fn move_file_replace(source: &Path, destination: &Path) -> std::io::Result<()> {
    let source = wide_null(source.as_os_str())?;
    let destination = wide_null(destination.as_os_str())?;
    retry_file_operation(|| {
        let result = unsafe {
            MoveFileExW(
                source.as_ptr(),
                destination.as_ptr(),
                MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH,
            )
        };
        if result == 0 {
            Err(std::io::Error::last_os_error())
        } else {
            Ok(())
        }
    })
}

#[cfg(windows)]
fn rename_with_retry(source: &Path, destination: &Path) -> std::io::Result<()> {
    retry_file_operation(|| fs::rename(source, destination))
}

#[cfg(windows)]
fn retry_file_operation<T>(
    mut operation: impl FnMut() -> std::io::Result<T>,
) -> std::io::Result<T> {
    let deadline = std::time::Instant::now() + Duration::from_secs(FILE_OPERATION_RETRY_SECS);
    loop {
        match operation() {
            Ok(value) => return Ok(value),
            Err(error)
                if is_retryable_file_error(&error) && std::time::Instant::now() < deadline =>
            {
                thread::sleep(Duration::from_millis(200));
            }
            Err(error) => return Err(error),
        }
    }
}

#[cfg(windows)]
fn is_retryable_file_error(error: &std::io::Error) -> bool {
    matches!(error.raw_os_error(), Some(5 | 32 | 33))
}

#[cfg(windows)]
fn copy_file_backup(source: &Path, destination: &Path) -> std::io::Result<()> {
    let temporary = destination.with_extension(format!("backup-part-{}", std::process::id()));
    if temporary.exists() {
        fs::remove_file(&temporary)?;
    }
    retry_file_operation(|| fs::copy(source, &temporary))?;
    fs::OpenOptions::new()
        .write(true)
        .open(&temporary)?
        .sync_all()?;
    if let Err(error) = move_file_replace(&temporary, destination) {
        let _ = fs::remove_file(&temporary);
        return Err(error);
    }
    Ok(())
}

#[cfg(windows)]
fn wait_for_process_exit(pid: u32, timeout: Duration) -> Result<(), FileUpdateCommandError> {
    let process = unsafe { OpenProcess(SYNCHRONIZE | PROCESS_QUERY_LIMITED_INFORMATION, 0, pid) };
    if process.is_null() {
        return Ok(());
    }
    let timeout_ms = timeout.as_millis().min(u32::MAX as u128) as u32;
    let result = unsafe { WaitForSingleObject(process, timeout_ms) };
    unsafe {
        CloseHandle(process);
    }
    if result == WAIT_OBJECT_0 {
        Ok(())
    } else if result == WAIT_TIMEOUT {
        Err(FileUpdateCommandError::from(format!(
            "application process {pid} did not exit within {} seconds",
            timeout.as_secs()
        )))
    } else {
        Err(FileUpdateCommandError::from(format!(
            "waiting for application process {pid} failed with code {result}"
        )))
    }
}

#[cfg(windows)]
fn shell_execute_elevated(
    executable: &Path,
    parameters: &str,
) -> Result<HANDLE, FileUpdateCommandError> {
    let verb = wide_null(OsStr::new("runas"))?;
    let executable = wide_null(executable.as_os_str())?;
    let parameters = wide_null(OsStr::new(parameters))?;
    let mut execute_info = SHELLEXECUTEINFOW {
        cbSize: std::mem::size_of::<SHELLEXECUTEINFOW>() as u32,
        fMask: SEE_MASK_NOCLOSEPROCESS | SEE_MASK_NOASYNC,
        lpVerb: verb.as_ptr(),
        lpFile: executable.as_ptr(),
        lpParameters: parameters.as_ptr(),
        nShow: SW_SHOWNORMAL,
        ..Default::default()
    };
    if unsafe { ShellExecuteExW(&mut execute_info) } == 0 {
        let error = std::io::Error::last_os_error();
        if error.raw_os_error() == Some(ERROR_CANCELLED as i32) {
            return Err(FileUpdateCommandError::from(
                "administrator permission was declined",
            ));
        }
        if error.raw_os_error() == Some(ERROR_ELEVATION_REQUIRED as i32) {
            return Err(FileUpdateCommandError::from(
                "administrator permission is required",
            ));
        }
        return Err(FileUpdateCommandError::from(format!(
            "failed to start elevated file update worker: {error}"
        )));
    }
    if execute_info.hProcess.is_null() || unsafe { GetProcessId(execute_info.hProcess) } == 0 {
        if !execute_info.hProcess.is_null() {
            unsafe {
                CloseHandle(execute_info.hProcess);
            }
        }
        return Err(FileUpdateCommandError::from(
            "elevated file update worker started without a process handle",
        ));
    }
    Ok(execute_info.hProcess)
}

