use crate::*;

#[derive(Clone, Debug, Default, PartialEq)]
#[cfg_attr(feature = "persistence", derive(serde::Deserialize, serde::Serialize))]
pub(crate) struct State {
    col_widths: Vec<f32>,
    row_heights: Vec<f32>,
}

impl State {
    fn set_min_col_width(&mut self, col: usize, width: f32) {
        self.col_widths
            .resize(self.col_widths.len().max(col + 1), 0.0);
        self.col_widths[col] = self.col_widths[col].max(width);
    }

    fn set_min_row_height(&mut self, row: usize, height: f32) {
        self.row_heights
            .resize(self.row_heights.len().max(row + 1), 0.0);
        self.row_heights[row] = self.row_heights[row].max(height);
    }

    fn col_width(&self, col: usize) -> Option<f32> {
        self.col_widths.get(col).copied()
    }

    fn row_height(&self, row: usize) -> Option<f32> {
        self.row_heights.get(row).copied()
    }

    fn full_width(&self, x_spacing: f32) -> f32 {
        self.col_widths.iter().sum::<f32>()
            + (self.col_widths.len().at_least(1) - 1) as f32 * x_spacing
    }
}

// ----------------------------------------------------------------------------

pub(crate) struct GridLayout {
    ctx: CtxRef,
    id: Id,

    /// State previous frame (if any).
    /// This can be used to predict future sizes of cells.
    prev_state: State,
    /// State accumulated during the current frame.
    curr_state: State,

    spacing: Vec2,

    striped: bool,
    initial_x: f32,
    min_cell_size: Vec2,
    col: usize,
    row: usize,
}

impl GridLayout {
    pub(crate) fn new(ui: &Ui, id: Id) -> Self {
        let prev_state = ui.memory().grid.get(&id).cloned().unwrap_or_default();

        Self {
            ctx: ui.ctx().clone(),
            id,
            prev_state,
            curr_state: State::default(),
            spacing: ui.spacing().item_spacing,
            striped: false,
            initial_x: ui.cursor().x,
            min_cell_size: ui.spacing().interact_size,
            col: 0,
            row: 0,
        }
    }
}

impl GridLayout {
    fn prev_col_width(&self, col: usize) -> f32 {
        self.prev_state
            .col_width(col)
            .unwrap_or(self.min_cell_size.x)
    }
    fn prev_row_height(&self, row: usize) -> f32 {
        self.prev_state
            .row_height(row)
            .unwrap_or(self.min_cell_size.y)
    }

    pub(crate) fn available_rect(&self, region: &Region) -> Rect {
        // let mut rect = Rect::from_min_max(region.cursor, region.max_rect.max);
        // rect.set_height(rect.height().at_least(self.min_cell_size.y));
        // rect

        // required for putting CollapsingHeader in anything but the last column:
        self.available_rect_finite(region)
    }

    pub(crate) fn available_rect_finite(&self, region: &Region) -> Rect {
        // If we want to allow width-filling widgets like `Separator` in one of the first cells
        // then we need to make sure they don't spill out of the first cell:
        let width = self.prev_state.col_width(self.col);
        let width = width.or_else(|| self.curr_state.col_width(self.col));
        let width = width.unwrap_or_default().at_least(self.min_cell_size.x);

        let height = region.max_rect_finite().max.y - region.cursor.y;
        let height = height.at_least(self.min_cell_size.y);

        Rect::from_min_size(region.cursor, vec2(width, height))
    }

    pub(crate) fn next_cell(&self, cursor: Pos2, child_size: Vec2) -> Rect {
        let width = self.prev_state.col_width(self.col).unwrap_or(0.0);
        let height = self.prev_row_height(self.row);
        let size = child_size.max(vec2(width, height));
        Rect::from_min_size(cursor, size)
    }

    pub(crate) fn align_size_within_rect(&self, size: Vec2, frame: Rect) -> Rect {
        // TODO: allow this alignment to be customized
        Align2::LEFT_CENTER.align_size_within_rect(size, frame)
    }

    pub(crate) fn justify_or_align(&self, frame: Rect, size: Vec2) -> Rect {
        self.align_size_within_rect(size, frame)
    }

    pub(crate) fn advance(&mut self, cursor: &mut Pos2, frame_rect: Rect, widget_rect: Rect) {
        let debug_expand_width = self.ctx.style().visuals.debug_expand_width;
        let debug_expand_height = self.ctx.style().visuals.debug_expand_height;
        if debug_expand_width || debug_expand_height {
            let rect = widget_rect;
            let too_wide = rect.width() > self.prev_col_width(self.col);
            let too_high = rect.height() > self.prev_row_height(self.row);

            if (debug_expand_width && too_wide) || (debug_expand_height && too_high) {
                let painter = self.ctx.debug_painter();
                painter.rect_stroke(rect, 0.0, (1.0, Color32::LIGHT_BLUE));

                let stroke = Stroke::new(2.5, Color32::from_rgb(200, 0, 0));
                let paint_line_seg = |a, b| painter.line_segment([a, b], stroke);

