use crate::{prelude::*, widgets::Block};

mod bar;
mod bar_group;

pub use bar::Bar;
pub use bar_group::BarGroup;

/// A chart showing values as [bars](Bar).
///
/// Here is a possible `BarChart` output.
/// ```plain
/// ┌─────────────────────────────────┐
/// │                             ████│
/// │                        ▅▅▅▅ ████│
/// │            ▇▇▇▇        ████ ████│
/// │     ▄▄▄▄   ████ ████   ████ ████│
/// │▆10▆ █20█   █50█ █40█   █60█ █90█│
/// │ B1   B2     B1   B2     B1   B2 │
/// │ Group1      Group2      Group3  │
/// └─────────────────────────────────┘
/// ```
///
/// A `BarChart` is composed of a set of [`Bar`] which can be set via [`BarChart::data`].
/// Bars can be styled globally ([`BarChart::bar_style`]) or individually ([`Bar::style`]).
/// There are other methods available to style even more precisely. See [`Bar`] to find out about
/// each bar component.
///
/// The `BarChart` widget can also show groups of bars via [`BarGroup`].
/// A [`BarGroup`] is a set of [`Bar`], multiple can be added to a `BarChart` using
/// [`BarChart::data`] multiple time as demonstrated in the example below.
///
/// The chart can have a [`Direction`] (by default the bars are [`Vertical`](Direction::Vertical)).
/// This is set using [`BarChart::direction`].
///
/// Note: this is the only widget that doesn't implement `Widget` for `&T` because the current
/// implementation modifies the internal state of self. This will be fixed in the future.
///
/// # Examples
///
/// The following example creates a `BarChart` with two groups of bars.
/// The first group is added by an array slice (`&[(&str, u64)]`).
/// The second group is added by a [`BarGroup`] instance.
/// ```
/// use ratatui::{prelude::*, widgets::*};
///
/// BarChart::default()
///     .block(Block::default().title("BarChart").borders(Borders::ALL))
///     .bar_width(3)
///     .bar_gap(1)
///     .group_gap(3)
///     .bar_style(Style::new().yellow().on_red())
///     .value_style(Style::new().red().bold())
///     .label_style(Style::new().white())
///     .data(&[("B0", 0), ("B1", 2), ("B2", 4), ("B3", 3)])
///     .data(BarGroup::default().bars(&[Bar::default().value(10), Bar::default().value(20)]))
///     .max(4);
/// ```
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub struct BarChart<'a> {
    /// Block to wrap the widget in
    block: Option<Block<'a>>,
    /// The width of each bar
    bar_width: u16,
    /// The gap between each bar
    bar_gap: u16,
    /// The gap between each group
    group_gap: u16,
    /// Set of symbols used to display the data
    bar_set: symbols::bar::Set,
    /// Style of the bars
    bar_style: Style,
    /// Style of the values printed at the bottom of each bar
    value_style: Style,
    /// Style of the labels printed under each bar
    label_style: Style,
    /// Style for the widget
    style: Style,
    /// vector of groups containing bars
    data: Vec<BarGroup<'a>>,
    /// Value necessary for a bar to reach the maximum height (if no value is specified,
    /// the maximum value in the data is taken as reference)
    max: Option<u64>,
    /// direction of the bars
    direction: Direction,
}

impl<'a> Default for BarChart<'a> {
    fn default() -> Self {
        Self {
            block: None,
            max: None,
            data: Vec::new(),
            bar_style: Style::default(),
            bar_width: 1,
            bar_gap: 1,
            value_style: Style::default(),
            label_style: Style::default(),
            group_gap: 0,
            bar_set: symbols::bar::NINE_LEVELS,
            style: Style::default(),
            direction: Direction::Vertical,
        }
    }
}

impl<'a> BarChart<'a> {
    /// Add group of bars to the `BarChart`
    ///
    /// # Examples
    ///
    /// The following example creates a `BarChart` with two groups of bars.
    /// The first group is added by an array slice (`&[(&str, u64)]`).
    /// The second group is added by a [`BarGroup`] instance.
    /// ```
    /// # use ratatui::{prelude::*, widgets::*};
    /// BarChart::default()
    ///     .data(&[("B0", 0), ("B1", 2), ("B2", 4), ("B3", 3)])
    ///     .data(BarGroup::default().bars(&[Bar::default().value(10), Bar::default().value(20)]));
    /// ```
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn data(mut self, data: impl Into<BarGroup<'a>>) -> Self {
        let group: BarGroup = data.into();
        if !group.bars.is_empty() {
            self.data.push(group);
        }
        self
    }

