#![doc(html_root_url = "https://docs.rs/tiny-skia/0.1.0")]

use std::ops::{Deref, DerefMut};
use std::slice;

mod ffi {
    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_surface { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_canvas { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_paint { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_path { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_shader { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_path_effect { _unused: [u8; 0] }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_transform {
        pub a: f32,
        pub b: f32,
        pub c: f32,
        pub d: f32,
        pub e: f32,
        pub f: f32,
    }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_point {
        pub x: f32,
        pub y: f32,
    }

    #[repr(C)]
    #[derive(Clone, Copy, Debug)]
    pub struct skiac_surface_data {
        pub ptr: *mut u8,
        pub size: u32,
    }

    extern "C" {

        pub fn skiac_surface_create_rgba_premultiplied(
            width: i32,
            height: i32,
        ) -> *mut skiac_surface;

        pub fn skiac_surface_create_rgba(
            width: i32,
            height: i32,
        ) -> *mut skiac_surface;

        pub fn skiac_surface_destroy(
            surface: *mut skiac_surface,
        );

        pub fn skiac_surface_copy_rgba(
            surface: *mut skiac_surface,
            x: u32, y: u32, width: u32, height: u32,
        ) -> *mut skiac_surface;

        pub fn skiac_surface_get_canvas(
            surface: *mut skiac_surface,
        ) -> *mut skiac_canvas;

        pub fn skiac_surface_get_width(
            surface: *mut skiac_surface,
        ) -> i32;

        pub fn skiac_surface_get_height(
            surface: *mut skiac_surface,
        ) -> i32;

        pub fn skiac_surface_read_pixels(
            surface: *mut skiac_surface,
            data: *mut skiac_surface_data,
        );

        pub fn skiac_surface_get_alpha_type(
            surface: *mut skiac_surface,
        ) -> i32;

        pub fn skiac_canvas_clear(
            canvas: *mut skiac_canvas,
            color: u32,
        );

        pub fn skiac_canvas_flush(
            canvas: *mut skiac_canvas,
        );

        pub fn skiac_canvas_set_transform(
            canvas: *mut skiac_canvas,
            ts: skiac_transform,
        );

        pub fn skiac_canvas_concat(
            canvas: *mut skiac_canvas,
            ts: skiac_transform,
        );

        pub fn skiac_canvas_scale(
            canvas: *mut skiac_canvas,
            sx: f32,
            sy: f32,
        );

        pub fn skiac_canvas_translate(
            canvas: *mut skiac_canvas,
            dx: f32,
            dy: f32,
        );

        pub fn skiac_canvas_get_total_transform(
            canvas: *mut skiac_canvas,
        ) -> skiac_transform;

        pub fn skiac_canvas_draw_path(
            canvas: *mut skiac_canvas,
            path: *mut skiac_path,
            paint: *mut skiac_paint,
        );

        pub fn skiac_canvas_draw_rect(
            canvas: *mut skiac_canvas,
            x: f32, y: f32, w: f32, h: f32,
            paint: *mut skiac_paint,
        );

        pub fn skiac_canvas_draw_surface(
            canvas: *mut skiac_canvas,
            surface: *mut skiac_surface,
            left: f32,
            top: f32,
            alpha: u8,
            blend_mode: i32,
            filter_quality: i32,
        );

        pub fn skiac_canvas_draw_surface_rect(
            canvas: *mut skiac_canvas,
            surface: *mut skiac_surface,
            x: f32, y: f32, w: f32, h: f32,
            filter_quality: i32,
        );

        pub fn skiac_canvas_reset_transform(
            canvas: *mut skiac_canvas,
        );

        pub fn skiac_canvas_clip_rect(
            canvas: *mut skiac_canvas,
            x: f32, y: f32, w: f32, h: f32,
        );

        pub fn skiac_canvas_save(
            canvas: *mut skiac_canvas,
        );

        pub fn skiac_canvas_restore(
            canvas: *mut skiac_canvas,
        );

