use std::hash::{Hash, Hasher};
use stretch::{geometry, style};

/// The appearance of a [`Node`].
///
/// [`Node`]: struct.Node.html
#[derive(Debug, Clone, Copy)]
pub struct Style(pub(crate) style::Style);

impl Style {
    /// Defines the width of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn width(mut self, width: u32) -> Self {
        self.0.size.width = style::Dimension::Points(width as f32);
        self
    }

    /// Defines the height of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn height(mut self, height: u32) -> Self {
        self.0.size.height = style::Dimension::Points(height as f32);
        self
    }

    /// Defines the minimum width of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn min_width(mut self, min_width: u32) -> Self {
        self.0.min_size.width = style::Dimension::Points(min_width as f32);
        self
    }

    /// Defines the maximum width of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn max_width(mut self, max_width: u32) -> Self {
        self.0.max_size.width = style::Dimension::Points(max_width as f32);
        self.fill_width()
    }

    /// Defines the minimum height of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn min_height(mut self, min_height: u32) -> Self {
        self.0.min_size.height = style::Dimension::Points(min_height as f32);
        self
    }

    /// Defines the maximum height of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn max_height(mut self, max_height: u32) -> Self {
        self.0.max_size.height = style::Dimension::Points(max_height as f32);
        self.fill_height()
    }

    /// Makes a [`Node`] fill all the horizontal available space.
    ///
    /// [`Node`]: struct.Node.html
    pub fn fill_width(mut self) -> Self {
        self.0.size.width = stretch::style::Dimension::Percent(1.0);
        self
    }

    /// Makes a [`Node`] fill all the vertical available space.
    ///
    /// [`Node`]: struct.Node.html
    pub fn fill_height(mut self) -> Self {
        self.0.size.height = stretch::style::Dimension::Percent(1.0);
        self
    }

    pub(crate) fn align_items(mut self, align: Align) -> Self {
        self.0.align_items = align.into();
        self
    }

    pub(crate) fn justify_content(mut self, justify: Justify) -> Self {
        self.0.justify_content = justify.into();
        self
    }

    /// Sets the alignment of a [`Node`].
    ///
    /// If the [`Node`] is inside a...
    ///
    ///   * [`Column`], this setting will affect its __horizontal__ alignment.
    ///   * [`Row`], this setting will affect its __vertical__ alignment.
    ///
    /// [`Node`]: struct.Node.html
    /// [`Column`]: widget/struct.Column.html
    /// [`Row`]: widget/struct.Row.html
    pub fn align_self(mut self, align: Align) -> Self {
        self.0.align_self = align.into();
        self
    }

    /// Sets the padding of a [`Node`] in pixels.
    ///
    /// [`Node`]: struct.Node.html
    pub fn padding(mut self, px: u32) -> Self {
        self.0.padding = stretch::geometry::Rect {
            start: style::Dimension::Points(px as f32),
            end: style::Dimension::Points(px as f32),
            top: style::Dimension::Points(px as f32),
            bottom: style::Dimension::Points(px as f32),
        };

        self
    }
}

impl Default for Style {
    fn default() -> Style {
        Style(style::Style {
            align_items: style::AlignItems::FlexStart,
            justify_content: style::JustifyContent::FlexStart,
            ..style::Style::default()
        })
    }
}

impl Hash for Style {
    fn hash<H: Hasher>(&self, state: &mut H) {
        hash_size(&self.0.size, state);
        hash_size(&self.0.min_size, state);
        hash_size(&self.0.max_size, state);

        hash_rect(&self.0.margin, state);

        (self.0.flex_direction as u8).hash(state);
        (self.0.align_items as u8).hash(state);
        (self.0.justify_content as u8).hash(state);
        (self.0.align_self as u8).hash(state);
        (self.0.flex_grow as u32).hash(state);
    }
}

fn hash_size<H: Hasher>(
    size: &geometry::Size<style::Dimension>,
    state: &mut H,
) {
    hash_dimension(size.width, state);
    hash_dimension(size.height, state);
}

fn hash_rect<H: Hasher>(
    rect: &geometry::Rect<style::Dimension>,
    state: &mut H,
) {
    hash_dimension(rect.start, state);
    hash_dimension(rect.end, state);
    hash_dimension(rect.top, state);
    hash_dimension(rect.bottom, state);
}

fn hash_dimension<H: Hasher>(dimension: style::Dimension, state: &mut H) {
    match dimension {
        style::Dimension::Undefined => state.write_u8(0),
        style::Dimension::Auto => state.write_u8(1),
        style::Dimension::Points(points) => {
            state.write_u8(2);
            (points as u32).hash(state);
        }
        style::Dimension::Percent(percent) => {
            state.write_u8(3);
            (percent as u32).hash(state);
        }
    }
}

/// Alignment on the cross axis of a container.
///
///   * On a [`Column`], it describes __horizontal__ alignment.
///   * On a [`Row`], it describes __vertical__ alignment.
///
/// [`Column`]: widget/struct.Column.html
/// [`Row`]: widget/struct.Row.html
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Align {
    /// Align at the start of the cross axis.
    Start,

    /// Align at the center of the cross axis.
    Center,

    /// Align at the end of the cross axis.
    End,

    /// Stretch over the cross axis.
    Stretch,
}

#[doc(hidden)]
impl From<Align> for style::AlignItems {
    fn from(align: Align) -> Self {
        match align {
            Align::Start => style::AlignItems::FlexStart,
            Align::Center => style::AlignItems::Center,
            Align::End => style::AlignItems::FlexEnd,
            Align::Stretch => style::AlignItems::Stretch,
        }
    }
}

#[doc(hidden)]
impl From<Align> for style::AlignSelf {
    fn from(align: Align) -> Self {
        match align {
            Align::Start => style::AlignSelf::FlexStart,
            Align::Center => style::AlignSelf::Center,
            Align::End => style::AlignSelf::FlexEnd,
            Align::Stretch => style::AlignSelf::Stretch,
        }
    }
}

/// Distribution on the main axis of a container.
///
///   * On a [`Column`], it describes __vertical__ distribution.
///   * On a [`Row`], it describes __horizontal__ distribution.
///
/// [`Column`]: widget/struct.Column.html
/// [`Row`]: widget/struct.Row.html
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Justify {
    /// Place items at the start of the main axis.
    Start,

    /// Place items at the center of the main axis.
    Center,

    /// Place items at the end of the main axis.
    End,

    /// Place items with space between.
    SpaceBetween,

    /// Place items with space around.
    SpaceAround,

    /// Place items with evenly distributed space.
    SpaceEvenly,
}

#[doc(hidden)]
impl From<Justify> for style::JustifyContent {
    fn from(justify: Justify) -> Self {
        match justify {
            Justify::Start => style::JustifyContent::FlexStart,
            Justify::Center => style::JustifyContent::Center,
            Justify::End => style::JustifyContent::FlexEnd,
            Justify::SpaceBetween => style::JustifyContent::SpaceBetween,
            Justify::SpaceAround => style::JustifyContent::SpaceAround,
            Justify::SpaceEvenly => style::JustifyContent::SpaceEvenly,
        }
    }
}