changes

src-tauri/src/gdrive.rs

@@ -0,0 +1,806 @@
+use base64::Engine;
+use base64::engine::general_purpose::URL_SAFE_NO_PAD;
+use rand::RngCore;
+use serde::de::DeserializeOwned;
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use std::collections::HashMap;
+use std::fs;
+use std::io::{Read, Write};
+use std::net::{TcpListener, TcpStream};
+use std::path::PathBuf;
+use std::sync::{LazyLock, Mutex};
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+use tauri::{Emitter, Manager};
+
+const FOLDER_NAME: &str = "margin";
+const DICTIONARY_NAME: &str = "custom-dictionary.txt";
+const SCOPES: &str = "openid email https://www.googleapis.com/auth/drive.file";
+const AUTH_TIMEOUT_SECS: u64 = 120;
+
+const CREDENTIALS_JSON: &str =
+    include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/../google-credentials.json"));
+
+static HTTP: LazyLock<reqwest::Client> = LazyLock::new(reqwest::Client::new);
+
+#[derive(Deserialize)]
+struct CredentialsFile {
+    installed: Credentials,
+}
+
+#[derive(Deserialize)]
+struct Credentials {
+    client_id: String,
+    client_secret: String,
+    auth_uri: String,
+    token_uri: String,
+}
+
+fn load_credentials() -> Result<Credentials, String> {
+    let runtime_path = concat!(env!("CARGO_MANIFEST_DIR"), "/../google-credentials.json");
+    let raw = fs::read_to_string(runtime_path).unwrap_or_else(|_| CREDENTIALS_JSON.to_string());
+    let parsed: CredentialsFile = serde_json::from_str(&raw)
+        .map_err(|e| format!("invalid google-credentials.json: {e}"))?;
+    let creds = parsed.installed;
+    if creds.client_id.starts_with("YOUR_CLIENT_ID") || creds.client_secret.starts_with("YOUR_CLIENT_SECRET") {
+        return Err("Google Drive is not set up yet. Add a real OAuth desktop client to google-credentials.json.".to_string());
+    }
+    Ok(creds)
+}
+
+#[derive(Default)]
+pub struct GDriveState(pub Mutex<Session>);
+
+#[derive(Default)]
+pub struct Session {
+    refresh_token: Option<String>,
+    access_token: Option<String>,
+    access_expiry: u64,
+    email: Option<String>,
+    folder_id: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Default)]
+struct BackupState {
+    #[serde(default)]
+    refresh_token: Option<String>,
+    email: Option<String>,
+    folder_id: Option<String>,
+    last_backup: Option<u64>,
+    #[serde(default)]
+    files: HashMap<String, FileRecord>,
+}
+
+#[derive(Serialize, Deserialize, Clone)]
+struct FileRecord {
+    hash: String,
+    drive_id: String,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Status {
+    connected: bool,
+    email: Option<String>,
+    last_backup: Option<u64>,
+    pending: bool,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RestoreResult {
+    restored: usize,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BackupOutcome {
+    uploaded: usize,
+    #[serde(flatten)]
+    status: Status,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RemoteBackup {
+    name: String,
+}
+
+#[derive(Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+struct AuthEvent {
+    ok: bool,
+    error: Option<String>,
+}
+
+fn now() -> u64 {
+    SystemTime::now().duration_since(UNIX_EPOCH).unwrap_or_default().as_secs()
+}
+
+fn dictionary_path(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    Ok(crate::library::app_data_dir(app)?.join(DICTIONARY_NAME))
+}
+
+fn state_path(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    Ok(crate::library::app_data_dir(app)?.join("backup.json"))
+}
+
+fn load_state(app: &tauri::AppHandle) -> BackupState {
+    let path = match state_path(app) {
+        Ok(p) => p,
+        Err(_) => return BackupState::default(),
+    };
+    match fs::read_to_string(&path) {
+        Ok(contents) => serde_json::from_str(&contents).unwrap_or_default(),
+        Err(_) => BackupState::default(),
+    }
+}
+
+fn save_state(app: &tauri::AppHandle, state: &BackupState) -> Result<(), String> {