#[cfg(windows)]
fn launch_installed_application(
    config: &FileUpdateHelperConfig,
    install_root: &Path,
) -> Result<Child, FileUpdateCommandError> {
    let executable = install_root.join(config.main_executable);
    let mut command = Command::new(&executable);
    command
        .current_dir(install_root)
        .creation_flags(CREATE_NO_WINDOW);
    command.spawn().map_err(|error| {
        FileUpdateCommandError::from(format!(
            "failed to restart installed application {}: {error}",
            executable.display()
        ))
    })
}

#[cfg(windows)]
fn request_rollback(transaction_root: &Path, reason: &str) -> Result<(), FileUpdateCommandError> {
    fs::write(
        transaction_root.join(ROLLBACK_REQUEST_FILE),
        reason.trim().as_bytes(),
    )?;
    Ok(())
}

#[cfg(windows)]
fn write_launched_pid(transaction_root: &Path, pid: u32) -> Result<(), FileUpdateCommandError> {
    fs::write(
        transaction_root.join(LAUNCHED_PID_FILE),
        pid.to_string().as_bytes(),
    )?;
    Ok(())
}

#[cfg(windows)]
fn read_launched_pid(transaction_root: &Path) -> Option<u32> {
    fs::read_to_string(transaction_root.join(LAUNCHED_PID_FILE))
        .ok()?
        .trim()
        .parse()
        .ok()
}

#[cfg(windows)]
fn process_is_running(pid: u32) -> bool {
    let process = unsafe { OpenProcess(SYNCHRONIZE | PROCESS_QUERY_LIMITED_INFORMATION, 0, pid) };
    if process.is_null() {
        return false;
    }
    let wait = unsafe { WaitForSingleObject(process, 0) };
    unsafe {
        CloseHandle(process);
    }
    wait == WAIT_TIMEOUT
}

#[cfg(windows)]
fn cleanup_transaction_payload(context: &ValidatedContext) -> Result<(), FileUpdateCommandError> {
    if context.staging_path.exists() {
        ensure_plain_directory(&context.staging_path)?;
        fs::remove_dir_all(&context.staging_path)?;
    }
    let patch_path = context.transaction_root.join("patch.hdiff");
    if patch_path.is_file() {
        fs::remove_file(patch_path)?;
    }
    let rollback_path = context.transaction_root.join(ROLLBACK_REQUEST_FILE);
    if rollback_path.is_file() {
        fs::remove_file(rollback_path)?;
    }

    let cache_root = context
        .transaction_root
        .parent()
        .and_then(Path::parent)
        .ok_or_else(|| FileUpdateCommandError::from("transaction cache root is missing"))?;
    let pointer_path = cache_root.join("prepared.json");
    if pointer_path.is_file() {
        let pointer = serde_json::from_slice::<PreparedPointer>(&fs::read(&pointer_path)?);
        if pointer.ok().is_some_and(|pointer| {
            pointer.transaction_path.canonicalize().ok() == Some(context.transaction_path.clone())
        }) {
            fs::remove_file(pointer_path)?;
        }
    }
    Ok(())
}

fn ensure_plain_directory(path: &Path) -> Result<(), FileUpdateCommandError> {
    let metadata = fs::symlink_metadata(path)?;
    if !metadata.is_dir() || metadata.file_type().is_symlink() || is_reparse_point(&metadata) {
        return Err(FileUpdateCommandError::from(format!(
            "directory is missing or is a reparse point: {}",
            path.display()
        )));
    }
    Ok(())
}

#[cfg(windows)]
fn is_reparse_point(metadata: &fs::Metadata) -> bool {
    use std::os::windows::fs::MetadataExt;
    metadata.file_attributes() & 0x0000_0400 != 0
}