        pub fn skiac_paint_create() -> *mut skiac_paint;

        pub fn skiac_paint_destroy(
            paint: *mut skiac_paint,
        );

        pub fn skiac_paint_set_style(
            paint: *mut skiac_paint,
            style: i32,
        );

        pub fn skiac_paint_set_color(
            paint: *mut skiac_paint,
            r: u8, g: u8, b: u8, a: u8,
        );

        pub fn skiac_paint_set_alpha(
            paint: *mut skiac_paint,
            a: u8,
        );

        pub fn skiac_paint_set_anti_alias(
            paint: *mut skiac_paint,
            aa: bool,
        );

        pub fn skiac_paint_set_blend_mode(
            paint: *mut skiac_paint,
            blend_mode: i32,
        );

        pub fn skiac_paint_set_shader(
            paint: *mut skiac_paint,
            shader: *mut skiac_shader,
        );

        pub fn skiac_paint_set_stroke_width(
            paint: *mut skiac_paint,
            width: f32,
        );

        pub fn skiac_paint_set_stroke_cap(
            paint: *mut skiac_paint,
            cap: i32,
        );

        pub fn skiac_paint_set_stroke_join(
            paint: *mut skiac_paint,
            join: i32,
        );

        pub fn skiac_paint_set_stroke_miter(
            paint: *mut skiac_paint,
            miter: f32,
        );

        pub fn skiac_paint_set_path_effect(
            paint: *mut skiac_paint,
            path_effect: *mut skiac_path_effect,
        );

        pub fn skiac_path_create() -> *mut skiac_path;

        pub fn skiac_path_destroy(
            path: *mut skiac_path,
        );

        pub fn skiac_path_set_fill_type(
            path: *mut skiac_path,
            kind: i32,
        );

        pub fn skiac_path_move_to(
            path: *mut skiac_path,
            x: f32,
            y: f32,
        );

        pub fn skiac_path_line_to(
            path: *mut skiac_path,
            x: f32,
            y: f32,
        );

        pub fn skiac_path_cubic_to(
            path: *mut skiac_path,
            x1: f32, y1: f32,
            x2: f32, y2: f32,
            x3: f32, y3: f32,
        );

        pub fn skiac_path_close(
            path: *mut skiac_path,
        );

        pub fn skiac_path_effect_make_dash_path(
            intervals: *const f32,
            count: i32,
            phase: f32,
        ) -> *mut skiac_path_effect;

        pub fn skiac_path_effect_destroy(
            path_effect: *mut skiac_path_effect,
        );

        pub fn skiac_shader_make_linear_gradient(
            points: *const skiac_point,
            colors: *const super::Color,
            positions: *const f32,
            count: i32,
            tile_mode: i32,
            flags: u32,
            ts: skiac_transform,
        ) -> *mut skiac_shader;

        pub fn skiac_shader_make_two_point_conical_gradient(
            start_point: skiac_point,
            start_radius: f32,
            end_point: skiac_point,
            end_radius: f32,
            colors: *const super::Color,
            positions: *const f32,
            count: i32,
            tile_mode: i32,
            flags: u32,
            ts: skiac_transform,
        ) -> *mut skiac_shader;

        pub fn skiac_shader_make_from_surface_image(
            surface: *mut skiac_surface,
            ts: skiac_transform,
        ) -> *mut skiac_shader;

        pub fn skiac_shader_destroy(
            shader: *mut skiac_shader,
        );
    }
}