+    let path = state_path(app)?;
+    let contents = serde_json::to_string_pretty(state).map_err(|e| e.to_string())?;
+    crate::project::atomic_write(&path, contents.as_bytes(), false)
+}
+
+fn random_b64(bytes: usize) -> String {
+    let mut buf = vec![0u8; bytes];
+    rand::thread_rng().fill_bytes(&mut buf);
+    URL_SAFE_NO_PAD.encode(buf)
+}
+
+fn pkce_challenge(verifier: &str) -> String {
+    let mut hasher = Sha256::new();
+    hasher.update(verifier.as_bytes());
+    URL_SAFE_NO_PAD.encode(hasher.finalize())
+}
+
+fn hash_bytes(bytes: &[u8]) -> String {
+    let mut hasher = Sha256::new();
+    hasher.update(bytes);
+    format!("{:x}", hasher.finalize())
+}
+
+fn urlencode(s: &str) -> String {
+    url::form_urlencoded::byte_serialize(s.as_bytes()).collect()
+}
+
+fn drive_escape(s: &str) -> String {
+    s.replace('\\', "\\\\").replace('\'', "\\'")
+}
+
+fn safe_book_name(name: &str) -> bool {
+    match name.strip_suffix(".margin") {
+        Some(stem) => !stem.is_empty() && stem.chars().all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_'),
+        None => false,
+    }
+}
+
+fn write_http_message(stream: &mut TcpStream, message: &str) {
+    let body = format!(
+        "<!doctype html><html><head><meta charset=\"utf-8\"><title>margin</title></head>\
+         <body style=\"font-family:system-ui,sans-serif;text-align:center;padding-top:80px;color:#222\">\
+         <h2>{message}</h2></body></html>"
+    );
+    let response = format!(
+        "HTTP/1.1 200 OK\r\nContent-Type: text/html; charset=utf-8\r\nContent-Length: {}\r\nConnection: close\r\n\r\n{}",
+        body.len(),
+        body
+    );
+    let _ = stream.write_all(response.as_bytes());
+    let _ = stream.flush();
+}
+
+fn await_code(listener: TcpListener, expected_state: &str, deadline: Instant) -> Result<String, String> {
+    listener.set_nonblocking(true).map_err(|e| e.to_string())?;
+    loop {
+        if Instant::now() > deadline {
+            return Err("Timed out waiting for Google authorization.".to_string());
+        }
+        match listener.accept() {
+            Ok((mut stream, _)) => {
+                stream.set_nonblocking(false).ok();
+                stream.set_read_timeout(Some(Duration::from_secs(5))).ok();
+                let mut buf = [0u8; 8192];
+                let n = stream.read(&mut buf).unwrap_or(0);
+                let request = String::from_utf8_lossy(&buf[..n]);
+                let path = request.lines().next().and_then(|line| line.split_whitespace().nth(1)).unwrap_or("");
+                if path == "/favicon.ico" {
+                    write_http_message(&mut stream, "margin");
+                    continue;
+                }
+                let full = format!("http://127.0.0.1{path}");
+                let parsed = match url::Url::parse(&full) {
+                    Ok(p) => p,
+                    Err(_) => {
+                        write_http_message(&mut stream, "Waiting for Google…");
+                        continue;
+                    }
+                };
+                let mut code = None;
+                let mut state = None;
+                let mut error = None;
+                for (key, value) in parsed.query_pairs() {
+                    match key.as_ref() {
+                        "code" => code = Some(value.into_owned()),
+                        "state" => state = Some(value.into_owned()),
+                        "error" => error = Some(value.into_owned()),
+                        _ => {}
+                    }
+                }
+                if let Some(error) = error {
+                    write_http_message(&mut stream, "Authorization was cancelled. You can close this tab.");
+                    return Err(format!("Google authorization failed: {error}"));
+                }
+                match (code, state) {
+                    (Some(code), Some(state)) if state == expected_state => {
