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use std::cmp::min;
use tui::{
    buffer::Buffer,
    layout::Rect,
    style::Style,
    symbols,
    widgets::{Block, Widget},
};

/// Widget to render a sparkline over one or more lines.
///
/// # Examples
///
/// ```
/// # use tui::widgets::{Block, Borders, Sparkline};
/// # use tui::style::{Style, Color};
/// Sparkline::default()
///     .block(Block::default().title("Sparkline").borders(Borders::ALL))
///     .data(&[0, 2, 3, 4, 1, 4, 10])
///     .max(5)
///     .style(Style::default().fg(Color::Red).bg(Color::White));
/// ```
#[derive(Debug, Clone)]
pub struct Sparkline<'a> {
    /// A block to wrap the widget in
    block: Option<Block<'a>>,
    /// Widget style
    style: Style,
    /// A slice of the data to display
    data: &'a [u64],
    /// The maximum value to take to compute the maximum bar height (if nothing is specified, the
    /// widget uses the max of the dataset)
    max: Option<u64>,
    /// A set of bar symbols used to represent the give data
    bar_set: symbols::bar::Set,
    /// Up side down
    reversed: bool,
}

impl<'a> Default for Sparkline<'a> {
    fn default() -> Sparkline<'a> {
        Sparkline {
            block: None,
            style: Default::default(),
            data: &[],
            max: None,
            bar_set: symbols::bar::NINE_LEVELS,
            reversed: false,
        }
    }
}

impl<'a> Sparkline<'a> {
    pub fn block(mut self, block: Block<'a>) -> Sparkline<'a> {
        self.block = Some(block);
        self
    }

    pub fn style(mut self, style: Style) -> Sparkline<'a> {
        self.style = style;
        self
    }

    pub fn data(mut self, data: &'a [u64]) -> Sparkline<'a> {
        self.data = data;
        self
    }

    pub fn max(mut self, max: u64) -> Sparkline<'a> {
        self.max = Some(max);
        self
    }

    pub fn bar_set(mut self, bar_set: symbols::bar::Set) -> Sparkline<'a> {
        self.bar_set = bar_set;
        self
    }

    pub fn reversed(mut self, reversed: bool) -> Sparkline<'a> {
        self.reversed = reversed;
        self
    }
}

impl<'a> Widget for Sparkline<'a> {
    fn render(mut self, area: Rect, buf: &mut Buffer) {
        let spark_area = match self.block.take() {
            Some(b) => {
                let inner_area = b.inner(area);
                b.render(area, buf);
                inner_area
            }
            None => area,
        };

        if spark_area.height < 1 {
            return;
        }

        let max = match self.max {
            Some(v) => v,
            None => *self.data.iter().max().unwrap_or(&1u64),
        };
        let max_index = min(spark_area.width as usize, self.data.len());
        let mut data = self
            .data
            .iter()
            .take(max_index)
            .map(|e| {
                if max != 0 {
                    e * u64::from(spark_area.height) * 8 / max
                } else {
                    0
                }
            })
            .collect::<Vec<u64>>();
        for j in (0..spark_area.height).rev() {
            for (i, d) in data.iter_mut().enumerate() {
                let (symbol, x, y) = if self.reversed {
                    (
                        match *d {
                            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,
                        },
                        spark_area.x + i as u16,
                        spark_area.y + spark_area.height - j - 1,
                    )
                } else {
                    (
                        match *d {
                            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,
                        },
                        spark_area.x + i as u16,
                        spark_area.y + j,
                    )
                };
                buf.get_mut(x, y).set_symbol(symbol).set_style(self.style);

                if *d > 8 {
                    *d -= 8;
                } else {
                    *d = 0;
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_does_not_panic_if_max_is_zero() {
        let widget = Sparkline::default().data(&[0, 0, 0]);
        let area = Rect::new(0, 0, 3, 1);
        let mut buffer = Buffer::empty(area);
        widget.render(area, &mut buffer);
    }

    #[test]
    fn it_does_not_panic_if_max_is_set_to_zero() {
        let widget = Sparkline::default().data(&[0, 1, 2]).max(0);
        let area = Rect::new(0, 0, 3, 1);
        let mut buffer = Buffer::empty(area);
        widget.render(area, &mut buffer);
    }
}