//! Auto-insert-at-cursor.
//!
//! `copy_to_clipboard` puts the transcript on the user's clipboard. That is
//! fine when the user wants to choose where it lands. It is friction when
//! they were about to paste into the already-focused window — which is
//! almost always, for a dictation tool.
//!
//! This module adds the follow-on step: send the platform's Ctrl+V / Cmd+V
//! keystroke to the focused window so the transcript lands where the cursor
//! already is. Each platform uses a different primitive (wtype / xdotool /
//! ydotool / osascript / SendKeys), so we probe and fall back.
//!
//! NOTE: focus must already be on the target window when the keystroke
//! fires. The global hotkey flow preserves this naturally; clicking Kon's
//! window does not. The frontend surfaces this caveat next to the toggle.

use std::process::Command;
use std::time::Duration;

use arboard::Clipboard;
use serde::Serialize;
use tauri::Manager;

/// Compositor settle time after hiding the preview overlay before firing
/// the paste keystroke. Empirically ~80ms is enough on KWin + Mutter
/// Wayland for focus to return to the previously-focused app; shorter
/// risks the keystroke still landing on the (now-invisible) overlay.
const PREVIEW_HIDE_SETTLE_MS: u64 = 80;

#[derive(Debug, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct PasteOutcome {
    /// The backend that executed the paste, if any (`"wtype"`, `"xdotool"`,
    /// `"ydotool"`, `"osascript"`, `"sendkeys"`).
    pub backend: Option<String>,
    pub pasted: bool,
    pub copied: bool,
    /// Diagnostic message when either step failed. Present even on success
    /// if the paste fell back to copy-only so the frontend can toast it.
    pub message: Option<String>,
}

/// Copy `text` to the clipboard, then trigger a paste keystroke in the
/// focused window. Returns a structured result so the frontend can surface
/// partial success (clipboard set, paste failed).
///
/// Wayland compositor quirk: if Kon's always-on-top preview overlay is
/// visible when the keystroke fires, KWin / Mutter may resolve the keystroke
/// against the overlay (even with `focused: false` set at build time) and
/// the paste lands inside Kon instead of the previously-focused app. We hide
/// the preview window and give the compositor a beat to re-focus the real
/// target before dispatching. Matches OpenWhispr's PR #246 fix on GNOME.
#[tauri::command]
pub async fn paste_text(app: tauri::AppHandle, text: String) -> Result<PasteOutcome, String> {
    let mut outcome = PasteOutcome {
        backend: None,
        pasted: false,
        copied: false,
        message: None,
    };

    match Clipboard::new().and_then(|mut cb| cb.set_text(&text)) {
        Ok(()) => outcome.copied = true,
        Err(err) => {
            outcome.message = Some(format!("clipboard: {err}"));
            return Ok(outcome);
        }
    }

    hide_preview_overlay_for_paste(&app).await;

    match trigger_paste_keystroke() {
        Ok(backend) => {
            outcome.backend = Some(backend);
            outcome.pasted = true;
        }
        Err(err) => outcome.message = Some(err),
    }

    Ok(outcome)
}

/// Hide the transcription-preview window if it's currently visible, then
/// sleep a short beat so the compositor can recompute focus. No-ops when
/// the window isn't registered yet (user never enabled the overlay) or
/// isn't currently shown.
async fn hide_preview_overlay_for_paste(app: &tauri::AppHandle) {
    let Some(window) = app.get_webview_window("transcription-preview") else {
        return;
    };
    let visible = window.is_visible().unwrap_or(false);
    if !visible {
        return;
    }
    if window.hide().is_err() {
        return;
    }
    tokio::time::sleep(Duration::from_millis(PREVIEW_HIDE_SETTLE_MS)).await;
}

/// Report which paste backends the OS has available right now. Pure probe —
/// does not paste. Used by Settings to tell the user "install wtype" when
/// nothing is available on their session.
#[tauri::command]
pub fn detect_paste_backends() -> Vec<String> {
    let mut available = Vec::new();

    #[cfg(target_os = "linux")]
    {
        for tool in ["wtype", "xdotool", "ydotool"] {
            if which_on_path(tool) {
                available.push(tool.to_string());
            }
        }
    }
    #[cfg(target_os = "macos")]
    {
        available.push("osascript".to_string());
    }
    #[cfg(target_os = "windows")]
    {
        available.push("sendkeys".to_string());
    }

    available
}

fn trigger_paste_keystroke() -> Result<String, String> {
    #[cfg(target_os = "linux")]
    {
        linux_paste(
            std::env::var("XDG_SESSION_TYPE").ok().as_deref(),
            std::env::var_os("WAYLAND_DISPLAY").is_some(),
        )
    }
    #[cfg(target_os = "macos")]
    {
        macos_paste()
    }
    #[cfg(target_os = "windows")]
    {
        windows_paste()
    }
    #[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
    {
        Err("auto-paste not implemented on this platform".into())
    }
}

