use std::cmp::{max, min};

use unicode_width::UnicodeWidthStr;

use buffer::Buffer;
use layout::Rect;
use style::Style;
use symbols::bar;
use widgets::{Block, Widget};

/// Display multiple bars in a single widgets
///
/// # Examples
///
/// ```
/// # extern crate tui;
/// # use tui::widgets::{Block, Borders, BarChart};
/// # use tui::style::{Style, Color, Modifier};
/// # fn main() {
/// BarChart::default()
///     .block(Block::default().title("BarChart").borders(Borders::ALL))
///     .bar_width(3)
///     .bar_gap(1)
///     .style(Style::default().fg(Color::Yellow).bg(Color::Red))
///     .value_style(Style::default().fg(Color::Red).modifier(Modifier::Bold))
///     .label_style(Style::default().fg(Color::White))
///     .data(&[("B0", 0), ("B1", 2), ("B2", 4), ("B3", 3)])
///     .max(4);
/// # }
/// ```
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,
    /// 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,
    /// Slice of (label, value) pair to plot on the chart
    data: &'a [(&'a str, u64)],
    /// 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>,
    /// Values to display on the bar (computed when the data is passed to the widget)
    values: Vec<String>,
}

impl<'a> Default for BarChart<'a> {
    fn default() -> BarChart<'a> {
        BarChart {
            block: None,
            max: None,
            data: &[],
            values: Vec::new(),
            bar_width: 1,
            bar_gap: 1,
            value_style: Default::default(),
            label_style: Default::default(),
            style: Default::default(),
        }
    }
}

impl<'a> BarChart<'a> {
    pub fn data(&'a mut self, data: &'a [(&'a str, u64)]) -> &mut BarChart<'a> {
        self.data = data;
        self.values = Vec::with_capacity(self.data.len());
        for &(_, v) in self.data {
            self.values.push(format!("{}", v));
        }
        self
    }

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

    pub fn bar_width(&'a mut self, width: u16) -> &mut BarChart<'a> {
        self.bar_width = width;
        self
    }
    pub fn bar_gap(&'a mut self, gap: u16) -> &mut BarChart<'a> {
        self.bar_gap = gap;
        self
    }
    pub fn value_style(&'a mut self, style: Style) -> &mut BarChart<'a> {
        self.value_style = style;
        self
    }
    pub fn label_style(&'a mut self, style: Style) -> &mut BarChart<'a> {
        self.label_style = style;
        self
    }
    pub fn style(&'a mut self, style: Style) -> &mut BarChart<'a> {
        self.style = style;
        self
    }
}

impl<'a> Widget for BarChart<'a> {
    fn draw(&mut self, area: Rect, buf: &mut Buffer) {
        let chart_area = match self.block {
            Some(ref mut b) => {
                b.draw(area, buf);
                b.inner(area)
            }
            None => area,
        };

        if chart_area.height < 2 {
            return;
        }

        self.background(&chart_area, buf, self.style.bg);

        let max = self
            .max
            .unwrap_or_else(|| self.data.iter().fold(0, |acc, &(_, v)| max(v, acc)));
        let max_index = min(
            (chart_area.width / (self.bar_width + self.bar_gap)) as usize,
            self.data.len(),
        );
        let mut data = self
            .data
            .iter()
            .take(max_index)
            .map(|&(l, v)| (l, v * u64::from(chart_area.height) * 8 / max))
            .collect::<Vec<(&str, u64)>>();
        for j in (0..chart_area.height - 1).rev() {
            for (i, d) in data.iter_mut().enumerate() {
                let symbol = match d.1 {
                    0 => " ",
                    1 => bar::ONE_EIGHTH,
                    2 => bar::ONE_QUATER,
                    3 => bar::THREE_EIGHTHS,
                    4 => bar::HALF,
                    5 => bar::FIVE_EIGHTHS,
                    6 => bar::THREE_QUATERS,
                    7 => bar::SEVEN_EIGHTHS,
                    _ => bar::FULL,
                };

                for x in 0..self.bar_width {
                    buf.get_mut(
                        chart_area.left() + i as u16 * (self.bar_width + self.bar_gap) + x,
                        chart_area.top() + j,
                    ).set_symbol(symbol)
                        .set_style(self.style);
                }

                if d.1 > 8 {
                    d.1 -= 8;
                } else {
                    d.1 = 0;
                }
            }
        }

        for (i, &(label, value)) in self.data.iter().take(max_index).enumerate() {
            if value != 0 {
                let value_label = &self.values[i];
                let width = value_label.width() as u16;
                if width < self.bar_width {
                    buf.set_string(
                        chart_area.left()
                            + i as u16 * (self.bar_width + self.bar_gap)
                            + (self.bar_width - width) / 2,
                        chart_area.bottom() - 2,
                        value_label,
                        &self.value_style,
                    );
                }
            }
            buf.set_stringn(
                chart_area.left() + i as u16 * (self.bar_width + self.bar_gap),
                chart_area.bottom() - 1,
                label,
                self.bar_width as usize,
                &self.label_style,
            );
        }
    }
}