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    //! This is a library for controlling colours and formatting, such as
    //! red bold text or blue underlined text, on ANSI terminals.
    //!
    //!
    //! ## Basic usage
    //!
    //! There are two main data structures in this crate that you need to be
    //! concerned with: `ANSIString` and `Style`. A `Style` holds stylistic
    //! information: colours, whether the text should be bold, or blinking, or
    //! whatever. There are also `Colour` variants that represent simple foreground
    //! colour styles. An `ANSIString` is a string paired with a `Style`.
    //!
    //! (Yes, it’s British English, but you won’t have to write “colour” very often.
    //! `Style` is used the majority of the time.)
    //!
    //! To format a string, call the `paint` method on a `Style` or a `Colour`,
    //! passing in the string you want to format as the argument. For example,
    //! here’s how to get some red text:
    //!
    //!     use ansi_term::Colour::Red;
    //!     println!("This is in red: {}", Red.paint("a red string"));
    //!
    //! It’s important to note that the `paint` method does *not* actually return a
    //! string with the ANSI control characters surrounding it. Instead, it returns
    //! an `ANSIString` value that has a `Display` implementation that, when
    //! formatted, returns the characters. This allows strings to be printed with a
    //! minimum of `String` allocations being performed behind the scenes.
    //!
    //! If you *do* want to get at the escape codes, then you can convert the
    //! `ANSIString` to a string as you would any other `Display` value:
    //!
    //!     use ansi_term::Colour::Red;
    //!     use std::string::ToString;
    //!     let red_string = Red.paint("a red string").to_string();
    //!
    //!
    //! ## Bold, underline, background, and other styles
    //!
    //! For anything more complex than plain foreground colour changes, you need to
    //! construct `Style` objects themselves, rather than beginning with a `Colour`.
    //! You can do this by chaining methods based on a new `Style`, created with
    //! `Style::new()`. Each method creates a new style that has that specific
    //! property set. For example:
    //!
    //!     use ansi_term::Style;
    //!     println!("How about some {} and {}?",
    //!              Style::new().bold().paint("bold"),
    //!              Style::new().underline().paint("underline"));
    //!
    //! For brevity, these methods have also been implemented for `Colour` values,
    //! so you can give your styles a foreground colour without having to begin with
    //! an empty `Style` value:
    //!
    //!     use ansi_term::Colour::{Blue, Yellow};
    //!     println!("Demonstrating {} and {}!",
    //!              Blue.bold().paint("blue bold"),
    //!              Yellow.underline().paint("yellow underline"));
    //!     println!("Yellow on blue: {}", Yellow.on(Blue).paint("wow!"));
    //!
    //! The complete list of styles you can use are: `bold`, `dimmed`, `italic`,
    //! `underline`, `blink`, `reverse`, `hidden`, and `on` for background colours.
    //!
    //! Finally, you can turn a `Colour` into a `Style` with the `normal` method.
    //! This will produce the exact same `ANSIString` as if you just used the
    //! `paint` method on the `Colour` directly, but it’s useful in certain cases:
    //! for example, you may have a method that returns `Styles`, and need to
    //! represent both the “red bold” and “red, but not bold” styles with values of
    //! the same type. The `Style` struct also has a `Default` implementation if you
    //! want to have a style with *nothing* set.
    //!
    //!     use ansi_term::Style;
    //!     use ansi_term::Colour::Red;
    //!     Red.normal().paint("yet another red string");
    //!     Style::default().paint("a completely regular string");
    //!
    //!
    //! ## Extended colours
    //!
    //! You can access the extended range of 256 colours by using the `Fixed` colour
    //! variant, which takes an argument of the colour number to use. This can be
    //! included wherever you would use a `Colour`:
    //!
    //!     use ansi_term::Colour::Fixed;
    //!     Fixed(134).paint("A sort of light purple");
    //!     Fixed(221).on(Fixed(124)).paint("Mustard in the ketchup");
    //!
    //! The first sixteen of these values are the same as the normal and bold
    //! standard colour variants. There’s nothing stopping you from using these as
    //! `Fixed` colours instead, but there’s nothing to be gained by doing so
    //! either.
    //!
    //!
    //! ## Combining successive coloured strings
    //!
    //! The benefit of writing ANSI escape codes to the terminal is that they
    //! *stack*: you do not need to end every coloured string with a reset code if
    //! the text that follows it is of a similar style. For example, if you want to
    //! have some blue text followed by some blue bold text, it’s possible to send
    //! the ANSI code for blue, followed by the ANSI code for bold, and finishing
    //! with a reset code without having to have an extra one between the two
    //! strings.
    //!
    //! This crate can optimise the ANSI codes that get printed in situations like
    //! this, making life easier for your terminal renderer. The `ANSIStrings`
    //! struct takes a slice of several `ANSIString` values, and will iterate over
    //! each of them, printing only the codes for the styles that need to be updated
    //! as part of its formatting routine.
    //!
    //! The following code snippet uses this to enclose a binary number displayed in
    //! red bold text inside some red, but not bold, brackets:
    //!
    //!     use ansi_term::Colour::Red;
    //!     use ansi_term::{ANSIString, ANSIStrings};
    //!     let some_value = format!("{:b}", 42);
    //!     let strings: &[ANSIString<'static>] = &[
    //!         Red.paint("["),
    //!         Red.bold().paint(some_value),
    //!         Red.paint("]"),
    //!     ];
    //!     println!("Value: {}", ANSIStrings(strings));
    //!
    //! There are several things to note here. Firstly, the `paint` method can take
    //! *either* an owned `String` or a borrowed `&str`. Internally, an `ANSIString`
    //! holds a copy-on-write (`Cow`) string value to deal with both owned and
    //! borrowed strings at the same time. This is used here to display a `String`,
    //! the result of the `format!` call, using the same mechanism as some
    //! statically-available `&str` slices. Secondly, that the `ANSIStrings` value
    //! works in the same way as its singular counterpart, with a `Display`
    //! implementation that only performs the formatting when required.