    /// Surround the [`BarChart`] with a [`Block`].
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn block(mut self, block: Block<'a>) -> Self {
        self.block = Some(block);
        self
    }

    /// Set the value necessary for a [`Bar`] to reach the maximum height.
    ///
    /// If not set, the maximum value in the data is taken as reference.
    ///
    /// # Examples
    ///
    /// This example shows the default behavior when `max` is not set.
    /// The maximum value in the dataset is taken (here, `100`).
    /// ```
    /// # use ratatui::{prelude::*, widgets::*};
    /// BarChart::default().data(&[("foo", 1), ("bar", 2), ("baz", 100)]);
    /// // Renders
    /// //     █
    /// //     █
    /// // f b b
    /// ```
    ///
    /// This example shows a custom max value.
    /// The maximum height being `2`, `bar` & `baz` render as the max.
    /// ```
    /// # use ratatui::{prelude::*, widgets::*};
    /// BarChart::default()
    ///     .data(&[("foo", 1), ("bar", 2), ("baz", 100)])
    ///     .max(2);
    /// // Renders
    /// //   █ █
    /// // █ █ █
    /// // f b b
    /// ```
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn max(mut self, max: u64) -> Self {
        self.max = Some(max);
        self
    }

    /// Set the default style of the bar.
    ///
    /// `style` accepts any type that is convertible to [`Style`] (e.g. [`Style`], [`Color`], or
    /// your own type that implements [`Into<Style>`]).
    ///
    /// It is also possible to set individually the style of each [`Bar`].
    /// In this case the default style will be patched by the individual style
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn bar_style<S: Into<Style>>(mut self, style: S) -> Self {
        self.bar_style = style.into();
        self
    }

    /// Set the width of the displayed bars.
    ///
    /// For [`Horizontal`](crate::layout::Direction::Horizontal) bars this becomes the height of
    /// the bar.
    ///
    /// If not set, this defaults to `1`.
    /// The bar label also uses this value as its width.
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn bar_width(mut self, width: u16) -> Self {
        self.bar_width = width;
        self
    }

    /// Set the gap between each bar.
    ///
    /// If not set, this defaults to `1`.
    /// The bar label will never be larger than the bar itself, even if the gap is sufficient.
    ///
    /// # Example
    ///
    /// This shows two bars with a gap of `3`. Notice the labels will always stay under the bar.
    /// ```
    /// # use ratatui::{prelude::*, widgets::*};
    /// BarChart::default()
    ///     .data(&[("foo", 1), ("bar", 2)])
    ///     .bar_gap(3);
    /// // Renders
    /// //     █
    /// // █   █
    /// // f   b
    /// ```
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn bar_gap(mut self, gap: u16) -> Self {
        self.bar_gap = gap;
        self
    }

    /// The [`bar::Set`](crate::symbols::bar::Set) to use for displaying the bars.
    ///
    /// If not set, the default is [`bar::NINE_LEVELS`](crate::symbols::bar::NINE_LEVELS).
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn bar_set(mut self, bar_set: symbols::bar::Set) -> Self {
        self.bar_set = bar_set;
        self
    }

    /// Set the default value style of the bar.
    ///
    /// `style` accepts any type that is convertible to [`Style`] (e.g. [`Style`], [`Color`], or
    /// your own type that implements [`Into<Style>`]).
    ///
    /// It is also possible to set individually the value style of each [`Bar`].
    /// In this case the default value style will be patched by the individual value style
    ///
    /// # See also
    ///
    /// [`Bar::value_style`] to set the value style individually.
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn value_style<S: Into<Style>>(mut self, style: S) -> Self {
        self.value_style = style.into();
        self
    }

    /// Set the default label style of the groups and bars.
    ///
    /// `style` accepts any type that is convertible to [`Style`] (e.g. [`Style`], [`Color`], or
    /// your own type that implements [`Into<Style>`]).
    ///
    /// It is also possible to set individually the label style of each [`Bar`] or [`BarGroup`].
    /// In this case the default label style will be patched by the individual label style
    ///
    /// # See also
    ///
    /// [`Bar::label`] to set the label style individually.
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn label_style<S: Into<Style>>(mut self, style: S) -> Self {
        self.label_style = style.into();
        self
    }

    /// Set the gap between [`BarGroup`].
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn group_gap(mut self, gap: u16) -> Self {
        self.group_gap = gap;
        self
    }

    /// Set the style of the entire chart.
    ///
    /// `style` accepts any type that is convertible to [`Style`] (e.g. [`Style`], [`Color`], or
    /// your own type that implements [`Into<Style>`]).
    ///
    /// The style will be applied to everything that isn't styled (borders, bars, labels, ...).
    #[must_use = "method moves the value of self and returns the modified value"]
    pub fn style<S: Into<Style>>(mut self, style: S) -> Self {
        self.style = style.into();
        self
    }