#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum PaintStyle {
    Fill = 0,
    Stroke = 1,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum FillType {
    Winding = 0,
    EvenOdd = 1,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum StrokeCap {
    Butt = 0,
    Round = 1,
    Square = 2,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum StrokeJoin {
    Miter = 0,
    Round = 1,
    Bevel = 2,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum TileMode {
    Clamp = 0,
    Repeat = 1,
    Mirror = 2,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum BlendMode {
    /// Replaces destination with zero: fully transparent.
    Clear = 0,
    /// Replaces destination.
    Source,
    /// Preserves destination.
    Destination,
    /// Source over destination.
    SourceOver,
    /// Destination over source.
    DestinationOver,
    /// Source trimmed inside destination.
    SourceIn,
    /// Destination trimmed by source.
    DestinationIn,
    /// Source trimmed outside destination.
    SourceOut,
    /// Destination trimmed outside source.
    DestinationOut,
    /// Source inside destination blended with destination.
    SourceATop,
    /// Destination inside source blended with source.
    DestinationATop,
    /// Each of source and destination trimmed outside the other.
    Xor,
    /// Sum of colors.
    Plus,
    /// Product of premultiplied colors; darkens destination.
    Modulate,
    /// Multiply inverse of pixels, inverting result; brightens destination.
    Screen,
    /// Multiply or screen, depending on destination.
    Overlay,
    /// Darker of source and destination.
    Darken,
    /// Lighter of source and destination.
    Lighten,
    /// Brighten destination to reflect source.
    ColorDodge,
    /// Darken destination to reflect source.
    ColorBurn,
    /// Multiply or screen, depending on source.
    HardLight,
    /// Lighten or darken, depending on source.
    SoftLight,
    /// Subtract darker from lighter with higher contrast.
    Difference,
    /// Subtract darker from lighter with lower contrast.
    Exclusion,
    /// Multiply source with destination, darkening image.
    Multiply,
    /// Hue of source with saturation and luminosity of destination.
    Hue,
    /// Saturation of source with hue and luminosity of destination.
    Saturation,
    /// Hue and saturation of source with luminosity of destination.
    Color,
    /// Luminosity of source with hue and saturation of destination.
    Luminosity,
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum FilterQuality {
    None = 0,
    Low = 1,
    Medium = 2,
    High = 3,
}

/// Describes how to interpret the alpha component of a pixel.
///
/// A pixel may be opaque, or alpha, describing multiple levels of transparency.
///
/// In simple blending, alpha weights the draw color and the destination
/// color to create a new color. If alpha describes a weight from zero to one:
///
/// new color = draw color * alpha + destination color * (1 - alpha)
///
/// In practice alpha is encoded in two or more bits, where 1.0 equals all bits set.
///
/// RGB may have alpha included in each component value; the stored
/// value is the original RGB multiplied by alpha. Premultiplied color
/// components improve performance.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum AlphaType {
    Unknown,
    Opaque,
    Premultiplied,
    Unpremultiplied,
}

pub struct Surface {
    ptr: *mut ffi::skiac_surface,
    canvas: Canvas,
}

impl Surface {
    // TODO: use AlphaType

    #[inline]
    pub fn new_rgba(width: u32, height: u32) -> Option<Surface> {
        unsafe {
            Self::from_ptr(ffi::skiac_surface_create_rgba(width as i32, height as i32))
        }
    }

    #[inline]
    pub fn new_rgba_premultiplied(width: u32, height: u32) -> Option<Surface> {
        unsafe {
            Self::from_ptr(ffi::skiac_surface_create_rgba_premultiplied(width as i32, height as i32))
        }
    }

    #[inline]
    unsafe fn from_ptr(ptr: *mut ffi::skiac_surface) -> Option<Surface> {
        if ptr.is_null() {
            None
        } else {
            Some(Surface {
                ptr,
                canvas: Canvas(ffi::skiac_surface_get_canvas(ptr))
            })
        }
    }

    #[inline]
    pub fn copy_rgba(&self, x: u32, y: u32, width: u32, height: u32) -> Option<Surface> {
        unsafe { Self::from_ptr(ffi::skiac_surface_copy_rgba(self.ptr, x, y, width, height)) }
    }

    #[inline]
    pub fn try_clone(&self) -> Option<Surface> {
        unsafe { Self::from_ptr(ffi::skiac_surface_copy_rgba(self.ptr, 0, 0, self.width(), self.height())) }
    }