+                        write_http_message(&mut stream, "Connected to margin. You can close this tab.");
+                        return Ok(code);
+                    }
+                    (Some(_), _) => {
+                        write_http_message(&mut stream, "Could not verify the request. You can close this tab.");
+                        return Err("State mismatch during Google authorization.".to_string());
+                    }
+                    _ => {
+                        write_http_message(&mut stream, "Waiting for Google…");
+                    }
+                }
+            }
+            Err(ref e) if e.kind() == std::io::ErrorKind::WouldBlock => {
+                std::thread::sleep(Duration::from_millis(150));
+            }
+            Err(e) => return Err(e.to_string()),
+        }
+    }
+}
+
+#[derive(Deserialize)]
+struct TokenResponse {
+    access_token: String,
+    #[serde(default)]
+    refresh_token: Option<String>,
+    #[serde(default)]
+    expires_in: u64,
+}
+
+#[derive(Deserialize)]
+struct UserInfo {
+    #[serde(default)]
+    email: Option<String>,
+}
+
+#[derive(Deserialize)]
+struct DriveFile {
+    id: String,
+    #[serde(default)]
+    name: String,
+}
+
+#[derive(Deserialize)]
+struct FileList {
+    #[serde(default)]
+    files: Vec<DriveFile>,
+    #[serde(default, rename = "nextPageToken")]
+    next_page_token: Option<String>,
+}
+
+async fn read_json<T: DeserializeOwned>(resp: reqwest::Response, context: &str) -> Result<T, String> {
+    let status = resp.status();
+    let text = resp.text().await.map_err(|e| e.to_string())?;
+    if !status.is_success() {
+        return Err(format!("{context} failed ({status}): {text}"));
+    }
+    serde_json::from_str(&text).map_err(|e| format!("{context}: could not parse response: {e}"))
+}
+
+async fn exchange_code(creds: &Credentials, code: &str, redirect: &str, verifier: &str) -> Result<TokenResponse, String> {
+    let resp = HTTP
+        .post(&creds.token_uri)
+        .form(&[
+            ("client_id", creds.client_id.as_str()),
+            ("client_secret", creds.client_secret.as_str()),
+            ("code", code),
+            ("code_verifier", verifier),
+            ("grant_type", "authorization_code"),
+            ("redirect_uri", redirect),
+        ])
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    read_json(resp, "Google token exchange").await
+}
+
+async fn refresh_access_token(creds: &Credentials, refresh_token: &str) -> Result<TokenResponse, String> {
+    let resp = HTTP
+        .post(&creds.token_uri)
+        .form(&[
+            ("client_id", creds.client_id.as_str()),
+            ("client_secret", creds.client_secret.as_str()),
+            ("refresh_token", refresh_token),
+            ("grant_type", "refresh_token"),
+        ])
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    read_json(resp, "Google token refresh").await
+}
+
+async fn fetch_email(access_token: &str) -> Result<String, String> {
+    let resp = HTTP
+        .get("https://www.googleapis.com/oauth2/v2/userinfo")
+        .bearer_auth(access_token)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    let info: UserInfo = read_json(resp, "Google account lookup").await?;
+    Ok(info.email.unwrap_or_default())
+}
+
+async fn ensure_folder(access_token: &str) -> Result<String, String> {
+    let query = format!(
+        "name = '{}' and mimeType = 'application/vnd.google-apps.folder' and trashed = false",
+        drive_escape(FOLDER_NAME)
+    );
+    let resp = HTTP
+        .get("https://www.googleapis.com/drive/v3/files")
+        .bearer_auth(access_token)
+        .query(&[
+            ("q", query.as_str()),
+            ("fields", "files(id,name)"),
+            ("spaces", "drive"),
+            ("pageSize", "1"),
+        ])
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    let list: FileList = read_json(resp, "Drive folder lookup").await?;