#[cfg(target_os = "linux")]
fn linux_paste(xdg_session_type: Option<&str>, wayland_display_set: bool) -> Result<String, String> {
    for tool in pick_linux_backend_order(xdg_session_type, wayland_display_set) {
        match run_linux_tool(tool) {
            Ok(()) => return Ok(tool.to_string()),
            Err(_) => continue,
        }
    }
    Err(
        "No paste backend available. Install wtype (Wayland) or xdotool (X11) to enable \
         auto-insert-at-cursor."
            .into(),
    )
}

#[cfg(target_os = "linux")]
fn pick_linux_backend_order(
    xdg_session_type: Option<&str>,
    wayland_display_set: bool,
) -> &'static [&'static str] {
    let is_wayland = xdg_session_type
        .map(|value| value.eq_ignore_ascii_case("wayland"))
        .unwrap_or(false)
        || wayland_display_set;
    if is_wayland {
        &["wtype", "ydotool", "xdotool"]
    } else {
        &["xdotool", "ydotool", "wtype"]
    }
}

#[cfg(target_os = "linux")]
fn run_linux_tool(tool: &str) -> Result<(), String> {
    let output = match tool {
        // wtype -M ctrl v -m ctrl  (press ctrl, tap v, release ctrl)
        "wtype" => Command::new("wtype")
            .args(["-M", "ctrl", "v", "-m", "ctrl"])
            .output(),
        "xdotool" => Command::new("xdotool").args(["key", "ctrl+v"]).output(),
        // ydotool linux input keycodes: 29=LEFTCTRL, 47=V. Format is
        // `code:state` pairs. Requires ydotoold running with access to
        // /dev/uinput.
        "ydotool" => Command::new("ydotool")
            .args(["key", "29:1", "47:1", "47:0", "29:0"])
            .output(),
        other => return Err(format!("unknown backend: {other}")),
    }
    .map_err(|e| format!("{tool} unavailable: {e}"))?;

    if output.status.success() {
        Ok(())
    } else {
        Err(format!(
            "{tool} exit {}: {}",
            output.status,
            String::from_utf8_lossy(&output.stderr).trim()
        ))
    }
}

#[cfg(target_os = "linux")]
fn which_on_path(tool: &str) -> bool {
    Command::new("sh")
        .args(["-c", &format!("command -v {tool}")])
        .output()
        .map(|output| output.status.success())
        .unwrap_or(false)
}

#[cfg(target_os = "macos")]
fn macos_paste() -> Result<String, String> {
    let output = Command::new("osascript")
        .args([
            "-e",
            "tell application \"System Events\" to keystroke \"v\" using command down",
        ])
        .output()
        .map_err(|e| format!("osascript: {e}"))?;
    if output.status.success() {
        Ok("osascript".into())
    } else {
        Err(format!(
            "osascript exit {}: {}",
            output.status,
            String::from_utf8_lossy(&output.stderr).trim()
        ))
    }
}

#[cfg(target_os = "windows")]
fn windows_paste() -> Result<String, String> {
    // SendKeys("^v") simulates Ctrl+V in the foreground window. Requires
    // no extra permissions on Windows. A native SendInput call would skip
    // the PowerShell spawn but pulls in the windows crate; cost not worth
    // the complexity until this hot path actually shows up.
    let output = Command::new("powershell")
        .args([
            "-NoProfile",
            "-Command",
            "(New-Object -ComObject WScript.Shell).SendKeys('^v')",
        ])
        .output()
        .map_err(|e| format!("powershell: {e}"))?;
    if output.status.success() {
        Ok("sendkeys".into())
    } else {
        Err(format!(
            "powershell exit {}: {}",
            output.status,
            String::from_utf8_lossy(&output.stderr).trim()
        ))
    }
}

#[cfg(all(test, target_os = "linux"))]
mod tests {
    use super::pick_linux_backend_order;

    #[test]
    fn wayland_session_prefers_wtype_then_ydotool() {
        assert_eq!(
            pick_linux_backend_order(Some("wayland"), true),
            &["wtype", "ydotool", "xdotool"]
        );
    }

    #[test]
    fn x11_session_prefers_xdotool() {
        assert_eq!(
            pick_linux_backend_order(Some("x11"), false),
            &["xdotool", "ydotool", "wtype"]
        );
    }

    #[test]
    fn wayland_display_env_var_alone_is_enough() {
        assert_eq!(
            pick_linux_backend_order(None, true),
            &["wtype", "ydotool", "xdotool"]
        );
    }

    #[test]
    fn uppercase_wayland_token_still_detects_wayland() {
        assert_eq!(
            pick_linux_backend_order(Some("WAYLAND"), false),
            &["wtype", "ydotool", "xdotool"]
        );
    }
}