    #[cfg(feature = "png-encoding")]
    pub fn save_png<P: AsRef<std::path::Path>>(&self, path: P) -> Result<(), png::EncodingError> {
        let file = std::fs::File::create(path)?;
        let ref mut w = std::io::BufWriter::new(file);

        let mut encoder = png::Encoder::new(w, self.width(), self.height());
        encoder.set_color(png::ColorType::RGBA);
        encoder.set_depth(png::BitDepth::Eight);
        let mut writer = encoder.write_header()?;

        if self.alpha_type() == AlphaType::Premultiplied {
            // TODO: remove allocation
            let mut data = self.data_u8().to_vec();
            demultiply_alpha(&mut data);
            writer.write_image_data(&data)
        } else if self.alpha_type() == AlphaType::Unpremultiplied {
            writer.write_image_data(&self.data())
        } else {
            panic!("unsupported alpha type")
        }
    }

    #[inline]
    pub fn width(&self) -> u32 {
        unsafe { ffi::skiac_surface_get_width(self.ptr) as u32 }
    }

    #[inline]
    pub fn height(&self) -> u32 {
        unsafe { ffi::skiac_surface_get_height(self.ptr) as u32 }
    }

    #[inline]
    pub fn alpha_type(&self) -> AlphaType {
        let kind = unsafe { ffi::skiac_surface_get_alpha_type(self.ptr) };
        match kind {
            0 => AlphaType::Unknown,
            1 => AlphaType::Opaque,
            2 => AlphaType::Premultiplied,
            3 => AlphaType::Unpremultiplied,
            _ => unreachable!(),
        }
    }

    #[inline]
    pub fn data_u8(&self) -> &[u8] {
        unsafe {
            let mut data = ffi::skiac_surface_data {
                ptr: std::ptr::null_mut(),
                size: 0,
            };
            ffi::skiac_surface_read_pixels(self.ptr, &mut data);

            slice::from_raw_parts(data.ptr, data.size as usize)
        }
    }

    #[inline]
    pub fn data(&self) -> SurfaceData {
        SurfaceData {
            slice: self.data_u8(),
        }
    }

    #[inline]
    pub fn data_mut(&mut self) -> SurfaceDataMut {
        unsafe {
            let mut data = ffi::skiac_surface_data {
                ptr: std::ptr::null_mut(),
                size: 0,
            };
            ffi::skiac_surface_read_pixels(self.ptr, &mut data);

            SurfaceDataMut {
                slice: slice::from_raw_parts_mut(data.ptr, data.size as usize),
            }
        }
    }
}

impl std::ops::Deref for Surface {
    type Target = Canvas;

    #[inline]
    fn deref(&self) -> &Self::Target {
        &self.canvas
    }
}

impl std::ops::DerefMut for Surface {
    #[inline]
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.canvas
    }
}

impl Drop for Surface {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            ffi::skiac_surface_destroy(self.ptr);
        }
    }
}


pub struct SurfaceData<'a> {
    slice: &'a [u8],
}

impl<'a> Deref for SurfaceData<'a> {
    type Target = [u8];

    #[inline]
    fn deref(&self) -> &[u8] {
        self.slice
    }
}


pub struct SurfaceDataMut<'a> {
    slice: &'a mut [u8],
}

impl<'a> Deref for SurfaceDataMut<'a> {
    type Target = [u8];

    #[inline]
    fn deref(&self) -> &[u8] {
        self.slice
    }
}

impl<'a> DerefMut for SurfaceDataMut<'a> {
    #[inline]
    fn deref_mut(&mut self) -> &mut [u8] {
        self.slice
    }
}


#[repr(C)]
#[derive(Clone, Copy, Debug)]
pub struct Color(pub u32);

impl Color {
    #[inline]
    pub fn new(a: u8, r: u8, g: u8, b: u8) -> Color {
        Color((a as u32) << 24 | (r as u32) << 16 | (g as u32) << 8 | (b as u32))
    }
}


pub struct Canvas(*mut ffi::skiac_canvas);

impl Canvas {
    #[inline]
    pub fn clear(&mut self) {
        unsafe { ffi::skiac_canvas_clear(self.0, 0); }
    }

