//! Linux AppImage desktop integration.
//!
//! A bare AppImage is a portable file with no menu entry — deleting it uninstalls
//! the app. These commands let ThoughtSync install itself into the application menu
//! (a `.desktop` launcher + icon) and keep a stable copy in `~/Applications`, so it
//! behaves like an installed app, and remove that again. No external helper
//! (AppImageLauncher / Gear Lever) is required.
//!
//! Everything keys off the `$APPIMAGE` env var (set only when running from an
//! AppImage), so on a non-AppImage run — the dev build, a `.deb` install, or a
//! future Windows/macOS build — the status simply reports `is_appimage: false` and
//! the actions are never offered by the frontend.

use std::fs;
use std::path::{Path, PathBuf};

use serde::Serialize;

// The 1024px brand icon, embedded so integration never depends on the AppImage's
// internal layout. Written to the user icon dir on integrate.
const APP_ICON: &[u8] = include_bytes!("../app-icon.png");

const DESKTOP_ENTRY_NAME: &str = "thoughtsync.desktop";
const ICON_FILE_NAME: &str = "thoughtsync.png";
const INSTALLED_APPIMAGE_NAME: &str = "ThoughtSync.AppImage";

#[derive(Serialize)]
pub struct IntegrationStatus {
    /// Running from an AppImage (`$APPIMAGE` is set).
    is_appimage: bool,
    /// Our `.desktop` launcher is present in the user applications dir.
    is_integrated: bool,
    /// Path of the currently-running AppImage, if any.
    appimage_path: Option<String>,
}

fn home() -> Option<PathBuf> {
    std::env::var_os("HOME").map(PathBuf::from)
}

fn appimage_path() -> Option<PathBuf> {
    std::env::var_os("APPIMAGE").map(PathBuf::from)
}

fn desktop_entry_path() -> Option<PathBuf> {
    home().map(|h| h.join(".local/share/applications").join(DESKTOP_ENTRY_NAME))
}

fn icon_path() -> Option<PathBuf> {
    home().map(|h| h.join(".local/share/icons").join(ICON_FILE_NAME))
}

#[tauri::command]
pub fn integration_status() -> IntegrationStatus {
    let ai = appimage_path();
    let is_integrated = desktop_entry_path().map(|p| p.exists()).unwrap_or(false);
    IntegrationStatus {
        is_appimage: ai.is_some(),
        is_integrated,
        appimage_path: ai.map(|p| p.to_string_lossy().into_owned()),
    }
}

#[tauri::command]
pub fn integrate_desktop() -> Result<IntegrationStatus, String> {
    let current = appimage_path().ok_or("Not running as an AppImage.")?;
    let home = home().ok_or("Cannot resolve the home directory.")?;

    // Give the AppImage a stable home so it can't be lost from Downloads. Copy (not
    // move): the running file is memory-mapped, so a copy is always safe.
    let apps_dir = home.join("Applications");
    fs::create_dir_all(&apps_dir).map_err(|e| format!("create ~/Applications: {e}"))?;
    let installed = apps_dir.join(INSTALLED_APPIMAGE_NAME);
    if current != installed {
        fs::copy(&current, &installed).map_err(|e| format!("copy AppImage: {e}"))?;
        set_executable(&installed)?;
    }

    // Icon (embedded) -> user icon dir.
    let icon = icon_path().ok_or("Cannot resolve the icon path.")?;
    if let Some(parent) = icon.parent() {
        fs::create_dir_all(parent).map_err(|e| format!("create icon dir: {e}"))?;
    }
    fs::write(&icon, APP_ICON).map_err(|e| format!("write icon: {e}"))?;

    // .desktop launcher -> user applications dir. Icon/Exec are absolute paths, so no
    // icon-theme lookup is needed.
    //
    // StartupWMClass is the exception: it must be the BINARY name, because GTK
    // derives the window's WM_CLASS from the executable and the desktop matches the
    // two to group the taskbar icon. Not the product name, and not this AppImage's
    // filename — AppRun execs `usr/bin/thoughtsync` inside it (issue 2075).
    let entry = desktop_entry_path().ok_or("Cannot resolve the applications dir.")?;
    if let Some(parent) = entry.parent() {
        fs::create_dir_all(parent).map_err(|e| format!("create applications dir: {e}"))?;
    }
    let contents = format!(
        "[Desktop Entry]\n\
         Type=Application\n\
         Name=ThoughtSync\n\
         Comment=Capture a fleeting thought in a second\n\
         Exec={exec} %U\n\
         Icon={icon}\n\
         Terminal=false\n\
         Categories=Utility;Office;\n\
         StartupWMClass=thoughtsync\n",
        exec = installed.to_string_lossy(),
        icon = icon.to_string_lossy(),
    );
    fs::write(&entry, contents).map_err(|e| format!("write .desktop: {e}"))?;

    refresh_desktop_database(&home);
    Ok(integration_status())
}

#[tauri::command]
pub fn unintegrate_desktop() -> Result<IntegrationStatus, String> {
    let home = home().ok_or("Cannot resolve the home directory.")?;
    if let Some(entry) = desktop_entry_path() {
        remove_if_exists(&entry)?;
    }
    if let Some(icon) = icon_path() {
        remove_if_exists(&icon)?;
    }
    // Intentionally keep ~/Applications/ThoughtSync.AppImage: it may be the running
    // binary, and removing it would delete the app the user is using. Un-integrate
    // only removes the menu entry.
    refresh_desktop_database(&home);
    Ok(integration_status())
}

fn remove_if_exists(p: &Path) -> Result<(), String> {
    if p.exists() {
        fs::remove_file(p).map_err(|e| format!("remove {}: {e}", p.display()))?;
    }
    Ok(())
}

#[cfg(unix)]
fn set_executable(p: &Path) -> Result<(), String> {
    use std::os::unix::fs::PermissionsExt;
    let mut perm = fs::metadata(p)
        .map_err(|e| format!("stat: {e}"))?
        .permissions();
    perm.set_mode(0o755);
    fs::set_permissions(p, perm).map_err(|e| format!("chmod: {e}"))
}

#[cfg(not(unix))]
fn set_executable(_p: &Path) -> Result<(), String> {
    Ok(())
}

// Best-effort: refresh the desktop database so the entry appears promptly. The entry
// still works on next login without it, so failures are ignored.
fn refresh_desktop_database(home: &Path) {
    let apps = home.join(".local/share/applications");
    let _ = std::process::Command::new("update-desktop-database")
        .arg(&apps)
        .output();
}