    /// Set the direction of the bars.
    ///
    /// [`Vertical`](crate::layout::Direction::Vertical) bars are the default.
    ///
    /// # Examples
    ///
    /// Vertical bars
    /// ```plain
    ///   █
    /// █ █
    /// f b
    /// ```
    ///
    /// Horizontal bars
    /// ```plain
    /// █foo██
    ///
    /// █bar██
    /// ```
    #[must_use = "method moves the value of self and returns the modified value"]
    pub const fn direction(mut self, direction: Direction) -> Self {
        self.direction = direction;
        self
    }
}

#[derive(Clone, Copy)]
struct LabelInfo {
    group_label_visible: bool,
    bar_label_visible: bool,
    height: u16,
}

impl BarChart<'_> {
    /// Returns the visible bars length in ticks. A cell contains 8 ticks.
    /// `available_space` used to calculate how many bars can fit in the space
    /// `bar_max_length` is the maximal length a bar can take.
    fn group_ticks(&self, available_space: u16, bar_max_length: u16) -> Vec<Vec<u64>> {
        let max: u64 = self.maximum_data_value();
        self.data
            .iter()
            .scan(available_space, |space, group| {
                if *space == 0 {
                    return None;
                }
                let n_bars = group.bars.len() as u16;
                let group_width = n_bars * self.bar_width + n_bars.saturating_sub(1) * self.bar_gap;

                let n_bars = if *space > group_width {
                    *space = space.saturating_sub(group_width + self.group_gap + self.bar_gap);
                    Some(n_bars)
                } else {
                    let max_bars = (*space + self.bar_gap) / (self.bar_width + self.bar_gap);
                    if max_bars > 0 {
                        *space = 0;
                        Some(max_bars)
                    } else {
                        None
                    }
                };

                n_bars.map(|n| {
                    group
                        .bars
                        .iter()
                        .take(n as usize)
                        .map(|bar| bar.value * u64::from(bar_max_length) * 8 / max)
                        .collect()
                })
            })
            .collect()
    }

    /// Get label information.
    ///
    /// height is the number of lines, which depends on whether we need to print the bar
    /// labels and/or the group labels.
    /// - If there are no labels, height is 0.
    /// - If there are only bar labels, height is 1.
    /// - If there are only group labels, height is 1.
    /// - If there are both bar and group labels, height is 2.
    fn label_info(&self, available_height: u16) -> LabelInfo {
        if available_height == 0 {
            return LabelInfo {
                group_label_visible: false,
                bar_label_visible: false,
                height: 0,
            };
        }

        let bar_label_visible = self
            .data
            .iter()
            .any(|e| e.bars.iter().any(|e| e.label.is_some()));

        if available_height == 1 && bar_label_visible {
            return LabelInfo {
                group_label_visible: false,
                bar_label_visible: true,
                height: 1,
            };
        }

        let group_label_visible = self.data.iter().any(|e| e.label.is_some());
        LabelInfo {
            group_label_visible,
            bar_label_visible,
            // convert true to 1 and false to 0 and add the two values
            height: u16::from(group_label_visible) + u16::from(bar_label_visible),
        }
    }

    fn render_horizontal(&self, buf: &mut Buffer, area: Rect) {
        // get the longest label
        let label_size = self
            .data
            .iter()
            .flat_map(|group| group.bars.iter().map(|bar| &bar.label))
            .flatten() // bar.label is an Option<Line>
            .map(Line::width)
            .max()
            .unwrap_or(0) as u16;

        let label_x = area.x;
        let bars_area = {
            let margin = u16::from(label_size != 0);
            Rect {
                x: area.x + label_size + margin,
                width: area.width - label_size - margin,
                ..area
            }
        };

        let group_ticks = self.group_ticks(bars_area.height, bars_area.width);

        // print all visible bars, label and values
        let mut bar_y = bars_area.top();
        for (ticks_vec, group) in group_ticks.into_iter().zip(self.data.iter()) {
            for (ticks, bar) in ticks_vec.into_iter().zip(group.bars.iter()) {
                let bar_length = (ticks / 8) as u16;
                let bar_style = self.bar_style.patch(bar.style);

                for y in 0..self.bar_width {
                    let bar_y = bar_y + y;
                    for x in 0..bars_area.width {
                        let symbol = if x < bar_length {
                            self.bar_set.full
                        } else {
                            self.bar_set.empty
                        };
                        buf.get_mut(bars_area.left() + x, bar_y)
                            .set_symbol(symbol)
                            .set_style(bar_style);
                    }
                }

                let bar_value_area = Rect {
                    y: bar_y + (self.bar_width >> 1),
                    ..bars_area
                };