    #[inline]
    pub fn fill(&mut self, r: u8, g: u8, b: u8, a: u8) {
        unsafe {
            ffi::skiac_canvas_clear(
                self.0,
                (a as u32) << 24 | (r as u32) << 16 | (g as u32) << 8 | b as u32
            );
        }
    }

    #[inline]
    pub fn flush(&mut self) {
        unsafe { ffi::skiac_canvas_flush(self.0); }
    }

    #[inline]
    pub fn set_transform(&mut self, ts: Transform) {
        unsafe { ffi::skiac_canvas_set_transform(self.0, ts.into()); }
    }

    #[inline]
    pub fn concat(&mut self, ts: Transform) {
        unsafe { ffi::skiac_canvas_concat(self.0, ts.into()); }
    }

    #[inline]
    pub fn scale(&mut self, sx: f32, sy: f32) {
        unsafe { ffi::skiac_canvas_scale(self.0, sx, sy); }
    }

    #[inline]
    pub fn translate(&mut self, dx: f32, dy: f32) {
        unsafe { ffi::skiac_canvas_translate(self.0, dx, dy); }
    }

    #[inline]
    pub fn get_transform(&self) -> Transform {
        unsafe { ffi::skiac_canvas_get_total_transform(self.0).into() }
    }

    #[inline]
    pub fn reset_transform(&mut self) {
        unsafe { ffi::skiac_canvas_reset_transform(self.0); }
    }

    #[inline]
    pub fn draw_path(&mut self, path: &Path, paint: &Paint) {
        unsafe { ffi::skiac_canvas_draw_path(self.0, path.0, paint.0); }
    }

    #[inline]
    pub fn draw_rect(&mut self, x: f32, y: f32, w: f32, h: f32, paint: &Paint) {
        unsafe { ffi::skiac_canvas_draw_rect(self.0, x, y, w, h, paint.0); }
    }

    #[inline]
    pub fn draw_surface(
        &mut self,
        surface: &Surface,
        left: f32,
        top: f32,
        alpha: u8,
        blend_mode: BlendMode,
        filter_quality: FilterQuality,
    ) {
        unsafe {
            ffi::skiac_canvas_draw_surface(
                self.0, surface.ptr, left, top, alpha, blend_mode as i32, filter_quality as i32,
            );
        }
    }

    #[inline]
    pub fn draw_surface_rect(
        &mut self,
        surface: &Surface,
        x: f32, y: f32, w: f32, h: f32,
        filter_quality: FilterQuality,
    ) {
        unsafe {
            ffi::skiac_canvas_draw_surface_rect(
                self.0, surface.ptr, x, y, w, h, filter_quality as i32,
            );
        }
    }

    #[inline]
    pub fn set_clip_rect(&mut self, x: f32, y: f32, w: f32, h: f32) {
        unsafe { ffi::skiac_canvas_clip_rect(self.0, x, y, w, h); }
    }

    #[inline]
    pub fn save(&mut self) {
        unsafe { ffi::skiac_canvas_save(self.0); }
    }

    #[inline]
    pub fn restore(&mut self) {
        unsafe { ffi::skiac_canvas_restore(self.0); }
    }
}

pub struct Paint(*mut ffi::skiac_paint);

impl Paint {
    #[inline]
    pub fn new() -> Paint {
        unsafe { Paint(ffi::skiac_paint_create()) }
    }

    #[inline]
    pub fn set_style(&mut self, style: PaintStyle) {
        unsafe { ffi::skiac_paint_set_style(self.0, style as i32); }
    }

    #[inline]
    pub fn set_color(&mut self, r: u8, g: u8, b: u8, a: u8) {
        unsafe { ffi::skiac_paint_set_color(self.0, r, g, b, a); }
    }