#[cfg(not(windows))]
fn is_reparse_point(_metadata: &fs::Metadata) -> bool {
    false
}

fn write_helper_result(
    path: &Path,
    state: HelperResultState,
    message: Option<String>,
) -> Result<(), FileUpdateCommandError> {
    write_json_file_atomic(
        path,
        &HelperResult {
            state,
            updated_at_ms: now_millis(),
            message,
        },
    )
    .map_err(FileUpdateCommandError::from)
}

fn read_helper_result(path: &Path) -> Result<HelperResult, FileUpdateCommandError> {
    Ok(serde_json::from_slice(&fs::read(path)?)?)
}

fn core_error_to_io(error: CoreError) -> std::io::Error {
    std::io::Error::other(error.to_string())
}

#[cfg(windows)]
fn wide_null(value: &OsStr) -> std::io::Result<Vec<u16>> {
    let mut wide = Vec::new();
    for unit in value.encode_wide() {
        if unit == 0 {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                "value contains an embedded null character",
            ));
        }
        wide.push(unit);
    }
    wide.push(0);
    Ok(wide)
}

#[cfg(windows)]
fn windows_command_line(args: &[String]) -> String {
    args.iter()
        .map(|argument| quote_windows_argument(argument))
        .collect::<Vec<_>>()
        .join(" ")
}

#[cfg(windows)]
fn quote_windows_argument(argument: &str) -> String {
    if !argument.is_empty()
        && !argument
            .chars()
            .any(|character| matches!(character, ' ' | '\t' | '"'))
    {
        return argument.to_owned();
    }
    let mut quoted = String::with_capacity(argument.len() + 2);
    quoted.push('"');
    let mut backslashes = 0usize;
    for character in argument.chars() {
        match character {
            '\\' => backslashes += 1,
            '"' => {
                quoted.extend(std::iter::repeat('\\').take(backslashes * 2 + 1));
                quoted.push('"');
                backslashes = 0;
            }
            _ => {
                quoted.extend(std::iter::repeat('\\').take(backslashes));
                quoted.push(character);
                backslashes = 0;
            }
        }
    }
    quoted.extend(std::iter::repeat('\\').take(backslashes * 2));
    quoted.push('"');
    quoted
}

fn now_millis() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|duration| duration.as_millis() as u64)
        .unwrap_or_default()
}

#[cfg(test)]
mod tests {
    #[cfg(windows)]
    use std::fs;

    #[cfg(windows)]
    use hdiff_update_core::{
        build_file_tree_manifest, verify_file_tree, DirectoryTransactionState,
        DirectoryUpdateTransaction,
    };
    #[cfg(windows)]
    use tempfile::tempdir;

    #[cfg(windows)]
    use super::{
        commit_update, quote_windows_argument, recover_interrupted_commit, windows_command_line,
        CommitJournal, FileUpdateHelperConfig, JournalOperation, JournalOperationState,
        ValidatedContext,
    };

    #[cfg(windows)]
    #[test]
    fn quotes_helper_arguments_for_shell_execute() {
        assert_eq!(quote_windows_argument("plain"), "plain");
        assert_eq!(
            windows_command_line(&[
                "--hdiff-update-elevated".to_string(),
                "C:\\Program Data\\transaction.json".to_string(),
            ]),
            "--hdiff-update-elevated \"C:\\Program Data\\transaction.json\""
        );
    }

    #[cfg(windows)]
    #[test]
    fn commit_replaces_managed_payload_and_keeps_unmanaged_files() {
        let dir = tempdir().unwrap();
        let install = dir.path().join("install");
        let transaction_root = dir.path().join("transaction");
        let staging = transaction_root.join("staged");
        fs::create_dir_all(install.join("resources")).unwrap();
        fs::create_dir_all(install.join("plugins")).unwrap();
        fs::create_dir_all(staging.join("resources")).unwrap();
        fs::create_dir_all(staging.join("plugins")).unwrap();
        fs::write(install.join("app.exe"), b"old-app").unwrap();
        fs::write(install.join("resources/data.bin"), b"old-resource").unwrap();
        fs::write(install.join("plugins/plugin.js"), b"same").unwrap();
        fs::write(install.join("uninstall.exe"), b"unmanaged").unwrap();
        fs::write(staging.join("app.exe"), b"new-app").unwrap();
        fs::write(staging.join("resources/data.bin"), b"new-resource").unwrap();
        fs::write(staging.join("plugins/plugin.js"), b"same").unwrap();

