xref: /aosp_15_r20/external/rust/android-crates-io/crates/textwrap/src/lib.rs

//! The textwrap library provides functions for word wrapping and
//! indenting text.
//!
//! # Wrapping Text
//!
//! Wrapping text can be very useful in command-line programs where
//! you want to format dynamic output nicely so it looks good in a
//! terminal. A quick example:
//!
//! ```
//! # #[cfg(feature = "smawk")] {
//! let text = "textwrap: a small library for wrapping text.";
//! assert_eq!(textwrap::wrap(text, 18),
//!            vec!["textwrap: a",
//!                 "small library for",
//!                 "wrapping text."]);
//! # }
//! ```
//!
//! The [`wrap`] function returns the individual lines, use [`fill`]
//! is you want the lines joined with `'\n'` to form a `String`.
//!
//! If you enable the `hyphenation` Cargo feature, you can get
//! automatic hyphenation for a number of languages:
//!
//! ```
//! #[cfg(feature = "hyphenation")] {
//! use hyphenation::{Language, Load, Standard};
//! use textwrap::{wrap, Options, WordSplitter};
//!
//! let text = "textwrap: a small library for wrapping text.";
//! let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
//! let options = Options::new(18).word_splitter(WordSplitter::Hyphenation(dictionary));
//! assert_eq!(wrap(text, &options),
//!            vec!["textwrap: a small",
//!                 "library for wrap-",
//!                 "ping text."]);
//! }
//! ```
//!
//! See also the [`unfill`] and [`refill`] functions which allow you to
//! manipulate already wrapped text.
//!
//! ## Wrapping Strings at Compile Time
//!
//! If your strings are known at compile time, please take a look at
//! the procedural macros from the [textwrap-macros] crate.
//!
//! ## Displayed Width vs Byte Size
//!
//! To word wrap text, one must know the width of each word so one can
//! know when to break lines. This library will by default measure the
//! width of text using the _displayed width_, not the size in bytes.
//! The `unicode-width` Cargo feature controls this.
//!
//! This is important for non-ASCII text. ASCII characters such as `a`
//! and `!` are simple and take up one column each. This means that
//! the displayed width is equal to the string length in bytes.
//! However, non-ASCII characters and symbols take up more than one
//! byte when UTF-8 encoded: `é` is `0xc3 0xa9` (two bytes) and `⚙` is
//! `0xe2 0x9a 0x99` (three bytes) in UTF-8, respectively.
//!
//! This is why we take care to use the displayed width instead of the
//! byte count when computing line lengths. All functions in this
//! library handle Unicode characters like this when the
//! `unicode-width` Cargo feature is enabled (it is enabled by
//! default).
//!
//! # Indentation and Dedentation
//!
//! The textwrap library also offers functions for adding a prefix to
//! every line of a string and to remove leading whitespace. As an
//! example, the [`indent`] function allows you to turn lines of text
//! into a bullet list:
//!
//! ```
//! let before = "\
//! foo
//! bar
//! baz
//! ";
//! let after = "\
//! * foo
//! * bar
//! * baz
//! ";
//! assert_eq!(textwrap::indent(before, "* "), after);
//! ```
//!
//! Removing leading whitespace is done with [`dedent`]:
//!
//! ```
//! let before = "
//!     Some
//!       indented
//!         text
//! ";
//! let after = "
//! Some
//!   indented
//!     text
//! ";
//! assert_eq!(textwrap::dedent(before), after);
//! ```
//!
//! # Cargo Features
//!
//! The textwrap library can be slimmed down as needed via a number of
//! Cargo features. This means you only pay for the features you
//! actually use.
//!
//! The full dependency graph, where dashed lines indicate optional
//! dependencies, is shown below:
//!
//! <img src="https://raw.githubusercontent.com/mgeisler/textwrap/master/images/textwrap-0.16.0.svg">
//!
//! ## Default Features
//!
//! These features are enabled by default:
//!
//! * `unicode-linebreak`: enables finding words using the
//!   [unicode-linebreak] crate, which implements the line breaking
//!   algorithm described in [Unicode Standard Annex
//!   #14](https://www.unicode.org/reports/tr14/).
//!
//!   This feature can be disabled if you are happy to find words
//!   separated by ASCII space characters only. People wrapping text
//!   with emojis or East-Asian characters will want most likely want
//!   to enable this feature. See [`WordSeparator`] for details.
//!
//! * `unicode-width`: enables correct width computation of non-ASCII
//!   characters via the [unicode-width] crate. Without this feature,
//!   every [`char`] is 1 column wide, except for emojis which are 2
//!   columns wide. See the [`core::display_width`] function for
//!   details.
//!
//!   This feature can be disabled if you only need to wrap ASCII
//!   text, or if the functions in [`core`] are used directly with
//!   [`core::Fragment`]s for which the widths have been computed in
//!   other ways.
//!
//! * `smawk`: enables linear-time wrapping of the whole paragraph via
//!   the [smawk] crate. See the [`wrap_algorithms::wrap_optimal_fit`]
//!   function for details on the optimal-fit algorithm.
//!
//!   This feature can be disabled if you only ever intend to use
//!   [`wrap_algorithms::wrap_first_fit`].
//!
//! <!-- begin binary-sizes -->
//!
//! With Rust 1.64.0, the size impact of the above features on your
//! binary is as follows:
//!
//! | Configuration                            |  Binary Size |    Delta |
//! | :---                                     |         ---: |     ---: |
//! | quick-and-dirty implementation           |       289 KB |     — KB |
//! | textwrap without default features        |       305 KB |    16 KB |
//! | textwrap with smawk                      |       317 KB |    28 KB |
//! | textwrap with unicode-width              |       309 KB |    20 KB |
//! | textwrap with unicode-linebreak          |       342 KB |    53 KB |
//!
//! <!-- end binary-sizes -->
//!
//! The above sizes are the stripped sizes and the binary is compiled
//! in release mode with this profile:
//!
//! ```toml
//! [profile.release]
//! lto = true
//! codegen-units = 1
//! ```
//!
//! See the [binary-sizes demo] if you want to reproduce these
//! results.
//!
//! ## Optional Features
//!
//! These Cargo features enable new functionality:
//!
//! * `terminal_size`: enables automatic detection of the terminal
//!   width via the [terminal_size] crate. See the
//!   [`Options::with_termwidth`] constructor for details.
//!
//! * `hyphenation`: enables language-sensitive hyphenation via the
//!   [hyphenation] crate. See the [`word_splitters::WordSplitter`]
//!   trait for details.
//!
//! [unicode-linebreak]: https://docs.rs/unicode-linebreak/
//! [unicode-width]: https://docs.rs/unicode-width/
//! [smawk]: https://docs.rs/smawk/
//! [binary-sizes demo]: https://github.com/mgeisler/textwrap/tree/master/examples/binary-sizes
//! [textwrap-macros]: https://docs.rs/textwrap-macros/
//! [terminal_size]: https://docs.rs/terminal_size/
//! [hyphenation]: https://docs.rs/hyphenation/

#![doc(html_root_url = "https://docs.rs/textwrap/0.16.0")]
#![forbid(unsafe_code)] // See https://github.com/mgeisler/textwrap/issues/210
#![deny(missing_docs)]
#![deny(missing_debug_implementations)]
#![allow(clippy::redundant_field_names)]

// Make `cargo test` execute the README doctests.
#[cfg(doctest)]
#[doc = include_str!("../README.md")]
mod readme_doctest {}

use std::borrow::Cow;

mod indentation;
pub use crate::indentation::{dedent, indent};

mod word_separators;
pub use word_separators::WordSeparator;

pub mod word_splitters;
pub use word_splitters::WordSplitter;

pub mod wrap_algorithms;
pub use wrap_algorithms::WrapAlgorithm;

mod line_ending;
pub use line_ending::LineEnding;

pub mod core;

// This module is only active when running fuzz tests. It provides
// access to private helpers.
#[cfg(fuzzing)]
pub mod fuzzing;