+    if let Some(folder) = list.files.into_iter().next() {
+        return Ok(folder.id);
+    }
+    let body = serde_json::json!({
+        "name": FOLDER_NAME,
+        "mimeType": "application/vnd.google-apps.folder",
+    });
+    let resp = HTTP
+        .post("https://www.googleapis.com/drive/v3/files")
+        .bearer_auth(access_token)
+        .query(&[("fields", "id")])
+        .json(&body)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    let created: DriveFile = read_json(resp, "Drive folder creation").await?;
+    Ok(created.id)
+}
+
+async fn find_file(access_token: &str, folder_id: &str, name: &str) -> Result<Option<DriveFile>, String> {
+    let query = format!(
+        "'{}' in parents and name = '{}' and trashed = false",
+        drive_escape(folder_id),
+        drive_escape(name)
+    );
+    let resp = HTTP
+        .get("https://www.googleapis.com/drive/v3/files")
+        .bearer_auth(access_token)
+        .query(&[
+            ("q", query.as_str()),
+            ("fields", "files(id,name)"),
+            ("spaces", "drive"),
+            ("pageSize", "1"),
+        ])
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    let list: FileList = read_json(resp, "Drive file lookup").await?;
+    Ok(list.files.into_iter().next())
+}
+
+async fn list_in_folder(access_token: &str, folder_id: &str) -> Result<Vec<DriveFile>, String> {
+    let query = format!("'{}' in parents and trashed = false", drive_escape(folder_id));
+    let mut files = Vec::new();
+    let mut page_token: Option<String> = None;
+    loop {
+        let mut request = HTTP
+            .get("https://www.googleapis.com/drive/v3/files")
+            .bearer_auth(access_token)
+            .query(&[
+                ("q", query.as_str()),
+                ("fields", "nextPageToken,files(id,name)"),
+                ("spaces", "drive"),
+                ("pageSize", "100"),
+            ]);
+        if let Some(token) = &page_token {
+            request = request.query(&[("pageToken", token.as_str())]);
+        }
+        let resp = request.send().await.map_err(|e| e.to_string())?;
+        let FileList { files: page, next_page_token } = read_json(resp, "Drive file list").await?;
+        files.extend(page);
+        match next_page_token {
+            Some(token) => page_token = Some(token),
+            None => break,
+        }
+    }
+    Ok(files)
+}
+
+async fn upload_file(
+    access_token: &str,
+    folder_id: &str,
+    name: &str,
+    bytes: &[u8],
+    existing_id: Option<String>,
+) -> Result<DriveFile, String> {
+    let boundary = "margin7f3e2a1b9c8d";
+    let metadata = match &existing_id {
+        Some(_) => serde_json::json!({ "name": name }),
+        None => serde_json::json!({ "name": name, "parents": [folder_id] }),
+    };
+    let mut body: Vec<u8> = Vec::new();
+    body.extend_from_slice(format!("--{boundary}\r\nContent-Type: application/json; charset=UTF-8\r\n\r\n").as_bytes());
+    body.extend_from_slice(serde_json::to_string(&metadata).unwrap_or_default().as_bytes());
+    body.extend_from_slice(format!("\r\n--{boundary}\r\nContent-Type: application/octet-stream\r\n\r\n").as_bytes());
+    body.extend_from_slice(bytes);
+    body.extend_from_slice(format!("\r\n--{boundary}--\r\n").as_bytes());
+
+    let request = match &existing_id {
+        Some(id) => HTTP.patch(format!("https://www.googleapis.com/upload/drive/v3/files/{id}")),
+        None => HTTP.post("https://www.googleapis.com/upload/drive/v3/files"),
+    };
+    let resp = request
+        .bearer_auth(access_token)
+        .query(&[("uploadType", "multipart"), ("fields", "id")])
+        .header(reqwest::header::CONTENT_TYPE, format!("multipart/related; boundary={boundary}"))
+        .body(body)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    read_json(resp, &format!("Drive upload of {name}")).await
