use super::{Direction, Expanded};
use ribir_core::prelude::{log::warn, *};

/// How the children should be placed along the main axis in a flex layout.
#[derive(Debug, Copy, Clone, PartialEq, Default)]
pub enum JustifyContent {
  /// Place the children as close to the start of the main axis as possible.
  #[default]
  Start,
  ///Place the children as close to the middle of the main axis as possible.
  Center,
  /// Place the children as close to the end of the main axis as possible.
  End,
  /// The children are evenly distributed within the alignment container along
  /// the main axis. The spacing between each pair of adjacent items is the
  /// same. The first item is flush with the main-start edge, and the last
  /// item is flush with the main-end edge.
  SpaceBetween,
  /// The children are evenly distributed within the alignment container
  /// along the main axis. The spacing between each pair of adjacent items is
  /// the same. The empty space before the first and after the last item
  /// equals half of the space between each pair of adjacent items.
  SpaceAround,
  /// The children are evenly distributed within the alignment container along
  /// the main axis. The spacing between each pair of adjacent items, the
  /// main-start edge and the first item, and the main-end edge and the last
  /// item, are all exactly the same.
  SpaceEvenly,
}

#[derive(Default, MultiChild, Declare, Query, Clone, PartialEq)]
pub struct Flex {
  /// Reverse the main axis.
  #[declare(default)]
  pub reverse: bool,
  /// Whether flex items are forced onto one line or can wrap onto multiple
  /// lines
  #[declare(default)]
  pub wrap: bool,
  /// Sets how flex items are placed in the flex container defining the main
  /// axis and the direction
  #[declare(default)]
  pub direction: Direction,
  /// How the children should be placed along the cross axis in a flex layout.
  #[declare(default)]
  pub align_items: Align,
  /// How the children should be placed along the main axis in a flex layout.
  #[declare(default)]
  pub justify_content: JustifyContent,
  /// Define item between gap in main axis
  #[declare(default)]
  pub item_gap: f32,
  /// Define item between gap in cross axis
  #[declare(default)]
  pub line_gap: f32,
}

/// A type help to declare flex widget as horizontal.
pub struct Row;

/// A type help to declare flex widget as Vertical.
pub struct Column;

impl Declare for Row {
  type Builder = FlexDeclarer;
  fn declarer() -> Self::Builder { Flex::declarer().direction(Direction::Horizontal) }
}

impl Declare for Column {
  type Builder = FlexDeclarer;
  fn declarer() -> Self::Builder { Flex::declarer().direction(Direction::Vertical) }
}

impl Render for Flex {
  fn perform_layout(&self, clamp: BoxClamp, ctx: &mut LayoutCtx) -> Size {
    if Align::Stretch == self.align_items && self.wrap {
      warn!("stretch align and wrap property is conflict");
    }
    let direction = self.direction;
    let max_size = FlexSize::from_size(clamp.max, direction);
    let mut min_size = FlexSize::from_size(clamp.min, direction);
    if Align::Stretch == self.align_items {
      min_size.cross = max_size.cross;
    }
    let mut layouter = FlexLayouter {
      max: max_size,
      min: min_size,
      reverse: self.reverse,
      dir: direction,
      align_items: self.align_items,
      justify_content: self.justify_content,
      wrap: self.wrap,
      main_axis_gap: self.item_gap,
      cross_axis_gap: self.line_gap,
      current_line: <_>::default(),
      lines: vec![],
    };
    layouter.layout(ctx)
  }

  #[inline]
  fn paint(&self, _: &mut PaintingCtx) {}
}

#[derive(Debug, Clone, Copy, Default)]
struct FlexSize {
  main: f32,
  cross: f32,
}

impl FlexSize {
  fn to_size(self, dir: Direction) -> Size {
    match dir {
      Direction::Horizontal => Size::new(self.main, self.cross),
      Direction::Vertical => Size::new(self.cross, self.main),
    }
  }

  fn from_size(size: Size, dir: Direction) -> Self {
    match dir {
      Direction::Horizontal => Self { main: size.width, cross: size.height },
      Direction::Vertical => Self { cross: size.width, main: size.height },
    }
  }

  fn zero() -> Self { Self { main: 0., cross: 0. } }
}

impl std::ops::Sub for FlexSize {
  type Output = Self;
  fn sub(self, rhs: Self) -> Self::Output {
    FlexSize {
      main: self.main - rhs.main,
      cross: self.cross - rhs.cross,
    }
  }
}

struct FlexLayouter {
  max: FlexSize,
  min: FlexSize,
  reverse: bool,
  dir: Direction,
  align_items: Align,
  justify_content: JustifyContent,
  wrap: bool,
  current_line: MainLineInfo,
  lines: Vec<MainLineInfo>,
  main_axis_gap: f32,
  cross_axis_gap: f32,
}

impl FlexLayouter {
  fn layout(&mut self, ctx: &mut LayoutCtx) -> Size {
    self.perform_children_layout(ctx);
    self.flex_children_layout(ctx);

