tui-textarea
============
[![crate][crates-io-badge]][crate]
[![docs][doc-badge]][doc]
[![CI][ci-badge]][ci]
[![coverage][codecov-badge]][codecov]

[tui-textarea][crate] is a simple yet powerful text editor widget like `<textarea>` in HTML for [ratatui][] and [tui-rs][].
Multi-line text editor can be easily put as part of your TUI application.

**Features:**

- Multi-line text editor widget with basic operations (insert/delete characters, auto scrolling, ...)
- Emacs-like shortcuts (`C-n`/`C-p`/`C-f`/`C-b`, `M-f`/`M-b`, `C-a`/`C-e`, `C-h`/`C-d`, `C-k`, `M-<`/`M->`, ...)
- Undo/Redo
- Line number
- Cursor line highlight
- Search with regular expressions
- Text selection
- Mouse scrolling
- Yank support. Paste text deleted with `C-k`, `C-j`, ...
- Backend agnostic. [crossterm][], [termion][], [termwiz][], and your own backend are all supported
- Multiple textarea widgets in the same screen
- Support both [ratatui][] (the fork by community) and [tui-rs][] (the original)

[Documentation][doc]

## Examples

Running `cargo run --example` in this repository can demonstrate usage of tui-textarea.

### [`minimal`](./examples/minimal.rs)

```sh
cargo run --example minimal
```

Minimal usage with [crossterm][] support.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/minimal.gif" width=539 height=172 alt="minimal example">

### [`editor`](./examples/editor.rs)

```sh
cargo run --example editor --features search file.txt
```

Simple text editor to edit multiple files.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/editor.gif" width=560 height=236 alt="editor example">

### [`single_line`](./examples/single_line.rs)

```sh
cargo run --example single_line
```

Single-line input form with float number validation.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/single_line.gif" width=539 height=92 alt="single line example">

### [`split`](./examples/split.rs)

```sh
cargo run --example split
```

Two split textareas in a screen and switch them. An example for multiple textarea instances.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/split.gif" width=539 height=124 alt="multiple textareas example">

### [`variable`](./examples/variable.rs)

```sh
cargo run --example variable
```

Simple textarea with variable height following the number of lines.

### [`vim`](./examples/vim.rs)

```sh
cargo run --example vim
```

Vim-like modal text editor. Vim emulation is implemented as a state machine.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/vim.gif" width=590 height=156 alt="Vim emulation example">

### [`popup_placeholder`](./examples/popup_placeholder.rs)

```sh
cargo run --example popup_placeholder
```

Popup textarea with a placeholder text.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/placepop.gif" width=539 height=220 alt="popup textarea with placeholder example">

### [`password`](./examples/password.rs)

```sh
cargo run --example password
```

Password input form with masking text with ●.

<img src="https://raw.githubusercontent.com/rhysd/ss/master/tui-textarea/password.gif" width=589 height=92 alt="password example">

### [`termion`](./examples/termion.rs)

```sh
cargo run --example termion --no-default-features --features=termion
```

Minimal usage with [termion][] support.

### [`termwiz`](./examples/termwiz.rs)

```sh
cargo run --example termwiz --no-default-features --features=termwiz
```

Minimal usage with [termwiz][] support.

### Examples for [tui-rs][] support

All above examples use [ratatui][], but some examples provide tui-rs version. Try `tuirs_` prefix. In these cases, you
need to specify features to use tui-rs and `--no-default-features` flag explicitly.

```sh
# tui-rs version of `minimal` example
cargo run --example tuirs_minimal --no-default-features --features=tuirs-crossterm

# tui-rs version of `editor` example
cargo run --example tuirs_editor --no-default-features --features=tuirs-crossterm,search file.txt

# tui-rs version of `termion` example
cargo run --example tuirs_termion --no-default-features --features=tuirs-termion
```

## Installation

Add `tui-textarea` crate to dependencies in your `Cargo.toml`. This enables crossterm backend support by default.

```toml
[dependencies]
ratatui = "*"
tui-textarea = "*"
```

If you need text search with regular expressions, enable `search` feature. It adds [regex crate][regex] crate as
dependency.

```toml
[dependencies]
ratatui = "*"
tui-textarea = { version = "*", features = ["search"] }
```

