termint 0.8.0

use std::{
    cmp::{max, min},
    hash::{DefaultHasher, Hash, Hasher},
};

mod layout_node;
mod layouting;

pub use layout_node::LayoutNode;
pub use layouting::*;

use crate::{
    buffer::Buffer,
    enums::Color,
    geometry::Padding,
    prelude::{Constraint, Direction, Rect, Vec2},
    style::Style,
    widgets::{Element, Widget},
};

/// A container widget that arranges child widgets in a single direction
/// (horizontal or vertical), flexing their sizes based on given constraints.
///
/// # Direction
///
/// The layout can be horizontal (left-to-right) or vertical (top-to-bottom).
/// This determines the axis along which the children are arranged.
///
/// # Constraints
///
/// Each child widget's size is controlled by a [`Constraint`] determining how
/// space is allocated. You can learn more about [`Constraint`] in its
/// documentation.
///
/// # Example
/// ```rust
/// use termint::prelude::*;
///
/// # type AnyWidget = Spacer;
/// # type OtherWidget = Spacer;
/// // Creates a horizontal layout
/// let mut layout = Layout::<()>::horizontal();
/// // Pushes a child with minimum size 1
/// layout.push("Left", 1..);
/// // Pushes another child filling the rest of the space
/// layout.push("Right", Constraint::Fill(1));
/// ```
#[derive(Debug)]
pub struct Layout<M: 'static = ()> {
    direction: Direction,
    children: Vec<Element<M>>,
    constraints: Vec<Constraint>,
    style: Style,
    padding: Padding,
    center: bool,
}

impl<M> Layout<M> {
    /// Creates a new [`Layout`] that flexes in given [`Direction`].
    ///
    /// # Example
    ///
    /// ```rust
    /// use termint::prelude::*;
    ///
    /// // Layout flexing horizontally
    /// let h = Layout::<()>::new(Direction::Horizontal);
    /// // Layout flexing vertically
    /// let v = Layout::<()>::new(Direction::Vertical);
    /// ```
    #[must_use]
    pub fn new(direction: Direction) -> Self {
        Self {
            direction,
            ..Default::default()
        }
    }

    /// Creates a new vertical [`Layout`] (top-to-bottom).
    ///
    /// This is a convenience constructor equivalent to
    /// `Layout::new(Direction::Vertical)`.
    #[must_use]
    pub fn vertical() -> Self {
        Default::default()
    }

    /// Creates a new horizontal [`Layout`] (left-to-right).
    ///
    /// This is a convenience constructor equivalent to
    /// `Layout::new(Direction::Horizontal)`.
    #[must_use]
    pub fn horizontal() -> Self {
        Self {
            direction: Direction::Horizontal,
            ..Default::default()
        }
    }

    /// Sets flexing [`Direction`] of the [`Layout`].
    #[must_use]
    pub fn direction(mut self, direction: Direction) -> Self {
        self.direction = direction;
        self
    }

    /// Sets the base style of the [`Layout`].
    ///
    /// The `style` can be any type convertible to [`Style`].
    #[must_use]
    pub fn style<T>(mut self, style: T) -> Self
    where
        T: Into<Style>,
    {
        self.style = style.into();
        self
    }

    /// Sets base background color of the [`Layout`].
    ///
    /// The `bg` can be any type convertible into `Option<Color>`. If `None` is
    /// supplied, the background is transparent.
    #[must_use]
    pub fn bg<T>(mut self, bg: T) -> Self
    where
        T: Into<Option<Color>>,
    {
        self.style = self.style.bg(bg);
        self
    }

    /// Sets base foreground color of the [`Layout`].
    ///
    /// The `fg` can be any type convertible into `Option<Color>`. If `None` is
    /// supplied, it keeps the original foreground color.
    #[must_use]
    pub fn fg<T>(mut self, fg: T) -> Self
    where
        T: Into<Option<Color>>,
    {
        self.style = self.style.fg(fg);
        self
    }

    /// Sets the [`Padding`] of the [`Layout`].
    ///
    /// The `padding` can be any type convertible into [`Padding`], such as
    /// `usize` (uniform), `(usize, usize)` (vertical, horizontal). You can
    /// read more in the [`Padding`] documentation.
    #[must_use]
    pub fn padding<T>(mut self, padding: T) -> Self
    where
        T: Into<Padding>,
    {
        self.padding = padding.into();
        self
    }

    /// Centers the content within the [`Layout`] in the flexing direction.
    ///
    /// If the layout is flexing its children horizontally, the content will
    /// be centered horizontally (left-to-right). Otherwise it will be centered
    /// vertically (top-to-bottom).
    #[must_use]
    pub fn center(mut self) -> Self {
        self.center = true;
        self
    }