    // cross direction need calculate cross_axis_gap but last line don't need.
    let cross = self.lines.iter().fold(-self.cross_axis_gap, |sum, l| {
      sum + l.cross_line_height + self.cross_axis_gap
    });
    let main = match self.justify_content {
      JustifyContent::Start | JustifyContent::Center | JustifyContent::End => {
        self.lines.iter().fold(0f32, |max, l| max.max(l.main_width))
      }
      JustifyContent::SpaceBetween | JustifyContent::SpaceAround | JustifyContent::SpaceEvenly => {
        self.max.main
      }
    };
    let size = FlexSize { cross, main };
    let &mut Self { max, min, dir, .. } = self;
    let size = size.to_size(dir).clamp(min.to_size(dir), max.to_size(dir));
    self.update_children_position(FlexSize::from_size(size, dir), ctx);
    size
  }

  fn perform_children_layout(&mut self, ctx: &mut LayoutCtx) {
    // All children perform layout.
    let mut layouter = ctx.first_child_layouter();
    let &mut Self { max, min, wrap, dir, .. } = self;
    let min = if self.align_items == Align::Stretch {
      FlexSize { main: 0., cross: min.cross }
    } else {
      FlexSize::zero()
    };
    let mut gap = 0.;
    while let Some(mut l) = layouter {
      let mut max = max;
      if !wrap {
        max.main -= self.current_line.main_width;
      }

      let clamp = BoxClamp {
        max: max.to_size(dir),
        min: min.to_size(dir),
      };

      let size = l.perform_widget_layout(clamp);
      let size = FlexSize::from_size(size, dir);

      let mut flex = None;
      l.query_type(|expanded: &Expanded| flex = Some(expanded.flex));

      // flex-item need use empty space to resize after all fixed widget performed
      // layout.
      let line = &mut self.current_line;
      if let Some(flex) = flex {
        // expanded child size is zero, it don't need calculate
        if size.main > 0. {
          line.flex_sum += flex;
        }
        line.main_width += gap;
      } else {
        if wrap && !line.is_empty() && line.main_width + size.main > max.main {
          self.place_line();
        } else {
          line.main_width += gap;
        }

        let line = &mut self.current_line;
        line.main_width += size.main;
        line.cross_line_height = line.cross_line_height.max(size.cross);
      }

      self
        .current_line
        .items_info
        .push(FlexLayoutInfo { size, flex, pos: <_>::default() });

      layouter = l.into_next_sibling();
      if layouter.is_some() && !FlexLayouter::is_space_layout(self.justify_content) {
        gap = self.main_axis_gap;
      } else {
        gap = 0.;
      }
    }
    self.place_line();
  }

  fn is_space_layout(justify_content: JustifyContent) -> bool {
    matches!(
      justify_content,
      JustifyContent::SpaceAround | JustifyContent::SpaceBetween | JustifyContent::SpaceEvenly
    )
  }

  fn flex_children_layout(&mut self, ctx: &mut LayoutCtx) {
    let mut layouter = ctx.first_child_layouter();
    self.lines.iter_mut().for_each(|line| {
      let flex_unit = (self.max.main - line.main_width) / line.flex_sum;
      line.items_info.iter_mut().for_each(|info| {
        let mut l = layouter.take().unwrap();
        if info.size.main > 0. {
          if let Some(flex) = info.flex {
            let &mut Self { mut max, mut min, dir, .. } = self;
            let main = flex_unit * flex;
            max.main = main;
            min.main = main;
            let clamp = BoxClamp {
              max: max.to_size(dir),
              min: min.to_size(dir),
            };
            let size = l.perform_widget_layout(clamp);
            info.size = FlexSize::from_size(size, dir);
            line.main_width += info.size.main;
            line.cross_line_height = line.cross_line_height.max(info.size.cross);
          }
        }

        layouter = l.into_next_sibling();
      });
    });
  }

  fn update_children_position(&mut self, bound: FlexSize, ctx: &mut LayoutCtx) {
    let Self {
      reverse,
      dir,
      align_items,
      justify_content,
      lines,
      ..
    } = self;