If you're using ratatui with [termion][] or [termwiz][], enable respective feature instead of `crossterm` feature.

```toml
[dependencies]

# For termion
ratatui = { version = "*", default-features = false, features = ["termion"] }
tui-textarea = { version = "*", default-features = false, features = ["termion"] }

# For termwiz
ratatui = { version = "*", default-features = false, features = ["termwiz"] }
tui-textarea = { version = "*", default-features = false, features = ["termwiz"] }
```

If you're using [tui-rs][] instead of [ratatui][], you need to enable features for using tui-rs crate and to disable
default features. The following table shows feature names corresponding to the dependencies.

|         | crossterm                        | termion         | termwiz   | Your own backend   |
|---------|----------------------------------|-----------------|-----------|--------------------|
| ratatui | `crossterm` (enabled by default) | `termion`       | `termwiz` | `no-backend`       |
| tui-rs  | `tuirs-crossterm`                | `tuirs-termion` | N/A       | `tuirs-no-backend` |

For example, when you want to use the combination of [tui-rs][] and [crossterm][],

```toml
[dependencies]
tui = "*"
tui-textarea = { version = "*", features = ["tuirs-crossterm"], default-features = false }
```

Note that [ratatui][] support and [tui-rs][] support are exclusive. When you use [tui-rs][] support, you must disable
[ratatui][] support by `default-features = false`.

In addition to above dependencies, you also need to install [crossterm][] or [termion][] or [termwiz][] to initialize
your application and to receive key inputs. Note that version of [crossterm][] crate is different between [ratatui][]
and [tui-rs][]. Please select the correct version.

## Minimal Usage

```rust,ignore
use tui_textarea::TextArea;
use crossterm::event::{Event, read};

let mut term = ratatui::Terminal::new(...);

// Create an empty `TextArea` instance which manages the editor state
let mut textarea = TextArea::default();

// Event loop
loop {
    term.draw(|f| {
        // Get `ratatui::layout::Rect` where the editor should be rendered
        let rect = ...;
        // `TextArea::widget` builds a widget to render the editor with tui
        let widget = textarea.widget();
        // Render the widget in terminal screen
        f.render_widget(widget, rect);
    })?;

    if let Event::Key(key) = read()? {
        // Your own key mapping to break the event loop
        if key.code == KeyCode::Esc {
            break;
        }
        // `TextArea::input` can directly handle key events from backends and update the editor state
        textarea.input(key);
    }
}

// Get text lines as `&[String]`
println!("Lines: {:?}", textarea.lines());
```

`TextArea` is an instance to manage the editor state. By default, it disables line numbers and highlights cursor line
with underline.

`TextArea::widget()` builds a widget to render the current state of the editor. Create the widget and render it on each
tick of event loop.

`TextArea::input()` receives inputs from tui backends. The method can take key events from backends such as
`crossterm::event::KeyEvent` or `termion::event::Key` directly if the features are enabled. The method handles default
key mappings as well.

Default key mappings are as follows:

| Mappings                                     | Description                               |
|----------------------------------------------|-------------------------------------------|
| `Ctrl+H`, `Backspace`                        | Delete one character before cursor        |
| `Ctrl+D`, `Delete`                           | Delete one character next to cursor       |
| `Ctrl+M`, `Enter`                            | Insert newline                            |
| `Ctrl+K`                                     | Delete from cursor until the end of line  |
| `Ctrl+J`                                     | Delete from cursor until the head of line |
| `Ctrl+W`, `Alt+H`, `Alt+Backspace`           | Delete one word before cursor             |
| `Alt+D`, `Alt+Delete`                        | Delete one word next to cursor            |
| `Ctrl+U`                                     | Undo                                      |
| `Ctrl+R`                                     | Redo                                      |
| `Ctrl+C`, `Copy`                             | Copy selected text                        |
| `Ctrl+X`, `Cut`                              | Cut selected text                         |
| `Ctrl+Y`, `Paste`                            | Paste yanked text                         |
| `Ctrl+F`, `→`                                | Move cursor forward by one character      |
| `Ctrl+B`, `←`                                | Move cursor backward by one character     |
| `Ctrl+P`, `↑`                                | Move cursor up by one line                |
| `Ctrl+N`, `↓`                                | Move cursor down by one line              |
| `Alt+F`, `Ctrl+→`                            | Move cursor forward by word               |
| `Atl+B`, `Ctrl+←`                            | Move cursor backward by word              |
| `Alt+]`, `Alt+P`, `Ctrl+↑`                   | Move cursor up by paragraph               |
| `Alt+[`, `Alt+N`, `Ctrl+↓`                   | Move cursor down by paragraph             |
| `Ctrl+E`, `End`, `Ctrl+Alt+F`, `Ctrl+Alt+→`  | Move cursor to the end of line            |
| `Ctrl+A`, `Home`, `Ctrl+Alt+B`, `Ctrl+Alt+←` | Move cursor to the head of line           |
| `Alt+<`, `Ctrl+Alt+P`, `Ctrl+Alt+↑`          | Move cursor to top of lines               |
| `Alt+>`, `Ctrl+Alt+N`, `Ctrl+Alt+↓`          | Move cursor to bottom of lines            |
| `Ctrl+V`, `PageDown`                         | Scroll down by page                       |
| `Alt+V`, `PageUp`                            | Scroll up by page                         |

