feat: Generate commands or ask questions with `atuin ai` (#3199)

This PR refines the system created in #3178 to be suitable for a v1
release.

---

## Overview

`atuin-ai` is a separate binary that allows for generating commands and
asking questions from the command line.

It is fully opt-in.

## Usage

`atuin ai init` will output bindings for your shell. Currently, bash,
zsh, and fish are supported.

```bash
eval "$(atuin ai init)"
```

Once the hooks are installed, just press `?` on an empty prompt line to
call up the TUI.

`atuin ai` requires an account on [Atuin Hub](https://hub.atuin.sh/);
you will be prompted to log in on first use.

## Features

### Command generation

Prompt the LLM to create a command, and get one back, no fuss. Press
`enter` to run, or `tab` to insert.

```
┌Ask questions or generate a command:──────────────────────────┐
│                                                              │
│ > Get a list of running docker containers                    │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ docker ps                                                  │
│                                                              │
└────[Enter]: Run  [Tab]: Insert  [f]: Follow-up  [Esc]: Cancel┘
```

### Follow-up

You can follow-up with `f` to specify a refinement prompt to update the
command that will be inserted.

```
┌Ask questions or generate a command:──────────────────────────┐
│                                                              │
│ > Get a list of running docker containers                    │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ docker ps                                                  │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ > Actually I want to get all docker containers               │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ docker ps -a                                               │
│                                                              │
└────[Enter]: Run  [Tab]: Insert  [f]: Follow-up  [Esc]: Cancel┘
```

You can also follow-up with questions to get responses in natural
language.

```
┌Ask questions or generate a command:──────────────────────────┐
│                                                              │
│ > Get a list of running docker containers                    │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ docker ps                                                  │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ > Actually I want to get all docker containers               │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ docker ps -a                                               │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ > What other useful flags to `docker ps` should I know?      │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│   Here are some handy `docker ps` flags:                     │
│                                                              │
│   - `-q` — Only show container IDs (great for piping to      │
│   other commands)                                            │
│   - `-s` — Show container sizes                              │
│   - `-n 5` — Show the last 5 created containers              │
│   - `-l` — Show only the latest created container            │
│   - `--no-trunc` — Don't truncate output (shows full IDs and │
│   commands)                                                  │
│   - `-f` or `--filter` — Filter by condition, e.g.:          │
│     - `-f status=exited` — only exited containers            │
│     - `-f name=myapp` — filter by name                       │
│     - `-f ancestor=nginx` — filter by image                  │
│   - `--format` — Custom output using Go templates, e.g.:     │
│     `--format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"`   │
│                                                              │
│   A common combo is `docker ps -aq` to get all container     │
│   IDs, useful for bulk operations like `docker rm $(docker   │
│   ps -aq)`.                                                  │
│                                                              │
└────[Enter]: Run  [Tab]: Insert  [f]: Follow-up  [Esc]: Cancel┘
```

You can use `enter` or `tab` at any time to run or insert the last
suggested command, even if it was suggested in a previous turn.

### Conversational and search usage

If you prompt the LLM with a question that doesn't imply you want to
generate a command, it can respond in natural language, and use web
search if necessary to fetch the data it needs.

```
┌Ask questions or generate a command:──────────────────────────┐
│                                                              │
│ > What is the latest version of atuin?                       │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ ✓ Used 2 tools                                               │
│                                                              │
│   The latest version of Atuin is **v18.12.0**, available on  │
│   the [GitHub releases                                       │
│   page](https://github.com/atuinsh/atuin/releases).          │
│                                                              │
└─────────────────────────────────[f]: Follow-up  [Esc]: Cancel┘
```

### Dangerous or low-confidence command detection

The LLM scores its confidence in the command, as well as how dangerous
the command is. This information is shown if a threshold is exceeded,
and requires an extra confirmation step before running automatically
with `enter`.