/// Holds configuration options for wrapping and filling text.
#[non_exhaustive]
#[derive(Debug, Clone)]
pub struct Options<'a> {
    /// The width in columns at which the text will be wrapped.
    pub width: usize,
    /// Line ending used for breaking lines.
    pub line_ending: LineEnding,
    /// Indentation used for the first line of output. See the
    /// [`Options::initial_indent`] method.
    pub initial_indent: &'a str,
    /// Indentation used for subsequent lines of output. See the
    /// [`Options::subsequent_indent`] method.
    pub subsequent_indent: &'a str,
    /// Allow long words to be broken if they cannot fit on a line.
    /// When set to `false`, some lines may be longer than
    /// `self.width`. See the [`Options::break_words`] method.
    pub break_words: bool,
    /// Wrapping algorithm to use, see the implementations of the
    /// [`wrap_algorithms::WrapAlgorithm`] trait for details.
    pub wrap_algorithm: WrapAlgorithm,
    /// The line breaking algorithm to use, see
    /// [`word_separators::WordSeparator`] trait for an overview and
    /// possible implementations.
    pub word_separator: WordSeparator,
    /// The method for splitting words. This can be used to prohibit
    /// splitting words on hyphens, or it can be used to implement
    /// language-aware machine hyphenation.
    pub word_splitter: WordSplitter,
}

impl<'a> From<&'a Options<'a>> for Options<'a> {
    fn from(options: &'a Options<'a>) -> Self {
        Self {
            width: options.width,
            line_ending: options.line_ending,
            initial_indent: options.initial_indent,
            subsequent_indent: options.subsequent_indent,
            break_words: options.break_words,
            word_separator: options.word_separator,
            wrap_algorithm: options.wrap_algorithm,
            word_splitter: options.word_splitter.clone(),
        }
    }
}

impl<'a> From<usize> for Options<'a> {
    fn from(width: usize) -> Self {
        Options::new(width)
    }
}

impl<'a> Options<'a> {
    /// Creates a new [`Options`] with the specified width.
    ///
    /// The other fields are given default values as follows:
    ///
    /// ```
    /// # use textwrap::{LineEnding, Options, WordSplitter, WordSeparator, WrapAlgorithm};
    /// # let width = 80;
    /// let options = Options::new(width);
    /// assert_eq!(options.line_ending, LineEnding::LF);
    /// assert_eq!(options.initial_indent, "");
    /// assert_eq!(options.subsequent_indent, "");
    /// assert_eq!(options.break_words, true);
    ///
    /// #[cfg(feature = "unicode-linebreak")]
    /// assert_eq!(options.word_separator, WordSeparator::UnicodeBreakProperties);
    /// #[cfg(not(feature = "unicode-linebreak"))]
    /// assert_eq!(options.word_separator, WordSeparator::AsciiSpace);
    ///
    /// #[cfg(feature = "smawk")]
    /// assert_eq!(options.wrap_algorithm, WrapAlgorithm::new_optimal_fit());
    /// #[cfg(not(feature = "smawk"))]
    /// assert_eq!(options.wrap_algorithm, WrapAlgorithm::FirstFit);
    ///
    /// assert_eq!(options.word_splitter, WordSplitter::HyphenSplitter);
    /// ```
    ///
    /// Note that the default word separator and wrap algorithms
    /// changes based on the available Cargo features. The best
    /// available algorithms are used by default.
    pub const fn new(width: usize) -> Self {
        Options {
            width,
            line_ending: LineEnding::LF,
            initial_indent: "",
            subsequent_indent: "",
            break_words: true,
            word_separator: WordSeparator::new(),
            wrap_algorithm: WrapAlgorithm::new(),
            word_splitter: WordSplitter::HyphenSplitter,
        }
    }

    /// Creates a new [`Options`] with `width` set to the current
    /// terminal width. If the terminal width cannot be determined
    /// (typically because the standard input and output is not
    /// connected to a terminal), a width of 80 characters will be
    /// used. Other settings use the same defaults as
    /// [`Options::new`].
    ///
    /// Equivalent to:
    ///
    /// ```no_run
    /// use textwrap::{termwidth, Options};
    ///
    /// let options = Options::new(termwidth());
    /// ```
    ///
    /// **Note:** Only available when the `terminal_size` feature is
    /// enabled.
    #[cfg(feature = "terminal_size")]
    pub fn with_termwidth() -> Self {
        Self::new(termwidth())
    }

    /// Change [`self.line_ending`]. This specifies which of the
    /// supported line endings should be used to break the lines of the
    /// input text.
    ///
    /// # Examples
    ///
    /// ```
    /// use textwrap::{refill, LineEnding, Options};
    ///
    /// let options = Options::new(15).line_ending(LineEnding::CRLF);
    /// assert_eq!(refill("This is a little example.", options),
    ///            "This is a\r\nlittle example.");
    /// ```
    ///
    /// [`self.line_ending`]: #structfield.line_ending
    pub fn line_ending(self, line_ending: LineEnding) -> Self {
        Options {
            line_ending,
            ..self
        }
    }

    /// Change [`self.initial_indent`]. The initial indentation is
    /// used on the very first line of output.
    ///
    /// # Examples
    ///
    /// Classic paragraph indentation can be achieved by specifying an
    /// initial indentation and wrapping each paragraph by itself:
    ///
    /// ```
    /// use textwrap::{wrap, Options};
    ///
    /// let options = Options::new(16).initial_indent("    ");
    /// assert_eq!(wrap("This is a little example.", options),
    ///            vec!["    This is a",
    ///                 "little example."]);
    /// ```
    ///
    /// [`self.initial_indent`]: #structfield.initial_indent
    pub fn initial_indent(self, indent: &'a str) -> Self {
        Options {
            initial_indent: indent,
            ..self
        }
    }

    /// Change [`self.subsequent_indent`]. The subsequent indentation
    /// is used on lines following the first line of output.
    ///
    /// # Examples
    ///
    /// Combining initial and subsequent indentation lets you format a
    /// single paragraph as a bullet list:
    ///
    /// ```
    /// use textwrap::{wrap, Options};
    ///
    /// let options = Options::new(12)
    ///     .initial_indent("* ")
    ///     .subsequent_indent("  ");
    /// #[cfg(feature = "smawk")]
    /// assert_eq!(wrap("This is a little example.", options),
    ///            vec!["* This is",
    ///                 "  a little",
    ///                 "  example."]);
    ///
    /// // Without the `smawk` feature, the wrapping is a little different:
    /// #[cfg(not(feature = "smawk"))]
    /// assert_eq!(wrap("This is a little example.", options),
    ///            vec!["* This is a",
    ///                 "  little",
    ///                 "  example."]);
    /// ```
    ///
    /// [`self.subsequent_indent`]: #structfield.subsequent_indent
    pub fn subsequent_indent(self, indent: &'a str) -> Self {
        Options {
            subsequent_indent: indent,
            ..self
        }
    }

    /// Change [`self.break_words`]. This controls if words longer
    /// than `self.width` can be broken, or if they will be left
    /// sticking out into the right margin.
    ///
    /// See [`Options::word_splitter`] instead if you want to control
    /// hyphenation.
    ///
    /// # Examples
    ///
    /// ```
    /// use textwrap::{wrap, Options};
    ///
    /// let options = Options::new(4).break_words(true);
    /// assert_eq!(wrap("This is a little example.", options),
    ///            vec!["This",
    ///                 "is a",
    ///                 "litt",
    ///                 "le",
    ///                 "exam",
    ///                 "ple."]);
    /// ```
    ///
    /// [`self.break_words`]: #structfield.break_words
    pub fn break_words(self, setting: bool) -> Self {
        Options {
            break_words: setting,
            ..self
        }
    }

    /// Change [`self.word_separator`].
    ///
    /// See [`word_separators::WordSeparator`] for details on the choices.
    ///
    /// [`self.word_separator`]: #structfield.word_separator
    pub fn word_separator(self, word_separator: WordSeparator) -> Options<'a> {
        Options {
            width: self.width,
            line_ending: self.line_ending,
            initial_indent: self.initial_indent,
            subsequent_indent: self.subsequent_indent,
            break_words: self.break_words,
            word_separator: word_separator,
            wrap_algorithm: self.wrap_algorithm,
            word_splitter: self.word_splitter,
        }
    }

    /// Change [`self.wrap_algorithm`].
    ///
    /// See the [`wrap_algorithms::WrapAlgorithm`] trait for details on
    /// the choices.
    ///
    /// [`self.wrap_algorithm`]: #structfield.wrap_algorithm
    pub fn wrap_algorithm(self, wrap_algorithm: WrapAlgorithm) -> Options<'a> {
        Options {
            width: self.width,
            line_ending: self.line_ending,
            initial_indent: self.initial_indent,
            subsequent_indent: self.subsequent_indent,
            break_words: self.break_words,
            word_separator: self.word_separator,
            wrap_algorithm: wrap_algorithm,
            word_splitter: self.word_splitter,
        }
    }

