postvak-core 0.3.0

use std::ffi::OsString;
use std::fs;
use std::io;
use std::os::unix::fs::{DirBuilderExt, PermissionsExt};
use std::path::{Path, PathBuf};
use std::time::SystemTime;

#[derive(Debug, Clone)]
pub struct Paths {
    /// The root given to `under` (`POSTVAK_HOME`); None for the platform directories.
    pub home: Option<PathBuf>,
    pub config_dir: PathBuf,
    pub state_dir: PathBuf,
    pub cache_dir: PathBuf,
}

impl Paths {
    pub fn discover() -> anyhow::Result<Paths> {
        let dirs = directories::ProjectDirs::from("", "", "postvak")
            .ok_or_else(|| anyhow::anyhow!("no home directory found"))?;
        let state_dir = dirs
            .state_dir()
            .map(Path::to_path_buf)
            .unwrap_or_else(|| dirs.data_local_dir().to_path_buf());
        Ok(Paths {
            home: None,
            config_dir: dirs.config_dir().to_path_buf(),
            state_dir,
            cache_dir: dirs.cache_dir().to_path_buf(),
        })
    }

    pub fn under(root: &Path) -> Paths {
        Paths {
            home: Some(root.to_path_buf()),
            config_dir: root.join("config"),
            state_dir: root.join("state"),
            cache_dir: root.join("cache"),
        }
    }

    pub fn config_file(&self) -> PathBuf {
        self.config_dir.join("config.toml")
    }

    pub fn rules_file(&self) -> PathBuf {
        self.config_dir.join("rules.toml")
    }

    pub fn daemon_socket(&self) -> PathBuf {
        self.state_dir.join("daemon.sock")
    }

    pub fn daemon_lock(&self) -> PathBuf {
        self.state_dir.join("daemon.lock")
    }

    pub fn daemon_log(&self) -> PathBuf {
        self.state_dir.join("daemon.log")
    }

    pub fn update_check(&self) -> PathBuf {
        self.cache_dir.join("update-check.json")
    }

    pub fn account_dir(&self, name: &str) -> PathBuf {
        self.state_dir.join("accounts").join(name)
    }

    pub fn mail_db(&self, name: &str) -> PathBuf {
        self.account_dir(name).join("mail.db")
    }

    pub fn trash_dir(&self, name: &str) -> PathBuf {
        self.account_dir(name).join("trash")
    }

    pub fn ensure_account(&self, name: &str) -> io::Result<()> {
        create_private_dir(&self.config_dir)?;
        create_private_dir(&self.cache_dir)?;
        create_private_dir(&self.account_dir(name))?;
        create_private_dir(&self.trash_dir(name))
    }
}

pub fn create_private_dir(dir: &Path) -> io::Result<()> {
    fs::DirBuilder::new()
        .recursive(true)
        .mode(0o700)
        .create(dir)?;
    fs::set_permissions(dir, fs::Permissions::from_mode(0o700))
}

pub fn write_atomic(path: &Path, bytes: &[u8]) -> io::Result<()> {
    write_atomic_in(path, bytes, true)
}

/// For a folder another app owns: an existing parent keeps its mode, a missing one is created private.
pub fn write_atomic_keeping_dir_mode(path: &Path, bytes: &[u8]) -> io::Result<()> {
    write_atomic_in(path, bytes, false)
}

fn write_atomic_in(path: &Path, bytes: &[u8], private_dir: bool) -> io::Result<()> {
    // A symlink (say into a dotfiles repo) is written through, not replaced; a dangling one fails in canonicalize.
    if fs::symlink_metadata(path).is_ok_and(|m| m.file_type().is_symlink()) {
        return write_file_atomic(&fs::canonicalize(path)?, bytes);
    }
    let dir = path
        .parent()
        .ok_or_else(|| io::Error::other("path has no parent"))?;
    if private_dir || !dir.exists() {
        create_private_dir(dir)?;
    }
    write_file_atomic(path, bytes)
}

/// This binary's path for anything that outlives the process (service file, MCP host config, an auto-started
/// daemon). On Linux `current_exe` resolves symlinks, so a Homebrew install reports its versioned keg, which
/// `brew upgrade` later deletes, and an AppImage reports its temporary mount, which goes away when it exits.
pub fn stable_exe() -> io::Result<PathBuf> {
    let exe = std::env::current_exe()?;
    let appimage = std::env::var_os("APPIMAGE").map(PathBuf::from);
    let appdir = std::env::var_os("APPDIR").map(PathBuf::from);
    if let Some(image) = appimage_path(&exe, appimage.as_deref(), appdir.as_deref()) {
        return Ok(image);
    }
    Ok(match homebrew_opt_path(&exe) {
        Some(opt) if same_file(&opt, &exe) => opt,
        _ => exe,
    })
}