                // label
                if let Some(label) = &bar.label {
                    buf.set_line(label_x, bar_value_area.top(), label, label_size);
                }

                bar.render_value_with_different_styles(
                    buf,
                    bar_value_area,
                    bar_length as usize,
                    self.value_style,
                    self.bar_style,
                );

                bar_y += self.bar_gap + self.bar_width;
            }

            // if group_gap is zero, then there is no place to print the group label
            // check also if the group label is still inside the visible area
            let label_y = bar_y - self.bar_gap;
            if self.group_gap > 0 && label_y < bars_area.bottom() {
                let label_rect = Rect {
                    y: label_y,
                    ..bars_area
                };
                group.render_label(buf, label_rect, self.label_style);
                bar_y += self.group_gap;
            }
        }
    }

    fn render_vertical(&self, buf: &mut Buffer, area: Rect) {
        let label_info = self.label_info(area.height - 1);

        let bars_area = Rect {
            height: area.height - label_info.height,
            ..area
        };

        let group_ticks = self.group_ticks(bars_area.width, bars_area.height);
        self.render_vertical_bars(bars_area, buf, &group_ticks);
        self.render_labels_and_values(area, buf, label_info, &group_ticks);
    }

    fn render_vertical_bars(&self, area: Rect, buf: &mut Buffer, group_ticks: &[Vec<u64>]) {
        // print all visible bars (without labels and values)
        let mut bar_x = area.left();
        for (ticks_vec, group) in group_ticks.iter().zip(&self.data) {
            for (ticks, bar) in ticks_vec.iter().zip(&group.bars) {
                let mut ticks = *ticks;
                for j in (0..area.height).rev() {
                    let symbol = match ticks {
                        0 => self.bar_set.empty,
                        1 => self.bar_set.one_eighth,
                        2 => self.bar_set.one_quarter,
                        3 => self.bar_set.three_eighths,
                        4 => self.bar_set.half,
                        5 => self.bar_set.five_eighths,
                        6 => self.bar_set.three_quarters,
                        7 => self.bar_set.seven_eighths,
                        _ => self.bar_set.full,
                    };

                    let bar_style = self.bar_style.patch(bar.style);

                    for x in 0..self.bar_width {
                        buf.get_mut(bar_x + x, area.top() + j)
                            .set_symbol(symbol)
                            .set_style(bar_style);
                    }

                    ticks = ticks.saturating_sub(8);
                }
                bar_x += self.bar_gap + self.bar_width;
            }
            bar_x += self.group_gap;
        }
    }

    /// get the maximum data value. the returned value is always greater equal 1
    fn maximum_data_value(&self) -> u64 {
        self.max
            .unwrap_or_else(|| {
                self.data
                    .iter()
                    .map(|group| group.max().unwrap_or_default())
                    .max()
                    .unwrap_or_default()
            })
            .max(1)
    }

    fn render_labels_and_values(
        &self,
        area: Rect,
        buf: &mut Buffer,
        label_info: LabelInfo,
        group_ticks: &[Vec<u64>],
    ) {
        // print labels and values in one go
        let mut bar_x = area.left();
        let bar_y = area.bottom() - label_info.height - 1;
        for (group, ticks_vec) in self.data.iter().zip(group_ticks) {
            if group.bars.is_empty() {
                continue;
            }
            // print group labels under the bars or the previous labels
            if label_info.group_label_visible {
                let label_max_width =
                    ticks_vec.len() as u16 * (self.bar_width + self.bar_gap) - self.bar_gap;
                let group_area = Rect {
                    x: bar_x,
                    y: area.bottom() - 1,
                    width: label_max_width,
                    height: 1,
                };
                group.render_label(buf, group_area, self.label_style);
            }

            // print the bar values and numbers
            for (bar, ticks) in group.bars.iter().zip(ticks_vec) {
                if label_info.bar_label_visible {
                    bar.render_label(buf, self.bar_width, bar_x, bar_y + 1, self.label_style);
                }

                bar.render_value(buf, self.bar_width, bar_x, bar_y, self.value_style, *ticks);

                bar_x += self.bar_gap + self.bar_width;
            }
            bar_x += self.group_gap;
        }
    }
}

impl Widget for BarChart<'_> {
    fn render(self, area: Rect, buf: &mut Buffer) {
        self.render_ref(area, buf);
    }
}

impl WidgetRef for BarChart<'_> {
    fn render_ref(&self, area: Rect, buf: &mut Buffer) {
        buf.set_style(area, self.style);

        self.block.render_ref(area, buf);
        let inner = self.block.inner_if_some(area);

        if inner.is_empty() || self.data.is_empty() || self.bar_width == 0 {
            return;
        }

        match self.direction {
            Direction::Horizontal => self.render_horizontal(buf, inner),
            Direction::Vertical => self.render_vertical(buf, inner),
        }
    }
}

impl<'a> Styled for BarChart<'a> {
    type Item = Self;
    fn style(&self) -> Style {
        self.style
    }

    fn set_style<S: Into<Style>>(self, style: S) -> Self::Item {
        self.style(style)
    }
}

