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// rgb.rs       RGB pixel format.
//
// Copyright (c) 2018-2019  Douglas P Lau
//
use crate::{
    Alpha, Channel, Ch8, Ch16, Ch32, Format, Opaque, PixModes, Translucent,
};

/// RGB pixel [Format](trait.Format.html), with optional
/// [Alpha](trait.Alpha.html) channel.
///
/// The `Channel`s are *red*, *green* and *blue*.
#[derive(Clone, Copy, Debug, Default, PartialEq)]
#[repr(C)]
pub struct Rgb<C: Channel, A: Alpha> {
    red: C,
    green: C,
    blue: C,
    alpha: A,
}

impl<C: Channel, A: Alpha> PixModes for Rgb<C, A> { }

impl<C: Channel, A: Alpha> Iterator for Rgb<C, A> {
    type Item = Self;

    fn next(&mut self) -> Option<Self::Item> {
        Some(*self)
    }
}

impl<C, A> From<i32> for Rgb<C, A>
    where C: Channel + From<Ch8>, A: Alpha<Chan=C> + From<Translucent<Ch8>>
{
    /// Get an `Rgb` from an `i32`
    fn from(c: i32) -> Self {
        let red = Ch8::from((c >> 0) as u8);
        let green = Ch8::from((c >> 8) as u8);
        let blue = Ch8::from((c >> 16) as u8);
        let alpha = Ch8::from((c >> 24) as u8);
        Rgb::with_alpha(red, green, blue, Translucent::new(alpha))
    }
}

impl<C, A> From<Rgb<C, A>> for i32
    where C: Channel, Ch8: From<C>, A: Alpha<Chan=C>
{
    /// Get an `i32` from an `Rgb`
    fn from(c: Rgb<C, A>) -> i32 {
        let red: u8 = Ch8::from(c.red()).into();
        let red = i32::from(red);
        let green: u8 = Ch8::from(c.green()).into();
        let green = i32::from(green) << 8;
        let blue: u8 = Ch8::from(c.blue()).into();
        let blue = i32::from(blue) << 16;
        let alpha: u8 = Ch8::from(c.alpha().value()).into();
        let alpha = i32::from(alpha) << 24;
        red | green | blue | alpha
    }
}

impl<C: Channel, A: Alpha> Rgb<C, A> {
    /// Create an [Opaque](struct.Opaque.html) color by specifying *red*,
    /// *green* and *blue* values.
    pub fn new<H>(red: H, green: H, blue: H) -> Self
        where C: From<H>, A: From<Opaque<C>>
    {
        Self::with_alpha(red, green, blue, Opaque::default())
    }
    /// Create a [Translucent](struct.Translucent.html) color by specifying
    /// *red*, *green*, *blue* and *alpha* values.
    pub fn with_alpha<H, B>(red: H, green: H, blue: H, alpha: B) -> Self
        where C: From<H>, A: From<B>
    {
        let red = C::from(red);
        let green = C::from(green);
        let blue = C::from(blue);
        let alpha = A::from(alpha);
        Rgb { red, green, blue, alpha }
    }
    /// Get the red `Channel`.
    pub fn red(self) -> C {
        self.red
    }
    /// Get the green `Channel`.
    pub fn green(self) -> C {
        self.green
    }
    /// Get the blue `Channel`.
    pub fn blue(self) -> C {
        self.blue
    }
    /// Get the alpha `Channel`.
    pub fn alpha(self) -> A {
        self.alpha
    }
}

impl<C, A> Format for Rgb<C, A>
    where C: Channel, A: Alpha<Chan=C> + From<C>
{
    type Chan = C;

    /// Get *red*, *green*, *blue* and *alpha* `Channel`s
    fn rgba(self) -> [Self::Chan; 4] {
        [self.red, self.green, self.blue, self.alpha.value()]
    }

    /// Make a pixel with given RGBA `Channel`s
    fn with_rgba(rgba: [Self::Chan; 4]) -> Self {
        let red = rgba[0];
        let green = rgba[1];
        let blue = rgba[2];
        let alpha = rgba[3];
        Rgb::with_alpha(red, green, blue, alpha)
    }

    /// Get channel-wise difference
    fn difference(self, rhs: Self) -> Self {
        let r = if self.red > rhs.red { self.red - rhs.red }
                else { rhs.red - self.red };
        let g = if self.green > rhs.green { self.green - rhs.green }
                else { rhs.green - self.green };
        let b = if self.blue > rhs.blue { self.blue - rhs.blue }
                else { rhs.blue - self.blue };
        let a = if self.alpha.value() > rhs.alpha.value() {
            self.alpha.value() - rhs.alpha.value()
        } else {
            rhs.alpha.value() - self.alpha.value()
        };
        Rgb::with_alpha(r, g, b, a)
    }

    /// Check if all `Channel`s are within threshold
    fn within_threshold(self, rhs: Self) -> bool {
        self.red <= rhs.red &&
        self.green <= rhs.green &&
        self.blue <= rhs.blue &&
        self.alpha.value() <= rhs.alpha.value()
    }
}

/// [Opaque](struct.Opaque.html) 8-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgb8 = Rgb<Ch8, Opaque<Ch8>>;

/// [Opaque](struct.Opaque.html) 16-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgb16 = Rgb<Ch16, Opaque<Ch16>>;

/// [Opaque](struct.Opaque.html) 32-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgb32 = Rgb<Ch32, Opaque<Ch32>>;

/// [Translucent](struct.Translucent.html) 8-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgba8 = Rgb<Ch8, Translucent<Ch8>>;

/// [Translucent](struct.Translucent.html) 16-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgba16 = Rgb<Ch16, Translucent<Ch16>>;

/// [Translucent](struct.Translucent.html) 32-bit [Rgb](struct.Rgb.html) pixel
/// [Format](trait.Format.html).
pub type Rgba32 = Rgb<Ch32, Translucent<Ch32>>;

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

    #[test]
    fn check_sizes() {
        assert_eq!(std::mem::size_of::<Rgb8>(), 3);
        assert_eq!(std::mem::size_of::<Rgb16>(), 6);
        assert_eq!(std::mem::size_of::<Rgb32>(), 12);
        assert_eq!(std::mem::size_of::<Rgba8>(), 4);
        assert_eq!(std::mem::size_of::<Rgba16>(), 8);
        assert_eq!(std::mem::size_of::<Rgba32>(), 16);
    }
}