use core::{
	fmt,
	fmt::{Debug, Display, Formatter},
};
use embedded_graphics::pixelcolor::PixelColor;

/// Store image data.
///
/// Image can be constructed using the [`include_image`](crate::include_image) macro at compile time.
/// To draw an image it must be put inside a [`Sprite`](crate::sprite::Sprite).
#[derive(Debug)]
pub struct Image<'a, C: PixelColor> {
	pub(crate) width: u16,
	pub(crate) transparenty: &'a [u8],
	pub(crate) colors: &'a [C],
}

#[derive(Debug, Eq, PartialEq)]
pub enum Dimension {
	Width,
	Height,
}

#[derive(Debug, Eq, PartialEq)]
pub enum Error {
	WrongPixelLength(Dimension),
}

impl Display for Error {
	fn fmt(&self, f: &mut Formatter) -> fmt::Result {
		match self {
			Self::WrongPixelLength(dimension) => match dimension {
				Dimension::Width => write!(f, "length of `colors` is is not divisible by `width`"),
				Dimension::Height => write!(f, "`colors.len()/width` does not match provided `height`"),
			},
		}
	}
}
impl Error {
	#[doc(hidden)]
	// const unwrap; see https://docs.rs/konst/0.3.4/konst/result/macro.unwrap_ctx.html
	pub const fn panic(&self) -> ! {
		match self {
			Self::WrongPixelLength(dimension) => match dimension {
				Dimension::Width => panic!("Error creating image:	length of `colors` is is not divisible by `width`"),
				Dimension::Height => panic!("Error creating image:	`colors.len()/width` does not match provided `height`"),
			},
		}
	}
}

impl<'a, C: PixelColor> Image<'a, C> {
	/// create a new [Image] from a array of [PixelColor]s, a transparenty map.
	///
	/// Return an error, if the length of `colors` does not fit to the widht and height.
	/// You can unwrap the error in a const contexts,
	/// by using the [konst](https://crates.io/crates/konst) crate see [`konst::result::unwrap_ctx`](https://docs.rs/konst/0.3.4/konst/result/macro.unwrap_ctx.html) for more informations.
	///
	/// `transparency` can be created by using the [`transparency!`](crate::transparency) macro.
	/// It's length doesn’t have to match the image length, missing data will be interpreted as fully opaque.
	///
	/// ```
	/// use embedded_graphics::pixelcolor::Bgr565;
	/// use embedded_sprites::{image::Image, transparency};
	/// use konst::result::unwrap_ctx;
	///
	/// type Color = Bgr565;
	/// const IMAGE_DATA: [Color; 6] = [
	/// 	Color::new(255, 0, 0),
	/// 	Color::new(0, 255, 0),
	/// 	Color::new(0, 0, 255),
	/// 	Color::new(255, 0, 255),
	/// 	Color::new(255, 255, 255),
	/// 	Color::new(255, 255, 255),
	/// ];
	/// const IMAGE: Image<Color> =
	/// 	unwrap_ctx!(Image::new(&IMAGE_DATA, &transparency![0, 0, 0, 1, 0], 3, 2));
	/// ```

	pub const fn new(colors: &'a [C], transparenty: &'a [u8], width: u16, height: u16) -> Result<Self, Error> {
		if colors.len() % width as usize != 0 {
			return Err(Error::WrongPixelLength(Dimension::Width));
		};
		if colors.len() / width as usize != height as usize {
			return Err(Error::WrongPixelLength(Dimension::Height));
		};
		Ok(Image {
			colors,
			transparenty,
			width,
		})
	}
}

/// Utility macro to construct a transparency array from bits. Can be used when creating an [`Image`].
///
/// The number of bits doesn't have to match the image length, missing data will be interpreted as fully opaque.
///
/// ```
/// # use embedded_sprites::transparency;
/// let transparency = transparency![0, 0, 1, 0];
/// ```
///
/// The result is that the 3rd pixel is transparent, and all other pixels are opaque.
#[macro_export]
macro_rules! transparency {
	($($x:expr),*) => {
		{
			const N: usize = [$($x),*].len();
			const LEN: usize = N / 8 + if N % 8 > 0 { 1 } else { 0 };
			const T: [u8; LEN] = {
				let mut t = [0u8; LEN];
				let mut i = 0;
				let mut j = 7;
				$(
					t[i] |= ($x & 1 ) << j;
					#[allow(unused_assignments)]
					if j == 0 {
						j = 7;
						i += 1;
					} else {
						j -= 1;
					}
				)*
					t
			};
			T
		}
	};
}

#[cfg(test)]
mod tests {
	use super::{Dimension, Error, Image};
	use crate::transparency;
	use embedded_graphics::pixelcolor::Bgr565;
	use konst::result::unwrap_ctx;

	type Color = Bgr565;

	const IMAGE_DATA: [Color; 6] = [
		Color::new(255, 0, 0),
		Color::new(0, 255, 0),
		Color::new(0, 0, 255),
		Color::new(255, 0, 255),
		Color::new(255, 255, 255),
		Color::new(255, 255, 255),
	];

	#[test]
	fn create_const_image() {
		#[allow(dead_code)]
		const IMAGE1: Image<Color> = unwrap_ctx!(Image::new(&IMAGE_DATA, &transparency![0, 0, 0, 1, 0, 0], 3, 2));
		#[allow(dead_code)]
		const IMAGE2: Image<Color> = unwrap_ctx!(Image::new(&IMAGE_DATA, &transparency![0, 0, 0, 0], 3, 2));
		//todo: check if iterator of image is identical if I put them inside a sprite
	}
	#[test]
	fn create_image_wrong_widht() {
		assert_eq!(
			Image::new(&IMAGE_DATA, &transparency![0, 0, 0, 0], 4, 2).unwrap_err(),
			Error::WrongPixelLength(Dimension::Width)
		);
	}
	#[test]
	fn create_image_wrong_hight() {
		assert_eq!(
			Image::new(&IMAGE_DATA, &transparency![0, 0, 0, 0], 3, 3).unwrap_err(),
			Error::WrongPixelLength(Dimension::Height)
		);
	}
}