    let cross_size = lines.iter().map(|l| l.cross_line_height).sum();
    // cross gap don't use calc offset
    let cross_gap_count = if !lines.is_empty() {
      (lines.len() - 1) as f32 * self.cross_axis_gap
    } else {
      0.
    };
    let cross_offset = align_items.align_value(cross_size, bound.cross - cross_gap_count);

    macro_rules! update_position {
      ($($rev: ident)?) => {
        let mut cross = cross_offset - self.cross_axis_gap;
        lines.iter_mut()$(.$rev())?.for_each(|line| {
          let (mut main, step) = line.place_args(bound.main, *justify_content, self.main_axis_gap);
          line.items_info.iter_mut()$(.$rev())?.for_each(|item| {
            let item_cross_offset =
              align_items.align_value(item.size.cross, line.cross_line_height);

            item.pos.cross = cross + item_cross_offset + self.cross_axis_gap;
            item.pos.main = main;
            main = main + item.size.main + step;
          });
          cross += line.cross_line_height + self.cross_axis_gap;
        });
      };
    }
    if *reverse {
      update_position!(rev);
    } else {
      update_position!();
    }

    let mut layouter = ctx.first_child_layouter();
    self.lines.iter_mut().for_each(|line| {
      line.items_info.iter_mut().for_each(|info| {
        let mut l = layouter.take().unwrap();
        l.update_position(info.pos.to_size(*dir).to_vector().to_point());
        layouter = l.into_next_sibling();
      })
    });
  }

  fn place_line(&mut self) {
    if !self.current_line.is_empty() {
      self.lines.push(std::mem::take(&mut self.current_line));
    }
  }
}

#[derive(Default)]
struct MainLineInfo {
  main_width: f32,
  items_info: Vec<FlexLayoutInfo>,
  flex_sum: f32,
  cross_line_height: f32,
}

struct FlexLayoutInfo {
  pos: FlexSize,
  size: FlexSize,
  flex: Option<f32>,
}

impl MainLineInfo {
  fn is_empty(&self) -> bool { self.items_info.is_empty() }

  fn place_args(&self, main_max: f32, justify_content: JustifyContent, gap: f32) -> (f32, f32) {
    if self.items_info.is_empty() {
      return (0., 0.);
    }

    let item_cnt = self.items_info.len() as f32;
    match justify_content {
      JustifyContent::Start => (0., gap),
      JustifyContent::Center => ((main_max - self.main_width) / 2., gap),
      JustifyContent::End => (main_max - self.main_width, gap),
      JustifyContent::SpaceAround => {
        let step = (main_max - self.main_width) / item_cnt;
        (step / 2., step)
      }
      JustifyContent::SpaceBetween => {
        let step = (main_max - self.main_width) / (item_cnt - 1.);
        (0., step)
      }
      JustifyContent::SpaceEvenly => {
        let step = (main_max - self.main_width) / (item_cnt + 1.);
        (step, step)
      }
    }
  }
}

#[cfg(test)]
mod tests {
  use super::*;
  use crate::prelude::*;
  use ribir_core::test_helper::*;
  use ribir_dev_helper::*;

  fn horizontal_line() -> impl WidgetBuilder {
    fn_widget! {
      @Flex {
        @{
          (0..10).map(|_| SizedBox { size: Size::new(10., 20.) })
        }
      }
    }
  }
  widget_layout_test!(horizontal_line, width == 100., height == 20.,);

  fn vertical_line() -> impl WidgetBuilder {
    fn_widget! {
      @Flex {
        direction: Direction::Vertical,
        @{ (0..10).map(|_| SizedBox { size: Size::new(10., 20.) })}
      }
    }
  }
  widget_layout_test!(vertical_line, width == 10., height == 200.,);

  fn row_wrap() -> impl WidgetBuilder {
    let size = Size::new(200., 20.);
    fn_widget! {
      @Flex {
        wrap: true,
        @{ (0..3).map(|_| SizedBox { size }) }
      }
    }
  }
  widget_layout_test!(
    row_wrap,
    wnd_size = Size::new(500., 500.),
    {path = [0], width == 400., height == 40.,}
    {path = [0, 0], width == 200., height == 20.,}
    {path = [0, 1], x == 200., width == 200., height == 20.,}
    {path = [0, 2], rect == ribir_geom::rect(0., 20., 200., 20.),}
  );

  fn reverse_row_wrap() -> impl WidgetBuilder {
    let size = Size::new(200., 20.);
    fn_widget! {
      @Flex {
        wrap: true,
        reverse: true,
        @{ (0..3).map(|_| SizedBox { size }) }
      }
    }
  }
  widget_layout_test!(
    reverse_row_wrap,
    wnd_size = Size::new(500., 500.),
    { path = [0], size == Size::new(400., 40.),}
    { path = [0,0], rect == ribir_geom::rect(200., 20., 200., 20.),}
    { path = [0, 1], rect == ribir_geom::rect(0., 20., 200., 20.),}
    { path = [0, 2], rect == ribir_geom::rect(0., 0., 200., 20.),}
  );