    /// Change [`self.word_splitter`]. The
    /// [`word_splitters::WordSplitter`] is used to fit part of a word
    /// into the current line when wrapping text.
    ///
    /// See [`Options::break_words`] instead if you want to control the
    /// handling of words longer than the line width.
    ///
    /// # Examples
    ///
    /// ```
    /// use textwrap::{wrap, Options, WordSplitter};
    ///
    /// // The default is WordSplitter::HyphenSplitter.
    /// let options = Options::new(5);
    /// assert_eq!(wrap("foo-bar-baz", &options),
    ///            vec!["foo-", "bar-", "baz"]);
    ///
    /// // The word is now so long that break_words kick in:
    /// let options = Options::new(5)
    ///     .word_splitter(WordSplitter::NoHyphenation);
    /// assert_eq!(wrap("foo-bar-baz", &options),
    ///            vec!["foo-b", "ar-ba", "z"]);
    ///
    /// // If you want to breaks at all, disable both:
    /// let options = Options::new(5)
    ///     .break_words(false)
    ///     .word_splitter(WordSplitter::NoHyphenation);
    /// assert_eq!(wrap("foo-bar-baz", &options),
    ///            vec!["foo-bar-baz"]);
    /// ```
    ///
    /// [`self.word_splitter`]: #structfield.word_splitter
    pub fn word_splitter(self, word_splitter: WordSplitter) -> Options<'a> {
        Options {
            width: self.width,
            line_ending: self.line_ending,
            initial_indent: self.initial_indent,
            subsequent_indent: self.subsequent_indent,
            break_words: self.break_words,
            word_separator: self.word_separator,
            wrap_algorithm: self.wrap_algorithm,
            word_splitter,
        }
    }
}

/// Return the current terminal width.
///
/// If the terminal width cannot be determined (typically because the
/// standard output is not connected to a terminal), a default width
/// of 80 characters will be used.
///
/// # Examples
///
/// Create an [`Options`] for wrapping at the current terminal width
/// with a two column margin to the left and the right:
///
/// ```no_run
/// use textwrap::{termwidth, Options};
///
/// let width = termwidth() - 4; // Two columns on each side.
/// let options = Options::new(width)
///     .initial_indent("  ")
///     .subsequent_indent("  ");
/// ```
///
/// **Note:** Only available when the `terminal_size` Cargo feature is
/// enabled.
#[cfg(feature = "terminal_size")]
pub fn termwidth() -> usize {
    terminal_size::terminal_size().map_or(80, |(terminal_size::Width(w), _)| w.into())
}

/// Fill a line of text at a given width.
///
/// The result is a [`String`], complete with newlines between each
/// line. Use the [`wrap`] function if you need access to the
/// individual lines.
///
/// The easiest way to use this function is to pass an integer for
/// `width_or_options`:
///
/// ```
/// use textwrap::fill;
///
/// assert_eq!(
///     fill("Memory safety without garbage collection.", 15),
///     "Memory safety\nwithout garbage\ncollection."
/// );
/// ```
///
/// If you need to customize the wrapping, you can pass an [`Options`]
/// instead of an `usize`:
///
/// ```
/// use textwrap::{fill, Options};
///
/// let options = Options::new(15)
///     .initial_indent("- ")
///     .subsequent_indent("  ");
/// assert_eq!(
///     fill("Memory safety without garbage collection.", &options),
///     "- Memory safety\n  without\n  garbage\n  collection."
/// );
/// ```
pub fn fill<'a, Opt>(text: &str, width_or_options: Opt) -> String
where
    Opt: Into<Options<'a>>,
{
    let options = width_or_options.into();

    if text.len() < options.width && !text.contains('\n') && options.initial_indent.is_empty() {
        String::from(text.trim_end_matches(' '))
    } else {
        fill_slow_path(text, options)
    }
}

/// Slow path for fill.
///
/// This is taken when `text` is longer than `options.width`.
fn fill_slow_path(text: &str, options: Options<'_>) -> String {
    // This will avoid reallocation in simple cases (no
    // indentation, no hyphenation).
    let mut result = String::with_capacity(text.len());

    let line_ending_str = options.line_ending.as_str();
    for (i, line) in wrap(text, options).iter().enumerate() {
        if i > 0 {
            result.push_str(line_ending_str);
        }
        result.push_str(line);
    }

    result
}

/// Unpack a paragraph of already-wrapped text.
///
/// This function attempts to recover the original text from a single
/// paragraph of text produced by the [`fill`] function. This means
/// that it turns
///
/// ```text
/// textwrap: a small
/// library for
/// wrapping text.
/// ```
///
/// back into
///
/// ```text
/// textwrap: a small library for wrapping text.
/// ```
///
/// In addition, it will recognize a common prefix and a common line
/// ending among the lines.
///
/// The prefix of the first line is returned in
/// [`Options::initial_indent`] and the prefix (if any) of the the
/// other lines is returned in [`Options::subsequent_indent`].
///
/// Line ending is returned in [`Options::line_ending`]. If line ending
/// can not be confidently detected (mixed or no line endings in the
/// input), [`LineEnding::LF`] will be returned.
///
/// In addition to `' '`, the prefixes can consist of characters used
/// for unordered lists (`'-'`, `'+'`, and `'*'`) and block quotes
/// (`'>'`) in Markdown as well as characters often used for inline
/// comments (`'#'` and `'/'`).
///
/// The text must come from a single wrapped paragraph. This means
/// that there can be no empty lines (`"\n\n"` or `"\r\n\r\n"`) within
/// the text. It is unspecified what happens if `unfill` is called on
/// more than one paragraph of text.
///
/// # Examples
///
/// ```
/// use textwrap::{LineEnding, unfill};
///
/// let (text, options) = unfill("\
/// * This is an
///   example of
///   a list item.
/// ");
///
/// assert_eq!(text, "This is an example of a list item.\n");
/// assert_eq!(options.initial_indent, "* ");
/// assert_eq!(options.subsequent_indent, "  ");
/// assert_eq!(options.line_ending, LineEnding::LF);
/// ```
pub fn unfill(text: &str) -> (String, Options<'_>) {
    let prefix_chars: &[_] = &[' ', '-', '+', '*', '>', '#', '/'];

    let mut options = Options::new(0);
    for (idx, line) in text.lines().enumerate() {
        options.width = std::cmp::max(options.width, core::display_width(line));
        let without_prefix = line.trim_start_matches(prefix_chars);
        let prefix = &line[..line.len() - without_prefix.len()];

        if idx == 0 {
            options.initial_indent = prefix;
        } else if idx == 1 {
            options.subsequent_indent = prefix;
        } else if idx > 1 {
            for ((idx, x), y) in prefix.char_indices().zip(options.subsequent_indent.chars()) {
                if x != y {
                    options.subsequent_indent = &prefix[..idx];
                    break;
                }
            }
            if prefix.len() < options.subsequent_indent.len() {
                options.subsequent_indent = prefix;
            }
        }
    }

    let mut unfilled = String::with_capacity(text.len());
    let mut detected_line_ending = None;

    for (idx, (line, ending)) in line_ending::NonEmptyLines(text).enumerate() {
        if idx == 0 {
            unfilled.push_str(&line[options.initial_indent.len()..]);
        } else {
            unfilled.push(' ');
            unfilled.push_str(&line[options.subsequent_indent.len()..]);
        }
        match (detected_line_ending, ending) {
            (None, Some(_)) => detected_line_ending = ending,
            (Some(LineEnding::CRLF), Some(LineEnding::LF)) => detected_line_ending = ending,
            _ => (),
        }
    }

    // Add back a line ending if `text` ends with the one we detect.
    if let Some(line_ending) = detected_line_ending {
        if text.ends_with(line_ending.as_str()) {
            unfilled.push_str(line_ending.as_str());
        }
    }

    options.line_ending = detected_line_ending.unwrap_or(LineEnding::LF);
    (unfilled, options)
}