    #![crate_name = "ansi_term"]
    #![crate_type = "rlib"]
    #![crate_type = "dylib"]

    #![warn(missing_copy_implementations)]
    #![warn(missing_docs)]
    #![warn(trivial_casts, trivial_numeric_casts)]
    #![warn(unused_extern_crates, unused_qualifications)]

    use std::borrow::Cow;
    use std::default::Default;
    use std::fmt;
    use std::ops::Deref;

    use Colour::*;
    use Difference::*;

    /// An ANSI String is a string coupled with the Style to display it
    /// in a terminal.
    ///
    /// Although not technically a string itself, it can be turned into
    /// one with the `to_string` method.
    ///
    /// ### Examples
    ///
    /// ```no_run
    /// use ansi_term::ANSIString;
    /// use ansi_term::Colour::Red;
    ///
    /// let red_string = Red.paint("a red string");
    /// println!("{}", red_string);
    /// ```
    ///
    /// ```
    /// use ansi_term::ANSIString;
    ///
    /// let plain_string = ANSIString::from("a plain string");
    /// assert_eq!(&*plain_string, "a plain string");
    /// ```
    #[derive(PartialEq, Debug, Clone)]
    pub struct ANSIString<'a> {
        string: Cow<'a, str>,
        style: Style,
    }

    impl<'a> fmt::Display for ANSIString<'a> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            try!(self.style.write_prefix(f));
            try!(write!(f, "{}", self.string));
            self.style.write_suffix(f)
        }
    }

    impl<'a, S> From<S> for ANSIString<'a>
    where S: Into<Cow<'a, str>> {
        fn from(input: S) -> ANSIString<'a> {
            ANSIString {
                string: input.into(),
                style:  Style::default(),
            }
        }
    }

    impl<'a> Deref for ANSIString<'a> {
        type Target = str;

        fn deref(&self) -> &str {
            self.string.deref()
        }
    }

    /// A colour is one specific type of ANSI escape code, and can refer
    /// to either the foreground or background colour.
    ///
    /// These use the standard numeric sequences.
    /// See http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
    #[derive(PartialEq, Clone, Copy, Debug)]
    pub enum Colour {

