use comparison::traits::{Max, Min};
use named::Named;

/// The number of [Unicode scalar values](https://www.unicode.org/glossary/#unicode_scalar_value).
///
/// $2^{20}+2^{16}-2^{11} = \mathrm{0x10\\,f800} = 1,\\!112,\\!064$.
pub const NUMBER_OF_CHARS: u32 = (1 << 20) + (1 << 16) - NUMBER_OF_SURROGATE_CODE_POINTS;

/// The number of [surrogate code points](https://www.unicode.org/glossary/#surrogate_code_point);
/// these are code points that do not correspond to any valid [`char`].
///
/// $2^{11} = 2,\\!048$.
pub const NUMBER_OF_SURROGATE_CODE_POINTS: u32 = 1 << 11;

/// The first [surrogate code point](https://www.unicode.org/glossary/#surrogate_code_point).
pub const FIRST_SURROGATE_CODE_POINT: u32 = 0xd800;

/// The [`char`] that comes just before the surrogate range.
///
/// This happens to be an unassigned (as of Unicode 14.0) character in the
/// [Hangul Jamo Extended-B block](https://www.unicode.org/charts/PDF/UD7B0.pdf).
pub const CHAR_JUST_BELOW_SURROGATES: char = '\u{d7ff}';

/// The [`char`] that comes just after the surrogate range.
///
/// This is a character in the [Private Use Area](https://www.unicode.org/charts/PDF/UE000.pdf).
pub const CHAR_JUST_ABOVE_SURROGATES: char = '\u{e000}';

impl Min for char {
    /// The minimum value of a [`char`]: `'\u{0}'`.
    ///
    /// This is the famous NUL character, a
    /// [C0 control](https://www.unicode.org/charts/PDF/U0000.pdf).
    const MIN: char = '\u{0}';
}

impl Max for char {
    /// The maximum value of a [`char`]: `'\u{10ffff}'`.
    ///
    /// This is a character in
    /// [Supplementary Private Use Area-B](https://www.unicode.org/charts/PDF/U10FF80.pdf).
    const MAX: char = std::char::MAX;
}

impl_named!(char);