/// Refill a paragraph of wrapped text with a new width.
///
/// This function will first use the [`unfill`] function to remove
/// newlines from the text. Afterwards the text is filled again using
/// the [`fill`] function.
///
/// The `new_width_or_options` argument specify the new width and can
/// specify other options as well — except for
/// [`Options::initial_indent`] and [`Options::subsequent_indent`],
/// which are deduced from `filled_text`.
///
/// # Examples
///
/// ```
/// use textwrap::refill;
///
/// // Some loosely wrapped text. The "> " prefix is recognized automatically.
/// let text = "\
/// > Memory
/// > safety without garbage
/// > collection.
/// ";
///
/// assert_eq!(refill(text, 20), "\
/// > Memory safety
/// > without garbage
/// > collection.
/// ");
///
/// assert_eq!(refill(text, 40), "\
/// > Memory safety without garbage
/// > collection.
/// ");
///
/// assert_eq!(refill(text, 60), "\
/// > Memory safety without garbage collection.
/// ");
/// ```
///
/// You can also reshape bullet points:
///
/// ```
/// use textwrap::refill;
///
/// let text = "\
/// - This is my
///   list item.
/// ";
///
/// assert_eq!(refill(text, 20), "\
/// - This is my list
///   item.
/// ");
/// ```
pub fn refill<'a, Opt>(filled_text: &str, new_width_or_options: Opt) -> String
where
    Opt: Into<Options<'a>>,
{
    let mut new_options = new_width_or_options.into();
    let (text, options) = unfill(filled_text);
    // The original line ending is kept by `unfill`.
    let stripped = text.strip_suffix(options.line_ending.as_str());
    let new_line_ending = new_options.line_ending.as_str();

    new_options.initial_indent = options.initial_indent;
    new_options.subsequent_indent = options.subsequent_indent;
    let mut refilled = fill(stripped.unwrap_or(&text), new_options);

    // Add back right line ending if we stripped one off above.
    if stripped.is_some() {
        refilled.push_str(new_line_ending);
    }
    refilled
}

/// Wrap a line of text at a given width.
///
/// The result is a vector of lines, each line is of type [`Cow<'_,
/// str>`](Cow), which means that the line will borrow from the input
/// `&str` if possible. The lines do not have trailing whitespace,
/// including a final `'\n'`. Please use the [`fill`] function if you
/// need a [`String`] instead.
///
/// The easiest way to use this function is to pass an integer for
/// `width_or_options`:
///
/// ```
/// use textwrap::wrap;
///
/// let lines = wrap("Memory safety without garbage collection.", 15);
/// assert_eq!(lines, &[
///     "Memory safety",
///     "without garbage",
///     "collection.",
/// ]);
/// ```
///
/// If you need to customize the wrapping, you can pass an [`Options`]
/// instead of an `usize`:
///
/// ```
/// use textwrap::{wrap, Options};
///
/// let options = Options::new(15)
///     .initial_indent("- ")
///     .subsequent_indent("  ");
/// let lines = wrap("Memory safety without garbage collection.", &options);
/// assert_eq!(lines, &[
///     "- Memory safety",
///     "  without",
///     "  garbage",
///     "  collection.",
/// ]);
/// ```
///
/// # Optimal-Fit Wrapping
///
/// By default, `wrap` will try to ensure an even right margin by
/// finding breaks which avoid short lines. We call this an
/// “optimal-fit algorithm” since the line breaks are computed by
/// considering all possible line breaks. The alternative is a
/// “first-fit algorithm” which simply accumulates words until they no
/// longer fit on the line.
///
/// As an example, using the first-fit algorithm to wrap the famous
/// Hamlet quote “To be, or not to be: that is the question” in a
/// narrow column with room for only 10 characters looks like this:
///
/// ```
/// # use textwrap::{WrapAlgorithm::FirstFit, Options, wrap};
/// #
/// # let lines = wrap("To be, or not to be: that is the question",
/// #                  Options::new(10).wrap_algorithm(FirstFit));
/// # assert_eq!(lines.join("\n") + "\n", "\
/// To be, or
/// not to be:
/// that is
/// the
/// question
/// # ");
/// ```
///
/// Notice how the second to last line is quite narrow because
/// “question” was too large to fit? The greedy first-fit algorithm
/// doesn’t look ahead, so it has no other option than to put
/// “question” onto its own line.
///
/// With the optimal-fit wrapping algorithm, the previous lines are
/// shortened slightly in order to make the word “is” go into the
/// second last line:
///
/// ```
/// # #[cfg(feature = "smawk")] {
/// # use textwrap::{Options, WrapAlgorithm, wrap};
/// #
/// # let lines = wrap(
/// #     "To be, or not to be: that is the question",
/// #     Options::new(10).wrap_algorithm(WrapAlgorithm::new_optimal_fit())
/// # );
/// # assert_eq!(lines.join("\n") + "\n", "\
/// To be,
/// or not to
/// be: that
/// is the
/// question
/// # "); }
/// ```
///
/// Please see [`WrapAlgorithm`] for details on the choices.
///
/// # Examples
///
/// The returned iterator yields lines of type `Cow<'_, str>`. If
/// possible, the wrapped lines will borrow from the input string. As
/// an example, a hanging indentation, the first line can borrow from
/// the input, but the subsequent lines become owned strings:
///
/// ```
/// use std::borrow::Cow::{Borrowed, Owned};
/// use textwrap::{wrap, Options};
///
/// let options = Options::new(15).subsequent_indent("....");
/// let lines = wrap("Wrapping text all day long.", &options);
/// let annotated = lines
///     .iter()
///     .map(|line| match line {
///         Borrowed(text) => format!("[Borrowed] {}", text),
///         Owned(text) => format!("[Owned]    {}", text),
///     })
///     .collect::<Vec<_>>();
/// assert_eq!(
///     annotated,
///     &[
///         "[Borrowed] Wrapping text",
///         "[Owned]    ....all day",
///         "[Owned]    ....long.",
///     ]
/// );
/// ```
///
/// ## Leading and Trailing Whitespace
///
/// As a rule, leading whitespace (indentation) is preserved and
/// trailing whitespace is discarded.
///
/// In more details, when wrapping words into lines, words are found
/// by splitting the input text on space characters. One or more
/// spaces (shown here as “␣”) are attached to the end of each word:
///
/// ```text
/// "Foo␣␣␣bar␣baz" -> ["Foo␣␣␣", "bar␣", "baz"]
/// ```
///
/// These words are then put into lines. The interword whitespace is
/// preserved, unless the lines are wrapped so that the `"Foo␣␣␣"`
/// word falls at the end of a line:
///
/// ```
/// use textwrap::wrap;
///
/// assert_eq!(wrap("Foo   bar baz", 10), vec!["Foo   bar", "baz"]);
/// assert_eq!(wrap("Foo   bar baz", 8), vec!["Foo", "bar baz"]);
/// ```
///
/// Notice how the trailing whitespace is removed in both case: in the
/// first example, `"bar␣"` becomes `"bar"` and in the second case
/// `"Foo␣␣␣"` becomes `"Foo"`.
///
/// Leading whitespace is preserved when the following word fits on
/// the first line. To understand this, consider how words are found
/// in a text with leading spaces:
///
/// ```text
/// "␣␣foo␣bar" -> ["␣␣", "foo␣", "bar"]
/// ```
///
/// When put into lines, the indentation is preserved if `"foo"` fits
/// on the first line, otherwise you end up with an empty line:
///
/// ```
/// use textwrap::wrap;
///
/// assert_eq!(wrap("  foo bar", 8), vec!["  foo", "bar"]);
/// assert_eq!(wrap("  foo bar", 4), vec!["", "foo", "bar"]);
/// ```
pub fn wrap<'a, Opt>(text: &str, width_or_options: Opt) -> Vec<Cow<'_, str>>
where
    Opt: Into<Options<'a>>,
{
    let options: Options = width_or_options.into();
    let line_ending_str = options.line_ending.as_str();

    let mut lines = Vec::new();
    for line in text.split(line_ending_str) {
        wrap_single_line(line, &options, &mut lines);
    }

    lines
}

fn wrap_single_line<'a>(line: &'a str, options: &Options<'_>, lines: &mut Vec<Cow<'a, str>>) {
    let indent = if lines.is_empty() {
        options.initial_indent
    } else {
        options.subsequent_indent
    };
    if line.len() < options.width && indent.is_empty() {
        lines.push(Cow::from(line.trim_end_matches(' ')));
    } else {
        wrap_single_line_slow_path(line, options, lines)
    }
}