+}
+
+async fn download_file(access_token: &str, id: &str) -> Result<Vec<u8>, String> {
+    let resp = HTTP
+        .get(format!("https://www.googleapis.com/drive/v3/files/{id}"))
+        .bearer_auth(access_token)
+        .query(&[("alt", "media")])
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    let status = resp.status();
+    if !status.is_success() {
+        let text = resp.text().await.unwrap_or_default();
+        return Err(format!("Drive download failed ({status}): {text}"));
+    }
+    Ok(resp.bytes().await.map_err(|e| e.to_string())?.to_vec())
+}
+
+async fn valid_access_token(app: &tauri::AppHandle, state: &GDriveState) -> Result<String, String> {
+    let (access, expiry, refresh) = {
+        let session = state.0.lock().unwrap();
+        (session.access_token.clone(), session.access_expiry, session.refresh_token.clone())
+    };
+    if let Some(token) = access {
+        if now() < expiry {
+            return Ok(token);
+        }
+    }
+    let refresh = refresh.ok_or("Not connected to Google Drive.")?;
+    let creds = load_credentials()?;
+    let tokens = refresh_access_token(&creds, &refresh).await?;
+    let access_token = tokens.access_token.clone();
+    {
+        let mut session = state.0.lock().unwrap();
+        session.access_token = Some(tokens.access_token);
+        session.access_expiry = now() + tokens.expires_in.saturating_sub(60);
+        if let Some(rotated) = &tokens.refresh_token {
+            session.refresh_token = Some(rotated.clone());
+        }
+    }
+    if let Some(rotated) = &tokens.refresh_token {
+        let mut stored = load_state(app);
+        stored.refresh_token = Some(rotated.clone());
+        let _ = save_state(app, &stored);
+    }
+    Ok(access_token)
+}
+
+async fn ensure_folder_id(app: &tauri::AppHandle, state: &GDriveState, access_token: &str) -> Result<String, String> {
+    {
+        let session = state.0.lock().unwrap();
+        if let Some(folder) = &session.folder_id {
+            return Ok(folder.clone());
+        }
+    }
+    let folder_id = ensure_folder(access_token).await?;
+    {
+        let mut session = state.0.lock().unwrap();
+        session.folder_id = Some(folder_id.clone());
+    }
+    let mut stored = load_state(app);
+    stored.folder_id = Some(folder_id.clone());
+    save_state(app, &stored)?;
+    Ok(folder_id)
+}
+
+fn collect_local_files(app: &tauri::AppHandle) -> Result<Vec<(String, Vec<u8>)>, String> {
+    let mut files = Vec::new();
+    let library = crate::library::library_dir(app)?;
+    for entry in fs::read_dir(&library).map_err(|e| e.to_string())? {
+        let path = match entry {
+            Ok(entry) => entry.path(),
+            Err(_) => continue,
+        };
+        if path.extension().and_then(|e| e.to_str()) != Some("margin") {
+            continue;
+        }
+        let name = match path.file_name().and_then(|n| n.to_str()) {
+            Some(name) if safe_book_name(name) => name.to_string(),
+            _ => continue,
+        };
+        let bytes = fs::read(&path).map_err(|e| e.to_string())?;
+        files.push((name, bytes));
+    }
+    let dictionary = dictionary_path(app)?;
+    if dictionary.exists() {
+        let bytes = fs::read(&dictionary).map_err(|e| e.to_string())?;
+        files.push((DICTIONARY_NAME.to_string(), bytes));
+    }
+    Ok(files)
+}
+
+fn file_pending(path: &std::path::Path, name: &str, stored: &BackupState, last_backup: u64) -> bool {
+    let record = match stored.files.get(name) {
+        Some(record) => record,
+        None => return true,
+    };
+    let touched = fs::metadata(path)
+        .and_then(|meta| meta.modified())
+        .ok()
+        .and_then(|time| time.duration_since(UNIX_EPOCH).ok())
+        .map(|since| since.as_secs() > last_backup)
+        .unwrap_or(true);
+    if !touched {
+        return false;
+    }
+    match fs::read(path) {