        /// Colour #0 (foreground code `30`, background code `40`).
        ///
        /// This is not necessarily the background colour, and using it as one may
        /// render the text hard to read on terminals with dark backgrounds.
        Black,

        /// Colour #1 (foreground code `31`, background code `41`).
        Red,

        /// Colour #2 (foreground code `32`, background code `42`).
        Green,

        /// Colour #3 (foreground code `33`, background code `43`).
        Yellow,

        /// Colour #4 (foreground code `34`, background code `44`).
        Blue,

        /// Colour #5 (foreground code `35`, background code `45`).
        Purple,

        /// Colour #6 (foreground code `36`, background code `46`).
        Cyan,

        /// Colour #7 (foreground code `37`, background code `47`).
        ///
        /// As above, this is not necessarily the foreground colour, and may be
        /// hard to read on terminals with light backgrounds.
        White,

        /// A colour number from 0 to 255, for use in 256-colour terminal
        /// environments.
        ///
        /// - Colours 0 to 7 are the `Black` to `White` variants respectively.
        ///   These colours can usually be changed in the terminal emulator.
        /// - Colours 8 to 15 are brighter versions of the eight colours above.
        ///   These can also usually be changed in the terminal emulator, or it
        ///   could be configured to use the original colours and show the text in
        ///   bold instead. It varies depending on the program.
        /// - Colours 16 to 231 contain several palettes of bright colours,
        ///   arranged in six squares measuring six by six each.
        /// - Colours 232 to 255 are shades of grey from black to white.
        ///
        /// It might make more sense to look at a [colour chart](^cc).
        /// [^cc]: https://upload.wikimedia.org/wikipedia/en/1/15/Xterm_256color_chart.svg
        Fixed(u8),
    }

    // I'm not beyond calling Colour Colour, rather than Color, but I did
    // purposefully name this crate 'ansi-term' so people wouldn't get
    // confused when they tried to install it.
    //
    // Only *after* they'd installed it.

    impl Colour {
        fn write_foreground_code(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                Black      => write!(f, "30"),
                Red        => write!(f, "31"),
                Green      => write!(f, "32"),
                Yellow     => write!(f, "33"),
                Blue       => write!(f, "34"),
                Purple     => write!(f, "35"),
                Cyan       => write!(f, "36"),
                White      => write!(f, "37"),
                Fixed(num) => write!(f, "38;5;{}", &num),
            }
        }

        fn write_background_code(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                Black      => write!(f, "40"),
                Red        => write!(f, "41"),
                Green      => write!(f, "42"),
                Yellow     => write!(f, "43"),
                Blue       => write!(f, "44"),
                Purple     => write!(f, "45"),
                Cyan       => write!(f, "46"),
                White      => write!(f, "47"),
                Fixed(num) => write!(f, "48;5;{}", &num),
            }
        }

        /// Return a Style with the foreground colour set to this colour.
        pub fn normal(self) -> Style {
            Style { foreground: Some(self), .. Style::default() }
        }

        /// Paints the given text with this colour, returning an ANSI string.
        /// This is a short-cut so you don't have to use Blue.normal() just
        /// to get blue text.
        pub fn paint<'a, S>(self, input: S) -> ANSIString<'a>
        where S: Into<Cow<'a, str>> {
            ANSIString {
                string: input.into(),
                style:  self.normal(),
            }
        }

        /// Returns a Style with the bold property set.
        pub fn bold(self) -> Style {
            Style { foreground: Some(self), is_bold: true, .. Style::default() }
        }

        /// Returns a Style with the dimmed property set.
        pub fn dimmed(self) -> Style {
            Style { foreground: Some(self), is_dimmed: true, .. Style::default() }
        }

        /// Returns a Style with the italic property set.
        pub fn italic(self) -> Style {
            Style { foreground: Some(self), is_italic: true, .. Style::default() }
        }