/// Wrap a single line of text.
///
/// This is taken when `line` is longer than `options.width`.
fn wrap_single_line_slow_path<'a>(
    line: &'a str,
    options: &Options<'_>,
    lines: &mut Vec<Cow<'a, str>>,
) {
    let initial_width = options
        .width
        .saturating_sub(core::display_width(options.initial_indent));
    let subsequent_width = options
        .width
        .saturating_sub(core::display_width(options.subsequent_indent));
    let line_widths = [initial_width, subsequent_width];

    let words = options.word_separator.find_words(line);
    let split_words = word_splitters::split_words(words, &options.word_splitter);
    let broken_words = if options.break_words {
        let mut broken_words = core::break_words(split_words, line_widths[1]);
        if !options.initial_indent.is_empty() {
            // Without this, the first word will always go into the
            // first line. However, since we break words based on the
            // _second_ line width, it can be wrong to unconditionally
            // put the first word onto the first line. An empty
            // zero-width word fixed this.
            broken_words.insert(0, core::Word::from(""));
        }
        broken_words
    } else {
        split_words.collect::<Vec<_>>()
    };

    let wrapped_words = options.wrap_algorithm.wrap(&broken_words, &line_widths);

    let mut idx = 0;
    for words in wrapped_words {
        let last_word = match words.last() {
            None => {
                lines.push(Cow::from(""));
                continue;
            }
            Some(word) => word,
        };

        // We assume here that all words are contiguous in `line`.
        // That is, the sum of their lengths should add up to the
        // length of `line`.
        let len = words
            .iter()
            .map(|word| word.len() + word.whitespace.len())
            .sum::<usize>()
            - last_word.whitespace.len();

        // The result is owned if we have indentation, otherwise we
        // can simply borrow an empty string.
        let mut result = if lines.is_empty() && !options.initial_indent.is_empty() {
            Cow::Owned(options.initial_indent.to_owned())
        } else if !lines.is_empty() && !options.subsequent_indent.is_empty() {
            Cow::Owned(options.subsequent_indent.to_owned())
        } else {
            // We can use an empty string here since string
            // concatenation for `Cow` preserves a borrowed value when
            // either side is empty.
            Cow::from("")
        };

        result += &line[idx..idx + len];

        if !last_word.penalty.is_empty() {
            result.to_mut().push_str(last_word.penalty);
        }

        lines.push(result);

        // Advance by the length of `result`, plus the length of
        // `last_word.whitespace` -- even if we had a penalty, we need
        // to skip over the whitespace.
        idx += len + last_word.whitespace.len();
    }
}

/// Wrap text into columns with a given total width.
///
/// The `left_gap`, `middle_gap` and `right_gap` arguments specify the
/// strings to insert before, between, and after the columns. The
/// total width of all columns and all gaps is specified using the
/// `total_width_or_options` argument. This argument can simply be an
/// integer if you want to use default settings when wrapping, or it
/// can be a [`Options`] value if you want to customize the wrapping.
///
/// If the columns are narrow, it is recommended to set
/// [`Options::break_words`] to `true` to prevent words from
/// protruding into the margins.
///
/// The per-column width is computed like this:
///
/// ```
/// # let (left_gap, middle_gap, right_gap) = ("", "", "");
/// # let columns = 2;
/// # let options = textwrap::Options::new(80);
/// let inner_width = options.width
///     - textwrap::core::display_width(left_gap)
///     - textwrap::core::display_width(right_gap)
///     - textwrap::core::display_width(middle_gap) * (columns - 1);
/// let column_width = inner_width / columns;
/// ```
///
/// The `text` is wrapped using [`wrap`] and the given `options`
/// argument, but the width is overwritten to the computed
/// `column_width`.
///
/// # Panics
///
/// Panics if `columns` is zero.
///
/// # Examples
///
/// ```
/// use textwrap::wrap_columns;
///
/// let text = "\
/// This is an example text, which is wrapped into three columns. \
/// Notice how the final column can be shorter than the others.";
///
/// #[cfg(feature = "smawk")]
/// assert_eq!(wrap_columns(text, 3, 50, "| ", " | ", " |"),
///            vec!["| This is       | into three    | column can be  |",
///                 "| an example    | columns.      | shorter than   |",
///                 "| text, which   | Notice how    | the others.    |",
///                 "| is wrapped    | the final     |                |"]);
///
/// // Without the `smawk` feature, the middle column is a little more uneven:
/// #[cfg(not(feature = "smawk"))]
/// assert_eq!(wrap_columns(text, 3, 50, "| ", " | ", " |"),
///            vec!["| This is an    | three         | column can be  |",
///                 "| example text, | columns.      | shorter than   |",
///                 "| which is      | Notice how    | the others.    |",
///                 "| wrapped into  | the final     |                |"]);
pub fn wrap_columns<'a, Opt>(
    text: &str,
    columns: usize,
    total_width_or_options: Opt,
    left_gap: &str,
    middle_gap: &str,
    right_gap: &str,
) -> Vec<String>
where
    Opt: Into<Options<'a>>,
{
    assert!(columns > 0);

    let mut options: Options = total_width_or_options.into();

    let inner_width = options
        .width
        .saturating_sub(core::display_width(left_gap))
        .saturating_sub(core::display_width(right_gap))
        .saturating_sub(core::display_width(middle_gap) * (columns - 1));

    let column_width = std::cmp::max(inner_width / columns, 1);
    options.width = column_width;
    let last_column_padding = " ".repeat(inner_width % column_width);
    let wrapped_lines = wrap(text, options);
    let lines_per_column =
        wrapped_lines.len() / columns + usize::from(wrapped_lines.len() % columns > 0);
    let mut lines = Vec::new();
    for line_no in 0..lines_per_column {
        let mut line = String::from(left_gap);
        for column_no in 0..columns {
            match wrapped_lines.get(line_no + column_no * lines_per_column) {
                Some(column_line) => {
                    line.push_str(column_line);
                    line.push_str(&" ".repeat(column_width - core::display_width(column_line)));
                }
                None => {
                    line.push_str(&" ".repeat(column_width));
                }
            }
            if column_no == columns - 1 {
                line.push_str(&last_column_padding);
            } else {
                line.push_str(middle_gap);
            }
        }
        line.push_str(right_gap);
        lines.push(line);
    }

    lines
}

/// Fill `text` in-place without reallocating the input string.
///
/// This function works by modifying the input string: some `' '`
/// characters will be replaced by `'\n'` characters. The rest of the
/// text remains untouched.
///
/// Since we can only replace existing whitespace in the input with
/// `'\n'` (there is no space for `"\r\n"`), we cannot do hyphenation
/// nor can we split words longer than the line width. We also need to
/// use `AsciiSpace` as the word separator since we need `' '`
/// characters between words in order to replace some of them with a
/// `'\n'`. Indentation is also ruled out. In other words,
/// `fill_inplace(width)` behaves as if you had called [`fill`] with
/// these options:
///
/// ```
/// # use textwrap::{core, LineEnding, Options, WordSplitter, WordSeparator, WrapAlgorithm};
/// # let width = 80;
/// Options::new(width)
///     .break_words(false)
///     .line_ending(LineEnding::LF)
///     .word_separator(WordSeparator::AsciiSpace)
///     .wrap_algorithm(WrapAlgorithm::FirstFit)
///     .word_splitter(WordSplitter::NoHyphenation);
/// ```
///
/// The wrap algorithm is [`WrapAlgorithm::FirstFit`] since this
/// is the fastest algorithm — and the main reason to use
/// `fill_inplace` is to get the string broken into newlines as fast
/// as possible.
///
/// A last difference is that (unlike [`fill`]) `fill_inplace` can
/// leave trailing whitespace on lines. This is because we wrap by
/// inserting a `'\n'` at the final whitespace in the input string:
///
/// ```
/// let mut text = String::from("Hello   World!");
/// textwrap::fill_inplace(&mut text, 10);
/// assert_eq!(text, "Hello  \nWorld!");
/// ```
///
/// If we didn't do this, the word `World!` would end up being
/// indented. You can avoid this if you make sure that your input text
/// has no double spaces.
///
/// # Performance
///
/// In benchmarks, `fill_inplace` is about twice as fast as [`fill`].
/// Please see the [`linear`
/// benchmark](https://github.com/mgeisler/textwrap/blob/master/benchmarks/linear.rs)
/// for details.
pub fn fill_inplace(text: &mut String, width: usize) {
    let mut indices = Vec::new();

    let mut offset = 0;
    for line in text.split('\n') {
        let words = WordSeparator::AsciiSpace
            .find_words(line)
            .collect::<Vec<_>>();
        let wrapped_words = wrap_algorithms::wrap_first_fit(&words, &[width as f64]);

        let mut line_offset = offset;
        for words in &wrapped_words[..wrapped_words.len() - 1] {
            let line_len = words
                .iter()
                .map(|word| word.len() + word.whitespace.len())
                .sum::<usize>();

            line_offset += line_len;
            // We've advanced past all ' ' characters -- want to move
            // one ' ' backwards and insert our '\n' there.
            indices.push(line_offset - 1);
        }