    /// Adds a child widget with its constraint.
    ///
    /// The `child` is any type convertible into [`Element`].
    ///
    /// The `constraint` is any type convertible into [`Constraint`], such as
    /// `usize` (fixed length), `RangeFrom` (e.g. `1..` equals to
    /// `Constraint::Min(1)`).
    pub fn push<T, C>(&mut self, child: T, constraint: C)
    where
        T: Into<Element<M>>,
        C: Into<Constraint>,
    {
        self.children.push(child.into());
        self.constraints.push(constraint.into());
    }
}

impl<M: Clone + 'static> Widget<M> for Layout<M> {
    fn render(&self, buffer: &mut Buffer, layout: &LayoutNode) {
        self.render_base_style(buffer, &layout.area);

        for (i, child) in self.children.iter().enumerate() {
            child.render(buffer, &layout.children[i]);
        }
    }

    fn height(&self, size: &Vec2) -> usize {
        let size = Vec2::new(
            size.x.saturating_sub(self.padding.get_horizontal()),
            size.y.saturating_sub(self.padding.get_vertical()),
        );
        let height = match self.direction {
            Direction::Vertical => {
                self.size_sd(&size, size.y, |c, s| c.height(s))
            }
            Direction::Horizontal => self.hor_height(&size),
        };
        height + self.padding.get_vertical()
    }

    fn width(&self, size: &Vec2) -> usize {
        let size = Vec2::new(
            size.x.saturating_sub(self.padding.get_horizontal()),
            size.y.saturating_sub(self.padding.get_vertical()),
        );
        let width = match self.direction {
            Direction::Vertical => self.ver_width(&size),
            Direction::Horizontal => {
                self.size_sd(&size, size.x, |c, s| c.width(s))
            }
        };
        width + self.padding.get_horizontal()
    }

    fn children(&self) -> Vec<&Element<M>> {
        self.children.iter().collect()
    }

    fn layout_hash(&self) -> u64 {
        let mut hasher = DefaultHasher::new();

        self.direction.hash(&mut hasher);
        self.constraints.hash(&mut hasher);
        self.padding.hash(&mut hasher);
        self.center.hash(&mut hasher);

        hasher.finish()
    }

    fn layout(&self, node: &mut LayoutNode, area: Rect) {
        if !node.is_dirty && !node.has_dirty_child && node.area == area {
            return;
        }

        node.area = area;
        let rect = area.inner(self.padding);
        match self.direction {
            Direction::Vertical => self.layout_ver(node, rect),
            Direction::Horizontal => self.layout_hor(node, rect),
        };

        node.is_dirty = false;
        node.has_dirty_child = false;
    }
}

impl<M> Default for Layout<M> {
    fn default() -> Self {
        Self {
            direction: Direction::Vertical,
            children: Vec::new(),
            constraints: Vec::new(),
            style: Style::new(),
            padding: Default::default(),
            center: false,
        }
    }
}

impl<M: Clone + 'static> Layout<M> {
    fn layout_ver(&self, node: &mut LayoutNode, area: Rect) {
        let (sizes, mut rect) = self.ver_sizes(area);

        for (i, s) in sizes.iter().enumerate() {
            let csize = min(*s, rect.height());
            let crect =
                Rect::from_coords(*rect.pos(), Vec2::new(rect.width(), csize));

            self.children[i].layout(&mut node.children[i], crect);
            rect = rect.inner(Padding::top(csize));
        }
    }

    fn layout_hor(&self, node: &mut LayoutNode, area: Rect) {
        let (sizes, mut rect) = self.hor_sizes(area);

        for (i, s) in sizes.iter().enumerate() {
            let csize = min(*s, rect.width());
            let crect = Rect::from_coords(
                *rect.pos(),
                Vec2::new(csize, rect.height()),
            );

            self.children[i].layout(&mut node.children[i], crect);
            rect = rect.inner(Padding::left(csize));
        }
    }

    /// Gets child sizes of vertical layout
    fn ver_sizes(&self, rect: Rect) -> (Vec<usize>, Rect) {
        self.child_sizes(
            rect,
            rect.height(),
            |c, s| c.height(s),
            |s, v| s.y = s.y.saturating_sub(v),
            |s| s.y,
            |r, s| r.inner(Padding::vertical(s)),
        )
    }

    /// Gets child sizes of horizontal layout
    fn hor_sizes(&self, rect: Rect) -> (Vec<usize>, Rect) {
        self.child_sizes(
            rect,
            rect.width(),
            |c, s| c.width(s),
            |s, v| s.x = s.x.saturating_sub(v),
            |s| s.x,
            |r, s| r.inner(Padding::horizontal(s)),
        )
    }