+        Ok(bytes) => record.hash != hash_bytes(&bytes),
+        Err(_) => false,
+    }
+}
+
+fn compute_pending(app: &tauri::AppHandle, stored: &BackupState) -> bool {
+    let last_backup = stored.last_backup.unwrap_or(0);
+    let library = match crate::library::library_dir(app) {
+        Ok(dir) => dir,
+        Err(_) => return false,
+    };
+    if let Ok(entries) = fs::read_dir(&library) {
+        for entry in entries.flatten() {
+            let path = entry.path();
+            if path.extension().and_then(|e| e.to_str()) != Some("margin") {
+                continue;
+            }
+            if let Some(name) = path.file_name().and_then(|n| n.to_str()) {
+                if safe_book_name(name) && file_pending(&path, name, stored, last_backup) {
+                    return true;
+                }
+            }
+        }
+    }
+    match dictionary_path(app) {
+        Ok(dict) if dict.exists() => file_pending(&dict, DICTIONARY_NAME, stored, last_backup),
+        _ => false,
+    }
+}
+
+fn status_inner(app: &tauri::AppHandle, state: &GDriveState) -> Status {
+    let (connected, email) = {
+        let session = state.0.lock().unwrap();
+        (session.refresh_token.is_some(), session.email.clone())
+    };
+    let stored = load_state(app);
+    let pending = connected && compute_pending(app, &stored);
+    Status {
+        connected,
+        email: email.or(stored.email),
+        last_backup: stored.last_backup,
+        pending,
+    }
+}
+
+pub fn init_session(app: &tauri::AppHandle) {
+    let state = app.state::<GDriveState>();
+    let stored = load_state(app);
+    let mut session = state.0.lock().unwrap();
+    session.refresh_token = stored.refresh_token;
+    session.email = stored.email;
+    session.folder_id = stored.folder_id;
+}
+
+async fn complete_auth(
+    app: &tauri::AppHandle,
+    listener: TcpListener,
+    csrf: String,
+    verifier: String,
+    redirect: String,
+    creds: Credentials,
+) -> Result<(), String> {
+    let code = tauri::async_runtime::spawn_blocking(move || {
+        let deadline = Instant::now() + Duration::from_secs(AUTH_TIMEOUT_SECS);
+        await_code(listener, &csrf, deadline)
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    let tokens = exchange_code(&creds, &code, &redirect, &verifier).await?;
+    let email = fetch_email(&tokens.access_token).await?;
+    let folder_id = ensure_folder(&tokens.access_token).await?;
+
+    {
+        let state = app.state::<GDriveState>();
+        let mut session = state.0.lock().unwrap();
+        if let Some(refresh) = &tokens.refresh_token {
+            session.refresh_token = Some(refresh.clone());
+        }
+        session.access_token = Some(tokens.access_token.clone());
+        session.access_expiry = now() + tokens.expires_in.saturating_sub(60);
+        session.email = Some(email.clone());
+        session.folder_id = Some(folder_id.clone());
+    }
+
+    let mut stored = load_state(app);
+    if let Some(refresh) = &tokens.refresh_token {
+        stored.refresh_token = Some(refresh.clone());
+    }
+    stored.email = Some(email);
+    stored.folder_id = Some(folder_id);
+    save_state(app, &stored)?;
+    Ok(())
+}
+
+#[tauri::command]
+pub async fn gdrive_connect(app: tauri::AppHandle) -> Result<String, String> {
+    let creds = load_credentials()?;
+    let verifier = random_b64(64);
+    let challenge = pkce_challenge(&verifier);
+    let csrf = random_b64(24);
+
+    let listener = TcpListener::bind("127.0.0.1:0").map_err(|e| e.to_string())?;
+    let port = listener.local_addr().map_err(|e| e.to_string())?.port();
+    let redirect = format!("http://127.0.0.1:{port}");
+
+    let auth_url = format!(
+        "{}?client_id={}&redirect_uri={}&response_type=code&scope={}&code_challenge={}&code_challenge_method=S256&state={}&access_type=offline&prompt=consent",
+        creds.auth_uri,