#[cfg(test)]
mod tests {
    use itertools::iproduct;

    use super::*;
    use crate::{
        assert_buffer_eq,
        widgets::{BorderType, Borders},
    };

    #[test]
    fn default() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 10, 3));
        let widget = BarChart::default();
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(buffer, Buffer::with_lines(vec!["          "; 3]));
    }

    #[test]
    fn data() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default().data(&[("foo", 1), ("bar", 2)]);
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "  █            ",
                "1 2            ",
                "f b            ",
            ])
        );
    }

    #[test]
    fn block() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 5));
        let block = Block::default()
            .title("Block")
            .border_type(BorderType::Double)
            .borders(Borders::ALL);
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .block(block);
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "╔Block════════╗",
                "║  █          ║",
                "║1 2          ║",
                "║f b          ║",
                "╚═════════════╝",
            ])
        );
    }

    #[test]
    fn max() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let without_max = BarChart::default().data(&[("foo", 1), ("bar", 2), ("baz", 100)]);
        without_max.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "    █          ",
                "    █          ",
                "f b b          ",
            ])
        );
        let with_max = BarChart::default()
            .data(&[("foo", 1), ("bar", 2), ("baz", 100)])
            .max(2);
        with_max.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "  █ █          ",
                "1 2 █          ",
                "f b b          ",
            ])
        );
    }

    #[test]
    fn bar_style() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .bar_style(Style::new().red());
        widget.render(buffer.area, &mut buffer);
        let mut expected = Buffer::with_lines(vec![
            "  █            ",
            "1 2            ",
            "f b            ",
        ]);
        for (x, y) in iproduct!([0, 2], [0, 1]) {
            expected.get_mut(x, y).set_fg(Color::Red);
        }
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn bar_width() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .bar_width(3);
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "    ███        ",
                "█1█ █2█        ",
                "foo bar        ",
            ])
        );
    }

    #[test]
    fn bar_gap() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .bar_gap(2);
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "   █           ",
                "1  2           ",
                "f  b           ",
            ])
        );
    }

    #[test]
    fn bar_set() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 0), ("bar", 1), ("baz", 3)])
            .bar_set(symbols::bar::THREE_LEVELS);
        widget.render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "    █          ",
                "  ▄ 3          ",
                "f b b          ",
            ])
        );
    }

    #[test]
    fn bar_set_nine_levels() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 18, 3));
        let widget = BarChart::default()
            .data(&[
                ("a", 0),
                ("b", 1),
                ("c", 2),
                ("d", 3),
                ("e", 4),
                ("f", 5),
                ("g", 6),
                ("h", 7),
                ("i", 8),
            ])
            .bar_set(symbols::bar::NINE_LEVELS);
        widget.render(Rect::new(0, 1, 18, 2), &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "                  ",
                "  ▁ ▂ ▃ ▄ ▅ ▆ ▇ 8 ",
                "a b c d e f g h i ",
            ])
        );
    }

    #[test]
    fn value_style() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .bar_width(3)
            .value_style(Style::new().red());
        widget.render(buffer.area, &mut buffer);
        let mut expected = Buffer::with_lines(vec![
            "    ███        ",
            "█1█ █2█        ",
            "foo bar        ",
        ]);
        expected.get_mut(1, 1).set_fg(Color::Red);
        expected.get_mut(5, 1).set_fg(Color::Red);
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn label_style() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .label_style(Style::new().red());
        widget.render(buffer.area, &mut buffer);
        let mut expected = Buffer::with_lines(vec![
            "  █            ",
            "1 2            ",
            "f b            ",
        ]);
        expected.get_mut(0, 2).set_fg(Color::Red);
        expected.get_mut(2, 2).set_fg(Color::Red);
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn style() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        let widget = BarChart::default()
            .data(&[("foo", 1), ("bar", 2)])
            .style(Style::new().red());
        widget.render(buffer.area, &mut buffer);
        let mut expected = Buffer::with_lines(vec![
            "  █            ",
            "1 2            ",
            "f b            ",
        ]);
        for (x, y) in iproduct!(0..15, 0..3) {
            expected.get_mut(x, y).set_fg(Color::Red);
        }
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn can_be_stylized() {
        assert_eq!(
            BarChart::default().black().on_white().bold().style,
            Style::default()
                .fg(Color::Black)
                .bg(Color::White)
                .add_modifier(Modifier::BOLD)
        );
    }