        /// Returns a Style with the underline property set.
        pub fn underline(self) -> Style {
            Style { foreground: Some(self), is_underline: true, .. Style::default() }
        }

        /// Returns a Style with the blink property set.
        pub fn blink(self) -> Style {
            Style { foreground: Some(self), is_blink: true, .. Style::default() }
        }

        /// Returns a Style with the reverse property set.
        pub fn reverse(self) -> Style {
            Style { foreground: Some(self), is_reverse: true, .. Style::default() }
        }

        /// Returns a Style with the hidden property set.
        pub fn hidden(self) -> Style {
            Style { foreground: Some(self), is_hidden: true, .. Style::default() }
        }

        /// Returns a Style with the background colour property set.
        pub fn on(self, background: Colour) -> Style {
            Style { foreground: Some(self), background: Some(background), .. Style::default() }
        }
    }

    /// A style is a collection of properties that can format a string
    /// using ANSI escape codes.
    #[derive(PartialEq, Clone, Copy, Debug)]
    pub struct Style {
        foreground: Option<Colour>,
        background: Option<Colour>,
        is_bold: bool,
        is_dimmed: bool,
        is_italic: bool,
        is_underline: bool,
        is_blink: bool,
        is_reverse: bool,
        is_hidden: bool
    }

    impl Style {
        /// Creates a new Style with no differences.
        pub fn new() -> Style {
            Style::default()
        }

        /// Paints the given text with this colour, returning an ANSI string.
        pub fn paint<'a, S>(self, input: S) -> ANSIString<'a>
        where S: Into<Cow<'a, str>> {
            ANSIString {
                string: input.into(),
                style:  self,
            }
        }

        /// Returns a Style with the bold property set.
        pub fn bold(&self) -> Style {
            Style { is_bold: true, .. *self }
        }

        /// Returns a Style with the dimmed property set.
        pub fn dimmed(&self) -> Style {
            Style { is_dimmed: true, .. *self }
        }

        /// Returns a Style with the italic property set.
        pub fn italic(&self) -> Style {
            Style { is_italic: true, .. *self }
        }

        /// Returns a Style with the underline property set.
        pub fn underline(&self) -> Style {
            Style { is_underline: true, .. *self }
        }

        /// Returns a Style with the blink property set.
        pub fn blink(&self) -> Style {
            Style { is_blink: true, .. *self }
        }

        /// Returns a Style with the reverse property set.
        pub fn reverse(&self) -> Style {
            Style { is_reverse: true, .. *self }
        }

        /// Returns a Style with the hidden property set.
        pub fn hidden(&self) -> Style {
            Style { is_hidden: true, .. *self }
        }

        /// Returns a Style with the background colour property set.
        pub fn on(&self, background: Colour) -> Style {
            Style { background: Some(background), .. *self }
        }

        /// Write any ANSI codes that go *before* a piece of text. These should be
        /// the codes to set the terminal to a different colour or font style.
        fn write_prefix(&self, f: &mut fmt::Formatter) -> fmt::Result {
            use std::fmt::Write;

            // If there are actually no styles here, then don’t write *any* codes
            // as the prefix. An empty ANSI code may not affect the terminal
            // output at all, but a user may just want a code-free string.
            if self.is_plain() {
                return Ok(());
            }

            // Write the codes’ prefix, then write numbers, separated by
            // semicolons, for each text style we want to apply.
            try!(write!(f, "\x1B["));
            let mut written_anything = false;

            {
                let mut write_char = |c| {
                    if written_anything { try!(f.write_char(';')); }
                    written_anything = true;
                    try!(f.write_char(c));
                    Ok(())
                };

                if self.is_bold       { try!(write_char('1')); }
                if self.is_dimmed     { try!(write_char('2')); }
                if self.is_italic     { try!(write_char('3')); }
                if self.is_underline  { try!(write_char('4')); }
                if self.is_blink      { try!(write_char('5')); }
                if self.is_reverse    { try!(write_char('6')); }
                if self.is_hidden     { try!(write_char('7')); }
            }