/// The app id when this process runs in a Flatpak sandbox, which sets `FLATPAK_ID`. The binary and config folders
/// there are the sandbox's own, so something the host runs later must go through `flatpak run`.
pub fn flatpak_id() -> Option<String> {
    std::env::var("FLATPAK_ID").ok().filter(|id| !id.is_empty())
}

/// The AppImage file this binary runs from: the runtime sets `APPIMAGE` and `APPDIR` (its mount), and only a binary
/// inside that mount is the AppImage; children of an AppImage inherit both variables.
fn appimage_path(exe: &Path, appimage: Option<&Path>, appdir: Option<&Path>) -> Option<PathBuf> {
    let (image, mount) = (appimage?, appdir?);
    exe.starts_with(mount).then(|| image.to_path_buf())
}

/// `<prefix>/Cellar/<formula>/<version>/<rest>` becomes `<prefix>/opt/<formula>/<rest>`, Homebrew's link to the
/// current keg.
fn homebrew_opt_path(exe: &Path) -> Option<PathBuf> {
    let parts: Vec<_> = exe.components().collect();
    let cellar = parts.iter().rposition(|c| c.as_os_str() == "Cellar")?;
    let (prefix, rest) = parts.split_at(cellar);
    let [_cellar, formula, _version, rest @ ..] = rest else {
        return None;
    };
    if rest.is_empty() {
        return None;
    }
    let mut opt: PathBuf = prefix.iter().collect();
    opt.push("opt");
    opt.push(formula);
    opt.extend(rest);
    Some(opt)
}

fn same_file(a: &Path, b: &Path) -> bool {
    match (fs::canonicalize(a), fs::canonicalize(b)) {
        (Ok(a), Ok(b)) => a == b,
        _ => false,
    }
}

/// Whether this process is the macOS app opened from Finder, the Dock or `open`: the binary sits in a bundle's
/// `Contents/MacOS`, got no arguments (very old macOS passes a `-psn_…` process serial number, which counts as none)
/// and stdin is not a terminal. Then the app opens the mail window instead of printing help; a terminal run of the
/// same binary (the cask links it as the `postvak` command) still prints help. `args` excludes argv\[0\].
pub fn launched_as_app(exe: &Path, args: &[OsString], stdin_is_terminal: bool) -> bool {
    let in_bundle = exe
        .parent()
        .is_some_and(|dir| dir.ends_with("Contents/MacOS"))
        && exe.ancestors().nth(3).is_some_and(|bundle| {
            bundle
                .extension()
                .is_some_and(|ext| ext.eq_ignore_ascii_case("app"))
        });
    let no_args = args
        .iter()
        .all(|a| a.to_str().is_some_and(|a| a.starts_with("-psn_")));
    in_bundle && no_args && !stdin_is_terminal
}

fn write_file_atomic(path: &Path, bytes: &[u8]) -> io::Result<()> {
    use std::io::Write;

    let dir = path
        .parent()
        .ok_or_else(|| io::Error::other("path has no parent"))?;
    let tmp = dir.join(format!(
        ".{}.{}.tmp",
        path.file_name().and_then(|n| n.to_str()).unwrap_or("file"),
        std::process::id()
    ));
    let mut file = fs::File::create(&tmp)?;
    file.set_permissions(fs::Permissions::from_mode(0o600))?;
    file.write_all(bytes)?;
    file.sync_all()?;
    fs::rename(&tmp, path)?;
    // The rename lives in the directory entry; without this a crash can bring back the old file or none.
    fs::File::open(dir)?.sync_all()?;
    Ok(())
}

/// A file's modification time, to notice edits by polling.
pub struct FileWatch {
    pub path: PathBuf,
    modified: Option<SystemTime>,
}

impl FileWatch {
    pub fn new(path: PathBuf) -> FileWatch {
        FileWatch {
            modified: modified_time(&path),
            path,
        }
    }

    /// Whether the modification time changed since the last call.
    pub fn changed(&mut self) -> bool {
        let modified = modified_time(&self.path);
        if modified == self.modified {
            return false;
        }
        self.modified = modified;
        true
    }
}

fn modified_time(path: &Path) -> Option<SystemTime> {
    fs::metadata(path).and_then(|meta| meta.modified()).ok()
}