Deleting multiple characters at once saves the deleted text to yank buffer. It can be pasted with `Ctrl+Y` later.

If you don't want to use default key mappings, see the 'Advanced Usage' section.

## Basic Usage

### Create `TextArea` instance with text

`TextArea` implements `Default` trait to create an editor instance with an empty text.

```rust,ignore
let mut textarea = TextArea::default();
```

`TextArea::new()` creates an editor instance with text lines passed as `Vec<String>`.

```rust,ignore
let mut lines: Vec<String> = ...;
let mut textarea = TextArea::new(lines);
```

`TextArea` implements `From<impl Iterator<Item=impl Into<String>>>`. `TextArea::from()` can create an editor instance
from any iterators whose elements can be converted to `String`.

```rust,ignore
// Create `TextArea` from from `[&str]`
let mut textarea = TextArea::from([
    "this is first line",
    "this is second line",
    "this is third line",
]);

// Create `TextArea` from `String`
let mut text: String = ...;
let mut textarea = TextArea::from(text.lines());
```

`TextArea` also implements `FromIterator<impl Into<String>>`. `Iterator::collect()` can collect strings as an editor
instance. This allows to create `TextArea` reading lines from file efficiently using `io::BufReader`.

```rust,ignore
let file = fs::File::open(path)?;
let mut textarea: TextArea = io::BufReader::new(file).lines().collect::<io::Result<_>>()?;
```

### Get text contents from `TextArea`

`TextArea::lines()` returns text lines as `&[String]`. It borrows text contents temporarily.

```rust,ignore
let text: String = textarea.lines().join("\n");
```

`TextArea::into_lines()` moves `TextArea` instance into text lines as `Vec<String>`. This can retrieve the text contents
without any copy.

```rust,ignore
let lines: Vec<String> = textarea.into_lines();
```

Note that `TextArea` always contains at least one line. For example, an empty text means one empty line. This is because
any text file must end with newline.

```rust,ignore
let textarea = TextArea::default();
assert_eq!(textarea.into_lines(), [""]);
```

### Show line number

By default, `TextArea` does now show line numbers. To enable, set a style for rendering line numbers by
`TextArea::set_line_number_style()`. For example, the following renders line numbers in dark gray background
color.

```rust,ignore
use ratatui::style::{Style, Color};

let style = Style::default().bg(Color::DarkGray);
textarea.set_line_number_style(style);
```

### Configure cursor line style

By default, `TextArea` renders the line at cursor with underline so that users can easily notice where the current line
is. To change the style of cursor line, use `TextArea::set_cursor_line_style()`. For example, the following styles the
cursor line with bold text.

```rust,ignore
use ratatui::style::{Style, Modifier};

let style = Style::default().add_modifier(Modifier::BOLD);
textarea.set_line_number_style(style);
```

To disable cursor line style, set the default style as follows:

```rust,ignore
use ratatui::style::{Style, Modifier};

textarea.set_line_number_style(Style::default());
```