            // The foreground and background colours, if specified, need to be
            // handled specially because the number codes are more complicated.
            // (see `write_background_code` and `write_foreground_code`)
            if let Some(bg) = self.background {
                if written_anything { try!(f.write_char(';')); }
                written_anything = true;

                try!(bg.write_background_code(f));
            }

            if let Some(fg) = self.foreground {
                if written_anything { try!(f.write_char(';')); }

                try!(fg.write_foreground_code(f));
            }

            // All the codes end with an `m`, because reasons.
            try!(f.write_char('m'));
            Ok(())
        }

        /// Write any ANSI codes that go *after* a piece of text. These should be
        /// the codes to *reset* the terminal back to its normal colour and style.
        fn write_suffix(&self, f: &mut fmt::Formatter) -> fmt::Result {
            if self.is_plain() {
                Ok(())
            }
            else {
                write!(f, "\x1B[0m")
            }
        }

        /// Compute the 'style difference' required to turn an existing style into
        /// the given, second style.
        ///
        /// For example, to turn green text into green bold text, it's redundant
        /// to write a reset command then a second green+bold command, instead of
        /// just writing one bold command. This method should see that both styles
        /// use the foreground colour green, and reduce it to a single command.
        ///
        /// This method returns an enum value because it's not actually always
        /// possible to turn one style into another: for example, text could be
        /// made bold and underlined, but you can't remove the bold property
        /// without also removing the underline property. So when this has to
        /// happen, this function returns None, meaning that the entire set of
        /// styles should be reset and begun again.
        fn difference(&self, next: &Style) -> Difference {
            // XXX(Havvy): This algorithm is kind of hard to replicate without
            // having the Plain/Foreground enum variants, so I'm just leaving
            // it commented out for now, and defaulting to Reset.

            if self == next {
                return NoDifference;
            }

            // Cannot un-bold, so must Reset.
            if self.is_bold && !next.is_bold {
                return Reset;
            }

            if self.is_dimmed && !next.is_dimmed {
                return Reset;
            }

            if self.is_italic && !next.is_italic {
                return Reset;
            }

            // Cannot un-underline, so must Reset.
            if self.is_underline && !next.is_underline {
                return Reset;
            }

            if self.is_blink && !next.is_blink {
                return Reset;
            }

            if self.is_reverse && !next.is_reverse {
                return Reset;
            }

            if self.is_hidden && !next.is_hidden {
                return Reset;
            }

            // Cannot go from foreground to no foreground, so must Reset.
            if self.foreground.is_some() && next.foreground.is_none() {
                return Reset;
            }

            // Cannot go from background to no background, so must Reset.
            if self.background.is_some() && next.background.is_none() {
                return Reset;
            }

            let mut extra_styles = Style::default();

            if self.is_bold != next.is_bold {
                extra_styles.is_bold = true;
            }

            if self.is_dimmed != next.is_dimmed {
                extra_styles.is_dimmed = true;
            }

            if self.is_italic != next.is_italic {
                extra_styles.is_italic = true;
            }

            if self.is_underline != next.is_underline {
                extra_styles.is_underline = true;
            }

            if self.is_blink != next.is_blink {
                extra_styles.is_blink = true;
            }

            if self.is_reverse != next.is_reverse {
                extra_styles.is_reverse = true;
            }

            if self.is_hidden != next.is_hidden {
                extra_styles.is_hidden = true;
            }

            if self.foreground != next.foreground {
                extra_styles.foreground = next.foreground;
            }

            if self.background != next.background {
                extra_styles.background = next.background;
            }

            ExtraStyles(extra_styles)
        }

        /// Return true if this `Style` has no actual styles, and can be written
        /// without any control characters.
        fn is_plain(self) -> bool {
            self == Style::default()
        }
    }

    impl Default for Style {
        fn default() -> Style {
            Style {
                foreground: None,
                background: None,
                is_bold: false,
                is_dimmed: false,
                is_italic: false,
                is_underline: false,
                is_blink: false,
                is_reverse: false,
                is_hidden: false
            }
        }
    }