        // Advance past entire line, plus the '\n' which was removed
        // by the split call above.
        offset += line.len() + 1;
    }

    let mut bytes = std::mem::take(text).into_bytes();
    for idx in indices {
        bytes[idx] = b'\n';
    }
    *text = String::from_utf8(bytes).unwrap();
}

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

    #[cfg(feature = "hyphenation")]
    use hyphenation::{Language, Load, Standard};

    #[test]
    fn options_agree_with_usize() {
        let opt_usize = Options::from(42_usize);
        let opt_options = Options::new(42);

        assert_eq!(opt_usize.width, opt_options.width);
        assert_eq!(opt_usize.initial_indent, opt_options.initial_indent);
        assert_eq!(opt_usize.subsequent_indent, opt_options.subsequent_indent);
        assert_eq!(opt_usize.break_words, opt_options.break_words);
        assert_eq!(
            opt_usize.word_splitter.split_points("hello-world"),
            opt_options.word_splitter.split_points("hello-world")
        );
    }

    #[test]
    fn no_wrap() {
        assert_eq!(wrap("foo", 10), vec!["foo"]);
    }

    #[test]
    fn wrap_simple() {
        assert_eq!(wrap("foo bar baz", 5), vec!["foo", "bar", "baz"]);
    }

    #[test]
    fn to_be_or_not() {
        assert_eq!(
            wrap(
                "To be, or not to be, that is the question.",
                Options::new(10).wrap_algorithm(WrapAlgorithm::FirstFit)
            ),
            vec!["To be, or", "not to be,", "that is", "the", "question."]
        );
    }

    #[test]
    fn multiple_words_on_first_line() {
        assert_eq!(wrap("foo bar baz", 10), vec!["foo bar", "baz"]);
    }

    #[test]
    fn long_word() {
        assert_eq!(wrap("foo", 0), vec!["f", "o", "o"]);
    }

    #[test]
    fn long_words() {
        assert_eq!(wrap("foo bar", 0), vec!["f", "o", "o", "b", "a", "r"]);
    }

    #[test]
    fn max_width() {
        assert_eq!(wrap("foo bar", usize::MAX), vec!["foo bar"]);

        let text = "Hello there! This is some English text. \
                    It should not be wrapped given the extents below.";
        assert_eq!(wrap(text, usize::MAX), vec![text]);
    }

    #[test]
    fn leading_whitespace() {
        assert_eq!(wrap("  foo bar", 6), vec!["  foo", "bar"]);
    }

    #[test]
    fn leading_whitespace_empty_first_line() {
        // If there is no space for the first word, the first line
        // will be empty. This is because the string is split into
        // words like [" ", "foobar ", "baz"], which puts "foobar " on
        // the second line. We never output trailing whitespace
        assert_eq!(wrap(" foobar baz", 6), vec!["", "foobar", "baz"]);
    }

    #[test]
    fn trailing_whitespace() {
        // Whitespace is only significant inside a line. After a line
        // gets too long and is broken, the first word starts in
        // column zero and is not indented.
        assert_eq!(wrap("foo     bar     baz  ", 5), vec!["foo", "bar", "baz"]);
    }

    #[test]
    fn issue_99() {
        // We did not reset the in_whitespace flag correctly and did
        // not handle single-character words after a line break.
        assert_eq!(
            wrap("aaabbbccc x yyyzzzwww", 9),
            vec!["aaabbbccc", "x", "yyyzzzwww"]
        );
    }

    #[test]
    fn issue_129() {
        // The dash is an em-dash which takes up four bytes. We used
        // to panic since we tried to index into the character.
        let options = Options::new(1).word_separator(WordSeparator::AsciiSpace);
        assert_eq!(wrap("x – x", options), vec!["x", "–", "x"]);
    }

    #[test]
    fn wide_character_handling() {
        assert_eq!(wrap("Hello, World!", 15), vec!["Hello, World!"]);
        assert_eq!(
            wrap(
                "Ｈｅｌｌｏ, Ｗｏｒｌｄ!",
                Options::new(15).word_separator(WordSeparator::AsciiSpace)
            ),
            vec!["Ｈｅｌｌｏ,", "Ｗｏｒｌｄ!"]
        );

        // Wide characters are allowed to break if the
        // unicode-linebreak feature is enabled.
        #[cfg(feature = "unicode-linebreak")]
        assert_eq!(
            wrap(
                "Ｈｅｌｌｏ, Ｗｏｒｌｄ!",
                Options::new(15).word_separator(WordSeparator::UnicodeBreakProperties),
            ),
            vec!["Ｈｅｌｌｏ, Ｗ", "ｏｒｌｄ!"]
        );
    }

    #[test]
    fn empty_line_is_indented() {
        // Previously, indentation was not applied to empty lines.
        // However, this is somewhat inconsistent and undesirable if
        // the indentation is something like a border ("| ") which you
        // want to apply to all lines, empty or not.
        let options = Options::new(10).initial_indent("!!!");
        assert_eq!(fill("", &options), "!!!");
    }

    #[test]
    fn indent_single_line() {
        let options = Options::new(10).initial_indent(">>>"); // No trailing space
        assert_eq!(fill("foo", &options), ">>>foo");
    }

    #[test]
    fn indent_first_emoji() {
        let options = Options::new(10).initial_indent("����");
        assert_eq!(
            wrap("x x x x x x x x x x x x x", &options),
            vec!["����x x x", "x x x x x", "x x x x x"]
        );
    }

    #[test]
    fn indent_multiple_lines() {
        let options = Options::new(6).initial_indent("* ").subsequent_indent("  ");
        assert_eq!(
            wrap("foo bar baz", &options),
            vec!["* foo", "  bar", "  baz"]
        );
    }

    #[test]
    fn only_initial_indent_multiple_lines() {
        let options = Options::new(10).initial_indent("  ");
        assert_eq!(wrap("foo\nbar\nbaz", &options), vec!["  foo", "bar", "baz"]);
    }

    #[test]
    fn only_subsequent_indent_multiple_lines() {
        let options = Options::new(10).subsequent_indent("  ");
        assert_eq!(
            wrap("foo\nbar\nbaz", &options),
            vec!["foo", "  bar", "  baz"]
        );
    }

    #[test]
    fn indent_break_words() {
        let options = Options::new(5).initial_indent("* ").subsequent_indent("  ");
        assert_eq!(wrap("foobarbaz", &options), vec!["* foo", "  bar", "  baz"]);
    }

    #[test]
    fn initial_indent_break_words() {
        // This is a corner-case showing how the long word is broken
        // according to the width of the subsequent lines. The first
        // fragment of the word no longer fits on the first line,
        // which ends up being pure indentation.
        let options = Options::new(5).initial_indent("-->");
        assert_eq!(wrap("foobarbaz", &options), vec!["-->", "fooba", "rbaz"]);
    }

    #[test]
    fn hyphens() {
        assert_eq!(wrap("foo-bar", 5), vec!["foo-", "bar"]);
    }

    #[test]
    fn trailing_hyphen() {
        let options = Options::new(5).break_words(false);
        assert_eq!(wrap("foobar-", &options), vec!["foobar-"]);
    }

    #[test]
    fn multiple_hyphens() {
        assert_eq!(wrap("foo-bar-baz", 5), vec!["foo-", "bar-", "baz"]);
    }

    #[test]
    fn hyphens_flag() {
        let options = Options::new(5).break_words(false);
        assert_eq!(
            wrap("The --foo-bar flag.", &options),
            vec!["The", "--foo-", "bar", "flag."]
        );
    }

    #[test]
    fn repeated_hyphens() {
        let options = Options::new(4).break_words(false);
        assert_eq!(wrap("foo--bar", &options), vec!["foo--bar"]);
    }

    #[test]
    fn hyphens_alphanumeric() {
        assert_eq!(wrap("Na2-CH4", 5), vec!["Na2-", "CH4"]);
    }

    #[test]
    fn hyphens_non_alphanumeric() {
        let options = Options::new(5).break_words(false);
        assert_eq!(wrap("foo(-)bar", &options), vec!["foo(-)bar"]);
    }

    #[test]
    fn multiple_splits() {
        assert_eq!(wrap("foo-bar-baz", 9), vec!["foo-bar-", "baz"]);
    }

    #[test]
    fn forced_split() {
        let options = Options::new(5).break_words(false);
        assert_eq!(wrap("foobar-baz", &options), vec!["foobar-", "baz"]);
    }