### Configure tab width

The default tab width is 4. To change it, use `TextArea::set_tab_length()` method. The following sets 2 to tab width.
Typing tab key inserts 2 spaces.

```rust,ignore
textarea.set_tab_length(2);
```

### Configure max history size

By default, past 50 modifications are stored as edit history. The history is used for undo/redo. To change how many past
edits are remembered, use `TextArea::set_max_histories()` method. The following remembers past 1000 changes.

```rust,ignore
textarea.set_max_histories(1000);
```

Setting 0 disables undo/redo.

```rust,ignore
textarea.set_max_histories(0);
```

### Text search with regular expressions

To search text in textarea, set a regular expression pattern with `TextArea::set_search_pattern()` and move cursor with
`TextArea::search_forward()` for forward search or `TextArea::search_back()` backward search. The regular expression is
handled by [`regex` crate][regex].

Text search wraps around the textarea. When searching forward and no match found until the end of textarea, it searches
the pattern from start of the file.

Matches are highlighted in textarea. The text style to highlight matches can be changed with
`TextArea::set_search_style()`. Setting an empty string to `TextArea::set_search_pattern()` stops the text search.

```rust,ignore
// Start text search matching to "hello" or "hi". This highlights matches in textarea but does not move cursor.
// `regex::Error` is returned on invalid pattern.
textarea.set_search_pattern("(hello|hi)").unwrap();

textarea.search_forward(false); // Move cursor to the next match
textarea.search_back(false);    // Move cursor to the previous match

// Setting empty string stops the search
textarea.set_search_pattern("").unwrap();
```

No UI is provided for text search. You need to provide your own UI to input search query. It is recommended to use
another `TextArea` for search form. To build a single-line input form, see 'Single-line input like `<input>` in HTML' in
'Advanced Usage' section below.

[`editor` example](./examples/editor.rs) implements a text search with search form built on `TextArea`. See the
implementation for working example.

To use text search, `search` feature needs to be enabled in your `Cargo.toml`. It is disabled by default to avoid
depending on `regex` crate until it is necessary.

```toml
tui-textarea = { version = "*", features = ["search"] }
```

## Advanced Usage

### Single-line input like `<input>` in HTML

To use `TextArea` for single-line input widget like `<input>` in HTML, ignore all key mappings which inserts newline.

```rust,ignore
use crossterm::event::{Event, read};
use tui_textarea::{Input, Key};

let default_text: &str = ...;
let default_text = default_text.replace(&['\n', '\r'], " "); // Ensure no new line is contained
let mut textarea = TextArea::new(vec![default_text]);

// Event loop
loop {
    // ...

    // Using `Input` is not mandatory, but it's useful for pattern match
    // Ignore Ctrl+m and Enter. Otherwise handle keys as usual
    match read()?.into() {
        Input { key: Key::Char('m'), ctrl: true, alt: false }
        | Input { key: Key::Enter, .. } => continue,
        input => {
            textarea.input(key);
        }
    }
}

let text = textarea.into_lines().remove(0); // Get input text
```

See [`single_line` example](./examples/single_line.rs) for working example.

### Define your own key mappings

All editor operations are defined as public methods of `TextArea`. To move cursor, use `tui_textarea::CursorMove` to
notify how to move the cursor.