    #[inline]
    pub fn set_alpha(&mut self, a: u8) {
        unsafe { ffi::skiac_paint_set_alpha(self.0, a); }
    }

    #[inline]
    pub fn set_anti_alias(&mut self, aa: bool) {
        unsafe { ffi::skiac_paint_set_anti_alias(self.0, aa); }
    }

    #[inline]
    pub fn set_blend_mode(&mut self, blend_mode: BlendMode) {
        unsafe { ffi::skiac_paint_set_blend_mode(self.0, blend_mode as i32); }
    }

    #[inline]
    pub fn set_shader(&mut self, shader: &Shader) {
        unsafe { ffi::skiac_paint_set_shader(self.0, shader.0); }
    }

    #[inline]
    pub fn set_stroke_width(&mut self, width: f32) {
        unsafe { ffi::skiac_paint_set_stroke_width(self.0, width); }
    }

    #[inline]
    pub fn set_stroke_cap(&mut self, cap: StrokeCap) {
        unsafe { ffi::skiac_paint_set_stroke_cap(self.0, cap as i32); }
    }

    #[inline]
    pub fn set_stroke_join(&mut self, join: StrokeJoin) {
        unsafe { ffi::skiac_paint_set_stroke_join(self.0, join as i32); }
    }

    #[inline]
    pub fn set_stroke_miter(&mut self, miter: f32) {
        unsafe { ffi::skiac_paint_set_stroke_miter(self.0, miter as f32); }
    }

    #[inline]
    pub fn set_path_effect(&mut self, path_effect: &PathEffect) {
        unsafe { ffi::skiac_paint_set_path_effect(self.0, path_effect.0); }
    }
}

impl Drop for Paint {
    #[inline]
    fn drop(&mut self) {
        unsafe { ffi::skiac_paint_destroy(self.0) }
    }
}


pub struct Path(*mut ffi::skiac_path);

impl Path {
    #[inline]
    pub fn new() -> Path {
        unsafe { Path(ffi::skiac_path_create()) }
    }

    #[inline]
    pub fn set_fill_type(&mut self, kind: FillType) {
        unsafe { ffi::skiac_path_set_fill_type(self.0, kind as i32); }
    }

    #[inline]
    pub fn move_to(&mut self, x: f32, y: f32) {
        unsafe { ffi::skiac_path_move_to(self.0, x, y); }
    }

    #[inline]
    pub fn line_to(&mut self, x: f32, y: f32) {
        unsafe { ffi::skiac_path_line_to(self.0, x, y); }
    }

    #[inline]
    pub fn cubic_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32, x3: f32, y3: f32) {
        unsafe { ffi::skiac_path_cubic_to(self.0, x1, y1, x2, y2, x3, y3); }
    }

    #[inline]
    pub fn close(&mut self) {
        unsafe { ffi::skiac_path_close(self.0); }
    }
}

impl Drop for Path {
    #[inline]
    fn drop(&mut self) {
        unsafe { ffi::skiac_path_destroy(self.0); }
    }
}


pub struct Gradient {
    pub colors: Vec<Color>,
    pub positions: Vec<f32>,
    pub tile_mode: TileMode,
    pub transform: Transform,
}

pub struct LinearGradient {
    pub start_point: (f32, f32),
    pub end_point: (f32, f32),
    pub base: Gradient,
}

pub struct TwoPointConicalGradient {
    pub start: (f32, f32),
    pub start_radius: f32,
    pub end: (f32, f32),
    pub end_radius: f32,
    pub base: Gradient,
}

pub struct Shader(*mut ffi::skiac_shader);

impl Shader {
    #[inline]
    pub fn new_linear_gradient(grad: &LinearGradient) -> Option<Shader> {
        let points = [
            ffi::skiac_point { x: grad.start_point.0, y: grad.start_point.1 },
            ffi::skiac_point { x: grad.end_point.0, y: grad.end_point.1 }
        ];

        unsafe {
            Self::from_ptr(ffi::skiac_shader_make_linear_gradient(
                points.as_ptr(),
                grad.base.colors.as_ptr(),
                grad.base.positions.as_ptr(),
                grad.base.colors.len() as i32,
                grad.base.tile_mode as i32,
                0 as u32,
                grad.base.transform.into(),
            ))
        }
    }