    /// Gets sizes of all the children
    fn child_sizes<F1, F2, F3, F4>(
        &self,
        rect: Rect,
        percent: usize,
        csize: F1,
        shrink: F2,
        left: F3,
        inner: F4,
    ) -> (Vec<usize>, Rect)
    where
        F1: Fn(&Element<M>, &Vec2) -> usize,
        F2: Fn(&mut Vec2, usize),
        F3: Fn(Vec2) -> usize,
        F4: Fn(Rect, usize) -> Rect,
    {
        let mut fill_ids = Vec::new();
        let mut fills = 0;
        let mut sizes = Vec::new();
        let mut size = *rect.size();

        for (i, constraint) in self.constraints.iter().enumerate() {
            let csize = match constraint {
                Constraint::Length(len) => *len,
                Constraint::Percent(p) => percent * p / 100,
                Constraint::Min(l) => max(csize(&self.children[i], &size), *l),
                Constraint::Max(h) => min(csize(&self.children[i], &size), *h),
                Constraint::MinMax(l, h) => {
                    min(max(csize(&self.children[i], &size), *l), *h)
                }
                Constraint::Fill(val) => {
                    fill_ids.push(sizes.len());
                    sizes.push(*val);
                    fills += val;
                    continue;
                }
            };
            sizes.push(csize);
            shrink(&mut size, csize);
        }

        let mut left = left(size);
        if fills == 0 && self.center {
            return (sizes, inner(rect, left / 2));
        }

        for f in fill_ids {
            let fill = sizes[f];
            sizes[f] = left / fills * fill;
            fills -= fill;
            left -= sizes[f];
        }
        (sizes, rect)
    }

    /// Renders [`Layout`] base style
    fn render_base_style(&self, buffer: &mut Buffer, rect: &Rect) {
        for pos in rect.into_iter() {
            buffer.set_style(self.style, &pos);
            if self.style.bg.is_some() {
                buffer.set_char(' ', &pos);
            }
        }
    }

    fn size_sd<F>(&self, size: &Vec2, prim: usize, csize: F) -> usize
    where
        F: Fn(&Element<M>, &Vec2) -> usize,
    {
        let mut total = 0;
        let mut fill = false;
        for (i, constraint) in self.constraints.iter().enumerate() {
            match constraint {
                Constraint::Length(len) => total += len,
                Constraint::Percent(p) => total += prim * p / 100,
                Constraint::Min(l) => {
                    total += max(*l, csize(&self.children[i], size))
                }
                Constraint::Max(h) => {
                    total += min(*h, csize(&self.children[i], size))
                }
                Constraint::MinMax(l, h) => {
                    total += min(*h, max(*l, csize(&self.children[i], size)))
                }
                Constraint::Fill(_) => fill = true,
            }
        }
        if fill {
            return max(prim, total);
        }
        total
    }

    fn ver_width(&self, size: &Vec2) -> usize {
        let mut width = 0;
        let mut total = 0;
        let mut total_fills = 0;
        let mut fills = Vec::new();
        for (i, constraint) in self.constraints.iter().enumerate() {
            let csize = match constraint {
                Constraint::Length(len) => *len,
                Constraint::Percent(p) => size.y * p / 100,
                Constraint::Min(l) => max(*l, self.children[i].height(size)),
                Constraint::Max(h) => min(*h, self.children[i].height(size)),
                Constraint::MinMax(l, h) => {
                    min(*h, max(*l, self.children[i].height(size)))
                }
                Constraint::Fill(f) => {
                    total_fills += f;
                    fills.push((&self.children[i], f));
                    continue;
                }
            };
            total += csize;
            width =
                width.max(self.children[i].width(&Vec2::new(size.x, csize)));
        }

        let mut left = Vec2::new(size.x, size.y.saturating_sub(total));
        for (child, f) in fills {
            let h = left.y / total_fills * f;
            width = width.max(child.width(&left));
            left.y -= h;
            total_fills -= f;
        }
        width
    }

    fn hor_height(&self, size: &Vec2) -> usize {
        let mut height = 0;
        let mut total = 0;
        let mut total_fills = 0;
        let mut fills = Vec::new();
        for (i, constraint) in self.constraints.iter().enumerate() {
            let csize = match constraint {
                Constraint::Length(len) => *len,
                Constraint::Percent(p) => size.y * p / 100,
                Constraint::Min(l) => max(*l, self.children[i].width(size)),
                Constraint::Max(h) => min(*h, self.children[i].width(size)),
                Constraint::MinMax(l, h) => {
                    min(*h, max(*l, self.children[i].width(size)))
                }
                Constraint::Fill(f) => {
                    total_fills += f;
                    fills.push((&self.children[i], f));
                    continue;
                }
            };
            total += csize;
            height =
                height.max(self.children[i].height(&Vec2::new(csize, size.y)));
        }

        let mut left = Vec2::new(size.x, size.y.saturating_sub(total));
        for (child, f) in fills {
            let h = left.y / total_fills * f;
            height = height.max(child.width(&left));
            left.y -= h;
            total_fills -= f;
        }
        height
    }
}

// From implementations
impl<M: Clone + 'static> From<Layout<M>> for Box<dyn Widget<M>> {
    fn from(value: Layout<M>) -> Self {
        Box::new(value)
    }
}

impl<M: Clone + 'static> From<Layout<M>> for Element<M> {
    fn from(value: Layout<M>) -> Self {
        Element::new(value)
    }
}