| Method                                               | Operation                                       |
|------------------------------------------------------|-------------------------------------------------|
| `textarea.delete_char()`                             | Delete one character before cursor              |
| `textarea.delete_next_char()`                        | Delete one character next to cursor             |
| `textarea.insert_newline()`                          | Insert newline                                  |
| `textarea.delete_line_by_end()`                      | Delete from cursor until the end of line        |
| `textarea.delete_line_by_head()`                     | Delete from cursor until the head of line       |
| `textarea.delete_word()`                             | Delete one word before cursor                   |
| `textarea.delete_next_word()`                        | Delete one word next to cursor                  |
| `textarea.undo()`                                    | Undo                                            |
| `textarea.redo()`                                    | Redo                                            |
| `textarea.copy()`                                    | Copy selected text                              |
| `textarea.cut()`                                     | Cut selected text                               |
| `textarea.paste()`                                   | Paste yanked text                               |
| `textarea.start_selection()`                         | Start text selection                            |
| `textarea.cancel_selection()`                        | Cancel text selection                           |
| `textarea.select_all()`                              | Select entire text                              |
| `textarea.move_cursor(CursorMove::Forward)`          | Move cursor forward by one character            |
| `textarea.move_cursor(CursorMove::Back)`             | Move cursor backward by one character           |
| `textarea.move_cursor(CursorMove::Up)`               | Move cursor up by one line                      |
| `textarea.move_cursor(CursorMove::Down)`             | Move cursor down by one line                    |
| `textarea.move_cursor(CursorMove::WordForward)`      | Move cursor forward by word                     |
| `textarea.move_cursor(CursorMove::WordBack)`         | Move cursor backward by word                    |
| `textarea.move_cursor(CursorMove::ParagraphForward)` | Move cursor up by paragraph                     |
| `textarea.move_cursor(CursorMove::ParagraphBack)`    | Move cursor down by paragraph                   |
| `textarea.move_cursor(CursorMove::End)`              | Move cursor to the end of line                  |
| `textarea.move_cursor(CursorMove::Head)`             | Move cursor to the head of line                 |
| `textarea.move_cursor(CursorMove::Top)`              | Move cursor to top of lines                     |
| `textarea.move_cursor(CursorMove::Bottom)`           | Move cursor to bottom of lines                  |
| `textarea.move_cursor(CursorMove::Jump(row, col))`   | Move cursor to (row, col) position              |
| `textarea.move_cursor(CursorMove::InViewport)`       | Move cursor to stay in the viewport             |
| `textarea.set_search_pattern(pattern)`               | Set a pattern for text search                   |
| `textarea.search_forward(match_cursor)`              | Move cursor to next match of text search        |
| `textarea.search_back(match_cursor)`                 | Move cursor to previous match of text search    |
| `textarea.scroll(Scrolling::PageDown)`               | Scroll down the viewport by page                |
| `textarea.scroll(Scrolling::PageUp)`                 | Scroll up the viewport by page                  |
| `textarea.scroll(Scrolling::HalfPageDown)`           | Scroll down the viewport by half-page           |
| `textarea.scroll(Scrolling::HalfPageUp)`             | Scroll up the viewport by half-page             |
| `textarea.scroll((row, col))`                        | Scroll down the viewport to (row, col) position |

To define your own key mappings, simply call the above methods in your code instead of `TextArea::input()` method.

See the [`vim` example](./examples/vim.rs) for working example. It implements more Vim-like key modal mappings.

If you don't want to use default key mappings, `TextArea::input_without_shortcuts()` method can be used instead of
`TextArea::input()`. The method only handles very basic operations such as inserting/deleting single characters, tabs,
newlines.

```rust,ignore
match read()?.into() {
    // Handle your own key mappings here
    // ...
    input => textarea.input_without_shortcuts(input),
}
```

### Use your own backend

ratatui and tui-rs allows to make your own backend by implementing [`ratatui::backend::Backend`][ratatui-backend] trait.
tui-textarea supports it as well. Please use `no-backend` feature for [ratatui][] or `tuirs-no-backend` feature for
[tui-rs][]. They avoid adding backend crates (crossterm, termion, or termwiz) since you're using your own backend.

```toml
[dependencies]
# For ratatui
tui-textarea = { version = "*", default-features = false, features = ["no-backend"] }
# For tui-rs
tui-textarea = { version = "*", default-features = false, features = ["tuirs-no-backend"] }
```

`tui_textarea::Input` is a type for backend-agnostic key input. What you need to do is converting key event in your own
backend into the `tui_textarea::Input` instance. Then `TextArea::input()` method can handle the input as other backend.

In the following example, let's say `your_backend::KeyDown` is a key event type for your backend and
`your_backend::read_next_key()` returns the next key event.

```rust,ignore
// In your backend implementation

pub enum KeyDown {
    Char(char),
    BS,
    Del,
    Esc,
    // ...
}

// Return tuple of (key, ctrlkey, altkey)
pub fn read_next_key() -> (KeyDown, bool, bool) {
    // ...
}
```

Then you can implement the logic to convert `your_backend::KeyDown` value into `tui_textarea::Input` value.

```rust,ignore
use tui_textarea::{Input, Key};
use your_backend::KeyDown;

fn keydown_to_input(key: KeyDown, ctrl: bool, alt: bool) -> Input {
    match key {
        KeyDown::Char(c) => Input { key: Key::Char(c), ctrl, alt },
        KeyDown::BS => Input { key: Key::Backspace, ctrl, alt },
        KeyDown::Del => Input { key: Key::Delete, ctrl, alt },
        KeyDown::Esc => Input { key: Key::Esc, ctrl, alt },
        // ...
        _ => Input::default(),
    }
}
```

For the keys which are not handled by tui-textarea, `tui_textarea::Input::default()` is available. It returns 'null'
key. An editor will do nothing with the key.