  fn main_axis_gap() -> impl WidgetBuilder {
    fn_widget! {
      @Row {
        item_gap: 15.,
        @SizedBox { size: Size::new(120., 20.) }
        @SizedBox { size: Size::new(80., 20.) }
        @SizedBox { size: Size::new(30., 20.) }
      }
    }
  }
  widget_layout_test!(
    main_axis_gap,
    wnd_size = Size::new(500., 40.),
    { path = [0, 0], rect == ribir_geom::rect(0., 0., 120., 20.),}
    { path = [0, 1], rect == ribir_geom::rect(135., 0., 80., 20.),}
    { path = [0, 2], rect == ribir_geom::rect(230., 0., 30., 20.),}
  );

  fn main_axis_reverse_gap() -> impl WidgetBuilder {
    fn_widget! {
      @Row {
        item_gap: 15.,
        reverse: true,
        @SizedBox { size: Size::new(120., 20.) }
        @SizedBox { size: Size::new(80., 20.) }
        @SizedBox { size: Size::new(30., 20.) }
      }
    }
  }
  widget_layout_test!(
    main_axis_reverse_gap,
    wnd_size = Size::new(500., 40.),
    { path = [0, 0], rect == ribir_geom::rect(140., 0., 120., 20.),}
    { path = [0, 1], rect == ribir_geom::rect(45., 0., 80., 20.),}
    { path = [0, 2], rect == ribir_geom::rect(0., 0., 30., 20.),}
  );

  fn main_axis_expand() -> impl WidgetBuilder {
    fn_widget! {
      @Row {
        item_gap: 15.,
        @SizedBox { size: Size::new(120., 20.) }
        @Expanded {
          flex: 1.,
          @SizedBox { size: Size::new(10., 20.) }
        }
        @SizedBox { size: Size::new(80., 20.) }
        @Expanded {
          flex: 2.,
          @SizedBox { size: Size::new(10., 20.) }
        }
        @SizedBox { size: Size::new(30., 20.) }
      }
    }
  }
  widget_layout_test!(
    main_axis_expand,
    wnd_size = Size::new(500., 40.),
    { path = [0, 0], rect == ribir_geom::rect(0., 0., 120., 20.),}
    { path = [0, 1], rect == ribir_geom::rect(135., 0., 70., 20.),}
    { path = [0, 2], rect == ribir_geom::rect(220., 0., 80., 20.),}
    { path = [0, 3], rect == ribir_geom::rect(315., 0., 140., 20.),}
    { path = [0, 4], rect == ribir_geom::rect(470., 0., 30., 20.),}
  );

  fn cross_axis_gap() -> impl WidgetBuilder {
    let size = Size::new(200., 20.);
    fn_widget! {
      @Flex {
        wrap: true,
        line_gap: 10.,
        align_items: Align::Center,
        @{ (0..3).map(|_| SizedBox { size }) }
      }
    }
  }
  widget_layout_test!(
    cross_axis_gap,
    wnd_size = Size::new(500., 500.),
    { path = [0], rect == ribir_geom::rect(0., 0., 400., 50.),}
    { path = [0, 0], rect == ribir_geom::rect(0., 0., 200., 20.),}
    { path = [0, 1], rect == ribir_geom::rect(200., 0., 200., 20.),}
    { path = [0, 2], rect == ribir_geom::rect(0., 30., 200., 20.),}
  );

  fn cross_align(align: Align) -> impl WidgetBuilder {
    fn_widget! {
      @Row {
        align_items: align,
        @SizedBox { size: Size::new(100., 20.) }
        @SizedBox { size: Size::new(100., 30.) }
        @SizedBox { size: Size::new(100., 40.) }
      }
    }
  }

  fn start_cross_align() -> impl WidgetBuilder { cross_align(Align::Start) }
  widget_layout_test!(
    start_cross_align,
    { path =[0],  width == 300., height == 40., }
    { path =[0, 0],  rect == ribir_geom::rect(0., 0., 100., 20.),}
    { path =[0, 1],  rect == ribir_geom::rect(100., 0., 100., 30.),}
    { path =[0, 2],  rect == ribir_geom::rect(200., 0., 100., 40.),}
  );