    /// When printing out one coloured string followed by another, use one of
    /// these rules to figure out which *extra* control codes need to be sent.
    #[derive(PartialEq, Clone, Copy, Debug)]
    enum Difference {

        /// Print out the control codes specified by this style to end up looking
        /// like the second string's styles.
        ExtraStyles(Style),

        /// Converting between these two is impossible, so just send a reset
        /// command and then the second string's styles.
        Reset,

        /// The before style is exactly the same as the after style, so no further
        /// control codes need to be printed.
        NoDifference,
    }

    /// A set of `ANSIString`s collected together, in order to be written with a
    /// minimum of control characters.
    pub struct ANSIStrings<'a>(pub &'a [ANSIString<'a>]);

    impl<'a> fmt::Display for ANSIStrings<'a> {
    	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    	    let first = match self.0.first() {
    	        None => return Ok(()),
    	        Some(f) => f,
    	    };

            try!(first.style.write_prefix(f));
    	    try!(write!(f, "{}", first.string));

    	    for window in self.0.windows(2) {
    	        match window[0].style.difference(&window[1].style) {
    	            ExtraStyles(style) => try!(style.write_prefix(f)),
    	            Reset => {
                        try!(f.write_str("\x1B[0m"));
                        try!(window[1].style.write_prefix(f));
    	            },
    	            NoDifference => { /* Do nothing! */ },
    	        }

                try!(write!(f, "{}", window[1].string));
    	    }

            // Write the final reset string after all of the ANSIStrings have been
            // written, *except* if the last one has no styles, because it would
            // have already been written by this point.
            if let Some(last) = self.0.last() {
                if !last.style.is_plain() {
                    try!(f.write_str("\x1B[0m"));
                }
            }

    	    Ok(())
    	}
    }

    #[cfg(test)]
    mod tests {
        pub use super::{Style, ANSIStrings};
        pub use super::Colour::*;

        macro_rules! test {
            ($name: ident: $style: expr; $input: expr => $result: expr) => {
                #[test]
                fn $name() {
                    assert_eq!($style.paint($input).to_string(), $result.to_string())
                }
            };
        }

        test!(plain:                 Style::default();                  "text/plain" => "text/plain");
        test!(red:                   Red;                               "hi" => "\x1B[31mhi\x1B[0m");
        test!(black:                 Black.normal();                    "hi" => "\x1B[30mhi\x1B[0m");
        test!(yellow_bold:           Yellow.bold();                     "hi" => "\x1B[1;33mhi\x1B[0m");
        test!(yellow_bold_2:         Yellow.normal().bold();            "hi" => "\x1B[1;33mhi\x1B[0m");
        test!(blue_underline:        Blue.underline();                  "hi" => "\x1B[4;34mhi\x1B[0m");
        test!(green_bold_ul:         Green.bold().underline();          "hi" => "\x1B[1;4;32mhi\x1B[0m");
        test!(green_bold_ul_2:       Green.underline().bold();          "hi" => "\x1B[1;4;32mhi\x1B[0m");
        test!(purple_on_white:       Purple.on(White);                  "hi" => "\x1B[47;35mhi\x1B[0m");
        test!(purple_on_white_2:     Purple.normal().on(White);         "hi" => "\x1B[47;35mhi\x1B[0m");
        test!(cyan_bold_on_white:    Cyan.bold().on(White);             "hi" => "\x1B[1;47;36mhi\x1B[0m");
        test!(cyan_ul_on_white:      Cyan.underline().on(White);        "hi" => "\x1B[4;47;36mhi\x1B[0m");
        test!(cyan_bold_ul_on_white: Cyan.bold().underline().on(White); "hi" => "\x1B[1;4;47;36mhi\x1B[0m");
        test!(cyan_ul_bold_on_white: Cyan.underline().bold().on(White); "hi" => "\x1B[1;4;47;36mhi\x1B[0m");
        test!(fixed:                 Fixed(100);                        "hi" => "\x1B[38;5;100mhi\x1B[0m");
        test!(fixed_on_purple:       Fixed(100).on(Purple);             "hi" => "\x1B[45;38;5;100mhi\x1B[0m");
        test!(fixed_on_fixed:        Fixed(100).on(Fixed(200));         "hi" => "\x1B[48;5;200;38;5;100mhi\x1B[0m");
        test!(bold:                  Style::new().bold();               "hi" => "\x1B[1mhi\x1B[0m");
        test!(underline:             Style::new().underline();          "hi" => "\x1B[4mhi\x1B[0m");
        test!(bunderline:            Style::new().bold().underline();   "hi" => "\x1B[1;4mhi\x1B[0m");
        test!(dimmed:                Style::new().dimmed();             "hi" => "\x1B[2mhi\x1B[0m");
        test!(italic:                Style::new().italic();             "hi" => "\x1B[3mhi\x1B[0m");
        test!(blink:                 Style::new().blink();              "hi" => "\x1B[5mhi\x1B[0m");
        test!(reverse:               Style::new().reverse();            "hi" => "\x1B[6mhi\x1B[0m");
        test!(hidden:                Style::new().hidden();             "hi" => "\x1B[7mhi\x1B[0m");