                if debug_expand_width && too_wide {
                    paint_line_seg(rect.left_top(), rect.left_bottom());
                    paint_line_seg(rect.left_center(), rect.right_center());
                    paint_line_seg(rect.right_top(), rect.right_bottom());
                }
            }
        }

        self.curr_state
            .set_min_col_width(self.col, widget_rect.width().at_least(self.min_cell_size.x));
        self.curr_state.set_min_row_height(
            self.row,
            widget_rect.height().at_least(self.min_cell_size.y),
        );

        self.col += 1;
        cursor.x += frame_rect.width() + self.spacing.x;
    }

    pub(crate) fn end_row(&mut self, cursor: &mut Pos2, painter: &Painter) {
        let row_height = self.prev_row_height(self.row);

        cursor.x = self.initial_x;
        cursor.y += row_height + self.spacing.y;
        self.col = 0;
        self.row += 1;

        if self.striped && self.row % 2 == 1 {
            if let Some(height) = self.prev_state.row_height(self.row) {
                // Paint background for coming row:
                let size = Vec2::new(self.prev_state.full_width(self.spacing.x), height);
                let rect = Rect::from_min_size(*cursor, size);
                let rect = rect.expand2(0.5 * self.spacing.y * Vec2::Y);
                let rect = rect.expand2(2.0 * Vec2::X); // HACK: just looks better with some spacing on the sides
                let color = Rgba::from_white_alpha(0.0075);
                // let color = Rgba::from_black_alpha(0.2);
                painter.rect_filled(rect, 2.0, color);
            }
        }
    }

    pub(crate) fn save(&self) {
        if self.curr_state != self.prev_state {
            self.ctx
                .memory()
                .grid
                .insert(self.id, self.curr_state.clone());
            self.ctx.request_repaint();
        }
    }
}

// ----------------------------------------------------------------------------

/// A simple grid layout.
///
/// The contents of each cell be aligned to the left and center.
/// If you want to add multiple widgets to a cell you need to group them with
/// [`Ui::horizontal`], [`Ui::vertical`] etc.
///
/// ```
/// # let ui = &mut egui::Ui::__test();
/// egui::Grid::new("some_unique_id").show(ui, |ui| {
///     ui.label("First row, first column");
///     ui.label("First row, second column");
///     ui.end_row();
///
///     ui.label("Second row, first column");
///     ui.label("Second row, second column");
///     ui.label("Second row, third column");
///     ui.end_row();
///
///     ui.horizontal(|ui| { ui.label("Same"); ui.label("cell"); });
///     ui.label("Third row, second column");
///     ui.end_row();
/// });
/// ```
pub struct Grid {
    id_source: Id,
    striped: bool,
    min_col_width: Option<f32>,
    min_row_height: Option<f32>,
    spacing: Option<Vec2>,
}

impl Grid {
    /// Create a new [`Grid`] with a locally unique identifier.
    pub fn new(id_source: impl std::hash::Hash) -> Self {
        Self {
            id_source: Id::new(id_source),
            striped: false,
            min_col_width: None,
            min_row_height: None,
            spacing: None,
        }
    }

    /// If `true`, add a subtle background color to every other row.
    ///
    /// This can make a table easier to read.
    /// Default: `false`.
    pub fn striped(mut self, striped: bool) -> Self {
        self.striped = striped;
        self
    }

    /// Set minimum width of each column.
    /// Default: [`crate::style::Spacing::interact_size`]`.x`.
    pub fn min_col_width(mut self, min_col_width: f32) -> Self {
        self.min_col_width = Some(min_col_width);
        self
    }

    /// Set minimum height of each row.
    /// Default: [`crate::style::Spacing::interact_size`]`.y`.
    pub fn min_row_height(mut self, min_row_height: f32) -> Self {
        self.min_row_height = Some(min_row_height);
        self
    }

    /// Set spacing between columns/rows.
    /// Default: [`crate::style::Spacing::item_spacing`].
    pub fn spacing(mut self, spacing: impl Into<Vec2>) -> Self {
        self.spacing = Some(spacing.into());
        self
    }
}

impl Grid {
    pub fn show<R>(self, ui: &mut Ui, add_contents: impl FnOnce(&mut Ui) -> R) -> R {
        let Self {
            id_source,
            striped,
            min_col_width,
            min_row_height,
            spacing,
        } = self;
        let min_col_width = min_col_width.unwrap_or_else(|| ui.spacing().interact_size.x);
        let min_row_height = min_row_height.unwrap_or_else(|| ui.spacing().interact_size.y);
        let spacing = spacing.unwrap_or_else(|| ui.spacing().item_spacing);

        // Each grid cell is aligned LEFT_CENTER.
        // If somebody wants to wrap more things inside a cell,
        // then we should pick a default layout that matches that alignment,
        // which we do here:
        ui.horizontal(|ui| {
            let id = ui.make_persistent_id(id_source);
            let grid = GridLayout {
                striped,
                spacing,
                min_cell_size: vec2(min_col_width, min_row_height),
                ..GridLayout::new(ui, id)
            };

            ui.set_grid(grid);
            let r = add_contents(ui);
            ui.save_grid();
            r
        })
        .0
    }
}