+        urlencode(&creds.client_id),
+        urlencode(&redirect),
+        urlencode(SCOPES),
+        challenge,
+        urlencode(&csrf),
+    );
+
+    use tauri_plugin_opener::OpenerExt;
+    let _ = app.opener().open_url(auth_url.clone(), None::<&str>);
+
+    let app_bg = app.clone();
+    tauri::async_runtime::spawn(async move {
+        let event = match complete_auth(&app_bg, listener, csrf, verifier, redirect, creds).await {
+            Ok(()) => AuthEvent { ok: true, error: None },
+            Err(error) => AuthEvent { ok: false, error: Some(error) },
+        };
+        let _ = app_bg.emit("gdrive-auth", event);
+    });
+
+    Ok(auth_url)
+}
+
+#[tauri::command]
+pub async fn gdrive_disconnect(app: tauri::AppHandle, state: tauri::State<'_, GDriveState>) -> Result<Status, String> {
+    let refresh = {
+        let session = state.0.lock().unwrap();
+        session.refresh_token.clone()
+    };
+    if let Some(refresh) = refresh {
+        let _ = HTTP
+            .post("https://oauth2.googleapis.com/revoke")
+            .form(&[("token", refresh.as_str())])
+            .send()
+            .await;
+    }
+    {
+        let mut session = state.0.lock().unwrap();
+        session.refresh_token = None;
+        session.access_token = None;
+        session.access_expiry = 0;
+        session.email = None;
+    }
+    let mut stored = load_state(&app);
+    stored.refresh_token = None;
+    stored.email = None;
+    save_state(&app, &stored)?;
+    Ok(status_inner(&app, &state))
+}
+
+#[tauri::command]
+pub async fn gdrive_status(app: tauri::AppHandle, state: tauri::State<'_, GDriveState>) -> Result<Status, String> {
+    Ok(status_inner(&app, &state))
+}
+
+#[tauri::command]
+pub async fn gdrive_backup(app: tauri::AppHandle, state: tauri::State<'_, GDriveState>) -> Result<BackupOutcome, String> {
+    let access_token = valid_access_token(&app, &state).await?;
+    let folder_id = ensure_folder_id(&app, &state, &access_token).await?;
+    let files = collect_local_files(&app)?;
+    let mut stored = load_state(&app);
+    let mut uploaded = 0;
+    for (name, bytes) in &files {
+        let hash = hash_bytes(bytes);
+        let existing = stored.files.get(name).cloned();
+        if let Some(record) = &existing {
+            if record.hash == hash {
+                continue;
+            }
+        }
+        let drive_id = match &existing {
+            Some(record) => Some(record.drive_id.clone()),
+            None => find_file(&access_token, &folder_id, name).await?.map(|file| file.id),
+        };
+        let result = upload_file(&access_token, &folder_id, name, bytes, drive_id).await?;
+        stored.files.insert(name.clone(), FileRecord { hash, drive_id: result.id });
+        uploaded += 1;
+    }
+    if uploaded > 0 {
+        stored.last_backup = Some(now());
+        save_state(&app, &stored)?;
+    }
+    Ok(BackupOutcome {
+        uploaded,
+        status: Status {
+            connected: true,
+            email: stored.email.clone(),
+            last_backup: stored.last_backup,
+            pending: false,
+        },
+    })
+}
+
+#[tauri::command]
+pub async fn gdrive_restore(app: tauri::AppHandle, state: tauri::State<'_, GDriveState>) -> Result<RestoreResult, String> {
+    let access_token = valid_access_token(&app, &state).await?;
+    let folder_id = ensure_folder_id(&app, &state, &access_token).await?;
+    let remote = list_in_folder(&access_token, &folder_id).await?;
+    let mut stored = load_state(&app);
+    let mut restored = 0;
+    for file in &remote {
+        let is_dictionary = file.name == DICTIONARY_NAME;
+        let is_book = safe_book_name(&file.name);
+        if !is_dictionary && !is_book {
+            continue;
+        }
+        let bytes = download_file(&access_token, &file.id).await?;
+        let destination = if is_dictionary {
+            dictionary_path(&app)?