        mod difference {
            use super::*;
            use super::super::Difference::*;

            #[test]
            fn diff() {
                let expected = ExtraStyles(Style::new().bold());
                let got = Green.normal().difference(&Green.bold());
                assert_eq!(expected, got)
            }

            #[test]
            fn dlb() {
                let got = Green.bold().difference(&Green.normal());
                assert_eq!(Reset, got)
            }

            #[test]
            fn nothing() {
                assert_eq!(NoDifference, Green.bold().difference(&Green.bold()));
            }

            #[test]
            fn nothing_2() {
                assert_eq!(NoDifference, Green.normal().difference(&Green.normal()));
            }

            #[test]
            fn colour_change() {
                assert_eq!(ExtraStyles(Blue.normal()), Red.normal().difference(&Blue.normal()))
            }

            #[test]
            fn removal_of_dimmed() {
                let dimmed = Style::new().dimmed();
                let normal = Style::default();

                assert_eq!(Reset, dimmed.difference(&normal));
            }

            #[test]
            fn addition_of_dimmed() {
                let dimmed = Style::new().dimmed();
                let normal = Style::default();
                let extra_styles = ExtraStyles(dimmed);

                assert_eq!(extra_styles, normal.difference(&dimmed));
            }

            #[test]
            fn removal_of_blink() {
                let blink = Style::new().blink();
                let normal = Style::default();

                assert_eq!(Reset, blink.difference(&normal));
            }

            #[test]
            fn addition_of_blink() {
                let blink = Style::new().blink();
                let normal = Style::default();
                let extra_styles = ExtraStyles(blink);

                assert_eq!(extra_styles, normal.difference(&blink));
            }

            #[test]
            fn removal_of_reverse() {
                let reverse = Style::new().reverse();
                let normal = Style::default();

                assert_eq!(Reset, reverse.difference(&normal));
            }

            #[test]
            fn addition_of_reverse() {
                let reverse = Style::new().reverse();
                let normal = Style::default();
                let extra_styles = ExtraStyles(reverse);

                assert_eq!(extra_styles, normal.difference(&reverse));
            }

            #[test]
            fn removal_of_hidden() {
                let hidden = Style::new().hidden();
                let normal = Style::default();

                assert_eq!(Reset, hidden.difference(&normal));
            }

            #[test]
            fn addition_of_hidden() {
                let hidden = Style::new().hidden();
                let normal = Style::default();
                let extra_styles = ExtraStyles(hidden);

                assert_eq!(extra_styles, normal.difference(&hidden));
            }

            #[test]
            fn no_control_codes_for_plain() {
                let one = Style::default().paint("one");
                let two = Style::default().paint("two");
                let output = format!("{}", ANSIStrings( &[ one, two ] ));
                assert_eq!(&*output, "onetwo");
            }
        }
    }

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