        let managed = vec![
            "app.exe".to_string(),
            "plugins".to_string(),
            "resources".to_string(),
        ];
        let source = build_file_tree_manifest(&install, &managed).unwrap();
        let target = build_file_tree_manifest(&staging, &managed).unwrap();
        let transaction = DirectoryUpdateTransaction {
            schema_version: 1,
            transaction_id: "test-transaction".to_string(),
            application_id: "test.app".to_string(),
            platform: "windows-x86_64".to_string(),
            current_version: "0.1.0".to_string(),
            target_version: "0.2.0".to_string(),
            install_root: install.clone(),
            managed_paths: managed.clone(),
            source_tree_sha256: source.tree_sha256.clone(),
            target_tree_sha256: target.tree_sha256.clone(),
            patch_sha256: "a".repeat(64),
            patch_size: 1,
            full_size: 100,
            state: DirectoryTransactionState::Ready,
            created_at_ms: 1,
            updated_at_ms: 1,
            failure_reason: None,
        };
        let transaction_path = transaction_root.join("transaction.json");
        let mut context = ValidatedContext {
            transaction_path,
            transaction_root: transaction_root.clone(),
            transaction,
            source,
            target: target.clone(),
            staging_path: staging,
            result_path: transaction_root.join("result.json"),
            install_root: install.clone(),
            managed_paths: managed.clone(),
        };
        let config = FileUpdateHelperConfig {
            application_id: "test.app",
            public_keys: &["unused"],
            main_executable: "app.exe",
            managed_paths: &["app.exe", "plugins", "resources"],
            hpatchz_relative_path: "bin/hpatchz.exe",
        };

        let protected = commit_update(&config, &mut context).unwrap();
        verify_file_tree(&install, &managed, &target).unwrap();
        assert_eq!(
            fs::read(install.join("uninstall.exe")).unwrap(),
            b"unmanaged"
        );
        assert!(protected.join("backup/app.exe").is_file());
    }

    #[cfg(windows)]
    #[test]
    fn interrupted_pending_file_backup_never_replaces_the_intact_source() {
        let dir = tempdir().unwrap();
        let install = dir.path().join("install");
        let transaction_root = dir.path().join("transaction");
        let staging = transaction_root.join("staged");
        fs::create_dir_all(&install).unwrap();
        fs::create_dir_all(&staging).unwrap();
        fs::write(install.join("app.exe"), b"old-app-complete").unwrap();
        fs::write(staging.join("app.exe"), b"new-app").unwrap();

        let managed = vec!["app.exe".to_string()];
        let source = build_file_tree_manifest(&install, &managed).unwrap();
        let target = build_file_tree_manifest(&staging, &managed).unwrap();
        let transaction = DirectoryUpdateTransaction {
            schema_version: 1,
            transaction_id: "test-interrupted-backup".to_string(),
            application_id: "test.app".to_string(),
            platform: "windows-x86_64".to_string(),
            current_version: "0.1.0".to_string(),
            target_version: "0.2.0".to_string(),
            install_root: install.clone(),
            managed_paths: managed.clone(),
            source_tree_sha256: source.tree_sha256.clone(),
            target_tree_sha256: target.tree_sha256.clone(),
            patch_sha256: "a".repeat(64),
            patch_size: 1,
            full_size: 100,
            state: DirectoryTransactionState::Committing,
            created_at_ms: 1,
            updated_at_ms: 1,
            failure_reason: None,
        };
        let context = ValidatedContext {
            transaction_path: transaction_root.join("transaction.json"),
            transaction_root: transaction_root.clone(),
            transaction,
            source,
            target,
            staging_path: staging,
            result_path: transaction_root.join("result.json"),
            install_root: install.clone(),
            managed_paths: managed,
        };
        let protected = install
            .join(".hdiff-update")
            .join("test-interrupted-backup");
        fs::create_dir_all(protected.join("backup")).unwrap();
        fs::write(protected.join("backup/app.exe"), b"partial").unwrap();
        let journal = CommitJournal {
            transaction_id: "test-interrupted-backup".to_string(),
            state: DirectoryTransactionState::Committing,
            operations: vec![JournalOperation {
                path: "app.exe".to_string(),
                is_directory: false,
                state: JournalOperationState::Pending,
            }],
            updated_at_ms: 1,
        };
        fs::write(
            protected.join("journal.json"),
            serde_json::to_vec_pretty(&journal).unwrap(),
        )
        .unwrap();

        recover_interrupted_commit(&context).unwrap();

        assert_eq!(
            fs::read(install.join("app.exe")).unwrap(),
            b"old-app-complete"
        );
        assert!(!protected.exists());
    }
}