+        } else {
+            crate::library::library_dir(&app)?.join(&file.name)
+        };
+        crate::project::atomic_write(&destination, &bytes, false)?;
+        stored.files.insert(
+            file.name.clone(),
+            FileRecord { hash: hash_bytes(&bytes), drive_id: file.id.clone() },
+        );
+        restored += 1;
+    }
+    stored.last_backup = Some(now());
+    save_state(&app, &stored)?;
+    Ok(RestoreResult { restored })
+}
+
+#[tauri::command]
+pub async fn gdrive_list_backups(app: tauri::AppHandle, state: tauri::State<'_, GDriveState>) -> Result<Vec<RemoteBackup>, String> {
+    let access_token = valid_access_token(&app, &state).await?;
+    let folder_id = ensure_folder_id(&app, &state, &access_token).await?;
+    let remote = list_in_folder(&access_token, &folder_id).await?;
+    Ok(remote
+        .into_iter()
+        .filter(|file| safe_book_name(&file.name))
+        .map(|file| RemoteBackup { name: file.name })
+        .collect())
+}

src-tauri/src/lib.rs

@@ -1,5 +1,6 @@
 mod epub;
 mod fonts;
+mod gdrive;
 mod library;
 mod pdf;
 mod project;
@@ -72,6 +73,11 @@ pub fn run() {
 
     builder
         .manage(proofing::new_state())
+        .manage(gdrive::GDriveState::default())
+        .setup(|app| {
+            gdrive::init_session(app.handle());
+            Ok(())
+        })
         .menu(|handle| build_menu(handle))
         .on_menu_event(|app, event| {
             if matches!(
@@ -94,7 +100,13 @@ pub fn run() {
             library::save_book,
             library::delete_book,
             proofing::proof_text,
-            proofing::remember_word
+            proofing::remember_word,
+            gdrive::gdrive_connect,
+            gdrive::gdrive_disconnect,
+            gdrive::gdrive_status,
+            gdrive::gdrive_backup,
+            gdrive::gdrive_restore,
+            gdrive::gdrive_list_backups
         ])
         .run(context)
         .expect("error while running margin");

src-tauri/src/library.rs

@@ -19,12 +19,14 @@ fn corrupt_summary(stem: &str) -> BookSummary {
     }
 }
 
-fn library_dir(app: &tauri::AppHandle) -> Result<PathBuf, String> {
-    let dir = app
-        .path()
-        .app_data_dir()
-        .map_err(|e| e.to_string())?
-        .join("library");
+pub(crate) fn app_data_dir(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    let dir = app.path().app_data_dir().map_err(|e| e.to_string())?;
+    fs::create_dir_all(&dir).map_err(|e| e.to_string())?;
+    Ok(dir)
+}
+
+pub(crate) fn library_dir(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    let dir = app_data_dir(app)?.join("library");
     fs::create_dir_all(&dir).map_err(|e| e.to_string())?;
     Ok(dir)
 }