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use core::fmt;

/// The location for applying a color
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum Canvas {
    Background,
    Foreground,
}

/// Generates ANSI escape sequences using a specific color
pub trait FormatColor {
    /// Apply the color
    fn prelude(&self, f: &mut fmt::Formatter, canvas: Canvas) -> fmt::Result;

    /// Undo the color application
    fn epilogue(&self, f: &mut fmt::Formatter, canvas: Canvas) -> fmt::Result {
        f.write_str(match canvas {
            Canvas::Foreground => "\x1B[39m",
            Canvas::Background => "\x1B[49m"
        })
    }
}

/// Something that will have a foreground color applied
pub struct WithForeground<Item, Formatter: FormatColor> {
    item: Item,
    formatter: Formatter
}

/// Something that will have a background color applied
pub struct WithBackground<Item, Formatter: FormatColor> {
    item: Item,
    formatter: Formatter
}

/// Adds a foreground or background color
pub trait Colorable: Sized {
    /// Add a background color
    fn bg<TFormatColor: FormatColor>(self, formatter: TFormatColor) -> WithBackground<Self, TFormatColor> {
        WithBackground {
            item: self,
            formatter
        }
    }

    /// Add a foreground color
    fn fg<TFormatColor: FormatColor>(self, formatter: TFormatColor) -> WithForeground<Self, TFormatColor> {
        WithForeground {
            item: self,
            formatter
        }
    }
}

impl<T> Colorable for T {}

macro_rules! impl_me {
    ($bound:path) => {
        impl<Item: $bound, TFormatColor: FormatColor> $bound for WithForeground<Item, TFormatColor> {
            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                self.formatter.prelude(f, Canvas::Foreground)
                    .and_then(|_| self.item.fmt(f))
                    .and_then(|_| self.formatter.epilogue(f, Canvas::Foreground))
            }
        }
        impl<Item: $bound, TFormatColor: FormatColor> $bound for WithBackground<Item, TFormatColor> {
            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                self.formatter.prelude(f, Canvas::Background)
                    .and_then(|_| self.item.fmt(f))
                    .and_then(|_| self.formatter.epilogue(f, Canvas::Background))
            }
        }
    };
}

impl_me!(fmt::Binary);
impl_me!(fmt::Debug);
impl_me!(fmt::Display);
impl_me!(fmt::LowerExp);
impl_me!(fmt::LowerHex);
impl_me!(fmt::Octal);
impl_me!(fmt::Pointer);
impl_me!(fmt::UpperExp);
impl_me!(fmt::UpperHex);