    #[test]
    fn test_empty_group() {
        let chart = BarChart::default()
            .data(BarGroup::default().label("invisible".into()))
            .data(
                BarGroup::default()
                    .label("G".into())
                    .bars(&[Bar::default().value(1), Bar::default().value(2)]),
            );

        let mut buffer = Buffer::empty(Rect::new(0, 0, 3, 3));
        chart.render(buffer.area, &mut buffer);
        let expected = Buffer::with_lines(vec!["  █", "1 2", "G  "]);
        assert_buffer_eq!(buffer, expected);
    }

    fn build_test_barchart<'a>() -> BarChart<'a> {
        BarChart::default()
            .data(BarGroup::default().label("G1".into()).bars(&[
                Bar::default().value(2),
                Bar::default().value(3),
                Bar::default().value(4),
            ]))
            .data(BarGroup::default().label("G2".into()).bars(&[
                Bar::default().value(3),
                Bar::default().value(4),
                Bar::default().value(5),
            ]))
            .group_gap(1)
            .direction(Direction::Horizontal)
            .bar_gap(0)
    }

    #[test]
    fn test_horizontal_bars() {
        let chart: BarChart<'_> = build_test_barchart();

        let mut buffer = Buffer::empty(Rect::new(0, 0, 5, 8));
        chart.render(buffer.area, &mut buffer);
        let expected = Buffer::with_lines(vec![
            "2█   ",
            "3██  ",
            "4███ ",
            "G1   ",
            "3██  ",
            "4███ ",
            "5████",
            "G2   ",
        ]);

        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_horizontal_bars_no_space_for_group_label() {
        let chart: BarChart<'_> = build_test_barchart();

        let mut buffer = Buffer::empty(Rect::new(0, 0, 5, 7));
        chart.render(buffer.area, &mut buffer);
        let expected = Buffer::with_lines(vec![
            "2█   ",
            "3██  ",
            "4███ ",
            "G1   ",
            "3██  ",
            "4███ ",
            "5████",
        ]);

        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_horizontal_bars_no_space_for_all_bars() {
        let chart: BarChart<'_> = build_test_barchart();

        let mut buffer = Buffer::empty(Rect::new(0, 0, 5, 5));
        chart.render(buffer.area, &mut buffer);
        let expected = Buffer::with_lines(vec!["2█   ", "3██  ", "4███ ", "G1   ", "3██  "]);

        assert_buffer_eq!(buffer, expected);
    }

    fn test_horizontal_bars_label_width_greater_than_bar(bar_color: Option<Color>) {
        let mut bar = Bar::default()
            .value(2)
            .text_value("label".into())
            .value_style(Style::default().red());

        if let Some(color) = bar_color {
            bar = bar.style(Style::default().fg(color));
        }

        let chart: BarChart<'_> = BarChart::default()
            .data(BarGroup::default().bars(&[bar, Bar::default().value(5)]))
            .direction(Direction::Horizontal)
            .bar_style(Style::default().yellow())
            .value_style(Style::default().italic())
            .bar_gap(0);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 5, 2));
        chart.render(buffer.area, &mut buffer);

        let mut expected = Buffer::with_lines(vec!["label", "5████"]);

        // first line has a yellow foreground. first cell contains italic "5"
        expected.get_mut(0, 1).modifier.insert(Modifier::ITALIC);
        for x in 0..5 {
            expected.get_mut(x, 1).set_fg(Color::Yellow);
        }

        let expected_color = if let Some(color) = bar_color {
            color
        } else {
            Color::Yellow
        };

        // second line contains the word "label". Since the bar value is 2,
        // then the first 2 characters of "label" are italic red.
        // the rest is white (using the Bar's style).
        let cell = expected.get_mut(0, 0).set_fg(Color::Red);
        cell.modifier.insert(Modifier::ITALIC);
        let cell = expected.get_mut(1, 0).set_fg(Color::Red);
        cell.modifier.insert(Modifier::ITALIC);
        expected.get_mut(2, 0).set_fg(expected_color);
        expected.get_mut(3, 0).set_fg(expected_color);
        expected.get_mut(4, 0).set_fg(expected_color);

        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_horizontal_bars_label_width_greater_than_bar_without_style() {
        test_horizontal_bars_label_width_greater_than_bar(None);
    }

    #[test]
    fn test_horizontal_bars_label_width_greater_than_bar_with_style() {
        test_horizontal_bars_label_width_greater_than_bar(Some(Color::White));
    }