#[cfg(test)]
mod tests {
    use super::*;

    fn args(list: &[&str]) -> Vec<OsString> {
        list.iter().map(OsString::from).collect()
    }

    const APP_EXE: &str = "/Applications/Postvak.app/Contents/MacOS/postvak";

    #[test]
    fn finder_launch_of_the_bundle_opens_the_app() {
        assert!(launched_as_app(Path::new(APP_EXE), &[], false));
        assert!(launched_as_app(
            Path::new("/Users/me/Downloads/Postvak.APP/Contents/MacOS/postvak"),
            &[],
            false
        ));
    }

    #[test]
    fn an_old_macos_process_serial_number_counts_as_no_arguments() {
        assert!(launched_as_app(
            Path::new(APP_EXE),
            &args(&["-psn_0_12345"]),
            false
        ));
    }

    #[test]
    fn any_real_argument_runs_the_cli() {
        assert!(!launched_as_app(
            Path::new(APP_EXE),
            &args(&["list"]),
            false
        ));
        assert!(!launched_as_app(
            Path::new(APP_EXE),
            &args(&["-psn_0_1", "--help"]),
            false
        ));
    }

    #[test]
    fn a_terminal_run_of_the_bundled_binary_prints_help() {
        assert!(!launched_as_app(Path::new(APP_EXE), &[], true));
    }

    #[test]
    fn a_binary_outside_a_bundle_runs_the_cli() {
        for exe in [
            "/opt/homebrew/bin/postvak",
            "/usr/local/Cellar/postvak/0.1.0/bin/postvak",
            "/tmp/Contents/MacOS/postvak",
            "/x/Postvak.app/Contents/Resources/postvak",
            "postvak",
        ] {
            assert!(!launched_as_app(Path::new(exe), &[], false), "{exe}");
        }
    }

    #[test]
    fn under_root_lays_out_three_dirs() {
        let root = tempfile::tempdir().unwrap();
        let p = Paths::under(root.path());
        assert_eq!(p.config_file(), root.path().join("config/config.toml"));
        assert_eq!(p.rules_file(), root.path().join("config/rules.toml"));
        assert_eq!(
            p.mail_db("work"),
            root.path().join("state/accounts/work/mail.db")
        );
        assert_eq!(
            p.trash_dir("work"),
            root.path().join("state/accounts/work/trash")
        );
        assert_eq!(
            p.update_check(),
            root.path().join("cache/update-check.json")
        );
    }

    #[test]
    fn ensure_account_creates_dirs() {
        let root = tempfile::tempdir().unwrap();
        let p = Paths::under(root.path());
        p.ensure_account("work").unwrap();
        assert!(p.trash_dir("work").is_dir());
        assert!(p.config_dir.is_dir());
    }

    #[test]
    fn write_atomic_replaces_content_and_leaves_no_tmp() {
        let root = tempfile::tempdir().unwrap();
        let file = root.path().join("a.txt");
        write_atomic(&file, b"one").unwrap();
        write_atomic(&file, b"two").unwrap();
        assert_eq!(fs::read(&file).unwrap(), b"two");
        let leftovers: Vec<_> = fs::read_dir(root.path()).unwrap().collect();
        assert_eq!(leftovers.len(), 1);
    }

    #[test]
    fn write_atomic_creates_private_dir_and_file() {
        let root = tempfile::tempdir().unwrap();
        let path = root.path().join("config").join("config.toml");
        write_atomic(&path, b"x").unwrap();
        let mode = |p: &Path| fs::metadata(p).unwrap().permissions().mode() & 0o777;
        assert_eq!(mode(path.parent().unwrap()), 0o700);
        assert_eq!(mode(&path), 0o600);
    }

    #[test]
    fn ensure_account_dirs_are_private() {
        let root = tempfile::tempdir().unwrap();
        let p = Paths::under(root.path());
        p.ensure_account("work").unwrap();

        let check_mode = |dir: &Path| {
            let mode = fs::metadata(dir).unwrap().permissions().mode();
            assert_eq!(mode & 0o777, 0o700, "directory {:?} is not 0700", dir);
        };

        check_mode(&p.state_dir);
        check_mode(&p.state_dir.join("accounts"));
        check_mode(&p.account_dir("work"));
        check_mode(&p.trash_dir("work"));
    }