The Atuin Hub server also monitors suggested commands for dangerous
patterns the LLM didn't catch, and appends its own assessment at the end
of the LLM's own assessment.

```
┌Ask questions or generate a command:──────────────────────────┐
│                                                              │
│ > Delete all files from $HOME                                │
│                                                              │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│ $ rm -rf $HOME/*                                             │
│                                                              │
│ ! ⚠️  This will PERMANENTLY delete ALL files and directories │
│   in your home directory, including documents, downloads,    │
│   configurations, SSH keys, and everything else. This is     │
│   irreversible and will likely break your system. Also note  │
│   this won't delete hidden (dot) files — if you want those   │
│   too, that's even more destructive.; [Server] Recursive     │
│   delete of critical directory                               │
│                                                              │
└────[Enter]: Run  [Tab]: Insert  [f]: Follow-up  [Esc]: Cancel┘
```

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 99 insertions, 0 deletions

diff --git a/crates/atuin-ai/src/tui/spinner.rs b/crates/atuin-ai/src/tui/spinner.rs
new file mode 100644
index 00000000..138e0269
--- /dev/null
+++ b/crates/atuin-ai/src/tui/spinner.rs
@@ -0,0 +1,99 @@
+//! Spinner styles and configuration for TUI animations
+//!
+//! To experiment with different spinners, change `ACTIVE_SPINNER` below.
+
+use std::time::Duration;
+
+/// Active spinner style - change this to experiment with different styles
+pub const ACTIVE_SPINNER: SpinnerStyle = SpinnerStyle::Dots;
+
+/// Spinner style definitions
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SpinnerStyle {
+    /// Classic ASCII line spinner: / - \ |
+    Line,
+    /// Braille dots pattern
+    Dots,
+    /// Growing/shrinking dots
+    Pulse,
+    /// Simple arrow rotation
+    Arrow,
+    /// Block building
+    Block,
+}
+
+impl SpinnerStyle {
+    /// Get the frames for this spinner style
+    pub const fn frames(&self) -> &'static [&'static str] {
+        match self {
+            SpinnerStyle::Line => &["/", "-", "\\", "|"],
+            SpinnerStyle::Dots => &["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"],
+            SpinnerStyle::Pulse => &["·", "•", "●", "•"],
+            SpinnerStyle::Arrow => &["←", "↖", "↑", "↗", "→", "↘", "↓", "↙"],
+            SpinnerStyle::Block => &[
+                "▏", "▎", "▍", "▌", "▋", "▊", "▉", "█", "▉", "▊", "▋", "▌", "▍", "▎", "▏",
+            ],
+        }
+    }
+
+    /// Get the recommended tick interval for this spinner style
+    /// Faster spinners need shorter intervals to look smooth
+    pub const fn tick_interval(&self) -> Duration {
+        match self {
+            SpinnerStyle::Line => Duration::from_millis(150),
+            SpinnerStyle::Dots => Duration::from_millis(80),
+            SpinnerStyle::Pulse => Duration::from_millis(200),
+            SpinnerStyle::Arrow => Duration::from_millis(100),
+            SpinnerStyle::Block => Duration::from_millis(80),
+        }
+    }
+
+    /// Get the frame at the given index (wraps around)
+    pub fn frame_at(&self, index: usize) -> &'static str {
+        let frames = self.frames();
+        frames[index % frames.len()]
+    }
+
+    /// Get the number of frames in this spinner
+    pub fn frame_count(&self) -> usize {
+        self.frames().len()
+    }
+}
+
+/// Get the active spinner's frame at the given index
+pub fn active_frame(index: usize) -> &'static str {
+    ACTIVE_SPINNER.frame_at(index)
+}
+
+/// Get the active spinner's tick interval
+pub fn active_tick_interval() -> Duration {
+    ACTIVE_SPINNER.tick_interval()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_frame_wrapping() {
+        let style = SpinnerStyle::Line;
+        assert_eq!(style.frame_at(0), "/");
+        assert_eq!(style.frame_at(4), "/"); // wraps
+        assert_eq!(style.frame_at(5), "-");
+    }
+
+    #[test]
+    fn test_all_styles_have_frames() {
+        let styles = [
+            SpinnerStyle::Line,
+            SpinnerStyle::Dots,
+            SpinnerStyle::Pulse,
+            SpinnerStyle::Arrow,
+            SpinnerStyle::Block,
+        ];
+        for style in styles {
+            assert!(!style.frames().is_empty());
+            assert!(style.tick_interval().as_millis() > 0);
+        }
+    }
+}