    /// Tests horizontal bars label are presents
    #[test]
    fn test_horizontal_label() {
        let chart = BarChart::default()
            .direction(Direction::Horizontal)
            .bar_gap(0)
            .data(&[("Jan", 10), ("Feb", 20), ("Mar", 5)]);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 10, 3));
        chart.render(buffer.area, &mut buffer);
        let expected = Buffer::with_lines(vec!["Jan 10█   ", "Feb 20████", "Mar 5     "]);

        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_group_label_style() {
        let chart: BarChart<'_> = BarChart::default()
            .data(
                BarGroup::default()
                    .label(Span::from("G1").red().into())
                    .bars(&[Bar::default().value(2)]),
            )
            .group_gap(1)
            .direction(Direction::Horizontal)
            .label_style(Style::default().bold().yellow());

        let mut buffer = Buffer::empty(Rect::new(0, 0, 5, 2));
        chart.render(buffer.area, &mut buffer);

        // G1 should have the bold red style
        // bold: because of BarChart::label_style
        // red: is included with the label itself
        let mut expected = Buffer::with_lines(vec!["2████", "G1   "]);
        let cell = expected.get_mut(0, 1).set_fg(Color::Red);
        cell.modifier.insert(Modifier::BOLD);
        let cell = expected.get_mut(1, 1).set_fg(Color::Red);
        cell.modifier.insert(Modifier::BOLD);

        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_group_label_center() {
        // test the centered group position when one bar is outside the group
        let group = BarGroup::from(&[("a", 1), ("b", 2), ("c", 3), ("c", 4)]);
        let chart = BarChart::default()
            .data(
                group
                    .clone()
                    .label(Line::from("G1").alignment(Alignment::Center)),
            )
            .data(group.label(Line::from("G2").alignment(Alignment::Center)));

        let mut buffer = Buffer::empty(Rect::new(0, 0, 13, 5));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "    ▂ █     ▂",
                "  ▄ █ █   ▄ █",
                "▆ 2 3 4 ▆ 2 3",
                "a b c c a b c",
                "  G1     G2  ",
            ])
        );
    }

    #[test]
    fn test_group_label_right() {
        let chart: BarChart<'_> = BarChart::default().data(
            BarGroup::default()
                .label(Line::from(Span::from("G")).alignment(Alignment::Right))
                .bars(&[Bar::default().value(2), Bar::default().value(5)]),
        );

        let mut buffer = Buffer::empty(Rect::new(0, 0, 3, 3));
        chart.render(buffer.area, &mut buffer);

        let expected = Buffer::with_lines(vec!["  █", "▆ 5", "  G"]);
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn test_unicode_as_value() {
        let group = BarGroup::default().bars(&[
            Bar::default()
                .value(123)
                .label("B1".into())
                .text_value("写".into()),
            Bar::default()
                .value(321)
                .label("B2".into())
                .text_value("写".into()),
            Bar::default()
                .value(333)
                .label("B2".into())
                .text_value("写".into()),
        ]);
        let chart = BarChart::default().data(group).bar_width(3).bar_gap(1);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 11, 5));
        chart.render(buffer.area, &mut buffer);

        let expected = Buffer::with_lines(vec![
            "    ▆▆▆ ███",
            "    ███ ███",
            "▃▃▃ ███ ███",
            "写█ 写█ 写█",
            "B1  B2  B2 ",
        ]);
        assert_buffer_eq!(buffer, expected);
    }

    #[test]
    fn handles_zero_width() {
        // this test is to ensure that a BarChart with zero bar / gap width does not panic
        let chart = BarChart::default()
            .data(&[("A", 1)])
            .bar_width(0)
            .bar_gap(0);
        let mut buffer = Buffer::empty(Rect::new(0, 0, 0, 10));
        chart.render(buffer.area, &mut buffer);
        assert_buffer_eq!(buffer, Buffer::empty(Rect::new(0, 0, 0, 10)));
    }

    #[test]
    fn single_line() {
        let mut group: BarGroup = (&[
            ("a", 0),
            ("b", 1),
            ("c", 2),
            ("d", 3),
            ("e", 4),
            ("f", 5),
            ("g", 6),
            ("h", 7),
            ("i", 8),
        ])
            .into();
        group = group.label("Group".into());

        let chart = BarChart::default()
            .data(group)
            .bar_set(symbols::bar::NINE_LEVELS);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 17, 1));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(buffer, Buffer::with_lines(vec!["  ▁ ▂ ▃ ▄ ▅ ▆ ▇ 8"]));
    }