Finally, convert your own backend's key input type into `tui_textarea::Input` and pass it to `TextArea::input()`.

```rust,ignore
let mut textarea = ...;

// Event loop
loop {
    // ...

    let (key, ctrl, alt) = your_backend::read_next_key();
    if key == your_backend::KeyDown::Esc {
        break; // For example, quit your app on pressing Esc
    }
    textarea.input(keydown_to_input(key, ctrl, alt));
}
```

### Put multiple `TextArea` instances in screen

You don't need to do anything special. Create multiple `TextArea` instances and render widgets built from each instances.

The following is an example to put two textarea widgets in application and manage the focus.

```rust,ignore
use tui_textarea::{TextArea, Input, Key};
use crossterm::event::{Event, read};

let editors = &mut [
    TextArea::default(),
    TextArea::default(),
];

let mut focused = 0;

loop {
    term.draw(|f| {
        let rects = ...;

        for (editor, rect) in editors.iter_mut().zip(rects.into_iter()) {
            let widget = editor.widget();
            f.render_widget(widget, rect);
        }
    })?;

    match read()?.into() {
        // Switch focused textarea by Ctrl+S
        Input { key: Key::Char('s'), ctrl: true, .. } => focused = (focused + 1) % 2;
        // Handle input by the focused editor
        input => editors[focused].input(input),
    }
}
```

See [`split` example](./examples/split.rs) and [`editor` example](./examples/editor.rs) for working example.

## Minimum Supported Rust Version

MSRV of this crate is depending on `tui` crate. Currently MSRV is 1.56.1. Note that `ratatui` crate requires more recent Rust version.

## Versioning

This crate is not reaching v1.0.0 yet. There is no plan to bump the major version for now. Current versioning policy is
as follows:

- Major: Fixed to 0
- Minor: Bump on breaking change
- Patch: Bump on new feature or bug fix

## Contributing to tui-textarea

This project is developed [on GitHub][repo].

For feature requests or bug reports, please [create an issue][new-issue]. For submitting patches, please [create a pull
request][pulls].

Please read [CONTRIBUTING.md](./CONTRIBUTING.md) before reporting an issue or making a PR.

## License

tui-textarea is distributed under [The MIT License](./LICENSE.txt).

[crates-io-badge]: https://img.shields.io/crates/v/tui-textarea.svg
[crate]: https://crates.io/crates/tui-textarea
[doc-badge]: https://docs.rs/tui-textarea/badge.svg
[doc]: https://docs.rs/tui-textarea/latest/tui_textarea/
[ci-badge]: https://github.com/rhysd/tui-textarea/actions/workflows/ci.yml/badge.svg?event=push
[ci]: https://github.com/rhysd/tui-textarea/actions/workflows/ci.yml
[codecov-badge]: https://codecov.io/gh/rhysd/tui-textarea/graph/badge.svg?token=YAA3EVRXAY
[codecov]: https://codecov.io/gh/rhysd/tui-textarea
[tui-rs]: https://github.com/fdehau/tui-rs
[ratatui]: https://github.com/ratatui-org/ratatui
[crossterm]: https://docs.rs/crossterm/latest/crossterm/
[termion]: https://docs.rs/termion/latest/termion/
[termwiz]: https://docs.rs/termwiz/latest/termwiz/
[ratatui-backend]: https://docs.rs/ratatui/latest/ratatui/backend/trait.Backend.html
[repo]: https://github.com/rhysd/tui-textarea
[new-issue]: https://github.com/rhysd/tui-textarea/issues/new
[pulls]: https://github.com/rhysd/tui-textarea/pulls
[regex]: https://docs.rs/regex/latest/regex/