    #[test]
    fn multiple_unbroken_words_issue_193() {
        let options = Options::new(3).break_words(false);
        assert_eq!(
            wrap("small large tiny", &options),
            vec!["small", "large", "tiny"]
        );
        assert_eq!(
            wrap("small  large   tiny", &options),
            vec!["small", "large", "tiny"]
        );
    }

    #[test]
    fn very_narrow_lines_issue_193() {
        let options = Options::new(1).break_words(false);
        assert_eq!(wrap("fooo x y", &options), vec!["fooo", "x", "y"]);
        assert_eq!(wrap("fooo   x     y", &options), vec!["fooo", "x", "y"]);
    }

    #[test]
    fn simple_hyphens() {
        let options = Options::new(8).word_splitter(WordSplitter::HyphenSplitter);
        assert_eq!(wrap("foo bar-baz", &options), vec!["foo bar-", "baz"]);
    }

    #[test]
    fn no_hyphenation() {
        let options = Options::new(8).word_splitter(WordSplitter::NoHyphenation);
        assert_eq!(wrap("foo bar-baz", &options), vec!["foo", "bar-baz"]);
    }

    #[test]
    #[cfg(feature = "hyphenation")]
    fn auto_hyphenation_double_hyphenation() {
        let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
        let options = Options::new(10);
        assert_eq!(
            wrap("Internationalization", &options),
            vec!["Internatio", "nalization"]
        );

        let options = Options::new(10).word_splitter(WordSplitter::Hyphenation(dictionary));
        assert_eq!(
            wrap("Internationalization", &options),
            vec!["Interna-", "tionaliza-", "tion"]
        );
    }

    #[test]
    #[cfg(feature = "hyphenation")]
    fn auto_hyphenation_issue_158() {
        let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
        let options = Options::new(10);
        assert_eq!(
            wrap("participation is the key to success", &options),
            vec!["participat", "ion is", "the key to", "success"]
        );

        let options = Options::new(10).word_splitter(WordSplitter::Hyphenation(dictionary));
        assert_eq!(
            wrap("participation is the key to success", &options),
            vec!["partici-", "pation is", "the key to", "success"]
        );
    }

    #[test]
    #[cfg(feature = "hyphenation")]
    fn split_len_hyphenation() {
        // Test that hyphenation takes the width of the whitespace
        // into account.
        let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
        let options = Options::new(15).word_splitter(WordSplitter::Hyphenation(dictionary));
        assert_eq!(
            wrap("garbage   collection", &options),
            vec!["garbage   col-", "lection"]
        );
    }

    #[test]
    #[cfg(feature = "hyphenation")]
    fn borrowed_lines() {
        // Lines that end with an extra hyphen are owned, the final
        // line is borrowed.
        use std::borrow::Cow::{Borrowed, Owned};
        let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
        let options = Options::new(10).word_splitter(WordSplitter::Hyphenation(dictionary));
        let lines = wrap("Internationalization", &options);
        assert_eq!(lines, vec!["Interna-", "tionaliza-", "tion"]);
        if let Borrowed(s) = lines[0] {
            assert!(false, "should not have been borrowed: {:?}", s);
        }
        if let Borrowed(s) = lines[1] {
            assert!(false, "should not have been borrowed: {:?}", s);
        }
        if let Owned(ref s) = lines[2] {
            assert!(false, "should not have been owned: {:?}", s);
        }
    }

    #[test]
    #[cfg(feature = "hyphenation")]
    fn auto_hyphenation_with_hyphen() {
        let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
        let options = Options::new(8).break_words(false);
        assert_eq!(
            wrap("over-caffinated", &options),
            vec!["over-", "caffinated"]
        );

        let options = options.word_splitter(WordSplitter::Hyphenation(dictionary));
        assert_eq!(
            wrap("over-caffinated", &options),
            vec!["over-", "caffi-", "nated"]
        );
    }

    #[test]
    fn break_words() {
        assert_eq!(wrap("foobarbaz", 3), vec!["foo", "bar", "baz"]);
    }

    #[test]
    fn break_words_wide_characters() {
        // Even the poor man's version of `ch_width` counts these
        // characters as wide.
        let options = Options::new(5).word_separator(WordSeparator::AsciiSpace);
        assert_eq!(wrap("Ｈｅｌｌｏ", options), vec!["Ｈｅ", "ｌｌ", "ｏ"]);
    }

    #[test]
    fn break_words_zero_width() {
        assert_eq!(wrap("foobar", 0), vec!["f", "o", "o", "b", "a", "r"]);
    }

    #[test]
    fn break_long_first_word() {
        assert_eq!(wrap("testx y", 4), vec!["test", "x y"]);
    }

    #[test]
    fn break_words_line_breaks() {
        assert_eq!(fill("ab\ncdefghijkl", 5), "ab\ncdefg\nhijkl");
        assert_eq!(fill("abcdefgh\nijkl", 5), "abcde\nfgh\nijkl");
    }

    #[test]
    fn break_words_empty_lines() {
        assert_eq!(
            fill("foo\nbar", &Options::new(2).break_words(false)),
            "foo\nbar"
        );
    }

    #[test]
    fn preserve_line_breaks() {
        assert_eq!(fill("", 80), "");
        assert_eq!(fill("\n", 80), "\n");
        assert_eq!(fill("\n\n\n", 80), "\n\n\n");
        assert_eq!(fill("test\n", 80), "test\n");
        assert_eq!(fill("test\n\na\n\n", 80), "test\n\na\n\n");
        assert_eq!(
            fill(
                "1 3 5 7\n1 3 5 7",
                Options::new(7).wrap_algorithm(WrapAlgorithm::FirstFit)
            ),
            "1 3 5 7\n1 3 5 7"
        );
        assert_eq!(
            fill(
                "1 3 5 7\n1 3 5 7",
                Options::new(5).wrap_algorithm(WrapAlgorithm::FirstFit)
            ),
            "1 3 5\n7\n1 3 5\n7"
        );
    }

    #[test]
    fn preserve_line_breaks_with_whitespace() {
        assert_eq!(fill("  ", 80), "");
        assert_eq!(fill("  \n  ", 80), "\n");
        assert_eq!(fill("  \n \n  \n ", 80), "\n\n\n");
    }

    #[test]
    fn non_breaking_space() {
        let options = Options::new(5).break_words(false);
        assert_eq!(fill("foo bar baz", &options), "foo bar baz");
    }

    #[test]
    fn non_breaking_hyphen() {
        let options = Options::new(5).break_words(false);
        assert_eq!(fill("foo‑bar‑baz", &options), "foo‑bar‑baz");
    }

    #[test]
    fn fill_simple() {
        assert_eq!(fill("foo bar baz", 10), "foo bar\nbaz");
    }

    #[test]
    fn fill_colored_text() {
        // The words are much longer than 6 bytes, but they remain
        // intact after filling the text.
        let green_hello = "\u{1b}[0m\u{1b}[32mHello\u{1b}[0m";
        let blue_world = "\u{1b}[0m\u{1b}[34mWorld!\u{1b}[0m";
        assert_eq!(
            fill(&(String::from(green_hello) + " " + blue_world), 6),
            String::from(green_hello) + "\n" + blue_world
        );
    }

    #[test]
    fn fill_unicode_boundary() {
        // https://github.com/mgeisler/textwrap/issues/390
        fill("\u{1b}!Ͽ", 10);
    }

    #[test]
    fn fill_inplace_empty() {
        let mut text = String::from("");
        fill_inplace(&mut text, 80);
        assert_eq!(text, "");
    }

    #[test]
    fn fill_inplace_simple() {
        let mut text = String::from("foo bar baz");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "foo bar\nbaz");
    }

    #[test]
    fn fill_inplace_multiple_lines() {
        let mut text = String::from("Some text to wrap over multiple lines");
        fill_inplace(&mut text, 12);
        assert_eq!(text, "Some text to\nwrap over\nmultiple\nlines");
    }

    #[test]
    fn fill_inplace_long_word() {
        let mut text = String::from("Internationalization is hard");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "Internationalization\nis hard");
    }

    #[test]
    fn fill_inplace_no_hyphen_splitting() {
        let mut text = String::from("A well-chosen example");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "A\nwell-chosen\nexample");
    }

    #[test]
    fn fill_inplace_newlines() {
        let mut text = String::from("foo bar\n\nbaz\n\n\n");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "foo bar\n\nbaz\n\n\n");
    }