    #[test]
    fn ensure_account_is_idempotent_across_accounts() {
        let root = tempfile::tempdir().unwrap();
        let p = Paths::under(root.path());
        p.ensure_account("work").unwrap();
        p.ensure_account("work").unwrap();
        p.ensure_account("personal").unwrap();
        assert!(p.trash_dir("work").is_dir());
        assert!(p.trash_dir("personal").is_dir());
    }

    #[test]
    fn an_appimage_reports_its_own_file_not_its_mount() {
        let exe = Path::new("/tmp/.mount_PostbXy12/usr/bin/postvak");
        let image = Path::new("/home/me/Apps/Postvak-x86_64.AppImage");
        let mount = Path::new("/tmp/.mount_PostbXy12");
        assert_eq!(
            appimage_path(exe, Some(image), Some(mount)),
            Some(image.to_path_buf())
        );
        // A postvak started from a shell that inherited another AppImage's environment is not that AppImage.
        let other = Path::new("/home/me/.cargo/bin/postvak");
        assert_eq!(appimage_path(other, Some(image), Some(mount)), None);
        assert_eq!(appimage_path(exe, None, Some(mount)), None);
        assert_eq!(appimage_path(exe, Some(image), None), None);
    }

    #[test]
    fn homebrew_keg_path_maps_to_opt() {
        let opt = |p: &str| homebrew_opt_path(Path::new(p));
        assert_eq!(
            opt("/home/linuxbrew/.linuxbrew/Cellar/postvak/0.3.0/bin/postvak"),
            Some(PathBuf::from(
                "/home/linuxbrew/.linuxbrew/opt/postvak/bin/postvak"
            ))
        );
        assert_eq!(
            opt("/opt/homebrew/Cellar/postvak/0.3.0_1/bin/postvak"),
            Some(PathBuf::from("/opt/homebrew/opt/postvak/bin/postvak"))
        );
        assert_eq!(opt("/home/me/.cargo/bin/postvak"), None);
        assert_eq!(opt("/opt/homebrew/Cellar/postvak/0.3.0"), None);
        assert_eq!(opt("/opt/homebrew/Cellar/postvak"), None);
    }

    #[test]
    fn opt_link_is_used_only_when_it_is_the_same_binary() {
        let root = tempfile::tempdir().unwrap();
        let keg = |v: &str| root.path().join(format!("Cellar/postvak/{v}/bin/postvak"));
        for v in ["0.3.0", "0.4.0"] {
            fs::create_dir_all(keg(v).parent().unwrap()).unwrap();
            fs::write(keg(v), v).unwrap();
        }
        fs::create_dir_all(root.path().join("opt")).unwrap();
        std::os::unix::fs::symlink(
            root.path().join("Cellar/postvak/0.4.0"),
            root.path().join("opt/postvak"),
        )
        .unwrap();
        let opt = homebrew_opt_path(&keg("0.4.0")).unwrap();
        assert_eq!(opt, root.path().join("opt/postvak/bin/postvak"));
        assert!(same_file(&opt, &keg("0.4.0")));
        // An older keg still running after an upgrade keeps its own path rather than pointing at another version.
        assert!(!same_file(
            &homebrew_opt_path(&keg("0.3.0")).unwrap(),
            &keg("0.3.0")
        ));
    }

    #[test]
    fn write_atomic_writes_through_a_symlink() {
        let root = tempfile::tempdir().unwrap();
        let real = root.path().join("dotfiles/rules.toml");
        fs::create_dir_all(real.parent().unwrap()).unwrap();
        fs::write(&real, "old").unwrap();
        let link = root.path().join("config/rules.toml");
        fs::create_dir_all(link.parent().unwrap()).unwrap();
        std::os::unix::fs::symlink(&real, &link).unwrap();
        write_atomic(&link, b"new").unwrap();
        assert!(
            fs::symlink_metadata(&link)
                .unwrap()
                .file_type()
                .is_symlink()
        );
        assert_eq!(fs::read_to_string(&real).unwrap(), "new");
    }

    #[test]
    fn write_atomic_refuses_a_dangling_symlink() {
        let root = tempfile::tempdir().unwrap();
        let link = root.path().join("rules.toml");
        std::os::unix::fs::symlink(root.path().join("missing/rules.toml"), &link).unwrap();
        assert!(write_atomic(&link, b"new").is_err());
        assert!(
            fs::symlink_metadata(&link)
                .unwrap()
                .file_type()
                .is_symlink()
        );
    }
}