  fn center_cross_align() -> impl WidgetBuilder { cross_align(Align::Center) }
  widget_layout_test!(
    center_cross_align,
    { path =[0],  width == 300., height == 40., }
    { path =[0, 0],  rect == ribir_geom::rect(0., 10., 100., 20.),}
    { path =[0, 1],  rect == ribir_geom::rect(100., 5., 100., 30.),}
    { path =[0, 2],  rect == ribir_geom::rect(200., 0., 100., 40.),}
  );

  fn end_cross_align() -> impl WidgetBuilder { cross_align(Align::End) }
  widget_layout_test!(
    end_cross_align,
    { path =[0],  width == 300., height == 40., }
    { path =[0, 0],  rect == ribir_geom::rect(0., 20., 100., 20.),}
    { path =[0, 1],  rect == ribir_geom::rect(100., 10., 100., 30.),}
    { path =[0, 2],  rect == ribir_geom::rect(200., 0., 100., 40.),}
  );

  fn stretch_cross_align() -> impl WidgetBuilder { cross_align(Align::Stretch) }
  widget_layout_test!(
    stretch_cross_align,
    wnd_size = Size::new(500., 40.),
    { path =[0],  width == 300., height == 40., }
    { path =[0, 0],  rect == ribir_geom::rect(0., 0., 100., 40.),}
    { path =[0, 1],  rect == ribir_geom::rect(100., 0., 100., 40.),}
    { path =[0, 2],  rect == ribir_geom::rect(200., 0., 100., 40.),}
  );

  fn main_align(justify_content: JustifyContent) -> impl WidgetBuilder {
    let item_size = Size::new(100., 20.);
    fn_widget! {
      @SizedBox {
        size: Size::new(500., 500.),
        @Row {
          justify_content,
          align_items: Align::Start,
          @SizedBox { size: item_size }
          @SizedBox { size: item_size }
          @SizedBox { size: item_size }
        }
      }
    }
  }

  fn start_main_align() -> impl WidgetBuilder { main_align(JustifyContent::Start) }
  widget_layout_test!(
    start_main_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 0.,}
    { path =[0, 0, 1], x == 100.,}
    { path =[0, 0, 2], x == 200.,}
  );

  fn center_main_align() -> impl WidgetBuilder { main_align(JustifyContent::Center) }
  widget_layout_test!(
    center_main_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 100.,}
    { path =[0, 0, 1], x == 200.,}
    { path =[0, 0, 2], x == 300.,}
  );

  fn end_main_align() -> impl WidgetBuilder { main_align(JustifyContent::End) }
  widget_layout_test!(
    end_main_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 200.,}
    { path =[0, 0, 1], x == 300.,}
    { path =[0, 0, 2], x == 400.,}
  );

  fn space_between_align() -> impl WidgetBuilder { main_align(JustifyContent::SpaceBetween) }
  widget_layout_test!(
    space_between_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 0.,}
    { path =[0, 0, 1], x == 200.,}
    { path =[0, 0, 2], x == 400.,}
  );

  fn space_around_align() -> impl WidgetBuilder { main_align(JustifyContent::SpaceAround) }
  const AROUND_SPACE: f32 = 200.0 / 3.0;
  widget_layout_test!(
    space_around_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 0.5 * AROUND_SPACE,}
    { path =[0, 0, 1], x == 100. + AROUND_SPACE * 1.5,}
    { path =[0, 0, 2], x == 2.5 * AROUND_SPACE+ 200.,}
  );

  fn space_evenly_align() -> impl WidgetBuilder { main_align(JustifyContent::SpaceEvenly) }
  widget_layout_test!(
    space_evenly_align,
    wnd_size = Size::new(500., 500.),
    { path =[0, 0], width == 500., height == 500.,}
    { path =[0, 0, 0], x == 50.,}
    { path =[0, 0, 1], x == 200.,}
    { path =[0, 0, 2], x == 350.,}
  );

  fn flex_expand() -> impl WidgetBuilder {
    fn_widget! {
      @SizedBox {
        size: Size::new(500., 25.),
        @Flex {
          direction: Direction::Horizontal,
          @Expanded {
            flex: 1.,
            @SizedBox { size: INFINITY_SIZE,}
          }
          @SizedBox { size: Size::new(100., 20.) }
          @Expanded {
            flex: 3.,
            @SizedBox { size: INFINITY_SIZE, }
          }
        }
      }
    }
  }
  widget_layout_test!(
    flex_expand,
    wnd_size = Size::new(500., 500.),
    { path = [0, 0], rect == ribir_geom::rect(0., 0., 500., 25.),}
    { path = [0, 0, 0], rect == ribir_geom::rect(0., 0., 100., 25.),}
    { path = [0, 0, 2], rect == ribir_geom::rect(200., 0., 300., 25.),}
  );
}