    #[test]
    fn fill_inplace_newlines_reset_line_width() {
        let mut text = String::from("1 3 5\n1 3 5 7 9\n1 3 5 7 9 1 3");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "1 3 5\n1 3 5 7 9\n1 3 5 7 9\n1 3");
    }

    #[test]
    fn fill_inplace_leading_whitespace() {
        let mut text = String::from("  foo bar baz");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "  foo bar\nbaz");
    }

    #[test]
    fn fill_inplace_trailing_whitespace() {
        let mut text = String::from("foo bar baz  ");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "foo bar\nbaz  ");
    }

    #[test]
    fn fill_inplace_interior_whitespace() {
        // To avoid an unwanted indentation of "baz", it is important
        // to replace the final ' ' with '\n'.
        let mut text = String::from("foo  bar    baz");
        fill_inplace(&mut text, 10);
        assert_eq!(text, "foo  bar   \nbaz");
    }

    #[test]
    fn unfill_simple() {
        let (text, options) = unfill("foo\nbar");
        assert_eq!(text, "foo bar");
        assert_eq!(options.width, 3);
        assert_eq!(options.line_ending, LineEnding::LF);
    }

    #[test]
    fn unfill_no_new_line() {
        let (text, options) = unfill("foo bar");
        assert_eq!(text, "foo bar");
        assert_eq!(options.width, 7);
        assert_eq!(options.line_ending, LineEnding::LF);
    }

    #[test]
    fn unfill_simple_crlf() {
        let (text, options) = unfill("foo\r\nbar");
        assert_eq!(text, "foo bar");
        assert_eq!(options.width, 3);
        assert_eq!(options.line_ending, LineEnding::CRLF);
    }

    #[test]
    fn unfill_mixed_new_lines() {
        let (text, options) = unfill("foo\r\nbar\nbaz");
        assert_eq!(text, "foo bar baz");
        assert_eq!(options.width, 3);
        assert_eq!(options.line_ending, LineEnding::LF);
    }

    #[test]
    fn unfill_trailing_newlines() {
        let (text, options) = unfill("foo\nbar\n\n\n");
        assert_eq!(text, "foo bar\n");
        assert_eq!(options.width, 3);
    }

    #[test]
    fn unfill_mixed_trailing_newlines() {
        let (text, options) = unfill("foo\r\nbar\n\r\n\n");
        assert_eq!(text, "foo bar\n");
        assert_eq!(options.width, 3);
        assert_eq!(options.line_ending, LineEnding::LF);
    }

    #[test]
    fn unfill_trailing_crlf() {
        let (text, options) = unfill("foo bar\r\n");
        assert_eq!(text, "foo bar\r\n");
        assert_eq!(options.width, 7);
        assert_eq!(options.line_ending, LineEnding::CRLF);
    }

    #[test]
    fn unfill_initial_indent() {
        let (text, options) = unfill("  foo\nbar\nbaz");
        assert_eq!(text, "foo bar baz");
        assert_eq!(options.width, 5);
        assert_eq!(options.initial_indent, "  ");
    }

    #[test]
    fn unfill_differing_indents() {
        let (text, options) = unfill("  foo\n    bar\n  baz");
        assert_eq!(text, "foo   bar baz");
        assert_eq!(options.width, 7);
        assert_eq!(options.initial_indent, "  ");
        assert_eq!(options.subsequent_indent, "  ");
    }

    #[test]
    fn unfill_list_item() {
        let (text, options) = unfill("* foo\n  bar\n  baz");
        assert_eq!(text, "foo bar baz");
        assert_eq!(options.width, 5);
        assert_eq!(options.initial_indent, "* ");
        assert_eq!(options.subsequent_indent, "  ");
    }

    #[test]
    fn unfill_multiple_char_prefix() {
        let (text, options) = unfill("    // foo bar\n    // baz\n    // quux");
        assert_eq!(text, "foo bar baz quux");
        assert_eq!(options.width, 14);
        assert_eq!(options.initial_indent, "    // ");
        assert_eq!(options.subsequent_indent, "    // ");
    }

    #[test]
    fn unfill_block_quote() {
        let (text, options) = unfill("> foo\n> bar\n> baz");
        assert_eq!(text, "foo bar baz");
        assert_eq!(options.width, 5);
        assert_eq!(options.initial_indent, "> ");
        assert_eq!(options.subsequent_indent, "> ");
    }

    #[test]
    fn unfill_only_prefixes_issue_466() {
        // Test that we don't crash if the first line has only prefix
        // chars *and* the second line is shorter than the first line.
        let (text, options) = unfill("######\nfoo");
        assert_eq!(text, " foo");
        assert_eq!(options.width, 6);
        assert_eq!(options.initial_indent, "######");
        assert_eq!(options.subsequent_indent, "");
    }

    #[test]
    fn unfill_trailing_newlines_issue_466() {
        // Test that we don't crash on a '\r' following a string of
        // '\n'. The problem was that we removed both kinds of
        // characters in one code path, but not in the other.
        let (text, options) = unfill("foo\n##\n\n\r");
        // The \n\n changes subsequent_indent to "".
        assert_eq!(text, "foo ## \r");
        assert_eq!(options.width, 3);
        assert_eq!(options.initial_indent, "");
        assert_eq!(options.subsequent_indent, "");
    }

    #[test]
    fn unfill_whitespace() {
        assert_eq!(unfill("foo   bar").0, "foo   bar");
    }

    #[test]
    fn refill_convert_lf_to_crlf() {
        let options = Options::new(5).line_ending(LineEnding::CRLF);
        assert_eq!(refill("foo\nbar\n", options), "foo\r\nbar\r\n",);
    }

    #[test]
    fn refill_convert_crlf_to_lf() {
        let options = Options::new(5).line_ending(LineEnding::LF);
        assert_eq!(refill("foo\r\nbar\r\n", options), "foo\nbar\n",);
    }

    #[test]
    fn refill_convert_mixed_newlines() {
        let options = Options::new(5).line_ending(LineEnding::CRLF);
        assert_eq!(refill("foo\r\nbar\n", options), "foo\r\nbar\r\n",);
    }

    #[test]
    fn refill_defaults_to_lf() {
        assert_eq!(refill("foo bar baz", 5), "foo\nbar\nbaz");
    }

    #[test]
    fn wrap_columns_empty_text() {
        assert_eq!(wrap_columns("", 1, 10, "| ", "", " |"), vec!["|        |"]);
    }

    #[test]
    fn wrap_columns_single_column() {
        assert_eq!(
            wrap_columns("Foo", 3, 30, "| ", " | ", " |"),
            vec!["| Foo    |        |          |"]
        );
    }

    #[test]
    fn wrap_columns_uneven_columns() {
        // The gaps take up a total of 5 columns, so the columns are
        // (21 - 5)/4 = 4 columns wide:
        assert_eq!(
            wrap_columns("Foo Bar Baz Quux", 4, 21, "|", "|", "|"),
            vec!["|Foo |Bar |Baz |Quux|"]
        );
        // As the total width increases, the last column absorbs the
        // excess width:
        assert_eq!(
            wrap_columns("Foo Bar Baz Quux", 4, 24, "|", "|", "|"),
            vec!["|Foo |Bar |Baz |Quux   |"]
        );
        // Finally, when the width is 25, the columns can be resized
        // to a width of (25 - 5)/4 = 5 columns:
        assert_eq!(
            wrap_columns("Foo Bar Baz Quux", 4, 25, "|", "|", "|"),
            vec!["|Foo  |Bar  |Baz  |Quux |"]
        );
    }

    #[test]
    #[cfg(feature = "unicode-width")]
    fn wrap_columns_with_emojis() {
        assert_eq!(
            wrap_columns(
                "Words and a few emojis �� wrapped in ⓶ columns",
                2,
                30,
                "✨ ",
                " ⚽ ",
                " ��"
            ),
            vec![
                "✨ Words      ⚽ wrapped in ��",
                "✨ and a few  ⚽ ⓶ columns  ��",
                "✨ emojis ��  ⚽            ��"
            ]
        );
    }

    #[test]
    fn wrap_columns_big_gaps() {
        // The column width shrinks to 1 because the gaps take up all
        // the space.
        assert_eq!(
            wrap_columns("xyz", 2, 10, "----> ", " !!! ", " <----"),
            vec![
                "----> x !!! z <----", //
                "----> y !!!   <----"
            ]
        );
    }

    #[test]
    #[should_panic]
    fn wrap_columns_panic_with_zero_columns() {
        wrap_columns("", 0, 10, "", "", "");
    }
}