    #[inline]
    pub fn new_two_point_conical_gradient(grad: &TwoPointConicalGradient) -> Option<Shader> {
        let start_point = ffi::skiac_point { x: grad.start.0, y: grad.start.1 };
        let end_point = ffi::skiac_point { x: grad.end.0, y: grad.end.1 };

        unsafe {
            Self::from_ptr(ffi::skiac_shader_make_two_point_conical_gradient(
                start_point, grad.start_radius,
                end_point, grad.end_radius,
                grad.base.colors.as_ptr(),
                grad.base.positions.as_ptr(),
                grad.base.colors.len() as i32,
                grad.base.tile_mode as i32,
                0 as u32,
                grad.base.transform.into(),
            ))
        }
    }

    #[inline]
    pub fn new_from_surface_image(surface: &Surface, ts: Transform) -> Option<Shader> {
        unsafe {
            Self::from_ptr(ffi::skiac_shader_make_from_surface_image(surface.ptr, ts.into()))
        }
    }

    #[inline]
    unsafe fn from_ptr(ptr: *mut ffi::skiac_shader) -> Option<Shader> {
        if ptr.is_null() {
            None
        } else {
            Some(Shader(ptr))
        }
    }
}

impl Drop for Shader {
    #[inline]
    fn drop(&mut self) {
        unsafe { ffi::skiac_shader_destroy(self.0); }
    }
}


pub struct PathEffect(*mut ffi::skiac_path_effect);

impl PathEffect {
    #[inline]
    pub fn new_dash_path(intervals: &[f32], phase: f32) -> Option<PathEffect> {
        unsafe {
            let ptr = ffi::skiac_path_effect_make_dash_path(
                intervals.as_ptr(),
                intervals.len() as i32,
                phase,
            );

            if ptr.is_null() {
                None
            } else {
                Some(PathEffect(ptr))
            }
        }
    }
}

impl Drop for PathEffect {
    #[inline]
    fn drop(&mut self) {
        unsafe { ffi::skiac_path_effect_destroy(self.0); }
    }
}


#[derive(Clone, Copy, PartialEq, Debug)]
pub struct Transform {
    pub a: f32,
    pub b: f32,
    pub c: f32,
    pub d: f32,
    pub e: f32,
    pub f: f32,
}

impl Transform {
    pub fn new(a: f32, b: f32, c: f32, d: f32, e: f32, f: f32) -> Self {
        Transform { a, b, c, d, e, f }
    }
}

impl Default for Transform {
    fn default() -> Self {
        Transform::new(1.0, 0.0, 0.0, 1.0, 0.0, 0.0)
    }
}

impl From<ffi::skiac_transform> for Transform {
    #[inline]
    fn from(ts: ffi::skiac_transform) -> Self {
        Transform::new(ts.a, ts.b, ts.c, ts.d, ts.e, ts.f)
    }
}

impl From<Transform> for ffi::skiac_transform {
    #[inline]
    fn from(ts: Transform) -> Self {
        ffi::skiac_transform {
            a: ts.a,
            b: ts.b,
            c: ts.c,
            d: ts.d,
            e: ts.e,
            f: ts.f,
        }
    }
}


fn demultiply_alpha(data: &mut [u8]) {
    struct RGBA { r: u8, g: u8, b: u8, a: u8 }

    let data: &mut [RGBA] = unsafe {
        slice::from_raw_parts_mut(data.as_ptr() as *mut _, data.len() / 4)
    };

    for p in data {
        let a = p.a as f64 / 255.0;
        p.b = (p.b as f64 / a + 0.5) as u8;
        p.g = (p.g as f64 / a + 0.5) as u8;
        p.r = (p.r as f64 / a + 0.5) as u8;
    }
}