    #[test]
    fn two_lines() {
        let mut group: BarGroup = (&[
            ("a", 0),
            ("b", 1),
            ("c", 2),
            ("d", 3),
            ("e", 4),
            ("f", 5),
            ("g", 6),
            ("h", 7),
            ("i", 8),
        ])
            .into();
        group = group.label("Group".into());

        let chart = BarChart::default()
            .data(group)
            .bar_set(symbols::bar::NINE_LEVELS);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 17, 3));
        chart.render(Rect::new(0, 1, buffer.area.width, 2), &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "                 ",
                "  ▁ ▂ ▃ ▄ ▅ ▆ ▇ 8",
                "a b c d e f g h i",
            ])
        );
    }

    #[test]
    fn three_lines() {
        let mut group: BarGroup = (&[
            ("a", 0),
            ("b", 1),
            ("c", 2),
            ("d", 3),
            ("e", 4),
            ("f", 5),
            ("g", 6),
            ("h", 7),
            ("i", 8),
        ])
            .into();
        group = group.label(Line::from("Group").alignment(Alignment::Center));

        let chart = BarChart::default()
            .data(group)
            .bar_set(symbols::bar::NINE_LEVELS);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 17, 3));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "  ▁ ▂ ▃ ▄ ▅ ▆ ▇ 8",
                "a b c d e f g h i",
                "      Group      ",
            ])
        );
    }

    #[test]
    fn three_lines_double_width() {
        let mut group = BarGroup::from(&[
            ("a", 0),
            ("b", 1),
            ("c", 2),
            ("d", 3),
            ("e", 4),
            ("f", 5),
            ("g", 6),
            ("h", 7),
            ("i", 8),
        ]);
        group = group.label(Line::from("Group").alignment(Alignment::Center));

        let chart = BarChart::default()
            .data(group)
            .bar_width(2)
            .bar_set(symbols::bar::NINE_LEVELS);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 26, 3));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "   1▁ 2▂ 3▃ 4▄ 5▅ 6▆ 7▇ 8█",
                "a  b  c  d  e  f  g  h  i ",
                "          Group           ",
            ])
        );
    }

    #[test]
    fn four_lines() {
        let mut group: BarGroup = (&[
            ("a", 0),
            ("b", 1),
            ("c", 2),
            ("d", 3),
            ("e", 4),
            ("f", 5),
            ("g", 6),
            ("h", 7),
            ("i", 8),
        ])
            .into();
        group = group.label(Line::from("Group").alignment(Alignment::Center));

        let chart = BarChart::default()
            .data(group)
            .bar_set(symbols::bar::NINE_LEVELS);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 17, 4));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "          ▂ ▄ ▆ █",
                "  ▂ ▄ ▆ 4 5 6 7 8",
                "a b c d e f g h i",
                "      Group      ",
            ])
        );
    }

    #[test]
    fn two_lines_without_bar_labels() {
        let group = BarGroup::default()
            .label(Line::from("Group").alignment(Alignment::Center))
            .bars(&[
                Bar::default().value(0),
                Bar::default().value(1),
                Bar::default().value(2),
                Bar::default().value(3),
                Bar::default().value(4),
                Bar::default().value(5),
                Bar::default().value(6),
                Bar::default().value(7),
                Bar::default().value(8),
            ]);

        let chart = BarChart::default().data(group);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 17, 3));
        chart.render(Rect::new(0, 1, buffer.area.width, 2), &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "                 ",
                "  ▁ ▂ ▃ ▄ ▅ ▆ ▇ 8",
                "      Group      ",
            ])
        );
    }

    #[test]
    fn one_lines_with_more_bars() {
        let bars: Vec<Bar> = (0..30).map(|i| Bar::default().value(i)).collect();

        let chart = BarChart::default().data(BarGroup::default().bars(&bars));

        let mut buffer = Buffer::empty(Rect::new(0, 0, 59, 1));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "        ▁ ▁ ▁ ▁ ▂ ▂ ▂ ▃ ▃ ▃ ▃ ▄ ▄ ▄ ▄ ▅ ▅ ▅ ▆ ▆ ▆ ▆ ▇ ▇ ▇ █",
            ])
        );
    }

    #[test]
    fn first_bar_of_the_group_is_half_outside_view() {
        let chart = BarChart::default()
            .data(&[("a", 1), ("b", 2)])
            .data(&[("a", 1), ("b", 2)])
            .bar_width(2);

        let mut buffer = Buffer::empty(Rect::new(0, 0, 7, 6));
        chart.render(buffer.area, &mut buffer);

        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "   ██  ",
                "   ██  ",
                "▄▄ ██  ",
                "██ ██  ",
                "1█ 2█  ",
                "a  b   ",
            ])
        );
    }
}